Cyclic Behavior and Design of an Innovative Composite Coupling Beam Using Stainless Steel Tube and Rib Plates

Abstract

Concrete-filled composite coupling beams provide an efficient alternative to RC beams for connecting shear walls, due to their enhanced structural performance and accelerated construction schedule. However, their rotation capacity is limited by strain concentration at the beam-to-wall connection and the relatively low fracture strain of conventional carbon steel. To address these issues, this study introduces an innovative composite coupling beam that incorporates rib plates at the connection and uses stainless steel tubes. Nine cyclic tests were conducted. The results showed that the use of rib plates enhanced both strength and rotation capacity by shifting the fracture location away from the connection, and the stainless steel further improved the rotation capacity by delaying the fracture initiation. Finite-element (FE) models then were developed and benchmarked to conduct additional parametric analyses. The analysis results showed that the thickness and grade of the stainless steel plate influenced both the strength and ductility, whereas the compressive strength of concrete had a minor effect. Finally, the applicability of AISC 360-22 for estimating flexural strength was evaluated and modifications are proposed.