RATCHETTING TESTS OF A STEPPED BEAM UNDER STEADY TENSION AND CYCLING BENDING

Seven identical stepped beams made of a lead alloy, were loaded by steady tension and cyclic bending. Three bending moments superimposing equal hogging and sagging were used in the tests. Six different tensions were also used. After tests of 15 cycles, most beams were re-loaded with a greater mean tension and the same cyclic bending moment. Strains were measured in the (circular arc) fillets at the step and in the shank. Ratchetting strains per cycle decreased during each test; steady state values were estimated and related to the load magnitudes. The common use of the 0. 2 per cent proof stress as the yield stress for an equivalent elastic-perfectly-plastic material has been shown to be extremely conservative.