An aerodynamic investigation of cylindrical and Y-shaped building structures was carried out. Specific emphasis was directed towards determining the pressure distribution over three configurations: a flat top, a single dome and a dome with a counter-dome. The Y-model was tested in all three configurations while the cylindrical model was tested in dome/counter-dome configuration only. Both models were tested at Reynolds number(Re) of 360000 and 720000. Surface flow visualization was carried out to reveal regions of separation, recirculation and reattachment. It was found that a large region of negative pressure can be achieved with the dome counter-dome configuration. The maximum negative Cp for this configuration was about 50% higher than the maximum value observed with the flat top or single dome configuration. When the gap between the dome was decreased the maximum negative Cp increased; the increment being greater at the lower Re. Also, for the same Re and gap, the dome with higher curvature showed higher maximum negative Cp; the difference being more pronounced at the lower Re. The effect on the pressure distribution of an opening in the center of the lower dome and of an air flow through that opening was also investigated. It was observed that for injection rates corresponding to typical design flow rates required for ventilation of tall full scale buildings, the pressure distribution remains essentially unaltered. / Master of Science

A dynamic pressure measuring system composed of long connecting tube, transducer, D-C amplifier and galvanometer oscillograph were used in a wind study conducted by the Department of Agricultural Engineering, Virginia Polytechnic Institute. The instrumentation was used to measure and record dynamic pressures due to wind velocity. Data recorded in that study indicated velocity head pressure oscillations on some surfaces of the test structure in excess of 100 Hz. This investigation was undertaken to see if the recorded oscillations could have been generated in the measuring system or if they were truly windpressure variations. Components of the pressure measuring system were modeled by transfer functions. From these transfer functions, a system operational transfer function was determined and used to define system frequency response. The frequency analysis indicated the system was severely limited in response by the oscillating air column constrained within the interconnecting tube. The usable frequency range of the system (+ 10% tolerable amplitude error allowable) was found to go from zero to 34.2 Hz. By eliminating the air column this frequency range could have been extended to 99.4 Hz. Phase shifts in these frequency ranges were found to be negligible. Transducers were mounted rigidly to exterior walls of the test structure. The measured fundamental natural frequencies of these walls (transducer mountings) were found to be well within the usable frequency range of the instrumentation; and, therefore, a source of vibration pickup. To improve the measuring system reliability, recommendations were made to eliminate the air column and stiffen the transducer mountings. / Master of Science

Cylindrical shells are widely used in civil engineering. Examples include cooling towers, pipelines, nuclear containment vessels, steel silos and tanks for storage of bulk solids and liquids, and pressure vessels. The loading condition for these shells is quite varied depending on the function of the shell. Axial compression, global bending, external or internal pressure and wind loading are some of the most common loading forms for realistic structures. The failure of these cylindrical shell structures is often controlled by elastic or elastic-plastic buckling failure. Yield failure may occur in thick cylinders in some situations. A cylindrical shell under different loading conditions may display quite different buckling behaviour. The objective of this thesis is to investigate the characteristics of different buckling behaviours of cylindrical shell structures under axial compression, global bending, uniform external pressure and wind pressure. Some challenging practical problems in the design of these shell structures are explored. This thesis is expected to have some far-reaching impacts in defining how to design cylindrical shell structures to give them adequate strength to resist extreme events. Many aspects will be based on the latest Eurocode (EN 1993-1-6, 2007) and Recommendations (ECCS EDR5, 2008). The results show both some strength and some weaknesses in the Eurocode in design of shell structures. New methods are proposed for some practical problems. Some new conclusions and suggestions are derived and are expected to provide some useful knowledge for the improvement of the Eurocode in cylindrical shell design in general.

