| With the development of prestressing, more and more prestressed concrete structures were extensively used in civil engineering. Compared with reinforced concrete beams, the prestressed ones are more slimmer due to the usage of high strength materials, so it is very important to study their deflection. Many methods on calculation of deflection of prestressed concrete beams have been proposed both at home and abroad, most of which were empirical formulas for approximate engineering calculation. Thus, further study on deflection and stiffness of the prestressed beams is necessary.First, formulas on calculation of deflection specified in both the Chinese Concrete Design Code GB50010-2002 and ACI318-99 were adopted, and then compared calculation results with test results. It is found that calculation results from formulas specified in GB50010-2002 agree with the test results on uncracked prestressed concrete beams to a great extent, and formulas specified in ACI318-99 are more suitable for calculation of those postcracked prestressed concrete beams, but formulas in both codes are not ideal for the calculation of beams which are subjected to loads near the crack ones or ultimate ones. Subsequently, the whole process nonlinear analysis for prestressed concrete beams was carried out by finite element analysis software ANSYS, and results indicated that deflection simulated by ANSYS agreed with test results well except data near the ultimate loads. Error is mainly due to difference between restraints simulated by ANSYS and in experiments, so it's need to search for more rational restraints.According to deficiency of empirical formulas in codes and analysis in ANSYS, the paper combined tests, theories and numerical analysis, took into account influence of geometrical non-linearity and material non-linearity on deflection. The method of calculating deflection and short-term stiffness on prestressed reinforced concrete beams was presented, and then formulas on deflection based on effective inertia method were induced. Compared with test results, it is found that formulas proposed in this paper could simulate tri-linear load-deflection curves to a great extent, but are not ideal for calculation of beams under loads near the crack ones and the yield ones too. Also, those formulas are so complex that they need to be simplified. |
