Masonry structures built to codes tightened for greater wind loading performed well in the face of Hurricane Katrina, concludes a team of National Concrete Masonry Association and The Masonry Society investigators. Arriving in Mississippi three days after Hurricane Katrina struck, the team observed intact, partially damaged, and demolished structures at sites in Pascagoula, Biloxi, Gulfport and other coastal towns.

“There is a vast improvement in performance of structures built in the past 10 years compared to ones designed according to older codes,” says NCMA's Jason Thompson, structural engineer. Intact masonry structures in Biloxi and Gulfport exhibited wind resistance characteristics that could be expected from structures built according to the IBC 2000 code, he adds. Prominent instances of concrete masonry walls withstanding the hurricane forces were noted at a Gulfport Kmart and Biloxi Wal-Mart store, plus a Harrison County building very near the Biloxi shoreline. Images of those and other projects are posted at www.ncma.org/Katrina, or linked at www.masonrysociety.org

Thompson notes that the IBC 2000 is among the first codes to stipulate wind load design to a factor known as a “three second gust,” which in a concrete masonry wall would require full grouting and vertical rebar of larger diameter than older codes. Leading up to the IBC 2000, wind loading for walls of masonry or other construction subject to high wind loads was based on a “fastest mile” factor that considered only peak gusts. Failures among modern masonry structures in Mississippi suggested that construction was not up to code, team members contend. They observed, for example, demolished block walls with vertical reinforcement but no grout, plus homes or buildings where improper or missing tie-backs led to complete failure of brick veneer, regardless of substrate.

Assisting the NCMA/TMS team were representatives of Birmingham, Ala.-based Block USA, the Southeast's second largest concrete masonry producer and supplier of much gray and architectural block in coastal Mississippi. Leading the team was the University of Louisville's Terence Weigel, Ph.D., who notes, “When catastrophic events like hurricanes damage structures, it is important to conduct an investigation as quickly as possible before clean-up efforts are begun to collect forensic data and determine how well the structures performed. Quick-response field studies conducted following major disasters are vital to identify knowledge gaps where further research and building code revisions are most needed. Such investigations also offer opportunities to make recommendations regarding mitigation measures, disaster preparedness, and emergency responses for better preparing communities for future disasters.”

TMS sponsored the investigation with the Council for Masonry Research. The Society's Coordinator for their Investigating Disasters Program, Art Schultz (University of Minnesota), and President Max Porter (University of Iowa) requested that authorities in the Gulf States region grant the team access to disaster areas and share information with the team members. “These scientific investigations are part of a comprehensive disaster hazard-reduction effort underway and cooperation from local officials enhances the team's effectiveness in carrying out their critical task,” Schultz says, adding that a report of findings is expected to be available from TMS in the near future.