* Corresponding author. Tel.: #679-212223; fax: #679-302567. E-mail addresses: sharma-r@usp.ac.fj (R.N. Sharma), pj.richards@auckland.ac (P.J. Richards) 1 Senior Lecturer. Journal of Wind Engineering and Industrial Aerodynamics 83 (1999) 147}157 The in#uence of Reynolds stresses on roof pressure #uctuations R.N. Sharma!,*,1, P.J. Richards1," !Department of Technology, University of the South Pacixc, P.O. Box 1168, Suva, Fiji "Department of Mechanical Engineering, University of Auckland, Private Bag 92019, Auckland, New Zealand Abstract This paper describes a further development of the quasi-steady theory to include the e!ect of uw Reynolds stress on building surface pressures. The theory predicts that uw Reynolds stresses have a signi"cant in#uence in suppressing roof pressure #uctuations, even though its magnitude is typically much smaller than variances for wind velocity components in the atmospheric boundary layer. Experimental evidence for this is provided by a wind tunnel investigation of roof pressures on a 1 : 50 scale model of the Texas Tech University (TTU) test building. This novel result immediately explains the overprediction of RMS roof pressure coe$cients by the theory that incorporates only the three turbulence components. It also explains the apparent loss of mid-frequency response of roof pressures reported in the past. It is speculated that Reynolds stresses are also responsible for shear layer instabilities that are believed to be responsible for a number of observed phenomena related to roof pressures. ( 1999 Elsevier Science Ltd. All rights reserved. Keywords: Reynolds stress; Quasi-steady theory; Roof pressures 1. Introduction Wind loading codes such as the AS1170.2-1989 [1] utilise the quasi-steady ap- proach in which #uctuations in surface pressure are assumed to follow #uctuations in wind velocity directly. Hence, the peak load is calculated from a mean pressure coe$cient and the design gust velocity pressure. The calculation of a design load in this manner is strictly valid only when the assumption of one-to-one relationship 0167-6105/99/$ - see front matter ( 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 7 - 6 1 0 5 ( 9 9 ) 0 0 0 6 8 - 9