In the aftermath of one of the strongest earthquakes on record, the world has turned its eyes to Chile and has been amazed at how relatively little structural damage was done in comparison with lesser quakes in other parts of the world. I asked my friend Sebastian Gray, an architect and professor at the Universidad Católica de Chile, for answers to the many questions on my mind about issues of architectural safety, earthquake resistance, and seismic considerations in Chilean building codes and structural design.
First: where is the safest place in the house? Structurally speaking, are there places that people can easily identify that would naturally be stronger than others?
The safest place would be beneath a reinforced concrete lintel, that is, a lintel formed by structural walls and a structural beam (these are usually thicker than a partition and easy to spot in a dwelling). In any case, stay away from tall furniture and open shelves. Running through hallways and staircases is not advisable.
** See the American Red Cross earthquake preparedness guide for more information.
When did Chilean building codes first take seismic activity into account? It would seem that perhaps even before the official codes existed, people knew not to construct higher than 1 story, or 2 at the most. Were the first building codes related to a specific earthquake?
The Chilean building code (the “Ley General de Urbanismo y Construcciones,” which falls under the control of the Ministry of Housing and Urban Development) was enforced after the Chillán earthquake in 1939 and perfected after the Valdivia earthquake in 1960. Many buildings of up to 9 floors were erected before 1960 (think of the vast downtown area, under the Brunner ordinance). The first tall building in Chile was the Endesa Tower on Santa Rosa Avenue. The improved code of 1960 stipulates that buildings must withstand a magnitude 9 earthquake or higher without collapsing, even if they are damaged so badly they must later be condemned.
Despite the code, some buildings did fall, most notably the one in Maipú and the other in Concepción. In your opinion, was this due to problems with the code, code enforcement, or something else?
Code enforcement, clearly. This appears to be a matter of a relaxation in building procedures and hasty construction, which is the responsibility of builders and developers, rather than a matter of structural design or the quality of materials, which are not an issue here. As part of the deregulation policies of the neoliberal economic model enacted in the 1980s, local authorities and professional associations were deprived of direct on-site supervision powers in the 1980s.
Structural design in Chile is reliable, based on state-of-the-art technologies, and has even developed innovations adopted in other regions around the world.
Do you anticipate adjustments to the building code following this quake?
I hope so, particularly in the project revision and on-site supervision powers of local authorities and professional associations, all of which existed until the 1980s.
How have the technology and theories changed over the years with respect to architecture in areas at risk for earthquakes?
The basic theoretical principles are rather simple and date back to the beginning of civilization. The use of reinforced concrete has been the single most important improvement in seismic construction. Other improvements include compulsory analysis of soil mechanics, sophisticated structural performance modeling, and the use of shock-absorbing devices, especially in high-rise buildings.
How does Chile stand up in terms of its building codes and architecture in general with respect to the other countries in the earthquake-prone Pacific Rim–also known as the Pacific Ring of Fire?
Chile’s building code is based on the most stringent international norms and regulates structural engineering design standards as well as the quality of building materials and construction procedures.
Do Chilean architectural students have courses in seismology?
Students are trained in basic structural design. They are expected to understand the general criteria required. However, structural stability, particularly in larger buildings, is always the responsibility of a structural engineer.
How well do you think Chile’s buildings did in the face of this 8.8 earthquake? Would San Francisco or Tokyo have fared better? I keep wondering what the outcome would have been if something like this had happened in New York, for example. Of course there’s no real reason to build anti-seismic structures there, but do building codes in areas at less risk to earthquakes take similar precautions anyway?
Modern buildings seem to have fared very well. Only one building actually collapsed (the one in Concepción). It toppled rather than crumbled, which appears to be more of a foundation design problem. The few buildings that sustained heavy damage and may be condemned (fewer than 30 in Santiago, according to unofficial information) did not collapse, which is the ultimate purpose of seismic design.
All buildings, and especially high-rises, regardless of their location in the world, must be designed to withstand overloads and lateral forces, such as earthquakes or strong winds.
You told me you were working on ways to protect national heritage–patrimonio nacional–with respect to its adobe architecture. Could you please explain a bit? I’ve heard that the original vernacular Chilean colonial-style home developed precisely because it WAS earthquake resistant, but that over time people started reducing the thickness of the walls and changing the design and that is why adobe homes are no longer considered safe. Your thoughts on that?
I’m concerned with not just the protection of surviving adobe structures, but the identical reconstruction of fallen buildings so that they will maintain their general appearance and urban character, as they are an intrinsic part of our national cultural identity. This is a difficult task, because adobe has always been a very limited material in terms of resistance to earthquakes.
Adobe was the only and most efficient material available for centuries, and they built with it as best as they could. Historically accurate earthquake-proof reconstruction would demand the use of mixed building techniques, for example with concealed supporting structures made of wood or steel, resistant wrapping materials, or some reinforced concrete elements. One serious hurdle I see is financial, as adobe buildings are much larger and bulkier than the contemporary standards. In any case, the most resistant structure would always be made out of reinforced concrete.
For more information, see Sebastian Gray’s New York Times Op-Ed piece: Santiago Stands Firm, March 1, 2010, in which he discusses the earthquake and the great loss of national heritage. He concludes by saying:
“For Chilean architects, this is the challenge of a lifetime: to restore beauty, to preserve history, to build sensibly.”