Solar energy harvesting using photovoltaic (PV) systems has gained popularity in recent years due to its relative ease of use and its cost efficiency compared to the rest of the clean energy sources. However, to further expand the application of PV systems requires making them more desirable than the other competitive energy sources. The improvement of safety and cost efficiency are requisites for further popularization of PV system application. To satisfy these requisites it is necessary to optimally design the system against the environmental conditions. Wind action is one of the main ambient loads affecting the performance of PV systems. This dissertation aims to investigate the effects of wind load on residential scale roof mounted PV panels and their supporting structures as well as evaluating the structural response of the system to the wind-induced vibration. To achieve these goals, several full- and large-scale experimental tests were performed at the Wall of Wind Experimental Facility at Florida International University (FIU). The wind effects on different PV system and roof configurations were investigated in these tests. The results shed light on the most influential parameters affecting the wind pressures acting on the PV panel surface. In addition, the findings are presented in the form of design pressure coefficients for adoption to future building codes and wind standards. The second phase of the physical testing included the investigation of the actual response of the PV system to the wind action. Because of the dynamic properties of the PV panel, it was expected that the wind induced vibration can affect the dynamic response of the system including the acceleration at the panel surface and support reactions at the racking system to roof interface. To test this theory, two different models of the system were developed, one with the real PV panels and the other one with wooden rigid panels. Comparing the results, it was concluded that the dynamic response of the system was not considerably affected by wind-induced fluctuations. Finally, and to better understand the dynamic response of the system, an analytical model was developed using ANSYS and dynamic analysis was carried out using as input the wind induced pressure data acquired from the physical testing. At the first step, the analytical model was verified by comparing the analytical modal frequencies to the experimental natural frequencies obtained from the hammer test. It was shown that the analytical model can well represent the dynamic properties of the actual model. However, once the reaction output was compared to the loadcell data recorded during the wind tunnel test, there was a considerable discrepancy between the results. It was assumed that the deflection of the supporting structure caused this discrepancy. This assumption was verified and it was concluded that the supporting structure can significantly influence the dynamic response of the system.

Ventilation might seem like a minor consideration, but when properly installed, it can extend the life of the attic and roof structure of residential buildings saving huge dollar amounts in repair costs. The objectives of this study were to measure the wind effect on different kind of vents as the problem is vents are subjected to high wind loads during hurricane events and often fail causing water penetration and damage of interior contents. Wind-induced failure of rooftop vents during a hurricane may result in large openings in the roof that will allow water to penetrate into the building, a puncturing of the roof membrane, again allowing water infiltration, and detached rooftop vents can pose considerable threats as windborne debris. The study found that water infiltration through a vent system is dependent upon the differential pressure as well as the vent mechanism. For vents experiencing higher differential pressures, vent covers can be used during storms to reduce water infiltration. Active controls can also be designed to close the vents automatically as differential pressure increases based on the wind speed and wind angle of attack.

Low-rise buildings are often subjected to high wind loads during hurricanes that lead to severe damage and cause water intrusion. It is therefore important to estimate accurate wind pressures for design purposes to reduce losses. Wind loads on low-rise buildings can differ significantly depending upon the laboratory in which they were measured. The differences are due in large part to inadequate simulations of the low-frequency content of atmospheric velocity fluctuations in the laboratory and to the small scale of the models used for the measurements. A new partial turbulence simulation methodology was developed for simulating the effect of low-frequency flow fluctuations on low-rise buildings more effectively from the point of view of testing accuracy and repeatability than is currently the case. The methodology was validated by comparing aerodynamic pressure data for building models obtained in the open-jet 12-Fan Wall of Wind (WOW) facility against their counterparts in a boundary-layer wind tunnel. Field measurements of pressures on Texas Tech University building and Silsoe building were also used for validation purposes. The tests in partial simulation are freed of integral length scale constraints, meaning that model length scales in such testing are only limited by blockage considerations. Thus the partial simulation methodology can be used to produce aerodynamic data for low-rise buildings by using large-scale models in wind tunnels and WOW-like facilities. This is a major advantage, because large-scale models allow for accurate modeling of architectural details, testing at higher Reynolds number, using greater spatial resolution of the pressure taps in high pressure zones, and assessing the performance of aerodynamic devices to reduce wind effects. The technique eliminates a major cause of discrepancies among measurements conducted in different laboratories and can help to standardize flow simulations for testing residential homes as well as significantly improving testing accuracy and repeatability. Partial turbulence simulation was used in the WOW to determine the performance of discontinuous perforated parapets in mitigating roof pressures. The comparisons of pressures with and without parapets showed significant reductions in pressure coefficients in the zones with high suctions. This demonstrated the potential of such aerodynamic add-on devices to reduce uplift forces.

