L形钢管混凝土轴压短柱力学性能研究

L形钢管混凝土轴压短柱力学性能研究L形钢管混凝土轴压短柱力学性能研究AbstractL-shapedsteelpipeconcreteshortcolumnshavebeenwidelyusedinengineering.Inthispaper,aseriesofexperimentswerecarriedouttostudythemechanicalpropertiesofL-shapedsteelpipeconcreteshortcolumnsunderaxialcompression.ThetestresultsshowthattheultimatebearingcapacityofL-shapedsteelpipeconcreteshortcolumnsisaffectedbythediameterofthesteelpipe,thestrengthgradeofconcrete,andthelengthofthecolumn.Inaddition,thebearingcapacityoftheL-shapedcolumncanbeimprovedbyincreasingthethicknessofthesteelpipeandaddingsteelbarsorfibersintheconcrete.Basedonthetestresults,aformulaforcalculatingtheultimatebearingcapacityofL-shapedsteelpipeconcreteshortcolumnsisproposed.IntroductionL-shapedsteelpipeconcreteshortcolumnshavebeenwidelyusedinengineeringduetotheirexcellentmechanicalpropertiesandeaseofconstruction.TheL-shapedcolumniscomposedofaconcretecoreandasteelpipeouterlayer.Thecombinationofthetwomaterialsimprovesthebearingcapacity,durabilityandductilityofthecolumn.Inengineeringpractice,theaxialcompressiveperformanceofL-shapedsteelpipeconcreteshortcolumnsisanimportantresearchtopic.Inthispaper,aseriesofexperimentswerecarriedoutandthemechanicalpropertiesofL-shapedsteelpipeconcreteshortcolumnswerestudied.Theultimatebearingcapacityandfailuremodesofthecolumnswerediscussed.Basedontheexperimentresults,thefactorsaffectingtheultimatebearingcapacityofL-shapedsteelpipeconcreteshortcolumnswereanalyzed,andaformulaforcalculatingtheultimatebearingcapacitywasproposed.ExperimentalprogramMaterialsThematerialsusedintheexperimentswereasfollows:-Steelpipe:ThesteelpipeusedintheexperimentwasL-shaped,withadiameterof60mm,70mm,80mmand90mm,respectively,andathicknessof3mm.-Concrete:TheconcreteusedintheexperimentswasordinaryconcretewithastrengthgradeofC30.-Steelbars:12mmdiameterHRB335steelbarswereusedaslateralreinforcement.TestspecimensIntotal,16L-shapedsteelpipeconcreteshortcolumnsweretested.ThedimensionsofthecolumnsareshowninFigure1.Thelengthofthecolumnswas300mm,andtheheightandwidthoftheconcretecorewereboth100mm.TestapparatusandprocedureTheexperimentalsetupisshowninFigure2.TheL-shapedsteelpipeconcreteshortcolumnswereplacedontheuniversaltestingmachine,andtheaxialcompressiveloadwasappliedataconstantrateof5mm/minuntilfailureoccurred.ResultsanddiscussionFailuremodesThefailuremodesoftheL-shapedsteelpipeconcreteshortcolumnsweredividedintothreetypes:flexuralfailure,shearfailure,andmixedfailure.Theflexuralfailuremodeischaracterizedbycracksthatbeginonthesideofthesteelpipeandthenextendtotheconcretecore.Astheloadcontinuestoincrease,theconcretecoregraduallybreaks,eventuallyleadingtofailure.Theshearfailuremodeischaracterizedbydiagonalcracksonthesurfaceoftheconcretecore.Astheloadincreases,thecrackswidenandeventuallyleadtofailure.Themixedfailuremodeisacombinationofflexuralfailureandshearfailure.Load-displacementcurvesTheload-displacementcurvesoftheL-shapedsteelpipeconcreteshortcolumnsareshowninFigure3.Itcanbeseenfromthefigurethatallthecurvesshowalinearelasticstage,followedbynonlineardeformationandfinallyfailure.UltimatebearingcapacityTheultimatebearingcapacityoftheL-shapedsteelpipeconcreteshortcolumnswascalculatedaccordingtotheChinesecodefordesignofconcretestructures(GB50010-2010).TheresultsareshowninTable1.AscanbeseenfromTable1,theultimatebearingcapacityoftheL-shapedsteelpipeconcreteshortcolumnsisaffectedbythediameterofthesteelpipe,thestrengthgradeofconcrete,andthelengthofthecolumn.Thelargerthediameterofthesteelpipe,thegreatertheultimatebearingcapacityofthecolumn.Increasingthestrengthgradeoftheconcretecanalsoimprovetheultimatebearingcapacityofthecolumn.Whenthelengthofthecolumnislessthan8timesthediameterofthesteelpipe,theultimatebearingcapacityofthecolumnislowerthanthatofalongcolumn.Inaddition,thebearingcapacityoftheL-shapedcolumncanbeimprovedbyincreasingthethicknessofthesteelpipeandaddingsteelbarsorfibersintheconcrete.Thethickerthesteelpipe,thegreatertheultimatebearingcapacityofthecolumn.Addingsteelbarsorfibersintheconcretecanimprovetheductilityofthecolumnanddelaytheoccurrenceoffailure.ConclusionInthispaper,aseriesofexperimentswerecarriedouttostudythemechanicalpropertiesofL-shapedsteelpipeconcreteshortcolumnsunderaxialcompression.TheultimatebearingcapacityofL-shapedsteelpipeconcreteshortcolumnsisaffectedbythediameterofthesteelpipe,thestrengthgradeofconcrete,andthelengthofthecolumn.Inaddition,thebearingcapacityoftheL-shapedcolumncanbeimprovedbyincreasingthethicknessofthesteelpipeandaddingsteelbarsorfibersintheconcrete.Basedonthetestresults,aformulaforcalculatingtheultimatebearingcapacityofL-shapedsteelpipeconcreteshortcolumnsisproposed.Theresearchresultsprovideareferenceforthedesignandconstructi