Restoring force model for earthquake-damaged RC columns strengthened with textile reinforced concrete (TRC) jackets

The restoring force model of reinforced concrete (RC) structures is proficient in delineating instantaneous variation laws, such as the degradation of strength and stiffness, and the pinch effect. It forms the quintessential basis for the execution of structural elastoplastic analysis and stands as an integral component within the scholarly exploration of the seismic performance of structures. This paper concentrates on textile reinforced concrete (TRC) strengthened earthquake-damaged RC columns that are primarily subjected to bending failure. In order to evaluate the dynamic characteristics of TRC-strengthened damaged columns under cyclic loading and forecast their hysteretic performance, a restoring force model for earthquake-damaged RC columns strengthened with TRC has been developed. Firstly, based on the experimental results of TRC-strengthened RC columns, it has been ascertained that their backbone curve exhibited a tri-linear characteristic. And characteristic points of the backbone curve, i.e., yield point, peak point, and ultimate point were determined through section performance analysis calculations rooted in the material constitutive relationship. Furthermore, simplified hysteresis rules were proposed by modifying the Clough hysteresis rules, with explicit definitions of loading/unloading stiffness calculation methods for strengthened RC columns. Consequently, a bending restoring force model for damaged RC columns strengthened with TRC was proposed. The predicted results agree well with existing experimental results, verifying that the restoring force model proposed in this paper could effectively and relatively accurately descripted the hysteretic characteristic of damaged RC columns strengthened with TRC under low-cycle loading. The developed model would provide a theoretical basis and reference for seismic strengthening design and engineering applications of TRC technology.