Hurricane is one of the most destructive and costly natural hazard to the built environment and its impact on low-rise buildings, particularity, is beyond acceptable. The major objective of this research was to perform a parametric evaluation of internal pressure (IP) for wind-resistant design of low-rise buildings and wind-driven natural ventilation applications. For this purpose, a multi-scale experimental, i.e. full-scale at Wall of Wind (WoW) and small-scale at Boundary Layer Wind Tunnel (BLWT), and a Computational Fluid Dynamics (CFD) approach was adopted. This provided new capability to assess wind pressures realistically on internal volumes ranging from small spaces formed between roof tiles and its deck to attic to room partitions. Effects of sudden breaching, existing dominant openings on building envelopes as well as compartmentalization of building interior on the IP were systematically investigated. Results of this research indicated: (i) for sudden breaching of dominant openings, the transient overshooting response was lower than the subsequent steady state peak IP and internal volume correction for low-wind-speed testing facilities was necessary. For example a building without volume correction experienced a response four times faster and exhibited 30-40% lower mean and peak IP; (ii) for existing openings, vent openings uniformly distributed along the roof alleviated, whereas one sided openings aggravated the IP; (iii) larger dominant openings exhibited a higher IP on the building envelope, and an off-center opening on the wall exhibited (30-40%) higher IP than center located openings; (iv) compartmentalization amplified the intensity of IP and; (v) significant underneath pressure was measured for field tiles, warranting its consideration during net pressure evaluations. The study aimed at wind driven natural ventilation indicated: (i) the IP due to cross ventilation was 1.5 to 2.5 times higher for Ainlet/Aoutlet>1 compared to cases where Ainlet/AoutletCFD based IP responses. Comparisons with ASCE 7-10 consistently demonstrated that the code underestimated peak positive and suction IP.

Major portion of hurricane-induced economic loss originates from damages to building structures. The damages on building structures are typically grouped into three main categories: exterior, interior, and contents damage. Although the latter two types of damages, in most cases, cause more than 50% of the total loss, little has been done to investigate the physical damage process and unveil the interdependence of interior damage parameters. Building interior and contents damages are mainly due to wind-driven rain (WDR) intrusion through building envelope defects, breaches, and other functional openings. The limitation of research works and subsequent knowledge gaps, are in most part due to the complexity of damage phenomena during hurricanes and lack of established measurement methodologies to quantify rainwater intrusion. This dissertation focuses on devising methodologies for large-scale experimental simulation of tropical cyclone WDR and measurements of rainwater intrusion to acquire benchmark test-based data for the development of hurricane-induced building interior and contents damage model. Target WDR parameters derived from tropical cyclone rainfall data were used to simulate the WDR characteristics at the Wall of Wind (WOW) facility. The proposed WDR simulation methodology presents detailed procedures for selection of type and number of nozzles formulated based on tropical cyclone WDR study. The simulated WDR was later used to experimentally investigate the mechanisms of rainwater deposition/intrusion in buildings. Test-based dataset of two rainwater intrusion parameters that quantify the distribution of direct impinging raindrops and surface runoff rainwater over building surface — rain admittance factor (RAF) and surface runoff coefficient (SRC), respectively — were developed using common shapes of low-rise buildings. The dataset was applied to a newly formulated WDR estimation model to predict the volume of rainwater ingress through envelope openings such as wall and roof deck breaches and window sill cracks. The validation of the new model using experimental data indicated reasonable estimation of rainwater ingress through envelope defects and breaches during tropical cyclones. The WDR estimation model and experimental dataset of WDR parameters developed in this dissertation work can be used to enhance the prediction capabilities of existing interior damage models such as the Florida Public Hurricane Loss Model (FPHLM).