带肋钢筋与Ⅱ型APC套筒约束灌浆料黏结性能试验研究

Experimental study on bonding properties between ribbed steel bars and grouting material constrained by TypeⅡ APC sleeve

关键词:  黏结滑移本构关系  约束灌浆料  锚固长度  套筒应变  拉拔试验

Key words:  bond-slip ontological relationship  constrained grout  anchorage length  sleeve strain  pull-out test

摘要:

为研究Ⅱ型APC套筒约束下带肋钢筋与灌浆料间的黏结滑移性能,本研究进行了23组共69个Ⅱ型APC套筒约束灌浆料钢筋拉拔试验。采用电液伺服万能试验机进行单向拉伸加载,利用应变片及位移计分别采集套筒应变和钢筋滑移值,研究了试件破坏形态、黏结强度影响因素、黏结滑移本构关系、套筒荷载应变曲线等。结果表明:套筒约束灌浆料试件的破坏形式包括钢筋（屈服前及屈服后）拔出破坏和钢筋拉断破坏两种；试件黏结强度随钢筋直径、锚固长度的增大而降低,随含钢率的增大而提升；钢筋与约束灌浆料间的黏结滑移分为滑移段、劈裂段、下降段、残余段4个阶段；对比不同材料锚固试件发现,灌浆料、套筒约束灌浆料、混凝土达到极限黏结强度时的滑移值依次降低,混凝土因骨料限制了裂缝发展,其滑移值最小。黏结滑移曲线的能量分析表明,试件延性较优,脆性系数随钢筋直径增大而降低、随锚固长度增大而提升。极限荷载时,套筒长边环向为拉应变,且随钢筋直径的增大而增大,短边环向绝大部分为压应变,套筒长边和短边纵向应变均为拉应变,且套筒长边纵向及环向应变均大于短边。基于ABAQUS平台构建了Ⅱ型APC套筒约束灌浆料有限元模型,其仿真结果与试验数据吻合较好。在计算屈服及拉断临界状态下钢筋临界锚固长度值时,套筒的存在可使其大大减小。

Abstract:

To study the bond-slip performance between ribbed steel bars and grout under Type II APC sleeve restraint, a total of 69 Type II APC sleeve-constrained grout reinforcement tensile tests in 23 groups were conducted in this study. An electro-hydraulic servo universal testing machine was used for unidirectional tensile loading. Strain gauges and displacement meters were used to collect data on the strain of the sleeve and the slip value of the reinforcing bar, respectively. The damage morphology of the specimens, factors affecting bond strength, bond-slip ontological relationship, and sleeve load-strain curve were studied. The results show that: The damage forms of the sleeve-constrained grout specimens include two types: the pull-out damage of steel bars (before and after yielding) and the pull-out damage of steel bars; The bond strength of the specimens decreases with the increase of the diameter of the steel bars and the anchorage length, and increases with the increase of the steel content rate; The bond slippage between the steel bars and the constrained grout is divided into four phases: slippage, cleavage, descending, and remnant;Comparison of anchorage specimens made of different materials reveals that when reaching the ultimate bond strength the slip values decrease in the order of unrestrained grout, sleeve-constrained grout, and concrete, and the slip value of concrete was the smallest due to the limitation of crack development by the aggregates. Energy analysis of the bond-slip curves shows that the ductility of the specimens is superior, and the coefficient of brittleness decreases with increasing reinforcement diameter and increases with increasing anchorage length. At the ultimate load, the annular direction of the long side of the sleeve is tensile strain, and it increases with the increase of the diameter of the reinforcement bar, the annular direction of the short side is mostly compressive strain, the longitudinal strain of the long side and short side of the sleeve is tensile strain, and the longitudinal and annular strain of the long side of the sleeve is larger than that of the short side. Based on the ABAQUS platform, a finite element model of type II APC sleeve-constrained grout was constructed, and the simulation results were in good agreement with the test data. When calculating the value of critical anchorage length of reinforcement in the critical state of yielding and pulling off, the existence of the sleeve significantly reduces this length.