Flexural behavior of fire damaged self-compacting concrete beams strengthened with fiber reinforced polymer (FRP) wrapping

Abstract

PurposeBuilding elements that are damaged by fire are often strengthened by fiber wrapping techniques. Self-compacting concrete (SCC) is an advanced building material that is widely used in construction due to its ability to flow and pass through congested reinforcement and fill the required areas easily without compaction. The aim of the research work is to examine the flexural behavior of SCC subjected to elevated temperature. This research work examines the effect of natural air cooling (AC) and water cooling (WC) on flexural behavior of M20, M30, M40 and M50 grade fire-affected retro-fitted SCC. The results of the investigation will enable the designers to choose the appropriate repair technique for improving the service life of structures.Design/methodology/approachIn this study, an attempt has been made to evaluate the flexural behavior of fire exposed reinforced SCC beams retrofitted with laminates of carbon fiber reinforced polymer (CFRP), basalt fiber reinforced polymer (BFRP) and glass fiber reinforced polymer (GFRP). Beam specimens were cast with M20, M30, M40 and M50 grades of SCC and heated to 925ºC using an electrical furnace for 60 min duration following ISO 834 standard fire curve. The heated SCC beams were cooled by either natural air or water spraying.FindingsThe reduction in the ultimate load carrying capacity of heated beams was about 42% and 55% for M50 grade specimens that were cooled by air and water, respectively, in comparison with the reference specimens. The increase in the ultimate load was 54%, 38% and 27% for the specimens retrofitted with CFRP, BFRP and GFRP, respectively, compared with the fire-affected specimens cooled by natural air. Water-cooled specimens had shown higher level of damage than the air-cooled specimens. The specimens wrapped with carbon fiber could able to improve the flexural strength than basalt and glass fiber wrapping.Originality/valueSCC, being a high performance concrete, is essential to evaluate the performance under fire conditions. This research work provides the flexural behavior and physical characteristics of SCC subjected to elevated temperature as per ISO rate of heating. In addition attempt has been made to enhance the flexural strength of fire-exposed SCC with wrapping using different fibers. The experimental data will enable the engineers to choose the appropriate material for retrofitting.

Flexural Behavior of Reinforced Concrete Beams with FRP Bars Exposed to Elevated Temperature

“…Moreover, the nature of cooling significantly affects the strength loss of all the beam specimens. All the watercooled beam specimens showed efficient performance compared to air-cooled beam specimens, similar trend in the results were observed by Mathews et al [4].…”

“…Many researchers have conducted detailed study on the physical and strength performance of concrete and FRP reinforcement steel under elevated temperatures. When concrete is exposed to a higher temperature, the weight loss, deformation changes in aggregate and damage of CSH gel, chemical changes, spalling, and decreases in mechanical properties occurs and lead to deterioration of the structural members [4]. Yield strength, ultimate strength, and modulus of elasticity of steel materials degrade when subjected to high temperatures [5].…”

Evaluation of Structural Response in Ultra-High-Strength Concrete and Carbon Fiber Reinforced Frames Exposed to High Temperatures Using Numerical Simulation

“…Through numerical simulations, it was demonstrated that the fire resistance of structures is significantly affected by the duration and intensity of exposure, as well as by the materials used. Therefore, [3] investigated the exposure to high temperatures in conventional reinforced concrete structures and their loss of strength under heat. For this reason, the implementation of carbon fibers was proposed.…”

“…This concludes that carbon fiber reinforced beams are the best option to achieve greater flexural strength under high temperature conditions. In previous studies [3,4], the mechanical properties of high-strength concrete reinforced with hybrid steel and polypropylene fibers were evaluated after exposure to different temperatures. The results showed a decrease in both compressive and flexural strength with increasing temperature.…”

The Thermal Effects on the Self-Compacting Concrete Beams Exposed to the Fire

“…Fire disasters can occur under or on the ground and sometimes in the most unexpected circumstances and considered one of the most serious potential disasters for most structures [1]. The widespread use of concrete as a building material has led to the need for a comprehensive understanding of fire effects and strengthening of affected concrete structures [2].…”