Scientists Build Homes That Keep Hurricanes From Raising the Roof
BOSTON — A HEADSTRONG hurricane season is spurring renewed efforts to find ways to keep storms from turning homes into heaps of plywood.
In the name of science and better construction techniques, researchers in South Carolina are pummeling roofs and walls with bursts of air in a university wind tunnel.
On the gusty plains of Lubbock, Texas, engineers have fitted an outdoor building with stress gauges to determine the impact of strong winds on an entire structure.
In Idaho, scientists want to set up a test facility that will use the thrusts of eight turboprop engines to help sort out everything from the number of nails to use in fastening walls to what keeps homes on foundations.
All are part of a growing effort to improve knowledge about what many consider a largely overlooked area of science and engineering. While some $100 million a year is now put into earthquake research, for instance, only $2 million to $3 million in federal funds goes into wind research.
Interest is growing, though. Next month, participants are expected to break ground on a construction-industry training facility in Southern Shores, N.C., as part of Project Blue Sky. A $2.1-million collaboration between federal, academic, and private sectors, it will explore stronger materials and sturdier construction techniques.
The training program will draw on the results of wind research conducted by the partners, which include Clemson University, the Federal Emergency Management Agency (FEMA), and private companies. Bob Shea, who oversees hazard mitigation projects for FEMA, calls Blue Sky "unique" in its objectives as well as its collaborative approach.
Several factors are prompting these and other wind-hazard reduction efforts. Not the least is America's love affair with seacoasts. Some 55 million people now live within 75 miles of a coastline, according to FEMA. By the end of the decade, that number is expected to reach about 90 million.
At the same time, people are beginning to realize that when it comes to natural disasters, wind is public enemy No. 1. Between 1985 and 1994, "70 percent of catastrophe-claim payments were paid out as a result of wind-related events," says Dick Griebel, spokesman for the Boston-based Insurance Institute for Property Loss Reduction.
Moreover, as scientific consensus builds on global warming, insurers and emergency planners are trying to anticipate the effects climate change may have on the frequency and intensity of storms. Researchers, too, still face a dearth of basic data on how wind and small-scale structures interact. Much of what is known about wind and buildings is based on wind-tunnel tests for skyscrapers, says Rita Knorr, managing director of technical activities for the American Society of Civil Engineers.
Ben Sill, coordinator for Clemson University's Wind Load Test Facility, adds: "Houses and small buildings have gotten the short end of the stick."
As a result, building codes may not include the most cost-effective requirements for protecting structures against wind damage.
For example, Florida's Dade and Broward Counties, which have the toughest hurricane building codes in the country, require that windows withstand the impact of a two-by-four shot from an air cannon and traveling at 34 m.p.h. Yet Mr. Sill points out that this approach is derived from one used to test the strength of containment buildings for nuclear-power plants. Bits of roofing tile, and even coconuts, might be more realistic projectiles, he adds.
The data gaps fall into three broad areas, engineers say: the loads wind can place on various parts of a building, the ability of different designs to resist those loads, and detailed wind profiles for specific regions or communities.
To get at the first two issues, Clemson researchers use a wind tunnel combined with BRERWULF, a three-sided chamber whose air pressure can be rapidly altered to simulate wind gusts. The chamber allows engineers to test different construction approaches on sections of full-sized walls or roofs, which in effect make up the chamber's fourth "wall."
"Our initial activity was to look at roof-to-rafter connections," says Scott Schiff, associate professor of civil engineering at Clemson. "This spring, we'll be starting tests on wall systems with windows installed."
Yet BRERWULF can only test sections of major components such as walls or roofs. The missing element, nearly everyone agrees, is a wind facility that allows tests on full-scale buildings.
The closest thing to a full-scale test site in the United States is the open-field facility in Lubbock. There, Texas Tech engineers have put a heavily instrumented metal building on a movable platform. "We get some strong winds in the late fall, winter, and early spring," says Doug Smith, an engineering professor engineering.
Yet even that fails to give researchers the range and control they'd like to have over experiments.
To remedy that, Clemson, Texas A&M University, and Notre Dame University have teamed up on the "wall of wind" project, which would establish a full-scale test facility at the Idaho National Engineering Laboratory. It will use eight engines from "Bear" strategic bombers flown by the former Soviet Union's Air Force, says Tim Reinhold, an assistant professor of civil engineering at Clemson and the coordinator for the project.
The lab also would conduct mechanical stress tests on structures, as well as cost analyses on various construction techniques. Work on the project will begin in December.