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Failures of high mast illumination poles (HMIPs) in recent years have raised concerns on the long-term fatigue performance of the poles by various transportation officials around the US. The thesis documents a study sponsored by the Texas Department of Transportation focused on the fatigue behavior of in-service HMIP systems. This study is an extension of previous investigations on the fatigue behavior of the poles that have demonstrated that many poles have poor performance and fail in fatigue before the AASHTO category E' limit. Galvanized specimens were also tested and some of them showed evidence of initial cracking, impacting the fatigue performance such that the galvanized poles behaved worse than the uncoated specimens. Ultrasonic Testing (UT) has shown several poles around the state of Texas contain cracks in the welds between the shaft and base plate. To further investigate the performance of the poles in-service, a field study was initiated to measure the wind speed and direction, as well as the corresponding stresses in the pole shaft. This thesis presents results from the field investigation. A data acquisition system was developed to gather wind data and induced stresses. The system was powered by a solar panel and can be remotely accessed via a wireless modem. Data collected throughout the year details the intensity and number of stress cycles experienced by the poles, and could be correlated with the measured wind velocity. Using the field data, more accurate estimates of expected fatigue life for the poles were made. The study provides TxDOT with valuable data on the performance of in-service poles so that the most critical fatigue cases can be identified and proper decisions can be made on the appropriate inspection or repair schedule. / text

When a structure with an in-plane discontinuous frame is used, a discontinuous load path is formed due to the irregularity. This is continuous load path can lead to the failure of certain elements and the structure as a whole when the structure is exposed to lateral loading. In this study, an in-plane discontinuous frame structure is exposed to gravity as well as lateral loading due to which a discontinuous load path is formed. Due to the discontinuous load path, higher value of axial load is developed on a beam which is generally designed considering it as a flexural member. The main objective of this thesis is to determine if the beam can be designated as the critical member in the in-plane discontinuous frame and the comparison of the critical element with the corresponding element in a frame that has no structural irregularities. The objective is also to design the critical member considering it as a beam-column element considering the combined effect of bending and compression.

For many years, inflatable structures and membrane enclosed structures have proved useful for a variety of purposes, such as athletic pavilions, exhibition spaces, coliseums, and kiosks. More recently, structures that combine highly pressurized inflatable arch members with light fabric membrane coverings have been considered for use as a variation of such structural systems. The United States Army has begun to investigate pressurized arch-supported membrane shelters that would be large, lightweight, and easily erected in a short amount of time. These shelters are proposed for a variety of purposes, including aircraft hangars, vehicle maintenance shelters, and medical aid stations. The specific contribution of this study was the creation and testing of scale models to obtain a better understanding of how these structures behave under wind and snow loading conditions. Three models were constructed, one at a scale of 1:100 and two at a scale of 1:50. The 1:100 scale model represented a proposed prototypical structure 200 ft long, 75 ft wide, and 50 ft tall, with multiple arches. Of the 1:50 scale models, one model represented a structure with the same dimensions as the 1:100 scale model and the other represented a single arch from one of the proposed prototypical structures. Both of the full structural models were wind and snow load tested. The single arch model was tested under full and partial snow loading. Data from the testing were collected, tabulated, and evaluated. The experimental results are discussed, conclusions are drawn, and recommendations for further research are presented. / Master of Science

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This thesis presents the results of testing and modeling conducted to characterize the performance of 3M™ VHB™ structural glazing tape in both shear and tension. Creep rupture testing results provided the failure time at a given static load and temperature, and ramp-to-fail testing results provided the ultimate load resistance at a given rate of strain and temperature. Parallel testing was conducted on three structural silicone sealants to compare performance. Using the time temperature superposition principle, master curves of VHB tape storage and loss moduli in shear and tension were developed with data from a dynamic mechanical analyzer (DMA). The thermal shift factors obtained from these constitutive tests were successfully applied to the creep rupture and ramp-to-fail data collected at 23°C, 40°C, and 60°C (73°F, 104°F, and 140°F), resulting in master curves of ramp-to-fail strength and creep rupture durability in shear and tension. A simple linear damage accumulation model was then proposed to examine the accumulation of wind damage if VHB tape is used to attach curtain wall glazing panels to building facades. The purpose of the model was to investigate the magnitude of damage resulting from the accumulation of sustained wind speeds that are less than the peak design wind speed. The model used the equation derived from tensile creep rupture testing, extrapolated into the range of stresses that would typically be generated by wind loading. This equation was applied to each individual entry in the data files of several real wind speed histories, and the fractions of life used at each entry were combined into a total percentage of life used. Although the model did not provide evidence that the established design procedure is unsafe, it suggested that the accumulation of damage from wind speeds below the peak wind speed could cause a VHB tape mode of failure that merits examination along with the more traditional peak wind speed design procedure currently recommended by the vendor. / Master of Science

