Performance of Fire-deteriorated Concrete Beams Strengthened with NSM Laminates

A Jadooe,K Abdouka,R Al-Mahaidi

doi:10.1088/1757-899x/433/1/012003

Abstract

Exposure of RC beams to fire may lead to a decrease in their load capacity and stiffness of the beams, both during heating and after the beam has cooled following the fire. The degree of damage is related to the fire’s intensity in terms of temperature and duration. This investigation is concerned with the effectiveness and suitability of the CFRP near-surface mounted (NSM) laminate system in terms of repairing RC beams after exposure to elevated temperatures. In the experimental work, the ISO-834 standard fire curve was adopted to test the beams. Two beams were tested at normal temperature exposure, while the other beams were heated to the target temperature using a large horizontal furnace. The experimental parameters involved in this study were the type of heat exposure, the level of heat exposure, and the insulation effect. Although a reduction did occur in the stiffness and ultimate load of affected beams, repairs with NSM laminates were found to offer an effective technique for increasing the overall stiffness and load carrying capacity of the beams.

Highlights

Rapid heating resulting from fire can cause many changes in structures due to thermal dilatation, as well as creep and thermal shrinkage of concrete caused by water loss
The major focus of this investigation was to use an experimental perspective to study the performance of RC beams exposed to heating and gradual cooling, and to investigate the repair of heat deteriorated beams using near-surface mounted (NSM) CFRP laminates with epoxy and cementitious adhesives
The NSM laminates were applied in grooves cut into the concrete surface to maximally utilise the benefits of this technique

Summary

Introduction

Rapid heating resulting from fire can cause many changes in structures due to thermal dilatation, as well as creep and thermal shrinkage of concrete caused by water loss. These changes can create large internal stresses and lead to large fractures and cracking. In extreme cases, when heating by fire is rapid, explosive spalling of concrete may occur. The influence of heating is most readily seen in the form of surface cracking. Arioz [3] demonstrated that at 600 °C, surface cracks were more visible and more obvious that when the temperature rose to 800 and 1000 °C, respectively. In a typical fire scenario, it was noted that the temperature distribution during heating is quite different to that during the cooling phase, as heat continues to be transferred to the interior from the exterior, hotter, parts of the structure [4]

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Discussion

Conclusion