A study of the effects of opening sizes and locations on large-span prestressed hollow core slab integrity

Abstract

Prestressed hollow core slabs are popular to use for constructing the ceilings of halls with large spans. However, electromechanical systems requirements for large halls mandate the inclusion of openings in ceilings. This paper studies the opening size limitations to avoid losses in prestressed hollow core slabs service capacities. Forty-one large-span slab samples are analyzed, each with different opening sizes and locations along their spans. All tested slabs are designed to comply with the national standards. A Finite element model is used to apply the testing technique. Results are compared with the ACI, European and the Egyptian standards service requirements. Results indicate that openings of variable sizes at midspan reduce the slab service capacity by nearly 18 %, reaching 43 % for openings with 50 % opening width to slab width ratio or more. A significant rise in normal stresses in flanges and extensive shear stresses in webs are observed around the openings especially for wider openings relative to the slab width. The strands around the openings in this case suffer extensive axial stresses that exceed the design limits. Meanwhile, on having large openings near supports, the deflection limits at midspans are exceeded but the loss in capacity is much lower.