长期荷载作用卸载后的锈蚀钢-混凝土组合梁抗弯性能试验研究

Experimental Study on Bending Property of Corroded Steel-concrete Composite Beam after Long-term Loading

为研究长期荷载卸载后锈蚀简支组合梁的抗弯性能,进行了6片钢-混凝土简支组合梁的抗弯性能试验,采用电化学腐蚀方法对组合梁进行加速腐蚀,使用5%浓度的NaCl溶液作为电解液。对钢梁和钢筋进行防腐处理,以达到仅使试件指定部位生锈的目的。腐蚀速率通过调节腐蚀电流来控制。在腐蚀和长期荷载作用200天后卸载,测试组合梁的抗弯性能。研究了腐蚀与长期荷载共同作用对组合梁挠度、滑移、应变及极限承载力的影响。试验结果表明:(1)在长期荷载作用下,组合梁的截面应变和界面相对滑移前期得到增长,但对试件的最大应变和最大滑移值影响甚微。(2)栓钉锈蚀导致组合梁整体刚度降低,延性变差;(3)经过栓钉锈蚀,组合梁的抗剪连接程度下降,混凝土板与钢梁工作协同性变差,组合梁抗剪连接程度降低导致滑移量增长,钢材塑性得不到充分发挥,试件的受弯承载力降低;(4)栓钉锈蚀导致栓钉与混凝土的有效接触面积减少,截面组合程度减弱,混凝土压应力提高,应变增大;(5)栓钉锈蚀导致栓钉抗剪切变形能力减弱,试件的滑移增长速率明显增大,相同荷载下,栓钉锈蚀率越高,组合梁相对滑移的最大值越大;(6)栓钉锈蚀更严重的组合梁在同一荷载等级下应变量更大。

In order to study the flexural behavior of corroded simply supported composite beams after long-term loading, the flexural behavior test on 6 steel-concrete simply supported composite beams are carried out. Electrochemical corrosion method is used to accelerate corrosion of the composite beams with 5% concentration of NaCl solution as the electrolyte. The steel beams and rebars are treated with antiseptic treatment to achieve the purpose of rusting at the designated parts of the specimens. The corrosion rate is controlled by adjusting the corrosion current. After 200 d of corrosion and long-term loading, the bending resistance of the composite beams is tested. The influences of corrosion and long-term loads on the deflection, slip, strain and ultimate bearing capacity of the composite beams are studied. The experimental result shows that(1) under the long-term load, the cross-section strain and the interface relative slip of the composite beams are increased at early stage, but it has little influence on the maximum strain and the maximum slip value;(2) the integral stiffness of the composite beams is reduced and the ductility is poor due to the corrosion of the studs;(3) after the corrosion of studs, the shear connection degree of the composite beams is decreased, the working synergy between concrete slab and steel beam becomes worse, the slip quantity increases due to the decrease of the shear connection degree of the composite beams, the plasticity of steel is not fully brought into play, and the flexural capacity of the specimens is reduced;(4) the corrosion of the studs leads to the decrease of the effective contact area between the studs and the concrete, of the cross-section combination is decreased, the compression stress and the strain of the concrete are increased;(5) the resistance to shear deformation of the studs is weakened due to the corrosion of the studs,the higher the corrosion rate of the studs under the same load, the greater the maximum relative slip of the composite beam;(6) the strain of the composite beams with more severe corrosion of studs is larger under the same load grade.