Title: Lateral Stiffness Characteristics of Reinforced Concrete Frame-Wall Structures
Author(s): A. E. Aktan, V. V. Bertero, and K. Sakino
Publication: Symposium Paper
Appears on pages(s): 231-262
Keywords: cracking (fracturing); deflection; earthquake resistant
structures; flexural strength; frames; framing systems; lateral
pressure; multistory buildings; reinforced concrete; shear
properties; shrinkage; stiffness; structural design; walls.
The lateral stiffness characteristics of medium-rise frame-wall systems were investigated at the serviceability limit state. Physical models of two exemplary structures, as well as individual wall elements, were tested. Experimentally measured displacements, local distortions, and internal force distributions were observed to differ by more than 100 percent from the analytically generated ones. The flexural, shear, and axial stiffnesses of individual wall elements were observed: (1) to be strongly influenced by intensity of axial force, (2) to approach nominal values based on gross-transformed section properties only at axial compression levels nearing the balanced value in the wall axial-flexural strength interaction relationship, (3) to decrease to less than 20 percent of the nominal stiffnesses at axial force levels approaching zero, and (4) to degrade significantly upon cracking at the serviceability limit state. Microcracking and very narrow cracking due to shrinkage induced by volumetric changes were identified as the main factors leading to reduced stiffnesses of walls upon first loading.