## 2 Beam-Column Joints of Composite Frames Under Seismic Loads  
### Beam-Column Joints of Composite Frames Under Seismic Loads: State-of-the-Art  
Beam-column joints play a crucial role in steel-concrete composite structures, particularly during seismic events, as they transfer forces between beams and columns and affect the structure's earthquake resistance. Composite structures have gained popularity due to their combined strength, stiffness, and ductility. This scholarly paper provides a comprehensive review of the seismic analysis and design of beam-column joints in these structures. It covers recent advancements in experimental studies, analytical methods, and design approaches, focusing on failure modes, influential parameters, experimental investigations, modeling techniques, existing guidelines and limitations, and emerging joint configurations. By consolidating recent research and identifying gaps, this review aims to offer valuable insights to earthquake engineering and structural design professionals. Thus, [PERSON] et al. (2017) [1] examined a detailed finite element (FE) model for studying the performance of deconstructable beam-to-column composite joints. Their model was validated through experiments, and a parametric study was conducted to analyze various parameters. Design models were proposed to predict performance parameters. Key findings included the impact of shear connection ratio, reinforcement ratio, bolt size, slab thickness, column flange thickness, and steel grade on joint behavior. It was found that the design models could accurately predict performance parameters, even for joints with high-strength steel components. Furthermore, [PERSON] et al. (2015) [2] presented a solution for connecting I-shaped beams to concrete-filled RHS columns using long bolts. The joint configuration improved rigidity and resistance, making it suitable for seismic-resistant moment frames, while experimental tests and analytical models were used to validate the joint design. Moreover, the dynamic response and failure mechanism of a new assembly of blind-bolted CFST composite structures under simulated seismic loading were studied by [PERSON] et al. (2017) [3]. The tests showed excellent seismic performance, including good ductility, energy dissipation capacity, and damage control, while analytical modeling using OpenSees software 3.7.1 ([[https://opensees.berkeley.edu/](https://opensees.berkeley.edu/)]([https://opensees.berkeley.edu/](https://opensees.berkeley.edu/)) accessed on 10 September 2024) validated the results. [PERSON] et al. (2018) [4] presented a study on the seismic performance of an innovative end-plate connection between T-shaped CFT columns and reinforced concrete beams. Seven specimens were tested, one under monotonic loading and six under cyclic loading. The proposed end-plate connections exhibited good seismic performance, achieving the desired \"strong column and weak beam\" and \"strong connection\" objectives in seismic design. [PERSON] et al. (2018) [5] found that the diameter of the bolts and the length of the (H-shaped) steel corbel influenced the yield strength, ultimate strength, and initial stiffness. A FEM model was also constructed and subsequently verified, and parametric studies revealed the impact of beam reinforcement ratio and concrete strength on seismic performance. Moreover, [PERSON] et al. (2021) [6] examined the shear strength and seismic damage performance of H-section beams with unequal-depth CFT column composite joints. Four specimens with varying height ratios of the beams were subjected to lateral cyclic loading. The findings indicated that shear failure occurred primarily in the joint core area, with the joint core area reaching yield strain earlier as the beam height ratio increased. A mathematical formula was developed to calculate the shear strength of the CFT columns with a H-shaped beam joint. This equation takes into account the combined effects of the restrained compression struts in the joint central region, concrete compression struts, and steel tube web.