Truss Overhead Crossing Structure Analysis Of Pipeline Engineering Over Sichuan-ZhijingRiver

The overhead crossing design is the important constituent of the engineering design about oil-gas pipeline, the truss overhead crossing structure is widely used in the middle and small scale overhead crossing projects below 100-meter because of the merits that structure is simple, arrangement is flexible, construction technique is mature and so on. The truss method is selected by the project of pipeline overhead crossing over the Zhijing river in Sichuan province.This project's reasonable design requires that overhead crossing structure must both satisfy project's intensity and stable requests under each kind of possibility operating mode, and give dual attention to save material and reduce investment. Regarding this goal, the article used the ANSYS finite element analysis software to carry on optimization design, stability analyses, modal analysis and earthquake dynamic response analysis for the truss overhead crossing structure, carried on the discussion in view of the difficult problems involved, expects to have guidance value to the truss overhead crossing design.First, this article built several optimized models of truss overhead crossing structure, to analyze the relations between the structural strength, the amount of deflection as well as the quality and optimization design variables including truss member section size, truss section form and so on. This article analyses emphatically to the truss section form's influences, and has drawn some meaningful conclusions: the triangle section truss is most superior, next is the trapezoid, the rectangle is worst; variable cross-section truss and constant section truss are quite in intensity and amount of deflection, but the former is short a lot in material consumption; although the variable cross-section truss consumes the material to be much less than the constant section truss, but its certain web member length varies, this increased the manufacture difficulty, possibly will enhance the cost. After optimized analysis, we have the necessity to carry on the flexure analysis for certain models to confirm the security of these models.Then, the models displayed good in the optimization design analysis are carried on the dynamic analysis, including modal analysis, earthquake spectrum analysis and earthquake wave transient analysis. Through analysis about earthquake responds of these models, makes the summary of their earthquake resistance abilities: the overhead crossing structure's cross neutral and support place present the biggest stress frequently, and this controls the seismic design; when carries on the intensity design, should simultaneously consider the structure's biggest stress and the structure's amount of deflection size; according to the section form, the triangle section truss has the best earthquake resistance performance, next is the trapezoid, the rectangular structure is worst, regarding the homogeneous section form's constant section truss and the variable cross-section truss, the earthquake resistance performance is similar, but the variable cross-section form even more saves the material, artistic.Finally, carries on the preliminary analysis to the truss overhead crossing structure's supports, has made the preliminary understanding to its stress situation and the stress distribution, and discovers support's several hazard points. In the end, the article summaries research contents and conclusions, and proposes some key questions should be paid attention in the next step work.