Study On Nonlinear Problems Introduced By Gradient In The Design And Construction Of Long-span Steel Truss Bridges

Sometimes, there will be height difference at both ends of long-span steel truss bridge which brings new difficulties in design and construction. For example the nonlinear problem caused by height difference when determining construction arc length .The precision degree of nonlinear problem solving affects bridge construction smoothly. The actual bridge construction arc length greater than the design value caused by cross-strait elevation lead to Ningbo yongjiang mouth of yongjiang railway bridge project construction midway shutdown. Therefore, the investigation of the nonlinear problem caused by height difference during large-span steel truss bridge design and construction has certain practical significance.In view of the above questions, this paper is mainly on the following two study works:â‘ Analysis of the key problem in the design plan of long-span steel truss bridge with height difference;On the base of mechanical system analysis of construction period and service phase of Long-span steel truss bridge, the main works can be summarized as follows:1)the selection of mechanical system scheme;2) mechanical system conversion in construction process;3) The determination principle of key design parameters, and so on. This paper is trying to design the large-span steel truss bridge with height difference into fixed beam ends in order to reduce the maximum deflection of the bridge and meet the requirement of biggest scratching ratios; According to different bridge construction plans, the mechanical system of bridge in the construction process will be simplified as a model which is an end fixed and an end simply supported or a simple supported beam .â‘¡Design and construction of the nonlinear calculation caused by height difference;For the three mechanical models abstracted from design and construction above, using two-parameter perturbation method to solve it. Due to the combined effect of height difference and load, making the first order derivative of deflection involved in the basic deformation of the beam equation (Euler-Bernoulli's equation) not be ignored, so that the real problem became a problem of large deflection of the beam. In this paper, we use two perturbation parameters, one parameter describes dynamic load characteristic of the problem, and the other describes geometric height difference characteristic of the problem, The combination of two parameters determined by the specific characteristics of the problem. The obtained solution covers all the effect of nonlinear factors to the solution. In addition, to simplify the solution of the problem . This paper proposes a two-parameter perturbation method based on substitution of the first derivative, by simplifying the basic equations ,so that making the two-parameter perturbation directly to the simplified nonlinear algebraic equations instead of the original integral equations, the results show that the solution precision is still meetting the design requirement.The results of this subject can provide a theoretical calculation of reference for design of the arc length of the large span steel truss bridge with a height difference and rigidity of construction and calculation of the deflection in use; the use of two-parameter perturbation technique in the subject has opened up a new idea for solving deformation of the geometric nonlinear beam.