By Jorge E. Sciupac, AIA
Among the main causes of damage to historic structures are natural disastersand among the most serious of natural disasters are earthquakes. In the historic city center of Quito, Ecuador, evidence of their destructive power is not hard to find. Recognized by the United Nations as a "World Heritage Site," Quito has sustained more than its share of earthquakes during its 460 years of recorded history. The latest one in 1987 had a serious impact on many of the city's historic buildings, including churches and monuments.
Prior to 1987, most of the conservation work done in Quito in the wake of earthquakes focused on repairs and architectural restorations. After 1987, seismic stabilization efforts became more comprehensive and prevention oriented. By 1993, the authorities, experts, and institutions involved recognized the need to carefully evaluate existing work, correct mistakes, and explore alternative strategies.
With the objective of sharing information and experiences on seismic stabilization, the Getty Conservation Institute, the Municipality of Quito, the Fondo de Salvamento, and the Fundación Caspicara sponsored an international colloquium on the "Seismic Protection of Historic Buildings and Monuments." The colloquium, held May 31 through June 3, 1993, was officially opened by Dr. Jamil Mahuad Witt, Mayor of Quito, and the two presidents of the colloquium, Dora Arízaga, Director of the Fondo de Salvamento, and Neville Agnew, Special Projects Director of the Getty Conservation Institute.
"Earthquakes are unavoidable," said Mayor Mahuad in his opening remarks, "but we have to be accountable. What have we done to be prepared? What actions have we taken to prevent the consequences?"
Architects, engineers, and scientists from Ecuador and other earthquake-prone countries such as Mexico, Turkey, Macedonia, and the United States attended the colloquium. Presentations addressed a variety of issues, including: the relationship between natural disasters and conservation of cultural heritage; preventive actions; examples of consolidation, rehabilitation, and reinforcement of monuments in Mexico, California, and Quito; computerized and analytical methodologies; seismic strengthening analysis and techniques; differing approaches of architects and engineers; social and political pressures on conservation activities; and the ethics of structural interventions.
A vigorous debate during the colloquium centered on a plan for the structural restoration of La Compañía de Jesús. This church is one of Quito's most significant monuments, and its artistic, cultural, and historical value is widely recognized throughout the world. Because the plan for stabilization includes the use of exposed tensors (rigid steel cables that provide strengthening), there was much discussion regarding this intervention's aesthetic, structural, historical, and ethical implications. Arguments were made for alternative technical solutions.
The discussion exposed some of the philosophical gaps between architecture and engineering on matters of conservation, in particular the difficulty of reconciling aesthetic and historical considerations with structural needs. Generally, conservation architects are more concerned with respecting the original aesthetic, material, and technology of buildings: minimum intervention is considered the best intervention. Some engineers, on the other hand, are more occupied with safety issues, and are interested in using modern techniques and materials to strengthen historic buildings, as long as the structures appear unchanged.
Another area of debate was the application of computer-based modeling for the design and calculation of structural stabilization of historic buildings. The issue was raised during a presentation describing the computer modeling used in the rehabilitation of the Mexico City Cathedral. The controversy in this case was not only about the practicality of such a sophisticated methodology (given the limited resources and expertise available for its use), but also its conceptual validity. The question raised was which approach was a better predictor of a building's behavior under seismic stress: a theoretical and individual examination of a building's parts, or observation of the building's behavior as an integrated whole? The answer to this question has significant implications in the type of seismic strengthening solutions proposed.
Participants agreed on the need for specialists in Quito to develop a scientific data base of seismic and geologic information, and also materials behavior. This multidisciplinary library should include studies, tests, methods, and most of all, statistical data of ground and structure behaviors. The available resources and local conditions are obviously of great value to the professional charged with proposing solutions for the protection of non-replaceable historical structures.
"Each problem needs a singular solution," stated Fernando Merino, President of the Ecuadorian Association of Structural Engineers, at the colloquium's conclusion. That being said, participants acknowledged in their final discussions that the quality of information exchange during the proceedings would help to guide them in the search for those singular solutions. By the end of the gathering the process of revising some of the proposals presented had already begun, and the institutions sponsoring the event were considering additional programs to further disseminate information on seismic stabilization methods. Indeed, in the following months, the Getty Conservation Institute's Training Program will offer a workshop on seismic issues.
Jorge E. Sciupac, AIA, a consultant to the Getty Conservation Institute, is an architect specializing in historic buildings and their seismic reinforcement.