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Global structural analyses in civil engineering are usually performed considering linear-elastic material behavior. However, for steel structures, a certain degree of plasticization depending on the member classification may be considered. Corresponding plastic analyses taking material nonlinearities into account are effectively realized using numerical methods. Frequently applied finite elements of two and three-dimensional models evaluate the plasticity at defined nodes using a yield surface, i.e. by a yield condition, hardening rule, and flow rule. Corresponding calculations are connected to a large numerical as well as time-consuming effort and they do not rely on the theoretical background of beam theory, to which the regulations of standards mainly correspond. For that reason, methods using beam elements (one-dimensional) combined with cross-sectional analyses are commonly applied for steel members in terms of plastic zones theories. In these approaches, plasticization is in general assessed by means of axial stress only. In this paper, more precise numerical representation of the combined stress states, i.e. axial and shear stresses, is presented and results of the proposed approach are validated and discussed.
The aim of my research is to observe the variance of energy efficiency of a typical multi-story office building under the exposure of different climatic conditions. Energy efficiency requirements in building codes or energy standards are among the most important single measures for buildings’ energy efficiency. Therefore, this study can be set up for a better understanding of how energy efficiency of a building changes under the effect of adverse to moderate climatic conditions which possess a mentionable effect on the operation of a building.
This thesis is structured in three balanced and conceptual steps. Following the aim of the project, the virtual building model is to be analyzed under the effect of seven distinct climatic conditions namely work environment of New Delhi, Mumbai, Berlin, Lisbon, Copenhagen, Dubai and Montreal. Firstly, the task is to do a complete literature research based on the scope of similar researches and studying the problems in detail along with the theoritical background all the concepts which are implemented to get the numerical results. This chapter also comprises a detailed study of the climatic conditions of the above-mentioned cities. Different climatic traits like temperature variations, count of heating and cooling degree days, relative humidity, temperature range and comfort zonal charts for the specified cities are studied in detail. This study helps to understand the effect of these adverse to moderate climates on the operation of the building. On the second step, the virtual building model is prepared on a software platform named Revit Structures. This virtual building model is not necessarily a complete building, but it has the relevant functionalities of a real building. We perform the energy analysis and the heating and cooling analysis on this virtual building model to study the operational outcome of the building under different climatic conditions in detail. By the end of these above two tasks, two scenarios are observed. On one hand, we have a literature research and on the other hand we have the numerical results. Therefore, finally we present a comparative scenario based on the energy efficient performances of the building under such variant climatic conditions. This is followed by the prediction of thermal comfort level inside the building and it based on Fanger’s PMV Model. Understanding the literature and the numerical values in detail helps us to predict the index thermal comfort level inside the building.
The conclusion of this master thesis focuses mainly on the scopes of improvement of energy efficiency requirements in energy codes if any, differentiated according to specific locations. The initial aim of my hypothesis which is to study the impacts of climatic variations on the energy efficient performances of a building is fulfilled but as such topics have very deep and broad roots, the scope of further improvements is always predominant.
The building sector is responsible for a large share of human environmental impacts. Architects and planners are the key players for reducing the environmental impacts of buildings, as they define them to a large extent. Life Cycle Assessment (LCA) allows for the holistic environmental analysis of a building. However, it is currently not employed to improve the environmental performance of buildings during the design process, although the potential for optimization is greatest there. One main reason is the lack of an adequate means of applying LCA in the architectural design process. As such, the main objective of this thesis is to develop a method for environmental building design optimization that is applicable in the design process. The key concept proposed in this thesis is to combine LCA with parametric design, because it proved to have a high potential for design optimization.
The research approach includes the analysis of the characteristics of LCA for buildings and the architectural design stages to identify the research gap, the establishment of a requirement catalogue, the development of a method based on a digital, parametric model, and an evaluation of the method.
An analysis of currently available approaches for LCA of buildings indicates that they are either holistic but very complex or simple but not holistic. Furthermore, none of them provide the opportunity for optimization in the architectural design process, which is the main research gap. The requirements derived from the analysis have been summarized in the form of a catalogue. This catalogue can be used to evaluate both existing approaches and potential methods developed in the future. In this thesis, it served as guideline for the development of the parametric method – Parametric Life Cycle Assessment (PLCA). The unique main feature of PLCA is that embodied and operational environmental impact are calculated together. In combination with the self-contained workflow of the method, this provides the basis for holistic, time-efficient environmental design optimization. The application of PLCA to three examples indicated that all established mandatory requirements are met. In all cases, environmental impact could be significantly reduced. In comparison to conventional approaches, PLCA was shown to be much more time-efficient.
PLCA allows architects to focus on their main task of designing the building, and finally makes LCA practically useful as one of several criteria for design optimization. With PLCA, the building design can be time-efficiently optimized from the beginning of the most influential early design stages, which has not been possible until now. PLCA provides a good starting point for further research. In the future, it could be extended by integrating the social and economic aspects of sustainability.
A parametric method for building design optimization based on Life Cycle Assessment - Appendix
(2016)
The building sector is responsible for a large share of human environmental impacts, over which architects and planners have a major influence. The main objective of this thesis is to develop a method for environmental building design optimization based on Life Cycle Assessment (LCA) that is applicable as part of the design process. The research approach includes a thorough analysis of LCA for buildings in relation to the architectural design stages and the establishment of a requirement catalogue. The key concept of the novel method called Parametric Life Cycle Assessment(PLCA) is to combine LCA with parametric design. The application of this method to three examples shows that building designs can be optimized time-efficiently and holistically from the beginning of the most influential early design stages, an achievement which has not been possible until now.
In many engineering applications two or more different interacting systems require the numer-ical solution of so-called multifield problems. In civil engineering the interaction of fluid and structures plays an important role, i.e. for fabric tensile structures of light and flexible materials often used for large roof systems, capacious umbrellas or canopies. Whereas powerful numerical simulation techniques have been established in structural engineering as well as in fluid mechan-ics, only relatively few approaches to simulate the interaction of fluids with civil engineering constructions have been presented. To determine the wind loads on complex structures, it is still state-of-the-art to apply semi-empirical, strongly simplifying methods or to perform expensive ex-periments in wind tunnels. In this paper an approach of a coupled fluid-structure simulation will be presented for membrane and thin shell structures. The interaction is described by the struc-tural deformation as response to wind forces, resulting in a modification of the fluid flow domain. Besides a realistic determination of the wind loads, information on the structural stability can be obtained. The so-called partitioned solution is based on an iterative frame algorithm, integrating different codes for Computational Fluid Dynamics (CFD) and for Computational Structural Dy-namics (CSD) in an explicit or an implicit time-stepping procedure. All data exchange between the two different applications is performed via a neutral geometric model provided by a coupling interface. A conservative interpolation method is used for the interpolation of the nodal loads. The time-dependent motion of the structure requires a dynamic modification of the different grids and a redefinition of the Navier-Stokes equations in an Arbitrary Langrangian Eulerian (ALE) formulation. As an example for the present implementation, results of a coupled fluid-structure simulation for a textile membrane canopy will be presented.
The contribution introduces a method for the distributed process modelling in order to support the process orientation in Structural Engineering, i.e., the modelling, analysis and management of planning processes. The approach is based on the Petri Net theory for the modelling of planning processes and workflows in Structural Engineering. Firstly, a central and coarse process model serves as a pre-structuring system for the detailed modelling of the technical planning activities. Secondly, the involved planning participants generate distributed process models with detailed technical workflow information. Finally, these distributed process models will be combined in the central workflow net. The final net is of great importance for the process orientation in Structural Engineering, i.e., the identification, publication, analysis, optimization and finally the management of planning processes.
This paper presents a novel numerical procedure based on the combination of an edge-based smoothed finite element (ES-FEM) with a phantom-node method for 2D linear elastic fracture mechanics. In the standard phantom-node method, the cracks are formulated by adding phantom nodes, and the cracked element is replaced by two new superimposed elements. This approach is quite simple to implement into existing explicit finite element programs. The shape functions associated with discontinuous elements are similar to those of the standard finite elements, which leads to certain simplification with implementing in the existing codes. The phantom-node method allows modeling discontinuities at an arbitrary location in the mesh. The ES-FEM model owns a close-to-exact stiffness that is much softer than lower-order finite element methods (FEM). Taking advantage of both the ES-FEM and the phantom-node method, we introduce an edge-based strain smoothing technique for the phantom-node method. Numerical results show that the proposed method achieves high accuracy compared with the extended finite element method (XFEM) and other reference solutions.
Increasing complexity of today's buildings requires a high level of integration in the planning process. Common planning strategies, where individual project partners cooperate mainly to exchange results, are not suitable to jointly develop project goals and objectives. Integrated planning, a more holistic approach to deal with complex problems, is based on a high degree of communication amoung team members and leads to a goal oriented cooperation. Current approaches in the reasearch area of Computer Supported Cooperative Work (CSCW) poorly meet the requirements in planning. A planning process model, based on the principles of integrated planning will be introduced, aimed to provide the background for the implementation of a CSCW-platform.
The capitalization of ‘certified’ sustainable building sector will be investigated over the power theory of value approach of Jonathan Nitzan and Shimshon Bichler. The study will be initiated by questioning why the environment problems are one of the first items on the agenda and by sharing the ideas of scholars who approaches the subject skeptically, because the predominant literature underlying the necessity and prominence of the topic is already well-known and adapted by the majority. Over the theory developed by Nitzan and Bichler, the concepts of capitalization, strategic sabotage, power, legitimacy, and obedience will be discussed. The hypothesis of “the absentee owners of the construction sector, holding the whip hand and capitalizing the ecology, control the growth and the creativity of green building production and make it carbon-dependent, in order to increase their profit margin” will be questioned. To strengthen the arguments in the hypothesis, the factors, the institutional arrangements, value measurement methods, which affect directly the net present value, will be investigated both in corporation and in building scale in detail, because net present value/ capitalization is asserted as the most important criteria by Nitzan and Bichler to make the investment decisions in the capitalist economic system. To trace the implications of power and the strategic sabotage that power caused, as the empirical dimension of this dissertation, an interface exploring the correlational ties between the climate responsive architecture and the ever changing political, economical, and social contexts and building economics praxis by decades will be developed and the expert interviews will be conducted with the design teams and the appraisers.
The displacements and stresses in arch dams and their abutments are frequently determined with 20-node brick elements. The elements are distorted near the contact plane between the wall and the abutment. A cantilever beam testbed has been developed to investigate the consequences of this distortion. It is shown that the deterioration of the accuracy in the computed stresses is significant. A compatible 18-node wedge element with linear stress variation is developed as an alternative to the brick element. The shape of this element type is readily adapted to the shape of the contact plane. It is shown that the accuracy of the computed stresses in the vicinity of the contact plane is improved significantly by the use of wedge elements.
