LEARNING FROM EARTHQUAKES TO IMPROVE REHABILITATION GUIDELINES FOR REINFORCED CONCRETE BUILDINGS

Development of design guidelines and updating of such documents is usually accomplished through a combination of laboratory studies and field experience. In the case of rehabilitation design, the problems are complex and the variety of different situations is immense. Furthermore, the issues are not easily studied in parts or in small scale because of the complexity of the interactions between different elements of the existing structure and between the existing structure and new elements added during rehabilitation. As a result, one of the best sources of information for understanding the behavior of existing structures before or after rehabilitation is reconnaissance studies after an earthquake occurs. Following the 1985 earthquake, several projects related to rehabilitation of structures were funded as part of the Mexico/US joint research effort. These projects involved both experimental studies and on-site visits to Mexico City to learn from the Mexican structural engineering community as much as possible about the massive repair and retrofit activities that followed the 1985 event. The objective of this presentation is to describe some of those activities. In 1989, a Workshop was organized to bring together Mexican and US engineers engaged in rehabilitation design and research to exchange ideas and discuss the state of the art. The participants visited buildings that had been rehabilitated or were in the process of being strengthened or repaired. At each site, engineers involved with the construction were available to lead the tour and to discuss details and objectives of their designs. The Workshop concluded with a round-table discussion from which it was concluded that a record of various case studies should be developed. The National Science Foundation provided funding for developing such a report. As a result, the experience of the workshop was made available to other engineers and included sufficient detail so that the performance of the rehabilitated buildings could be assessed better following future events. Perhaps the most significant aspect of the workshop and report was the willingness of the Mexican engineers to discuss their concepts, problems, and frustrations with US engineers. The mutual understanding of the challenges of rehabilitation of existing buildings led to professional and personal friendships that have lasted long after the original Workshop. The 1985 Mexico earthquake provided the impetus for a significant expansion of research and designrelated activities related to rehabilitation in the US. The data that was generated provided much of the basic technical information that was used in developing procedures for evaluation and rehabilitation design of existing buildings under the sponsorship of FEMA. Similar opportunities occurred after the Kobe, Northridge, and Izmit earthquakes. The purpose of this paper is to outline the importance of studying earthquake damage to improve our understanding of the weaknesses in existing buildings, developing practical design and construction solutions for mitigating the hazards posed by the large inventory of existing buildings in seismic zones around the world, and the need to collaborative efforts to share this information.