The shear strength of pre-tensioned I beams with unreinforced webs

This paper presents the results of two-point loading shear tests on 50 pre-tensioned concrete I beams without web reinforcement. Although many of the beams carried a shear load greater than the cracking shear load, the amount of the excess could not be predicted, and it is concluded that failure should be considered to have occurred when the web is cracked in shear. An expression is developed for the diagonal cracking shear force. Test results already published are shown to give satisfactory agreement with this expression, and comparisons are made, for specific cases, between the ultimate shear load predicted by it and by other design equations and code rules.