Fire Performance of FRCM Strengthened Columns: Experimental Investigation

Abstract

The utilization of Externally Bonded (EB) fiber systems for the rehabilitation and retrofitting of existing and deteriorated RC structures has grown in recent decades, given their demonstrated promise and convenience. Fiber Reinforced Polymers (FRP) system is the most common type of EB strengthening systems. However, one of the main concerns about FRP strengthening systems are their low resistance to elevated temperatures or fire exposure. This poor fire performance of FRP systems motivated researchers to use different fireproofing systems or use a more durable type of EB fiber systems. Fabric Reinforced Cementitious Matrix (FRCM) strengthening system has been introduced as an alternative to FRP systems, especially when there is a high risk of fire exposure. This thesis investigates the fire performance of twenty short circular RC columns strengthened with poly-paraphenylene-ben-zobisoxazole (PBO) FRCM and Carbon FRP (CFRP) systems. The columns were categorized into two phases, each featuring different post-curing storage times. The study examined various parameters, including the choice of strengthening system (PBO-FRCM or CFRP), the number of strengthening layers (ranging from 0 to 4 layers), the type of fireproofing applied (none, Sikacrete 213F, or intumescent paint), and exposure to fire. Following ASTM E119 standards, columns from both phases were subjected to fire exposure in a full-scale furnace, while phase 2 columns underwent testing under concentric loading until failure after fire exposure. Results showed that the use of cement-based insulation has significantly reduced the temperature readings at all locations within the section by 60%. The cement-based insulated PBO-FRCM strengthened column demonstrated the highest resistance to fire exposure, as the temperature readings were significantly less than the other columns, and it retained about 92.1% load capacity of the unexposed counterpart. Additionally, the cement-based insulated PBO-FRCM strengthened column underwent minimal displacement when subjected to a sustained load during the fire test. The column’s axial capacity was predicted using different ACI codes and developed models. The predicted capacity of the unexposed columns using ACI codes were within 7% of the actual capacity, while the model used to estimate the post-fire axial capacity was within 14%.