| A slab that is axially prestressed develops compressive membrane action that tends to increase significantly its strength. The behaviour of axially prestressed slabs was experimentally examined. Five unreinforced two-way slab specimens were built and tested to failure under monotonically increasing central load. Three of the specimens were constructed using plain concrete, while the other two were constructed using fibre reinforced concrete (FRC). Axial stress was applied using an external post-tensioning system; the system consisted of Dywidag bars and side steel beams. Parameters, such as lateral stress level, fibre inclusion, and varying the axial stress in one direction were investigated.; The level of axial stress was observed to affect all aspects of the behaviour, including cracking, deflection, stiffness, and failure mode. The higher the stress level, the higher the ultimate strength and stiffness, and the lower the ductility. A stress level as low as 2.0 MPa was able to provide lateral restraint necessary to prevent premature flexural failure of Specimen P-3, which failed in a combined flexural-punching mode at a significantly higher load than expected by flexural failure. Adding steel fibres in an amount equal to 1% by volume fraction resulted in a ductile punching shear failure and improved post-cracking behaviour and residual load-carrying capacity after reaching maximum load. |
