Beijing-shanghai High-speed Dashengguan Changjiang River Bridge Node Force Performance

The abuilding Nanjing Dashengguan Yangzi River Bridge (NJB) of Beijing-Shanghai high speed railway is a continuous steel truss arch bridge with 6 spans, 3 principle trusses, 6 railway lines, and integral ballast deck. The floor system of the bridge is multiple cross girder system. The structure of the low chord joints of the main truss is rather complicated. On the basis of the analysis of whole NJB, local analysis was applied the joint with consideration of structural details,the main contents are as follows:1. After studing the common methods of local analysis ,the "direct modeling" was chosen as the method of joint local analysis .By the Saint-Venant Principle,the principle and method of interception was proposed,and the method of application of inpintemal force boundary of joint on finite element model of joint was proposed.2. Considering structure details, refined finite element models of "joint E7 " and "joint ME9" were established using shell element.3. The method of defining the most possible unfavorable processing condition of joints was proposed,and that method was used to define the most possible unfavorable processing condition of "joint E7" and "joint ME9".4. The local analysis was done on the several combinations of loads as follows: combination of dead load and the chosen most possible unfavorable processing condition;combination of dead load,the chosen most possible unfavorable processing condition and additional strength.The results showed the total stress level of gusset plate,big cross girder web plate and main link weld seam was low.The degree of stress concentration and equivalent value stress were high at the top of juncture of big cross girder web plate and low chord girder web plate,and in the juncture of vertical web member'end and gusset plate, and in the juncture of inclined web member'end and gusset plate,but equivalent value stress didn't exceed the material yield stress.5. Compared with the results of the integral analysis and local analysis in the same load case, the conclusion was obtained: the stress concentration phenomenon on the end of the bar connected with the joint was quite improved in the local analysis compared with the integral analysis, which demonstrated the structural measures ,such as heightening, thickening and strengthening the joint ,were very effective.So the local analysis is necessary.