29-09-2012, 04:25 PM
Software for Finite Element Analysis of Prestressed Concrete Structures
Software for Finite Element.docx (Size: 234.01 KB / Downloads: 50)
INTRODUCTION
Prestressed concrete sections are economical compared to reinforced concrete and hence, have a wide use in bridges, buildings and other structures. Reliability of these structures mainly depends on the performance of the prestressing force over a design period of these structures. Prediction of the response of prestressed concrete structures requires three-dimensional structural idealization and true modelling of nonlinear behavior of concrete, reinforcing steel and prestressing tendons.
All these effects have been considered for the analysis of the prestressed concrete structures. Based on the above, computer software has been developed for the three-dimensional finite element analysis of prestressed concrete structures. Validation of the software has been done by analyzing experimental as well as analytical studies, reported in the literature. The results of these validation studies have been compared with the reported results in the literature and found to be in a good agreement.
Finite Element Method
Finite element method is accepted as the most powerful technique for the numerical solution of a variety of engineering problems and hence, the same has been used to model and analyze the nonlinear behavior of prestressed concrete structures.
Prestressing Tendon
A discrete formulation of prestressing tendons using 20-noded solid-element has been developed. The influence of prestressing tendon on the concrete is modelled by distributed normal and tangential load acting along the tendon length, Figure 3 and concentrated point load at anchorages. Prestressing tendon is modelled using one-dimensional curved element embedded in the solid-element. Geometry of the tendon segment, lying inside the solid-element, is defined by three nodal points, Figure 4. Prestressing tendon may be located anywhere in the depth of the section. Full strain compatibility is assumed between concrete and prestressing tendon. The stiffness of the tendon is added to the stiffness of the solid element to get the total stiffness.
Modelling of Loads
Finite element formulations for application of loads such as concentrated nodal loads, concentrated point loads, self–weight, pressure over a surface and prestress load on the structures have been developed and implemented into finite element code.
Constitutive Modelling
Concrete is highly nonlinear material and its nonlinear response is mainly due to progressive cracking and nonlinear deformations. Triaxial tests performed on concrete shows that concrete is pressure sensitive material and under high hydrostatic compression, concrete flows like metals in a limited manner. The compressive, tensile and flexural strengths of concrete depend upon the rate of loading.
Conclusion
Computer software has been developed for three-dimensional finite element analysis of prestressed concrete structures taking into account nonlinear material properties and effects of creep and shrinkage. Validation of the software has been done with the help of available literature. A very good match between the experimental and numerical results is found.