International Concrete Abstracts Portal

A total of 21 technical papers comprise this Special Publication which covers recent developments in lateral force transfer in buildings. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP157

The difficulties in assessing the probable deformation and force states of structural wall buildings under lateral earthquake forces were evaluated by means of laboratory test results from a five-story full-scale reinforced masonry structural wall research building tested to failure at the University of California, San Diego, under simulated seismic loads. The individual structural components and actions which contribute predominantly to the seismic response characteristics of a structural wall building, such as axial loads on walls, coupling between structural walls, lintel beam force, and deformation capacities, as well as floor and wall-flange participation were evaluated based on individual component tests, the full-scale prototype test, and parallel diagnostic analyses. The importance of a realistic assessment of these parameters in a capacity design approach for structural wall buildings was evaluated. The outline for rational design models which allow a prediction of the complex behavior characteristics of structural wall buildings for all design limit states is presented in this paper.

Discusses aspects of the design of connections in reinforced concrete frame structures which often get overlooked. The need for careful assessment and detailing of slab-column connections in flat plate structures combined with walls is addressed. The way in which the strength and stiffness of spandrel beams can significantly alter the expected response of beam-column connections is illustrated by experimental results and observed seismic damage. Detailed analysis of beam-column joint regions using the modified compression field theory demonstrates behavioral features that have important design implications. The use of nonlinear finite element modelling of joint regions to design efficient, yet practical, retrofit measures is discussed. An alternate form of construction using ductile steel link beams to connect reinforced concrete walls is presented. The important design features for the connection of these beams to the walls are highlighted.

Reinforced concrete structural walls may provide efficient earthquake resistance in multistory buildings. In Europe, they are commonly combined with gravity load dominated slender columns in which the entire horizontal action is taken by the walls. In recent years, it became possible to design reinforced concrete structural walls in a clear manner according to the capacity design method which is based on an "elastic" equivalent static force reduced by a global displacement ductility factor and by an overstrength reduction factor. In this paper, a nonlinear dynamic performance check of capacity designed walls was carried out. For this purpose, a newly developed macro model was used for the modelling of the wall. Nonlinear time history analyses were carried out with a ground motion compatible to the elastic design response spectrum of the Swiss Standard SIA 160 as input. The major findings of this paper pertain to three important design aspects as follows. 1. The dynamic rotational ductility demand may have a different distribution over various height to length aspect ratios of the wall than previously anticipated by static analysis. 2. The dynamic bending moment demand over the height of the wall may differ from the static assumption depending on the aspect ratio of the wall. This necessitates a modified moment capacity distribution. 3. The dynamic shear force at the base of the wall may exceed the previous assumptions of the capacity design method.

The New Zealand Standard for design loadings for buildings (NZS4203) was revised in 1992 superseding the earlier standard NZS4203 (1984). Some of the most significant changes in the new code are a considerable increase in the allowable interstory drifts and a marked reduction in the seismic lateral forces for structures with longer natural periods. Designers may now be encouraged to design buildings to the maximum allowable drifts as the resulting buildings will attract smaller lateral loads. Reinforced concrete buildings designed with the new loadings code may be constrained by the minimum reinforcement requirements rather than strength requirement of the loadings code; as a result, they may have a different distribution of strength capacity from that assumed in the code design. Because of this, buildings designed using the capacity design principles may not have the strength distribution that the designer intended. The reasons for this problem are discussed in this paper and the effects of the irregular distribution of strength capacity are investigated using inelastic response analysis. It was found that the large reduction of the design lateral forces resulting from the large allowable interstory drifts may lead to the problem. The design lateral forces or the deflection limits defined in the new code, NZS4203 (1992), may need to be reconsidered.