Prestressed Beams Lifting Off Elastic Supports

The static strength of stud shear connections in composite beams has been derived from the analysis of 110 push tests which include eight new tests in which measured axial loads were applied to the connectors. Allowances have been made for the variations in the number andposition of the studs in push tests and for the difference between the external restraints in push tests and in beams. The static strength prediction equation differs from those in Codes of Practice, as it is in a form that allows for variations in the strengths and moduli of both connection materials, and hence obviates the need to distinguish between lightweight and normal-density concrete or to set limits to the stud material strength, and it is in a form which allows for the beneficial effect of the redistribution of the load in groups of connectors subjected to similar displacements. D.J. Oehlers and Professor R.P. Johnson

Short-term longitudinal reinforcement strain distributions in reinforced concrete tension members were measured using electric resistance strain-gauges. These were installed at 12.5 mm centres in a duct milled longitudinally through the centre of the reinforcement, thus avoiding degredation of the steel/concrete interface. Fourteen specimens were tested, all reinforced with a single rod positioned centrally in the cross-section. Twelve specimens had square cross-sections, one specimen had a rectangular cross-section, and one specimen was made with lightweight aggregate concrete. R.H. Scott and P.A.T. Gill