暴雨洪涝灾害下漂浮物堵塞对施工栈桥稳定性影响分析

Effects of floating object-induced blockage on construction trestle bridge stability in rainstorms and floods

【目的】暴雨洪涝灾害中,洪水会携带大量杂木杂草垃圾等漂浮物,施工栈桥上部贝雷梁由于杆件密集,容易堵塞,堵塞后水流压力更大,更容易导致施工栈桥的破坏。【方法】为分析不同工况下漂浮物堵塞对施工栈桥稳定性的影响,以黄河特大桥施工栈桥为例,利用ANSYS模拟计算,分析了(1)漂浮物未堵塞贝雷梁;(2)漂浮物堵塞单跨贝雷梁;(3)漂浮物堵塞双跨贝雷梁以及在不同水流速度下施工栈桥稳定性。【结果】结果显示:随着水流速度的增大,施工栈桥水流方向位移极值和米塞斯应力极值也随之增大,贝雷梁未被堵塞工况下,位移极值和米塞斯应力极值增长率最小,双跨贝雷梁被堵塞工况和单跨贝雷梁被堵塞工况位移极值和米塞斯应力极值增长率接近。【结论】暴雨洪涝灾害中,漂浮物堵塞和水流速度对施工栈桥稳定性不利,会增大施工栈桥的位移和应力,导致施工栈桥的局部破坏,可为暴雨洪涝灾害中施工栈桥防护提供参考。

[Objective]In rainstorms and floods,floodwater is laden with floating objects such as wood debris,grass,and trash,which tend to jam the Bailey truss of the superstructure of a construction trestle bridge.The blockage leads to higher water pressure and also an increased likelihood of bridge failure.[Methods]To understand the effects of floating object blockage on the stability of the construction trestle bridge,a case study is performed on a grand bridge across the Yellow River via the numerical simulation using ANSYS to characterize the bridge stability in cases with(1)no Bailey beam blockage,(2)one-span Bailey beam blockage,(3)two-span Bailey beam blockage and varying water flow velocities.[Results]With an increased water flow velocity,the extremums of the displacement along the flow direction and the Mises stress extremums of the bridge climb up correspondingly.The case with no Bailey beam blockage is associated with the least growth rates of the maximum displacement and Mises stress,while those with one-span and two-span blockage show similar result.[Conclusion]Therefore,it can be concluded that floating object-induced blockage and accelerated water flow have negative effects on the stability of the construction trestle bridge during rainstorms and floods.They can raise the displacement and stress of the bridge and lead to local bridge failure.The findings of this research provide references for protecting construction trestle bridges during rainstorm/flood-triggered disasters.