SHEAR CAPACITY OF NOTCHED PRESTRESSED HOLLOW-CORE SLABS WITH CIRCULAR VOIDS

In many structural applications, prestressed hollow core slabs need to be provided with different types of end notch. The frequently used types of notch and cut-out, and their effect on the failure mechanisms and shear capacity of the hollow core units are discussed. The theoretical principles and procedures for determining the shear capacity of notched hollow core members are presented. A reduction factor to be applied to the shear capacity of corresponding unnotched slabs is introduced. Methods of analysis, solutions and iteration procedures for the different failure mechanisms and for the evaluation of the shear capacities of both notched and unnotched slabs are proposed. The principles and procedures are applied to prestressed hollow core slabs with circular voids and curved end notches and the reduction factors are evaluated by using the finite element method. The slab thickness, notch depth, and amount of prestressing reinforcement are varied. It is concluded that: (i) the shear capacity is determined by shear tension failure of the web and is not reduced if the relative depth of notch is less than 40%; (ii) the shear capacity is governed by flexural cracking of the bottom edge of the slab and is considerably reduced if the relative depth of notch is more than 40%; and (iii) the amount of prestressing reinforcement has a minor effect on the reduction factor (<15%). A tentative design recommendation for the reduction factor is also given.