Study On Bearing Capacity Of Casing Joint Of Concrete-filled Circular Steel Tubular Arch

The concrete-filled steel tubular composite structure is widely used in large span and high space structures, especially in soft rock roadway support, because it has the advantages of large rigidity, good seismic performance and convenient construction. It solves the safety and economic problems caused by the traditional support form such as anchor net spray, u-section steel stents and so on, which greatly promoted the development of Chinese coal mining industry and national economy.In recent years, with the increasing application of concrete-filled circular steel tubular arch,the bearing mechanism and failure mechanism have been paid more and more attention, but the related research is not much, especially on the weak parts of the arch -the casing joint. Therefore, it is very important to carry out the experimental study on bias and pure bending performance of the casing joint of the concrete-filled steel tubular arching.In this paper, the bending test of 10 concrete-filled circular steel tubular casing joints and conventional components were carried out,which is controlled by the load first and then by the displacement.The load displacement curve and the load strain curve of the main sections of the specimen are obtained by the bridge displacement meter and the resistance strain gauge. Analysis shows that the effect of the casing joint on the specimen is mainly in the elastic-plastic stage, and the greater the eccentricity of the load is, the more obvious the casing action is.The normal cross-section Nu-Mu curve of the specimen is obtained by numerical calculation. The results show that the bearing capacity of the casing is significantly lower than that of the conventional components by comparing the Nu-Mu curve of the specimen with the cross-section load-strain curve.The influence of casing and casing parameters on the bearing capacity of concrete - filled circular steel tubular arch is studied by using the finite element software ABAQUS to simulate the conventional components and casing joints.In the simulation process, solid modeling,steel and concrete use C3D8R units, and the Tie constraint is used between steel pipe and concrete to ignore the relative slip, and surface contact (Surface-to-Surface contact) is used between the steel pipe and casing , so more close to the engineering characteristics of the arch in the force.Compared with the laboratory experiment, the experimental phenomena and the load-displacement curves are consistent with each other,and the correctness of the numerical simulation is verified. The Nu-Mu curve of the normal cross-section bearing capacity of each specimen was obtained by laboratory tests and numerical simulation.The calculation formula of the ultimate bearing capacity of the conventional components and the casing joints is obtained by using the origin software.Finally, the influence of concrete strength, casing length,wall thickness and clearance on the bearing capacity of arch section is discussed,which provide some reference for the design of concrete-filled circular steel tube arch.