Comparative Performance Assessment of RCS Connections Across Different Generations of ASCE Guidelines

The hybrid moment-resisting frames, comprising Reinforced Concrete columns and Steel beams (RCS), have attracted attention due to potential cost savings and enhanced structural characteristics. The ASCE Task Committee on Design Criteria for Composite Structures issued early guidelines for RCS joint design, primarily applicable to low seismicity regions. Subsequent research has demonstrated the reliable ductile performance of Composite RCS systems, making them attractive for high seismic areas. Following this, an updated Pre-Standard for the Design of RCS connections was introduced, serving as the latest ASCE guideline for designing RCS joints. This paper investigates the cyclic performance of different RCS joint details, focusing on the influence of design requirements on connection behavior. Four specimens are selected for investigation, with two conforming to the early ASCE guideline and two to the updated ASCE guideline. The early ASCE guideline-conforming specimens closely resemble the updated ones, with the distinction that a doubler plate is attached to their beam web. A detailed finite element model, validated against experimental data, is employed to analyze the specimens. The results indicate better connection performance when adhering to the early ASCE guideline requirements compared to the updated ASCE guideline. The incorporation of a 6 mm thick doubler plate, along with four triangular stiffeners, significantly enhances connection performance, including increased initial strength, reduced strength degradation, and improved energy dissipation capacity. These modifications contribute minimally to the overall building cost while yielding a substantial 25.5% increase in connection energy dissipation capacity and a 40% reduction in strength deterioration during cyclic loading.