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- 2015 (51) (remove)
Polymer modification of mortar and concrete is a widely used technique in order to improve their durability properties. Hitherto, the main application fields of such materials are repair and restoration of buildings. However, due to the constant increment of service life requirements and the cost efficiency, polymer modified concrete (PCC) is also used for construction purposes. Therefore, there is a demand for studying the mechanical properties of PCC and entitative differences compared to conventional concrete (CC). It is significant to investigate whether all the assumed hypotheses and existing analytical formulations about CC are also valid for PCC. In the present study, analytical models available in the literature are evaluated. These models are used for estimating mechanical properties of concrete. The investigated property in this study is the modulus of elasticity, which is estimated with respect to the value of compressive strength. One existing database was extended and adapted for polymer-modified concrete mixtures along with their experimentally measured mechanical properties. Based on the indexed data a comparison between model predictions and experiments was conducted by calculation of forecast errors.
What is nowadays called (classic) Clifford analysis consists in the establishment of a function theory for functions belonging to the kernel of the Dirac operator. While such functions can very well describe problems of a particle with internal SU(2)-symmetries, higher order symmetries are beyond this theory. Although many modifications (such as Yang-Mills theory) were suggested over the years they could not address the principal problem, the need of a n-fold factorization of the d’Alembert operator. In this paper we present the basic tools of a fractional function theory in higher dimensions, for the transport operator (alpha = 1/2 ), by means of a fractional correspondence to the Weyl relations via fractional Riemann-Liouville derivatives. A Fischer decomposition, fractional Euler and Gamma operators, monogenic projection, and basic fractional homogeneous powers are constructed.
Recently there has been a surge of interest in PDEs involving fractional derivatives in different fields of engineering. In this extended abstract we present some of the results developedin [3]. We compute the fundamental solution for the three-parameter fractional Laplace operator Δ by transforming the eigenfunction equation into an integral equation and applying the method of separation of variables. The obtained solutions are expressed in terms of Mittag-Leffer functions. For more details we refer the interested reader to [3] where it is also presented an operational approach based on the two Laplace transform.
This article presents the Rigid Finite Element Method in the calculation of reinforced concrete beam deflection with cracks. Initially, this method was used in the shipbuilding industry. Later, it was adapted in the homogeneous calculations of the bar structures. In this method, rigid mass discs serve as an element model. In the flat layout, three generalized coordinates (two translational and one rotational) correspond to each disc. These discs are connected by elastic ties. The genuine idea is to take into account a discrete crack in the Rigid Finite Element Method. It consists in the suitable reduction of the rigidity in rotational ties located in the spots, where cracks occurred. The susceptibility of this tie results from the flexural deformability of the element and the occurrence of the crack. As part of the numerical analyses, the influence of cracks on the total deflection of beams was determined. Furthermore, the results of the calculations were compared to the results of the experiment. Overestimations of the calculated deflections against the measured deflections were found. The article specifies the size of the overestimation and describes its causes.
The sizing of simple resonators like guitar strings or laser mirrors is directly connected to the wavelength and represents no complex optimisation problem. This is not the case with liquid-filled acoustic resonators of non-trivial geometries, where several masses and stiffnesses of the structure and the fluid have to fit together. This creates a scenario of many competing and interacting resonances varying in relative strength and frequency when design parameters change. Hence, the resonator design involves a parameter-tuning problem with many local optima. As its solution evolutionary algorithms (EA) coupled to a forced-harmonic FE simulation are presented. A new hybrid EA is proposed and compared to two state-of-theart EAs based on selected test problems. The motivating background is the search for better resonators suitable for sonofusion experiments where extreme states of matter are sought in collapsing cavitation bubbles.
The p-Laplace equation is a nonlinear generalization of the Laplace equation. This generalization is often used as a model problem for special types of nonlinearities. The p-Laplace equation can be seen as a bridge between very general nonlinear equations and the linear Laplace equation. The aim of this paper is to solve the p-Laplace equation for 2 < p < 3 and to find strong solutions. The idea is to apply a hypercomplex integral operator and spatial function theoretic methods to transform the p-Laplace equation into the p-Dirac equation. This equation will be solved iteratively by using a fixed point theorem.
