What made Ian unique was its deadly combination of storm surge and catastrophic high winds. A storm surge with an inundation of an unprecedented 3 to 5.4 m (12 to 18 ft) above-ground level was reported along the southwestern Florida coast, and Ft. Myers itself was hit particularly hard with a record-high surge. High watermarks on Ft. Myers Beach reached nearly 4.8 (16 ft) in spots, according to a study by the U.S. Geological Survey. According to the Insurance Institute for Business & Home Safety (IBHS), water surge is always far more damaging than wind. “Water simply weighs more than wind. Complete structural failure can be common in the surge zone, leading to far more damage than wind alone,” says Dr. Ian Giammanco, managing director of standards and analytics at IBHS.
Designing better structures for the future
Following the aftermath of Hurricane Andrew in 1992, an entirely new category of products testing was born. In hurricane-prone regions, architects, engineers, and owners face multiple design and safety challenges related to the building envelope and its ability to withstand severe storm and hurricane-force winds and water intrusion. The combination of intense wind, storm surge flooding, and heavy rainfall can lead to the type of damage seen during Hurricane Ian and many other recent hurricanes.
Many advances in understanding how high winds and water affect structures begin at the test lab. Manufacturers must ensure their building products meet code compliance to be used in hurricane-prone areas, including the high-velocity hurricane zone (HVHZ). Hurricane zones are typically defined by the geographical location of the building, which is defined in part by The American Society of Civil Engineers’ (ASCE’) wind speed map—ASCE 7. Florida has implemented some of the toughest product approvals in the world, specifically Miami-Dade County, and the need to receive either a notice of approval (NOA) or a Florida Product Approval (FPA).
The FBC are administered by the Florida Building Commission. The FBC is based on the International Building Code (IBC), which is used across the U.S. As a result of the destruction caused by Hurricane Andrew in 1992, the state of Florida designates various wind zones to mandate product approvals. The FBC created the HVHZ and includes Miami-Dade and Broward counties with ultimate design wind speeds higher than 273 km/h (170 mph). Wind zones 1, 2, and 3 are defined for ultimate wind speeds ranging from 209 to 273 km/h (130 to 170 mph).
The most common test for the hurricane market is the impact and cycling test, designed to simulate windborne debris striking a window or an element of the building during a hurricane. Providing protection from flying debris that breaches the building envelope is critical. If a structure’s envelope is breached, wind can enter the building, creating pressure changes that can lead to destruction of the contents in a building and to the building structure itself. Also, a breached opening can allow water into the building causing water damage throughout. Impact and cycling tests simulate the hurricane act of flying debris and the rapid increase and decrease in pressure.
The weakest links in a building envelope are windows, doors, soffits, and ridges vents on roofs. For windows and doors, the impact test consists of firing a 2×4 projectile at predetermined locations. The cycling portion of the test is conducted after the impact test with no penetrations and consists of 9,000 cycles of positive and negative pressures.
