Axial force-biaxial moment-vector shear (P-M-V) interaction for steel-plate composite (SC) wall piers

Abstract

Structural walls in industrial construction may be subjected to a combination of axial, in-plane, and out-of-plane force and moment demands. Experimental studies conducted on SC wall piers (i.e., walls without any boundary elements) subjected to combined in-plane and out-of-plane forces and moments indicate that wall piers with aspect (wall height-to-length) ratios greater than or equal to 0.6 have flexure dominated response. Experimental results indicate that wall piers subjected to out-of-plane shear force equal to their nominal shear strength (per US codes) develop flexural yielding and failure due to biaxial moments, i.e., interaction between the in-plane moment and out-of-plane moment. Shear failure (in-plane or out-of-plane) does not occur in these walls. The wall pier specimen subjected to out-of-plane shear force that was 250% of the nominal shear strength (calculated using US codes) was forced into a shear failure mode by the vector shear corresponding to the vector sum of in-plane shear and out-of-plane shear. This paper presents the development of a numerical model to consider the complex interaction of axial, in-plane, and out-of-plane forces and moments. For walls having flexure dominated response, a trilinear interaction surface is recommended for biaxial (in-plane and out-of-plane) moments. This interaction surface is a function of the applied axial compression force. For SC wall piers with aspect ratios lower than 0.6, or those subjected to out-of-plane shear forces larger than the calculated nominal strength, the behavior will not be flexure dominated, and the effects of vector shear force on the biaxial moment interaction also need to be considered. For such cases, an axial force-biaxial moment interaction surface that can account for vector shear failure (P-M-V) is recommended. The numerical models and accompanying interaction surfaces presented in this paper enable the consideration of simultaneous axial, in-plane, and out-of-plane forces and moments in the design of structural wall piers (without boundary elements).