In recent years, the discussion of digitalization has arrived in the media, at conferences, and in committees of the construction and real estate industry. While some areas are producing innovations and some contributors can be described as pioneers, other topics still show deficits with regard to digital transformation. The building permit process can also be counted in this category. Regardless of how architects and engineers in planning offices rely on innovative methods, building documents have so far remained in paper form in too many cases, or are printed out after electronic submission to the authority. Existing resources – for example in the form of a building information model, which could provide support in the building permit process – are not being taken advantage of. In order to use digital tools to support decision-making by the building permit authorities, it is necessary to understand the current situation and to question conditions before pursuing the overall automation of internal authority processes as the sole solution.
With a substantive-organizational consideration of the relevant areas that influence building permit determination, an improvement of the building permit procedure within authorities is proposed. Complex areas – such as legal situations, the use of technology, as well as the subjective alternative action – are determined and structured. With the development of a model for the determination of building permitability, both an understanding of influencing factors is conveyed and an increase in transparency for all parties involved is created.
In addition to an international literature review, an empirical study served as the research method. The empirical study was conducted in the form of qualitative expert interviews in order to determine the current state in the field of building permit procedures. The collected data material was processed and subsequently subjected to a software-supported content analysis. The results were processed, in combination with findings from the literature review, in various analyses to form the basis for a proposed model.
The result of the study is a decision model that closes the gap between the current processes within the building authorities and an overall automation of the building permit review process. The model offers support to examiners and applicants in determining building permit eligibility, through its process-oriented structuring of decision-relevant facts. The theoretical model could be transferred into practice in the form of a web application.
We present a software prototype for fluid flow problems in civil engineering, which combines essential features of Computational Steering approaches with efficient methods for model transfer and high performance computing. The main components of the system are described: - The modeler with a focus on the data management of the product model - The pre-processing and the post-processing toolkit - The simulation kernel based on the Lattice Boltzmann method - The required hardware for real-time computing
A Product Model of a Road
(1997)
Many errors and delays frequently appear when data is exchanged between particular tasks in the lifecycle of the road. Inter-task connections are therefore of great importance for the quality of the final product. The article describes a product model of a road wich is the kernel of an integrated information system intended to support all important stages of the road lifecycle: design, evaluation (through different analysis procedures), construction, and maintainance. Since particular tasks are often executed at different places and in different companies, the interconnections are supported by a special metafile which contains all specific data of the product model. The concept of the integrated system is object and component oriented. Additionally, existing conventional program packages are included to support some common tasks (methods). A conventional relational database system as well as an open spatial database system with the relevant GIS functionality are included to support the data structures of the model.
In recent years, the survey is performed for repair, such as a bridge and a building built in past, spending great expense. And it is anxious for the survey technique that doesn’t need cost and time more. Then, we made an idea of the technique of precise 3D model creation by 2D pictures. However, the technique of performing the improvement in accuracy of convergent photographing and automatic acquisition of corresponding points was not established. Therefore, in this research, we try to obtain a semi-automation of corresponding points acquisition from initial corresponding points and the improvement in accuracy of convergent photographing. Moreover, we applied the research to the used house of Japanese real estate, and the applicable field was selected as the high needs of the residence of 3D model. And we developed the system that everyone could create Web / 3D model house by VRML easily without requiring expensive apparatuses or expertise.
The goal of architecture is changing in response to the expanding role of cities, rapid urbanization, and transformation under changing economic, environmental, social, and demographic factors. As cities increased in the early modern era, overcrowding, urbanization, and pollution conditions led reformers to consider the future shape of the cities. One of the most critical topics in contemporary architecture is the subject of the future concepts of living. In most cases, domed cities, as a future concept of living, are rarely considered, and they are used chiefly as “utopian” visions in the discourse of future ways of living. This paper highlights the reviews of domed cities to deepen the understanding of the idea in practice, like its approach in terms of architecture. The main aim of this paper is to provide a broad overview for domed cities in the face of pollution as one of the main concerns in many European cities. As a result, the significance of the reviews of the existing projects is focused on their conceptual quality. This review will pave the way for further studies in terms of future developments in the realm of domed cities. In this paper, the city of Celje, one of the most polluted cities in Slovenia, is taken as a case study for considering the concept of Dome incorporated due to the lack of accessible literature on the topic. This review’s primary contribution is to allow architects to explore a broad spectrum of innovation by comparing today’s achievable statuses against the possibilities generated by domed cities. As a result of this study, the concept of living under the Dome remains to be developed in theory and practice. The current challenging climatic situation will accelerate the evolution of these concepts, resulting in the formation of new typologies, which are a requirement for humanity.
Electric trains are considered one of the most eco-friendly and safest means of transportation. Catenary poles are used worldwide to support overhead power lines for electric trains. The performance of the catenary poles has an extensive influence on the integrity of the train systems and, consequently, the connected human services. It became a must nowadays to develop SHM systems that provide the instantaneous status of catenary poles in- service, making the decision-making processes to keep or repair the damaged poles more feasible. This study develops a data-driven, model-free approach for status monitoring of cantilever structures, focusing on pre-stressed, spun-cast ultrahigh-strength concrete catenary poles installed along high-speed train tracks. The pro-posed approach evaluates multiple damage features in an unfied damage index, which leads to straightforward interpretation and comparison of the output. Besides, it distinguishes between multiple damage scenarios of the poles, either the ones caused by material degradation of the concrete or by the cracks that can be propagated during the life span of the given structure. Moreover, using a logistic function to classify the integrity of structure avoids the expensive learning step in the existing damage detection approaches, namely, using the modern machine and deep learning methods. The findings of this study look very promising when applied to other types of cantilever structures, such as the poles that support the power transmission lines, antenna masts, chimneys, and wind turbines.
Information technology plays a key role in the everyday operation of buildings and campuses. Many proprietary technologies and methodologies can assist in effective Building Performance Monitoring (BPM) and efficient managing of building resources. The integration of related tools like energy simulator packages, facility, energy and building management systems, and enterprise resource planning systems is of benefit to BPM. However, the complexity to integrating such domain specific systems prevents their common usage. Service Oriented Architecture (SOA) has been deployed successfully in many large multinational companies to create integrated and flexible software systems, but so far this methodology has not been applied broadly to the field of BPM. This paper envisions that SOA provides an effective integration framework for BPM. Service oriented architecture for the ITOBO framework for sustainable and optimised building operation is proposed and an implementation for a building performance monitoring system is introduced.
A simple multiscale analysis framework for heterogeneous solids based on a computational homogenization technique is presented. The macroscopic strain is linked kinematically to the boundary displacement of a circular or spherical representative volume which contains the microscopic information of the material. The macroscopic stress is obtained from the energy principle between the macroscopic scale and the microscopic scale. This new method is applied to several standard examples to show its accuracy and consistency of the method proposed.
A simple multiscale analysis framework for heterogeneous solids based on a computational homogenization technique is presented. The macroscopic strain is linked kinematically to the boundary displacement of a circular or spherical representative volume which contains the microscopic information of the material. The macroscopic stress is obtained from the energy principle between the macroscopic scale and the microscopic scale. This new method is applied to several standard examples to show its accuracy and consistency of the method proposed.
To fulfil safety requirements the changes in the static and/or dynamic behaviour of the structure must be analysed with great care. These changes are often caused by local reduction of the stiffness of the structure caused by the irregularities in the structure, as for example cracks. In simple structures such analysis can be performed directly, by solving equations of motion, but for more complex structures a different approach, usually numerical, must be applied. The problem of crack implementation into the structure behaviour has been studied by many authors who have usually modelled the crack as a massless rotational spring of suitable stiffness placed at the beam at the location where the crack occurs. Recently, the numerical procedure for the computation of the stiffness matrix for a beam element with a single transverse crack has been replaced with the element stiffness matrix written in fully symbolic form. A detailed comparison of the results obtained by using 200 2D finite elements with those obtained with a single cracked beam element has confirmed the usefulness of such element.
As computer programs become ever more complex, software development has shifted from focusing on programming towards focusing on integration. This paper describes a simulation access language (SimAL) that can be used to access and compose software applications over the Internet. Specifically, the framework is developed for the integration of tools for project management applications. The infrastructure allows users to specify and to use existing heterogeneous tools (e.g., Microsoft Project, Microsoft Excel, Primavera Project Planner, and AutoCAD) for simulation of project scenarios. This paper describes the components of the SimAL language and the implementation efforts required in the development of the SimAL framework. An illustration example bringing on-line weather forecasting service for project scheduling and management applications is provided to demonstrate the use of the simulation language and the infrastructure framework.
A four-node quadrilateral shell element with smoothed membrane-bending based on Mindlin-Reissner theory is proposed. The element is a combination of a plate bending and membrane element. It is based on mixed interpolation where the bending and membrane stiffness matrices are calculated on the boundaries of the smoothing cells while the shear terms are approximated by independent interpolation functions in natural coordinates. The proposed element is robust, computationally inexpensive and free of locking. Since the integration is done on the element boundaries for the bending and membrane terms, the element is more accurate than the MITC4 element for distorted meshes. This will be demonstrated for several numerical examples.
This paper presents a new design environment based on Multi-Agents and Virtual Reality (VR). In this research, a design system with a virtual reality function was developed. The virtual world was realized by using GL4Java, liquid crystal shutter glasses, sensor systems, etc. And the Multi-Agent CAD system with product models, which had been developed before, was integrated with the VR design system. A prototype system was developed for highway steel plate girder bridges, and was applied to a design problem. The application verified the effectiveness of the developed system.
The distinguishing structural feature of single-layered black phosphorus is its puckered structure, which leads to many novel physical properties. In this work, we first present a new parameterization of the Stillinger–Weber potential for single-layered black phosphorus. In doing so, we reveal the importance of a cross-pucker interaction term in capturing its unique mechanical properties, such as a negative Poisson's ratio. In particular, we show that the cross-pucker interaction enables the pucker to act as a re-entrant hinge, which expands in the lateral direction when it is stretched in the longitudinal direction. As a consequence, single-layered black phosphorus has a negative Poisson's ratio in the direction perpendicular to the atomic plane. As an additional demonstration of the impact of the cross-pucker interaction, we show that it is also the key factor that enables capturing the edge stress-induced bending of single-layered black phosphorus that has been reported in ab initio calculations.
Superplasticizers are utilized both to improve the fluidity during the placement and to reduce the water content of concretes. Both effects have also an impact on the properties of the hardened concrete. As a side effect the presence of superplasticizers affects the strength development of concretes that is strongly retarded. This may lead to an ecomomical drawback of the concrete manufacturing. The present work is aimed at gaining insights on the causes of the retarding effect of superplasticizers on the hydration of Portland cement. In order to simplify the complex interactions occurring during the hydration of Portland cement the majority of the work focuses on the interaction of superplasticizer and tricalcium silicate (Ca3SiO5 or C3S, the main compound of Portland cement clinker). The tests are performed in three main parts accompanied by methods as for example isothermal conduction calorimetry, electrical conductivity, Electron Microscopy, ICP-OES, TOC, as well as Analytical Ultracentrifugation.
