Western Avenue Extension - the Design of Section Five

The general theory of beams curved in plan with torsional restraint at the supports is explained, with particular reference to prestress loading. It is proved that the torsional moments due to prestress loading are solely dependent on the support bending moments, and the conditions of concordancy are formulated for a circularly curved beam. It is suggested that for most practical cases the support bending moments in circularly curved beams can be calculated to sufficient accuracy assuming the beam is straight, and the order of accuracy is given. A similar approximation can also be made when analysing the effects of loads other than prestress. R.J. Garrett and R.A. Cochrane

Particular requirements of a length of urban elevated motorway are described, which have been satisfied by the use of a bridge deck using ‘top-hat’ section box beams with no transverse diaphragms. The deck has proved economical and suitable for a wide range of bridges. During the development of the design of the deck, methods of analysis for the effect of concentrated loads have been investigated and the paper describes an approach based on finite element techniques and the derivation from this of a simpler technique for design ofice use, both of which provide satisfactorily accurate results. D.M.A. Hook and B. Richmond

Analytical and experimental studies have been carried out at Imperial College into various aspects of limit state design when applied to highway bridges. To obtain an indication of the inherent load factors against the various appropriate limit states, three typical bridges were theoretically investigated. The predicted load factors were compared with those proposed for use with new design procedures. Dr. A.R. Flint and L.S. Edwards