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- 2014 (48) (remove)
The increasing success of BIM (Building Information Model) and the emergence of its implementation in 3D construction models have paved a way for improving scheduling process. The recent research on application of BIM in scheduling has focused on quantity take-off, duration estimation for individual trades, schedule visualization, and clash detection.
Several experiments indicated that the lack of detailed planning causes about 30% non-productive time and stacking of trades. However, detailed planning still has not been implemented in practice despite receiving a lot of interest from researchers. The reason is associated with the huge amount and complexity of input data. In order to create a detailed planning, it is time consuming to manually decompose activities, collect and calculate the detailed information in relevant. Moreover, the coordination of detailed activities requires much effort for dealing with their complex constraints.
This dissertation aims to support the generation of detailed schedules from a rough schedule. It proposes a model for automated detailing of 4D schedules by integrating BIM, simulation and Pareto-based optimization.
Strain measurement is important in mechanical testing. A wide variety of techniques exists for measuring strain in the tensile test; namely the strain gauge, extensometer, stress and strain determined by machine crosshead motion, Geometric Moire technique, optical strain measurement techniques and others. Each technique has its own advantages and disadvantages. The purpose of this study is to quantitatively compare the strain measurement techniques. To carry out the tensile test experiments for S 235, sixty samples were cut from the web of the I-profile in longitudinal and transverse directions in four different dimensions. The geometry of samples are analysed by 3D scanner and vernier caliper. In addition, the strain values were determined by using strain gauge, extensometer and machine crosshead motion. Three techniques of strain measurement are compared in quantitative manner based on the calculation of mechanical properties (modulus of elasticity, yield strength, tensile strength, percentage elongation at maximum force) of structural steel. A statistical information was used for evaluating the results. It is seen that the extensometer and strain gauge provided reliable data, however the extensometer offers several advantages over the strain gauge and crosshead motion for testing structural steel in tension. Furthermore, estimation of measurement uncertainty is presented for the basic material parameters extracted through strain measurement.
The focus of the thesis is to process measurements acquired from a continuous
monitoring system at a railway bridge. Temperature, strain and ambient vibration
records are analysed and two main directions of investigation are pursued.
The first and the most demanding task is to develop processing routines able to extract modal parameters from ambient vibration measurements. For this purpose, reliable experimental models are achieved on the basis of a stochastic system identification(SSI) procedure. A fully automated algorithm based on a three-stage clustering is implemented to perform a modal parameter estimation for every single measurement. After selecting a baseline of modal parameters, the evolution of eigenfrequencies is
studied and correlated to environmental and operational factors.
The second aspect deals with the structural response to passing trains. Corresponding
triggered records of strain and temperature are processed and their assessment is
accomplished using the average strains induced by each train as the reference parameter.
Three influences due to speed, temperature and loads are distinguished and treated individually. An attempt to estimate the maximum response variation due to each factor is also carried out.
Analyse von Terminplänen
(2014)
Das Bachelorprojekt „Analyse von Terminplänen“ beschäftigt sich mit der Analyse der Abhängigkeiten zwischen den unterschiedlichen Vorgängen des Bauablaufs. Die Problematik in der Terminplanerstellung liegt darin, dass ein Terminplan nicht alle Hintergrundinformationen abbildet und es daher zu Projektverzögerungen und Absprachefehlern kommen kann. Dieses Bachelorprojekt macht Gebrauch von bereits aufbereiteten Informationen zur genannten Problematik in Form eines vorangegangen Bachelorprojekts und eines Masterprojekts, sowie einer Umfrage des Instituts für Bauwirtschaft der Universität Kassel.
In diesem Projekt werden 50 neue und 100 bereits existierende Terminpläne von diversen Unternehmen aus ganz Deutschland analysiert und ausgewertet. Die Analyse der Terminpläne basiert auf geführten Experteninterviews. Das Interview berücksichtigt Faktoren wie zum Beispiel Darstellungsformen, Detaillierungsgrade, Abhängigkeiten, Vorgangsdauern oder Planungsgrundlagen. Durch die Befragung von möglichst vielen Firmen konnte festgestellt werden, dass jeder Terminplanentwickler eine Vorgehensweise entwickelt, nach welcher er arbeitet. Außerdem ist in den Gesprächen deutlich geworden, dass das Theorie- Praxis-Gefälle sehr groß ist. Das heißt, dass theoretische Modelle aus der Ausbildung an beispielsweise Hochschulen, in der Praxis heutzutage wenig angewandt werden.
Nach der Analyse der Terminpläne und Auswertung der Interviews, werden die Daten in eine vom vorangehenden Masterprojekt erstellte Excel-Tabelle eingepflegt. Die vorhandenen Informationen werden dann anhand verschiedenster Diagramme verglichen und ausgewertet.
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.
We apply keyquery-based taxonomy composition to compute a classification system for the CORE dataset, a shared crawl of about 850,000 scientific papers. Keyquery-based taxonomy composition can be understood as a two-phase hierarchical document clustering technique that utilizes search queries as cluster labels: In a first phase, the document collection is indexed by a reference search engine, and the documents are tagged with the search queries they are relevant—for their so-called keyqueries. In a second phase, a hierarchical clustering is formed from the keyqueries within an iterative process. We use the explicit topic model ESA as document retrieval model in order to index the CORE dataset in the reference search engine. Under the ESA retrieval model, documents are represented as vectors of similarities to Wikipedia articles; a methodology proven to be advantageous for text categorization tasks. Our paper presents the generated taxonomy and reports on quantitative properties such as document coverage and processing requirements.
A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage
(2014)
Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES) provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM) modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared.