地震作用下曲线梁桥非均匀碰撞效应研究

Uneven distribution of pounding effect in a curved girder bridge under earthquake

曲线梁桥在地震作用下产生的不规则平面旋转位移使得应用碰撞单元法计算曲线梁体碰撞效应存在一定的局限性,为了探讨曲线梁桥地震碰撞效应的非均匀分布规律,提出了采用显式动力接触算法计算曲线梁桥地震碰撞效应的数值模拟方法,并分析曲线连续梁桥碰撞效应引起的主梁、挡块和桥墩的冲击地震反应特点。结果表明,主梁与桥台胸墙的碰撞作用限制了主梁的切向位移,使得固定墩墩底弯矩小于不考虑碰撞时的墩底弯矩。碰撞后梁端截面顶板正应力和曲线内外侧挡块径向应力的分布严重不均匀,梁端截面悬臂翼缘的正应力明显小于腹板间顶板的正应力,曲线外侧挡块的径向应力显著大于内侧挡块的径向应力。地震碰撞作用使得主梁的最大拉应力和压应力通常会发生在梁体曲线的内外侧。这为合理解释曲线连续梁桥在强震下的碰撞破坏震害现象提供了理论指导。

Because of irregular rotational displacements of a curved girder bridge under earthquake,there are some limits to calculate its pounding effect with pounding element approach.In order to analyze the uneven distributing rule of seismic pounding effect for a curved girder bridge,a new approach of explicit dynamic contact algorithm was presented.Seismic impactive response characteristics of girder,pier and block were analyzed.The results indicated that the pounding action between girder and abutment limits shear displacements of girder and makes bending moment of fixed pier smaller than that without pounding effect;after pounding,the normal stress distribution of upper board on girder end and the radial stress distribution of blocks inside and outside the curve are severely uneven;on the cross section of girder end,the normal stress of flange is obviously smaller than that of upper board between webs;the radial stress of block at outside curve is larger than that at inside curve distinctly;the seismic pounding effect makes maximum tensile stress or compressive one occur at inside curve or outside curve.These results provided a theoretical guide for explaining phenomena of pounding damages for a curved girder bridge under earthquake.