Wind Pressure Mitigation on Gable Roofs for Low-Rise Buildings Using Spoilers

Abstract

Previous wind disaster investigations have indicated that the roof systems of low-rise buildings often suffer severe damage under the negative wind pressure caused by the sharp corners between the walls and the roof. Technical mitigation has been demonstrated to be efficient for decreasing the peak and mean wind pressure on the roof system through mounting mitigation devices or modifying the roof geometry. Previous studies on low-rise buildings were conducted primarily for flat roofs, and the wind pressure effect on the mitigation device itself was not considered. The current study conducted wind tunnel tests for a low-rise gable-roof building with spoilers to investigate the wind pressure mitigation effect on the roof region. Several influencing factors including the height, width, angles and positions (at the eave, gable wall, and ridge) were taken into account. In particular, the wind pressure on the spoilers themselves was measured to comprehensively evaluate the uplift force for a roof system involving the roof region and spoilers. The test results showed that the spoilers at the gable wall mitigate wind pressure the most, followed by the spoilers at the eave; a spoiler at the ridge showed no noticeable decrease in the wind pressure on the roof. Relative to the width and height of the spoilers, the angle of the spoilers had the strongest influence on the wind pressure reduction, with the recommended angles of ° for spoilers at the eave and 1–25° for spoilers at the gable wall. Considering the economic concerns and construction details, the recommended height of a spoiler is .2 to .6 m, and the recommended width is 1/2 of the length of the whole building. Although a spoiler can effectively mitigate the wind pressure on the gable roof region of a low-rise building, the test results revealed that this configuration creates a relatively large uplift force that is transmitted to the roof system. Thus, it is recommended that the increased uplift force over the entire roof system including spoilers be considered under extreme wind loads in the design stage.