The Structural Engineer > Archive > Volume 35 (1957) > Issues > Issue 9 > Tests on Eccentrically Loaded Columns with Square Twisted Steel Reinforcement
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Tests on Eccentrically Loaded Columns with Square Twisted Steel Reinforcement

Investigation of the behaviour of twisted steel reinforcement (TS) in axially loaded columns revealed several important advantages over the more usual type of reinforcement, namely mild steel (MS). TS to C.P. 1144 is more efficient than MS and will devclop a stress of 54,000 psi at ultimate load, whereas the useful strength of MS is limited to that at yielding and may only be about 36,000 psi. 'Toughness' is also a valuable feature in the behaviour of TS columns. The load at first cracking of the concrete was reached at strains of 0.0013, this corresponding to the development of maximum stress in the Concrete, but ultimate strength was not developed until strains of 0.002 - 0.0025 were reached at loads some 10 per cent higher. In columns with MS the steel yields before the concrete dcvclops its full strength and the column fails immediately without warning. Hajnal-Konyi and the Authors' also pointed out that the effect of crecp is to increase the factor of safety for columns with TS as compared with columns with MS. Creep occurs under sustained loads and over a long period of time large deformations may take place. Strains at failure are much higher than a short laboratory test shows and therefore the steel will develop a higher stress. This increased load on the steel will partly offsct the effect of a reduction in concrete strength due to fatigue. The samc is not true for columns with MS becausc the stress level in the steel is limited by yielding. R. H. Evans and and K. T. Lawson

Author(s): Evans, R H;Lawson, K T

Keywords: eccentric loads;columns;square;reinforcement;deformed;cp1144;behaviour