Over the last decade, the technology of constructing buildings has been dramatically developed especially with the huge growth of CAD tools that help in modeling buildings, bridges, roads and other construction objects. Often quality control and size accuracy in the factory or on construction site are based on manual measurements of discrete points. These measured points of the realized object or a part of it will be compared with the points of the corresponding CAD model to see whether and where the construction element fits into the respective CAD model. This process is very complicated and difficult even when using modern measuring technology. This is due to the complicated shape of the components, the large amount of manually detected measured data and the high cost of manual processing of measured values. However, by using a modern 3D scanner one gets information of the whole constructed object and one can make a complete comparison against the CAD model. It gives an idea about quality of objects on the whole. In this paper, we present a case study of controlling the quality of measurement during the constructing phase of a steel bridge by using 3D point cloud technology. Preliminary results show that an early detection of mismatching between real element and CAD model could save a lot of time, efforts and obviously expenses.
The stress state of a piecewise-homogeneous elastic body, which has a semi-infinite crack along the interface, under in-plane and antiplane loads is considered. One of the crack edges is reinforced by a rigid patch plate on a finite interval adjacent to the crack tip. The crack edges are loaded with specified stresses. The body is stretched at infinity by specified stresses. External forces with a given principal vector and moment act on the patch plate. The problem reduces to a Riemann-Hilbert boundary-value matrix problem with a piecewise-constant coefficient for two complex potentials in the plane case and for one in the antiplane case. The complex potentials are found explicitly using a Gaussian hypergeometric function. The stress state of the body close to the ends of the patch plate, one of which is also simultaneously the crack tip, is investigated. Stress intensity factors near the singular points are determined.
Steel profiles with slender cross-sections are characterized by their high susceptibility to instability phenomena, especially local buckling, which are intensified under fire conditions. This work presents a study on numerical modelling of the behaviour of steel structural elements in case of fire with slender cross-sections. To accurately carry out these analyses it is necessary to take into account those local instability modes, which normally is only possible with shell finite elements. However, aiming at the development of more expeditious methods, particularly important for analysing complete structures in case of fire, recent studies have proposed the use of beam finite elements considering the presence of local buckling through the implementation of a new effective steel constitutive law. The objective of this work is to develop a study to validate this methodology using the program SAFIR. Comparisons are made between the results obtained applying the referred new methodology and finite element analyses using shell elements. The studies were made to laterally restrained beams, unrestrained beams, axially compressed columns and columns subjected to bending plus compression.
In photogrammetry and computer vision the trifocal tensor is used to describe the geometric relation between projections of points in three views. In this paper we analyze the stability and accuracy of the metric trifocal tensor for calibrated cameras. Since a minimal parameterization of the metric trifocal tensor is challenging, the additional constraints of the interior orientation are applied to the well-known projective 6-point and 7-point algorithms for three images. The experimental results show that the linear 7-point algorithm fails for some noise-free degenerated cases, whereas the minimal 6-point algorithm seems to be competitive even with realistic noise.
The Laguerre polynomials appear naturally in many branches of pure and applied mathematics and mathematical physics. Debnath introduced the Laguerre transform and derived some of its properties. He also discussed the applications in study of heat conduction and to the oscillations of a very long and heavy chain with variable tension. An explicit boundedness for some class of Laguerre integral transforms will be present.
SELECTION AND SCALING OF GROUND MOTION RECORDS FOR SEISMIC ANALYSIS USING AN OPTIMIZATION ALGORITHM
(2015)
The nonlinear time history analysis and seismic performance based methods require a set of scaled ground motions. The conventional procedure of ground motion selection is based on matching the motion properties, e.g. magnitude, amplitude, fault distance, and fault mechanism. The seismic target spectrum is only used in the scaling process following the random selection process. Therefore, the aim of the paper is to present a procedure to select a sets of ground motions from a built database of ground motions. The selection procedure is based on running an optimization problem using Dijkstra’s algorithm to match the selected set of ground motions to a target response spectrum. The selection and scaling procedure of optimized sets of ground motions is presented by examining the analyses of nonlinear single degree of freedom systems.
Modern distributed engineering applications are based on complex systems consisting of various subsystems that are connected through the Internet. Communication and collaboration within an entire system requires reliable and efficient data exchange between the subsystems. Middleware developed within the web evolution during the past years provides reliable and efficient data exchange for web applications, which can be adopted for solving the data exchange problems in distributed engineering applications. This paper presents a generic approach for reliable and efficient data exchange between engineering devices using existing middleware known from web applications. Different existing middleware is examined with respect to the suitability in engineering applications. In this paper, a suitable middleware is shown and a prototype implementation simulating distributed wind farm control is presented and validated using several performance measurements.
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).
Restelo Neighbourhood: Expanding the Capital of the Empire with the First Portuguese Urban Planner
(2015)
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).
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).
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).
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).
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).
Granite on the Ground: Former Nazi Party Rally Grounds, Nuremberg/Germany. A brief introduction
(2015)
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).