考虑泥皮及径厚比影响下钢混组合桩的抗弯性能试验研究

Experimental Study on Flexural Behavior of Steel Tubular-concrete Composite Pile Considering Influence of Mud and Radius-thickness Ratio

为研究灌注桩施工过程中残留的泥皮厚度及不同钢管径厚比对钢管混凝土抗弯性能的影响,采用模拟水下浇筑混凝土的方法制备了6根钢管混凝土组合桩试件,对其进行了纯弯试验及截面测量,得到了各试件的弯矩-跨中挠度曲线、弯矩-曲率曲线、受弯承载力及抗弯刚度等.试验结果表明:泥皮的存在会削弱钢混组合桩的抗弯性能,使其抗弯刚度降低5%~25%,极限受弯承载力降低5%~10%,且径厚比越小受泥皮的影响越明显;当泥皮存在时,径厚比的减小使得钢混组合桩受弯承载力及抗弯刚度的提升幅度不如无泥皮状态;存有残留泥皮的钢混组合桩在受弯过程中截面不再符合平截面假定;采用统一理论所计算的抗弯承载力与试验值吻合较好,但随泥皮厚度增长,逐渐较试验值偏大,导致设计预留的安全储备降低;抗弯刚度的计算公式组合系数出现明显下降,组合系数在0.1~0.4左右.

In order to study the influence of residual mud during construction process and steel pipe with different radius-thickness ratio on the flexural behavior of concrete filled steel tube,six steel tubular composite pile specimens were prepared by simulating underwater pouring of concrete for bending experiment and cross-section measurement.Through the test,M-um,M-Φ curves,flexural resistance and stiffness of these specimens were obtained.The test results show that the existence of mud weakens the stiffness and flexural resistance of concrete-filled steel tube by approximately 5%~25%and 5%~10%,respectively.The smaller the radius-thickness ratio is,the more obvious the influence of mud is.The steel tube and concrete no longer meet the section assumption under the influence of the mud.The flexural capacity calculated by the unified theory agrees well with the test value,but with the increase of mud thickness,it gradually becomes larger than the test values,which leads to the reduction of the reserve for safety in design.The coefficient of the stiffness formula is about 0.1~0.4.