LONG-TERM BEHAVIOUR OF PRECAST PRESTRESSED HOLLOW CORE SLABS WITH CONCRETE TOPPINGS
The purpose of this paper is to study all the autogenous effects causing relative movement between the concrete toppings and the precast prestressed hollow core unit (HCU). These include creep, shrinkage and thermal stresses over a long-term period. To achieve this, a full size composite floor slab comprising five HCUs of area 6 m 6 m was constructed on-site. Distributed load of 10 kN/m2 was applied on the composite floor slab and left for 24 months to be exposed to the UK weather. The study found that the creep increases in tension and compression over the loading period. When temperature is considered, the creep during a cold day in winter is 50 10-6 strain per MPa higher compared to a hot day in summer. From the measured top and bottom temperature, a theoretical approach was used to determine the internal temperature within the composite section. The internal temperature especially at the interface was later used to study the shear stress behaviour over the exposure period. The interface shear stress due to the sustained imposed load, differential shrinkage and thermal stresses fluctuates between 0.01 and 0.40 N/mm2 , which is below the BS 8110 values. This shows that the interface was able to resist shear stress over the exposure period without any additional reinforcement.