基于粘结-滑移的FRP筋钢纤维轻骨料混凝土梁裂缝宽度计算方法

CALCULATION METHOD FOR CRACK WIDTH OF STEEL FIBERREINFORCED LIGHTWEIGHT AGGREGATE CONCRETE BEAMS REINFORCED WITH FRP BARS CONSIDERING BOND-SLIP BEHAVIOR

将纤维增强筋(FRP筋)混凝土梁裂缝的开展过程视作FRP筋由两侧混凝土中拔出的过程,建立了基于粘结-滑移的FRP筋轻骨料混凝土梁裂缝宽度微分方程。根据规范给出的裂缝宽度限值,合理确定滑移量上限,提出并引入了适用于梁正常使用阶段的FRP筋钢纤维轻骨料混凝土“低滑移”阶段粘结-滑移本构模型。进而,在明确最大裂缝间距l_(max)、裂缝宽度放大系数h_(2)/h_(1)与裂缝截面纤维混凝土残余应力σ_(fib)等特征参数的基础上,利用迭代算法建立了FRP筋钢纤维轻骨料混凝土梁最大裂缝宽度计算模型。基于正常使用阶段裂缝宽度实测数据对建议模型的适用性进行评估,结果表明:裂缝宽度限值0.5 mm内,建议模型能够准确预测FRP筋钢纤维轻骨料混凝土梁的最大裂缝宽度。

Regarding the crack development of concrete beams reinforced with fiber-reinforced polymer(FRP)bars as a process wherein the FRP bars are pulled out from concrete on both sides,a differential equation of crack width of lightweight aggregate concrete beams reinforced with FRP bars considering bond-slip behavior was established.According to the crack width limits provided by the design codes,the upper limit of slip was reasonably determined and constitutive models for bond-slip relationship between FRP bars and steel fiber reinforced-lightweight aggregate concrete in‘low slip’stage which were suitable to the service stage of the beams were proposed and introduced.The maximum crack spacing,l_(max),amplification factor of crack width,h_(2)/h_(1),and residual stress of fiber reinforced-concrete in cracked sections,σ_(fib),were specified.On this basis,a crack width model of steel fiber reinforced-lightweight aggregate concrete beams reinforced with FRP bars was proposed using iterative algorithm and its accuracy was evaluated based on measured data of maximum crack width in service stage.It is shown that within crack width limit of 0.5 mm,the proposed model generates accurate maximum crack width predictions for steel fiber-reinforced lightweight aggregate concrete beams reinforced with FRP bars.