高温作用下锈蚀钢筋与混凝土黏结性能研究

Study on bond behavior between corroded reinforcement and concrete at elevated temperature

为研究高温下与高温后锈蚀钢筋与混凝土黏结性能退化规律,制作84个混凝土立方体试块及110个偏心拉拔试件,对立方体试块进行高温下及高温后抗压试验,对偏心拉拔试件进行高温下及高温后拉拔试验,分析温度状态(高温下和高温后)、锈蚀率(2%、5%和10%)、试件尺寸(立方体、棱柱体)及箍筋数量(单肢箍和双肢箍)对黏结性能的影响,依据高温对材料性能的折减规律,得出高温下锈蚀钢筋混凝土黏结强度计算方法,提出分段式及连续型黏结滑移本构模型。研究表明:锈蚀时间为59 d且历经400℃的混凝土抗压强度降低了27.6%,温度100℃时锈蚀率为4.6%的钢筋混凝土黏结强度较常温的增大8%,温度200~400℃时黏结强度降低约9%,800℃时黏结强度损失85%;温度低于400℃时,高温下钢筋混凝土黏结强度小于高温后的,温度高于400℃时,不同温度状态下黏结强度值相近;单肢箍筋试件黏结强度较双肢箍筋试件黏结强度下降了10%,立方体(150 mm×150 mm×150 mm)试件黏结耗能是棱柱体(150 mm×150 mm×300 mm)试件黏结耗能的54%。通过比较积分绝对误差验证了模型精度,计算误差小于10%,可用于锈蚀结构火灾下的数值计算。

To investigate the degradation regular of bond behavior between corroded rebar and concrete at and after elevated temperature,84 cube specimens and 110 eccentric pull-out specimens were made.The cube specimens were subjected to compressive strength test,and the eccentric specimens were subjected to pull-out test respectively.The influence of temperature condition(at and after high-temperature),corrosion levels(2%,5%,and 10%),specimen size(cubic and prism specimen),and stirrup number(single and double stirrup)on the bond behavior were analyzed.The bond strength calculated method of corroded structures at high temperature is obtained,and the segmental and continuous bond slip constitutive models are proposed.Research indicates that the concrete compressive strength immersed for 56 d at 400℃is reduced by 27.6%,and the the bond strength of corroded specimen at 100℃is 8%higher than that at 20℃,the bond strength decreases by 9%from 200℃to 400℃,and the bond strength loss is 85%at 800℃.When the temperature is below 400℃,the bond strength at elevated temperature is less than that after fire.When the temperature is higher than 400℃,the bond strengths under two temperature states are similar.The bond strength of a single stirrup specimen is 10%lower than that of a double stirrup specimen,and the energy consumption of little specimen is 54%of that of larger specimen.The accuracy of the model is verified by integral absolute error,the calculation error is less than 10%,and the calculated formula can provide a basis for the numerical calculation of corroded structures under fire.