Engineering Commons^™

Experimental Evaluation Of Abl And Downburst Wind Loads On An Elevated Building, Kate Current

Electronic Thesis and Dissertation Repository

Elevated low-rise buildings are vulnerable to cladding damage underneath the structure due to extreme winds and the absence of proper wind loading codes and standards such as the National Building Code of Canada (NBCC). The space between the ground and the horizontal base surface of an elevated structure affects its aerodynamics differently compared to a ground-mounted structure. Despite the widespread use of elevated low-rise buildings, there is still limited understanding of the wind interaction across building surfaces for different stilt heights and wind types. This research aims to evaluate the impact of atmospheric boundary layer (ABL) and downburst wind loads …

Physical Investigation Of Downburst Winds And Applicability To Full Scale Events, Federico Canepa

Electronic Thesis and Dissertation Repository

Thunderstorm winds, i.e. downbursts, are cold descending currents originating from cumulonimbus clouds which, upon the impingement on the ground, spread radially with high intensities. The downdraft phase of the storm and the subsequent radial outflow that is formed can cause major issues for aviation and immense damages to ground-mounted structures. Thunderstorm winds present characteristics completely different from the stationary Gaussian synoptic winds, which largely affect the mid-latitude areas of the globe in the form of extra-tropical cyclones. Downbursts are very localized winds in both space and time. It follows that their statistical investigation, by means of classical full scale anemometric …

Numerical Simulation And Scaling Of Thunderstorm Downburst Outflows, Cristiano Andre Rodrigues Kondo

Electronic Thesis and Dissertation Repository

A downburst is a natural phenomenon that occurs during thunderstorms, creating hazards and damage to infrastructure due to the strong winds produced. This research contributes to the current literature by applying the Lundgren et al. scaling parameters (R₀, T₀, V₀) to scale cooling source (CS) downburst simulations. The research also investigates the effects of the environmental lapse rate (ELR) on full-scale downburst outflows and compares the full-cloud model with the subcloud model simulations. The results showed that the scaling parameters preserve the temporal and vertical radial wind speed profile shape, as well as the …

Experimental Modelling Of Downburst And Downburst Line Outflows, Kyle Graat

Electronic Thesis and Dissertation Repository

The outflow velocity vector fields of simulated stationary thunderstorm downbursts and downburst lines were resolved in two plane orientations, vertical and horizontal, using a dense fluid release system and Particle Image Velocimetry. Single event releases were scaled to show agreement with past studies based on radial velocity magnitude and location and radial and vertical front propagation. The vortex trajectory of a single event using the vortex aspect ratio supported density's role in the outflow after the time and location of the maximum radial velocity. The interaction between two release events varied temporally and spatially and showed that the interaction region's …

Transient Analysis Of Full Scale And Experimental Downburst Flows, Junayed Chowdhury

Electronic Thesis and Dissertation Repository

Downbursts are highly transient natural phenomena which produce strong downdrafts evolving from a cumulonimbus cloud They induce an outburst of damaging winds on or near to the ground causing an immense damage to the ground mounted structures and aircrafts. This study investigates the transient nature of downbursts using wind speed records from full scale downburst events employing an objective methodology. This method can detect the abrupt change points in a downburst time series based on statistical parameters such as mean, standard deviation and linear trend. In addition to the analysis of the full scale downburst events, several large scale experimental …

Assessment Of Dynamic Effect Of Transmission Line Conductor Longitudinal Reaction Due To Downburst Loading, Ibrahim Ibrahim

Electronic Thesis and Dissertation Repository

Due to the locality and non-stationary nature of downburst wind loading events, their effect on the structural response of transmission line structures is of special nature that differs from conventional atmospheric boundary layer wind loading. Acknowledging such difference, the current thesis aims to quantify the dynamic effect associated with downburst loading on transmission line systems. To achieve that, several steps had to be realized, including experimentally verifying the numerical model used for analysis using wind field that was generated using computational fluid dynamics. The verified model was extended from model scale to full scale, where the wind field used for …

