The Research Of An Arcuated Built-up System Bridge Structural Characteristics

Arcuated built-up system bridges are one of bridge structural styles, which are used extensively at present. On one hand, because of complexity and diversity of this kind of structure, current engineering experiences have not satisfied design requirements no longer. On the other hand, towards this kind of structural system traditional methods simplify complicated structures into planar structures, these methods neglect apparently spatial action among members, especially those primary bearing load members along lateral direction of bridges. Therefore how to simulate exactly an arcuated built-up system bridge, carry calculation and design of it and obtain behaviors in accord with facts, is a urgent task in front of bridge workers.The paper is based on an arcuated built-up system bridge-Zhongshan No.one Bridge to be built in Guangzhou, adopts the large universal finite element programme ANSYS, takes spatial action among members into account, establishes a three-dimension finite element model, and discusses the following several aspects:Firstly, when three-dimensional finite model of a complicated bridge is founded, a beam-lattice method is a kind of applied and effective spatial analysis method, which is used to analyze superstructures of a bridge. When whole analysis is carried through the beam-lattice method and bridge surface is made of box beams with one box and two cells, according to the principle of constant bending rigidity and every part revolving the same neutral axis, a box beam can be simplified into three beams in the places of corresponding webs. Thus effective transfer of shearing force can be ensured, and global property can be reached through that of three beams, this kind of method is simple and is able to ensure engineering precision;Secondly, the paper is based on elastic theory, adopts finite element method and carries through the first kind stability analysis towards Zhongshan No.one Bridge. Destabilization style of an arcuated built-up system bridge, influence of nonconservative force of hanger rods, comparative between stress value in construction stage and stress value in finished bridge stage,stability coefficients in bridge code, these are discussed deep.Destabilization laws of an arcuated built-up system bridge are provided, nonconservative force of hanger rods and members' bearing force are integrated in order to consider influence of hanger rods towards arch stability. Besides, stress values of some members are probably higher than those of some members in finished bridge stage. Therefore failure of members should be avoided in construction stage due to insufficiency of strength.Thirdly, subspace iterative method is adopted in the paper, and natural periods and modes of preceding fifteen steps of Zhongshan No.one Bridge are solved, dynamic characteristics of this kind of structural system are obtained, inherent link between dynamic characteristics and structural rigidity is discussed deep, the viewpoint is provided that dynamic characteristics of a structure are considered as important basis whether structural scheme is rational;In addition, the author brings out some own views and opinions about calculational methods of prestress value of different sorts of tie rods, simulation of local rigidity region, foundation of a local finite element model of a node. Some helpful suggestions and conclusions are provided for similar complicated structures.