Lateral load-displacement response of flexure-dominant concrete-encased steel columns based on ASCE/SEI 41

Concrete-encased steel (CES) column, in which structural steel is encased in an RC section, is widely used in high-rise or heavily-loaded structures due to its great load-carrying capacity, rigidity, and durability. Nevertheless, the development of performance-based seismic design is still insufficient for CES structures, especially for evaluating the lateral load-displacement relationship. As a commonly-used performance-based seismic design (PBSD) guidance, current ASCE/SEI 41 guides global engineers to conduct the seismic evaluation of RC, steel, masonry, and timber structures. Nevertheless, ASCE/SEI 41 fails to give the modeling parameters for CES members owing to insufficient research concerning the steel-concrete interaction. In this paper, a lateral load-displacement curve for flexure-dominant CES columns under a nonlinear static procedure is proposed based on the provisions of RC members in the current ASCE/SEI 41. In the proposed curve, different constitutive laws are applied to consider different confinement of concrete; the slip between the structural steel and surrounding concrete is considered by reduced lateral stiffness; meanwhile, the end rotation caused by the bar-slip in RC is also taken into account to simulate the lateral behavior better. With a detailed calculation procedure, a comparison with experimental results of 42 CES columns in different references is reported to verify the applicability of the proposed curve. It can be concluded that the proposed curve can produce reasonable predictions of cracking load, cracking displacement, yield load, yield displacement, peak displacement, and strength degradation of flexure-dominant CES columns, leading to a feasible way to evaluate the lateral response of CES columns in practical design. •A lateral load-displacement curve of CES columns that fail in flexure is proposed under the framework of ASCE/SEI 41.•The proposed curve considers the effects of bond-slip, confinement ratio, and reinforcement detailing on the curve configuration.•Based on the proposed curve, ASCE/SEI 41 can reasonably model the lateral behavior of CES columns.