Analysis Of Mechanical Behavior Of Whole Bridge And Key Parts For A Long-Span Railway Continuous Steel Truss Girder Bridge

The DLY bridge is a through6-span continuous two-line railway steel truss girder bridge with variable height. The bridge span arrangement is120+4×180+120m. The floor system used steel orthotropic monolithic deck system with dense crossbeams. This acrticle used spacial finite element analysis method for the whole bridge and fine finite element analysis method for the key parts of the floor system, systematically analysed the mechanical behaviors of DLY bridge. The major work and results were as follows:1. The spacial plate-beam method(SPB) was used to establish a special FEA model for the whole bridge of DLY Bridge, the mechanical characteristics and force performances of the bridge under dead load、 worst-case live load and combination of main loads were analysed.The main analysis results showed:the whole bridge loading was reasonable, and the need of stiffness was met.2. The two internode under local parts where the longitudinal beam and cross beam are connected in the floor system was chosed to establish a fine FEA locality model with spacial plate and shell elements.The forced state of these local parts under dead load、worst-case live load and combination of main loads was analysed.The results showed:the stress of most area was not large, but the maximum principal tensile stress and the maximum Mises equivalent stress of E40middle support crossbeam and E12joint crossbeam was comparatively large, which were above allowable stress.3. Three improvement proposals were made based on the original program to improve the local forced state for the connection in floor stytem of DLY Bridge:the thickness of the support crossbeam web and diaphragm was rised; the section type of the middle support crossbeam was changed from box type to T type; the constructional details for the connections of the support crossbeam were changed.4. The mechanical behaviors of the above three improved structures under dead load、worst-case live load and combination of main loads were calculated and comparatively analysed. All of them could improve the local forced state of the orthotropic plate connection to some degrees. However, rising the thickness of the crossbeam web and changing the section types of the middle support crossbeam were the most effective. Therefoce, changing the section types of the middle support crossbeam from box type to T type and rising the thickness of the support crossbeam web from16mm to24mm were recommended.The results of this article had applied to DLY Bridge, and had important reference value to the design of other similar bridges.This paper has121graphs,31tables and63references.