Study On Long-Term Performance Of Self-Centering Prestressed Concrete Frame With Web Friction Devices

Precast reinforced concrete frames have attracted much attention and got applied due to their notable advantages, such as fast manufacture, easy field construction, high quality of structural component and saving on formwork, etc. However, traditional precast reinforced concrete frames have low seismic reliability in the beam-column connections, and may generate large residual deformation in earthquakes, resulting in difficulty in post-earthquake retrofits. Therefore, the application of traditional precast reinforced concrete frames is restricted in seismic zones. Considering this situation, a novel self-centering prestressed concrete (SCPC) beam-column connection with web friction devices is proposed, so as to realize the self-centering after earthquake and to obtain controllable energy dissipation capacity. However, there is no study about the long-term performance of SCPC, such as creeping, loss of prestressing force and their influence on seismic fragility. With regard to the new aseismic structure, investigation is made including the long-term performance tests on SCPC frames, their seismic vulnerability etc. The main work and findings of this study are as follows:(1) The configuration and main mechanical properties of SCPC frame connections are introduced. Comparative tests were conducted on the SCPC frame with fixed column ends and the monolithic reinforced concrete frame, based on this, the numerical simulation method is investigated by using the DIANA, and good agreement is observed between the numerical simulation and the test results. A reliable numerical model is therefore obtained for the following seismic reliability analyses of the SCPC frames.(2) Experimental study about the long-term performance and numerical simulation of SCPC were carried out. This experiment was launched mainly as an observation experiment of single bay frame, including displacement observation of important points and the prestress loss, etc. This test lasted more than one year, form those data, we can analysis the rule of the development of shrinkage and creep of SCPC, as well as the prestress loss. On the base of verifying the rationality of short-term behavior, to describe the long-term performance of mechanical properties of SCPC, CEB-FIP90 model, shrinkage and creep model, stress relaxation model were inset in DIANA as well as considering parameters such as reinforcement ratio. Through the analysis of the numerical simulation and the experimental data, results approved that the numerical simulation was reliable.(3) Time-dependent characteristic of SCPC was investigated.20 seismic records on hard soil site of the far field were selected in the study, through analysis method IDA, seismic fragility and self-centering capability was studied in three different performance level (IO, LS, CP) by comparing interlayer displacement and residual deformation. Based on this, analysis of IDA was calculated at different time point finally the characteristics of change of seismic fragility with the development of the time were researched.The above study provides references to the seismic fragility analysis and time-invariance characteristics of the SCPC frames.