This paper investigates the load-carrying mechanisms and the strength of thin-webbed, post-tensioned beams failing by crushing of the web. The shear strength in these members is significantly reduced because of the state of cracking in the web and because of the disturbance in the flow of stresses introduced by the prestressing tendons. The interaction between both effects is investigated. To that end, the results of six full-scale tests performed on actual prestressed beams extracted from a girder bridge are presented. The results are analyzed and various approaches for the modeling of such members are investigated and compared.