Research On Seismic Performance Of Coastal Bridges Considered Coupling Effects Of Seismic Action And Resistance Deterioration

Bridge is becoming more and more important in our daily life, the change of itsseismic performance in the whole design working life has attracted wide attention ofscholars from different countries. Especially for the bridges near or cross the sea, thecorrosion caused by chloride ions will result in significant degradation of materialproperties in a short time. Here a proper evaluation method is needed. It’s a newidea to take into consideration the coupling effects of earthquake action andcorrosion degree to assess the bridge’s seismic performance.Based on Comsol software package, the diffusion of chloride ions before rebarcorrosion is simulated,3models are established by OpenSees at different momentsin bridge’s design working life and the seismic performance is assessed. The maincontents are:(1) Through research on Chinese Code, Euro code and United States standard,according to equal exceeding probability principle, the earthquake action which isused to assess the bridge’s seismic performance at different service stages iscalculated. The results indicate that earthquake intensity is reduced as the length ofservice period is increased.(2) Based on Comsol, the rebar corrosion time in the atmosphere zone, sprayand splash zone, and the submerged zone of the bridge piles are calculated. Thechloride diffusion equation takes many factors into consideration. In spray andsplash zone, the corrosion is most serious while in submerged zone, thechloride-induced corrosion is seldom happened because of the lack of the oxygenand light.(3) Considering the effect of corrosion on the steel yield strength and diameter,three models are established by OpenSees, these models corresponding to threedifferent moments (0,30,45years after structure constructed). Ten properearthquake ground motions are selected to perform increment dynamic analysis onstructures. The results show that the fixed bearing damage is reduced while the pierdamage is increased as the corrosion aggravated.(4) The seismic action intensity which is calculated by equal exceedingprobability principle is used to assess the seismic performance of bridge at threedifferent moments (0,30,45years after structure constructed). The results indicatethat the fragile of four damage states decrease as the length of service period isincreased if the effects of earthquake action and corrosion degree are considered atthe same time.