2014 Napa Earthquake: Learning from ‘Quakes Past

In 2000, researchers at UC Berkeley performed an earthquake simulation not too dissimilar from what we saw in the recent Napa earthquake.  The simulation performed in 2000 was based off a 7.4 magnitude earthquake, and while the Napa earthquake was slightly smaller at 6.2 magnitude, knowing the

devastation that this most recent earthquake caused in wineries indicates to me that the effect was basically the same.

Here’s the video of what happened to barrel stacks during that simulation:  http://www.berkeley.edu/news/features/2000/07/31_video_hi.html

Several years prior, researchers also tested the effects of a similar earthquake on steel tanks.  International vineyard and winery consultant Gary Strachan recalls: “They mounted a tank on a concrete pad that had hydraulic jacks under it and released a video.   They initiated the shaking and could vary the frequency and the amplitude until the tank failed.  It was interesting to see that the tank (filled with water) buckled about 1/3 of the way up the tank and eventually failed from metal fatigue.  This gave them

Photo By USGS [Public domain], via Wikimedia Commons

Photo By USGS [Public domain], via Wikimedia Commons

information for tank construction and also (I assume) how much of a quake would be required to damage a properly constructed tank.  For example, they may require 12 gauge steel for the bottom third and 14 gauge for the top 2/3.”

I have not yet seen the video of this simulation myself, as it is in VHS form and located about 2300 miles away from where I am located right now, but for those that are interested, here is that information:

http://www.worldcat.org/title/earthquake-simulation-test-full-scale-95×20-cylindrical-wine-storage-tanks/oclc/28241201

Learning from ‘quakes past:

This isn’t the first time a wine region has seen devastation caused by an earthquake.  In fact, there are records of several of them, including the 1977 Caucete Earthquake (7.4 magnitude: San Juan province, Argentina), the 1980 Greenville Earthquake (5.8 magnitude: California, USA), the 1984 Morgan Hill Earthquake (6.2 magnitude: California, USA), the 1985 Valparaiso Earthquake (7.5 magnitude: Chile), the 1989 Loma Prieta Earthquake (7.1 magnitude: California, USA), the 2003 San Simeon Earthquake (6.5 magnitude: California, USA), the 2007 Pisco Earthquake (7.9 magnitude: Ica province, Peru), and the 2010 Maule Earthquake (8.8 magnitude: central Chile).

While these earthquakes appear to be “hit and miss”, it is important not to become too complacent about them and to take some precautions in the winery to reduce the likelihood of a major or even total loss of inventory, as we’ve seen in some of the small wineries in the 2014 Napa Earthquake, the damages so far estimated to be in the millions of dollars and growing.

Tanks in an Earthquake:

Several research studies as well as first-hand reporting have well documented what can happen to stainless steel tanks in a winery in the event of an earthquake.  Depending upon the type of stainless steel tank, there are different kinds of damages that can occur after a shaker.  Specifically, it is documented that stainless steel tanks can experience several different types of damage after an

Fig. 11. Typical strong leg-weak wall failure in small tanks without stiffening system at the bottom: (a) 15 m3 LSSS tank; and (b) 10 m3 LSSS tanks. Source: Gonzalez, E. et al, 2013.

Fig. 11. Typical strong leg-weak wall failure in small tanks without stiffening system at the bottom: (a) 15 m3 LSSS tank; and (b) 10 m3 LSSS tanks.
Source: Gonzalez, E. et al, 2013.

earthquake, including (but not limited to) fracture of anchors and elephant foot buckling near the base of the tanks, tank wall fractures, collapse of the top of the tank due to rapid spillage of wine from a fracture, diamond-shaped buckling, tanks “slipping” and pulling pipes down with them, and cracks in welded spots on the tanks.

One study from 2013 found that in the 2010 Maule Earthquake, while all types of stainless steel tanks appear to suffer damage from the 8.8 magnitude quake, leg-supported stainless steel tanks appeared to be the wine storage system most affected.  For a highly detailed analysis on the different types of tanks and the damages seen from the 2010 Maule Earthquake, please read the following paper: “Performance of stainless steel winery tanks during the 02/27/2010 Maule Earthquake” in the journal Engineering Structures.

