Civil Engineering Works for the new Plate Glass Works for Pilkington Brothers Limited, St. Helens

The development is described of a design for a range of precast concrete bridge beams of U-section which strive for economy of construction and structural efficiency. Methods of analysis for the effect of concentrated loads have been investigated including finite element techniques from which simple methods for design office use have been derived. Standard construction details are proposed in the paper and there are examples given of how U-beams may be used in superstructures. Tendered costs are also given for two projects already under construction. E.C. Chaplin, R.J. Garrett, J.A. Gordon and D.J. Sharpe

Tests are described of a quarter-scale concrete simply supported bridge deck composed of U-section pretensioned beams and in situ top slab. The bridge behaved linearly at design and up to one third overload. No serious deterioration of load distribution occurred after equivalent full HB loading was repeated 2000 times at midspan in both central and eccentric positions with respect to the longitudinal centre line. Two-dimensional analysis using plate theory was found to be adequate in predicting longitudinal beam moments. The finite strip method was found to be efficient in analysing both transverse and longitudinal stresses. An ultimate load test was carried out and the cracking and collapse load factors were satisfactory. A.R. Cusens and J.L. Rounds

Dr. G. Somerville (M): I have a few questions I would like to ask regarding the two methods of analysis which were finally selected, namely, the equivalent grillage and the space frame analysis.