钢-混凝土组合梁加宽混凝土旧桥技术中组合横梁界面受力性能研究

在钢-混凝土组合梁加宽旧桥技术中,旧桥混凝土边梁与新加宽的钢-混凝土组合梁间的横向连接采用钢-混凝土组合横梁的形式,这种横梁形式较为新颖,目前相关试验研究尚未有报道。对6个钢-混凝土组合横梁进行试验研究,通过采用目前已有的新老混凝土植筋界面承载力计算方法对试验结果进行对比计算。研究结果表明:组合横梁界面的破坏模式为新老混凝土界面破坏,钢-混凝土界面没有任何破坏特征;新老混凝土界面黏结破坏以前,新老混凝土之间几乎没有滑移,整体性很强;新老混凝土界面黏结破坏以后,界面剪力主要由植筋承担,试件延性良好。针对钢-混凝土组合梁加宽旧桥技术中组合横梁的破坏模式,采用合理的材料本构关系,提出三阶段界面受力模型,理论方法计算结果与试验值吻合良好。通过理论分析确定界面的破坏机理:新老混凝土界面的极限抗剪强度由混凝土强度,界面粗糙程度和摩擦系数共同确定,界面正应力的存在有利于极限抗剪强度的提高;新老混凝土界面的残余抗剪强度主要由界面植筋提供,植筋率和植筋屈服强度是主要影响因素。最后,提出适用于实际工程的设计方法。

Mechanical behavior of the interface of composite cross beam in old concrete bridges widened with steel-concrete composite beam

In old concrete bridges widened with steel-concrete composite beams,the connection is accomplished by using a composite cross beam.There has been no experimental study on the mechanical behavior of such composite cross beams.Six specimens were tested and based on existing methods,the shear strength of interface of old and new concrete was calculated.The results showed that shear failure of the interface of old and new concrete is the cause of failure of composite cross beam in old concrete bridges widened with steel-concrete composite beams.There was nearly no slip between old and new concrete before bonding failure of the interface.The interface of old and new concrete had good ductility and high strength.Based on the constitutive law of the materials,a three-stage mechanical model was proposed for the interface of old and new concrete.The load-slip relationship was also predicted.Comparison between analytical and experimental results showed that the analytical method has enough precision.The ultimate shear strength of the interface was determined by strength of concrete,rough degree of interface,and friction coefficient.The normal stress could increase the ultimate shear strength of the interface.The residual shear strength of the interface was determined by the embedded bars,and the ratio and yielding strength of the embedded bars were the main influence factors.The design method was proposed.