Flexurally Rigid Support of Prestressed Hollow Core Slabs with Post-tensioned Beams

Abstract

Flat slabs with long spans can be economically manufactured only in the form of precast prestressed concrete elements. However, the precast slab elements must be supported on a beam within the column strip. The beam resists the loads from the precast hollowcore concrete slabs and transmits these to the columns. Prestressed hollowcore slabs are reinforced exclusively with prestressing strands. The cross-sections of these prestressed hollowcore slabs have hollow cores that are separated from each other by narrow unreinforced webs. The compressive stresses due to prestressing enable the webs to provide the required shear resistance, even without reinforcement. However, the cross-sections and hence the webs react very sensitively to shear deformations as well as to transverse bending and transverse stress. This loading arises in particular from the forces imposed by the precast slabs on a flexural beam. Deformation of the flexural beam cannot be prevented without an active force supporting the flexural beam.