钢-混组合桥梁栓钉腐蚀疲劳失效及力学性能退化机理试验研究

Experimental Research on Corrosion-Fatigue Failure and Properties Degradation Mechanism of Stud in Steel-Concrete Composite Bridges

腐蚀环境中钢-混组合桥梁的栓钉连接件可能因腐蚀-疲劳耦合作用而劣化,为此设计制作3组10个栓钉推出试件,分别进行腐蚀后的静力、疲劳性能试验和腐蚀-疲劳耦合试验,研究栓钉的腐蚀-疲劳失效及力学性能退化机理。结果表明:腐蚀作用使得栓钉抗剪刚度显著退化;腐蚀-疲劳耦合作用下栓钉疲劳寿命明显低于腐蚀后疲劳寿命;栓钉初始疲劳裂纹产生于钉杆靠近焊趾截面的剪力作用侧,以剪切裂纹扩展为主,当疲劳裂纹或腐蚀疲劳裂纹发展至约1/2栓钉直径后,栓钉在拉-剪组合应力作用下断裂;影响栓钉损伤发展速率的主要因素为荷载比、腐蚀速率及腐蚀-疲劳耦合作用;腐蚀-疲劳耦合作用下栓钉抗剪刚度退化速度大于疲劳单独作用下,抗剪刚度退化包括快速退化和缓慢退化2个阶段,前一阶段约占栓钉腐蚀疲劳寿命的20%。

The stud connectors of steel-concrete composite bridges in corrosive environments may deteriorate due to corrosion-fatigue coupling effect.Three groups of 10 stud push-out specimens were designed and fabricated,and the static and fatigue performance tests and corrosion-fatigue coupling tests were carried out respectively to study the corrosion-fatigue failure and mechanical property degradation mechanism of stud.The results show that corrosion significantly degrades the shear stiffness of the stud;the fatigue life of stud under corrosion-fatigue coupling effect is significantly lower than that after corrosion;the fatigue crack of the stud originates from the stud rod section near the weld toe section on the shear action side,and mainly propagates as a shear crack.When the fatigue crack or corrosion-fatigue crack develops to about 1/2 of the stud diameter,the stud fractures under the combined tensile-shear stress;the main factors affecting stud’s damage evolution rate are load ratio,corrosion rate,and corrosion-fatigue coupling effect;the degradation rate of shear stiffness of the stud under the corrosion-fatigue coupling effect is greater than that of the fatigue alone,and the degradation of the shear stiffness includes two stages:rapid degradation and slow degradation,and the former stage accounts for about 20%of the corrosion fatigue life of the stud.