直缝焊接钢管与混凝土界面黏结性能试验研究

EXPERIMENTAL RESEARCH ON INTERFACE BOND PERFORMANCES BETWEEN LSAW STEEL PIPES AND CONCRETE

大跨越输电杆塔工程中钢管混凝土结构设计对其界面黏结性能提出了更高的要求。为研究直缝焊接钢管与混凝土界面黏结性能,采用正交试验方法设计了9个钢管混凝土试件的推出试验。研究了直缝焊接钢管与混凝土界面黏结机理和黏结应力分布规律,分析了各因素影响黏结强度的主次关系及变化规律,并基于正交试验分析结果提出了优化的黏结强度经验计算式。试验结果表明:黏结应力-滑移曲线包括胶结段、非线性初滑移段和滑移段,在胶结段、非线性初滑移段曲线呈相似上升趋势,在滑移段曲线出现3种发展趋势,即Ⅰ-1、Ⅰ-2和Ⅱ类;Ⅰ-1类曲线下降后保持水平,Ⅰ-2类曲线下降后呈二次上升,Ⅱ类曲线形成拐点后缓慢上升,其3种发展趋势主要由直缝焊接钢管的制作“宏观偏差”所导致;影响胶结强度和极限黏结强度的因素主次关系均为钢管径厚比、混凝土强度、界面黏结长度,胶结强度和极限黏结强度随钢管径厚比增大而显著降低,随混凝土强度提高而增大;试件两端处黏结应力存在随荷载增大而减小的现象,揭示了黏结界面剥离从两端向中部发展的破坏机制;与其他学者实测数据对比证明本文黏结强度计算式有一定的可参考性。

In structure design of concrete-filled steel tube(CFST)structure of long-span transmission towers,the higher requirements were put forward for the interface bond performance.To study the interface bond performances between LSAW(longitudinally Submerged Arc Welding)steel pipes and concrete,push-out tests based on orthogonal test principles were conducted on nine CFST specimens.The bond mechanisms and distribution laws of bond stress between LSAW steel pipes and concrete were studied.The main and secondary relations and influencing laws of parameters on the bond strength were analyzed.The optimized empirical formulas of bond strength were proposed based on the analysis of orthogonal tests.Test results indicated that curves of bond stress and slip consisted of the adhesive stage,nonlinear initial sliding stage and sliding stage.All curves had a similar rising tendency at the adhesive stage and nonlinear initial sliding stage.And there were three kinds of tendencies at sliding stage,namely,type I-1,Ⅰ-2 andⅡ.The type I-1 curve firstly decreased and then kept it stable.The typeⅠ-2 curve firstly decreased and then possessed a secondary rising branch.The type II curve continued to ascend slowly at the sliding stage.Three kinds of curve tendencies were mainly caused by macro-manufacturing deviations of the LSAW steel pipes.The factors that influenced adhesive strength and ultimate bond strength both were in order of diameter-thickness ratio of steel pipes,concrete strength and interface bond length in terms of importance.The adhesive strength and ultimate bond strength bothdecreased significantly with the increase of diameter-thickness ratios of steel pipes,but increased with the increase of concrete strength.The bond stress at two ends of specimens decreased with the increase of loads,which revealed the failure mechanism that interface peeled off from the both ends to the middle part.A comparison with other literatures verified that the optimized calculation formulas of bond strength had reliability.