The quantitative calculation and evaluation of seismic damage play a crucial role in ensuring structural safety, conducting performance-based structural analysis, and implementing seismic strengthening measures. However, there is limited research on the damage performance of blind-bolted T-stub steel connections used extensively in prefabricated buildings. In this study, the tensile sub model of a blind-bolted T-stub steel connection in a beam–column joint is investigated. The influence of the flange and web thickness of the T-stub connector, as well as the shear-loaded connecting bolts on the web of the T-stub, on the tensile performance of the sub model are considered. Four tensile destructive tests are conducted on a T-stub connector connected to a hollow section column using blind bolts. The experimental results, including failure modes, force–displacement curves, and strain development in the hollow section column and T-stub, are discussed and analyzed in this study. The test results reveal three main failure modes for this tensile substructure: the plastic deformation of the hollow section column, the bending fracture of the T-stub flange, and the fracture of the T-stub web bolt holes due to compression. Furthermore, a ductile damage finite element analysis method is employed to simulate the fracture damage process of the substructure, and the corresponding damage index is calculated using the typical Park–Ang damage model for evaluation, showing good agreement with the damage classification levels specified in FEMA.

Steel traditional Chinese buildings (STCBs) are constructed using modern materials, replicating the esthetics of ancient Chinese buildings, but their irregular joints differ significantly from those in conventional steel structures. To investigate the influence of beam section shape and axial compression ratio on the failure mode and shear resistance of all-welded irregular joints (WIJs) in STCBs, the size proportion relationships in the traditional Chinese modular construction system for such joints in existing practical projects are analyzed. Four exterior joint specimens were designed and fabricated for pseudo-static loading tests. The failure mode, hysteresis curve, and skeleton curve of the specimens were obtained. The test results indicate that the failure mode of the specimens involves shear deformation in the lower core area, with final failure due to crack formation in the weld at the junction between the column wall and the beam flange. As the axial compression ratio increases, the bearing capacity of the joint decreases. Based on the test results, the numerical model was established by using finite element software Abaqus2016, and parameter analysis was performed by varying the axial compression ratio of the column. After analyzing the force transfer mechanism of the core area in the WIJs of STCBs, a simplified calculation formula for the shear bearing capacity of the core area was derived based on the proportional relationship outlined in the construction manual from the Song Dynasty. The calculated results show good agreement with the experimental results, providing a basis for the structural design of WIJs in STCBs.

In this paper, the quasi-static reciprocating loading test was carried out for the T-stub steel middle column joints with blind-bolt connections. As the thickness of the T-stub steel increased, the damage failure modes were different. The load–displacement curve, cumulative energy dissipation, equivalent viscous damping coefficient, damage index and other characteristics of the joints were analysed. When T-stub steel was used as a connector, its thickness affected the damage development mode. As the thickness of T-stub steel increased, the bearing capacity and plastic displacement were improved, the energy dissipation capacity was significantly increased, and the rotational stiffness retention ability of the joint was improved, but the damage index value was not significantly increased. Finally, the damage index and the rotational stiffness degradation coefficient under each loading level were numerically fitted, and the polynomial and exponential rotational stiffness models were established, taking into account the damage index. These two models took into account the reduction in rotational stiffness caused by damage under each level of load, and the rotational stiffness under each loading level could be obtained from the damage index and the initial rotational stiffness.

