多点锚固体外无粘结CFRP预应力加固RC梁的抗弯性能

在梁侧或梁底用波形齿横向张拉CFRP片材并锚固的体外预应力加固混凝土结构技术,对3根完全相同的7m跨T形截面梁进行加固:其中2根梁侧面加固;1根梁底部加固。试验表明:多点锚固体外无粘结CFRP预应力可以依据构件的弯矩来调整各段的加固量从而更有效的利用CFRP材料的高强性能;梁底与梁侧加固对提高构件的抗弯刚度差别不大;波形齿能彻底解决预应力CFRP片材的锚固问题。以该3根加固梁的试验结果为基础,提出了梁体极限状态下塑性绞区长度的体外无粘结预应力碳纤维加固受弯构件的抗弯承载力公式,以及考虑二次效应的有效惯性矩法的挠曲变形的计算公式,通过与试验值的对比分析可知,所提出的方法可供设计参考使用。

The flexural properties of RC beams strengthened with multi-pointsachored externally unbonded prestressed CFRP sheets

Three same 7 m span reinforced concrete T-beams were strengthened with an external prestressed strengthening technique. CFRP (carbon fiber reinforced polymer) sheets were not affixed to the beams, but laterally pulled by WSGG (wave-shaped-gear-grip) anchor and gripped at the bottom or two sides of the beams. Two beams were strengthened at two sides, while the other one beam was strengthened at bottom. The flexural propterty test results indicate that the section of the CFRP sheets can be adjusted according to the moment of the beam and the high-strength properties of CFRP materials can be efficiently used. There is no difference in improving the flexural rigidity of the beams either strengthened at two sides or at bottom. The WSGG can anchor the prestressed CFRP sheets well. Based on the test results, we proposed an equation for calculating ultimate load and deflection of beams which are strengthen by externally unbonded prestressed CFRP sheets, and a flexural capacity formula according to the beam plastic hinge zone length limit state of the strengthened beams. And the formula for calculation deflection is derived by considering secondary effects of inertia. Compared with the experimental results, the above formulas are verified and can be used for design.