In the first main part and based on the interaction of cations and anionic charges of polymers, the interactions between calcium ions and superplasticizers are investigated. As a main effect calcium ions are complexed by the functional groups of the polymers (carboxy, sulfonic). Calcium ions may be both dissolved in the aqueous phase and a constitute of particle interfaces. Besides these effects it is furthermore shown that superplasticizers induce the formation of nanoscaled particles which are dispersed in the aqueous phase (cluster formation). Analogous to recent findings in the field of biomineralization, it is reasonable to assume that these nanoparticles influence the crystal growth by their assembly process.
Based on the assumption that superplasticizers hinder either or both dissolution and precipitation and by that retard the cement hydration, the impact on separate reactions is investigated. On experiments that address the solubility of C-S-H phases and portlandite, it is shown that complexation of calcium ions in the aqueous phase by functional groups of polymers increases the solubility of portlandite. Contrary, in case of C-S-H solubility the complexation of calcium ions in solution leads to decrease of the calcium ion concentration in the aqueous phase. These effects are explained by differences in adsorption of polymers on C-S-H phases and portlandite. It is proposed that adsorption is stronger on C-S-H phases compared to portlandite due to the increased specific surface area of C-S-H phases. Following that, it is claimed that before polymers are able to adsorb on C-S-H phases the functional groups must be screened by calcium ions in the aqueous phase. It is further shown that data regarding the impact of superplasticizers on the unconstrained dissolution rate of C3S does not provide a clear relation to the overall retarding effect occurring during the hydration of C3S. Both increased and decreased dissolution rate with respect to the reference sample are detected. If the complexation capability of the superplasticizers is considered then also a reduced dissolution rate of C3S is determined. Despite the fact that the global hydration process is accelerated, the addition of calcite leads to a slower dissolution rate. Thus, a hindered unconstrained dissolution of C3S as possibly cause for the retarding effect still remains open for discussion. In the last section of this part, the pure crystallization of hydrate phases (C-S-H phases, portlandite) is fathomed. Results clearly show that superplasticizers prolong the induction time and modify the rate of crystal growth during pure crystallization in particular due to the complexation of ions in solution. But this effect is insufficient to account for the overall retarding effect. Further important factors are the blocking of crystal growth faces by adsorbed polymers and the dispersion of nanoscaled particles which hinders their agglomeration in order to build up crystals.
In the last main part of the work, the previously gathered results are utilized in order to investigate hydration kinetics. During hydration, dissolution and precipitation occur in parallel. Thereby, special attention is laid on the ion composition of the aqueous phase of C3S pastes and suspensions in order to determine the rate limiting step. All in all it is concluded that the retarding effect of superplasticizers on the hydration of tricalcium silicate is based on the retardation of crystallization of hydrate phases (C-S-H phases and portlandite). Thereby, the two effects complexation of calcium ions on surfaces and stabilization of nanoscaled particles are of major importance. These mechanisms may partly be compensated by template performance and increase in solubility by complexation of ions in solution. The decreased dissolution rate of C3S by the presence of superplasticizers during the in parallel occuring hydration process can only be assessed indirectly by means of the development of the ion concentrations in the aqueous phase (reaction path). Whether this observation is the cause or the consequence within the dissolution-precipitation process and therefore accounts for the retarding effect remains a topic for further investigations.
Besides these results it is shown that superplasticizers can be associated chemically with inhibitors because they reduce the frequency factor to end the induction period. Because the activation energy is widely unaffected it is shown that the basic reaction mechanism sustain. Furthermore, a method was developed which permits for the first time the determination of ion concentrations in the aqueous phase of C3S pastes in-situ. It is shown that during the C3S hydration the ion concentration in the aqueous phase is developed correspondingly to the heat release rate (calorimetry). The method permits the differentiation of the acceleration period in three stages. It is emphasized that crystallization of the product phases of C3S hydration, namely C-S-H phases and portlandite, are responsible for the end of the induction period.
Rice husk ash (RHA) is classified as a highly reactive pozzolan. It has a very high silica content similar to that of silica fume (SF). Using less-expensive and locally available RHA as a mineral admixture in concrete brings ample benefits to the costs, the technical properties of concrete as well as to the environment. An experimental study of the effect of RHA blending on workability, strength and durability of high performance fine-grained concrete (HPFGC) is presented. The results show that the addition of RHA to HPFGC improved significantly compressive strength, splitting tensile strength and chloride penetration resistance. Interestingly, the ratio of compressive strength to splitting tensile strength of HPFGC was lower than that of ordinary concrete, especially for the concrete made with 20 % RHA. Compressive strength and splitting tensile strength of HPFGC containing RHA was similar and slightly higher, respectively, than for HPFGC containing SF. Chloride penetration resistance of HPFGC containing 10–15 % RHA was comparable with that of HPFGC containing 10 % SF.
In this Paper, we explored the relation between the electricity consumption in residential sector and the automobile energy consumption in transportation sector in accordance with the location of city by employing Geographic Information System (GIS). We found in the study that the electricity consumption per capita has a tendency that is higher in city center and lower in suburbs in Utsunomiya city. It is also noted that there is little difference among total consumption between city center and suburbs, despite the fact that the density of electric appliances tends to increase in a small size house of city center and the amount of automobile energy consumption from residence is lower in city center than in suburbs.
The construction industry is a supportive industry in China. IT (information technolgy), including computer technology and communication technology, as a whole is regarded as the most important means to upgrade the construction industry so that research projects were organized by Chinese government to further the application of IT in the construction industry. This study originated from one of the projects and is aimed at grasping the general situation on the application of IT in the construction industry. A questionnaire was designed for the survey, which used stratified proportional sampling method, and was carried out under the help of a government agency. This study can not only provide sound foundation for the government to make relative policies, but also reveal references for the firms in construction industry to apply IT in their business. This paper presents the preliminary result of the survey.
Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses.
The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity.
A vast number of existing buildings were constructed before the development and enforcement of seismic design codes, which run into the risk of being severely damaged under the action of seismic excitations. This poses not only a threat to the life of people but also affects the socio-economic stability in the affected area. Therefore, it is necessary to assess such buildings’ present vulnerability to make an educated decision regarding risk mitigation by seismic strengthening techniques such as retrofitting. However, it is economically and timely manner not feasible to inspect, repair, and augment every old building on an urban scale. As a result, a reliable rapid screening methods, namely Rapid Visual Screening (RVS), have garnered increasing interest among researchers and decision-makers alike. In this study, the effectiveness of five different Machine Learning (ML) techniques in vulnerability prediction applications have been investigated. The damage data of four different earthquakes from Ecuador, Haiti, Nepal, and South Korea, have been utilized to train and test the developed models. Eight performance modifiers have been implemented as variables with a supervised ML. The investigations on this paper illustrate that the assessed vulnerability classes by ML techniques were very close to the actual damage levels observed in the buildings.
Explicit solutions for the cohesive energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. The dependence of the cohesive energy on their size, spacing and crossing angles is analyzed. Checking against full atom molecular dynamics calculations and available experimental results shows that the continuum solution has high accuracy. The equilibrium distances between the nanotubes, graphene and substrates with minimum cohesive energy are also provided explicitly. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and substrates, and designing composites and nanoelectromechanical systems.
In recent decades, a multitude of concepts and models were developed to understand, assess and predict muscular mechanics in the context of physiological and pathological events.
Most of these models are highly specialized and designed to selectively address fields in, e.g., medicine, sports science, forensics, product design or CGI; their data are often not transferable to other ranges of application. A single universal model, which covers the details of biochemical and neural processes, as well as the development of internal and external force and motion patterns and appearance could not be practical with regard to the diversity of the questions to be investigated and the task to find answers efficiently. With reasonable limitations though, a generalized approach is feasible.
The objective of the work at hand was to develop a model for muscle simulation which covers the phenomenological aspects, and thus is universally applicable in domains where up until now specialized models were utilized. This includes investigations on active and passive motion, structural interaction of muscles within the body and with external elements, for example in crash scenarios, but also research topics like the verification of in vivo experiments and parameter identification. For this purpose, elements for the simulation of incompressible deformations were studied, adapted and implemented into the finite element code SLang. Various anisotropic, visco-elastic muscle models were developed or enhanced. The applicability was demonstrated on the base of several examples, and a general base for the implementation of further material models was developed and elaborated.
A UNIFIED APPROACH FOR THE TREATMENT OF SOME HIGHER DIMENSIONAL DIRAC TYPE EQUATIONS ON SPHERES
(2010)
Using Clifford analysis methods, we provide a unified approach to obtain explicit solutions of some partial differential equations combining the n-dimensional Dirac and Euler operators, including generalizations of the classical time-harmonic Maxwell equations. The obtained regular solutions show strong connections between hypergeometric functions and homogeneous polynomials in the kernel of the Dirac operator.
The development of a life cycle structured cooperation platform is described, which is based on an integrated process and goal-oriented project model. Furthermore the structure of a life cycle oriented object structure model and its implementation in the platform are documented. The complete conceptual model is described, which represents the basis of a lifecycle -oriented structuring of the planning object and supports the thematic classification of the object and project management data.
The paper describes a concept for the step-by-step computer-aided capture and representation of geometric building data in the context of planning-oriented building surveying. Selected aspects of the concept have been implemented and tested as prototypes. The process of step-by-step capture and representation is determined by the order in which the user experiences the building. Only the information that the user knows (can see) or can reasonably deduce is represented. In addition approaches to the flexible combination of different measuring techniques and geometric abstractions are described which are based upon geodetic computational adjustment.
This paper is concerned with the numerical treatment of quasilinear elliptic partial differential equations. In order to solve the given equation we propose to use a Galerkin approach, but, in contrast to conventional finite element discretizations, we work with trial spaces that, not only exhibit the usual approximation and good localization properties, but, in addition, lead to expansions of any element in the underlying Hilbert spaces in terms in multiscale or wavelet bases with certain stability properties. Specifically, we select as trial spaces a nested sequence of spaces from an appropriate biorthogonal multiscale analysis. This gives rise to a nonlinear discretized system. To overcome the problems of nonlinearity, we make use of the machinery of interpolating wavelets to obtain knot oriented quadrature rules. Finally, Newton's method is applied to approximate the solution in the given ansatz space. The results of some numerical experiments with different biorthogonal systems, confirming the applicability of our scheme, are presented.
Anlass zum Abriss der Brücke; Das abzubrechende Bauwerk; Vorgaben für den Abbruch (gemäß der Ausschreibung, aus statischer Sicht, aus Arbeitsschutzgründen); Abbruch der Aufbauten und der Fahrbahnplatte (Abbruch der Aufbauten, Problem Festpunkt Bogenscheitel – Fahrbahn, Abbruch Plattenbalken und Pfeilerscheiben); Abbruch der Bögen (Abbruchgerüst, Scheitelöffnung, Bogenrückbau, Kontrollsystem). Noch nie zuvor war in Deutschland eine Bogenbrücke auf diese Art und Weise abgebrochen worden. Maßgeblich für das Gelingen des schwierigen Rückbaus der Teufelstalbrücke war das Verantwortungsbewusstsein der Beteiligten im Zusammenhang mit der notwendigen Risikobereitschaft, aber auch mit der Vermeidung unnötiger Restrisiken schon von vornherein. Zur Risikominimierung trugen die gute Organisation des Vorhabens, regelmäßige gemeinsame Baustellenbegehungen mit Vertretern der für Sicherheit zuständigen Institutionen (Amt für Arbeitsschutz Gera, Bau-Berufsgenossenschaft, Sicher-heits- und Gesundheitsschutzkoordinator) sowie die technische Ausstattung bei. All dies führte letztendlich zum Erfolg einer Maßnahme, bei der man den bisherigen Erfahrungsbereich verlassen musste.
