Next Thursday is The Great California ShakeOut…
It is not often that we know when the BIG ONE will hit… but Thursday, October 20, 2011 at 10:20am, California is going to be ROCKED!
MHP is, of course, a participant and at our offices, we will be conducting a small test exercise. We encourage you and all our valued clients to do the same, or at the very least, practice protecting yourself during earthquake shaking using Drop! Cover! Hold on! Register yourself or your firm here: http://www.shakeout.org/register/
Be counted in the largest earthquake drill ever, and be the example that motivates others to participate and get prepared!
HEADLINE: September 29, WTTG 5 District of Columbia – (District of Columbia) Engineers find ‘expected ’ damage at monument.
SUMMARY: The team inspecting earthquake damage at the Washington Monument in Washington D.C. is finding ‘expected’ problems with the exterior stones which support the structure. A National Park Service (NPS) spokesman said the agency believes the monument remains structurally sound. “They have identified areas of interest that need further examination.” The monument grounds are closed to tourists.
ANALYSIS: Having been to the top of the Washington Monument on numerous occasions while living on the East Coast, it is with considerable interest that I have watched the stories develop regarding the Virginia Earthquake and, in particular, the inspection of the Monument. My interest is heightened by the fact that I’m a practicing structural engineer in Southern California with ties remaining in the DC area, including my Virginia Professional Engineer’s license. Interestingly enough, early in my career, I had the opportunity to conduct a seismic risk study for another of the large buildings bordering the National Mall. With that understanding comes an awareness that the earthquake which occurred was not outside the realm of possibility or expectation. With the adoption of recent codes such as the International Building Code (IBC) on a more consistent national basis, the potential for, and effects of, earthquake generated ground shaking are becoming better understood and more specifically addressed in areas of our nation outside the “familiar earthquake region” of the West Coast.
When dedicated in 1885, the Washington Monument was the tallest building structure in the world. Although its “tallest structure reign” was cut short by the Eiffel Tower a mere three years later, at just over 555 feet tall the Washington Monument remains the tallest, free standing, unreinforced masonry or stone structure in the world. This means that the structure relies on the bond of the stone units and the mortar between them to maintain integrity. With over 125 years of service, the mortar joints appear to have passed the load test. Of course, with any structure, materials age and points of localized stress develop. Perhaps this begins to explain some of the reasons behind the observed cracks in the stone and loss of mortar beds. It should be noted that this is not unusual or necessarily unexpected. As the article points out, the damage so far observed is ‘expected’. Given the amount of ground shaking and the type of construction, it can be suggested that the Monument performed very well. So, what comes next?
Fortunately, experience with restoration of the Monument is not too far in the distant past. As recently as 1999, a renovation project completely enclosed the Monument in a scaffold so that cleaning of the stone and re-pointing of the mortar joints could be undertaken. Re-pointing is a method whereby old mortar is removed and new material is placed to re-bond joints that may have deteriorated over time or through excessive loading. As with previous renovation projects, some of the actual stone blocks will likely require replacement as well. Considering that masonry and stone buildings have been undergoing renovation for centuries (think of the historic buildings throughout the world), there is a considerable amount of experience to draw from. The process will not be overly complex, but it will be very detailed. With adequate time, energy and a bit of money, the Monument should be back to sharing the views of Washington “soon”.
Ken O’Dell and MHP are Firestorm partners and frequent contributors to the Firestorm Disaster Due Diligence Newsletter. To read the current newsletter in its entirety, view archives of previous Newsletters, or to sign up to receive updates, visit Firestorm Disaster Due Diligence.