Coupling Coefficient-Based Damage Evaluation Method of Precast Unbonded Post-Tensioned (UPT) Shear Wall Structures

Abstract

This research presents a damage evaluation method proposed for structures with precast unbonded post-tensioned (UPT) shear walls using the concept of coupling coefficient. The proposed method considers the damage mechanism of the entire structure with damaged UPT shear walls, including the detachment of wall bases, yielding of dampers and UPT bars, yielding of beams or columns, concrete crushing, and so on. The contributions of frames and walls to structural seismic performance can be estimated separately by introducing wall and structure damage parameters. An accidental torsion parameter was proposed to reflect out-of-plane structural rotation. A two-story, low-damage concrete shear wall building designed for large-scale shaking-table testing is adopted as a benchmark structure to verify the proposed method. First, a three-dimensional finite element model of the benchmark structure was constructed, and the damage and accidental torsion parameter curves were derived using static analysis. Limit values of the damage parameters for the design and collapse limit states are obtained from the parameter curves calculated by simulation and the proposed equations, respectively. Then, incremental dynamic analysis with bidirectional ground motion inputs was conducted to check the damage evaluation performance at various damage levels and compare with conventional evaluation method based on the inter-story drift. The proposed method is validated to be systematic, detailed, and sensitive to damage.