Browsing by Subject "Buildings -- Aerodynamics"
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Item A model for time varying wind loads on a low-rise structure(Texas Tech University, 2001-05) Fagan, Rebecca BimmermanOverall loads acting on a full scale building in the natural vdnd environment are characterized in this work. The first objective of this research is to directly measure the overall wind loads on the test building at the Wind Engineering Research Field Laboratory (WERFL) in the natural wind environment. The measurements are accomplished using four load cells, with one load cell placed at each comer of the building. These four load cells support the entire weight of the building, and each cell measures two shear forces and one vertical force acting at its comer of the building. These twelve forces were combined to measure total uplift, total horizontal shear, along, and across wind response. Mean drag coefficients are calculated from these measurements in the natural wind environment and are compared to wind tunnel. Uncertainty in the measurements was expected, as several aspects of full-scale testing are difficult to control. Thermal reactions of the WERFL undercarriage were time varying and the variable weight distribution occurred upon lowering the undercarriage onto four point supports. The second objective of this research is to develop a mathematical model using system identification to relate the three orthogonal fluctuating components of wind induced forces to the along, cross and vertical components of wind speed. An ARX (5,5) was found to be appropriate to capture the relationship between the free-stream wind turbulence and the turbulent wake characteristics. This model may then be used to generate modeled data or describe spectral relationships. Investigation in the frequency domain indicates that the building acts as a low-pass filter with the half-power frequency of 0.08 Hz.Item Analysis of wind characteristics from field wind data(Texas Tech University, 1987-05) Kancharla, Vidyasagar ReddyNot availableItem Application of the boundary element method for tornado forces on buildings(Texas Tech University, 1985-08) Selvam, Rathinam PanneerNot availableItem Comparison of wind tunnel pressure measurements on the Texas Tech building(Texas Tech University, 2004-05) Chowdary, Niaz AA recent trend has been observed concerning the mean extreme local pressure coefficients measured in wind tunnels and in full-scale experiments for flow around low buildings. It was observed that the magnitudes of the mean extreme pressure coefficients measured in wind tunnel studies have been increasing as the data acquisition methods and boundary simulation techniques have improved. Wind tunnel'test data on generic low building is being generated at the Boundary Layer Wind Tunnel Laboratory at the Texas Tech University to contribute to a large database that will be made available to designers. In the most recent of these experiments, two scaled models 1:100 and 1:50 of the Texas Tech University test building were investigated at two simulations in open terrain condition. Pressure data collected at several taps is analyzed for a large number of records roughly covering all angles of attack. The primary purpose of this thesis is to develop two simulations of the 10th and 90' percentile velocity and turbulence characteristics observed at WERFL and to compare point pressure coefficients between the three models, two simulations, and two other wind tunnel data sets (UWO & CSU). In addition, the study was extended to include comparisons of results obtained using the same model but tested in different wind tunnels (UWO & CSU). Tests were conducted for different wind simulations, and the data were used to develop a better understanding of the effect of flow simulation and model scale on wind load estimates for low-rise buildings. These were conducted in a boundary layer wind tunnel using simulations developed as part of a research program aimed at improving boundary layer simulations. The purpose of the improved simulations was to reduce the differences between wind tunnel data obtained at three different universities, two different scaled models and two different simulations, obtained from physical model studies in boundary layer wind tunnels. The comparison of the pressures measured on the 1:100 scale model at the Texas Tech University to those measured at two other institutions revealed that there are some differences. These differences appear to be due primarily to differences in the reference static and dynamic pressures used at the various institutions as indicated by the fact that the shape of the distribution of the pressures over the exterior of the building is maintained between the results from the various studies. Additional differences can be associated with differences in the local turbulence intensities present in the various simulations. Results indicate that without careful adjustments, the scale effects, and wind simulation variations can result in widely varying pressure coefficient predictions for the same structure. These discrepancies were attributed to the approach flow characteristics, Reynolds number effects, frequency response of the pressure measurement system, and sampling frequency of acquired data. The model and full-scale flow parameters and pressure coefficients are presented for low-turbulence nominal flow. The comparison of the model exhibits a better agreement for most of the pressure taps, including the critical corner region, than other reported wind tunnel results.Item Concrete block masonry construction to resist severe winds(Texas Tech University, 2001-08) Al-Menyawi, Yahya MohammedUnreinforced masonry is a common construction system for low-rise commercial buildings. It is often used as load-bearing wall system in large low-rise buildings such as malls, warehouse and industrial buildings. Failure of such construction type is prevalent during severe windstorm events such as tornadoes, hurricanes and severe