Speziell für die Sandwich-Platten der Außenfassade von DDR-Plattenbauten, die in ihrem Inneren in den meisten Fällen Mineralwolle (Handelsname: Kamilit) enthalten, wurden belastungsarme Abbruch- bzw. Rückbautechnologien untersucht und durch Gefahrstoffmessungen begleitet. Es werden Vorschläge für zukünftig zu bevorzugende Abbruchtechnologien unterbreitet.
Warum werden in aktuellen Diskussionen Wohnungsgenossenschaften immer wieder als zentrale Akteure einer gemeinwohlorientierten Wohnraumversorgung benannt – obwohl sie kaum zur Schaffung neuen bezahlbaren Wohnraums beitragen? Warum wehrt sich die Mehrzahl der Wohnungsgenossenschaften mit Händen und Füßen gegen die Wiedereinführung eines Gesetzes zur Wohnungsgemeinnützigkeit, obwohl es doch gerade dieses Gesetz war, dass sie im 20. Jahrhundert zu im internationalen Vergleich großen Unternehmen wachsen ließ? Sind Wohnungsgenossenschaften nun klientilistische, wenig demokratische und nur halb dekommodifizierte Marktteilnehmer oder wichtiger Teil der Wohnungsversorgung der unteren Mittelschicht? Wer Antworten auf diese und andere Fragen sucht und Differenziertheit in ihrer Beantwortung aushält, lese Joscha Metzers Dissertation „Genossenschaften und die Wohnungsfrage.
Objektorientierte Anwendungen aus dem Ingenieurwesen bestehen aus strukturierten Mengen, deren Elemente Objekte sind. Zwischen den Objekten bestehen vielfältige Abhängigkeiten. Die Beziehungen sind zur Zeit der Entwicklung einer Anwendung nur teilweise bekannt. Beziehungen zwischen Objekten müssen deshalb auch zur Laufzeit der Anwendung erzeugt und gelöscht werden können. Aufgrund des hohen Rechenaufwandes wird die Objektbasis einer Anwendung verzögert aktualisiert. Eine objektorientierte Anwendung wird auf Grundlage der Systemtheorie als System formal beschrieben. Als Elemente des Systems werden Attribute, Objekte und Objektmengen eingeführt. Die in den Methoden der Objekte implementierten Algorithmen bestimmen die Bindungsrelation des Systems. Auf Grundlage der Graphentheorie wird die Reihenfolge der Aktualisierung der Objektbasis berechnet. ...
In this article, I show why it is necessary to abolish the use of predictive algorithms in the US criminal justice system at sentencing. After presenting the functioning of these algorithms in their context of emergence, I offer three arguments to demonstrate why their abolition is imperative. First, I show that sentencing based on predictive algorithms induces a process of rewriting the temporality of the judged individual, flattening their life into a present inescapably doomed by its past. Second, I demonstrate that recursive processes, comprising predictive algorithms and the decisions based on their predictions, systematically suppress outliers and progressively transform reality to match predictions. In my third and final argument, I show that decisions made on the basis of predictive algorithms actively perform a biopolitical understanding of justice as management and modulation of risks. In such a framework, justice becomes a means to maintain a perverse social homeostasis that systematically exposes disenfranchised Black and Brown populations to risk.
The AEC industry is conscious of the potentials arising from the usage of mobile computer systems to increase productivity by streamlining their business processes. Discussions are no longer on whether or not to use a mobile computer solution, but rather, on how it should be used. However, the implantation process of this new technology in Architecture, Engineering and Construction (AEC) and Facility Management (FM) practise is very slow and should be improved. One way to encourage and ease the usage of mobile computer systems in AEC is a more process-oriented usability and context appropriateness of mobile computer solutions. Context-sensitivity is defined as a crucial feature to be taken into account for further research in the area of Mobile Computing. Context-sensitive, mobile IT-solutions depend on two features: (1) flexible definitions of (construction) processes describing the context and (2) tools for flexible, multi-dimensional information management representing the context. It is on this premise that the authors propose the n-dimensional data management approach for the implementation of mobile computing solutions. In this paper, we analyse working scenarios in the AEC and FM sector, defining context aspects which are transformed and formalized as dimension hierarchies of the envisaged context model.
For decades in Germany, historical research on dictatorial urban design in the first half of the 20th century focused on the National Socialist period. Studies on the urban design practices of other dictatorships remained an exception. This has changed. Meanwhile, the urban production practices of the Mussolini, Stalin, Salazar, Hitler and Franco dictatorships have become the subject of comprehensive research projects. Recently, a research group that studies dictatorial urban design in 20th century Europe has emerged at the Bauhaus-Institut für Geschichte und Theorie der Architektur und der Planung. The group is already able to refer to various research results.
Part of the research group’s self-conception is the assumption that the urban design practices of the named dictatorships can only be properly understood from a European perspective. The dictatorships influenced one another substantially. Furthermore, the specificities of the practices of each dictatorship can only be discerned if one can compare them to those of the other dictatorships. This approach requires strict adherence to the research methods of planning history and urban design theory. Meanwhile, these methods must be opened
to include those of general historical studies.
With this symposium, the research group aims to further qualify this European perspective. The aim is to pursue an inventory of the various national historiographies on the topic of “urban design and dictatorship”. This inventory should offer an overview on the general national level of historical research on urban design as well as on the level of particular urban design projects, persons or topics.
The symposium took place in Weimar, November 21-22, 2013. It was organized by Harald Bodenschatz, Piero Sassi and Max Welch Guerra and funded by the DAAD (German Academic Exchange Service).
In der Arbeit werden Möglichkeiten aufgezeigt, die Tragfähigkeit von Queranschlüssen an Trägern aus Voll- und Brettschichtholz abzuschätzen. Die Tragfähigkeit dieser Anschlüsse wird nicht allein durch die Tragfähigkeit der mechanischen Verbindungsmittel selbst begrenzt. Die Tragfähigkeit der Verbindungsmittel wird in dieser Arbeit a priori als hinreichend betrachtet. Sie kann z. B. nach der Theorie von JOHANSEN bestimmt werden. Insbesondere bei solchen Anschlüssen, welche unterhalb der Schwerachse von Trägern angeordnet sind, erzeugen die durch die Verbindungsmittel eingeleiteten Lasten Beanspruchungen, welche die Tragfähigkeiten dieser Anschlüsse bestimmen. Die Abschätzung der Tragfähigkeit auf der Basis von Spannungen hat bei dieser Problemstellung methodische Schwächen. Bauteile aus Holz können unter Gebrauchsbedingungen rißbehaftet sein. Mit den Methoden der Linear-Elastischen Bruchmechanik kann die Tragfähigkeit von rißbehafteten Bauteilen beurteilt werden. Es werden wegen der Vielzahl möglicher Ausführungvarianten lediglich Anschlüsse betrachtet, welche mit stiftförmigen Verbindungsmitteln hergestellt werden. Zur Bestimmung bruchmechanischer Kennwerte werden numerische Methoden angewendet. Es werden wichtige Parameter dieser Anschlüsse untersucht und hinsichtlich ihrer Berücksichtigung im Rechenmodell bewertet. Zur Verifizierung des Rechenmodells werden Vergleiche mit experimentellen Untersuchungen anderer Wissenschaftler angestellt. Der Einsatz verschiedener Versagenskriterien wird diskutiert. Schließlich wird ein formaler Zusammenhang zur Abschätzung der Tragfähigkeit für einzelne Verbindungsmittel hergestellt. Weiterhin wird die Tragfähigkeit von praxisüblichen Anschlüssen anhand einfacher Zusammenhänge aufgezeigt.
An architecture of a distributed planning system for the building industry has been developed. The emphasis is on highly collaborative environments in steelwork, timber construction etc. where designers concurrently handle 3D models. The overall system connects local design systems by the so-called Design Framework DFW. This framework consists of the definition of distributed components and protocols which make the collaborative design work. The process of collaborative design has been formalized on an abstract level. This paper describes how this has been done. A sample is given to illustrate the mapping of concrete scenarios of the ‘real design world’ to an abstract scenario level. This work is funded by the Deutsche Forschungsgemeinschaft DFG as part of the project SPP1103 (Meißner et al. 2003).
The paper presents the abstraction of process relevant information in order to enable the workflow management based on semantic data. It is shown for three examples, how the standards define the information needed to perform a certain planning activity. Abstraction of process relevant information is discussed for different granularities of the underlying processmodel. As one possible application ProMiSE is introduced, which uses process relevant data in individual tokens in a petri-net based process-model.
Der Beitrag basiert auf den Ansätzen und Ergebnissen des Forschungsprojekts >Prozessorientierte Vernetzung von Ingenieurplanungen am Beispiel der Geotechnik<, das im Rahmen des Schwerpunktprogramms 1103 >Vernetzt-kooperative Planungsprozesse im Konstruktiven Ingenieurbau< von der DFG gefördert wird. Ziel des gemeinsam mit dem Institut für Numerische Methoden und Informatik im Bauwesen an der TU Darmstadt durchgeführten Forschungsprojekts ist die Entwicklung einer netzwerkbasierten Kooperationsplattform zur Unterstützung von geotechnischen Ingenieurplanungen. Daher konzentriert sich das Forschungsprojekt auf die Abbildung und Koordination der Planungsprozesse für Projekte des Konstruktiven Ingenieurbaus vor dem Hintergrund der stark arbeitsteiligen Projektbearbeitung in einer verteilten Rechnerumgebung. Der Beitrag stellt die Abstraktion von Prozessmustern im Bauplanungsprozess als Basis für die dynamische Prozessmodellierung in einem Kooperationsmodell dar. Ziel ist es, durch die Identifikation der mit dem Entwurf und der Dimensionierung eines Bauteils verbundenen Planungs- und Abstimmungsprozesse einen bauteilbezogenen Katalog von Prozessmustern zu abstrahieren. Die einzelnen Prozessmuster werden in jedem Bauplanungsprozess dynamisch über geeignete Kopplungsmechanismen in das aktuelle Prozessmodell integriert, so dass die für den Bauplanungsprozess typischen Veränderungen der Konstruktion und der Zusammensetzung des Planungsteams im Prozessmodell berücksichtigt werden können. Dazu werden im Beitrag die bisherigen Ergebnisse der Analyse des Planungsprozesses eines großen innerstädtischen Bauvorhabens, das als Referenzobjekt dient, sowie typischer Planungsszenarien in der Geotechnik vorgestellt. Anschließend werden Grundlagen und methodische Ansätze zur Modellierung von Prozessen mit der Methode der farbigen Petri-Netze mit individuellen Marken vorgestellt. Anhand von Beispielen für bauteilorientierte Prozessmuster wird die Funktionalität der Prozessmuster in sich und im gegenseitigen Zusammenspiel erläutert
The lattice dynamics properties are investigated for twisting bilayer graphene. There are big jumps for the inter-layer potential at twisting angle θ=0° and 60°, implying the stability of Bernal-stacking and the instability of AA-stacking structures, while a long platform in [8,55]° indicates the ease of twisting bilayer graphene in this wide angle range. Significant frequency shifts are observed for the z breathing mode around θ=0° and 60°, while the frequency is a constant in a wide range [8,55]°. Using the z breathing mode, a mechanical nanoresonator is proposed to operate on a robust resonant frequency in terahertz range.
