Research On Seismic Performance Of Reinforced Concrete Bridge Piers Under Corrosive Environment

Earthquakes are natural disaster which threat to human andarchitectural structures suddenly. Many Earthquakes happened in the wordindicate that bridge pier is the most vulnerable to damage as a maincomponents in bridge structure system. The destruction of the reinforcedconcrete bridge piers and that the collapse phenomenon caused by bridgedamage has become the main feature of the modern bridge damages.As amain component supporting bridge superstructure, bridge piers not onlywithstand the upper dead load, vehicle dynamic load and earthquakes,storms and other unexpected loads, but also subject to environmentaleffects, such as atmospheric environment of concrete carbonation,freeze-thaw cycles in cold northern regions, oceans environment caused byhigh concentrations of chloride corrosion of reinforcing steel and the wetand dry cycle of splash zones. So there must be damage in the reality of thepiers in the normal state. Due to damage caused by lack of durability oftenleads to the degradation in carrying capacity of pier and the ability to resistearthquakes or other natural disasters declined. However, whether thedamaged piers can withstand seismic loads in service has importantsignificance on the security of the entire bridge. To some extent, it is moreimportant to have research on seismic performance of damaged RCstructure than new piers.In this paper, according to the characteristics of a bridge pier, the pieris simplified for artifact.The seismic behavior of pier is studied byapplying the constant axial compression and horizontal load. The seismic performance of pier is reflected by hysteretic behavior, cracks and failuremodes when loaded.Compared with experimental result, the main work ofthis paper is using numerical simulation method by finite element softwareOpen Sees and DIANA form which the fiber model and two-dimensionalplane stress element model are build respectively.Also different methods of reinforcement corrosion were considered toanalyze how the corrosion was affected on seismic performance byhysteresis curves, skeleton curves, energy dissipation capacity, ductility,stiffness degradation, stiffness degradation. The study in this paper providereliable guidance on assessment and design after earthquake.The main contents of this article includes the following sections:(1) The fiber plastic hinge model was used in Open Sees software,concentrated on selecting a reasonable steel and concrete constitutivemodel. No corrosion pier was simulated to verify the rationality of finiteelement model. Also Consider the experimental three corrosive reinforcedconcrete pier was simulated to verify the reasonableness of corrosionconstitutive model. To test the corrosion rate on seismic performance,considering12%,16%,20%,24%,28%of different corrosion rate onconcrete pier. When corrosion rate is more than16%, it had a greaterinfluence on the pier.(2) The experiment was extended to consider other factors in additionto high corrosion. Such as the impact of the change of longitudinalreinforcement ratio, shear span ratio, stirrup ratio and other factors on thehysteresis curves, skeleton curves, ductility, yield strength, ultimatestrength, etc. Simulation results show that the ductility of pier increasedobviously with strength of concrete, the longitudinal reinforcement ratio,the high axial compression ratio and the height of column for the bearingcapacity and ductility are bad, stirrup ratio improve the bearing capacity ofpires is not obvious, while ductility increased obviously.(3) Elastic-plastic process analysis. Based on the previous fiber model,the process of acceleration is applied to analyze different seismic intensity on the pier top displacement pier, the base shear and other response, thenchoose a reasonable earthquake. On the basis of this earthquake intensity,considering the effects of corrosion on the pier top displacement, baseshear, hysteresis curve and the different.(4) Three different constitutive model was used in finite elementsoftware DIANA which use two-dimensional plane stress element. Theanalysis include monotonic loading on seismic behavior and low cyclicloading. Corrosion was considered in the program of DIANA on seismicbehavior simulation. analysis on seismic behavior change with corrosionrate, and comparison of tests and simulation.