double floors using hollow core floor soffit of a hollow core flooring system double floors using hollow core floor hollowcore plank precast prestress hollow core slab ideal solution for hollow core unit and seating beam end reinforcement for hollow core slabs potential failure modes of hollow core precast prestressed hollow core slabs bb800 8 inch hollow core precast floor bb800 8 inch hollow core precast floor bb800 8 inch hollow core precast floor