In this research, a wind feedforward (FF) controller has been developed to augment closed loop feedback controllers for the position and heading station keeping control of Unmanned Surface Vehicles (USVs). The performance of the controllers was experimentally tested using a 16 foot USV in an outdoor marine environment. The FF controller was combined with three nonlinear feedback controllers, a Proportional–Derivative (PD) controller, a Backstepping (BS) controller, and a Sliding mode (SM) controller, to improve the station-keeping performance of the USV. To address the problem of wind model uncertainties, adaptive wind feedforward (AFF) control schemes are also applied to the FF controller, and implemented together with the BS and SM feedback controllers. The adaptive law is derived using Lyapunov Theory to ensure stability. On-water station keeping tests of each combination of FF and feedback controllers were conducted in the U.S. Intracoastal Waterway in Dania Beach, FL USA. Five runs of each test condition were performed; each run lasted at least 10 minutes. The experiments were conducted in Sea State 1 with an average wind speed of between 1 to 4 meters per second and significant wave heights of less than 0.2 meters. When the performance of the controllers is compared using the Integral of the Absolute Error (IAE) of position criterion, the experimental results indicate that the BS and SM feedback controllers significantly outperform the PD feedback controller (e.g. a 33% and a 44% decreases in the IAE, respectively). It is also found that FF is beneficial for all three feedback controllers and that AFF can further improve the station keeping performance. For example, a BS feedback control combined with AFF control reduces the IAE by 25% when compared with a BS feedback controller combined with a non-adaptive FF controller. Among the eight combinations of controllers tested, SM feedback control combined with AFF control gives the best station keeping performance with an average position and heading error of 0.32 meters and 4.76 degrees, respectively. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Thesis (M.S.)--Mississippi State University. Department of Civil Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--Naval Postgraduate School, 1993. / Includes bibliographical references (p. 95-98).

D. Phil. / Conventional internal wind tunnel balances are designed and constructed to accommodate foil strain gauges which measure the deformation (strain) of the material. Foil strain gauge balances are known to be affected by electromagnetic interference and temperature. These balances are expensive and their manufacture is time consuming. With an increasing demand for higher accuracy, stiffness, increased resolution and temperature compensation, current balance designs are becoming inadequate. To overcome identified balance deficiencies a research programme in the application of optical Bragg gratings to wind tunnel balances was initiated. In this programme a new concept of using optical fibre Bragg grating sensors, with the advantage of using mechanical amplification to increase sensitivity, and the implementation of temperature compensation techniques was demonstrated on a simulated two component balance.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Robert Erik Grip. / M.S.

Thesis (PhD (Civil Engineering))--Stellenbosch University, 1986. / ENGLISH ABSTRACT: This dissertation presents the development process of a wind damage and disaster management support model for South Africa. Several aspects of wind damage are analysed. The impact of wind disasters on human habitat is highlighted by providing selected data of loss due to such events. This is followed by a comprehensive review of relevant research, carried out locally and internationally. The role and relevance of wind loading codification is discussed. The factors influencing wind damage are identified and their applicability to South African conditions is evaluated. An outline of a database of wind damage in South Africa which has been developed during the course of the project is presented. Selected statistics derived from this database are presented. A probabilistic model for assessing wind damage in South Africa is proposed. The model is based on the spatial principle of occurrence of strong wind events. A 'first approximation' division of the country into zones where various types of wind events occur and the characteristics of their generic footprints (i.e. distribution of wind speeds) are developed. The risk model procedure also takes the distribution of wealth, and the vulnerability of the built environment into account. / AFRIKAANSE OPSOMMING: Hierdie verhandeling bied die ontwikkelingsproses vir 'n hulpmodel vir windskade en rampbestuur vir Suid-Afrika aan. Verskeie aspekte van windskade word ontleed. Die invloed van windskade op woongebiede word beklemtoon deur die aanbieding van geselekteerde data oor relevante plaaslike en internasionale navorsing. Die rol en toepaslikheid van windbelasting in ontwerpkodes word bespreek. Die faktore wat windskade beinvloed, word geidentifiseer en die aanwendbaarheid onder Suid-Afrikaanse omstandighede word beoordeel. 'n Beskrywing van n databasis vir windskade in Suid'-Afrika, wat tydens die projek saamgestel is, word aangebied. Sekere statistiek wat uit die databasis afgelei is, word voorgelê. n Statistiese model vir die beraming van windskade in Suid-Afrika word voorgestel. Die model is gebaseer op die ruimtelike beginsel van voorkoms van sterk-wind-gebeurlikhede. 'n "Eerste benadering" - indeling van die land in streke waar verskillende soorte windgebeurlikhede voorkom en hulle karakteristieke kenmerke (bv. verspreiding van windspoed) is ontwikkel. Die werkwyse vir die risikomodel neem die verdeling van rykdom en die kwesbaarheid van die beboude omgewing in ag.