thunderstorms. Resistance of masonry construction to wind depends on the out-of-plane strength of the exterior walls. Out-of-plane strength of unreinforced masonry walls depends mainly on the wall modulus of rupture (MOR). The statistical analysis of previously published investigations gives a mean value of the MOR of 55.5 psi with a COV of 26%. Wind-induced load is probability-based and involves variables of wind speed, terrain exposure, building enclosure type, and pressure direction. The Monte Carlo Simulation using 1,000 observations of the MOR and the wind-induced loads is used to determine the probability of failure of walls. For a wall of 10-in. thickness and 15-ft height of a partially enclosed building located in terrain exposure C in Lubbock, Texas, the probability of failure is 94% in 50-year life of the building. A target probability of failure of 1.5% in a 50-year life is ascertained from the current practice of masonry wall design. Failure strength of intermittently reinforced walls is determined using yield-line theory analysis. A mathematical methodology to relate the target probability of failure to the intermittent reinforcement spacing is introduced. It is found that a wall with intermittent reinforcement placed at a spacing equal to the wall height would survive in areas with design wind speeds up to 120 mph.Item Evaluation of the Potential Performance of Hospital Buildings in Windstorms(Texas Tech University, 1978-08) Lea, Patrick AlanNot Available.Item Inelastic response of multistory buildings to tornadoes(Texas Tech University, 1977-12) Seniwongse, Muang-sa-ngopNot availableItem Integration of knowledge-based expert system and relational database to grade buildings for wind resistance: design and implementation(Texas Tech University, 1995-12) Godbole, Seemantini PThis research was aimed at designing and implementing a system which would be capable of providing decision support, information management and easy to use user interface. Among many other challenges, one of the main challenge was to combine these different branches of computer science into one unified system. Some of the significant design features of this system include a loosely coupled design, run time binding of various components, relational database design and object-oriented user interface. It is also worth mentioning that this complex system with different components constantly communicating with one another, presents a unified fi^ont to the user. The user interface of this system was built with Microsoft Visual Basic, the database was implemented in Microsoft Access and the decision support component was built around the M4 expert system shell. The loosely coupled design facilitated a parallel design and implementation of each of the components. A user survey was conducted as a part of this thesis. The aim of the user survey was to gather information and feedback from the users about the system. This system is at work at the Insurance Industry for property Loss Reduction at Boston, MA.Item Pressure measuring system for wind-induced pressure on building surfaces(Texas Tech University, 1988-08) Ng, Howard Ho-takNot availableItem Safety analysis of steel building frames under dynamic wind loading(Texas Tech University, 1988-05) Das, Nirmal KAbsolute safety of a structure cannot be achieved because of uncertainties in loading and resistance. Conventional safety factors only qualitatively account for these uncertainties. Thus, the actual risk of failure of a structure designed in accordance with building code provisions remains unknown. Conversely, the probability of attaining a suitably specified limit state is recognized as a quantitative measure of safety. Since such information is needed in determining acceptable risk levels and in decision-making for structural improvements, a method for the evaluation of risk of failure is needed. Traditionally, wind-excited structures have been designed based on equivalent static forces in place of actual dynamic loads. For flexible buildings this may not always provide a reasonable approximation in the response analysis. The objective of this study is to evaluate the lifetime risk of failure of steel building frames subjected to dynamic wind loading. Risk is evaluated in terms of probability of excessive interfloor deflection. The method consists of the following studies: (1) estimation of the probabilities of exceedance of significant wind speeds at a specified site (wind hazard), (2) evaluation of the structural response statistics for a given storm intensity, using multiple time-histories of wind speed; and (3) convolution of the wind hazard with the response exceedance probabilities for each loading intensity considered. The wind field model used is based on the Power Law profile and Davenport's gust spectrum. Wind speeds are generated by a simulation technique. Three steel buildings ranging from three to twenty stories are investigated using shear beam model. An ideal elasto-plastic force-deformation relationship is assumed, neglecting strain-hardening effects. A step-by-step integration method is employed for solving the governing differential equations. This study is restricted to low-rise/moderately tall (up to 20 stories) rectangular steel buildings having equally spaced, laterally unbraced frames. Only along-wind responses are considered, neglecting wind directional effects.Item The effects of stationarity on the pressure coefficients measured on a low-rise building(Texas Tech University, 2002-08) Whitworth, Mona RichardThe primary objective of this investigation is to establish whether or not nonstationarity has a significant effect on the pressures (and the resulting pressure coefficients) measured on the full-scale building at WERFL. Four flow regimes (stagnation, wake, separated and conical vortex) using three pressure taps located on the wall, the roof edge, and the roof comer were chosen for this investigation. Summary statistics from 15-minute duration runs collected in collection Modes 15, 28, 38, 