Probabilistic study of wind pressures on buildings

Date

1996-05

Journal Title

Journal ISSN

Volume Title

Publisher

Texas Tech University

Abstract

Probabilistic modeUng of wind induced pressures on buUdings is important in developing assessment of wind loading on buUdings, as weU as fatigue loading evaluation for building envelope of waUs and roof Most ofthe probability density function (PDF) models developed in the past were based upon wind tunnel resuhs, which have recently been shown to underestimate peak and standard deviation of real-life pressures. Full-scale buUding pressure data coUected at the Wmd Engineering Research Field Laboratory at Texas Tech University are used to develop probabUity density functions (PDF). Several records are used for every case in order to reduce the risk of being biased due to the randomness of field data. The closeness-of-fit test technique is used to verify the best PDF model to represent wind-induced pressures on buUdings. Extemal and internal pressures in regions representative of different aerodynamic phenomena are studied. Area-averaged pressures on roof comers and a stmctural member are also investigated. Effects of time averaging, turbulence mtensity level, and the angle of attack of approaching flow on pressure PDFs are evaluated.

It is found that a shifted lognormal distribution model is suitable to represent the PDFs of the pressures in windward waUs, and roof separation bubble, delta-wing vortices, and reattachment regions. For roof comer regions where more than one flow mechanism affect the pressures, the pressure PDFs demonstrate some properties that cannot be described with any available PDF model. However, a shifted lognormal PDF model is able to represent the taU ofthe pressure PDFs satisfactorUy. Internal pressures also follow the shifted lognormal distribution when there is an opening m windward waUs. Area-averaged pressures on roof comers and a roof purlin are found to foUow a shifted lognormal distribution. Time averaging appears to have Uttle effect on pressure PDFs for a wavelength of up to 20 ft/cycle. The effect ofthe turbulence intensity in an approaching wind flow is negUgible on pressure PDFs. In contrast, the angle of attack of 2in approaching flow has a marked influence on the pressure PDFs; the extent of this effect depends on the location ofthe pressure zone and the angle of attack ofthe incident wind flow.

The effects of non-Gaussian properties of pressures on the damage accumulation to glass is evaluated m this study. It is shown that shifted lognormal distribution for wind pressures yields the best damage estimation. In addition, preUminary results to calibrate safety indices of design codes of practice show that non-Gaussian properties of pressures have a significant effect on safety indices.

The pressure PDFs observed in this study can be used in the simulation of pressure histories for analytical studies, the fatigue assessment of building cladding, calibration of the safety indices as weU as validation of wind tunnel simulation techniques.

Description

Keywords

Buildings, Wind-presuure

Citation