Research On The Mechanical Properties Of The Composite Roof Truss Connected By Square Steel Pipe And Round Pipe

Through the study of the PKPM design data of a combined roof truss connected by a square steel pipe and round pipe,the following problems were found: First,all components are hinged at both ends in the design process,but the actual method is not hinged;Second,the stress situation of the steel roof truss is simulated as that the steel roof truss bears only the joint load.In fact,the chord joints bear the uniform load.The above two points are different from the actual stress situation of the project,and it is necessary to conduct in-depth study on whether the engineering design meets the requirements.Taking the case of a combined roof truss connecting square steel pipe and round pipe as the research object.This paper makes a comparative study based on finite element software design calculation and PKPM software design calculation.It also studies and analyzes the factors affecting the mechanical performance of square steel pipe and round pipe connection combined roof truss,in order to provide reference for similar design.The finite element model of a combined roof truss connected by square steel pipe and round pipe is established by ABAQUS.The design calculation results of the model are compared with those of PKPM,and the differences of displacement and stress distribution data between PKPM and ABAQUS about a square steel pipe and round pipe connection combined roof truss are compared and analyzed.It is found that: First,the displacement of PKPM data is smaller and the stress is larger than that of finite element data;Second,there is no local yield of a combined roof truss connected by square steel pipe and round pipe in PKPM data,but there is local yield between chord and web of finite element model.The research shows that there are some defects in the design of the combined roof truss connecting a square steel pipe and a round pipe only by using PKPM software.According to the in-depth study,it is found that only using PKPM software to design the combined roof truss connected by a square steel pipe and round pipe,many factors affecting the mechanical performance of the structure can not be considered in the design: chord and web do not intersect at one point,upper chord and lower chord penetration height,chord surface cushion plate,chord side strengthening plate and web rod plus outer casing.For this reason,this paper makes an in-depth study on the above influencing factors of the combined roof truss connected by a square steel pipe and a round pipe,and the conclusions are as follows:1.The axis of the chord and the web do not intersect at one point,which will increase the overall stress and displacement of the combined roof truss connected with the square steel pipe and the round pipe.2.When the penetration height of the upper and lower strings is half of the chord side length,the effect of the mechanical performance of the combined roof truss connected by the opposite steel pipe and the round pipe is better.3.The chord surface is equipped with a backing plate and the chord side is reinforced with a reinforcing plate,which greatly reduces the stress concentration and deformation of the chord.The thickness of the backing plate and the reinforcing plate is twice the thickness of the web member.The effect is the best.So the length should not be too large,as long as it meets the structural requirements such as welding.4.The web rod and the outer tube can greatly reduce the stress at the end of the web rod and eliminate the local yield of the end of the web rod.The above research conclusions provide a meaningful reference for designers when designing a combined roof truss connected by a square steel pipe and a round pipe.