Full Scale and Wind Tunnel Testing of Rooftop Equipment on a Flat Roof

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Damage surveys performed during recent hurricane seasons have identified rooftop equipment as a primary point of failure on low rise building envelopes. Rooftop equipment failures caused by high winds have resulted in millions of dollars worth of damage to buildings, primarily from water infiltration into large openings exposed by detached rooftop equipment, wind-borne debris damages caused by blown-off rooftop equipment, and delays in post-storm building re-occupancy due to subsequent mold and mildew infestations attributed to water infiltration. These observations indicate that existing rooftop equipment wind load design methodologies and anchorage techniques may not be adequate to withstand severe wind loads. The objective of this study was to obtain realistic wind loading data for rooftop equipment by conducting full scale and wind tunnel experiments on typically sized roof-mounted air conditioning (a/c) units. Wind loads on full scale rooftop a/c units were measured using the 6fan Wall of Wind (WoW) hurricane simulator at Florida International University (FIU). The full scale study considered three a/c condenser units placed on the roof of a low rise building model having a flat slope. The a/c units were instrumented with force and pressure sensors to capture the aerodynamic loading effects. A similar investigation was carried out in a boundary layer wind tunnel (BLWT) at a scale of 1:10. The wind tunnel a/c unit models were instrumented with 32 pressure taps each, and the pressure integration method was used to calculate the net aerodynamic loading effects. Preliminary results indicate that the force and moment coefficients obtained from the full scale and model scale studies are in reasonable agreement when rooftop a/c units are away from the edges of the roof.