INTRODUCTION The overall response of structures in the natural wind is the result of several causes. This Item is one of a group concerned with methods of calculating the along-wind loading and response due to atmospheric turbulence. Part 1 (Derivation) provides a background discussion of methods of calculation and their implementation. Part 2 (Item 87035) provides a calculation procedure for the along-wind loading or response of line-like structures and Part 3 (this Item) provides corresponding procedures for buildings or plate-like structures. These three parts together supersede Item 76001@ the principal changes being to incorporate the updated wind properties given in Derivations 15@ 16 and 17 and the revised load/velocity admittance factors discussed in Section A3 of Appendix A. A computer program version of the calculation methods in Parts 2 and 3 will be issued as Part 4 of the series (Reference 12) to supersede Item 84034. The along-wind loading or response of a structure in the natural wind can be expressed in terms of a mean component@ due to the hourly-mean wind speed@ and a fluctuating component@ due to the turbulent fluctuations in wind speed about that mean. A full dynamic analysis for the fluctuating component is time-consuming but for most practical cases it can be replaced by an approximate method that treats the fluctuating response as the sum of a background (quasi-static) component and separate resonant components for each mode. This method is outlined in Derivation 18 and is described in more detail in Reference 2. It forms the basis of the calculation methods in this Item where it is further simplified by provision of precalculated loading factors for a range of wind and structure properties. An alternative@ more approximate@ approach is the gust method in which dynamic effects are ignored and a gust of an appropriate duration (dependent on the size of the structure) is assumed to act on the whole structure at a given time. The overall loading is then calculated on a quasi-static basis. This approach is appropriate only for structures for which the resonant component of response is negligible and is used for certain classes of structure in some national Codes of Practice. The gust method is discussed further in Derivation 18. Section 4 of the present Item gives a step-by-step method for calculating the along-wind loading or response@ in terms of a mean component and rms fluctuating components. With the assumption that the fluctuating wind speed and the response to it are stationary random processes@ expected maximum values of the along-wind component of loading or response can then be estimated. The normalised loading factors required in the method are presented graphically and in equation form. The required input data are discussed in Section 5. Section 8 gives worked examples of the application of the method. * The essential requirement is that the fluctuating drag force due to the along-wind component of wind-speed fluctuations can be assumed uncorrelated with drag fluctuations from other sources e.g. vortex shedding or across-wind motion.
ESDU 88019 C-1998 history
1998ESDU 88019 C-1998 CALCULATION METHODS FOR ALONG-WIND LOADING Part 3: Response of Buildings and Plate-like Structures to Atmospheric Turbulence