Research On The Ultimate Bearing Capacity Of CHS K-shaped Joints With Opening

The direct welded steel pipe structure can be widely used in long-span spatial structures due to its light weight,beautiful shape,and superior mechanical properties.Due to the fact that the intersecting joints are the key part to bear the load in the structural design,and the difference in the number of joints,the size,the angle,and the shape of the cross section,the forces are complicated.When designing the structure,the overall performance of the structure may be greatly affected due to insufficient consideration of node problems.At the same time,in the large-scale steel structure buildings,due to the hidden buried requirements of pipes such as falling water and cables,it will encounter openings at the intersections of columns,columns and horizontal pipe fittings.Therefore,it is necessary to study the opening conditions of nodes.At present,national standards have mature and reliable calculation methods for the calculation of the bearing capacity of general intersecting nodes.However,although scholars have conducted research on the bearing capacity of intersecting nodes with open holes,the actual results are still small.Inconvenience for designers.Based on the above description,based on the K-shaped circular steel tube intersecting nodes,this paper specifically studies the ultimate bearing capacity of the K-shaped circular steel tube intersecting nodes with openings and related conditions in order to obtain useful results.This article first introduces the finite element theory,while focusing on the basic theory of elastoplasticity and the basic theory of nonlinear analysis.Combining the two basic theories lays the foundation for subsequent finite element analysis.Secondly,by consulting relevant literatures,determine the geometric parameters that affect the ultimate bearing capacity of K-shaped joints,and reasonably set the parameter range and loading method of the joints,and calculate the ultimate bearing capacity of the joints according to the specifications and recommended formulas.At the same time,ANSYS software was combined with finite strain shell element shell181 to establish a finite element calculation model of K-shaped joints.Based on this,the ultimate bearing capacity analysis was performed,and then the results of two parts were compared to verify the accuracy of the finite element model.Finally,by introducing the opening rate parameters,a suitable and accurate opening node model is established on the basis of the K-shaped node model,which is used to analyze the parameter model of 192 open K-shaped nodes and draw the following conclusions:1.The failure mode analysis of the K-shaped node and the open-hole K-shaped node is conducted,and it is concluded that the failure modes of the two are similar,that is,the intersection of the branch and the main reaches the yield first.When the load continues to increase,the surrounding area of the branch and the main forms The overall plastic zone was established.At the same time,with the increase of plastic deformation,stress redistribution gradually formed in this area.Finally,due to the large plastic deformation in the intersectingarea of the branch and main pipe,the bearing strength of the node reached the ultimate yield strength,which resulted in the node failure.2.Different geometric parameters have different effects on the ultimate bearing capacity of the K-shaped opening.The geometric parameters that affect the change of the ultimate bearing capacity of the K-shaped joint of the opening include the opening ratio(parameter ?),the ratio of the diameter of the branch pipe(parameter ?),and the angle between the ratio of the diameter of the pipe branch(parameter ?)and the axis of the branch pipe(parameter ?).At the same time,according to the analysis of this paper,it is concluded that the parameters ?,?,and ? are the main influencing factors,so the parameters with the main influence can be given priority in engineering applications.3.By analyzing the changes in the ultimate bearing capacity of different nodes,it is concluded that the opening rate can be conservatively taken to be 0.25 within the parameters of the article,and while the ultimate bearing capacity of the K-shaped node is almost unchanged.At the same time,in order to maintain the economics of the structural design,the optimal solution for the value of the opening rate is also given when different geometric parameters are changed individually.4.By introducing the hole reduction coefficient ?kd,based on the calculation results and simulation values in the article,and combining multiple linear regression techniques,a reduction coefficient fitting formula is obtained.The value verification and comparison analysis prove that the formula has good applicability within the parameter range.