剪跨比对钢管混凝土组合桥墩抗震性能影响试验研究

钢管混凝土组合桥墩是一种以圆钢管为钢骨的新型钢-混凝土组合桥墩,具有良好的应用前景.通过3个组合桥墩试件的拟静力试验,研究了钢管混凝土组合桥墩的抗震性能和抗剪强度,分析了剪跨比对组合桥墩破坏形态、位移延性、刚度退化、滞回耗能和残余位移的影响.试验结果表明:剪跨比是决定组合桥墩破坏形态的关键因素,3个不同剪跨比的组合桥墩试件发生的破坏模式有剪切斜压破坏、弯剪破坏和弯曲破坏3类;3个组合桥墩试件的滞回曲线均比较饱满、稳定,无明显的捏缩、滑移现象;随着剪跨比的增大,试件的变形能力和耗能特性得到改善,刚度退化减慢,残余位移减小;不同剪跨比的组合桥墩试件均具有良好的变形能力,满足工程实践对位移延性系数和极限位移角的要求;对组合桥墩的抗剪强度计算公式进行了有益探讨,研究成果可为组合桥墩的抗震设计提供参考.

Experimental study for effects of shear span ratio on seismic performance of concrete filled steel tube (CFST) composite bridge columns

Concrete-filled steel tube(CFST) composite bridge column, which is formed by pre-embedding a steel tube into a reinforced concrete bridge column, is an innovative type of steel-concrete composite bridge column, and has prosperous potential in widespread application. Quasi-static tests of three specimens are conducted to investigate the seismic behavior and shear strength of CFST composite bridge columns. The influences of shear span ratio on failure patterns, displacement ductility, stiffness degradation, hysteretic energy dissipation and residual displacement of CFST composite bridge columns are discussed. Test results indicate that the shear span ratio is the critical factor in determining the failure patterns of CFST composite bridge columns. Three specimens with different shear span ratios suffer from shear diagonal-compression, flexural-shear and flexural failure, respectively. The hysteretic curves of the tested specimens show good plumpness and stability, without any noticeable pinching and slippage effect. With the increase of shear span ratio, the deformation ability and energy dissipation capacity are improved, while the residual displacement and the rate of stiffness degradation decrease. Three specimens with different shear span ratios all exhibit favorable deformation ability, satisfying the requirements of displacement ductility factor and ultimate drift ratio specified in engineering practice. At last, some beneficial discussions are made based on the shear strength computational formula of CFST composite bridge column. Research findings can provide reference for seismic-resistant design of CFST composite bridge columns.