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Article
Publication date: 6 April 2021

Kun Liu, Wei Chen, Jihong Ye, Jian Jiang, Wenwen Chen and Mingyue Zhao

Most previous thermal-mechanical modeling of cold-formed steel (CFS) walls did not consider the failure of screwed connections under fire conditions because of the limited…

Abstract

Purpose

Most previous thermal-mechanical modeling of cold-formed steel (CFS) walls did not consider the failure of screwed connections under fire conditions because of the limited data of such connections at elevated temperatures.

Design/methodology/approach

In this study, 285 steady-state tests are conducted on CFS screwed connections with single-layer gypsum plasterboard (GPB) and Bolivian magnesium board (BMB) sheathing at ambient and elevated temperatures. The failure of these connections is described as the breaking of the loaded sheathing edge.

Findings

For the BMB sheathing screwed connections, hydrochloric acid gas is generated and released above 300°C, and the shear strength becomes much less than that of the GPB sheathing screwed connection above 370°C. Hence, BMB may not be suitable for use as the face-layer sheathing of CFS walls but is still recommended to replace GPB as the base-layer sheathing. The major influencing parameters on the shear strength of screwed connections are identified as the type of sheathing material and the loaded sheathing edge distance.

Originality/value

Based on the previous and present test results, a unified expression for the residual shear strength of screwed connections with GPB and BMB is proposed at ambient and elevated temperatures with acceptable accuracy. It can be used as the basic input parameter of the numerical simulation of the CFS structures under fire conditions.

Details

Journal of Structural Fire Engineering, vol. 12 no. 2
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 7 December 2021

Sachin Vijaya Kumar and N. Suresh

The Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat…

Abstract

Purpose

The Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat developing from accidental fires and other industrial processes. In both of the scenarios, the RC element is exposed to elevated temperatures. However, the primary differences between the fire and processed temperatures are the rate of temperature increase, mode of exposure and exposure durations. In order to determine the effect of two heating modalities, RC beams were exposed to processed temperatures with slow heating rates and fire with fast heating rates.

Design/methodology/approach

In the present study, RC beam specimens were exposed to 200 °C, to 800 °C temperature at 200 °C intervals for 2 h' duration by adopting two heating modes; Fire and processed temperatures. An electrical furnace with low-temperature increment and a fire furnace with standard time-temperature increment is adapted to expose the RC elements to elevated temperatures.

Findings

It is observed from test results that, the reduction in load-carrying capacity, first crack load, and thermal crack widths of RC beams exposed to 200 °C, and 600 °C temperature at fire is significantly high from the RC beams exposed to the processed temperature having the same maximum temperature. As the exposure temperature increases to 800 °C, the performance of RC beams at all heating modes becomes approximately equal.

Originality/value

In this work, residual performance, and failure modes of RC beams exposed to elevated temperatures were achieved through two different heating modes are presented.

Details

Journal of Structural Fire Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 3 September 2019

Mariyana Aida Ab Kadir, Mohammad Iqbal Khiyon, Abdul Rahman Mohd. Sam, Ahmad Beng Hong Kueh, Nor Hasanah Abdul Shukor Lim, Muhammad Najmi Mohamad Ali Mastor, Nurizaty Zuhan and Roslli Noor Mohamed

The purpose of this paper is to examine the mechanical properties, material composition of spent garnet as a sand replacement in high-strength concrete at room and elevated

Abstract

Purpose

The purpose of this paper is to examine the mechanical properties, material composition of spent garnet as a sand replacement in high-strength concrete at room and elevated temperatures. Bonding of the concrete containing spent garnet and reinforcing rebar is investigated. Moreover, the optimum thickness of concrete cover subjected to elevated temperatures is investigated.

Design/methodology/approach

First, the plain spent garnet was physically, chemically and thermally studied. Then, a series of concrete specimens with 0, 20, 40, 60, 80 and 100 per cent of spent garnet were prepared to determine the optimum percentage of spent garnet. Finally, the physical and mechanical behaviours of concrete specimens and effects of cover thickness on steel rebar when subjected to elevated temperature of 200°C, 400°C, 600°C and 800°C for 1 h were studied. It was observed that spent garnet was thermally stable compared to river sand.

