February 22, 2001

NC State Researchers Test Breakaway Walls

– Their Findings Are Part of FEMA’s New Coastal Construction Manual

Bertha, Fran, Floyd – meaningful names for North Carolinians, who more than ever are aware of a hurricane’s potential to wreak havoc. Citizens of coastal areas live with this potential every hurricane season. Evacuation can prevent loss of life, but preventing loss of property is more challenging.

To minimize damage from storm surges to buildings in coastal flood zones, the National Flood Insurance Program (NFIP) suggests that such buildings be built on piles, or "stilts," and that the ground floor be used only for access, parking or storage.

Buildings on piles may have unique coastal charm, but homeowners may want to enclose that ground-level space. Because strong walls absorb the surging water, which could jeopardize the whole building’s foundation during a storm, homeowners have been encouraged to use walls that would break away without compromising the structural integrity of the foundation.

To find the proper design of such a wall, NC State researchers Dr. C. C. Tung, professor emeritus of civil engineering; Spencer M. Rogers Jr., senior coastal engineering specialist with North Carolina Sea Grant and inter-institutional adjunct faculty member in civil engineering at NC State; and Dr. Bohumil Kasal, associate professor of wood and paper science, launched a study that involved an elaborate test of eight wall designs using a wave channel at a facility at Oregon State University.

The massive wave channel is 342 feet long, 12 feet wide and 15 feet deep. The research team placed the eight-foot by eight-foot prototype wall sections about one-quarter of the way into the channel and directed increasingly strong waves at the walls until they broke apart. Their findings are included in the Federal Emergency Management Agency’s (FEMA) new Coastal Construction Manual.

These experiments were done with wood breakaway walls, but researchers would like to try using unreinforced, hollow-cell masonry walls in similar experiments. Hollow cinder blocks would have the advantage of not becoming large, floating debris after a hurricane, making cleanup easier and reducing the danger to other buildings. Testing masonry blocks is more difficult than testing wood because of long cure times for the mortar and potential for damage to the wave machine. The next step in this research will be to find a way to test block walls safely.

This research was funded jointly by the National Science Foundation (NSF) and FEMA.

-- rudd --

Technical Contact: Dr. C.C. Tung, 919-515-7695, tung@eos.ncsu.edu
Media Contact: Linda E. Rudd, 919-515-3848, linda_rudd@ncsu.edu

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