钢筋混凝土板受燃气爆炸作用下的行为响应及承载力性能分析

Analysis of behavior and load bearing capacity of RC slabs subjected to gas explosions

燃气爆炸的反应过程与荷载特征与炸药爆炸明显不同。为研究燃气爆炸对钢筋混凝土板行为响应及竖向承载力的影响,采用FLACS模拟得到了室内燃气爆炸典型的超压时程曲线,结合LS-DYNA有限元软件建立的楼板数值分析模型,研究了钢筋混凝土板在燃气爆炸下的动态响应、破坏模式及在抗倒塌过程中的受力机制和承载能力,以及混凝土、钢筋强度等因素的影响。结果表明:钢筋混凝土板在燃气爆炸荷载作用下呈典型的弯曲破坏模式,且与能量等效的TNT爆炸相比,动态响应及损伤相对较小;燃气爆炸后楼板在抗倒塌过程的初期以薄壳受力机制为主,随后由受弯机制发展为受拉薄膜机制,但因受拉薄膜效应无法有效开展而导致爆炸后楼板的承载能力出现中度下降;增大钢筋直径,减小钢筋间距,采用双层配筋方式,以及在高强度钢筋对应的适筋范围内增大混凝土强度,可有效提高楼板抗燃气爆炸的能力,并降低爆炸对板承载力的影响;增大钢筋强度虽能提高楼板抗燃气爆炸能力,但亦会增强爆炸对板承载力的影响,而在低强度钢筋对应的适筋范围内增大混凝土强度基本不会改变爆炸对板承载力的影响。

The reaction process and load characteristics of gas explosions are obviously different from TNT explosions. To investigate the effect of gas explosions on the behavior and vertical load bearing capacity of RC slabs,the typical pressure time history of gas explosions was simulated using FLACS. Based on the obtained curve and the numerical model established in LS-DYNA,the dynamic response and failure mode of RC slabs under gas explosions were analyzed. Then,the loading mechanism and load bearing capacity of RC slabs in the anti-collapse process were studied and the effects of factors were further analyzed. The results indicate that RC slabs exhibit the flexural failure mode under gas explosions,and the dynamic response and damage are less severe than those of TNT explosions. In the process of collapse after gas explosions,the shell mechanism plays a major role in the early stage,then the bending mechanism develops and finally the tensile membrane action works. However,because the membrane action cannot fully develop in some cases,the vertical load bearing capacity of RC slabs are reduced to the medium level. Increasing rebar diameter,decreasing the rebar spacing,using the double-layer reinforcement,and increasing the concrete strength in the under-reinforced range corresponding to high rebar strength can effectively improve the gas explosion resistance and decrease the effect of gas explosions on load bearing capacity of RC slabs. However,though the gas explosion resistance will be improved with the increase of the rebar strength,the effect of gas explosions on load bearing capacity of RC slabs will also be improved. Moreover,increasing the concrete strength in the under-reinforced range corresponding to low rebar strength cannot change the effect of gas explosions on load bearing capacity of RC slabs.