On the Experimental Analysis of Temperature Influence on Stiffness of Reinforced Concrete Beams

Kowalski, Robert; Głowacki, Michał; Abramowicz, M.

doi:10.1260/2040-2317.6.1.49

Cited by 7 publications

(9 citation statements)

References 7 publications

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“…Obtained results show that deflections obtained from current investigation for beams reinforced with FRP bars were much smaller than the results received for similar beams reinforced with steel bars in other studies [13,32]. In addition, the behavior of FRP-RC beams was quite uncharacteristic when subjected to elevated temperature, as well as during the cooling phase.…”

Section: Discussioncontrasting

confidence: 59%

“…In addition, it can also be seen that the maximum temperatures measured at the bottom edge were approximately 20% lower (at the last point) than the applied temperatures. The sample beam B2Ø14 from Set 1 showed a time-vertical deflection relationship more similar to a typical one for steel reinforced concrete beams [13,32]; the deflections were only increasing. Despite the larger initial deflections for beam samples B2Ø14, H2Ø14 and N2Ø14, the increase of deflections during fire exposure started to be twice lower than in the case of analogous beams with steel reinforcement.…”

Section: Resultsmentioning

confidence: 62%

“…Fire ratings for buildings refer to the amount of time a structure can be exposed to fire before the structure collapses. The most relevant property of FRP bars is not its flammability or its reaction to fire, but rather its ability to continue to sustain loads in an environment of rapidly rising temperature [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars

Protchenko

Szmigiera

2020

Materials

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One of the main concerns of experimental and numerical investigations regarding the behavior of fiber-reinforced polymer reinforced concrete (FRP-RC) members is their fire resistance to elevated temperatures and structural performance at and after fire exposure. However, the data currently available on the behavior of fiber-reinforced polymer (FRP) reinforced members related to elevated temperatures are scarce, specifically relating to the strength capacity of beams after being subjected to elevated temperatures. This paper investigates the residual strength capacity of beams strengthened internally with various (FRP) reinforcement types after being subjected to high temperatures, reflecting the conditions of a fire. The testing was made for concrete beams reinforced with three different types of FRP bars: (i) basalt-FRP (BFRP), (ii) hybrid FRP with carbon and basalt fibers (HFRP) and (iii) nano-hybrid FRP (nHFRP), with modification of the epoxy matrix of the rebar. Tested beams were first loaded at 50% of their ultimate strength capacity, then unloaded before being heated in a furnace and allowed to cool, and finally reloaded flexurally until failure. The results show an atypical behavior observed for HFRP bars and nHFRP bars reinforced beams, where after a certain temperature threshold the deflection began to decrease. The authors suggest that this phenomenon is connected with the thermal expansion coefficient of the carbon fibers present in HFRP and nHFRP bars and therefore creep can appear in those fibers, which causes an effect of “prestressing” of the beams.

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Section: Discussioncontrasting

confidence: 59%

Section: Resultsmentioning

confidence: 62%

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Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars

Protchenko

Szmigiera

2020

Materials

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“…In this case only the tensile zone of the element (reinforcement) in the span region and the compressed zone in the support are heated. Stiffness of a cross-section with heated tensile zone decreases much faster than in a cross-section with heated compressed zone (EN 1992(EN -1-2 2004Kowalski 2008;Kowalski et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

Premature destruction of two-span RC beams exposed to high temperature caused by a redistribution of shear forces

Kowalski

Głowacki

Abramowicz

2016

Journal of Civil Engineering and Management

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When multi-span RC elements are exposed to fire one usually observes a yielding of span cross-sections while a safety reserve of support cross-sections is still significant. Due to this phenomenon a redistribution of bending moments occurs and the values of sagging moment in span cross-sections decrease while the values of hogging moment in support cross-sections increase. This paper shows the results of tests conducted on two-span RC beams in a situation when only one span has been exposed to high temperature from the bottom. The beams were 12×16 cm in their cross-section. The length of the span was 165 cm. The load has been applied by two forces put on each span. The beams were made of C25/30 concrete with siliceous aggregate. As a result of significant stiffness decrease of the heated span, redistribution of shear forces and bending moment occurs. Due to this redistribution the tested beams were prematurely damaged due to exhaust of the shear load bearing capacity in the middle part of the beam span where there was no transverse reinforcement.

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“…Therefore, it is necessary to model the change in stiffness of various parts (sections) of the structure. In cross sections where the tensile zone is exposed to fire, stiffness decrease is governed by the strain (elongation) of reinforcing bars …”

Section: Introductionmentioning

confidence: 99%

Experimental approach to strength reduction and elongation of self‐tempered reinforcing bars tensioned at a steady and an increasing temperature

Kowalski

Kisieliński

2018

Structural Concrete

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This paper describes experiments performed on specimens of reinforcing bars 10, 12, and 16 mm in diameter. The bars were made of 500 MPa steel produced with Tempcore technology and were subject to simultaneous action of high temperature and tension. The experiments were performed both at a constant temperature of 100, 200, 300, 400, 500, and 600°C and in an increasing temperature and constant load corresponding to 0, 30, 45, 60, or 75% of steel yield strength at a room temperature. The analysis of the obtained results is focused on the reduction of steel strength and on the bar elongation due to high temperature. In the former case, different failure criteria were considered, which corresponded to the elongation of 0.2%, the elongation of 2% or the bar failure. The experimental results were compared with Eurocode 1992‐1‐2 models for the bar elongation below and over 2% and against results of similar test reported in the literature. In the study of bar elongation, different components of total elongation, which can be measured during a constant and an increasing temperature test, are described and compared with each other and Eurocode 1992‐1‐2 model.

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On the Experimental Analysis of Temperature Influence on Stiffness of Reinforced Concrete Beams

Cited by 7 publications

References 7 publications

Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars

Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars

Premature destruction of two-span RC beams exposed to high temperature caused by a redistribution of shear forces

Experimental approach to strength reduction and elongation of self‐tempered reinforcing bars tensioned at a steady and an increasing temperature

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