薄壁方钢管混凝土柱轴压承载力试验研究

Experimental Research on the Axial Compressive Capacity of Thin-Walled Concrete-Filled Square Steel Tubular Columns

通过对10个薄壁方钢管混凝土柱的轴压试验,研究了长细比、壁厚、混凝土强度三种因素对试件破坏形态、荷载-位移曲线、极限承载力及泊松比等力学指标的影响。结果显示,薄壁钢管混凝土柱试件的加载过程与普通钢管混凝土柱试件类似,总体上可分为弹性、弹塑性和下降三个阶段。本试验试件破坏均表现为核心混凝土被压碎,钢管外部出现环向屈曲带。利用有限元软件建立了薄壁钢管混凝土柱模型并验证了其有效性与可靠性,分析结果表明:当构件截面含钢率一定时,混凝土强度对钢混结构的组合效率影响十分明显,对于含钢率为0.02~0.06的薄壁构件,采用强度等级为C20~C50的混凝土能明显提高钢混结构的组合效率;对于稳定承载力,发现不同变化参数下的稳定系数均可以采用以正则长细比为自变量的单一方程来表示。参考GB 50936—2014《钢管混凝土结构技术规范》提出了薄壁方钢管混凝土柱轴压承载力的简化计算式,计算值与实测值吻合良好。

Tests of 10 concrete-filled thin-walled square steel tubular columns under axial compression were conducted,the influence of slenderness ratio,wall thickness and concrete strength on the failure pattern,load-displacement curve,ultimate bearing capacity and Poisson’s ratio of the specimens were studied.The results showed that the loading process of concrete-filled thin-walled steel tubular column was similar to that of ordinary concrete-filled steel tubular cloumn.Generally,it could be divided into three stages:elastic stage,elastic-plastic stage and descending stage.The failure of the specimens in the test was that the core concrete was crushed and there was a circumferential buckling band outside the steel pipe.The finite element software was used to establish the model of concrete-filled thin-walled steel tubular column and verify its effectiveness and reliability.The analysis results showed that when the steel ratio of member section was certain,the influence of concrete strength on the combination effect of steel-concrete structure was very obvious.For thin-walled members with steel ratio of 0.02 to 0.06,the combination efficiency of steel-concrete structure could be improved by using concrete with strength grade of C20 to C50.For the stability bearing capacity,it was found that the stability coefficient under different variation parameters could be expressed by a single equation with the regular slenderness ratio as the independent variable.Finally,referring to Technical Code for Concrete Filled Steel Tubular Structures(GB 50936-2014),a simplified calculation formula for the axial compressive bearing capacity of concrete-filled thin-walled square steel tubular columns was proposed,and the calculated values were in good agreement with the measured values.