Development Length of High Strength Reinforcing Bars in Bond
Phil M. Ferguson an dJ. Neils Thompson
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A new type test beam was used to place the development length of the bar in a negative moment region such that the maximum steel stress and average bond stress could be calculated. Bars were high strength steel, yield point of 75 kips per sq in. of #3, #7, and #ll size with and without stirrups. Typically, bars split out in bond, but diagonal tension was often a complicating factor. The developed bond stress was lower as the development length or larger bars was increased, but the bond stress showed to be primarily a function of length rather than of bar size. Ultimate bond stress varied as fl when other factors were constant. Bar cover and beam widths were important factors. End anchorage was reasonably effective but seemed to increase the cracked widths observed.