Dan Liang

To reduce the modeling effort and computational cost of assembled composite shear walls with C-shaped steel frames in global structural analysis, this study proposes an engineering-oriented simplified mechanical analysis method. Three representative specimens—a C-shaped steel-frame composite shear wall (CSCSW), a rectangular steel-frame composite shear wall (RSCSW), and a T-shaped, C-shaped steel-frame composite shear wall with a vertical connection (VTCSWC)—are decomposed into functional modules according to their load-transfer mechanisms. Simplified models comprising axial springs, diagonal braces, and a modified three-vertical-line-element model are established. Degrading bilinear Clough and trilinear Takeda models are adopted as the restoring-force relationships, and the governing parameters are determined through mechanical equilibrium analyses. The three simplified wall models are implemented in OpenSees to obtain hysteresis curves, skeleton curves, and stiffness-degradation responses. Comparisons with quasi-static test results show that the errors in peak load and secant stiffness are both within 10%, while the models reproduce the stiffness degradation and pinching characteristics of the specimens. Relative to refined three-dimensional solid finite element models, the proposed approach substantially reduces computational cost without compromising engineering accuracy, providing an efficient tool for structural design and seismic performance assessment of assembled C-shaped steel-framed composite shear-wall systems.

To systematically investigate the effects of C-shaped and rectangular steel frames on the seismic performance of assembled composite shear walls, this paper, based on the validation of existing pseudo-static test results, employs ABAQUS software to establish refined finite element models, and carries out parametric analyses on C-shaped steel-frame composite shear walls (CSCSWs) and rectangular steel-frame composite shear walls (RSCSWs). With shear-span ratio, axial-load ratio, boundary frame steel plate thickness, and concrete strength grade as variables, a total of 28 numerical models are designed to systematically examine the influence laws of each parameter on bearing capacity, ductility, energy dissipation capacity, and failure modes, and to reveal the performance differences in the confinement mechanisms of the two cross-sectional types. The results indicate that: as the shear-span ratio decreases from 3.0 to 1.0, the bearing capacity increases by up to 171%, but the ductility drops by up to 43%, and the failure mode shifts from flexure-dominated to shear-dominated; increasing the steel plate thickness can simultaneously enhance bearing capacity and ductility, with the peak load increasing by up to 52% and cumulative energy dissipation by over 110%, the mechanism being the synergistic enhancement of the flexural contribution of the boundary frame and the passive confinement effect on the core concrete; increasing the axial-load ratio can improve bearing capacity by about 24%, but significantly impairs ductility and energy dissipation capacity, and it is recommended that the design axial-load ratio be controlled between 0.26 and 0.43; the concrete strength grade has a limited effect on bearing capacity, and as the strength increases, brittle characteristics emerge, leading to a ductility decrease of about 12%; therefore, provided that the strength requirements are met, enhancing the concrete strength grade should not be taken as the primary technical approach for improving the seismic performance of such structures. Comparing the two cross-sectional types, the rectangular cross-section, by providing more uniform and effective lateral confinement, exhibits superior bearing capacity, ductility, and energy dissipation to the C-shaped cross-section across the entire parameter domain, and its performance advantages are more pronounced under conditions of high axial-load ratio and large shear-span ratio.

Axial compression tests were conducted on four groups of C-shaped steel tube-confined concrete specimens. The results demonstrate that the C-shaped steel tube effectively confines the core concrete, significantly enhancing the peak compressive stress by 14.1% to 22.1% compared to unconfined concrete, resulting in a more gradual descending branch of the stress–strain curve, and effectively improving the ultimate deformation capacity of the concrete with peak strain increasing by a factor of 1.45 to 1.68. The influences of steel plate thickness and reinforcement on the compressive stress–strain curve of the confined concrete were systematically analyzed. Based on the analysis of the strain in the steel tube and the stress state of the confined concrete during testing, a method for calculating the effective confining stress on the core concrete is proposed. A uniaxial compressive stress–strain model for C-shaped steel tube-confined concrete is developed based on the Mander model. Comparisons show that the proposed model agrees well with the experimental stress–strain curves, with predicted peak stresses within 5% of experimental values and predicted peak strains within 7% deviation.