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Synopsis A potential method for reducing the weight of the roadway deck on medium- to long-span composite bridges is to use an open steel-concrete sandwich. This consists of a concrete core which is cast against a steel plate, the necessary shear connection being provided by epoxy resin adhesive. Open sandwich beams and slabs constructed in this manner have been appraised by testing over spans of 1·8 and 0·9 m, respectively. Then carried loads equivalent to wheels of an HB vehicle with an adequate safety margin, and current designprocedures generally underestimated both theirflexuraland shear strengths.

This experimental study was undertaken with the aim of examining the flexural behaviour of a skew slab bridge deck with particular regard to the obtuse corners and the boundaries of the structure. The investigation considered bending and twisting moments, and reactive and shearing forces under concentrated point loads.Tests were carried out on a simply supported asbestos-cement slab, with a 45° skew angle. Experimental results are compared with finite element solutions.

Synopsis The paper reports the results offlexural tests on highly converted prestressed high alumina cement concrete T beamsfrom schools in Dundee. Owing to the low strength of the concrete, all beams failed in compression. Values of elastic modulus, creep and loss of prestress are estimated from test data and compared with the provisions of CP 110. Recommendations are made regarding appropriate values of elastic modulus and creep.

Synopsis In order to reduce the weight of roadway slab on medium- and long-span composite bridges, a possible alternative in the form of a steel-concrete-steel sandwich has been appraised. This consists of a concrete core, precast or otherwise, to which is attached reinforcement in the form of flat steel plates by means of epoxy resin adhesive. Specimens of the order of 100 mm thick were tested statically over a span of 1·8 m, and carried loads equivalent to wheels of the HB vehicle with an adequate safety margin. Accepted design procedures gave reasonable prediction of the ultimate loads.

Summary The paper describes the results of tests on eight square prestressed concrete slabs having unbonded wires. The ratio of transverse prestress to longitudinal prestress (γi,) was varied hetween 0 and 100%. A system of wheel loads based on AASHO specifications was used and it was found that, for the upper range of values of γiultimate loads were considerably in excess of those predicted by the use of yield-line theory. It is suggested that at least part of this increased load capacity could be utilized if a suitable design criterion were adopted.Summary The paper describes the results of tests on eight square prestressed concrete slabs having unbonded wires. The ratio of transverse prestress to longitudinal prestress (γi,) was varied hetween 0 and 100%. A system of wheel loads based on AASHO specifications was used and it was found that, for the upper range of values of γi ultimate loads were considerably in excess of those predicted by the use of yield-line theory. It is suggested that at least part of this increased load capacity could be utilized if a suitable design criterion were adopted.

Summary The paper describes tests on a number of dry mixes, using the Vebe and compacting factor principles, together with a third test based on the compacting factor test. The modified compacting factor test substitutes a period of vibration for the fall under gravity of the normal apparatus. It is shown that the normal compacting factor test does not reflect the compaction properties of very dry mixes, as the amount of work done on the concrete is too small. The Vebe test is shown to be satisfactory and is recommendedfor more general use with dry mixes.

Summary This paper describes experimental work on the compaction of concrete by table vibration. The cases of castings of small depth and those of greater depth are separated and guiding principles suggested for each. The effects of rotational instability and the injfuence of the mould are considered.