A unified section-based restoring force model for reinforced concrete coupling beams based on the XGBoost model: Establishment, validation and application

Abstract

To enhance the seismic performance of reinforced concrete (RC) coupling beams, improved reinforcement details such as diagonal layout and high-performance concrete including fiber reinforced concrete (FRC) as well as engineered cementitious composites (ECC) are widely investigated and applied. Despite the numerous experimental studies on various reinforced concrete coupling beams, there is still a lack of unified, efficient and accurate numerical model applicable to all kinds of concrete and reinforcement layouts, leading to difficulty in numerical study and proper design of coupling beams and coupled shear walls. In this study, a database containing 180 reinforced concrete coupling beam specimens is first set up. Then the key mechanical indexes of test curves including the peak load, peak beam rotation, yielding beam rotation and softening beam rotation are predicted using the trained XGBoost models. The feature importance and partial dependence of different independent variables are analyzed. Based on the predicted results, the skeleton curves of the section-based restoring force model can be obtained. Besides, a new hysteretic rule for the restoring force model which can account for the pinching effect, strength and stiffness degradation is proposed. The proposed model is then implemented in ABAQUS 2017 software, of which the accuracy and applicability are validated by twelve coupling beam specimens with different concrete materials and reinforcement layouts. Finally, a coupled shear wall specimen is simulated to quantitatively and thoroughly evaluate the effects of key indexes of the coupling beams on the seismic performance of the coupled shear wall structures.