方钢管混凝土的共同工作状态研究

Study on Cooperative Action Between Steel and Concrete in Concrete-filled Rectangular Steel Tube

根据试验和对方钢管混凝土柱的超声波检测结果,发现钢管和混凝土之间存在缝隙,界面承载力应主要来源于钢管壁粗糙造成的机械咬合力和摩擦力,当界面上部分粘结达到破坏界限后,仍然具有一定的界面承载力,滑移发生后,界面承载力主要来源于核心混凝土与钢管壁间的摩擦力,此时界面承载力基本保持常数,且其值较小,分析相关文献结果认为在0.15～0.3N/mm^2之间变化。将现有试验成果进行比较,发现界面承载力和混凝土的标号关系不大,而与混凝土的干缩有很大关联,并且在承担水平荷载的情况下,界面承载力随水平力的变化而发生明显变化,在只承受竖向荷载时,影响界面承载力的主要因素有长细比、径厚比和混凝土的浇筑方式等。分析了目前我国方钢管混凝土计算理论的现状,由于界面缝隙的存在,提出钢管与核心混凝土的弱粘结问题(部分粘结)和界面承载力考虑方法,为钢和混凝土共同工作性能确定及方钢管混凝土承载力计算提供依据。

According to consequence of the ultrasonic detecting on the CFRT,it is found that there are lots of gaps between the pipe and concrete.So the interfacial bearing capacity should root in the mechanical clutch force and friction force to which is contributed by the roughness of the steel pipe.There is also some interfacial bearing force after reaching the limit of interfacial bearing capacity.The force is rooted in the frictional force when there is any slipping,then it keeps a constant ultimately,and the numerical value is small,ranging between 0.15 and 0.3 N/mm^2.The existing experimental results are summarized,and the interfacial bearing strength is hardly related to the concrete grade,but has a close relationship with the concrete dry shrinkage.In addition,the obvious changes in interfacial bearing capacity often occur because of shifts in horizontal force when the tube responds the horizontal load.When the tube only responds the vertical load,the ratio of slenderness,the radius-thickness ratio and the place way of the concrete are the contributing factors to the bond strength.The status of research on calculation theory of CFRT in china is analyzed.The problems of weak bond and cooperative action between the steel pipe and inner concrete according to the existing of the gaps are reanalyzed,method of load-bearing capacity on interface is discussed,calculation theory and references are provided for principle of cooperative action and the load-bearing capacity of CFRT.