Nonlinear Seismic Analysis and Design of Reinforced Concrete Buildings: Supplementary Proceedings of a Workshop Held in Bled, Slovenia, July 13-16, 1992

An international workshop on Nonlinear Seismic Analysis of Reinforced Concrete Buildings was held in Bled, Slovenia, on July 13-16, 1992. The workshop focused on the following two topics of much relevance to the seismic protection of reinforced concrete structures:

(a) Energy concepts and damage models in seismic analysis and design

(b) Analysis and seismic behavior of buildings with structural walls


The two topics were selected because of their importance in seismic design and the need for an evaluation and dissemination of recent advances in these areas. It has long been recognized that energy input, absorption, and dissipation are the most fundamental quantities controlling seismic performance. Already in the late 1950's G.W. Housner proposed "a limit design type of analysis to ensure that there was sufficient energy-absorbing capacity to give an adequate factor of safety against collapse in the event of extremely strong ground motion". In 1960 John A. Blume, in his classical paper on the Reserve Energy Technique (2WCEE), states that "with the procedures outlined, the anomalies of a great deal of apparently baffling earthquake history can be explained as can the gap between elastic spectral data and the capacity to resist earthquakes". However, to this day, energy concepts have been ignored in earthquake resistant design because of apparent complexities in the quantification of energy demands and capacities and their implementation in the design process.


In many countries extensive use is made of structural walls (shear walls) to increase the strength and stiffness of lateral load resisting systems. 'Recent earthquakes have often indicated better performance of multistory buildings containing structural walls compared to buildings whose structural system consists of frames alone. Clearly, this observation cannot be generalized since seismic performance is affected greatly by wall layout, strength, and detailing, as well as by the primary deformation mode (bending versus shear). Although the great importance of walls in seismic performance has long been recognized, mathematical modeling of the nonlinear static and dynamic response of structures containing walls is only in the development stage.

The invited contributions written for the workshop are archived in two publications. The majority of papers can be found in the book Nonlinear Seismic Analysis and Design of Reinforced Concrete Buildings, (P. Fajfar and H. Krawinkler, editors), Elsevier Applied Science, London and New York, 1992. Additional papers submitted at the time of the workshop, together with written discussions and conclusions, are presented in this report.


The papers on energy concepts and damage models illustrate how energy terms together with cumulative damage models can be utilized to provide quantitative information useful for damage assessment and design. It is hoped that a study of these papers leaves the reader with the impression that an explicit consideration of energy principles is a viable concept that can be incorporated in the design process. It must be pointed out, however, that much more research is needed in order to implement this concept in design practice.


Many of the papers address important design and modeling problems for structural walls and buildings that rely on the participation of walls in seismic resistance. The papers illustrate the complexity of the problems but also propose solution techniques intended to contribute to a more accurate prediction of the seismic behavior of buildings containing structural walls.

The two publications discuss selected issues of importance in the seismic design of reinforced concrete buildings. They lay no claim to providing final solutions to any of the problems investigated and probably raise more questions than they answer. Their purpose is
to form a basis for discussion on the state-of-the-knowledge and research and implementation needs. It is hoped that the workshop and both publications will make a contribution towards the achievement of the goals of the International Decade for Natural Disaster Reduction (IDNDR).


We are deeply indebted to the authors who have written original and thoughtful contributions for both publications and participated in the workshop. The conclusions on the Behavior of Buildings with Structural Walls were provided by Professors Matej Fischinger and James O. Jirsa. Their contribution is most gratefully acknowledged. We are also much indebted to Elsevier Science Publishers Ltd who made the first publication available in a timely manner. Sponsorship for the workshop was provided by the former U.S.-Yugoslav Joint Fund for Scientific and Technical Cooperation in conjunction with the U.S. National Science Foundation and the U.S. National Institute of Standards and Technology, by the Ministry for Science and Technology of the Republic of Slovenia, and the Slovenian Academy for Sciences and Arts. This support is gratefully acknowledged.


The workshop in Bled was organized by the Institute for Structural and Earthquake Engineering at the Department of Civil Engineering, University of Ljubljana. We are most grateful to the staff of this Institute, headed by Professor Janez Reflak, for the excellent organization of the workshop.