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

在预应力混凝土箱梁桥的设计中，由于主梁的自重对跨度长度有很大的限制，因此有必要对主梁腹板进行轻量化。本文提出了一种新的结构体系，即由两个单元组成的轻质腹板。一种是框架结构，可以抵抗弯矩和轴力。另一种是用二维碳纤维连续筋(CFRP网格)加固的薄腹板，可以抵抗板梁的弯矩和冲切剪力。本文的研究旨在为上述混合结构体系的发展提供一些基础资料。(1)采用混合结构体系对PC箱梁截面进行了数值分析。试验结果表明，与传统的腹板截面形式相比，腹板的重量减轻了50%。(2)进行了碳纤维布加固梁、板的加载试验，评价了碳纤维布加固梁、板的极限强度。从试验结果可以看出：(1)混凝土梁的裂缝宽度和分布取决于CFRP格栅的网格。(2)CFRP格栅加固混凝土梁的极限抗剪强度和混凝土板的抗弯强度可以用现行设计标准的规范公式来估算。(3)对于CFRP格栅加固混凝土板的冲切，现有的设计公式可能高估了实际极限强度。因此，可以用杨氏模量率修正后的公式来估算其冲切剪切强度。

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.