Study On Seismic Performance Of Unbonded Partly Prestressed Reinforced Concrete Piers

Bridges are one of the most important parts of our country’s traffic network. Earthquakes with high energy break out frequently around the world, which guarantees the extreme importance to explore bridge seismic performance. After earthquake, bridge is the key part to assure the way through to save people’s life. Generally speaking, bridge piers are the most fragile part of the whole structure, and loses caused by its failure may be inestimable.Recently, seismic technology has a rapid expansion, which can be attributed to the fair amount of maga-earthquakes around the world. Many of the important seismic codes around the world have already applied ductile design, and performance-based seismic design has been one of the research hotspots and development trend, GB50011-2010Code for seismic design of buildings which has been published recently, also adds contents of performance-based seismic design.Residual displacement after earthquake is the key fator to determine bridge’s repairability. The issue of buliding a re-centering structure to control the residual displacement should be well developed. Partially prestressed reinforced concrete piers (PRC piers) have the marits to lightening structural deadload, controlling crack and can gain remarkable stiffness after yield, which makes it one of the research hotspots in pier seismic research. In China, test and analytical research for PRC piers are both in shortage, an effective method is needed to evaluate the effect of prestressing ratio. For this reason, sponsored by National Natural Science Foundation (50978042), a pseudo-static test has been designed and performed to evaluate the effects of prestressed degree, prestressing force and position of prestressing strands. The following issues are accomplished:(1) Based on literature review, the factors influencing the seismic performance of PRC piers have been summarized from five aspects, which are:prestressed compression ratio, amounts of prestressing strands, amounts of reinforcing steel, prestressed degree and position of prestressing strands;(2) The pseudo-static test of three factors (prestressing ratio, prestressed compression ratio, position of prestressing strands) has been designed and performed;(3) An evaluation has been done based on test results in terms of hysteretic curve, skeleton curve, ductile performance, energy dissipation, residual displacement, presressed tendon stress, stiffness, cracking control; (4) Based on finite analytical software OpenSees, a beamWithHinges fiber element is built to simulate the PRC piers of the test. The accuracy of the model is also been verified and evaluated.