U型锚固对BFRP加固混凝土梁作用效果研究

Study on Effect of U Anchorages on Concrete Beams Reinforced by BFRP

目的研究端部U型锚固和沿全梁U型锚固对玄武岩纤维布加固钢筋混凝土梁的作用效果.方法以两种U型锚固方式的BFRP加固钢筋混凝土试验梁为研究对象,采用扩展有限元模拟混凝土裂缝扩展,利用界面粘结单元计算BFRP与混凝土之间的界面应力,分析两种U型锚固形式下BFRP加固混凝土梁的裂缝扩展、界面应力、BFRP应力以及加固梁的失效机理.结果端部U型锚固下BFRP加固梁的极限承载力高于全梁U型锚固的加固梁,随着荷载的增加,裂缝位置的局部高应力向两侧移动,界面应力和BFRP布的拉应力沿全梁分布更均匀,加固梁易产生界面剥离破坏;而全梁锚固的加固梁U型箍间裂缝位置处的BFRP局部应力增加迅速,易发生局部BFRP布拉断破坏.结论当BFRP加固混凝土梁只产生剪切裂缝时,全梁U型锚固的加固效果好于端部U型锚固方式,全梁U型锚固下BFRP加固混凝土梁的承载力更高、变形更小.

In order to study the effect of two types of U-stirrups anchored at the end of the beam and along the whole beam on the reinforced concrete beams strengthened by basalt fiber reinforced plastic(BFRP),two specimens from the experiment are specified as the study objects in this paper.Through applying Extended Finite Element to simulate concrete cracking and Cohesive Zone Element to calculate the bonding stress between BFRP and concrete,the crack propagation,interfacial stress,BFRP stress and failure mechanism of BFRP strengthened concrete beams are analyzed.The results show that the ultimate bearing capacity of the BFRP strengthened beam with U-stirrup at two ends is higher than that of the U-stirrup along the whole beam.With the increase of load,the locally high stress at the crack position moves to both sides,and the interfacial stress and the tensile stress of BFRP are more evenly distributed along the whole beam,which can produce debonding failure on the interface.However,the local stress of BFRP increases rapidly at the crack position between two U-stirrups for the whole beam anchorage,which can generate local BFRP rupture.When there are only shear cracks developed in BFRP reinforced concrete beams,the strengthening effect of the whole beam U-anchorage is better than that of the end U-anchorage.In this case,BFRP reinforced concrete beam is of higher loading capacity and smaller deformation.