Magazine article Editor & Publisher

Designing for Press Survival; Base Isolation Protects Mexican Newspaper's Press from Earthquakes

Magazine article Editor & Publisher

Designing for Press Survival; Base Isolation Protects Mexican Newspaper's Press from Earthquakes

Article excerpt

ALREADY ONE OF Mexico's strongest and most innovative newspaper companies, the publisher of Monterrey's El Norte and El Sol made a substantial contribution to the launch of the Mexico City daily Reforma in late 1992.

To help ensure the young paper's uninterrupted publication, Consorcio Interamericano de Communicacion S.A. (CICSA), a separate company headed by the Monterrey publisher's general director, made a further investment to protect its printing press.

CICSA hired Monterrey-based GT Implementacion Antisismica S.A. de C.V. to devise a way to keep its Goss Headliner Offset press operable in the event of an earthquake. The press, which had printed the Sacramento Union until that paper's sate and eventual closure, was to be installed in a new production plant.

The plant was completed a year after launch, leaving no time to build in earthquake resistance. GT-IA's job was to design an isolation system solely for the press, although its president, Federico Garza-Tamez, said he would have preferred to isolate the entire press hall.

Equipped with project reports, test results, videos and photos at their Nexpo booth in Atlanta, Garza-Tamez and his son, Hugo Garza-Martinez, explained their system and work for Reforma - but not before describing the. result: When a 6.6-magnitude quake occurred earlier this year, said Garza-Tamez, the only production plant staffers who didn't scatter for safety were those in the press hall.

The elder Garza explained that the object of base isolation is to prevent or greatly attenuate the transmission of acceleration forces from ground to structure.

In the past, he said, base isolation typically relied on shock-absorbing rubber bearings, sometimes with lead cores. Though capable of reducing seismic effects by 25-30%, he said the method is inadequate for protecting printing equipment. More generally, such an approach suited only to low-rise buildings erected on stiff soils.

Referring specifically to shear, Garza-Tamez said that with his system of isolation, "seismic effects can be reduced up to 96%." The system, added Garza-Martinez, can be applied to new and existing buildings.

A professor of structural engineering at the University of Nuevo Leon, Garza-Tamez said he developed his first base-isolation application in 1993 after years of research. The research culminated in confirmation of the design during tests conducted by the University of Illinois at Urbana on 1/8,-scale nine-story model building on a controlled-vibration table at the U.S. Army Construction Engineering Laboratory in Champaign, Ill. The tests reproduced the characteristics of four recorded North American earthquakes.

Employing base isolators with rods or cables of adjustable length, dampers of adjustable resistance and a wind-restraint device with spring-loaded pin, the GT Base Isolation System was designed to protect high-rise structures and those built on softer soils. The system prevents damaging differences in the rates of movement of different floors in high-rise buildings.

Though a comparatively low structure requiring no wind restraint (in which the pin disengages as soon as a quake strikes to permit some sway), the new plant's press placed considerable weight on the 50 feet of soft, saturated clay below it. Site studies showed that using piles driven down 50 feet for the building's foundation, differential settlements could be as much as two centimeters.

Furthermore, because the plant was built near a seismological station that recorded acceleration of vibration velocity during the great earthquake of September 1985 (8. …

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