预应力筋局部锈蚀断裂混凝土梁抗弯性能试验研究

Experimental research for flexural behavior on concrete beams with local corrosion fracture of strands

为了研究钢绞线腐蚀断裂对后张预应力混凝土梁受弯性能的影响,制作5片混凝土梁,在不同部位进行电化学快速腐蚀使钢绞线发生局部断裂,然后对其进行静载试验,研究钢绞线局部断裂对混凝土梁裂缝扩展、挠度变形、破坏模式和极限承载力的影响,进而探讨局部断裂的混凝土梁抗弯承载力计算分析方法和抗弯性能数值模拟方法。研究结果表明:预应力筋局部锈蚀断裂对开裂荷载影响较小,但导致构件裂缝分布发生改变,裂缝数量减小,裂缝高度不均匀性明显;构件的破坏形式由断筋局部损伤及对应区域的截面内力共同决定,若断口处弯矩较大,则很可能引起少筋破坏;反之,钢绞线断裂对破坏形式影响较小;钢绞线断裂引起混凝土梁刚度减小,其减小程度与钢绞线断裂的位置相关,钢绞线断裂在端部锚固区对梁的刚度影响很小,从锚固区到弯剪区到纯弯段,刚度减小依次增大;构件极限承载能力受钢绞线断裂位置影响,钢绞线断裂位置越靠近跨中,其抗弯承载力减小越明显。

In order to study the degradation bending property of the post tensioned prestressed concrete beam with the corroded and fractured strand,five kinds of beams were manufactured.An accelerated corrosion test was used to obtain different locally corroded and fractured strands,then all beams were subjected to static load test.The influences of local breakage of steel strands on the crack propagation,deflection deformation,failure mode and ultimate bearing capacity of concrete beams were studied.The calculation method of bending capacity of local fractured concrete beams and numerical simulation method of bending performance were discussed.The results show that the local corrosion fracture of the prestressed tendon has little effect on the cracking load,but it leads to the change of the crack distribution of the component,the decrease of the number of cracks,and the inhomogeneity of the crack height.The failure mode of the beam is determined by the local damage of the broken strand and the internal force of the section in the corresponding region.If the moment at the fracture is large,it causes less rib damage.Conversely,the breakage of the strand has little effect on the damage mode.The stiffness of the concrete beam is degraded due to fracture of the strand,and the degree of degradation is related to the location of the strand fracture.Strand fracture has little effect on the stiffness of the beam at the end anchorage zone,but the stiffness degradation is gradually increased from the anchorage zone to the bending shear zone and then to the purely curved zone.The ultimate load-carrying capacity of the component is affected by the breaking position of the strand.When the fracture location of the steel strand is closer to the middle of the span,the bending capacity is more deteriorated.