折线先张法预应力工字梁受力性能试验

Experimental on Mechanical Behavior of Broken Line Pretensioned I-beam

为克服直线先张法的预应力筋不能弯折而使桥梁跨径受限,以30 m折线先张法预应力混凝土工字梁为研究对象,研究折线先张法工字梁在弹塑性阶段的应力、变形、裂缝和承载能力,进行理论计算及静载破坏试验,并利用Midas Civil有限元软件的PSC程序计算,对比静载试验与有限元模型。结果表明:在弹性阶段,荷载与混凝土应变、挠度的试验曲线均呈线性变化;跨中截面和3L/8截面(L为工字梁跨径)为梁体应变的危险截面;加载至1~1.4倍的开裂荷载时,L/4、L/2截面挠度变化仍基本处于线性增大状态,斜率约为按弹性阶段计算的2倍;当出现第一条裂缝后,随着荷载的增加,裂缝继续向工字梁腹板延伸,跨中底板及腹板附近出现新裂缝,但未出现梁端剪切裂缝或破损现象。预应力混凝土工字梁的应力、挠度校验系数均小于1,表明折线先张法工字梁的抗弯和抗剪承载能力、强度、刚度、抗裂性均满足设计及规范要求。

In order to overcome the straight line first tensioning prestressed reinforcement can not bend and make the limited bridge spans,to 30 m line first tensioning prestressed concrete I-beam as the research object,research first line tensioning I-beam in elastic-plastic stage of the stress,deformation,cracks and carrying capacity,through theoretical calculation and static load test,PSC program of Midas Civil finite element software was used to compare static load test and finite element model.The results show that in the elastic stage,The test curves of load,concrete strain and deflection change linearly.Midspan section and 3L/8 section(L is the span of I-beam)are dangerous sections of beam body strain;When the cracking load is 1~1.4 times,the deflection of L/4 and L/2 sections is still in a linear increase state,and the slope is about twice that calculated according to the elastic stage.After the first crack appears,with the increase of load,the crack continues to extend to the I-beam web,and new cracks appear near the mid span bottom plate and web,but there is no shear crack or damage at the beam end.The stress and deflection check coefficients of the beam end concrete are less than 1,indicating that the bending and shear bearing capacity,strength,stiffness and crack resistance of the broken line pretensioned I-beam meet the requirements of the design and specifications.