Experimental Research On Static And Dynamic Responses Of Bridge Longitudinal Truss With Typical Welded Details

This thesis aims to experimentally study static and dynamic responses of bridge longitudinal truss with typical welded details for the purpose of providing experimental data to the structural FE modeling by considering the local detailed feature such as the stress concentration at the welded components. The work involved in the thesis was supported by the National Science Foundation of China via the project"Multi-scale damage modeling and failure behavior simulation of long span structure"(No: 50278017) and others.The experimental research was carried out on the basis of a reduced scale specimen, with the scale of 1:5 (4.2m×1.32m, four segments of the truss), as a part of standard segments of the Tsing Ma Bridge longitudinal truss with typical welded details. The experimental measurement of the specimen under static and dynamic loading in the whole structure and local details for hot-spot stress distribution has been done in the thesis. The emphases of the measurement of the specimen's response under several groups of loading and boundary conditions were put on welded details the specimen. Experiments included the measurement of dynamic properties and responses of the specimen under different boundary conditions and static and dynamic loading respectively. The measuring plans were firstly studied on the basis of primary FEM analysis and pre-test in which feasible and detailed option for the efficient test was provided. A lot of measuring spots for strain distribution were lay on the hot spot area of welded details. Then, the strain distribution of the specimen and the stress concentration factor on the toe of welds were obtained, and the distributed rule of the structural and local stresses was analyzed. Modal parameters (frequencies and vibration modes) were also obtained by modal test.It can be concluded from the results of the analyses on experimental data that, 1) Three types of material parameters, i.e. parameter of structural steel, solder and boundary area of welding, should be tested and then adopted in the FE modeling of the truss structure with typical welded details for the accurate evaluation of the material description of the tested specimen; 2) the typical details in the longitudinal truss showed the concentration to a limited area on the toe of a dominate weld at the intersection among the upper chord or bottom chord, diagonal and the gusset plates. These concentrated areas should be paid more attentions in the FE modeling of the bridge truss in considering the local detailed feature of the welded components. 3) The behavior of local stress concentration depends on not only the welding details nearby, but also the type and location of loading on the structure and the boundary conditions. 4) The extent of the concentration seems...