An experimental approach to the estimation of stiffness changes in RC elements exposed to bending and high temperature
Michał Jan Głowacki , Robert Kowalski
AbstractThispaperpresentstheresultsoftestsforpossiblestiffnesschangesinbentreinforcedconcreteelementsexposedto 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.
|Journal series||Engineering Structures, ISSN 0141-0296, e-ISSN 1873-7323|
|Publication size in sheets||0.7|
|Keywords in English||RC beams, Load, High temperature, Fire, Deflection, Stiffness, Tests|
|Score||= 140.0, 24-06-2020, ArticleFromJournal|
|Publication indicators||= 0; = 0; : 2018 = 2.089; : 2018 = 3.084 (2) - 2018=3.345 (5)|
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