Peter Irwin

Large-Scale Experimentation Using the 12-Fan Wall of Wind to Assess and Mitigate Hurricane Wind and Rain Impacts on Buildings and Infrastructure Systems

AbstractEngineering research is undergoing dramatic changes with novel, large-scale research facilities being developed to help reduce the growing economic losses associated with natural disasters....

Experimental Assessment of Wind Loads on Vinyl Wall Siding

Wind-induced damage to multi-layer building wall systems, such as systems with vinyl siding, is common, especially in hurricane-prone areas. Wind load distribution through these multi layered walls and the amount of load reduction due to pressure equalization is expressed through Pressure Equalization Factors (PEF). The ASTM D3679 standard suggests a PEF of 0.36, which means a 64% reduction in the net pressure on the siding. This paper presents results from an experimental study conducted on a low-rise building subjected to realistic wind loading conditions at the Wall of Wind (WOW) experimental facility at Florida International University (FIU). Results from area averaged mean and peak pressure coefficients indicated that a very small portion of the total wind load is carried by the vinyl siding. However, PEF’s were found to be much higher when individual taps were considered. For instance, PEFs ranged from 71% to 106% for the case of pressure coefficients with negative sign (suction) and 39% to 110% for the case of pressure coefficients with positive sign (pressure). When a combined set of taps was considered, PEFs ranged approximately from 50% to 80% for the case of ‘suction’ and 15% to 75% for ‘pressure’. Based on the 1 m2 of tributary area used in ASCE 7-10 Standard, results show that the net load on vinyl wall siding can be obtained by reducing the net design load for the entire wall assembly by 25% and 60% for suctions and pressures, respectively. However, a smaller tributary area (< 1 m2) can experience a local peak load that can induce damage to connections, especially in the case of relatively flexible wall coverings, with no or very little load sharing between connection points. Results indicate that for smaller areas (~ 0.2 m2) the allowable percentage reductions should not be more than 15% and 25% for suctions and pressures, respectively. This study shows that the suggested ASTM PEF of 0.36 may lead to the underestimation of loads for the design of details affected by local loads. However, further research is needed to consider more cases when developing adequate design load guidelines for vinyl wall sidings.

Design Guidelines for Roof Pavers against Wind Uplift

The objective of this paper is to develop guidance for design of loose laid roof pavers against wind uplift. Large-scale experiments were performed on concrete roof pavers installed on the flat roof of a low-rise building using the Wall of Wind (WOW) facility at Florida International University (FIU). Both wind blow-off tests and pressure measurements on the top and bottom surfaces of the pavers were performed. The results are used to develop specific guidelines for design of loose-laid roof pavers. Account is taken of pressure equalization, the gaps between the pavers, and the space beneath the pavers. These guidelines are intended to be simple enough to be used by designers in parallel with the usual code provisions for exterior suctions

An Experimental Study on the Wind-Induced Response of Variable Message Signs

Variable Message Sign (VMS) systems are widely used in motorways to provide traffic information to motorists. Such systems are subjected to wind-induced structural vibration that can lead to damage due to fatigue. The limited information that is available on the safe wind design of VMS motivated a large scale testing that was conducted at the Wall of Wind (WOW) Experimental Facility at Florida International University (FIU). One of the objectives of the present study was to experimentally assess the wind-induced force coefficients on VMS of different geometries and utilize these results to provide improved design guidelines. A comprehensive range of VMS geometries were tested and mean normal and lateral force coefficients, in addition to the twisting moment coefficient and eccentricity ratio, were determined using the measured data for each model, for wind directions of 0o and 45o. The results confirmed that the mean drag coefficient on a prismatic VMS is smaller than the value of 1.7 suggested by American Association of State Highway and Transportation Officials (AASHTO). An alternative to this value is presented in the form of a design matrix with coefficients ranging from 0.98 to 1.28, depending on the aspect and depth ratio of the VMS. Furthermore, results indicated that the corner modification on a VMS with chamfered edges demonstrated a reduction in the drag coefficient compared to sharper edges. Finally, the dynamic loading effects were considered by evaluating the gust effect factor, using the ASCE 7 formulations, for various VMS weights and geometries. The findings revealed a wide range of possible gust effect factors, both above and below the current AASHTO specification of 1.14. Future research may include different geometries of VMS and a wider range of wind directions.