Mechanical Characteristics Of Plate- Truss Composite Steel Girder Bridge And Structural Analysis Of Integral Joints Details

In this paper, Midas Civil software is used to establish a spatial finite element model of the whole bridge based on the mixed plate-beam element for double-track railway plate- truss composite steel girder bridge, researching and analysing the mechanical characteristics of lower supported type plate-truss composite steel girder under different loading conditions. Then the article uses finite element analysis software-Ansys Workbench to make a more in-depth analysis for the integral joints on the stress distribution,the loss of high-strength bolt preload force and contact stress from the constructional details. This primarily work and achievements of the paper is as follows:1. The SPB plate-beam hybrid element method considering rigid zone effect is used to establish finite element model of the whole bridge for steel truss girder bridge. The mechanical characteristics of the bridge are analyzed under different conditions(constant load, the most unfavorable live load, the main stress, the main and additional stress). The calculated results showed: the whole bridge stress is reasonable, the strength and the rigidity satisfied requirements of railway bridge design specification.2. Local analysis is done for the bottom chord bar integral joints of main truss under the main loads. The results shows: The gusset plate value at stress concentration point with considering high strength bolt is smaller than without considering. The degree of stress concentration is higher and the equivalent stress is larger at arc parts of gusset plate, joints between gusset plate and floor, and intersection between gusset plate and longitudinal ribs. But both of them didn’t exceed the material yield strength.3. The loss of high-strength bolt pretension is analyzed of internal and external lateral gusset plates,and explains what are the real reasons for improving the bolt pre-tension when the high-strength bolt is tightened. Meanwhile,it provides a reference for tightening bolts at different locations.4. The stress state between the contact surface is studied on the friction stress, compressive stress, sliding distance and penetration distance,from which obtaines the distribution regularity of frictional stress and compressive stress. Judging by the sliding distance,we can draw a conclusion that a phenomenon of "trip slip" between the plates is produced,which making the gusset plate internal force redistribution occurred.5. By checking the support reactions and all the bars’ inner force,we can get the conclusions as follows: The local analysis model with considering high strength bolt well simulated real force state of the integral joints,which is consistent with the overall results. And it reflects a general model that does not have phenomena such as stress concentration and stress transfer in high-strength bolt...