Findings

Mechanical properties were found to be optimal for concrete with 40% spent garnet replacement. Physically, spent garnet concrete changed colour to brown at 400°C, and to whitish grey at 600°C. The residual compressive strength of spent garnet concrete was also found slightly higher than that for control specimens. At various high temperatures, the reduction in ultimate tensile stress for steel bar inside concrete cover of 30 mm was the lowest compared to that of 20 mm.

Research limitations/implications

Spalling effect it not considered in this study.

Practical implications

The optimum concrete cover is important issues in reinforced concrete design. This can be used as a guideline by structural designers when using a different type of concrete material in the construction.

Social implications

Utilization of the waste spent garnet reduces usage of natural aggregates in concrete production and enhances its performance at elevated temperatures. Natural aggregates are normally taken from sand and rock. The new innovation in concrete perhaps can produce light concrete, reduce the cost of concrete production and at the same time also mitigates environmental problems affect from waste material such as minimizing disposal area.

Originality/value

Utilization of spent garnet in ordinary Portland cement (OPC) concrete at high temperature is a new innovation. It shows that the concrete cover of the concrete element reduced as compared to the OPC concrete. Reduce in weight concrete however the strength of concrete is similar to conventional concrete. This study at elevated temperature has never been performed by any previous researcher.

Details

Journal of Structural Fire Engineering, vol. 10 no. 4
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 21 March 2022

Jason Martinez and Ann Jeffers

A methodology for producing an elevated-temperature tension stiffening model is presented.

Abstract

Purpose

A methodology for producing an elevated-temperature tension stiffening model is presented.

Design/methodology/approach

The energy-based stress–strain model of plain concrete developed by Bažant and Oh (1983) was extended to the elevated-temperature domain by developing an analytical formulation for the temperature-dependence of the fracture energy Gf. Then, an elevated-temperature tension stiffening model was developed based on the modification of the proposed elevated-temperature tension softening model.

Findings

The proposed tension stiffening model can be used to predict the response of composite floor slabs exposed to fire with great accuracy, provided that the global parameters TS and Kres are adequately calibrated against global structural response data.

Originality/value

In a finite element analysis of reinforced concrete, a tension stiffening model is required as input for concrete to account for actions such as bond slip and tension stiffening. However, an elevated-temperature tension stiffening model does not exist in the research literature. An approach for developing an elevated-temperature tension stiffening model is presented.

Details

Journal of Structural Fire Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 14 July 2021

Sachin B.P. and N. Suresh

The purpose of the paper is to study the effect of elevated temperature on load carrying capacity of reinforced self compacting concrete beams and the performance of…

Abstract

Purpose

The purpose of the paper is to study the effect of elevated temperature on load carrying capacity of reinforced self compacting concrete beams and the performance of deteriorated beams after retrofitting by GFRP sheets. The reinforced beams which were exposed to sustained elevated temperature and tested for flexural load-carrying capacity. Further deteriorated beams (exposed from 500°C to 800°C) were re-strengthened by adopting retrofitting with GFRP sheets.

Design/methodology/approach

The investigation includes the concrete specimens, i.e. cubes of 150 mm, cylinders of size 150 mm dia with 300 mm height and beams of 150 × 150 × 1,100 mm, reinforced with minimum tension reinforcement according to IS 456–2000. The specimens were subjected to elevated temperature from 300°C to 800°C with an interval of 100°C for 2 h. The residual compressive strength, modulus of elasticity, load at first crack of beams and load-carrying capacity of beams for 5-mm deflection were measured before and after retrofitting.

Findings

The result shows that there is a gain in residual compressive strength at 300°C and beyond which it decreases. The modulus of elasticity, load at first crack and load-carrying capacity of beams reduces continuously with an increase in temperature. The decrease in load-carrying capacity of beams is observed from 27.55% and up to 38.77% between the temperature range of 500°C–800°C and after the retrofitting of distressed beams, the load carrying capacity increases up to 24.48%.

Originality/value

Better performance was observed with retrofitting by GFRP sheets when the specimens were distressed due to elevated temperatures.