The technique of Acoustic travel-time TOMography (ATOM) allows for measuring the distribution of air temperatures throughout the entire room based on the determined sound-travel-times of early reflections, currently up to second order reflections. The number of detected early reflections in the room impulse response (RIR) which stands for the desired sound paths inside the room, has a significant impact on the resolution of reconstructed temperatures. This study investigates the possibility of utilizing an array of directional sound sources for ATOM measurements instead of a single omnidirectional loudspeaker used in the previous studies [1–3]. The developed measurement setup consists of two directional sound sources placed near the edge of the floor in the climate chamber of the Bauhaus-University Weimar and one omnidirectional receiver at center of the room near the ceiling. In order to compensate for the reduced number of sound paths when using directional sound sources, it is proposed to take high-energy early reflections up to third order into account. For this purpose, the simulated travel times up to third-order image sources were implemented in the image source model (ISM) algorithm, by which these early reflections can be detected effectively for air temperature reconstructions. To minimize the uncertainties of travel-times estimation due to the positioning of the sound transducers inside the room, measurements were conducted to determine the exact emitting point of the utilized sound source i.e. its acoustic center (AC). For these measurements, three types of excitation signals (MLS, linear and logarithmic chirp signals) with various frequency ranges were used considering that the acoustic center of a sound source is a frequency dependent parameter [4]. Furthermore, measurements were conducted to determine an optimum excitation signal based on the given condition of the ATOM measurement set-up which defines an optimum method for the RIR estimation correspondingly. Finally, the uncertainty of the measuring system utilizing an array of directional sound sources was analyzed.
Acoustic travel-time tomography (ATOM) determines the distribution of the temperature in a propagation medium by measuring the travel-time of acoustic signals between transmitters and receivers. To employ ATOM for indoor climate measurements, the impulse responses have been measured in the climate chamber lab of the Bauhaus-University Weimar and compared with the theoretical results of its image source model (ISM). A challenging task is distinguishing the reflections of interest in the reflectogram when the sound rays have similar travel-times. This paper presents a numerical method to address this problem by finding optimal positions of transmitter and receiver, since they have a direct impact on the distribution of travel times. These optimal positions have the minimum number of simultaneous arrival time within a threshold level. Moreover, for the tomographic reconstruction, when some of the voxels remain empty of sound-rays, it leads to inaccurate determination of the air temperature within those voxels. Based on the presented numerical method, the number of empty tomographic voxels are minimized to ensure the best sound-ray coverage of the room. Subsequently, a spatial temperature distribution is estimated by simultaneous iterative reconstruction technique (SIRT). The experimental set-up in the climate chamber verifies the simulation results.
Expert systems integrating fuzzy reasoning techniques represent a powerful tool to support practicing engineers during the early stages of structural design. In this context fuzzy models have proved themselves to be very suitable for the representation of complex design knowledge. However their definition is a laborious task. This paper introduces an approach for the design and the optimization of fuzzy systems based upon Genetic Programming. To keep the emerging fuzzy systems transparent a new framework for the definition of linguistic variables is also introduced.
The uncertainty existing in the construction industry is bigger than in other industries. Consequently, most construction projects do not go totally as planned. The project management plan needs therefore to be adapted repeatedly within the project lifecycle to suit the actual project conditions. Generally, the risks of change in the project management plan are difficult to be identified in advance, especially if these risks are caused by unexpected events such as human errors or changes in the client preferences. The knowledge acquired from different resources is essential to identify the probable deviations as well as to find proper solutions to the faced change risks. Hence, it is necessary to have a knowledge base that contains known solutions for the common exceptional cases that may cause changes in each construction domain. The ongoing research work presented in this paper uses the process modeling technique of Event-driven Process Chains to describe different patterns of structure changes in the schedule networks. This results in several so called “change templates”. Under each template different types of change risk/ response pairs can be categorized and stored in a knowledge base. This knowledge base is described as an ontology model populated with reference construction process data. The implementation of the developed approach can be seen as an iterative scheduling cycle that will be repeated within the project lifecycle as new change risks surface. This can help to check the availability of ready solutions in the knowledge base for the situation at hand. Moreover, if the solution is adopted, CPSP, “Change Project Schedule Plan „a prototype developed for the purpose of this research work, will be used to make the needed structure changes of the schedule network automatically based on the change template. What-If scenarios can be implemented using the CPSP prototype in the planning phase to study the effect of specific situations without endangering the success of the project objectives. Hence, better designed and more maintainable project schedules can be achieved.
The numerical simulation of damage using phenomenological models on the macroscale was state of the art for many decades. However, such models are not able to capture the complex nature of damage, which simultaneously proceeds on multiple length scales. Furthermore, these phenomenological models usually contain damage parameters, which are physically not interpretable. Consequently, a reasonable experimental determination of these parameters is often impossible. In the last twenty years, the ongoing advance in computational capacities provided new opportunities for more and more detailed studies of the microstructural damage behavior. Today, multiphase models with several million degrees of freedom enable for the numerical simulation of micro-damage phenomena in naturally heterogeneous materials. Therewith, the application of multiscale concepts for the numerical investigation of the complex nature of damage can be realized. The presented thesis contributes to a hierarchical multiscale strategy for the simulation of brittle intergranular damage in polycrystalline materials, for example aluminum. The numerical investigation of physical damage phenomena on an atomistic microscale and the integration of these physically based information into damage models on the continuum meso- and macroscale is intended. Therefore, numerical methods for the damage analysis on the micro- and mesoscale including the scale transfer are presented and the transition to the macroscale is discussed. The investigation of brittle intergranular damage on the microscale is realized by the application of the nonlocal Quasicontinuum method, which fully describes the material behavior by atomistic potential functions, but reduces the number of atomic degrees of freedom by introducing kinematic couplings. Since this promising method is applied only by a limited group of researchers for special problems, necessary improvements have been realized in an own parallelized implementation of the 3D nonlocal Quasicontinuum method. The aim of this implementation was to develop and combine robust and efficient algorithms for a general use of the Quasicontinuum method, and therewith to allow for the atomistic damage analysis in arbitrary grain boundary configurations. The implementation is applied in analyses of brittle intergranular damage in ideal and nonideal grain boundary models of FCC aluminum, considering arbitrary misorientations. From the microscale simulations traction separation laws are derived, which describe grain boundary decohesion on the mesoscale. Traction separation laws are part of cohesive zone models to simulate the brittle interface decohesion in heterogeneous polycrystal structures. 2D and 3D mesoscale models are presented, which are able to reproduce crack initiation and propagation along cohesive interfaces in polycrystals. An improved Voronoi algorithm is developed in 2D to generate polycrystal material structures based on arbitrary distribution functions of grain size. The new model is more flexible in representing realistic grain size distributions. Further improvements of the 2D model are realized by the implementation and application of an orthotropic material model with Hill plasticity criterion to grains. The 2D and 3D polycrystal models are applied to analyze crack initiation and propagation in statically loaded samples of aluminum on the mesoscale without the necessity of initial damage definition.
We present recent developments of adaptive wavelet solvers for elliptic eigenvalue problems. We describe the underlying abstract iteration scheme of the preconditioned perturbed iteration. We apply the iteration to a simple model problem in order to identify the main ideas which a numerical realization of the abstract scheme is based upon. This indicates how these concepts carry over to wavelet discretizations. Finally we present numerical results for the Poisson eigenvalue problem on an L-shaped domain.
Major problems of applying selective sensitivity to system identification are requirement of precise knowledge about the system parameters and realization of the required system of forces. This work presents a procedure which is able to deriving selectively sensitive excitation by iterative experiments. The first step is to determine the selectively sensitive displacement and selectively sensitive force patterns. These values are obtained by introducing the prior information of system parameters into an optimization which minimizes the sensitivities of the structure response with respect to the unselected parameters while keeping the sensitivities with respect to the selected parameters as a constant. In a second step the force pattern is used to derive dynamic loads on the tested structure and measurements are carried out. An automatic control ensures the required excitation forces. In a third step, measured outputs are employed to update the prior information. The strategy is to minimize the difference between a predicted displacement response, formulated as function of the unknown parameters and the measured displacements, and the selectively sensitive displacement calculated in the first step. With the updated values of the parameters a re-analysis of selective sensitivity is performed and the experiment is repeated until the displacement response of the model and the actual structure are conformed. As an illustration a simply supported beam made of steel, vibrated by harmonic excitation is investigated, thereby demonstrating that the adaptive excitation can be obtained efficiently.
The nonlinear behavior of concrete can be attributed to the propagation of microcracks within the heterogeneous internal material structure. In this thesis, a mesoscale model is developed which allows for the explicit simulation of these microcracks. Consequently, the actual physical phenomena causing the complex nonlinear macroscopic behavior of concrete can be represented using rather simple material formulations. On the mesoscale, the numerical model explicitly resolves the components of the internal material structure. For concrete, a three-phase model consisting of aggregates, mortar matrix and interfacial transition zone is proposed. Based on prescribed grading curves, an efficient algorithm for the generation of three-dimensional aggregate distributions using ellipsoids is presented. In the numerical model, tensile failure of the mortar matrix is described using a continuum damage approach. In order to reduce spurious mesh sensitivities, introduced by the softening behavior of the matrix material, nonlocal integral-type material formulations are applied. The propagation of cracks at the interface between aggregates and mortar matrix is represented in a discrete way using a cohesive crack approach. The iterative solution procedure is stabilized using a new path following constraint within the framework of load-displacement-constraint methods which allows for an efficient representation of snap-back phenomena. In several examples, the influence of the randomly generated heterogeneous material structure on the stochastic scatter of the results is analyzed. Furthermore, the ability of mesoscale models to represent size effects is investigated. Mesoscale simulations require the discretization of the internal material structure. Compared to simulations on the macroscale, the numerical effort and the memory demand increases dramatically. Due to the complexity of the numerical model, mesoscale simulations are, in general, limited to small specimens. In this thesis, an adaptive heterogeneous multiscale approach is presented which allows for the incorporation of mesoscale models within nonlinear simulations of concrete structures. In heterogeneous multiscale models, only critical regions, i.e. regions in which damage develops, are resolved on the mesoscale, whereas undamaged or sparsely damage regions are modeled on the macroscale. A crucial point in simulations with heterogeneous multiscale models is the coupling of sub-domains discretized on different length scales. The sub-domains differ not only in the size of the finite elements but also in the constitutive description. In this thesis, different methods for the coupling of non-matching discretizations - constraint equations, the mortar method and the arlequin method - are investigated and the application to heterogeneous multiscale models is presented. Another important point is the detection of critical regions. An adaptive solution procedure allowing the transfer of macroscale sub-domains to the mesoscale is proposed. In this context, several indicators which trigger the model adaptation are introduced. Finally, the application of the proposed adaptive heterogeneous multiscale approach in nonlinear simulations of concrete structures is presented.
