Pennoni Perspective Volume 22 • Issue 2 • Summer 2018 - Page 5

Lesson 1:  Hurricane Winds Are Gusting Prior to Hurricane Andrew: Building codes dealt with constant velocity winds. Now: Codes are based on 3-second gust winds to more accurately reflect hurricane conditions. Lesson 2:   Door and Window Openings in Exterior Walls Must Be Protected Damage at many of the buildings in South Florida occurred where doors or windows had failed from wind pressure and flying debris. Now: Codes now require approved doors and windows that have been specially engineered and tested or protected with impact resistant coverings. Lesson 3:  Uplift Wind Forces on Roofs are Critical Hurricane winds flowing over and around structures generate significant negative pressures or uplift forces on roof. Before Hurricane Andrew, it was not fully understood that those forces were much greater at the edges and corners of the roof. Now: Codes require engineers to design for significantly higher uplift forces at the edges and corners of roofs and to provide a continuous load path down to the foundations. Lesson 4:   Exterior Corners Are Subject to Increased Wind Forces Hurricane winds flowing around buildings generate higher negative pressure or suction at exterior corners. Now: Codes account for this by calling for higher design criteria for doors, windows, and wall surfaces in these edge zones. Lesson 5:  Gable Roofs Can Be a Real Problem Many of the houses in south Florida that were built with gable type roofs suffered serious damage when the exterior wall at the triangular gable ends failed. Now: Codes mandate structural bracing or a continuous wall height, and hip roofs performed much better during the storm. Lesson 6:  Wind Tunnel Testing Is a Must for Tall Buildings The most accurate way to determine wind loads on a specific building is wind tunnel testing. This is especially important for tall buildings. Wind tunnel testing is conducted by specialized companies who build a scale model of a proposed building along with any structures that surround it. They place the model on a rotating table and blow wind against it in a wind tunnel. Sensors on the subject building record plus and minus wind forces that are converted to design pressures for use by the building designers. The resulting pressures are more accurate and are normally less than the pressures required by code, resulting in cost savings. But What About Flooding? Historically, flooding causes more loss of life and property damage than wind during a hurricane. Since people will always want to live near bodies of water, construction must be regulated through the building codes. The Federal Government encourages proper construction in flood hazard areas by offering lower-cost insurance to homeowners in participating communities through the National Flood Insurance Program (NFIP). The ability of a house or commercial building to survive hurricane force winds is based primarily on the design and construction of the exterior shell (roof, walls, windows, and doors). Damage usually occurs when one of the exterior shell components are breached. Hurricane Andrew was a wake-up call to the entire building construction industry and the lessons learned have been incorporated into the major building codes. The personal knowledge that I gained from studying the storm damage following Hurricane Andrew has allowed Pennoni to become a leading expert in the design of specialized high wind buildings throughout Florida. These code modifications have significantly reduced hurricane damage to structures since Andrew, specifically during the hurricanes that crossed the state of Florida in 2004 and 2005, and as recently as Hurricane Irma in late summer of 2017. PENNONI | 5