Modeling cyclic inelastic in-plane flexural behavior of concrete filled sandwich steel panel walls

Finite element analysis was first used to replicate the inelastic cyclic test response of previously tested concrete filled steel sandwich panel (CFSSP) walls, to determine the material and contact models best able to capture the wall's initial stiffness, the ultimate wall strength at each cycle, the web plate and HSS local buckling, and the pinching in the hysteresis loops. Results obtained show good agreement with all those aspects of response, while providing insights, guidance, and a validated model that will be of benefit in future studies of CFSSP-Walls. In a second part of this paper, the calibrated finite element model is used to provide insights and generate knowledge on some important aspects of wall behavior that is valuable for the design of CFSSP-Walls. Designers of CFSSP-Walls are typically provided little prescriptive guidance by design specifications and must instead rely, to a large extent, on findings from the recent research literature to ascertain that designs will perform as intended. For this new structural system, such insights into structural behavior are severely lacking. The findings here provide such insights on the distribution of wall-to-footing forces, shear force demands in critical tie bars, cumulative plastic strain value at failure due to low-cycle fatigue, the effect of hoop and shear stresses on uniaxial steel plate yielding, and the effect of interface friction on the force flow within boundary elements. These allow research to verify the adequacy of many of the assumptions used to determine the wall's plastic moment, which is typically considered to be the flexural strength of CFSSP-Walls.