Finite Element Modeling of Post-Tensioned Two-Way Concrete Slabs under Flexural Loading

Post-Tensioned (PT) method is a widely used technique to prevent cracking and to minimize the deflection which is resulted by loads. In this method, stress is applied after concrete placing and reach adequate hardening and strength. This paper investigates the structural behaviour of PT two-way concrete slabs. The main objective of this study involves a detailed flexural behavior analytical investigation of PT concrete two-way slab with the different bonded tendon layout. This will be achieved by non-linear Finite Element (FE) analysis programs method, to choose the most effective and optimum position of tendon layout with different number of tendons and applied load on the concrete two-way slab. A parametric study was conducted to investigate the effect of tendons layout on the overall behavior of post-tensioned two-way concrete slab. The result obtained from finite element analysis showed that the failure load in PT in both directions increased about 89 % as compared with slab PT in one direction

Finite Element Analysis and Optimization of Steel Girders with External Prestressing

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

Comparative Response Assessment of Steel Frames With Different Bracing Systems Under Seismic Effect

The field of earthquake engineering and seismology is of a great importance to structural engineers around the world. Choosing an appropriate lateral force resisting system has a significant effect on performance of the steel structure. The paper presents a comparison of the seismic response of steel frames by using different types of bracing systems. The bracing systems are X-braced frames, V braced frames, inverted V braced frames, Knee braced frames and zipper braced frames. The steel frames are modeled and analyzed in four different height levels. Nonlinear static and dynamic analyses were performed. The frames consist of three bays and steel braces were inserted in the middle bay of each frame. The structural responses of frames are studied in terms of capacity curve, drift ratio, global damage index, base shear, storey displacements, roof displacement time history and plastification. The results showed a good improvement in the seismic resistance of frames with the incorporation of bracing. The results revealed that the bracing elements were very effective in diminishing drifts since the reduction of inter-storey drifts with respect to unbraced frames were on the average 58%. Also steel braces considerably reduced the global damage index