Lead Core Heating Effects On Seismic Response Of Lrb-isolated Bridge And Energy Balance Analysis

After the Wenchuan earthquake,seismic isolation for bridges has been paid more attention in China.However,the influence of temperature change due to the transformation of mechanical energy to internal energy is seldom considered in the guide specifications for seismic design of bridge and isolation devices in China,that may cause theperformance change of the temperature sensitive rubber bearing.And there is also a lack of special consideration for near fault ground motions.In this paper,we establish a lead rubber bearing isolation bridge using the correction model,which has considered temperature,aging,seismic and other factors proposed by American scholar Constantinou et al.to study the lead core heating effects on seismic response of LRB-isolatedbridge,including the energy response and the maximum reaction,and the emphasis is on the analysis of the reaction under near fault ground motion.In the case of example analysis,the main work of this paper is as follows:(1)With the increase of the acceleration of the input seismic wave,the temperature of lead core increasedand the yield force decreased.Taking the acceleration peak 0.4g as an example,the maximum temperature of the lead core under far fault ground motion is 15 degrees,and the corresponding yield force decreases by 10%.However,under near fault ground motion,the maximum temperature of the lead core rises to 51 degrees,and the corresponding yield force decreases 27%.(2)Under near fault seismicwave,the total hysteretic energy of the support increases by 10%to 50%,the single support hysteretic energy increases by 10%～30%,and the maximum shear strain of the support increases by 0-30%when considering the effect of lead core temperature.For the design of seismic isolation,if we do not consider the lead core temperature effect,we will underestimate the demand for energy dissipation and maximum shear deformation during the earthquake,which will lead to the design unsafe.(3)The relationship between the seismic response of the bridge and ground motion parameters such as TP and PGV/PGA,and the relationship between the proportion of pluse factors in the full wave and TP and PGV/PGA were studied.The analysis shows that with the increase of pulse period,the energy response and the proportion of velocity pulse shows a process of increasing first and then decreasing,but weakly related to PGV/PGA.The relationship between the maximum response of bridge(the maximum beam displacement,the maximum shear strain of support and the maximum side shift angle of bridge pier)and TP is close to that of the energy response.