This paper presents a method for rapidly assessing the bending moments in simply supported bridge decks by the use of simple distribution coefficients. The theory behind the method is briefly explained, its present limitations tested and its use described by the study of some examples.

During the current world recession a great deal of effort has been expended by governments throughout the world on the management of existing bridge stocks and related structures. One vital area of concern is that of establishing the strength of decks to see if they can cope with current highway loading specifications. The strength of single elements is based on the factored stress resultants obtained from an elastic analysis, which may take the form of either a grillage or finite element approximation of the bridge deck construction. This approach requires the preparation of a considerable amount of data relating to geometry, material properties, connectivity, loading and support conditions. The resulting output then provides information at a large number of locations throughout the deck, from which the critical numbers are extracted and used as a basis for strength and serviceability checks. As the information required usually consists of maxima only, it makes sense to consider methods which provide results in a rapid but accurate manner confined only to a critical point, and which require the minimum of data input.

Engineers are drawn instinctively to simple methods of analysis or design if they provide answers which are not only accurate enough for their purposes, but compare favourably with more rigorous computational methods. Furthermore, if the information required can be presented in the form of a limited number of tables and/or charts which can be incorporated into standard Codes of Practice, then a computational methods of exceptional ease and simplicity can be made available for the practising bridge engineer.

A way of doing this, and presented in this paper, is to provide the engineer with tables of distribution factors which define the maximum bending moments at a critical section of bridge deck.

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