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.