钢丝与混凝土粘结拔出行为的试验与模拟

该文首先建立了钢丝从混凝土基材中拔出的试验方法,并试验测定了不同锚固长度的钢丝拉拔行为,获得了拉拔荷载与拔出端位移之间的定量关系。在此基础上,建立了基于细观力学分析的钢丝拔出模型。通过模型计算,获得了钢丝与混凝土之间的界面粘结参数,并计算分析了锚固长度、倾斜角度等因素对钢丝拔出行为、最大承载力的影响。试验与模型计算结果表明,钢丝在混凝土中的拔出行为可分为脱粘和拔出两个阶段。在脱粘阶段,钢丝与混凝土之间的粘结强度可视为常数;在拔出阶段,钢丝与混凝土之间的粘结强度随拔出位移首先快速减小,之后减小速率逐渐降低,并趋于恒定值。对相同养护龄期,钢丝锚固长度越长,钢丝极限拔出荷载越大,同时与最大拔出力相对应的拔出位移也逐渐增大。钢丝埋置深度和角度相同时,养护龄期越长,钢丝抗拔能力增强。钢丝拔出方向与锚固方向不一致时,钢丝拔出荷载将增大,钢丝拔出方向与埋入方向夹角越大,抗拔极限承载力越大。模型与实验结果对比表明,所建模型及其所获得的粘结参数可良好地预测不同锚固长度的钢丝从混凝土中的拔出行为。

TEST AND SIMULATION ON PULL-OUT BEHAVIOR OF STEEL WIRE IN CONCRETE

A test method for steel wire pulling out from concrete is developed in this paper. The relationship of pull-out load and wire end slippage is obtained. Meanwhile, a micromechanical model of steel wire pull-out from concrete is developed. The interfacial bond parameters are obtained by model calculation. The impacts of embedment length and inclined angles of the steel wire on pull-out performance are analysed. The results show that the pull-out behaviour of steel wire from concrete can be divided into two stages, i.e., debonding stage and pull-out stage. In the debonding stage, the bonding stress between wire and concrete can be regarded as a constant. In the pull-out stage, the bonding strength between wire and concrete decreases rapidly first and then tends to a constant. For the same curing age, the pull-out peak load and corresponded wire end slippage increase with the embedment length. For the same embedment length pull-out peak load increases with curing age and inclined angles. Good agreement between test and model results is obtained and the pull-out model can be used to predict the pull-out behaviour of steel wire.