To improve the seismic performance of semi-rigid steel frame beam–column joints connected by T-stubs, reinforced T-stubs formed via wedge-shaped and thickening modifications are proposed. Taking the middle column joints in steel frames as the research objects, three types of beam–column joints are designed by adopting ordinary, wedge-shaped, and thickened wedge-shaped T-stubs. To conduct a comparative analysis of the seismic performance of the test specimens, this study imposes low-cycle cyclic loads on the column ends of each specimen along their major-axis and minor-axis in-planes. This loading protocol is adopted to simulate the dynamic responses of the specimens under bidirectional seismic action. Comparing the macroscopic failure phenomena of the specimens, the influence of reinforced T-stubs on the plastic development mode of the joints is analyzed. Based on seismic indicators such as hysteresis characteristics, skeleton curves, stiffness degradation, and energy dissipation capacity, the energy dissipation capacity of the specimens along the major-axis is greater than that along the minor-axis, but their deformation capacity is slightly reduced. The bearing capacity, energy dissipation, and rotational stiffness could be improved by reinforced T-stubs, but the deformation capacity is reduced to varying degrees. The stiffness degradation rate of the specimen adopting wedge-shaped T-stubs shows a more obvious accelerating trend. Through the comparative analysis of the three specimens based on the energy damage index, the results indicate that wedge-shaped T-stubs significantly increase the damage degree of the specimens, but thickened wedge-shaped T-stubs have a relatively small impact on the evolution of joint damage.

Four full-scale exterior beam-to-column connections comprising H-section beams and square hollow-section (SHS) columns were tested under low-cycle reversed loading to investigate two engineering-oriented T-stub section configurations and the effects of the presence or absence of triangular stiffeners. Failure modes, moment–rotation response, stiffness degradation, energy dissipation, and cumulative damage were evaluated, together with nonlinear finite element simulations and a modified Park–Ang damage assessment. All specimens progressed from bolt-hole slip through plastic deformation to localized fracture. In the unstiffened connections, damage concentrated near the T-stub flange-to-web junction; stiffeners redistributed critical demand toward the stiffener welds, adjacent T-stub webs, and SHS column walls. The maximum differences in initial rotational stiffness relative to J1A were 15.69% and 15.07% in the positive and negative loading directions, indicating that the elastic-stage response reflected the combined deformability of the T-stub, blind-bolt assembly, and column wall. The maximum increases in yield moment, peak-resistance moment, and ductility coefficient were 20.59%, 43.71%, and 45.91%, respectively. Complete-history energy dissipation varied non-monotonically across the tested configurations. The finite element model reproduced the global and local responses, while the damage-index results showed overall correspondence with the observed failure progression. The findings emphasize stiffness compatibility and rational distribution of plastic demand rather than maximum local stiffness.

To investigate the feasibility and effectiveness of seismic repair for prefabricated single-beam column joints in modern Chinese traditional-style buildings (MCTBs), low-cycle reversed loading tests were conducted on two original joints with different T-stub web thicknesses and one repaired joint. A repair strategy was proposed in which damaged T-stub connectors were removed and replaced with welded end-plate connections. The seismic behavior of the joints, including failure mode, hysteretic response, skeleton curve, stiffness degradation, ductility, energy dissipation capacity, and seismic performance comparison between the original and repaired joints, was systematically evaluated. In addition, a refined finite element model was established using ABAQUS and validated against the experimental results to investigate the stress distribution, deformation characteristics, and load-transfer mechanism of the joints. The results indicate that damage in the original joints was mainly concentrated in the T-stub connection region, while the beam and column members remained essentially intact, demonstrating an effective damage-control mechanism. Increasing the T-stub web thickness improved the load-carrying capacity, stiffness, and ductility of the joints. After repair, the load-transfer mechanism changed from a blind-bolted T-stub connection to a welded end-plate connection, resulting in a different damage evolution pattern and failure mode. Nevertheless, the repaired joint exhibited stable hysteretic behavior, satisfactory deformation capacity, and favorable energy dissipation performance. Compared with the original joint, the repaired specimen achieved a moment capacity comparison ratio of approximately 116%, stiffness comparison ratios exceeding 120%, and an energy dissipation comparison ratio of approximately 148%. The finite element results agreed well with the experimental observations and further revealed the evolution of stress concentration regions and load-transfer paths before and after repair. The present experimental results demonstrate the feasibility of the proposed repair method for rehabilitating damaged joints while maintaining satisfactory seismic performance without replacing the primary beam and column members. The proposed repair strategy therefore provides a practical and efficient solution for the post-earthquake rehabilitation of prefabricated joints in MCTBs.