A shift in emphasis can be seen in the approach to structural design. More often structures are looked at ‘globally’, as whole structural units, rather than a group of individual elements. The investigation of this global behaviour, also described as ‘holistic’ or ‘whole building’ behaviour has been made possible by new theoretical achievements and the spectacular advance in computer technology during the last decades. The global structural analysis of buildings can be carried out following two routes.
First, sophisticated and complex computer packages based on the finite element method offer endless facilities and can handle even huge structures with a great number of elements. Second, analytical methods can also deal with whole structures leading to simple closed-form solutions, with the additional benefit of providing fast checking facilities for the computer-based methods. This book follows the latter route and, after describing and solving the complex theoretical problems of bracing systems covering many practical cases, intends to achieve the following three objectives:
• To present simple procedures and closed-form formulae which make it possible for the practising structural engineer to carry out a general structural analysis of the bracing system of building structures in minutes.
• To show that the main areas of structural design (stability, stress and frequency analyses) are not independent; indeed they can be linked by the global critical load ratio which can be used to achieve optimum structural solutions with high performance and adequate safety.
• To help to understand global behaviour better and to develop structural engineering common sense through the introduction of the most representative stiffness characteristics for the stability, stress and frequency analyses.
In applying physical and mathematical models which are based on the global behaviour of building structures, a unified treatment of the stress, stability and frequency analyses of bracing systems is presented for carrying out the structural analysis of buildings. In complementing the conventional ‘element-based’ design process, closed-form formulae and simple procedures are given for the global analysis of individual bracing elements and 3-dimensional bracing systems.
The conventional design process is normally based on the ‘local’ structural analysis of individual elements (columns, beams, floor slabs, walls, etc). This attitude is natural, since the structural system consists of individual elements. However, theoretical research, small-scale and large-scale tests and failures (and in some cases the lack of failures) in structural systems have indicated that complex structures cannot be considered simply as a collection of individual elements. The response of the structure is often more than the ‘sum’ of the responses of the individual elements since structural integrity ensures that the elements work together in a properly designed system and the structure develops some ‘global’ response through the complex interaction of its elements.
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