Feasibility of 2-D analyses in determining the design member forces in asymmetric 3-D RC frame structures

On the basis of an examination of the general characteristics in the structural behavior of 3-D RC frame structures, this paper introduces the possibility of adopting a 2-D frame structural analysis in the preliminary design stage at which the initial design sections are determined, even in the case of asymmetric 3-D RC frame structures. Upon consideration of the creep deformation of concrete and the construction sequence, which dominantly affect the structural responses of concrete structures, material nonlinear analyses of RC frame structures are performed with the use of a numerical approach based on the moment-curvature relation of an RC section, because it can deliver computational efficiency in 3-D RC frame structures composed of many beams and columns. Furthermore, a simplified numerical solution procedure that can reflect the change in the moment-curvature relations with the magnitude of the axial force and the biaxial bending moments is introduced and its exactness is verified through correlation studies between experimental data and numerical results. Typical asymmetric 3-D RC frame structures are considered with variation in the arrangement of asymmetric upper floors, and the structural responses are analyzed from the perspective of member forces to examine whether the member forces determined through a 2-D analysis can be used in the preliminary design of asymmetric 3-D RC frame structures. Finally, through a comparison of member forces in RC frame structures, it can be concluded that 2-D RC frame analyses only considering the construction sequence can be utilized in the preliminary design of 3-D RC frame structures with or without symmetry.