Studies On Static And Dynamic Property Of Multi-beam Bridges Retrofitted With Adding Main Girders Or CFRP

With the swift and violent development of communication undertaking, the strengthening and retrofitting of multi-beam bridges becomes a significant task to be confronted with. The strengthening methods of multi-beam bridge may be divided into two types: broaden the moment of sections; improve the structural system of bridge or heighten the transverse connecting between the girders in order to decrease the inner force of the old beams. From these two viewpoints, the strengthening methods of multi-beam bridges with bonded CFRP and adding main girders were compared, and the effect factors were studied.The strengthening principle, construction process, static and dynamic property of adding main girders were analyzed and the analysis methods were discussed. In this paper, the entity cells were adopted to establish the finite element physical model; comparative analysis has been underway from bending deflection, strain to natural vibration frequency and mode shape. Stiffness ratio of newly adding girder and old beams has been underway the parametric analysis, optimization suggestions of newly adding girders were put forward. In this study, 3D cracking reinforced concrete elements were adopted to simulate the behavior of the CFRP bonded concrete beams in the linear and nonlinear ranges, and the results compared with tests were discussed. By the load tests of two 12.6m span beam bridges both before and after strengthened, the variation of static and dynamic property is studied.By FE analysis, the mode frequency and shape were compared, and relations with transverse connections were also discussed. The problems required to be solved in present bridge strengthening were pointed out, and some corresponding advice was given.