| The new steel arch with adjustable axis has been used in the construction of concrete arch bridges.To achieve greater adjustability,wider applicability,better linearity,reasonable mechanical properties and deformation performance,it must be designed.The key node of this bracket is the spherical connection system node with adjustable length and direction set in the upper chord of the bracket.This node system must not only achieve the above mechanical functions,but also have good mechanical properties and deformation properties.Ensure that the support structure is strong and adjustable,but also safe and reliable.The mechanical and deformation characteristics of this connection system node are much more complicated than other nodes of the bracket structure,especially the mechanical and deformation characteristics of the spherical node stiffness formed by the externally preloaded high-strength bolts in this node.It plays a decisive role,and even plays an important role in the bearing capacity and deformation of the entire arch.Therefore,it is necessary to conduct a comprehensive study on the joints of the new arch spherical connection system to obtain its mechanical properties and deformation characteristics.To this end,this article conducted the following research:In this paper,first,using Abaqus finite element software,using solid elements to establish a refined model of the connection system nodes,local analysis of the nodes,and the non-planar and out-of-plane non-planar connection system nodes based on state nonlinearity and geometric nonlinearity are obtained.Linear bending moment-turning angle characteristic curve,and proposes a method for determining the bending moment-turning curve characteristic of the node system,defining three phases of the curve,respectively: elastic phase,nonlinear phase and failure phase,and gives The method of determining the critical critical point is obtained,and the initial rotational stiffness in the in-plane and out-plane directions of the node are obtained:1961kN·m/rad,4533kN·m/rad,and the quantitative judgment is based on the European steel structure design code Eurocode3 The nodes studied belong to the category of semi-rigid nodes.The above method for solving the initial rotational stiffness of the nodes is applied to the actual project to obtain the initial rotational stiffness of the new arch frame at the nodes at four different connection points.In order to discuss the semi-rigid performance of the joints,a large number of analyses were made on the sensitive factors that affect the semi-rigid performance of the joints,totaling 22 sets of data.The effects of joint load,joint friction coefficient,adjusting screw diameter,high-strength bolt diameter,and high-strength bolt performance level on the initial stiffness and ultimate bearing capacity of the joint are specifically studied.Research indicates:Under the same other conditions,the influence of various factors on the initial stiffness of the node:(1)Adjusting the screw diameter has the greatest effect on the initial stiffness of the node,and as the diameter increases,the initial rotational stiffness increases;(2)Different friction coefficients also have a certain effect on the initial stiffness of the node.As the friction coefficient increases,the initial rotational stiffness also increases;(3)The size of the joint load,the diameter of the high-strength bolt,and the performance level have basically no effect on the initial stiffness of the joint.Under other conditions being the same,each factor has a certain effect on the ultimate bearing capacity of the node: according to the degree of influence on the ultimate bearing capacity of the node,it is divided into friction coefficient,adjusting screw diameter,high-strength bolt diameter,node load size and high-strength bolt performance grade.Finally,combined with engineering examples,the nodes of the arched spherical connection system were introduced into the overall structure of the arch.The Madis Civil finite element software was used to establish a new model of the overall space of the arch using beam elements,and the theoretical and measured values were compared and analyzed.Its consistency shows that it is more reasonable to consider the nodes of the arched spherical connection system as semi-rigid nodes.Compared with the arched spherical nodes as twisted nodes,the deformation calculation accuracy is increased by21% and the stress calculation accuracy is increased by 10%.It also shows that the method used in this paper to determine the initial rotational stiffness is correct,and the initial rotational stiffness of each part is also correct. |
