American Architectural Manufacturers Association

Expert Focuses on Hurricane Simulation Techniques during Fall Meeting; Members Discuss other Important Industry Issues

September 2, 2010

The AAMA Southeast Region Fall Meeting was held in Orlando, Fla. on August 5-6, and it was the perfect venue for a demonstration of state-of-the-art hurricane wind testing, being the home of the University of Florida Wind Engineering Lab in nearby Gainesville. Dr. Forrest Masters (University of Florida) demonstrated the 130 mph hurricane simulator, while dousing the mock-up house test subject with the equivalent of an eight-inch-per-hour rainfall. Use of the simulator for installation testing and for impacting windows with real world projectiles such as roof tiles and three-tab shingles was also demonstrated. To study water penetration, a cyclic test chamber (for testing per the new AAMA 520, Voluntary Specification for Rating the Severe Wind Driven Rain Resistance of Windows, Doors and Unit Skylights) is now capable of mimicking the actual pressure pulses and lateral turbulence of a recorded hurricane.

Masters also reviewed findings from the Precipitation Imaging Probe (PIP), design pressure requirements as they relate to water penetration test pressures and unveiled new research proposals of interest to industry professionals.

Tests conducted in 2008 involved subjecting 34 finished walls with integrated windows to four rounds of pressure loading and water testing:

1. Static
2. Rapidly pulsed
3. Amplitude-and frequency-modulated sinusoidal pressure load sequences
4. A repeat of the static test to ensure that the specimens were not permanently damaged

The results were instructive, indicating that:

• Specimens utilizing windows with compression seals (awning and casement operator types) generally performed better than those with sliding seals (hung and horizontal sliders). The rate of leakage through sliding seal windows was observed to be significantly larger that compression seal windows.
• The rapidly pulsed tests showed no clear advantage over the static test as a diagnostic tool; i.e., conventional test methods as effective as dynamic simulation.
• In 72% of the specimens that leaked, water ingress occurred at the window/wall interface, sill and/or wall, rather than from performance of the window unit considered in isolation, which is the basis for current product approval testing.

Masters concluded that future research needs to be designed to apply realistic rain conditions, noting that the eight-inch per hour rate is much greater than actually experienced in hurricanes, which is more on the order of one to two inches per hour.

Part of the problem is obtaining accurate rainfall data. Masters’ studies found that the impact of large raindrops during heavy rain, as well as acoustic noise, electrical interference and strong winds on the type of disdrometer (a device that measures the size distribution of raindrops) currently used tends to overwhelm the sensor and underestimates the amount of smaller raindrops. He concludes that the effort to accurately define the conditions during a hurricane requires more measuring stations that could collect simultaneous and more accurate measurements of wind and wind-driven raindrop size distribution (RSD).

The proposed next phase would utilize second-generation wind-driven rain (WDR) equipment such as the Parsivel disdrometer made by OTT (Europe’s largest maker of hydrometric systems). Parsivel is a modern laser-based optical system for the measurement of all kinds of precipitation. The precipitation particles are measured optically for size and velocity and differentiated and classified as drizzle, rain, sleet, hail, snow or mixed precipitation. The size spectrum, the amount of precipitation, the equivalent radar reflectivity, the visibility and the kinetic precipitation energy as well as the kind of precipitation are derived from the recorded data. When mounted on a versatile, rapid-deployment, 2.5 m meteorological observing station developed at Texas Tech University, the resulting platforms can be deployed in large numbers, in a short period of time (three minutes or less), and by a small number of people. Originally developed to collect data from supercell thunderstorms, the probes can quickly be adapted to collect data in the hurricane environment. And, although some data resolution is sacrificed, the new platforms are one-tenth the cost of the Generation-one platforms that feature expensive PIP probes. Follow Masters’ hurricane research on Facebook.

The second day’s agenda covered a variety of topics ranging from changes in the new 2010 edition of ASCE 7 and their effect on fenestration design, the Gulf oil spill and oceanic trends driving hurricanes, photovoltaic glass developments and Institute for Business and Home Safety (IBHS) simulation test facility development. In addition, a recap of findings from an exhaustive study on installation techniques that parallel FMA/AAMA 100-07, Standard Practice for the Installation of Windows with Flanges or Mounting Fins in Wood Frame Construction, and FMA/AAMA 200-09, Standard Practice for the Installation of Windows with Frontal Flanges for Surface Barrier Masonry Construction for Extreme Wind/Water Conditions, was provided, as well as upcoming Florida Department of Community Affairs Product Approval process changes mandated by Florida HB 663 that became law this past May, and an update on AAMA activities at the national level, including green certification. The AAMA Southeast Region Technical Committee also discussed issues raised by AAMA’s Accredited Laboratories regarding implementation of the new AAMA 520 standard, including concerns related to rounding error and water capture.

Photos from the the tour of Dr. Forrest Masters Laboratory can be found on the Southeast Region Photos & Applications page.

See article in this issue highlighting the presentations given at the Fall Meeting.

back