International Concrete Abstracts Portal

Gives an outline of the many significant and pioneering contributions made by Emeritus Professor Tom Paulay to the understanding of the behavior of reinforced concrete and to the design of reinforced concrete structures for earthquake resistance. Particularly innovative has been his research into the design of structural walls for earthquake resistance, including the concept of the use of diagonal reinforcement in coupling beams. Other internationally recognized research described include his outstanding investigations into the mechanisms of shear resistance of reinforced concrete, aggregate interlock across cracks, behavior of beam-column joints, and the capacity design and detailing procedures for structural walls and frames.

The M7.8 earthquake which hit the Philippines in July 1990 caused extensive and varied damage to a wide range of structures, most of which were of reinforced concrete. Because U. S. codes are adopted in the Philippines, the event provides a unique opportunity for earthquake engineers worldwide to review their approaches to seismic design. This paper results from the author's involvement in a visit immediately after the event and his subsequent role, in 1991 and 1992, advising the Philippine government on reconstruction of damaged public buildings and infrastructure. Valuable insights into the real issues were gained through contact local consultants, government engineers, and government agencies, such as the Departments of Health and Education. The government's Earthquake Reconstruction Project is outlined and the effects of the earthquake briefly described as an introduction to the main issues: structural concepts, ductile detailing, construction practice and supervision, influence of "nonstructural" elements, and the value of site investigations. Examples are given to illustrate these issues in the Philippine context. The author concludes that proper attention to the basics is sufficient to significantly reduce earthquake risk, not only in the Philippines, but in many developing and other countries. In this International Decade for Natural Disaster Reduction, this has special relevance.

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.