An experimental investigation of steel-free deck slabs

Abstract

The steel-free deck slab developed in Canada used straps as a confinement system and relied on the stiffness of this confinement system rather than its strength. In this paper, a new approach, using the strength of a confinement system comprising unbonded prestressed bars, was investigated. In addition, the effect of the concrete strength and the steel ratio of the confinement system was examined. Seven large-scale one-way steel-free deck slabs were built using normal- and high-strength concrete, prestressed to different levels, and statically tested up to failure. The overall behaviour of the slabs was similar to that of slabs confined by straps. Cracking strength was not considerably enhanced. The slabs failed in punching shear mode with high loads. The new approach was not able to overcome the problem of the longitudinal crack, which developed in the tested slabs and reportedly appeared in all the steel-free slabs built or tested previously in Canada. Prestressing had a definite effect, however, on delaying the occurrence of this longitudinal crack, thereby enhancing serviceability. The paper recommends that the serviceability limit state of the steel-free slabs would be better assessed by the occurrence of the longitudinal crack, even though the ultimate capacity of the slabs is high.Key words: arch action, cracking, external prestressing, high-strength concrete, punching shear, steel-free deck slab.

Modelling high temperature effects on bridge slabs reinforced with GFRP rebars

“…On the contrary service problems may arise due to a deterioration of both bond strength and reinforcement Young modulus. The scheme with the bottom reinforcement of the slab unbonded in between the bridge beams is similar to the reinforcement-free bridge decks studied in Canada (see for instance [39]), which, in fact, suffered the problem related to cracking of the bottom surface of the deck slab in the service load range [40]. Similarly, the deterioration of bond strength during heating implies the need to reliably compute the displacements (i.e.…”

Long-term structural health monitoring of the Crowchild Trail Bridge

“…In addition, these types of cracks may lead to further deterioration of the bridge deck concrete, such as the reduced fatigue strength of the bridge deck. Bakht et al (2003) and Hassan et al (2002) agreed that cracking could be limited if a nominal amount of glass fibre reinforced polymer (GFRP) reinforcement was incorporated into the bottom of the steel-free deck. Prior to the use of GFRP reinforcement within steel-free decks, polypropylene fibres had typically been used with limited success to minimize and control the effects of thermal and shrinkage cracking.…”

Punching Shear Behavior of Externally Prestressed Concrete Slabs

“…Mufti et al (1993) investigated the possibility of producing a concrete deck slab that is entirely steel-free and capable of matching the load levels resisted by conventionally reinforced decks. Hassan et al (2002) also studied the effect of prestressing on the punching strength of steel-free deck slabs. A system of external unbonded prestressing bars was used as the lateral confinement system, rather than the steel straps used by Mufti et al (1993).…”