The advent of high-performance mobile phones has opened up the opportunity to develop new context-aware applications for everyday life. In particular, applications for context-aware information retrieval in conjunction with image-based object recognition have become a focal area of recent research. In this thesis we introduce an adaptive mobile museum guidance system that allows visitors in a museum to identify exhibits by taking a picture with their mobile phone. Besides approaches to object recognition, we present different adaptation techniques that improve classification performance. After providing a comprehensive background of context-aware mobile information systems in general, we present an on-device object recognition algorithm and show how its classification performance can be improved by capturing multiple images of a single exhibit. To accomplish this, we combine the classification results of the individual pictures and consider the perspective relations among the retrieved database images. In order to identify multiple exhibits in pictures we present an approach that uses the spatial relationships among the objects in images. They make it possible to infer and validate the locations of undetected objects relative to the detected ones and additionally improve classification performance. To cope with environmental influences, we introduce an adaptation technique that establishes ad-hoc wireless networks among the visitors’ mobile devices to exchange classification data. This ensures constant classification rates under varying illumination levels and changing object placement. Finally, in addition to localization using RF-technology, we present an adaptation technique that uses user-generated spatio-temporal pathway data for person movement prediction. Based on the history of previously visited exhibits, the algorithm determines possible future locations and incorporates these predictions into the object classification process. This increases classification performance and offers benefits comparable to traditional localization approaches but without the need for additional hardware. Through multiple field studies and laboratory experiments we demonstrate the benefits of each approach and show how they influence the overall classification rate.
One major research focus in the Material Science and Engineering Community in the past decade has been to obtain a more fundamental understanding on the phenomenon 'material failure'. Such an understanding is critical for engineers and scientists developing new materials with higher strength and toughness, developing robust designs against failure, or for those concerned with an accurate estimate of a component's design life. Defects like cracks and dislocations evolve at
nano scales and influence the macroscopic properties such as strength, toughness and ductility of a material. In engineering applications, the global response of the system is often governed by the behaviour at the smaller length scales. Hence, the sub-scale behaviour must be computed accurately for good predictions of the full scale behaviour.
Molecular Dynamics (MD) simulations promise to reveal the fundamental mechanics of material failure by modeling the atom to atom interactions. Since the atomistic dimensions are of the order of Angstroms ( A), approximately 85 billion atoms are required to model a 1 micro- m^3 volume of Copper. Therefore, pure atomistic models are prohibitively expensive with everyday engineering computations involving macroscopic cracks and shear bands, which are much larger than the atomistic length and time scales. To reduce the computational effort, multiscale methods are required, which are able to couple a continuum description of the structure with an atomistic description. In such paradigms, cracks and dislocations are explicitly modeled at the atomistic scale, whilst a self-consistent continuum model elsewhere.
Many multiscale methods for fracture are developed for "fictitious" materials based on "simple" potentials such as the Lennard-Jones potential. Moreover, multiscale methods for evolving cracks are rare. Efficient methods to coarse grain the fine scale defects are missing. However, the existing multiscale methods for fracture do not adaptively adjust the fine scale domain as the crack propagates. Most methods, therefore only "enlarge" the fine scale domain and therefore drastically increase computational cost. Adaptive adjustment requires the fine scale domain to be refined and coarsened. One of the major difficulties in multiscale methods for fracture is to up-scale fracture related material information from the fine scale to the coarse scale, in particular for complex crack problems. Most of the existing approaches therefore were applied to examples with comparatively few macroscopic cracks.
Key contributions
The bridging scale method is enhanced using the phantom node method so that cracks can be modeled at the coarse scale. To ensure self-consistency in the bulk, a virtual atom cluster is devised providing the response of the intact material at the coarse scale. A molecular statics model is employed in the fine scale where crack propagation is modeled by naturally breaking the bonds. The fine scale and coarse scale models are coupled by enforcing the displacement boundary conditions on the ghost atoms. An energy criterion is used to detect the crack tip location. Adaptive refinement and coarsening schemes are developed and implemented during the crack propagation. The results were observed to be in excellent agreement with the pure atomistic simulations. The developed multiscale method is one of the first adaptive multiscale method for fracture.
A robust and simple three dimensional coarse graining technique to convert a given atomistic region into an equivalent coarse region, in the context of multiscale fracture has been developed. The developed method is the first of its kind. The developed coarse graining technique can be applied to identify and upscale the defects like: cracks, dislocations and shear bands. The current method has been applied to estimate the equivalent coarse scale models of several complex fracture patterns arrived from the pure atomistic simulations. The upscaled fracture pattern agree well with the actual fracture pattern. The error in the potential energy of the pure atomistic and the coarse grained model was observed to be acceptable.
A first novel meshless adaptive multiscale method for fracture has been developed. The phantom node method is replaced by a meshless differential reproducing kernel particle method. The differential reproducing kernel particle method is comparatively more expensive but allows for a more "natural" coupling between the two scales due to the meshless interpolation functions. The higher order continuity is also beneficial. The centro symmetry parameter is used to detect the crack tip location. The developed multiscale method is employed to study the complex crack propagation. Results based on the meshless adaptive multiscale method were observed to be in excellent agreement with the pure atomistic simulations.
The developed multiscale methods are applied to study the fracture in practical materials like Graphene and Graphene on Silicon surface. The bond stretching and the bond reorientation were observed to be the net mechanisms of the crack growth in Graphene. The influence of time step on the crack propagation was studied using two different time steps. Pure atomistic simulations of fracture in Graphene on Silicon surface are presented. Details of the three dimensional multiscale method to study the fracture in Graphene on Silicon surface are discussed.
In engineering science the modeling and numerical analysis of complex systems and relations plays an important role. In order to realize such an investigation, for example a stochastic analysis, in a reasonable computational time, approximation procedure have been developed. A very famous approach is the response surface method, where the relation between input and output quantities is represented for example by global polynomials or local interpolation schemes as Moving Least Squares (MLS). In recent years artificial neural networks (ANN) have been applied as well for such purposes. Recently an adaptive response surface approach for reliability analyses was proposed, which is very efficient concerning the number of expensive limit state function evaluations. Due to the applied simplex interpolation the procedure is limited to small dimensions. In this paper this approach is extended for larger dimensions using combined ANN and MLS response surfaces for evaluating the adaptation criterion with only one set of joined limit state points. As adaptation criterion a combination by using the maximum difference in the conditional probabilities of failure and the maximum difference in the approximated radii is applied. Compared to response surfaces on directional samples or to plain directional sampling the failure probability can be estimated with a much smaller number of limit state points.
In this paper an adaptive heterogeneous multiscale model, which couples two substructures with different length scales into one numerical model is introduced for the simulation of damage in concrete. In the presented approach the initiation, propagation and coalescence of microcracks is simulated using a mesoscale model, which explicitly represents the heterogeneous material structure of concrete. The mesoscale model is restricted to the damaged parts of the structure, whereas the undamaged regions are simulated on the macroscale. As a result an adaptive enlargement of the mesoscale model during the simulation is necessary. In the first part of the paper the generation of the heterogeneous mesoscopic structure of concrete, the finite element discretization of the mesoscale model, the applied isotropic damage model and the cohesive zone model are briefly introduced. Furthermore the mesoscale simulation of a uniaxial tension test of a concrete prism is presented and own obtained numerical results are compared to experimental results. The second part is focused on the adaptive heterogeneous multiscale approach. Indicators for the model adaptation and for the coupling between the different numerical models will be introduced. The transfer from the macroscale to the mesoscale and the adaptive enlargement of the mesoscale substructure will be presented in detail. A nonlinear simulation of a realistic structure using an adaptive heterogeneous multiscale model is presented at the end of the paper to show the applicability of the proposed approach to large-scale structures.
We present an enhancement towards adaptive video training for PhoneGuide, a digital museum guidance system for ordinary camera–equipped mobile phones. It enables museum visitors to identify exhibits by capturing photos of them. In this article, a combined solution of object recognition and pervasive tracking is extended to a client–server–system for improving data acquisition and for supporting scale–invariant object recognition.
Die vorliegende Arbeit fokussiert die Optimierung freigeformter adaptiver Faserverbundflächentragwerke auf Basis einer entwickelten und auf einem parametrischen Gesamtmodell basierenden Entwurfsmethode. Die Übertragung adaptiver, natürlich inspirierter Vorgänge stellt eine weitreichende Inspirationsquelle dar. Adaptive Tragwerke können unter Anwendung von Smart Materials als materialsparende, filigrane Tragwerke ausgeführt werden. Die Erfüllung der Grenzzustände der Tragfähigkeit und der Gebrauchstauglichkeit wird nicht allein über die Querschnittsabmessungen sichergestellt. Die notwendige Bauteilsteifigkeit kann vielmehr durch Eintragung von Aktivierungsenergie (Operational Energy) realisiert werden. Auf diese Weise kann die aufgrund der Bauteilabmessungen gebundene Energie (Embodied Energy) minimiert werden. Die entwickelte Entwurfsmethode ermöglicht die Auslegung und Optimierung materialminimierter Schalentragwerke in einem mehrstufigen Prozess. Hierbei wird aus tragwerksplanerischer Sicht die numerische Formfindung, die statische Berechnung und die Aktor- und Sensorpositionierung berechnet. Zudem werden Analysen hinsichtlich der Nachhaltigkeit auf Basis einer Lebenszyklusanalyse durchgeführt. Aufgrund der unterschiedlichen, sich aber gegenseitig beeinflussenden Kriterien, ist eine Optimierung durchzuführen. In der vorliegenden Arbeit wird ein Ansatz zur Definition zulässiger Ökobilanzkennwerte von Smart Materials auf Basis der Energiedifferenz zwischen einer passiven und einer adaptiven Struktur vorgestellt. Anhand dieser Kennwerte kann die Entwicklung zukünftiger Smart Materials unter dem Aspekt der ganzheitlichen Nachhaltigkeit erfolgen. Die Allgemeingültigkeit und Übertragbarkeit der Entwurfsmethode auf weitere Tragsysteme im Bauwesen und speziell anderer Materialkonstellationen wird anhand verschiedener Beispiele aufgezeigt.
