R.V. Milford

A review of worldwide occurrence of tornadoes

Abstract The objective of the present study was to re-visit and up-date data on tornado occurrences throughout the world. This was carried out by accessing the relevant literature, analysing, re-analysing and comparing the data on tornado occurrence from various sources. The investigation was aimed at those countries/regions for which no or little information is available. In addition to the literature survey, nearly 30 Weather Monitoring Authorities in various countries throughout the world were contacted. For some countries/regions a more detailed description of tornado occurrences than that found in the literature, was obtained. Several discrepancies between various sources of information were also identified. In addition to South Africa, contour maps of the mean rate of occurrence for France, Austria and Australia were developed.

Tornado risk model for transmission line design

A tornado risk model is developed for transmission line design. This model is based on an extension to the McDonald, (NUREG/CR-3058,1983) model for point structures, and has been developed such that it can be simplified for applications in codes of practice and design recommendations. Tornado statistics obtained for South Africa are presented to illustrate the application of the model.

Jan Smuts experiment: Comparison of full-scale and wind-tunnel results

Abstract A comparison between full-scale and wind-tunnel results obtained at the Division of Building Technology for the Jan Smuts full-scale experiment is presented. The comparison refers to the roof pressure transducers only. The comparison between the mean and root-mean-square pressure coefficients is in general satisfactory, although for certain data-sets a noticeable shift between the full-scale and wind-tunnel mean pressure coefficients was observed. In these cases the trend in the full-scale mean pressure coefficients is, however, satisfactorily reproduced. The comparison of the peak pressure coefficients is less satisfactory.

Structural reliability and crosswind response of tall chimneys

Abstract The structural safety of tall industrial chimneys at ‘lock-in’ is investigated in terms of upcrossing probabilities. In this manner the inherent random nature of the load, as well as the uncertainties in the description of the load are accounted for. Peak factors and load factors in excess of those currently used in codes of practice are obtained.

Jans Smuts experiment: Details of full-scale experiment

Abstract A full-scale experiment undertaken on a portion of a large aircraft hangar at Jan Smuts Airport from 1980 to 1988 is presented. The instrumentation for this experiment consisted of 50 differential pressures transducers located at one corner of the hangar (49 external and 1 internal), on both the wall and roof, and wind speed and direction measurements. The paper concentrates on the pressures obtained for the roof of the hangar. A companion paper presents a comparison between the full-scale and wind-tunnel tests undertaken at the Division of Building Technology, CSIR.

South African Wind Loadings: Where to Go

Publisher Summary This chapter presents several investigations into the revision of wind-loading stipulations of the South African structural design code South African Bureau of Standards (SABS) 0160-1989. The chapter also presents a proposal regarding the new wind-loading stipulations of SABS 0160. Initially, a brief evaluation of selected aspects of the current code is made, comparing them with modern trends and overseas loading codes. This is followed by an examination of the applicability of European and American codes. The paper includes the information on the principles, structure, and content of the proposed wind-loading stipulations. The feasibility of adopting the European and American codes is discussed in the chapter. Finally, information on the proposed principles of the wind loading stipulations is presented.

A topographical study to investigate wind nuisance

Abstract Selected results of a small-scale wind tunnel investigation into the characteristics of the boundary layer influenced by a dominant topography are presented. The investigation has shown that the severe wind conditions experienced in a city centre approached by this boundary layer are due to an unfortunate combination of several factors.

The influence of upwind topography on the development of the boundary layer profile over a city centre

Abstract The paper describes the results of a preliminary investigation undertaken as part of a pedestrian level wind tunnel study within a city centre. The aim of the investigation was to study the development of the boundary layer profile in the city centre, influenced by a 150 m high hill, 1.3 km upwind of the city. The city is characterized as consisting predominantly of medium height buildings.

Gust loading factors for lighting masts

Abstract Gust loading factors for lighting mast structures are presented. These factors are arrived at by assuming perfect frequency coherence between the velocity and drag-force fluctuations. This assumption is investigated and found to be satisfactory for practical applications.