地震动强度及近断层速度脉冲峰值对简支板桥地震响应影响

地震动强度和近断层速度脉冲峰值均为导致桥梁结构震害的主要原因。与其他桥型相比，简支板桥在地震中更容易发生破坏和损毁。作者以在2008年汶川地震中出现严重破坏的高原大桥（预应力混凝土简支空心板桥）为研究背景，探讨大桥所处场地的人工边界分别为自由边界、固定边界、黏弹性边界和黏弹性+阻尼层边界时对计算结果精度、计算效率等的影响。通过ABAQUS建立包含高原大桥及其场地的整体有限元模型，人工边界采用黏弹性+阻尼层边界，并以地震波加速度峰值作为地震动强度指标和人工合成近断层速度脉冲型地震波，分析地震动强度、近断层速度脉冲峰值对简支板桥地震响应影响程度。结果表明：人工边界为黏弹性+阻尼层边界时，可有效减弱边界处的反射效应，计算结果精度基本能满足要求；近断层速度脉冲峰值对结构地震响应的影响比地震动强度更为显著；场地表面加速度峰值随地震动强度提高而增加；近河岸和存在基岩分界面易导致简支板桥局部结构的地震响应加剧；随地震动强度或近断层速度脉冲峰值或地震波位移峰值的增加，跨径变化峰值、相对滑移量和滑移峰值变大；近断层速度脉冲型地震波对桥梁的影响比无脉冲型地震波更为不利。

Effects on Earthquake Intensity and Peak of Near-fault Velocity Pulse on Seismic Response of the Simply Supported Slab Bridge

The main reasons for earthquake damage of bridge structures are earthquake intensity and peak of near-fault velocity pulse. Compared with other bridge types, simply supported slab bridges are more likely to be damaged in the earthquakes. Gaoyuan bridge was a kind of simply supported hollow slab bridge of prestressed concrete, which was seriously destroyed in the Wenchuan earthquake in 2008. The effects of artificial boundary on the site on the accuracy of calculation results and calculation efficiency were studied carefully while the boundary was free boundary, fixed boundary, viscoelastic boundary and the artificial boundary of viscoelastic damping layer, respectively. The finite element model of Gaoyuan bridge included structure and site was established by ABAQUS, and boundary condition was the artificial boundary of viscoelastic damping layer. The effects of earthquake intensity and peak of near-fault velocity pulse on this bridge were researched. Peak acceleration of seismic wave represented earthquake intensity, and seismic wave with near-fault velocity pulse characteristic was synthesized. The results showed that when the artificial boundary of the model is the artificial boundary of viscoelastic damping layer, the reflection effect at the boundary could be effectively reduced and the accuracy of calculation results meets the basic requirements. Peak of near-fault velocity pulse is more sensitive to the seismic response of bridge than earthquake intensity. Peak accelerations of all points are improved on the site surface while earthquake intensity is raised. The earthquake damage of local structure is aggravated easily for closing to river bank and existing bedrock interface. The increase of earthquake intensity, peak of near-fault velocity pulse or peak of seismic wave displacement lead to enhance peak of span variation, relative slipping and slipping peak. Wave seismic with near-fault velocity pulse feature caused earthquake destruction in the bridge to be magnified.