Barrels in an Earthquake:

The researchers at UC Berkeley, the same from the barrel simulation video shown above, found that there were different types of barrel stack collapse possible in an earthquake, including sliding, rocking of the stack, and ejection of barrels from higher up in the racks resulting in dangerous flying projectiles.  In

Figure 5. Earthquake response of the (2, 3) model: (a) pairs of contact and target bodies; (b) rocking collapse sequence; (c) static and dynamic envelope of normal contact stresses (body 2); and (d) relative horizontal displacement history of bodies 1, 4, and 7 for µrg=0.4 and µrg=0.1. Source: Candia, G. et al 2010.

Figure 5. Earthquake response of the (2, 3) model: (a) pairs of contact and target bodies; (b) rocking collapse sequence; (c) static and dynamic envelope of normal contact stresses (body 2); and (d) relative horizontal displacement history of bodies 1, 4, and 7 for µrg=0.4 and µrg=0.1.
Source: Candia, G. et al 2010.

2008, research presented at the 14th World Conference on Earthquake Engineering in Beijing, China and later published in the journal Earthquake Engineering and Structural Dynamics, found that the forces on a barrel stack that is subjected to ground motions like an earthquake can be upwards of 3 times greater than the normal forces of a barrel at rest.  In other words, fill up a barrel and stack it up on top of several other barrels, and you’re going to have a bad time.

Conclusions and Recommendations:

According to international vineyard and winery consultant, Gary Strachan, “The after-quake chaos in barrel rooms reinforces my recommendation that barrels not be stacked more than two pallets High.   If you are in the premium wine business you must take into account that there is a temperature gradient from floor to ceiling.   The effect is negligible for two pallets but significant for six pallets.    An added bonus is that two pallets would probably have survived the quake.”

It is important to learn from ‘quakes past, and to provide the structure and support necessary to prevent these kinds of damages to the tanks and barrel stacks in the event of another earthquake.  As Gary Strachan suggests, perhaps don’t stack the barrels up so high.  Also, invest in equipment designed to hold barrels in place and anchored against a well-structured wall.  Finally, perhaps experiment more with concrete tanks instead of stainless steel tanks, as the damage to the latter have been shown over and over again to be problematic in major quakes.

What about you all?  Do you have any experience with some of these older quakes, and what sorts of changes have you made in your winery to decrease the odds of major economic damage following a natural event like an earthquake? Those of you currently cleaning up in Napa: have you thought about what steps you will take to protect your winery better in the future?  I’d love to hear your thoughts on this topic!

Sources:

Candia, G., de la Llera, J.C., and Almazán, J.L. 2008. Earthquake simulation and response of wine-barrel stacks. 14th World Conference on Earthquake Engineering. October 12-18th, 2008; Beijing, China. http://www.iitk.ac.in/nicee/wcee/article/14_S02-031.PDF  Accessed online 9/2/2014.

Candia, G., de la Llera, J.C., and Almazán, J.L. 2010. A physical model for dynamic analysis of wine barrel stacks. Earthquake Engineering and Structural Dynamics 39: 1063-1081.

Djermane, M., Zaoui, D., Labbaci, B., and Hammadi, F. 2014. Dynamic buckling of steel tanks under seismic excitation: Numerical evaluation of code provisions. Engineering Structures 70: 181-196.

González, E., Almazán, J., Beltrán, J., Herrera, R., and Sandoval, V. 2013. Performance of stainless steel winery tanks during the 02/27/2010 Maule Earthquake. Engineering Structures 56: 1402-1418.

Shekari, M.R., Khaji, N., and Ahmadi, M.T. 2010. On the seismic behavior of cylindrical base-isolated liquid storage tanks excited by long-period ground motions. Soil Dynamics and Earthquake Engineering 30: 968-980.