Loading tests of full scale specimens of the anchorage zone of prestressing tendons were carried out. Factors.of the area of the cross section of members, concrete strength, and amount of lateral reinforcement (amount of spiral and hoop reinforcement) are considered to affect the cracking behavior and ultimate strength of the anchorege zone, and those factors were taken as parameters. From the relations between each parameter and the behaviors of specimens, formulae by which cracking and ultimate strengths can be predicted are presented here. Based on a new idea of cumulative strength of concrete, and spiral and hoop reinforcement, the formulae were derived. Proposed formulae for cracking and ultimate strengths were examined by the application to the experimental data which ware published preveously, and it was confirmed that they gave.good prediction and that they were satisfactorily applicable.
