Following structural engineering practice of the 1970s, engineers designed the Citicorp Building for the action of wind in each of the structure's principal axes. One problem they faced was how to determine design values by combining simultaneous wind loads from the means and root mean squares of these loads. Given the technology available at the time, the simplifying assumption was made of decomposing the effects of a corner wind into the sum of the effects on two adjacent faces, as if these wind loads were static and perfectly correlated, which they are not.
View Article and Find Full Text PDFFor the database-assisted design (DAD) of low-rise building purlins and girts, a method is proposed that explicitly accounts for wind directionality by using directional wind tunnel measurements, directional wind speed data, and publicly available software. The method consists of four steps: (1) assignment of wind loads induced by a unit directional wind speed on purlins and girts from pressure taps and their tributary areas; (2) development of bending moment and shear force influence coefficients for line loads on purlins and girts; (3) multiplication of loads from step 1 by influence coefficients from step 2 and estimation of the peak bending moments and shear forces thus obtained; and (4) use of nonparametric statistics to calculate peak moments and shear forces with a specified mean recurrence interval for various building orientations and accounting for wind directionality. For one example of wind effects on purlins, (1) comparison of the Envelope Method in ASCE 7-16 (taken as 100%) with the most demanding aerodynamic case from wind tunnel tests shows differences ranging between +10% and -25%; and (2) comparison of the ASCE 7-16 method accounting for the wind directionality factor with directional wind loads using nonparametric statistical methods shows differences ranging between +21% and -25%.
View Article and Find Full Text PDFUsing Database-Assisted Design and the Tokyo Polytechnic University Aerodynamic Database, we show that face winds put more structural demand than corner winds do on the Citicorp Tower in Manhattan. This 59-story building, supported by four midside columns, famously had to undergo secret emergency strengthening shortly after its completion in the 1970s to withstand corner winds.
View Article and Find Full Text PDFThis paper illustrates the application of the database-assisted design (DAD) method to the wind design of high-rise buildings. The paper uses publicly available wind tunnel data and DAD procedures to compare responses to (1) corner winds and (2) face winds of a high-rise building of square cross-section supported by a central core column and four mid-side legs. The responses being considered consist of overturning moments, and of demand-to-capacity indexes (DCIs) of selected members, including multistory chevron braces.
View Article and Find Full Text PDFA method is presented for calculating the uncertainty associated with the estimation of peak pressure coefficients from wind tunnel test records of various lengths and how this uncertainty influences design wind effects. The proposed method is applicable to any type of structure and any type of civil engineering aerodynamic testing facility, including large-scale facilities. As an example of the application of the method, an investigation is presented of time series belonging to five categories of pressure coefficients implicit in Chapter 27 of the ASCE 7-10 Standard.
View Article and Find Full Text PDFJ Struct Eng (N Y N Y)
January 2018
This paper briefly reviews recent and current National Institute of Standards and Technology (NIST) research aimed at improving standard provisions and advancing structural design practice for wind loads. The research covers: (i) New wind speed maps for the conterminous United States; (ii) Risk-consistent estimation of wind load factors for use with the wind tunnel procedure; (iii) Modern peaks-over-threshold approaches to estimation of peak wind effects; (iv) User-friendly procedures for the database-assisted design of rigid and flexible structures; (v) Novel approaches to codification of pressures on cladding and components; (vi) Modern modeling of synoptic storm planetary boundary layers and its implications for super-tall building design; (vii) Computational Wind Engineering (CWE); (viii) Tornado climatology and development of tornado-resistant design methodologies; (ix) Joint climatology of wind speeds, storm surge and waves heights, and estimates of their combined effects on structures.
View Article and Find Full Text PDFJ Struct Eng (N Y N Y)
January 2018
This paper presents a methodology for analyzing wind pressure data on cladding and components of low-rise buildings. The aerodynamic force acting on a specified area is obtained by summing up pressure time series measured at that area's pressure taps times their respective tributary areas. This operation is carried out for all sums of tributary areas that make up rectangles with aspect ratios not exceeding four.
View Article and Find Full Text PDFASCE ASME J Risk Uncertain Eng Syst A Civ Eng
April 2017
A 2004 Skidmore Owings and Merrill report (in Simiu E. (2011) , Appendix 5, Wiley, Hoboken, NJ) notes that the ASCE 7 Standard (American Society of Civil Engineers (2002) ASCE 7-02, Reston, Va) is incomplete insofar as it provides no guidance on wind load factors appropriate for use with the Standard's wind tunnel procedure. The purpose of this paper is to contribute to such guidance.
View Article and Find Full Text PDFEstimating properties of the distribution of the peak of a stationary process from a single finite realization is a problem that arises in a variety of science and engineering applications. Further, it is often the case that the realization is of length while the distribution of the peak is sought for a different length of time, > . Current methods for estimating peaks of time series have drawbacks that motivated the development of a new procedure, based on the method, an advantage of which is that it often results in an increased size of the relevant extreme value data set compared with procedures.
View Article and Find Full Text PDFExternal pressure coefficients specified in the ASCE 7-10 Standard, used to determine design wind pressures for the components and cladding of buildings, are developed from wind tunnel test data that date back 30-50 years. In recent decades, advances in pressure measurement and computer technology have made it possible to obtain simultaneous pressure records, with high sampling rates, at many more wind tunnel pressure taps than was the case in the past. This paper proposes a method to calculate external pressure coefficients using aerodynamic wind tunnel databases such as Tokyo Polytechnic University's large, publicly available database.
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