Masonry Magazine April 1986 Page. 33
Special Report
Part II
MEXICO
EARTHQUAKE
The major earthquake that rocked Mexico City and surroundings in September, 1985 was one of the worst disasters ever to hit the North American Continent. Here is the conclusion of a special eyewitness report prepared by the IMI investigative team that went to Mexico to assess the monumental damage and loss of lives.
The following is a re-publication of a scientific document released in February, 1986 by the International Masonry Institute describing the structural damage caused by the devastating earthquake that rocked Mexico in September, 1985. This is the second of two parts; Part I appeared in the January/February, 1986 issue of Masonry. Voluminously illustrated, the entire document is available for purchase, at $2.50 per copy, by contacting IMI at 823-15th St., Washington, DC 20005. Masonry is deeply grateful to IMI for its permission to publish this special report as well as for its commitment and dedication to provide this scientific data for the better understanding and improvement of masonry construction is seismic regions.
General Characteristics of Structural Response in Mexico City
# Reinforced Concrete Frames
In the five- to 20-story range, the most common type of construction in Mexico City consists of reinforced concrete frames, often with unreinforced clay brick masonry infills. A common type of infilling is shown in Fig. 3.3. Infilling is often discontinued in the lower stories to permit access to businesses. The resulting soft-story structural system was observed to be susceptible to damage at the lower levels. Corner buildings, in which the infilling is often discontinued on two sides at the lower levels, were particularly heavily damaged, probably due to the additional torsion introduced by eccentricities in plan at the lower levels.
Many reinforced concrete braced frames are also found in Mexico City. Typical bracing configurations are shown in Fig. 3.4. One of the most striking examples of this type of structural system was found in the collapsed Nuevo Leon housing units (Fig. 3.5). The most common floor system is usually a type of waffle slab ("losa reticular"), in which the soffit indentations are filled with lightweight concrete block which are left in place after casting. The resulting floor system is relatively heavy and sus susceptible to local failures around