Behaviour Of Pre-Stressed Concrete Transmission Poles Under High Intensity Wind, Ahmed M. Ibrahim

Electronic Thesis and Dissertation Repository

Among different types of electrical transmission line structures, pre-stressed concrete transmission poles have the advantages of low installation and maintenance costs, appropriate delivery time, and high corrosion resistivity. Typically, these poles are designed to resist synoptic wind loading. Current design codes do not consider the effect of high intensity wind (HIW) events in the form of downbursts and tornadoes on pre-stressed concrete poles despite the fact that those weather events are the main cause of failure of transmission line structures. The first comprehensive study conducted to assess the behaviour of pre-stressed concrete transmission poles under HIW is presented in this …

Development Of Design Loads For Transmission Line Structures Subjected To Downbursts Using Aero-Elastic Testing And Numerical Modeling, Amal Elawady

Electronic Thesis and Dissertation Repository

The failure of transmission line structures due to severe High Intensity Wind (HIW) events is one of the major problems facing the electrical utility companies in various places around the globe including Canada. An extensive research program focusing on this problem started about fifteen years ago at The University of Western Ontario (UWO). In this Thesis, two major milestones are achieved leading to the advancement of the knowledge in this field. The first milestone is conducting, for the first time, a test on an aero-elastic model of a multi-span transmission system under reduced–scale simulated downbursts. The first objective of the …

Numerical Investigation Of Full Scale Thunderstorm Downbursts: A Parametric Study And Comparison To Meteorological Model, Christopher Oreskovic

Electronic Thesis and Dissertation Repository

A series of Large Eddy Simulations using an atmospheric meteorological cloud model have been used to investigate the important geometric and thermal parameters that influence a thunderstorm downburst outflow, as it pertains specifically to the idealized cooling source model. A separate set of Large Eddy Simulations make use of the same idealized cooling source model, in a realistic atmospheric base state using real field sounding data, in an attempt to make a quantifiable comparison to a downburst from a full cloud simulation. Randomness has been added to the cooling source forcing function to mimic the thermal variation in a real …

Response Of Transmission Line Conductors Under Downburst Wind, Haitham Aboshosha

Electronic Thesis and Dissertation Repository

Electricity is transmitted by Transmission Lines (TLs) from the source of production to the distribution system and then to the end consumers. Failure of a TL can lead to significant economic losses and to negative social consequences resulting from the interruption of power. High Intensity Winds (HIW), in the form of downbursts and tornadoes, are believed to be responsible for more than 80% of the weather-related failure of TLs around the world. The studies reported in this thesis are part of an ongoing extensive research program at Western University focusing on the response of TLs under HIW. Previous investigations conducted …

Numerical Modelling Of Downburst Interaction With Bluff Body, Aditi Jog

Electronic Thesis and Dissertation Repository

The objective of this study is to investigate the interaction of a bluff body with a downburst flow. Numerical investigation of the flow field using CFD analysis was carried out for three different downburst sizes (h/d=1, 2, 4) under suitable boundary conditions subjected to constant jet velocity. The downburst-structure interaction study was conducted for two jet diameters (h/d=1 and 4) and two radial locations from the downburst center.

The results showed that the downburst size greatly dominates the intensity of the flow. The largest downburst resulted in the highest velocity magnitude near the ground and also covered a larger area …

Capacity Assessment Of A Transmission Tower Under Wind Loading, Thomas G. Mara

Electronic Thesis and Dissertation Repository

Transmission towers play a vital role in power distribution networks and are often subject to strong wind loads. Lattice tower design is often based on a linear elastic response to wind loading using methodology derived for atmospheric boundary layer (ABL) winds. A number of failures have been attributed to high intensity wind (HIW) events such as downbursts and tornadoes. This thesis investigates extreme winds on a self-supported lattice transmission tower and ultimately makes comparisons of the capacity under ABL and HIW. The force-deformation relation between the base shear and the displacement of the tip of the tower are used to …