混凝土梁桥桥下爆炸压力场分析

Analysis of pressure field for concrete girder bridges under below-deck explosions

为了探索桥下爆炸自由场超压、墩柱反射超压和梁底反射超压的分布规律,对一座两跨混凝土梁桥缩尺模型开展了桥下爆炸试验,并结合数值模拟方法研究了桥下爆炸波传播规律以及爆炸波与T梁和墩柱之间的相互作用.研究结果表明:地面反射条件的改变对爆炸荷载影响显著;实测柱底、柱中和柱顶超压峰值沿柱高分布相对离散,实测T梁底超压时程曲线呈多峰正压.爆炸波传播过程中有马赫波形成;爆炸波遇到T梁梁肋和横隔板会发生反射和绕射,遇到T梁翼板下表面会发生反射,爆炸波传播至墩柱盖梁和T梁相交区域时,传播路径较为复杂,作用时间相对较长.炸药形状对T梁底部超压分布有一定影响,中梁梁肋下表面的超压峰值自爆心向两边呈指数形式衰减;超压峰值沿柱高整体呈减小趋势,柱底、柱中和柱顶迎爆面沿柱周超压峰值整体呈中间大两边小的趋势.

To explore the distribution law of free-field overpressures,reflected overpressures of the columns and the bottom faces of T-beams for bridges subjected to below-deck explosions,the below-deck blast test for a scaled two-span concrete continuous T-beam bridge was carried out,and the blast wave propagation law below the bridge deck,the interaction between blast wave and T-beam as well as that between blast wave and columns were investigated through numerical simulation.The results show that the variation of ground reflection condition has a significant influence on the blast load;the measured peak overpressures at the bottom,middle and top of the column are relatively discrete along the column height;the time-history curve of the measured overpressure at the bottom of the T-beam shows multi-peak positive pressure.Mach wave is formed in the process of explosion wave propagation;the explosion wave will reflect and diffract when it encounters the T-beam rib and diaphragm,and when it encounters the bottom surface of the wing plate,reflection will occur;when the blast wave propagates to the intersection area of the bent and the T-beam,the propagation path is complicated,and the action time is relatively long.The explosive shape has a certain influence on the overpressure distribution at the bottom of T-beam,and the peak overpressure on the bottom surface of the rib of middle beam decays exponentially from the explosion center to both sides.The peak overpressure generally decreases along the column height;on the front surface,the peak overpressure distribution around cross section at the bottom,middle and top of the column shows a trend of being larger in the middle and smaller on both sides.