A simplified method is presented for the analysis of laterally loaded wide-flanged shear wall structures with rigid or flexible joints between web and flange. The flange and web elements may be either of solid or framed construction, the latter being included by replacing the frame panel by an equivalent orthotropic plate in which the shear modulus is chosen to model the racking behaviour of the rigidly-jointed frame. The results obtained are compared both with theoretical values obtained by the finite element and frame methods, and with the results from a series of tests on small-scale plexiglass models. The method gives results which are sufficiently accurate for practical purposes, and enable the degree of shear lag in the flange, the effective width, and the lateral deflection to be estimated rapidly.

The results of an experimental investigation to determine strength of rectangular low-rise structural walls for buildings are presented in this report. Seven large specimens with "height-to-hori-zontal- length" ratios of 1.0 were subjected to static in-plane horizontal loads. One of the specimens was subjected to ten cycles of load reversals. Variables in the test program were amount and distribution ofvertical and horizontal reinforcement. The walls did not have any boundary elements or special hoop reinforcement. No vertical load was applied. Results indicate that low-rise rectangular walls can develop shear stresses on the order of 10 f'c psi (0.83 f'c MPa). Also, results indicate that shear strengths implied by Section 11.10, Special Provisions for Walls, of the 1977 ACI Building Code provide a reasonable lower bound capacity, even when load reversals are applied.

Two three-story, two-bay l/10 scale reinforced concrete model frame structures were subjected to combined gravity and lateral loads. One frame was subjected to unidirectional lateral loading, and the second was loaded with gradually increasing reversing lateral loads; loads were increased to failure in both cases. Distribution of lateral loads was in accordance with the SEAOC requirements for seismic design; steel reinforcement was also designed to conform to these requirements. A nonlinear, incremental stiffness analysis approach was developed for uni-directional loading and was applied to the experimental frame and to a single bay portal frame reported in the literature. Stiffness reduction of the frame subjected to reversing lateral loads was not more severe than that for the unidirectionally loaded frame at loads less than about 80% of the ultimate lateral load capacity of the frame. There was minor reduction in strength and stiffness caused by cycling at higher load levels. Ductility requirements were met by the frames, and no adverse shear-induced effects were observed in the joint regions of the frames. The analytical method gave excellent predictions of frame deformations.

Two approaches are discussed for mathematical modeling of the elastic and inelastic response of infilled frames. The first approach is based on idealizations of local behavior, while the second is based on observations of overall behavior. Both approaches are found to give good representations of nonlinear response. The second approach, based on the equivalent strut concept, is believed to be efficient for use in analyzing the response of complex, infilled frame structures.

Numerous computer analysis techniques for use in the seismic design of reinforced concrete structures are available to the design engineer and are finding general use. Unfortunately, these techniques are not "exact". Rather, they are forced to make a large number of questionable assumptions about earthquake characteristics and building behavior. To the practicing engineer, whose complex structures and structural elements defy symmetry, regularity and simplicity, the valid use of such technique depends on a complete understanding of the analysis limitations and inaccuracies and requires constant review of the results for analysis generated errors. This paper, while presenting a practical analysis application, addresses the serious difficulties and the inherent inaccuracies encountered in applying the most commonly used computer analysis techniques to concrete shear wall buildings. It is based on the actual computer analyses of a variety of middle-rise concrete shear wall buildings performed over the past few years at H. J. Degenkolb & Associates. This paper, while it addresses and identifies the invalid results that can be easily produced, believed and designed for, in concrete shear wall building analysis, also provides usable techniques for identifying, adjusting and correcting the problems that are encountered. As such, it provides the practicing engineer with additional insight and understanding of his computer analysis techniques.