By Paul E. Beers
It is hard to believe that next year will be the 20th anniversary of Hurricane Andrew striking South Florida. This was the storm that caused record damage and changed building codes and property insurance markets forever. Today’s building codes in hurricane prone areas of the United States and many areas abroad evolved from the aftermath of Andrew and the efforts to prevent a recurrence of the catastrophic damage that occurred.
In the years since Andrew, many hurricanes have affected urban areas, and it is interesting to look back at the recent history and damages.
The first storm documented to affect a major metropolitan city was actually before Andrew. Hurricane Alicia caused widespread damage to high rise buildings in downtown Houston, TX in 1982. In the aftermath of the storm, researchers found that much of the glass damage was in the middle building floors rather than the top floors, as would have been expected at the time. The cause of the glass damage was determined not to be from high wind pressures, but rather from windborne debris, specifically roof gravel from adjacent roofs. After the storm, there was debate about strengthening building codes to ban roof gravel and require the use of storm shutters and laminated glass, but ultimately no action was taken.
In 1992, Hurricane Andrew caused record damage in Miami-Dade County. Homes were destroyed and commercial buildings were heavily damaged. One of the major causes of damage as determined to be windborne debris. In residential areas, roof tiles blew through windows and doors breaking glass and causing internal pressurization that resulted in the loss of roofs and exterior walls. Commercial buildings were also damaged by windborne debris, resulting in the widespread loss of glass. There were extensive investigations and analyses of the damage and building codes were changed to require protection of windows and doors from windborne debris. This included a performance test where a nine-pound 2×4 timber is fired at windows, doors and storm shutters, followed by 9,000 wind pressure cycles.
Tornados can also cause damage to buildings in urban areas. In 1998 a tornado struck downtown Nashville, TN, damaging many buildings downtown. In 2008, a tornado struck downtown Atlanta, GA, causing damage to high-rise buildings in the downtown area.
The next hurricane to affect major metropolitan areas was Hurricane Wilma in 2005. Wilma was a very large storm that affected Naples, Miami, Ft. Lauderdale and West Palm Beach, Fla. There was façade and glass damage in all areas, particularly in downtown Miami and Fort Lauderdale. Most of the damaged buildings predated the new hurricane codes; however, there were a couple of new code buildings with significant glass loss. Initially there was a loophole in the new codes that allowed the use of heat-strengthened or tempered glass in the upper floors of high-rise buildings, but it was closed shortly thereafter. Most post hurricane code buildings performed very well with no catastrophic damage, proving that the structural portion of the new codes work.
The most recent hurricane to strike an urban area was Hurricane Ike in 2008. Like Hurricane Alicia 24 years earlier in 1982, windborne debris damaged high-rise buildings in downtown Houston. Ike again damaged some of the same buildings that were damaged by Alicia.
History shows that for hurricane and tornado prone areas, the question is not if, but when the next strike will occur. Buildings in South Florida that were designed and built to stronger codes and standards performed well in recent storms. Older buildings with facades that were not upgraded suffered severe damage. Many damaged buildings simply replaced the damaged glass with more of the same. As was demonstrated in Houston, it is only a matter of time before another hurricane strike and more damage.
Correction: This blog originally stated that a tornado struck downtown Atlanta, GA, in 2000. In fact, this tornado occurred in 2008.
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Paul is the Managing Member of Glazing Consultants International, LLC (GCI), a building envelope consulting firm in business since 1988. He has over 25 years experience in the window and glazing trade and with building envelopes. He is a leading expert with glazing systems and hurricane damage and protection and was instrumental in the development and implementation of missile impact tests after Hurricane Andrew hit Dade County, FL. His expertise includes windows, doors, glass and wall claddings with an emphasis on water leakage and damage. He has served as an expert witness in federal and circuit courts for windows, doors, glass and wall systems and water leakage. Paul can be reached at firstname.lastname@example.org.