海冰对单柱式桥墩非线性地震反应的影响

Effects of sea ice on the nonlinear seismic responses of single-column piers

用简化的附加水质量模型考虑动水压力对桥墩的影响,用动冰力模型考虑冰与桥墩的相互作用,建立了冰水域单柱式桥墩地震反应的动力计算模型,并利用时程分析法研究了在不同类型地震作用下海冰对桥墩非线性地震反应的影响.桥墩的最不利反应一般发生在海冰质量为5×106～5×107kg,可作为桥墩设计时的海冰质量;且墩底截面出现最大曲率时对应的海冰质量随着水深的增大而变大.有冰时墩底截面曲率延性需求系数、墩顶最大位移和墩顶残余位移比无冰时增大数倍,墩底截面弯矩–曲率滞回曲线呈倒"S"型更显著,桥墩的变形和耗能能力显著下降.同时,与近场地震波作用时相比,远场地震波作用下海冰对单柱式桥墩顶部最大位移和残余位移的影响更大.

The effect of hydrodynamic pressure on bridge piers was considered by a simplified model of additional water and the interaction between ice and bridge piers was taken into account by a dynamic ice force model, then a seismic response analysis model was established for a single-column pier surrounded by sea ice and the nonlinear seismic responses of the pier subject to different types of earthquakes were analyzed by using the time-history analysis method. It is shown that the least favorite seismic responses of the pier occur when the mass of sea ice is 5×106 to 5×107 kg, which can be used as the design mass of sea ice to design a bridge pier. The mass of sea ice under the maximum curvature condition of the pier increases with the water depth increasing. The curvature ductility demand coefficient, the maximum displacement and the residual displacement of the pier surrounded by sea ice are several times larger than the seismic responses of the pier which is not. Since sea ice also makes the moment-curvature hysteretic curves of the pier＇s bottom cross-section present a downfallen ＇S＇ form significantly, the deformability and energy dissipation capability of the pier drop remarkably. Compared with the pier subjected to a near-field seismic wave, the effects of sea ice on the maximum displacement and residual displacement of the pier subjected to a far-field seismic wave are more remarkable.