Assessing concrete strength in fire-damaged structures

Wróblewska, Julia; Kowalski, Robert

doi:10.1016/j.conbuildmat.2020.119122

Cited by 51 publications

(17 citation statements)

References 25 publications

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“…Determining the residual capacity of reinforced concrete (RC) beams involves understanding the effects of temperature on concrete and steel. Concrete has a good fire performance due to its low thermal conductivity and high thermal capacity but presents loss on the residual strength depending on the severity of the fire [2], [3]. After fire temperatures between 500 and 600ºC, the steel recovers its strength to room temperatures, as indicated by Neves et al [4] and Van Coile et al [5], respectively.…”

Section: Introductionmentioning

confidence: 98%

Applicability of the 500°C isotherm method in determining the strength of reinforced concrete beams after fire

Costa

Silva

Pires

et al. 2022

Rev. IBRACON Estrut. Mater.

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A procedure to estimate the residual bending moment and the shear load capacity after fire in reinforced concrete beams was evaluated. The calculation method is based on the 500ºC Isotherm Method, adopting the reduction coefficients proposed by Van Coile et al. (2014) for the steel yield strength. The proposed method validation was done from experimental results of 62 reinforced concrete beams available in the literature. It was possible to observe a good approximation of the analytical method with the experimental data. For the bending moment an average ratio M r ana / M r exp of 1.04 and standard deviation of 0.15 was found. For the shear force an average ratio V r ana / V r exp of 0.85 and standard deviation of 0.23 was found.

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Section: Introductionmentioning

confidence: 98%

Applicability of the 500°C isotherm method in determining the strength of reinforced concrete beams after fire

Costa

Silva

Pires

et al. 2022

Rev. IBRACON Estrut. Mater.

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“…In most cases, these methods allow the assessment of the degree to which the considered material has been degraded by its exposure to high temperatures. The evolution of the concrete’s mechanical properties as a function of temperature is well known and is extensively described in numerous state-of-the-arts and original publications (Pimienta et al , 2019; Wróblewska and Kowalski, 2020; Felicetti et al , 2009). At the same time, the analogous data related to the behaviour of the steel rebars after fire episodes considered in this paper seem to be still insufficiently represented.…”

Section: Introductionmentioning

confidence: 99%

Properties of quenched and self-tempered reinforcing steel subjected to high temperature and different cooling conditions

Hager

Kańka

Maślak

2021

JSFE

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Purpose The study presents test results concerning the impact of high temperature and different cooling conditions on the mechanical properties of quenched and self-tempered reinforcing steel. The purpose of this paper is to clarify the extent of the history of the material’s temperature development profile, the course and the intensity of fire exposure and how cooling conditions determines its properties. Design/methodology/approach Each specimen series was heated to the temperatures of T = 200°C, 400°C, 600°C, 700°C, 800°C and 1,000 °C. The specimens were either slowly cooled down or subjected to rapid cooling with water quenching, which can be encountered during a firefighting operation. Additionally, stress–strain relationships, microhardness and structural observations were also performed. Findings The results of the presented experiments have shown that the steel bars previously heated in fire conditions were very sensitive to the cooling intensity. The test results from the steel specimens – that were heated and quenched with water – demonstrate an increase in tensile strength but a significant reduction in material plasticity. Originality/value The presented piece of work provides a contribution for fire safety engineering giving insight into the fire behaviour of reinforcing steel under fire conditions and subjected to rapid or slow cooling. This study has shown the threats arising from thermally induced changes in steel microstructure because of high-temperature exposure. It should also be noted that structure changes may have a local character and refer to steel rebars that are exposed because of fire spalling of concrete cover.

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“…Concrete is safer under fire due to noncombustibility and low thermal conductivity in comparison to other widely used construction materials, such as glasses [2,3], steel [4], composites [5], and wood [6]. However, the physical, chemical and mechanical properties of concrete deteriorate due to fire exposure [7,8]. The structural and occupant safety in fire depends on the behaviour of concrete; thus, the performance of concrete under elevated temperature is extensively investigated [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…where: = 1 − 0.0004 ≤ 500 ° 1.44 − 0.00145 500 ≤ ≤ 900 °0 ≥ 900 ° Further, the stress-strain relations for CBC-PET10 at elevated temperature (1 h heating in DF) are given in Equations (7) and (8), where:…”

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confidence: 99%

Study on the Compressive Behaviour of Sustainable Cement-Based Composites under One-Hour of Direct Flame Exposure

2020

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Fire is a significant threat to human life and civil infrastructures. Builders and architects are hankering for safer and sustainable alternatives of concrete that do not compromise with their design intent or fire safety requirements. The aim of the present work is to improve the residual compressive performance of concrete in post-fire exposure by incorporating by-products from urban residues. Based on sustainability and circular economy motivations, the attention is focused on rubber tire fly ash, aged brick powder, and plastic (PET) bottle residuals used as partial sand replacement. The selected by-products from urban residues are used for the preparation of Cement-Based Composites (CBCs) in two different proportions (10% and 15%). Thermal CBC behaviour is thus investigated under realistic fire scenarios (i.e., Direct Flame (DF) for 1 h), by following the International Organization for Standardization (ISO) 834 standard provisions, but necessarily resulting in nonuniform thermal exposure for the cubic specimens. The actual thermal exposure is further explored with a Finite Element (FE) model, giving evidence of thermal boundaries effects. The post-fire residual compressive strength of heated concrete and CBC samples is hence experimentally derived, and compared to unheated specimens in ambient conditions. From the experimental study, the enhanced post-fire performance of CBCs with PET bottle residual is generally found superior to other CBCs or concrete. The structure–property relation is also established, with the support of Scanning Electron Microscopy (SEM) micrographs. Based on existing empirical models of literature for the prediction of the compressive or residual compressive strength of standard concrete, newly developed empirical relations for both concrete and CBCs are assessed.

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Assessing concrete strength in fire-damaged structures

Cited by 51 publications

References 25 publications

Applicability of the 500°C isotherm method in determining the strength of reinforced concrete beams after fire

Applicability of the 500°C isotherm method in determining the strength of reinforced concrete beams after fire

Properties of quenched and self-tempered reinforcing steel subjected to high temperature and different cooling conditions

Study on the Compressive Behaviour of Sustainable Cement-Based Composites under One-Hour of Direct Flame Exposure

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