Wall of Wind researchers conducted full-scale testing of trees to determine realistic wind loads on various types of trees and the planter design to securely hold them in the balconies, which is impossible to do using small-scale models.

Learn more about this project.

This video compares the performance of two windows, one covered with a shutter (on the right) and the other one without a shutter (on the left), under wind-driven rain conditions simulated at the Wall of Wind. It is clear from the video that shutters can play an important role in reducing wind-driven-rain intrusion through windows.

The current methods for evaluating the adequacy of metal roofs in withstanding wind-induced loads involve undertaking uniform uplift pressure tests. These methods may not be truly representative of real conditions, and might set higher minimum design requirements than necessary in some cases, and in others they could underestimate effects of very localized peak pressures. This research work presents results of a full-scale experimental study conducted under more realistic wind loading with the panels installed as they would be in the American Society for Testing and Materials (ASTM) E1592 test chamber. The research objectives were to (i) measure the uplift roof pressure experience by mono-sloped standing seam metal roofs and compare them with the provisions of the American Society of Civil Engineers (ASCE) 7–10 standard, (ii) evaluate the performance of standing seam roofs under high winds, and (iii) compare the deflections and failure modes observed under more realistic wind loading to uniform loading tests. The research has provided test based data on aerodynamic loading of two types of standing seam metal roofs (i.e. vertical-leg and trapezoidal), as well as their performances under high wind speeds.

Learn more about this project.

To address wind induced vibrations of PV systems, a multi-scale wind load measurement study was conducted at Florida International University (FIU) using a single PV system located on the roof of a building model. The PV panel orientation was adjusted to different tilt angles that would generally encompass common residential installations in North America. The goal of the study was to compare the net aerodynamic forces acting on an individual roof-mounted PV panel measured at full scale using the 6-fan Wall of Wind (WOW) hurricane simulator at FIU with those measured in a boundary layer wind tunnel (BLWT) of RWDI USA LLC at a scale of 1:12. A complementary full-scale and scaled model testing approach, such as the one discussed in this paper, may draw upon the strengths of each test method. Full-scale testing affords engineers with opportunities to (1) investigate possible Reynolds Number (Re) effects to assess the applicability of experimental results to the real design cases, (2) determine load transfer information on actual PV support systems, (3) study wind induced vibrations of PV systems when subjected to severe winds, and (4) evaluate possible failure modes due to high winds. Conversely, small-scale testing in the BLWT is an established and reputable method for wind load estimations accepted by most code-writing authorities, and provides a convenient platform for testing many different model configurations and wind directions in shorter amounts of time and at significantly lower costs when compared to equivalent full-scale testing. As a result of a comparison between full- and small-scale test results, the main observation was that the dynamic effects were one of the main sources of discrepancy between wind tunnel and WOW measurements. A post-test analytical approach was used to incorporate the dynamic effects to correct the measurements obtained on rigid model tested in wind tunnel to bring them in line with full scale results.

The roof is the most vulnerable part of a low rise building as it is often affected in the event of high winds that produce high suctions or uplift forces on the edges and corners. This study investigates the application of an active mitigation strategy, in the form of an Active Aerodynamics Mitigation and Power Production System (AMPS) (United States Patent Application Publication, Pub. No.: US 2015/0345472 A1, Pub. Date: Dec. 3, 2015), designed to simultaneously reduce wind damage and provide power to buildings, homes, and other infrastructures. The system consists of horizontal axis wind turbines attached to the roof edges with or without gutters. Three different configurations of this system were tested on a flat roof of a low rise building model for a range of wind directions through experiments at the Wall of Wind Experimental Facility (WOW EF) at Florida International University (FIU), USA. In one of the configurations, the wind turbines were placed slightly above the roof edge, while in the other two configurations, the turbines were placed closer to the roof edge. Estimation of area averaged mean and peak pressure coefficients were made for various locations on the roof for the three different configurations, and compared with the case of no mitigation (i.e. bare roof deck without AMPS). Results show that for all wind directions tested, significant reduction in mean and peak pressure coefficients (reduced suction) were obtained in those cases where the wind turbines were placed closer to the roof edge as compared to the bare roof deck case. Flow visualization studies showed that the turbines helped to disrupt the conical vortices caused by cornering winds, thereby reducing the wind uplift forces on the roof. This study shows that the active mitigation system can be utilised to prevent wind induced damage to the roof while generating wind energy. Future research is underway to study the effectiveness of AMPS in mitigating wind loading on other kinds of buildings and structures.

Learn more about this project.

This study presents a large-scale experimental study to investigate the wind loading on concrete roof pavers on the flat roof of a low rise building. The experiments were performed in Wall of Wind, a largescale hurricane testing facility at Florida International University. Experiments included both wind blowoff tests and pressure measurements on the top and bottom surfaces of the pavers. The effects of the pavers' edge-gap to spacer height ratio and the relative parapet height on the wind performance of roof pavers were also investigated. The results showed that increasing the edge-gap to spacer height ratio parameter decreases the net pressures by enhancing pressure equalization between top and bottom surfaces. Also, increasing the relative parapet height reduces the worst suctions for the parapet heights considered in this study. The resolution of the pressure taps was found to have significant influence on the test results. Too few taps can result in underestimation of the net uplift and overturning moments that can cause failure under strong winds. Guidelines on the resolution and location of pressure taps were provided for better capturing the effects of conical vortices on wind loads on pavers. Results of the wind blow-off tests are compared with those obtained from pressure measurements and a typical practice based on ASCE 7-10 exterior pressures.

Learn more about this project.

This work investigates the effects of Reynolds number (Re) on the aerodynamic characteristics of a twin-deck bridge. A 1:36 scale sectional model of a twin girder bridge was tested using the Wall of Wind (WOW) open jet wind tunnel facility at Florida International University (FIU). Static tests were performed on the model, instrumented with pressure taps and load cells, at high wind speeds with Re ranging from 1.3 × 106 to 6.1 × 106 based on the section width. Results show that the section was almost insensitive to Re when pitched to negative angles of attack. However, mean and fluctuating pressure distributions changed noticeably for zero and positive wind angles of attack while testing at different Re regimes. The pressure results suggested that with the Re increase, a larger separation bubble formed on the bottom surface of the upstream girder accompanied with a narrower wake region. As a result, drag coefficient decreased mildly and negative lift coefficient increased. Flow modification due to the Re increase also helped in distributing forces more equally between the two girders. The bare deck section was found to be prone to vortex shedding with limited dependence on the Re. Based on the observations, vortex mitigation devices attached to the bottom surface were effective in inhibiting vortex shedding, particularly at lower Re regime.

Learn more about this project.