On July 28 the Pacific Earthquake Engineering Research Center provided the venue for a test of “sobering” proportions. UC Berkeley researchers, lead by civil engineering graduate student Joshua Marrow, performed a series of earthquake shaking table tests on a popular wine barrel stacking system used by vintners throughout California and the western United States. The tests were part of the Wine Industry Seismic Hazard Reduction Project. The intention of the tests was to determine the level of seismic hazard posed to stacked wine barrel inventories and to investigate possible methods to mitigate the hazard. The July 28 test was attended by representatives from the wine industry, the media, and by interested members of the public. Robert Mondavi Winery contributed the wine barrels.
Barrel-Rack System
The wine barrel stacking system consists of a welded steel barrel rack that, depending on the configuration, will hold either two or four 60-gal oak wine barrels. The rack-barrel combinations are carried by forklifts and placed in vertical stacks up to 6 barrels high, approximately 18.5 ft tall. The wine industry uses this system for two main reasons: (1) it provides easy access to the barrels for topping and maintenance and (2) it provides the best available alternative for high-density storage of wine barrels—with the growing size of the industry, an extremely important issue.
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Fig. 1. Two barrel stacks used to investigate the effects of pounding. |
Each barrel weighs about 600 pounds and is worth approximately $600. The value
of a filled barrel is around $3000. Many cellars in California contain between
40,000 and 60,000 wine barrels. The value is therefore immense and the losses
could be catastrophic in an earthquake.
Shaking Table Tests
Over a period of one month the barrel stacks at PEER were subjected to a variety
of earthquake ground motions. The barrels were stacked in various configurations
to emulate the vast number of ways the industry utilizes the system. Stack heights
of between 4 and 6 levels were tested. A series of safety tethers were devised
to provide protection for onlookers and the shaking table in the event that
the barrel stacks toppled. The tethers were designed for the shaking table tests
only and were not intended to be a viable method of mitigation in the wine cellars.
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Fig. 2. Barrel stack on shake table after earthquake simulation test. |
Observations and
Conclusions
The implications of the effects of a major earthquake on the wine industry
are considerable. The full economic impact of the wine industry on the State
of California totals $33 billion, counting revenues to the wine industry and
allied industries, direct, indirect, and induced economic benefits. Outside
of California, the sale and distribution of California wines generates an additional
$5.7 billion in sales revenue and $1.6 million in taxes, providing additional
value and employment worldwide. Wine is California’s most valuable finished
agricultural product. If a winery were to sustain major damage in an earthquake,
it might never be able to recover financially. The likelihood of this outcome
is because the wine industry has the longest return on investment of any agricultural
industry, between 2 and 5 years. The wineries’ entire source of profit
lies upon the barrel-stacking system.
Although the barrel stacks did not display an adequate level of seismic performance, the researchers labeled the tests as an overwhelming success. The testing brought important insights into the behavior of the system that researchers are confident can be used to provide a series of recommendations to help the wine industry mitigate losses in a great earthquake.
To document the progress of their work, the author has developed a comprehensive
website at http://www.eresonant.com.
Joshua Marrow
Graduate Student
Department of Civil and Environmental Engineering
University of California, Berkelety