Framed-tube system with multiple internal tubes is analysed using an orthotropic box beam analogy approach in which each tube is individually modelled by a box beam that accounts for the flexural and shear deformations, as well as the shear-lag effects. A simple numerical modeling technique is proposed for estimating the shear-lag phenomenon in tube structures with multiple internal tubes. The proposed method idealizes the framed-tube structures with multiple internal tubes as equivalent multiple tubes, each composed of four equivalent orthotropic plate panels. The numerical analysis is based on the minimum potential energy principle in conjunction with the variational approach. The shear-lag phenomenon of such structures is studied taking into account the additional bending moments in the tubes. A detailed work is carried out through the numerical analysis of the additional bending moment. The moment factor is further introduced to identify the shear lag phenomenon along with the additional moment.
It is widely accepted that most people spend the majority of their lives indoors. Most individuals do not realize that while indoors, roughly half of heat exchange affecting their thermal comfort is in the form of thermal infrared radiation. We show that while researchers have been aware of its thermal comfort significance over the past century, systemic error has crept into the most common evaluation techniques, preventing adequate characterization of the radiant environment. Measuring and characterizing radiant heat transfer is a critical component of both building energy efficiency and occupant thermal comfort and productivity. Globe thermometers are typically used to measure mean radiant temperature (MRT), a commonly used metric for accounting for the radiant effects of an environment at a point in space. In this paper we extend previous field work to a controlled laboratory setting to (1) rigorously demonstrate that existing correction factors used in the American Society of Heating Ventilation and Air-conditioning Engineers (ASHRAE) Standard 55 or ISO7726 for using globe thermometers to quantify MRT are not sufficient; (2) develop a correction to improve the use of globe thermometers to address problems in the current standards; and (3) show that mean radiant temperature measured with ping-pong ball-sized globe thermometers is not reliable due to a stochastic convective bias. We also provide an analysis of the maximum precision of globe sensors themselves, a piece missing from the domain in contemporary literature.
Search engines are very good at answering queries that look for facts. Still, information needs that concern forming opinions on a controversial topic or making a decision remain a challenge for search engines. Since they are optimized to retrieve satisfying answers, search engines might emphasize a specific stance on a controversial topic in their ranking, amplifying bias in society in an undesired way. Argument retrieval systems support users in forming opinions about controversial topics by retrieving arguments for a given query. In this thesis, we address challenges in argument retrieval systems that concern integrating them in search engines, developing generalizable argument mining approaches, and enabling frame-guided delivery of arguments.
Adapting argument retrieval systems to search engines should start by identifying and analyzing information needs that look for arguments. To identify questions that look for arguments we develop a two-step annotation scheme that first identifies whether the context of a question is controversial, and if so, assigns it one of several question types: factual, method, and argumentative. Using this annotation scheme, we create a question dataset from the logs of a major search engine and use it to analyze the characteristics of argumentative questions. The analysis shows that the proportion of argumentative questions on controversial topics is substantial and that they mainly ask for reasons and predictions. The dataset is further used to develop a classifier to uniquely map questions to the question types, reaching a convincing F1-score of 0.78.
While the web offers an invaluable source of argumentative content to respond to argumentative questions, it is characterized by multiple genres (e.g., news articles and social fora). Exploiting the web as a source of arguments relies on developing argument mining approaches that generalize over genre. To this end, we approach the problem of how to extract argument units in a genre-robust way. Our experiments on argument unit segmentation show that transfer across genres is rather hard to achieve using existing sequence-to-sequence models.
Another property of text which argument mining approaches should generalize over is topic. Since new topics appear daily on which argument mining approaches are not trained, argument mining approaches should be developed in a topic-generalizable way. Towards this goal, we analyze the coverage of 31 argument corpora across topics using three topic ontologies. The analysis shows that the topics covered by existing argument corpora are biased toward a small subset of easily accessible controversial topics, hinting at the inability of existing approaches to generalize across topics. In addition to corpus construction standards, fostering topic generalizability requires a careful formulation of argument mining tasks. Same side stance classification is a reformulation of stance classification that makes it less dependent on the topic. First experiments on this task show promising results in generalizing across topics.
To be effective at persuading their audience, users of an argument retrieval system should select arguments from the retrieved results based on what frame they emphasize of a controversial topic. An open challenge is to develop an approach to identify the frames of an argument. To this end, we define a frame as a subset of arguments that share an aspect. We operationalize this model via an approach that identifies and removes the topic of arguments before clustering them into frames. We evaluate the approach on a dataset that covers 12,326 frames and show that identifying the topic of an argument and removing it helps to identify its frames.
The laser beam is a small, flexible and fast polishing tool. With laser radiation it is possible to finish many outlines or geometries on quartz glass surfaces in the shortest possible time. It’s a fact that the temperature developing while polishing determines the reachable surface smoothing and, as a negative result, causes material tensions. To find out which parameters are important for the laser polishing process and the surface roughness respectively and to estimate material tensions, temperature simulations and extensive polishing experiments took place. During these experiments starting and machining parameters were changed and temperatures were measured contact-free. The accuracy of thermal and mechanical simulation was improved in the case of advanced FE-analysis.
Seit die Datenverarbeitung in ihrer Komplexität sich der Thematik des Computer Integrated Manufacturing widmet gehört die Produktionsplanung und Steuerung zu jenen Bereichen, in denen eine Computerunterstützung am vordringlichsten erschien. Später sind betriebswirtschaftliche Gesamtlösungen entstanden, die (bis heute recht unpräzise) als Enterprise Resource Planning (ERP)-Systeme bezeichnet werden und in ihren Logistik-Modulen auch Funktionen der Produktionsplanung abdecken. Alle bekannten MRP-, PPS- und auch ERP-Systeme beruhen auf einer Sukzessivplanung. Advanced Planning and Scheduling (APS) Systems finden seit etwa 1995 zunehmend Interesse. Neben Demand Planning, Production Planning and Scheduling, Distribution Planning, Transportation Planning und Supply Chain Planning werden Lösungen für Anzahl und Standorte von Produktionsstätten und Auslieferungslagern, Zuordnung zu Produktionsstätten, Kapazitätsbestimmung für Arbeitskräfte und Betriebsmittel je Standort, Lagerhaltung je Teil und Lager, Bestimmung benötigter Transportmittel und Häufigkeit ihres Einsatzes, Zuordnung von Lagern zu Produktionsstätten von Märkten zu Lagern u.a.m. von APS-Systemen erwartet. D.h. APS-Systeme ergänzen ERP-Lösungen, nutzen die bereits durch das ERP-System vorhandenen Daten und benötigen neuartige Algorithmen und (Meta-) Heuristiken. Im Rahmen des Vortrages werden Modelle und Echtzeitalgorithmen zur Optimierung der Logistik für Prozesse mit kurzfristigen Anforderungen, geographisch verteilter Produktion, Lagerhaltung der Ausgangs-, Zwischen- und Endprodukte und wechselnden Transport-Bedingungen aus der Sicht der praktischen Umsetzung und Anwendung in Form einer ASP-Lösung aufgezeigt und diskutiert.
This thesis presents new interactive visualization techniques and systems intended to support users with real-world decisions such as selecting a product from a large variety of similar offerings, finding appropriate wording as a non-native speaker, and assessing an alleged case of plagiarism.
The Product Explorer is a significantly improved interactive Parallel Coordinates display for facilitating the product selection process in cases where many attributes and numerous alternatives have to be considered. A novel visual representation for categorical and ordered data with only few occurring values, the so-called extended areas, in combination with cubic curves for connecting the parallel axes, are crucial for providing an effective overview of the entire dataset and to facilitate the tracing of individual products. The visual query interface supports users in quickly narrowing down the product search to a small subset or even a single product. The scalability of the approach towards a large number of attributes and products is enhanced by the possibility of setting some constraints on final attributes and, therefore, reducing the number of considered attributes and data items. Furthermore, an attribute repository allows users to focus on the most important attributes at first and to bring in additional criteria for product selection later in the decision process. A user study confirmed that the Product Explorer is indeed an excellent tool for its intended purpose for casual users.
The Wordgraph is a layered graph visualization for the interactive exploration of search results for complex keywords-in-context queries. The system relies on the Netspeak web service and is designed to support non-native speakers in finding customary phrases. Uncertainties about the commonness of phrases are expressed with the help of wildcard-based queries. The visualization presents the alternatives for the wildcards in a multi-column layout: one column per wildcard with the other query fragments in between. The Wordgraph visualization displays the sorted results for all wildcards at once by appropriately arranging the words of each column. A user study confirmed that this is a significant advantage over simple textual result lists. Furthermore, visual interfaces to filter, navigate, and expand the graph allow interactive refinement and expansion of wildcard-containing queries.
Furthermore, this thesis presents an advanced visual analysis tool for assessing and presenting alleged cases of plagiarism and provides a three-level approach for exploring the so-called finding spots in their context. The overview shows the relationship of the entire suspicious document to the set of source documents. An intermediate glyph-based view reveals the structural and textual differences and similarities of a set of finding spots and their corresponding source text fragments. Eventually, the actual fragments of the finding spot can be shown in a side-by-side view with a novel structured wrapping of both the source, as well as the suspicious text. The three different levels of detail are tied together by versatile navigation and selection operations. Reviews with plagiarism experts confirm that this tool can effectively support their workflow and provides a significant improvement over existing static visualizations for assessing and presenting plagiarism cases.
The three main contributions of this research have a lot in common aside from being carefully designed and scientifically grounded solutions to real-world decision problems. The first two visualizations facilitate the decision for a single possibility out of many alternatives, whereas the latter ones deal with text at varying levels of detail. All visual representations are clearly structured based on horizontal and vertical layers contained in a single view and they all employ edges for depicting the most important relationships between attributes, words, or different levels of detail. A detailed analysis considering the context of the established decision-making literature reveals that important steps of common decision models are well-supported by the three visualization systems presented in this thesis.
For the dynamic behavior of lightweight structures like thin shells and membranes exposed to fluid flow the interaction between the two fields is often essential. Computational fluid-structure interaction provides a tool to predict this interaction and complement or eventually replace expensive experiments. Partitioned analyses techniques enjoy great popularity for the numerical simulation of these interactions. This is due to their computational superiority over simultaneous, i.e. fully coupled monolithic approaches, as they allow the independent use of suitable discretization methods and modular analysis software. We use, for the fluid, GLS stabilized finite elements on a moving domain based on the incompressible instationary Navier-Stokes equations, where the formulation guarantees geometric conservation on the deforming domain. The structure is discretized by nonlinear, three-dimensional shell elements.
Commonly used sequential staggered coupling schemes may exhibit instabilities due to the so-called artificial added mass effect. As best remedy to this problem subiterations should be invoked to guarantee kinematic and dynamic continuity across the fluid-structure interface. Since iterative coupling algorithms are computationally very costly, their convergence rate is very decisive for their usability. To ensure and accelerate the convergence of this iteration the updates of the interface position are relaxed. The time dependent, 'optimal' relaxation parameter is determined automatically without any user-input via exploiting a gradient method or applying an Aitken iteration scheme.
