Some applications of the electronic computer to structural engineering

Composite construction in structural steel and concrete slab in the early years was mostly designed for medium-span highway bridges in which steel beams were seldom fully encased and for which shear connectors were necessary to maintain the composite action against the vibration due to traffic. In consequence the majority of the experimental investigations were concerned with the behaviour of composite beams provided with shear connectors and the load-carrying capacity of various types of shear connector. Very little has been done on the determination of horizontal shear resistance of composite Tee-beams in which the fully encased steel joist has no shear connectors. F. K. C. Wong

In 1952 a series of tests were carried out on a reinforced concrete building and unexpected results were obtained from two tests to destruction on interior slab panels. In both tests the collapse load was more than twice the load predicted by the yield-line method. In a later paper Professor Ockleston, who carried out the tests, showed that this unexpected result can be explained by an arching action due to the development of compressive membrane stresses in the concrete. It was, however, not possible at that time to predict the extent to which arching action will affect the strength of a slab. This paper presents an analysis of arching action in beams and one-way slabs with lateral restraints and a method of estimating the ultimate strength of interior slab panels due to the combined effect of bending and membrane stresses. The ultimate strength is presented in graphical form as a function of the steel ratio and the ratio of span to effective depth. The results of a short series of tests show good agreement with values calculated according to the theory. K. P. CHRISTIANSEN

The paper deals briefly with the application of reinforced concrete cellular deck for bridges (hereinafter referred to as box girder) in the USA and its wide use in the State of California for structures in urban expressway systems. The history of the box girder structure, its advantages, economy and applications are mentioned. Design specifications both theoretical and practical are discussed and illustrated. Finally a typical example of a box girder detail is shown together with sketches and photographs of box girder application in viaducts and flyovers. S. H. Studzinski