Details

Journal of Structural Fire Engineering, vol. 12 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 20 September 2019

Subhash Yaragal, Chethan Kumar B. and Manoj Uddavolu Abhinav

To reduce environmental impact caused by excessive use of ordinary Portland cement (OPC) and to mitigate scarcity of base materials such as natural coarse aggregate (NCA)…

Abstract

Purpose

To reduce environmental impact caused by excessive use of ordinary Portland cement (OPC) and to mitigate scarcity of base materials such as natural coarse aggregate (NCA), industrial by-products can be carefully used as alternatives to OPC and NCA, in production of concrete. This paper aims to describe the performance of using ground granulated blast furnace slag (GGBS), fly ash (FA) as a complete replacement to OPC and ferrochrome slag (FCS) as replacement to NCA in production of novel FCS based alkali activated slag/fly ash concretes (AASFC) and evaluate their performance at elevated temperatures.

Design/methodology/approach

Two control factors with three levels each i.e. FA (0, 25 and 50 per cent by weight) and FCS (0, 50 and 100 per cent by volume) as a GGBS and NCA replacement, respectively, were adopted in AASFC mixtures. Further, AASFC mixture specimens were subjected to different levels of elevated temperature, i.e. 200°C, 400°C, 600°C and 800°C. Compressive strength and residual compressive strength were considered as responses. Three different optimization techniques i.e. gray relational analysis, technique for order preference by similarity to ideal solution and Desirability function approach were used to optimize AASFC mixtures subjected to elevated temperatures.

Findings

As FA replacement increases in FCS based AASFC mixtures, workability increases and compressive strength decreases. The introduction of FCS as replacement to NCA in AASFC mixture did not show any significant change in compressive strength under ambient condition. AASFC produced with 75 per cent GGBS, 25 per cent FA and 100 per cent FCS was found to have excellent elevated temperature enduring properties among all other AASFC mixtures studied.

Originality/value

Although several studies are available on using GGBS, FA and FCS in production of OPC-based concretes, present study reports the performance of novel FCS based AASFC mixtures subjected to elevated temperatures. Further, GGBS, FA and FCS used in the present investigation significantly reduces CO2 emission and environmental degradation associated with OPC production and NCA extraction, respectively.

Article
Publication date: 28 February 2019

Hala Mohamed Elkady, Ahmed M. Yasien, Mohamed S. Elfeky and Mohamed E. Serag

This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond…

Abstract

Purpose

This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond strengths is studied. Pre- and post-exposure to elevated temperature ranges of 200 to 600°C is examined. A range covered by three percentages of 1.5, 3 and 4.5 per cent nano silica (NS) in concrete mixes is tested.

Design/methodology/approach

Pre-exposure mechanical tests (normal conditions – room temperature), using 3 per cent NS in the concrete mix, led to the highest increase in both compressive and bond strengths (43 per cent and 38.5 per cent, respectively), compared to the control mix without NS (based on 28-day results). It is worth noticing that adding NS to the concrete mixes does not have a significant effect on improving early-age strength. Besides, permeability tests are performed on NSC with different NS ratios. NS improved the concrete permeability for all tested percentages of NS. The maximum reduction is accompanied by the maximum percentage used (4.5 per cent NS in the NSC mix), reducing permeability to half the value of the concrete mix without NS. As for post-exposure to elevated-temperature mechanical tests, NSC with 1.5 per cent NS exhibited the lowest loss in strength owing to indirect heat exposure of 600°C; the residual compressive and bond strengths are 73 per cent and 35 per cent, respectively.

Findings

The dispersion technique of NS has a key role in NSC-distinguished mechanical performance with NSC having lower NS percentages. NS significantly improved bond strength. NS has a remarkable effect on elevated temperature endurance. The bond strength of NSC exposed to elevated temperatures suffered faster deterioration than compressive strength of the exposed NSC.

Research limitations/implications

A special scale factor needs to be investigated for the NSC.

Originality/value

Although a lot of effort is placed in evaluating the benefits of using nano materials in structural concrete, this paper presents one of the first outcomes of the thermal effects on concrete mixes with NS as a partial cement replacement.

