空爆载荷作用下钢筋混凝土梁压力场与响应分析

摘要

Pressure propagation process,the displacement changes of the nodes in different locations of reinforced concrete(RC) beam,the state of stress of the reinforcing steel bar and concrete,and the influence of bearing types on the damage mode of RC beam under air blast loads are studied by numerical simulation.The simulation results show that,after exploding of TNT above RC beam in the air, shock wave firstly spreads outward freely in the form of approximate spherical wave and phenomena of reflection and transmission could be found when touching RC beam.When reaching the surface of RC beam,shock wave is reflected and the peak overpressure is increased significantly.Then,when spreading to the bottom of RC beam,the shock wave is reflected and a strong tensile wave could be formed, which leads to the tensile failure of RC beam on the mid-span bottom.The mid-span top of RC beam is impacted by shock wave at the ear-liest and the bending deformation of the mid-span of RC beam is greater than those of the other parts of RC beam,the max bending defor-mations of the different parts of RC beam could be obtained when the impact of shock wave nearly disappears.Different failure modes (bending failure mainly produced on simple supported beam,and bending shear failure mainly produced on clamped beam)can be pro-duced under the same condition of explosive mass and proportion distance.The antiknock ability of RC beam could be improved by in-creasing the ratio of longitudinal reinforcement of mid-span of beam and stirrup at the supports of beam and strength of the concrete and re-inforcing steel bar,reinforcement of the local-easy cracking area(mid-span of beam and bearing point)with high stresses.%数值模拟研究了空爆载荷作用下钢筋混凝土梁正上方的压力传播过程、梁不同位置的节点位移变化、钢筋和混凝土的受力情况，支座类型对钢筋混凝土梁损伤破坏形态的影响。研究表明：空爆形成的冲击波先以近似球状的波阵面形式自由向外传播，遇到钢筋混凝土梁后发生明显的反射和透射现象；当接近梁上表面时，冲击波发生正反射，超压峰值明显升高；当冲击波传播至梁底面时，由于反射形成强拉伸波，导致梁跨中处的底面先出现损伤拉伸破坏；梁跨中顶面部位最先受到爆炸冲击波作用，跨中处弯曲变形大于其他部位并且都在冲击波作用将近结束时达到最大值。在相同炸药量和比例距离的情况下，不同支座的钢筋混凝土梁在爆炸冲击波作用下会产生不同的破坏模式（简支梁主要产生弯曲破坏，固支梁主要产生弯剪破坏）。提高梁跨中纵筋配筋率、支座处箍筋配筋率、钢筋强度和混凝土强度以及对高应力易开裂区（梁跨中和支座处）进行局部加固，可提高钢筋混凝土梁的抗爆能力。