48, 49, 50, 51, and 52 over a period of 10 years are used in this study. Four categories of stationarity were used for the analysis. Stationary Speed & Stationary Direction (SS), Nonstationary Speed and Stationary Direction (NS), Stationary Speed & Nonstationary Direction (SN), Nonstationary Speed and Nonstationary Direction (NN). The Kruskal-Wallis test on the Cp mean, rms, min and max pressure coefficients using the 4 stationarity categories were initially performed to establish a statistical significant difference in the Cp's associated with each of the stationarity categories. The Kruskal-Wallis test does not remove the effects of flow characteristics on the measured pressure coefficients. To remove the confounding effects of the flow turbulence parameters, the non parametric Friedman Test was used. Roughness length, zo, longitudinal turbulence Intensity lu, lateral turbulence Intensity L, and mean wind speed are used as blocking factors in the Friedman test. In general, stationarity of speed and direction was not significant when the effects of the flow characteristics are considered.Item Wall barrier resistance to the impact of tornado-generated missiles(Texas Tech University, 1984-05) Bailey, James RobertNot availableItem Wind effects on a full-scale frame(Texas Tech University, 2002-12) Jain, ShikhaThe design of structural members entails computation of members' stresses generated due to various loads such as dead load, live load, wind load, earthquake load etc. This study restricts itself to the determination of load effects arising out of wind load. The subject of this research is the building located in the WERFL field site, Texas Tech University, Lubbock. The building is comprised of three portal frames. The focus is on determining load effects at three locations for the middle frame of the building Influence coefficients are obtained for various tap locations on the building. The pressure coefficients obtained from model scale testing of WERFL at UWO boundary layer wind tunnel are combined with the influence coefficients to obtain the desired load effects. This has been enabled through MATLAB programs developed for this research. The marginal relative frequency distribution for these load effects is compared to Gaussian and Gamma distributions to understand the applicability of these distributions in generalizing the wind tunnel results. Load effects are computed for this building using ASCE 7 recommended pressure coefficients. These values have been compared with wind tunnel load effects. The magnitude of load effect obtained using ASCE 7-98 pressure coefficient values is higher than the mean value obtained using wind tunnel data for all load effects except for uplift in leeward column and is observed to lie in the tail region of the marginal distribution of load effect generated using wind tunnel data.Item Wind effects on metal edge flashings(Texas Tech University, 1995-12) Jiang, HuiThis thesis presents the full-scale measurements of wind pressures on four different metal edge flashing profiles installed on the Texas Tech University Wind Engineering Research Field Laboratory (WERFL) test building at different wind angles of attack (windward, leeward, quartering and parallel direction). The distributions of wind pressure coefficients (Cp) on each flashing are plotted and discussed. Using the measured wind pressure coefficients (Cp) and influence coefficients (IC) obtained from a Finite Element Analysis, the combined wind effect coefficients (GC) for each flashing were developed. A general equation similar to that in ASCE 7-93 is introduced to determine the wind effects (fastener pullout force, deflection and maximum stress) on metal edge flashings. From the study, it is clear that pressure distributions on metal edge flashings strongly depend on size and profile shape of the flashings, location on the building and angle of attack of the wind. The largest mean pressure coefficients occur when the wind is blowing normal to the wall. However, near a roof comer, the most critical wind direction is a quartering wind. Substantially large mean pressures occur on both the horizontal and vertical flanges of the flashings near sharp comers. These pressures are not predicted by current codes and standards.Item Wind parameters of Texas Tech University field site(Texas Tech University, 1988-08) Chok, Chee VuiWind parameters obtained from field data are generally simulated in wind tunnel for studying wind effects on structures. The result of the wind tunnel study depends on the reliability of field wind parameters and the simulation technique. The objective of this study is to assess wind parameters from field data. The National Science Foundation has sponsored a project at the Texas Tech University Wind Engineering Research Field Laboratory to study wind effects on low-rise building. Wind pressure and meteorological data are collected on the test building and meteorological tower respectively. Meteorological data which include wind speed, wind direction, temperature, barometric pressure and relative humidity data, are measured at four levels of the tower. Wind speed, wind direction and temperature data are used for assessment of wind parameters and characterization of terrain. A total of 63, 15-minute duration each, records are collected. Of these, 31 records are found to be suitable for analysis. These 31 records are analyzed to determine wind profile parameters for both power and logarithmic laws, turbulence intensity and longitudinal integral scale of turbulence. The wind profile parameters, mean wind directions and terrain features are used to characterize the field site terrain. Results of the analysis are presented in this report.Item Wind pressure fields around non-rectangular buildings(Texas Tech University, 2003-05) Morse, Stephen M.Not availableItem Wind tunnel simulation of the Texas Tech Field Research Laboratory: effects of terrain features and building orientation(Texas Tech University, 1998-08) Lakas, Basilio DNot available