Details

Journal of Structural Fire Engineering, vol. 10 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 14 February 2022

Virendra Kumar and Rajesh Kumar Paswan

This paper attempted to study the alkali-activated (AA) binder consisting of 94% of ground granulated blast furnace slag (GGBFS) and 6% of blended powder of alkali metal…

Abstract

Purpose

This paper attempted to study the alkali-activated (AA) binder consisting of 94% of ground granulated blast furnace slag (GGBFS) and 6% of blended powder of alkali metal hydroxide and metal sulfate, which acted as an activator.

Design/methodology/approach

Several concrete specimens (cubes, cylinders and prisms), which were casted using AA binders, were further tested for mechanical properties after exposure to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C. Additionally, to understand the structural behavior in uniaxial compressive load, reinforced concrete short columns were cast, cured and tested at ambient temperature as well as after exposure to 300 °C, 600 °C and 900 °C, to know the residual strength after exposure to elevated temperature.

Findings

The findings for the residual strength of alkali-activated slag binder concrete (AASBC) indicated a substantial agreement with the results obtained for the residual strength of Portland slag cement (PSC) concrete, thereby showing the effectiveness of binder when used as a replacement of cement.

Originality/value

The study clearly indicates that the binder developed is an effective approach for the 100% replacement of cement in the concrete.

Details

Journal of Structural Fire Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 20 January 2022

N. Suresh, Vadiraj Rao and B.S. Akshay

The purpose of the study is to evaluate the suitability of post-fire curing for normal and Recycled Aggregate Concretes (RAC) with and without fibres.

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Abstract

Purpose

The purpose of the study is to evaluate the suitability of post-fire curing for normal and Recycled Aggregate Concretes (RAC) with and without fibres.

Design/methodology/approach

The study includes the testing of RAC specimens, i.e. 150 mm cubes and cylinders with 300 mm length and 150 mm diameter with hybrid fibres (0.15% polypropylene fibres + 0.35% steel fibres) along with fly ash. The specimens were exposed to elevated temperatures between 400 to 700°C with 100°C intervals for 2 h of duration and the post-fire exposed samples were further subjected to water curing for a period of 7 days. The compressive strength, split tensile strength and Rebound Hammer Number (RHN) were measured at room temperature, after exposure to elevated temperatures and post-fire curing.

Findings

The result shows that the compressive strength reduces by a maximum of 61.25% for 700°C and maximum retain in strength, i.e. 71.2% (in comparison to specimens kept at room temperature) is observed for 600°C post-fire cured specimens. The split tensile strength reduces by more than half for 500°C and above temperatures, whereas 400°C specimens exhibits a significant regain in strength after post-fire curing. To validate the results of compressive strength, the Rebound Hammer test has been conducted. The RHN value decreases by 41.3% for 700°C specimens and the effectiveness of post-fire curing is observed to be considerable up to 500°C.

Practical implications

The conclusions from the study can be used in assessing the extent of damage and to check the suitability of post-fire curing in further continuing the utilisation of a fire damaged structure.

Social implications

Utilisation of secondary materials like recycled aggregates and fly ash can be made in the production of concrete.

Originality/value

Specimens with fibres performed better when compared to specimens without fibres and post-fire curing is found to be effective up to 500°C.

Details

Journal of Structural Fire Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 4 August 2017

Vadims Goremikins, Lukas Blesak, Josef Novak and Frantisek Wald

This work aims to present an experimental study of steel fibre-reinforced concrete (SFRC) subjected to high temperature, especially focusing on residual behaviour.

Abstract

Purpose

This work aims to present an experimental study of steel fibre-reinforced concrete (SFRC) subjected to high temperature, especially focusing on residual behaviour.

Design/methodology/approach

Compressive strength and split tensile strength of SFRC cubes and ultimate bending strength of prisms were evaluated under ambient and elevated temperatures. The specimens were heated by ceramic heaters and then repacked for testing.

Findings

The results showed that a compressive strength of SFRC is reduced by 38 and 66 per cent, tensile strength is reduced by 25 and 59 per cent and ultimate bending force is reduced by 33 and 56 per cent in case of 400°C and 600°C, respectively, comparing with ambient temperature.

Originality value

The developed testing procedure could be used for determination of material properties of SFRC under elevated temperatures.

Details

Journal of Structural Fire Engineering, vol. 8 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

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