预应力CFRP板加固梁的界面应力分析

INTERFAICAL STRESS ANALYSIS OF BEAMS STRENGTHENED WITH A PRESTRESSED CFRP PLATE

CFRP板端应力集中导致的剥离破坏是加固梁破坏的主要形式之一。该文对CFRP板加固梁中的界面应力进行了推导,给出了考虑外荷载、温度变化和预应力等作用的界面应力计算公式,并对板端的最大界面应力计算进行了简化。对CFRP板施加预应力采用了预应力FRP法和梁反拱预应力法。通过算例及参数分析,讨论了不同工况(包括外荷载作用、温度变化、预应力作用等)下的界面应力及CFRP板纵向力。结果显示,采用预应力FRP法和温度的升高显著增加了加固梁的界面应力集中,而梁反拱预应力法引起的界面应力集中相对较小。另外,CFRP板的长度对预应力FRP法引起的最大界面应力没有影响,但梁反拱预应力法引起的最大界面应力随板长增加而减少。而各种工况下的最大界面应力均随板厚度的增加而增加。

The debonding failure caused by the interfacial stress concentrations at the cut-off ends of the CFRP plate is one of the main failure modes of the retrofitted beams. This paper presents an analytical solution to calculate the interfacial stresses in the beams strengthened with a CFRP plate under mechanical loads, thermal loads and prestressing actions. Two simplified equations for the maximum interfacial stresses are given as well. The prestressed FRP strengthening scheme and load-relief jacking scheme are employed to apply prestress to the CFRP plate. An example and the parametric study are employed to investigate the development of interfacial stresses and longitudinal stresses in the CFRP plate under different load cases, including mechanical loads, thermal loads and prestressing actions, etc. Results show the interfacial stress concentrations caused by the load-release jacking scheme is far less than those introduced by prestessed FRP strengthening scheme and thermal change. In addition, the length of the CFRP plate has no infiuencence on the maximum interfacial stresses caused by prestressed FRP strengthening scheme, but the stresses caused by load-relief jacking scheme decreases with the plate length. Moreover, for all the loading cases the maximum interracial stresses increase with the plate thickness.