Abstract
This study introduces a new type of precast, prestressed reactive powder concrete (RPC) bottom panel for a large-span composite slab. The bottom panels, which have one or two inverted ribs with openings, act as formwork during the construction stage. The paper experimentally investigated the crack characteristics, deflection, and normal section bearing capacity of four precast, prestressed ribbed RPC bottom panels under flexural load. The results indicated that the RPC ultimate strain under non-uniform compression is 5500x106 and the plastic influence coefficient of the section modulus is linear with the longitudinal reinforcement ratio. The tensile stress of RPC at the cracked section should be considered while calculating the flexural stiffness; the equation used to determine the nominal tensile stress of RPC as a major variable for calculating the crack width at the bottom of panels was proposed. The bottom panels generally exhibit an over-reinforced failure mode behaviour without the composite layer; the calculation method of the normal section bearing capacity of this mode was established.
Highlights
The composite slab is a semi-fabricated system that consists of a precast bottom panel and a composite layer
One reason for the limited span is that the prestressing wires in precast bottom panels provide most of the reinforcement of a composite slab; as a result, as the span of a composite slab increases, the amount of prestressing in the bottom panel must be increased, which leads to the excessive elastic compression and creeping loss of the prestress
The section with openings was chosen as the calculating section in this paper because it is the weakest section of a precast, prestressed ribbed reactive powder concrete (RPC) bottom panel
Summary
The composite slab is a semi-fabricated system that consists of a precast bottom panel and a composite layer. Following the assembly of the bottom panel, transverse reinforcements can be arranged in the rectangular openings, and a two-way solid composite slab that has good integrity is formed after the cast-in-place concrete is poured and hardened One reason for the limited span is that the prestressing wires in precast bottom panels provide most of the reinforcement of a composite slab; as a result, as the span of a composite slab increases, the amount of prestressing in the bottom panel must be increased, which leads to the excessive elastic compression and creeping loss of the prestress Another reason is that the flexural crack strain of an ordinary concrete is relatively low, so the crack width and deflection most likely cannot satisfy the serviceability requirements.
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