This ethnographic study reports on emerging work processes and practices observed in the AEC (Architecture/Engineering/Construction) Global Teamwork program, i.e., what people experience when interacting with and through collaboration technologies, why people practice in the way they do, how the practice fits into the environment and changes the work patterns. It presents the experience of two high-performance typical but extreme AEC teamwork cases adopting and adapting to collaboration technologies and how these technologies in practice impact their work processes. The findings illustrate the importance of collaboration technologies in cross-disciplinary, global teamwork. Observations indicate that high performance teams that use the collaboration technologies effectively exhibit collaboration readiness at an early stage and manage to define a “third way” to meet the demands of the cross-disciplinary, multi cultural and geographically distributed AEC workspace. The observations and implications represent the blueprint for yearly innovations and improvements to the design of the AEC Global Teamwork program.
Aerodynamic Analysis of Slender Vertical Structure and Response Control with Tuned Mass Damper
(2015)
Analysis of vortex induced vibration has gained more interest in practical held of civil engineering. The phenomenon often occurs in long and slender vertical structure like high rise building, tower, chimney or bridge pylon, which resulting in unfavorable responses and might lead to the collapse of the structures. The phenomenon appears when frequency of vortex shedding produced in the wake area of body meet the natural frequency of the structure. Even though this phenomenon does not necessarily generate a divergent amplitude response, the structure still may fail due to fatigue damage.
To reduce the effect of vortex induced vibration, engineers widely use passive vibration response control system. In this case, the thesis studies the effect of tuned mass damper. The objective of this thesis is to simulate the effect of tuned mass damper in reducing unfavorable responses due to vortex induced vibration and initiated by numerical model validation with respect to wind tunnel test report. The reference structure that being used inside the thesis is Stonecutter Bridge, Hongkong.
A numerical solver for computational uid dynamics named VX ow which developed by Morgenthal [6] is utilized for wind and structure simulation. The comparison between numerical model and wind tunnel result shows 10% maximum tip displacement diference in the model of full erection freestanding tower. The tuned mass damper (TMD) model itself built separately in finite element software SOFiSTiK, and the efective damping obtained from this model then applied inside input modal data of VX ow simulation. A single TMD with mass ratio of TMD 0.5% to the mass of first bending frequency, the maximum tip displacement is measured to be average 67% reduced.
Considering construction limitation and robustness of TMD, the effects of multiple TMD inside a structure are also studied. An uncoupled procedure of applying aeroelastic loads obtained from VX
ow inside finite element software SOFiSTiK is also done to observe the optimum distribution and optimum mass ratio of multiple tuned mass damper. The rest of the properties of TMD are calculated with Den Hartog's formula. The results are as follows: peak displacement in the case of multiple TMD that distributed with polynomial spacing achieve 7.8% more reduction performance than
the one that distributed with equal spacing. Optimum mass of tuned mass damper achieved with ratio 1.25% mass of first bending frequency corresponds to across wind direction.
Stonecutters and Sutong Bridge have pushed the world record for main span length of cable-stayed bridges to over 1000m. The design of these bridges, both located in typhoon prone regions, is strongly influenced by wind effects during their erection. Rigorous wind tunnel test programmes have been devised and executed to determine the aerodynamic behaviour of the structures in the most critical erection conditions. Testing was augmented by analytical and numerical analyses to verify the safety of the structures throughout construction and to ensure that no serviceability problems would affect the erection process. This paper outlines the wind properties assumed for the bridge sites, the experimental test programme with some of its results, the dynamic properties of the bridges during free cantilevering erection and the assessment of their aerodynamic performance. Along the way, it discusses the similarities and some revealing differences between the two bridges in terms of their dynamic response to wind action.
The accurate representation of aerodynamic forces is essential for a safe, yet reasonable design of long-span bridges subjected to wind effects. In this paper, a novel extension of the Pseudo-three-dimensional Vortex Particle Method (Pseudo-3D VPM) is presented for Computational Fluid Dynamics (CFD) buffeting analysis of line-like structures. This extension entails an introduction of free-stream turbulent fluctuations, based on the velocity-based turbulence generation. The aerodynamic response of a long-span bridge is obtained by subjecting the 3D dynamic representation of the structure to correlated free-stream turbulence in two-dimensional (2D) fluid planes, which are positioned along the bridge deck. The span-wise correlation of the free-stream turbulence between the 2D fluid planes is established based on Taylor's hypothesis of frozen turbulence. Moreover, the application of the laminar Pseudo-3D VPM is extended to a multimode flutter analysis. Finally, the structural response from the Pseudo-3D flutter and buffeting analyses is verified with the response, computed using the semi-analytical linear unsteady model in the time-domain. Meaningful merits of the turbulent Pseudo-3D VPM with respect to the linear unsteady model are the consideration of the 2D aerodynamic nonlinearity, nonlinear fluid memory, vortex shedding and local non-stationary turbulence effects in the aerodynamic forces. The good agreement of the responses for the two models in the 3D analyses demonstrates the applicability of the Pseudo-3D VPM for aeroelastic analyses of line-like structures under turbulent and laminar free-stream conditions.
In this work, practice-based research is conducted to rethink the understanding of aesthetics, especially in relation to current media art. Granted, we live in times when technologies merge with living organisms, but we also live in times that provide unlimited resources of knowledge and maker tools. I raise the question: In what way does the hybridization of living organisms and non-living technologies affect art audiences in the culture that may be defined as Maker culture? My hypothesis is that active participation of an audience in an artwork is inevitable for experiencing the artwork itself, while also suggesting that the impact of the umwelt changes the perception of an artwork. I emphasize artistic projects that unfold through mutual interaction among diverse peers, including humans, non-human organisms, and machines. In my thesis, I pursue collaborative scenarios that lead to the realization of artistic ideas: (1) the development of ideas by others influenced by me and (2) the materialization of my own ideas influenced by others. By developing the scenarios of collaborative work as an artistic experience, I conclude that the role of an artist in Maker culture is to mediate different types of knowledge and different positions, whereas the role of the audience is to actively engage in the artwork itself. At the same time, aesthetics as experience is triggered by the other, including living and non-living actors. It is intended that the developed methodologies could be further adapted in artistic practices, philosophy, anthropology, and environmental studies.
Wissenschaftliches Kolloquium vom 27. bis 30. Juni 1996 in Weimar an der Bauhaus-Universität zum Thema: ‚Techno-Fiction. Zur Kritik der technologischen Utopien'
Die heutige Situation in der Tragwerksplanung ist durch das kooperative Zusammenwirken einer größeren Anzahl von Fachleuten verschiedener Disziplinen (Architektur, Tragwerksplanung, etc.) in zeitlich befristeten Projektgemeinschaften gekennzeichnet. Bei der Abstimmung der hierdurch bedingten komplexen, dynamischen und vernetzten Planungsprozesse kommt es dabei häufig zu Planungsmängeln und Qualitätseinbußen. Dieser Artikel zeigt auf, wie mit Hilfe der Agententechnologie Lösungsansätze zur Verbesserung der Planungssituation erreicht werden können. Hierzu wird ein Agentenmodell für die vernetzt-kooperative Tragwerksplanung vorgestellt und anhand der Planung einer Fußgängerbogenbrücke anschaulich demonstriert. Das Agentenmodell erfasst (1) die beteiligten Fachplaner und Organisationen, (2) die tragwerksspezifischen Planungsprozesse, (3) die zugehörigen (Teil-)Produktmodelle und (4) die genutzte (Ingenieur-)Software. Hieraus leiten sich die drei Teilmodelle (1) agentenbasiertes Kooperationsmodell, (2) agentenbasierte Produktmodellintegration und (3) Modell zur agentenbasierten Software-Integration ab. Der Fokus des Artikels liegt auf der Darstellung des agentenbasierten Kooperationsmodells.
Aktionsräume in Dresden
(2012)
In vorliegender Studie werden die Aktionsräume von Befragten in Dresden über eine standardisierte Befragung (n=360) untersucht. Die den Aktionsräumen zugrundeliegenden Aktivitäten werden unterschieden in Einkaufen für den täglichen Bedarf, Ausgehen (z.B. in Café, Kneipe, Gaststätte), Erholung im Freien (z.B. spazieren gehen, Nutzung von Grünanlagen) und private Geselligkeit (z.B. Feiern, Besuch von Verwandten/Freunden). Der Aktionsradius wird unterschieden in Wohnviertel, Nachbarviertel und sonstiges weiteres Stadtgebiet. Um aus den vier betrachteten Aktivitäten einen umfassenden Kennwert für den durchschnittlichen Aktionsradius eines Befragten zu bilden, wird ein Modell für den Kennwert eines Aktionsradius entwickelt. Die Studie kommt zu dem Ergebnis, dass das Alter der Befragten einen signifikanten – wenn auch geringen – Einfluss auf den Aktionsradius hat. Das Haushaltsnettoeinkommen hat einen mit Einschränkung signifikanten, ebenfalls geringen Einfluss auf alltägliche Aktivitäten der Befragten.
Im Rahmen des Sonderforschungsbereiches 524 <Werkstoffe und Konstruktionen für die Revitalisierung von Bauwerken 1> ist das primäre Anliegen des Teilprojektes D2 <Bauplanungsrelevantes digitales Gebäudeaufnahme- und Informationssystem> die Entwicklung von Methoden und Techniken zur Aufnahme von Bestandsdaten vor Ort oder durch Auswertung vorhandener Dokumentationen und deren direkte Integration in ein Bauwerksmodell. [15] Das Vorhaben erarbeitet Grundlagen zu Aspekten der fachplanerischen Nutzung und der wissenschaftlichen Auswertungen arbeitsmethodischer Vorgehensweisen in der Bestandsaufnahme unter Einbeziehung softwaretechnischer Methoden. Dabei finden Sachverhalte der Strukturierung, die Herausarbeitung von Systematiken der wesentlichen Informations-/Datenmengen, die Ableitung von Methoden zur zerstörungsfreien Erfassung und die Darstellung planungsrelevanter Gebäudeinformationen in digitalen Systemen Berücksichtigung. Beim Bauaufmaß werden neben traditionellen Methoden und Techniken längst geodätische Verfahren wie die Tachymetrie, die Photogrammetrie und die Handlaserentfernungsmessung einbezogen. In der Praxis des Bestandsaufmaßes repräsentiert gegenwärtig die Tachymetrie, das am häufigsten zur Innen- und Außenaufnahme von Gebäuden eingesetzte geodätische Vermessungsverfahren. [9] [3] Ausgehend von der heutigen Situation in der Bestandsaufnahme wird aufgezeigt, inwieweit es nach dem gegenwärtigen Stand der Technik möglich ist, die in der Geodäsie verwendeten Tachymeter direkt in der Bestandsaufnahme einzusetzen. In einem weiteren Schwerpunkt wird die Konzeption eines rechnergestützten Bauaufnahmesystems basierend auf reflektorlos messenden tachymetrischen Geräten beschrieben. Das Konzept berücksichtigt nicht nur das Bauaufmaß, sondern unterstützt adäquat den gesamten Prozeß der Bauaufnahme – von der Erstbegehung bis hin zur konstruktiven Gliederung. Abschließend werden tendenzielle Möglichkeiten in der Bauaufnahme diskutiert.