INTRODUCTION

General considerations

This text book focuses exclusively on the prediction of wind induced static and dynamic response of slender line–like civil engineering structures. Throughout the main part of the book it is taken for granted that the structure is horizontal, i.e. a bridge, but the theory is generally applicable to any line-like type of structure, and thus, it is equally applicable to e.g. a vertical tower. It is a general assumption that structural behaviour is linear elastic and that any non-linear part of the relationship between load and structural displacement may be disregarded. It is also taken for granted that the main flow direction throughout the entire span of the structure is perpendicular to the axis in the direction of its span. The wind velocity vector is split into three fluctuating orthogonal components, U in the main flow along–wind direction, and v and w in the across wind horizontal and vertical directions. For a relevant structural design situation it is assumed that U may be split into a mean value V that only varies with height above ground level and a fluctuating part u, , i.e. U = V + u. V is the commonly known mean wind velocity, and u, v and w are the zero mean turbulence components, created by friction between the terrain and the flow of the main weather system.