Papers by Keyword: Numerical Model

Abstract: This paper focuses on the characterization of the behaviour of Concrete Filled Steel Tubular (CFST) columns made with Rubberized Concrete (RuC), and on the development of an accurate numerical model for the simulation of CFST columns under monotonic and cyclic bending. The test campaign involves 18 CFST specimens with different configurations, namely the cross-section slenderness, the concrete strength, the axial load level and the lateral loading type. All CFST members tested exhibited good ductility under monotonic loading. The Eurocode 4 design provisions was verified against the test results and the design capacities of the CFST members were validated to be conservative. A comprehensive 3D Finite Element (FE) model was developed and calibrated based on test results. The FE model proved to be reliable in predicting the bending behaviour of CFST member, in terms of local buckling deformation modes, ultimate capacity and ductility of the CFST columns.

Abstract: The authors participated in the prediction contest for strength of 4m deep concrete slab strip set forth by University Toronto in Canada. They submitted the best prediction among 66 entries from all over the world. Their solution was achieved with a numerical analysis based on nonlinear constitutive model of concrete using fracture mechanics. The shear strength of beam was significantly affected by its large size. After the results of contest were made public the authors performed a study about mesh sensitivity and element type effects, which resulted in assessment of model uncertainty.

Abstract: Most of the monumental structures worldwide and residential structures in developing countries are built in masonry. The studies performed by various researchers prove the vulnerability of masonry structures under various circumstances, especially under earthquakes, so as to necessitate detailed contemplation. In this paper, a numerical model for nonlinear static analysis of unreinforced masonry walls is developed based on a macro-modelling approach. A detailed parametric study is also performed to analyse the effect of wall thickness as well as length on the behaviour of the masonry wall. The present numerical model can be utilized for risk assessment and seismic retrofitting of historical masonry structures.

Abstract: A dam is an artificial barrier constructed across a stream channel to impound water. Analysis of stresses and displacements are inevitable for the structural design and failure analysis of dams. This paper deals with the numerical simulation of structural response of gravity dams, duly considering the foundation-structure interaction. The optimum depth and width of foundation extend to be considered in the numerical model is also studied. A parametric study based on the stiffness of the foundation is also exercised. As an application of the developed model, a case study of Peechi gravity dam is presented. This study proved the importance of consideration of foundation-structure interaction in the structural analysis of dams. The developed numerical model can be further improved for performing seismic analysis of gravity dams, considering the foundation-structure as well as fluid-structure interactions.

Abstract: Vortex pump is a kind of non-clogging pump, which will cause a large amount of vortex during transportation. Four kinds of mathematical model of vortex pump are introduced with continuous improvement. Moreover, the internal flow state, calculation and design method are also presented. In addition, the influent of slurry and structure parameters is introduced. After analyzed above, the design method of vortex pump can be further investigated specific to different concentration, viscosity and particle sizes under different specific speed. The focus of future research is testing internal flow by the advanced technology, building up a new flow model and proposing complete and practical calculation method.

Abstract: Many road and highway have been constructed over the expansive soil in Java island without proper soil improvement for the subgrade. The behavior of the column on the expansive soil needs for study numerically and large scale. In this study, a numerical analysis is performed to study the effect of swelling on the deformation of the soil stabilized column supported flexible pavement. The main focus of the research is to obtain the deformation due to swelling and vehicle loading. The methodology including comparison the differential settlement of the soil stabilized column supported flexible pavement and unsupported flexible pavement as control model. The numerical analysis was modeled using finite element method. The simulations result that the column installation to support flexible pavement reduced the heaving and differential settlement of the pavement effectively. In case the overlay was performed for rehabilitation and maintenance of the pavement, the mini-columns can be installed before the overlay works. However, the conclusions of the study were limited to the result of numerical modeling that depended on the applied material model and volumetric swelling.

Abstract: The red blood cell (RBC) membrane consists of a lipid bilayer and spectrin-based cytoskeleton, which enclose haemoglobin-rich fluid. Numerical models of RBCs typically integrate the two membrane components into a single layer, preventing investigation of bilayer-cytoskeleton interaction. To address this constraint, a new RBC model which considers the bilayer and cytoskeleton separately is developed using the discrete element method (DEM). This is completed in 2D as a proof-of-concept, with an extension to 3D planned in the future. Resting RBC morphology predicted by the two-layer model is compared to an equivalent and well-established composite (one-layer) model with excellent agreement for critical cell dimensions. A parametric study is performed where area reduction ratio and spring constants are varied. It is found that predicted resting geometry is relatively insensitive to changes in spring stiffness, but a shape variation is observed for reduction ratio changes as expected.

Abstract: The paper deals with evaluation of experimental data collected during the Oparno arch bridge construction and with subsequent analysis of the construction process and long-term behavior with regard to rheological properties of concrete. The Oparno valley bridge is composed of two separate concrete arch structures with spans of 135 metres (this is currently the second longest span of concrete arch bridge in the Czech Republic). It was built using cantilever casting technology with temporary cable-stays and auxiliary pylons. The data recorded for this study include detailed geodetic measurement of the bridge structure during construction, along with measured strains and temperatures in the arches. Most of the data was measured during the bridge construction in 2008 and 2009. Data significant for long term behavior of structure are still being collected. Verification of different concrete material models and their suitability for design of arch bridges built by free cantilevering will be a main result of the analysis. On the basis of a detailed comparison of numerical results and measured deflections, strains and temperatures, it is possible to quantify the impact of rheological properties of the material (or their individual input parameters) on the resulting structural behavior. Unlike previous research, the examined structure is made of reinforced concrete (not prestressed) and consists of compact solid section and in the final state it is mainly in compression.

Abstract: At the beginning of this year prof. Z. P. Bažant and his team published a new numerical model for predicting creep and shrinkage in concrete structures. Model, named B4, is conceptually based on the previous version B3. While early prediction models were based mostly on classical concrete composition, the new model allows for observation the variability of modern concrete compositions, i.e. the effects of admixtures, various aggregate types and increasing concrete strength. The model also captures the effects of environment temperature, multi-decade prediction and autogenous shrinkage. This is important for concretes that are produced in Czech Republic and have higher, but not high strength (about 50 MPa). The model also allows to determine internal parameters according to experimental measurements on laboratory specimens or structural members. Therefore it is possible to refine the prediction of the behavior of structures made of this concrete in the long time periods. However, the increased number of input parameters leads to a higher complexity and it is necessary to have computational tools for practical model application. To provide the model to wider engineering community open structure computational program (in MATLAB environment) was created. Software is freely available for download on the internet. Description of the innovations of the model B4 and demonstration of its relatively simple applications using newly developed software products is a subject of this paper.

Abstract: This paper shows common research activities of the Chemical Engineering team from the Institute of Materials Chemistry of the Faculty of Chemistry in Brno, University of Technology, Czech Republic. The paper is focused on application of simplified mathematical model on the experimental data obtained through the carbon dioxide scrubbing in to the deionized water in the experimental gas scrubber. The MS Excel’s (2007) Solver was used for computing simplified mathematical model of gas absorption under unsteady state. The CO₂ used for the experiment was of the food quality. 24.675 liters of the deionized water was used as water quantity batch. Absorbed CO₂ was detected with the gas electrode.