近断层地震动下曲线梁桥碰撞效应研究

Pounding effect of curved bridges subjected to near-fault seismic ground motions

桥梁的地震碰撞会导致结构局部破坏,甚至造成落梁、倒塌等严重灾害,曲线梁桥的非规则性使得其碰撞效应与直梁桥显著不同。对一典型的三跨曲线梁桥建立多尺度有限元数值模拟模型,利用三维接触-摩擦模型结合显式动力接触算法模拟曲线梁桥上部主梁间的碰撞,研究了近断层地震动下碰撞效应对曲线梁桥地震反应的影响,并对地震动参数、碰撞刚度、伸缩缝间隙及曲率半径进行了详细的参数影响分析研究。研究结果表明:曲线梁桥地震响应受非均匀碰撞影响显著,碰撞限制了主梁相对位移;近断层脉冲地震较其他两类地震对曲线梁桥碰撞效应的影响更为显著,碰撞力最大值随着碰撞刚度和曲率半径的增加而增大,随着伸缩缝间隙的增大而减小,主梁相对位移响应则相反;外侧切向位移较大,落梁很有可能从曲线梁外侧发生。

Bridges’ seismic pounding leads to local damage of a structure,and even causes serious disarsters,such as,falling beam and collapsing. The irregularity of curved bridges makes their pounding effects be significantly different from those of straight beam bridges. A multi-scale finite element model of a typical 3-span curved bridge was established and poundings among its upper part’s main beams were simulated using the 3 D contact-friction model combined with the explicit dynamic contact algorithm. The influences of pounding effects on the seismic response of the curved bridge under near-fault earthquake were analyzed. Meanwhile,a detailed parametric effect analysis was performed including ground motion parameters,pounding stiffness,expansion joint clearance and curvature radius,etc. parameters. The numerical results indicated that the seismic response of the curved bridge is significantly affected by inhomogeneous poundings and poundings restrict relative displacements of main beams; near-fault impulse earthquakes affects the pounding effect of the curved bridge more significantly than other two types earthquakes do; the maximum pounding force increases with increase in pounding stiffness and curvature radius,and decreases with increase in expansion joint clearance while main beams’ relative displacement response has the opposite changes; falling beam may occur at the curved beam outside due to excessive large outside tangential displacement.