Research On Seismic Performance Of PC Frame Structures With Different Prestressing Ratios

Prestressing ratio(PPR) determines the proportion of prestressed tendons and non prestressed reinforcement in prestressed concrete(PC) frame beam, which reflects the prestressing level applied to the members. The value of PPR will directly affect the seismic performance of PC structures. In this paper, the method of theoretical analysis and numerical simulation were adopted respectively to research the seismic performance of PC frame structures, and to evaluate the influence of PPR on PC frame structures. The main work is described as following.(1) A PC frame structure is designed according to the current Chinese designing codes as the archetype structure. Then, the archetype structure is modeled in OpenSees software. Through comparing the modal results(Periods and Modes) with PKPM software, the OpenSees model is verified to describe the modeling process of the archetype structure. A combined nonlinear numerical analysis model of PC frame structure is established in OpenSees software, adopted the numerical model to analyze the pseudo-static test of a single span PC frame. Through comparing the experimental and numerical results to verify the practicability of the numerical model, such as material constitutive model selection, element type input, and prestressing effect simulation.(2) Summarized the factors that ‘strong column & weak beam' is difficult to be realized, and investigated the effect of PPR & crack control level on structural seismic performance of PC frame structure. Analyze the applicability of the method in determining the amount of non-prestressed reinforcement theoretically in prestressed concrete beams designed by current codes. Static elasto-plastic analysis are conducted on four PC frame structures with different PPR. The analytical results show that the amount of non-prestressed reinforcement in prestressed concrete beams designed by current codes is excessive, PC frames are difficult to achieve ‘strong column and weak beam' failure mode under strong earthquakes, reasonable increase of the PPR could improve the structural seismic capacity.(3) Develop the incremental dynamic analysis and vulnerability analysis on three PC frame structures, which taken the maximum inter story drift as the seismic demand parameter, then compared the failure modes of PC frame structures with different PPR. The results show that, increase the PPR reasonably is beneficial to disperse the positions of the structure where energy dissipation and damage occur under the earthquake, reduce the failure probability and enhance the seismic capacity of the structure. Therefore, it is appropriate to increase the limit value of PPR when designing codes revised, and suggestion that the PPR could be increased to 0.80 when designing PC frame is proposed in this paper.