LIGHT-WEIGHT PRECAST PC BOX GIRDER BRIDGE USING CFRP CONTINUOUS GRIDS

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For the design of prestressed concrete box girder briges, it is necessary to lighten the girder webs since severe limit is set to the span length by the weight of girder. A new structural systems is proposed herein as the light weight web which consists of tow element. One is a framed structure which can resist the bending moment and axial force. And the other is a thin web reinforced by the two-dimensional carbon fiber continuous reinforcement (CFRP grids) which can resist the shear force for beams of bending moment and punching shear for slabs.This study aims at providing some fundamental informations on deveropment of the above mentioned hybrid structual system.(1) Numerical analysis of PC box girder section by using hybrid structural system was carried out. From the result, it can be seen that the weight of web can be reduced by 50% comparing the traditional type of web section.(2) A loading test was carried out to evaluate the effect of CFRP grids and ultimate strength of beams and slabs reinforced with CFRP grids. From test results, it can be summarized as follows ;(1)The crack width and distribution of concrete beams depend on the mesh of CFRP grids.(2) Ultimate shear strength of concrete beam and bending strength of concrete slab, which are reinforced with CFRPgrids, can be evaluated by the code equations of current design standards.(3) For punching shear of concrete slabs reinforced with CFRP grids, the current design equations may be overestimate the actural ultimate strength. So, it can be evaluated their punching shear strength by using the equations modified with the ratio of Young's modulus.