An experimental approach to the estimation of stiffness changes in RC elements exposed to bending and high temperature

Michał Jan Głowacki , Robert Kowalski

Abstract

Thispaperpresentstheresultsoftestsforpossiblestiffnesschangesinbentreinforcedconcreteelementsexposedto simultaneous action of load and high temperature. The above issue plays a critical role in the advancedanalysis of complex RC structures subjected to fire.Inordertoexaminethisissue,anexperimentalstudyof24full-sizeRCbeamswasperformed.Allbeamsweredividedinto8seriesaccordingto3factors:(1)thecross-sectionzoneexposedtohightemperature–tensionorcompressionzone,(2)reinforcementratio–0.44or1.13%,(3)loadlevelinreferencetoultimateloadcapacityatroomtemperature–50or70%.Thepurebendingpartofthebeamwasheated.Stiffnesschangesestimatedonthe basis of deflection measurement.The cross-section stiffness of the beam with the heated tension zone decreases rapidly at the initial heatingstage.A decrease of 60–80% in cross-section stiffness is observed at reinforcement temperature of 200–300 °C.Whenreinforcementtemperatureisabout500°C,thecross-sectionstiffnessmaybeonly10–15%ofitsvalueatroom temperature. It has also been found that the model recommended in Eurocode 1992-1-2 characterizingmechanical properties of tensile steel in high temperature maybe usedfor the adequateprediction of stiffnessdecrease in the cross-section with the heated tension zone.It can be assumed that during heating the stiffness of cross-sections with the heated compression zone willremainapproximatelyconstantforsometime.Itwillonlystarttodecreasewhenthestrainofconcreteexposedsimultaneously to load andhigh temperature begins to exceed itsfree thermal strain.This paper presents a simplified method to estimate the cross-section stiffness in bent reinforced concreteelements with the heated tension or compression zone.
Author Michał Jan Głowacki (FCE / ICE)
Michał Jan Głowacki,,
- The Institute of Civil Engineering
, Robert Kowalski (FCE / ICE)
Robert Kowalski,,
- The Institute of Civil Engineering
Journal seriesEngineering Structures, ISSN 0141-0296, e-ISSN 1873-7323
Issue year2020
Vol217
Pages1-15
Publication size in sheets0.7
Article number110720
Keywords in EnglishRC beams, Load, High temperature, Fire, Deflection, Stiffness, Tests
ASJC Classification2205 Civil and Structural Engineering
DOIDOI:10.1016/j.engstruct.2020.110720
URL https://www.sciencedirect.com/science/article/pii/S0141029619339264
Languageen angielski
File
1-s2.0-S0141029619339264-main.pdf 8.24 MB
Score (nominal)140
Score sourcejournalList
ScoreMinisterial score = 140.0, 24-06-2020, ArticleFromJournal
Publication indicators Scopus Citations = 0; WoS Citations = 0; Scopus SNIP (Source Normalised Impact per Paper): 2018 = 2.089; WoS Impact Factor: 2018 = 3.084 (2) - 2018=3.345 (5)
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