内嵌CFRP筋/片加固木梁受弯性能试验研究

Experimental study on flexural behavior of strengthening timber beams with near surface mounted CFRP bars and strips

为研究内嵌CFRP筋/片加固木梁的受弯性能,制作5根底面中心内嵌CFRP筋加固试件,3根侧面内嵌CFRP筋加固试件,6根底面中心内嵌CFRP片加固试件以及3根未加固的对比试件,对其进行三分点静载试验。试验参数包括:CFRP筋/片,内嵌位置(底面或侧面),CFRP筋/片数量(1根或2根)、是否采用附加锚固措施(U形铁钉或CFRP布U形箍)、底面是否粘贴CFRP布等。研究表明,内嵌CFRP筋/片加固试件的受弯承载力较未加固试件明显提高,提高幅度为14%～85%,平均提高39%;破坏位移亦平均提高32%。内嵌CFRP筋加固试件的初始弯曲刚度均大于对比试件,而内嵌CFRP片加固试件由于底面开槽面积较大其初始弯曲刚度未见提高。内嵌CFRP筋加固试件的跨中截面应变随荷载增加仍基本符合平截面假定,而内嵌CFRP片加固木梁的跨中截面应变变化与平截面假定存在一定差距。增加内嵌CFRP筋/片的数量及端部采用U形铁钉锚固措施对提高加固木梁承载力的作用不明显;而在加固木梁底面粘贴一层CFRP布可显著提高其加固效果。

To learn the effectiveness of flexural strengthening of timber beams with near surface mounted CFRP,17 timber beams were experimentally studied.There were three unstrengthened reference beams and 14 beams strengthened with near surface mounted（NSM） CFRP bars or strips.The test parameters included the type of CFRP,the position of NSM（tension face or the bottom of the sides）,the number of CFRP bars and strips（1 or 2）,additional anchoring of NSM CFRP bars and strips（U iron nail or CFRP U stirrup）,and additional CFRP sheet bonded to the tension face.The test results show that the ultimate flexural strength of the timber beams are increased by 14%～85% with an average of 39% due to NSM CFRP bar or strip strengthening.Their ultimate deflections are increased by an average of 32%.The initial flexural stiffness of the timber beams is also enhanced by NSM CFRP bar strengthening,while this increase is not significant by NSM CFRP strip strengthening.The strain distribution along the height of the NSM CFRP bars strengthened beams at middle-span is nearly linear during the whole loading process,while there is some different by NSM CFRP strip strengthening.This preliminary study shows that neither an increase of the number of CFRP bars/strips nor the addition of extra anchoring can significantly enhance the bending capacity of strengthened beams,but bonding an additional CFRP sheet to the tension face of the NSM strengthened beams can.