Forums > Specific Focus > Home, Garden & Construction in Mexico

tomgibbs

Jan 22, 2003, 10:02 PM

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Earthquake and adobe

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.....Colima, where at least 166 homes were badly damaged or destroyed, two deaths in the neighboring state of Jalisco and one in the state of Michoacán. Most of the dead lived in adobe buildings, and most were very poor, very old or very young, ........

Some time ago we had a discussion of adobe building techniques and appropriateness. Someone brought up their fear and reservations to adobe building with all their mass (which is their main performance point) having been through a number of earthquakes in Mexico. Carl Franz brought up a newer method of hybrid adobe, which, if I remember right, was reinforced with standard reinforced concrete post and beam construction.

Maybe Rolly could put an engineer's perspective to the possible Mexican building techniques. Many older Central Mexican buildings that are not adobe are stone, or rubblestone construction. And I've seen quite a few adobe-rubblestone combination walls and buildings in, for example, Penjamo, Guanajuato. Whether one is talking about adobe, stone, concrete, or brick, one is talking about significant mass and potential energy-laden weight. These available Mexican building materials are not resilient materials. Is the standard reinforced concrete and brick structure proving to be the best for quake resistance? Are there equivalent of better options, within the range of available Mexican material options?

tomgibbs

Jan 23, 2003, 7:58 AM

Post #2 of 4 (2939 views)

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Re: [tomgibbs] Earthquake and adobe

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I found an opinion in an international engineering consultant's report from a '95 quake. It says in summary that earthquakes illustrated an inherent hazard in the use of reinforced concrete structures infilled with other materials.

I wonder what this means for reinforced concrete organically shaped shell type structures of the type mentioned here a few weeks ago?

Rolly / Moderator

Jan 23, 2003, 9:30 AM

Post #3 of 4 (2955 views)

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Re: [tomgibbs] Earthquake and adobe

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The most practical earthquake resistant home construction technique is wood frame. A wooden building has considerable ability to flex without failure. The lack of flexibility is the main drawback to brick or adobe construction. The use of a concrete post and beam frame with brick or adobe infill is a reasonable compromise when wood frame construction is not possible, as in Mexico where it would be prohibitively expensive and where there is no fire-fighting infrastructure to protect wooden buildings.

The mortar used to hold the bricks or concrete blocks is very weak and brittle, as are the bricks. If a panel of bricks sustains much flexing during an earthquake (or a ram by a car), the panel will collapse. If there are no concrete columns to frame the panels and support the roof, as in many old adobe buildings, the whole building may collapse. While the loss of part of a brick wall can be dangerous, the collapse of the roof is more likely to be deadly and much more costly to repair.

The key to a safe post and beam building is a very solid foundation on firm ground. One of the reasons Mexico City (or the marina district of San Francisco) sustains so much damage is because of the weak soil structure. There are techniques for isolating the structure from the ground so that the building, in effect, floats above the ground, and thus is largely immune to the effects of the motion of the ground. This technique is commonly used for large buildings in quake-prone areas, but it is too costly to be used in single family dwellings.

The fact that Manzanillo sustained not much residential damage from the very powerful (8+) quake in 1995 shows that properly done post and beam construction is reasonably safe. The fact that so many poured concrete apartment houses collapsed in the Northridge (Los Angeles) quake shows that the construction needs to be properly done.

During the Northridge quake (when I was living 3 miles from the epicenter) few wood frame homes were damaged beyond collapsed fireplace chimneys and minor plaster cracks. Of those wooden homes that suffered serious damage, almost all were the result of improper foundations.

Bottom line: Wood frame construction in Mexico is impractical, so homes are post and beam with brick or block infill. They should be built with careful attention to the foundations and to the quality of the concrete posts and beams. Light weight roofs are desirable. The best earthquake protection comes from not living along the Pacific coast or in Mexico City. – however….

Rolly Pirate

Robertito

Jan 23, 2003, 11:50 AM

Post #4 of 4 (2927 views)

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Re: [tomgibbs] Earthquake and adobe

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My wife and I lived in DF (Talalpan), Cuernavaca and Acapulco during the 1970s through 1980. We, of course, experienced many noisy earthquakes, particularly in Acapulco where I remember several buildings fell as the result of poor (and sometimes fraudulent) construction: coconut shell filling in high-rise piers, for example.

My father-in-law, in a joint-venture with Scott Paper, built a large paper mill next to the Lago de Tezcoco in DF in the 1950s (the lake’s alkaline water was used to make bagasse pulping liquor). The region is prone to earthquakes and subsidence. He built the whole factory as a ferro-concrete steel-reinforced barge. The factory is still operating today without ever having sustained earthquake damage to my knowledge. Keep in mind that each paper machine may weigh more than a hundred tons and needs to always be in precision alignment to avoid shutting down a complicated process. This “barge” had 6 of the large machines as I recall.

Similarly, he added a 350 square meter extension to my in-laws house in Tacubaya, DF built in the same fashion in the late 1950s. It has suffered several earthquakes without any significant damage. A couple of cracked windows (steel framed) occurred in the 1985 DF earthquake and a few knick-knacks fell from shelves: that was it. My mother-in-law still lives there.

We plan to return permanently to Mexico when we retire next year. Being aware that all of western Mexico is part of one big subduction zone, but wanting to live in that region because of the tropical savanna climate (at about 1400 meters), we are thinking of building (or much more preferably buying) a small house of about 200 sq/m or so.

Does anyone have any Mexico experience of building or buying a house with a high quality reinforced slab tied to reinforced structural walls and roof? If so, where?