نوع مقاله : پژوهشی
دانشکدهی مهندسی عمران، دانشگاه صنعتی شریف
عنوان مقاله [English]
Researchers have always paid great attention to safe and economical design and, therefore, different codes in different areas have been formed. The ACI 318-2011 code insists that two-way post-tensioned slabs shall be classified as class U (without cracking), which means the section must be uncracked in both service and transient conditions (code reference 18.3.3). In addition, two-way post-tensioned slabs must be post-tensioned in both directions for 100% of the load, wich means that one-way behavior for this type of slab is assumed. In this study, two-way post-tensioned slabs with various spans under different loadings have been designed, based on the ACI code. Then, using the Lee-Fenves isotropic damage plasticity model for concrete, the numerical simulation of post-tensioned slabs was performed through the finite element method. The isotropic damage plasticity used a yield criterion that matches the experimental data for both elastic and plastic parts of the stress-strain curves of concrete. The onset and propagation of cracking can be evaluated by simple postprocessing of the finite element plasticity solution. The accuracy of the model was checked by the data provided by previous researchers which indicates simulation was precise. The linear elastic-perfectly plastic stress strain relation was used for steel using the Von-mises yield criterion, while the tendons were simulated by bilinear stress strain curve and Von-mises yield criterion. By using nonlinear finite element software (Abaqus) and the above - mentioned yield criterion, several slabs are studied. Numerical simulation shows that some laws of the ACI code are not satisfied in some cases, including cracked slabs in both service and transient conditions. In addition, over post-tensioning of slabs results in negative deflection and non-economical design. At the end some suggestions for better designs are presented.