考虑粘结滑移的冻融损伤纤维梁柱模型研究

伸入梁柱节点以及柱与基础交界处纵向受力钢筋的粘结滑移效应会显著影响构件的侧向变形。为准确评估冻融损伤后钢筋混凝土(Reinforced Concrete, RC)柱的抗震性能，在考虑冻融损伤不均匀分布的纤维模型基础上，以锚固区的粘结滑移效应为研究对象，首先基于拉拔试验建立可考虑冻融损伤分布的粘结强度退化规律，进而根据简化粘结应力分布假设，通过建立控制方程进行理论推导得到冻融损伤粘结滑移计算方法，并与冻融钢筋混凝土拉拔试验数据进行了对比验证。进而基于有限元分析软件OpenSEES，将该文模型嵌套于零长度截面单元中，提出可综合考虑冻融不均匀损伤与粘结滑移效应的纤维梁柱模型，根据6榀冻融RC柱拟静力加载试验数据进行了验证，并与仅考虑冻融损伤的纤维模型进行了对比。结果表明:与纤维模型计算结果相比，采用该文模型计算所得滞回曲线与试验结果吻合更好，在承载力、极限位移和累积耗能等方面的计算误差较小，表明所建模型可更为准确地反映冻融损伤后RC柱的地震响应。

RESEARCH ON FREEZE-THAW DAMAGE MODEL OF FIBER BEAM-COLUMN CONSIDERING REINFORCEMENT SLIP EFFECT

The reinforcement slip in the beam-column joints or column footings can make a significant contribution to the total lateral displacement of reinforced concrete members. In order to accurately evaluate the seismic performance of reinforced concrete (RC) with freeze-thaw damage, the reinforcement slip effect is taken into consideration in this study based on the framework of the fiber model accounting for the uneven distribution of freeze-thaw damage. Firstly, the bond strength degradation model with the consideration of the distribution of freeze-thaw damage is built according to the bar pull-out test data. An analytical procedure is proposed for the prediction of reinforcement slip in the frozen-thawed anchorage area based on the assumption of simplified bond stress distribution along the bar and on the governing equations. The model is validated by comparing the data come from frozen-thawed bar pullout experiments. Then the proposed model is implemented to the zero-length section using the finite element software OpenSEES for formulating the modelling method for RC columns considering the uneven distribution of freeze-thaw damage and reinforcement slip effects. Pseudo-static test data from column specimens subjected to freeze-thaw cycles are used to validate the proposed column model and previous fiber model. The research results show that comparing with the fiber modelling results, the calculated hysteretic curves through using the proposed column model are closer to that of the test results, and that the strength errors, the ultimate displacement errors, and accumulated energy errors indicated that the proposed column model can accurately simulate the seismic response of RC column with freeze-thaw damage.