钢支撑加固RC框架抗连续倒塌试验与数值模拟研究

Tests and numerical simulation for anti-progressive collapse of RC frame reinforced with steel braces

为研究钢支撑对RC框架抗连续倒塌性能的加固效应,在实验室制作了2榀RC平面子框架试件,并对其中1榀框架通过钢支撑进行加固,采用pushdown加载方式研究钢支撑对RC框架破坏模式和抗倒塌承载能力的影响。试验结果表明:钢支撑可以提高峰值荷载超过122%,其承载能力随拉杆的断裂而突然下降;由于压杆在加载初期就发生严重的平面外屈曲破坏,故仅对试件的初始刚度有影响,对峰值荷载作用很小。为进一步量化拉杆与压杆的加固贡献,通过商用有限元软件LS-DYNA进行精细有限元分析。有限元结果进一步验证了试验结果:采用角钢加固RC框架,压杆在加载初期容易发生平面外屈曲,对结构抗力影响不大,抗力提升主要由拉杆提供;通过拓展分析发现:采用防屈曲支撑加固可以显著提升压杆对结构抗力贡献,如压杆使用方钢管混凝土截面比L形截面峰值荷载提升超过42.8%。

Here,to study reinforcement effect of steel braces on anti-progressive collapse performance of RC frame,two RC plane subframe specimens were fabricated in lab,and one of them was reinforced with steel braces.Effects of steel braces on failure mode and anti-collapse load-bearing capacity of RC frame were studied using the pushdown loading method.The test results showed that steel brace can increase the peak load by more than 122%,and its load-bearing capacity suddenly drops with fracture of pull rod;because compression bar has serious out of plane buckling failure in initial stage of loading,it only affects the initial stiffness of the specimen and has little effect on peak load.In order to further quantify the reinforcement contribution of pull rod and compression bar,the fine finite element analysis was performed using the commercial finite element software LS-DYNA.The finite element results showed that the test results were further verified;when a RC frame is reinforced with angle steel,compression bar is easy to have out of plane buckling in initial stage of loading,it has little effect on structural resistance force;the resistance force improvement is mainly provided by pull rod;the expansion analysis reveals the contribution of compression bar to structural resistance force can be significantly improved by using buckling-restrained brace,for example,the peak load of compression bar using concrete-filled square steel tubular cross-section is more than 42.8%higher than that using L-shaped cross-section.