This thesis describes a series of 1:75 scale wind tunnel experiments investigating the wind flow over, and through, three different forest models and the resultant wind loading on individual model trees. The experiments were designed to lead to a quantitative assessment of the wind stability of the particular forest arrangements and also to permit a study of the coherent gust structures in the flow. Forest canopy flow is dominated by a plane mixing layer flow regime with a shear layer close to the canopy top. It has been confirmed that data can be correlated usefully in terms of a shear length, Ls, related to the form of this shear layer. Frequency analysis has confirmed that the flow structures have the same frequency as the swaying of the tallest trees in each forest. A mechanism is proposed whereby upstream turbulence induces swaying of trees at and near the upwind edge region of the forest, which in turn perturbs the air in the unstable shear layer. This leads to a roll-up of the shear layer and the creation of coherent flow structures. Conditional sampling of the gust structures, using wavelet analysis, has also supported the theory of a plane mixing layer type flow. An eddy-pair structure was revealed, the arrangement of which accounts for the intermittent strong downward sweeps of air into the canopy that have been reported by many observers. The large downward sweep of air was also shown to be responsible for the highest bending moments experienced by individual trees. Assessments of the different forest formations showed that in a forest consisting of a 50/50 mix of 200 mm and 100 mm model trees, gusts did not penetrate the lower forest. This arrangement should improve the protection of younger trees and may be worth investigating in field trials.

In order to meet EU legislation on emissions, significant effort is being invested into the development of cost-effective renewable power generation technologies. The two leading technologies are solar and wind power because of their potential for the lowest levelised cost of energy and for showing a growth in installed capacity and technological development. Various research findings have suggested that significant cost savings in the capital expenditure of renewable energy projects can be made through the optimisation of their support foundations, the understanding of which has formed the main goal of the research.

The turbulent nature of the wind flow coupled with additional turbulence created by the wind-building interaction result in highly non-uniform, fluctuating wind-loading on building envelopes. This is true even for simple rectangular symmetric buildings. Building codes and standards should reflect the information on which they are based as closely as possible, and this should be achieved without making the building codes too complicated and/or bulky. However, given the complexity of wind loading on low-rise buildings, its codification can be difficult, and it often entails significant inconsistencies. This required the development of alternative design methods, such as the Database-Assisted-Design (DAD) methodology, that can produce more accurate and risk-consistent estimates of wind loads or their effects. In this dissertation, the DAD methodology for rigid-structures has been further developed into a design tool capable of automatically helping to size member cross sections that closely meet codified strength and serviceability requirements. This was achieved by the integration of the wind engineering and structural engineering phases of designing for wind and gravity loads. Results obtained using this method showed DAD’s potential for practical use in structural design. Different methods of synthesizing aerodynamic and climatological data were investigated, and the effects of internal pressure in structural design were also studied in the context of DAD. This dissertation also addressed the issues of (i) insufficiently comprehensive aerodynamic databases for various types of building shapes, and (ii) the large volume (in size) of existing aerodynamic databases, that can significantly affect the extent to which the DAD methodology is used in engineering practice. This research is part of an initiative to renew the way we evaluate wind loads and perform designs. It is transformative insofar as it enables designs that are safe and economical owing to the risk-consistency inherent in DAD, meaning that enough structural muscle is provided to assure safe behavior, while fat is automatically eliminated in the interest of economy and CO2 footprint reduction.