Optimization is a process through which the best possible values of design variables are achieved under the given of constraints and in accordance to a selected optimization objective function. Steel I-girders have been used widely in different fields, which are generally fabricated by connecting two plate flanges, a flat web and a series of longitudinal or transverse stiffeners together. The use of steel girder with external prestressing has been used in many countries as a means of strengthening bridges. The purpose of this paper is to develop a finite element model for the optimization of a steel girder with external prestressing. The ANSYS finite element software package was used to find the optimum cross section dimension for the steel girder. Two objective functions are considered in this study there are optimization of the strain energy and total volume of the girder. The design variables are the width of top flange, the thickness of top flange, the width of bottom flange, the thickness of bottom flange, the height of the web, the width of the web and area of prestressing tendons. Two type of steel girder are considered there are steel girder without prestressing and steel girder with prestressing.The results for volume minimization shows that the optimum cross section for steel girder with prestressing smaller than for steel girder without prestressing.
The aim of this research is to study the experimental effect of the number of cells on the structural behaviour of reinforced concrete box girder. Three simply supported box girder specimens with different numbers of cells were cast by using self-compacting concrete and experimentally tested under four-point load, the first reference specimen is with one cell, the second specimen is with two cells and the last specimen is with four cells. The testing results show that the ultimate load in the two-cell and four-cell specimens is higher compared with the one-cell specimen by (20.1% and 23.3%) respectively. Increasing the number of cells decrease the cracks width and increase the number of cracks, all the specimens failed with diagonal shear.
3D explicit technique based on finite element analysis is usually applied for solving the nonlinear problems in metal forming process such as wire drawing. The mass scaling percentage that related with stable time increment has substantial influence for attaining the optimum simulation results. In this article, the drawing process of A304 stainless wire utilizing analytical and numerical approach without mass scaling was developed to estimate and validate the obtained drawing stresses using different reduction of area. Then, 3D explicit models based on finite element analysis was run using various mass scaling at the low and high reduction of area 12 and 27% for displaying the analysis time, equivalent plastic strain (PEEQ), and drawing stress. The results exposed that the appropriate increase of mass percentage corresponding to the target time increment can be selected for reducing the time of wire drawing analysis to 53 and 50% at reduction of area 12 and 27% respectively. Although the PEEQ and drawing stress had little increase when the mass percentage raises however, it should be taken into consideration through the design of the wire drawing process. Therefore; the mass scaling value must be carefully adopted.
Shape Memory Alloys (SMA) is type of smart materials that have ability to undergo large deformation and return back to their undeformed shape through heating (shape memory effect) or removal of load (superelastic effect). This unique ability is useful to enhance behavior of structure and seismic resistance. In this paper, superelasticity (SE) effect of NiTi alloys is used to improve the structural characteristics of steel building. The finite element analysis of steel building is done using ABAQUS v.2017. In order to compare the structural behavior of the steel building equipped with Shape Memory Alloy bars at beam-column connection, three steel building was modeled with a different combination of high strength steel bars and SMA bars. The steel building was checked for time history analysis by using Vrancea 1977 earthquake data. In order to estimate the recentring ability, residual of roof displacement and energy dissipation. The steel building equipped with SMA bars shows 82.7%, 152.72% recovery in residual roof displacement for steel building equipped with 50% SMA bars and 50% HS steel bars and steel building equipped with 100% SMA bars respectively, and moderate energy dissipation. In general, the frame equipped with 50% superelastic SMA bars and 50% HS steel bars provided better seismic performance.
A delicate analysis of the natural frequencies and mode shapes of a cable stayed bridge is essential to the solution of its dynamic responses due to seismic, wind and traffic loads. In this paper, a bridge with geometry comparable to the Quincy Bayview Bridge was modelled in order to explore the significance of the three dimensional and free vibration analysis. This paper provides a detail of the bridge and the equivalent cross section of the three-dimensional finite element model implicating cables, the bridge deck and pylons as well as the boundary conditions and free vibration analysis by Ansys15.0. The bridge was analyzed to free vibration to obtaine the natural frequency and mode shape. result of this paper present the natural frequencies and mode shapes of the bridge. The method of modelling cables is also studied. It is found that modelling cables as multi beam elements provides better results than using the traditional (and simpler) method of modeling them as single tensile elements.
In this study the shear behavior of reinforced concrete wide beams was experimentally investigated the experimental program consisted of four wide beams of 30 MPa of concrete Compressive strength tested with a shear span-depth ratio (a / d) of 2.77. One of the tested wide beams Design according to the ACI code for maximum spacing of shear reinforcement normal beam (d/2), and the other three specimens designed for spacing (0.75 d,0.81 d, 1.0 d) Respectively. The flexure failure mode was secured to allow for shear failure mode for all specimens. The main parameters covered during this study were the effect of spacing shear reinforcement on shear capacity of the wide beams tested. The study showed that there is no significant effect of divergence on shear strength. The decrease of shear capacity ranged from 1.5 % to 8.85 % For the range of beams tested as compared to the control beam.
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