钢-UHPC桥面板湿接缝负弯矩试验研究

Experimental study on negative bending moment of wet joint of steelUHPC bridge deck

某斜拉桥的次边跨和中跨的桥面板采用8 mm平钢板+15 cm UHPC层+PBL剪力键的新型组合体系。桥面板预制段UHPC依靠阶梯式燕尾榫湿接缝连接。为研究该组合桥面板湿接缝的负弯矩静力性能,制作足尺模型试件进行试验。通过施加荷载,测量各级荷载下桥面板试件的位移、应变,并观测裂缝,获得荷载-位移曲线、荷载-应变曲线、裂纹发展规律和破坏形态。研究结果表明:阶梯式燕尾榫湿接头接缝处的抗裂能力、承载能力与湿接头非接缝处性能大体相当,开裂后其刚度逐渐退化;裂纹宽度0.2 mm时,荷载关系从线性变为非线性;到达极限荷载后,桥面板仍保持良好的延性;PBL剪力键能确保钢与UHPC形成整体,保证两者共同变形;桥面板裂纹主要集中在现浇段,多而密;跨中截面处钢筋和混凝土的应变均大于其他部位的,试件破坏以跨中裂纹宽度急剧增加为标志。

The deck of the second side span and middle span of a cable-stayed bridge adopts a new combination system of "8 mm flat steel plate + 15 cm UHPC layer + PBL shear connection". The UHPC of the prefabricated section of the bridge deck is connected by stepped dovetail wet joints. In order to study the static negative bending moment performance of the wet joint of the composite bridge deck,full-scale model specimen was made for the test. Through the application of load,the displacement and strain of bridge deck specimens under all levels of load were measured and the cracks were observed. The the load-displacement curve,load-strain curve,crack development law and failure pattern were obtained. The results show that the crack resistance and bearing capacity of the stepped dovetail wet joints are about the same as those of the non-joints of the wet joints. The stiffness gradually deteriorates after cracking,When the crack width is 0.2 mm,the relation between crack and load changes from linear to nonlinear. The bridge deck still maintains good ductility after reaching the ultimate load. PBL shear connection can ensure the integrity and common deformation of steel and UHPC. The numerous and dense cracks of bridge deck are mainly concentrated in the cast-in-place section. If the strain of steel bar and concrete in the middle section of the span are larger than that in other parts,the failure of the specimen will be marked by the sharp increase of crack width in the middle of the span.