Wind tunnel investigation of wind loads on rooftop model modules for green roofing systems

• Wind loads on rooftop modules was studies through pressure measurement.
• The most unfavorable wind loads on rooftop modules occurs at the corner or edge.
• ASCE7 underestimates wind loads on rooftop modules at the corner or edge.
• Overturning moment coefficients for the module were determined by uplift force.
• Design considerations were proposed including relating roof pressure to module force.

With the increasing popularity of modular green roofing systems, a need was perceived to establish building code requirements for these systems, such as wind resistant performance. However, few wind-related scientific researches have been conducted for such systems. In order to improve knowledge on wind load characteristics for green roof modules, a series of wind tunnel experiments were carried out on a scaled densely tapped module model installed at different positions on two types of flat roofs of medium-rise buildings. Peak force and moment coefficients of the rooftop module model were mainly investigated followed by comparison with related contents in ASCE/SEI7-10. The effect of parapets and other design parameters were also considered. The results show that the most unfavorable values for both peak lateral and uplift force coefficients occur when the module is located at the corners of the roof, and they exceed those suggested in the code. The overturning moments for the module are mainly determined by the uplift forces due to the unique geometry of green roof modules. The wind load decreases as the parapet height increases. For practical design, considerations on relating roof pressures to uplift forces, generalization of aerodynamic centers and estimation of failure wind speeds were proposed.