Factors governing the fire response of prestressed reactive powder concrete beams

Abstract

This paper presents the details of fire test on eight prestressed reactive powder concrete (RPC) beams cured with 150°C hot-air condition. The test specimens were varied in load ratios/degree, cover thicknesses of tendons, bonded and unbonded tendons, partial prestressing ratios. The thermal fields, deflections behaviour, effective prestress, fire endurance, failure modes, and crack patterns of the beams were observed and recorded during the tests. The post-fire tests observation reveals that no obvious thermal-induced spalling occurred on the prestressed RPC beams prepared in hot-air curing. The fire tests results indicated that the failure of prestressed RPC beams was driven by direct fire exposure and fracture of tendons and longitudinal rebars after generation of wide cracks in the beams. In extreme fire, prestressed RPC beams that are under-reinforced at ambient temperature may fail as the low-reinforced beams. The load ratios and cover thicknesses of tendons are the key factors affecting the fire resistance of the prestressed RPC beams. With the decrease of the load ratios and increase of cover thicknesses of tendons, the fire resistance is dramatically improved. Bonded prestressed RPC beams showed superior performance to equivalent unbonded prestressed RPC beams in fire. The whole scale transferring effect of prestress loss in unbonded beams should be considered for fire resistance performance design based on structural systems.

A Numerical Investigation into the Effectiveness of Composite Jacket Strengthening (CJS) on Fire-Damaged Concrete Beams

“…Yang et al [17] demonstrated that decreasing load ratios and shear span to effective depth ratios increased fire resistance while increasing longitudinal reinforcement and stirrup ratios prevented cracking and reduced shear failure fragility. The research conducted by Yan's team [18][19][20] focused on the investigation of the response of pre-stressed ultra-high performance concrete (UHPC) beams subjected to ISO fire. They also developed a novel two-stage hot air curing method to mitigate spalling.…”