长期轴压下有初应力的CFRP约束混凝土柱应力-应变关系分析

为了研究有初应力的CFRP约束混凝土柱在长期荷载作用下的应力-应变关系，对有不同初应力的12个CFRP约束混凝土柱进行了三种模式的长期荷载试验，观测了初应力和长期荷载对CFRP约束柱的长期变形、峰值点应力、应变及应力-应变曲线特征的影响。试验结果表明，在长期荷载作用下，包裹CFRP后的构件比未包裹的长期变形小，并随初应力水平的提高，构件的长期变形增大；长期荷载对峰值点应力、应变的影响随初应力水平的提高而增大，在初应力水平较高时有减小的趋势；与短期荷载相比，长期荷载作用后的应力-应变曲线特征没有发生明显变化。在此基础上，选取ACI 209-92模型和Findley模型分别作为混凝土和CFRP的徐变模型，提出了CFRP约束混凝土柱长期变形的计算方法，并针对三种加载模式，分别建立了长期荷载下CFRP约束混凝土柱的应力-应变关系计算模型，结果表明模型的计算曲线与试验曲线吻合较好。

Analysis on the stress-strain relationship of CFRP confined concrete with initial stress under long-term sustained load

To study the stress-strain relationship of CFRP confined concrete with initial stressunder the sustained load, a total of twelve columns with different initial stress level weretested under three types of the sustained load modes. The influence of initial stress andsustained load on the long-term deformation, the peaks of the strain and the stress of concrete,and the stress-strain relationship of CFPP confined concrete columns were observed. Theexperimental results show that the axial strain of CFRP confined concrete is smaller than that ofunconfined ones, and the axial strain rises with the increase of initial stress level. The peaksof stress and strain of concrete are affected by the sustained load and the initial stress.Meanwhile, the peaks of the stress and strain of concrete decrease with the initial stress level.The characteristic of stress-strain curve under the long-term loading is similar with that undershort-term loading. A method to calculate the long-term deformation of the CFPR confined concretecolumn is proposed. In this method, ACI 209-92 model and Findley model are adopted to simulate thecreep of concrete and CFRP, respectively. Moreover, a model for stress-strain curve of CFRPconfined concrete column is presented, considering initial stress level and long-term sustainedload mode. The results show that the numerical curve agrees well with the experimental curve.