Date: Wednesday, February 1, 2012
Time: 4:30pm (Refreshments will be served before the Lecture at 4:00 PM)
Location: Stanford University, Li Ka Shing Conference Center – Berg Hall C
Topic: "Challenges for Attaining Earthquake Safety in Developing Countries"
Presenter: Dr. Sergio M. Alcocer, Universidad Nacional Autonoma de Mexico, UNAM
More Information can be found at the Blume Center website.
Over the last years, enforcement of building codes in developing countries has been a major concern of academics, technical societies, practicing engineers and government officials. In Mexico City, for example, aiming at simplifying the process to obtain a building license, in 2004, the city government decided to implement a “Notification Process” applicable for buildings up to 5 stories. In this process, the building owner is only required to inform the local authority about general characteristics of a building to be constructed. This process, in lieu of a building license, has then omitted the formal revision of building drawings and calculations that was typically made and filed by local building officials. The outcome of such process is buildings with evident irregularities in stiffness, strength and/or mass distribution, and excessive lateral flexibility. Buildings with such characteristics were the most affected during the 1985 Mexico City earthquakes, such as soft stories.
The case of taller structures, although different in nature, has led to similar concerns. Indeed, a simple evaluation of the arrangement of reinforcing bars, quality of welds, or detailing of structures, not only indicates poor workmanship in many cases, but worse, a systematic misinterpretation of code requirements. Up to know, reasons for this phenomenon are not clear. Lack of understanding of code requirements, ignorance about effects on structural behavior of assumptions made during analysis and design, and corruption have been discussed as possible reasons. In the opinion of the author, the first two reasons prevail.
Aiming at solving this problem, public offices designed to coordinate the deployment of a full safety assurance system, which involves peer reviews and the development of a building information system that would include final structural drawings, among other relevant information, have been implemented.
Besides the issues indicated above, recent earthquakes in Haiti, Chile, Mexico (Baja California), New Zealand and Japan, have prompted a discussion of the actual safety provided by building code requirements. Design philosophy to attain a building that would remain operational during the design earthquake is one of topics in which agreement has not been reached. Also, the 2011 Tohoku earthquake is an example of a rare event that encompasses several seismic gaps and rupture areas. For such rare earthquakes, the regular size and return periods typically assumed for rupture areas are no longer valid. Magnitudes, intensities and destructive effects may be much higher and extended over larger areas, and a return period for design applications becomes more difficult to develop. Implications of a major quake along subduction zones, extending to areas where recent events have occurred, are under development and study.
In the lecture, a discussion of topics will be presented. Emphasis will be given to buildings formally designed by architects and engineers and to buildings, typically houses, self-constructed without the participation of design professionals. Opinions on how to attain earthquake safety in developing countries will be given.