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Intro to XTRACT program

1. UseXtract onserver(locatedinTRCfolder)

2. Downloadtrialversionfrom

http://www.imbsen.com/softwareXTRACT.html

SECTION ANALYSIS USING XTRACT (A QUICK INTRO)

Needtoinputinfoinall5

linesinordertoproceed.

Enterthenameofthe

section,usuallystartfroma

templateorapreviously

definedsectionandselect

preferredunitssystem.

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SECTION TYPE AND TRANSVERSE REINFORCEMENT

Selectsectiontype

(e.g.circularorrectangular

columns,rectangularbeams,

Tbeams,rectangularwalls

andenclosedcomposite)

Selecttransverse

reinforcementlayout.

Specifytransversereinforcementbarsizeand

spacing(s).(Shown:hoopsandcrossties#4@3)

Ifallowedto,theprogramwillusethisinfoto

calculateeffectiveconfinementofthecore.

Usuallywe

input

the

confinement

parameters

(i.e.effectiveconfiningstresses)byhandusing

theprocedurespresentedintheCourse.

SECTION DIMENSIONS AND LONGITUDINAL REINF.

Specifydimensionsandclear

cover.

Specifyamountoflongitudinalreinforcement

andbarsize(dblong).(Shown:8#8)

Checkthesummaryofthesectionpropertiesand

thelongitudinalreinforcementratio(totalsteel

areadividedbygrosscolumnarea)

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MATERIALS DEFINITION: UNCONFINED CONCRETE

Addnewunconfinedcover

concretematerial.

Cfc(largecolumnnominalconcrete

compressivestrengthwithreduction

factorC=0.85.

For

beams

use

fc)

fr=7.5(fc)1/2 (oraround10%fc)

Notethesignconvention!

Thisisjustareference

valueusedbythesolver

algorithmtodefineaFirst

Yield

Criterion

.

Usually

set

to70%o.

Whendealingwith

confinedsections,settoa

verylargenumber(e.g.

equal1)toavoidthesolver

algorithmfromreachinga

falselimitingvalue.This

willnotgiveunrealistic

highercapacitiesbecause

thestrengthissetto zero

forsuchlargestrains(i.e.

PostCrushingStess=0)

cu=0.004(ACIvaluetypicallytakenas0.003)

sp=0.004(othervaluetypicallyusedis0.006)

cu=0.004sp=0.006

Ec=57(fc)1/2 (fcinpsi)

Alternative

MATERIALS DEFINITION: CONFINED CONCRETE

Addnewconfinedcoreconcrete

material.

CAUTION!!Unconfinedconcrete

properties!!!

Sameasbeforesetto

70%o.

ccu(confinedconcreteultimatestrain)

fcc(confinedconcretestrength)

Ec=57(fc)1/2 (fcinpsi)

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MATERIALS DEFINITION: REBAR STEEL A706-G60

Addnewlongitudinalsteel

stressstrainrelation.

(perFigure2.3.2andTable2.3.2in

theReader)

MESH SIZE & SECTION CREATION

ClickHeretoBegin!

Herethesizeofthe

discretizationmeshcan

beadjusted(i.e.define

thesizeofthetriangles

intowhichthesection

isdivided).Ingeneral

trytoavoidmakingit

muchsmallerthanthe

defaultvaluebecause

itusuallyshowsan

errorthathastodue

withmemory

management

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EXERCISE 1: INCREMENTAL AXIAL LOADING

GotoLoading/Moment

Curvature(Crtl+T)

(+)forcompressionand()fortension

incrementalloading

Theobjectiveofthisexampleistoshowtheresponseofacolumnwithconfinedcoreunderincremental

axialloading(similartoProblem5 Homework3)

Initialconditionspriortothe

incrementalaxialload

analysis.Forthisexamplewe

willstartfromzero.(Usually,

wesetanaxialloadfor

columnsorwallsbeforedoing

incrementalmomentloading)

Herewesetwhichtypeof

incrementaldemandwewill

imposeto

the

section

Giveanametotheloading

pattern

EXERCISE 1: INCREMENTAL AXIAL LOADING

Hitrun,

then

check

the

projectmanagerandexplore

theoutputsoftheanalysis

Thefailuremechanismisgovernedbythematerialthatfirst

reachestheultimatestrain.Inthisexampleitcouldbe

eithertheconfinedconcretereachingcu =0.029orthe

steelreachingsu =0.14.

Herewecananalyzewhatisthestressstrainrelationof

eachmaterialateverystageoftheresponse.

Givesasummaryoftheresponseofthesection(Py,Pu,

ductilitycapacityu/y,etc.)

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EXERCISE 2: MOMENT-CURVATURE ANALYSIS

GotoLoading/Moment

Curvature(Crtl+T)

()forcompressionoftheextremetopfiber

Theobjectiveofthisexampleistoshowthemomentcurvature(M)responseofacolumnwithanappliedaxialload

Applyatypicalaxialloadof

10%Agfc.(+)forcompression

Willapplymoment

incrementsuntileitherthe

confinedconcreteorthe

longitudinalsteelreachthe

limitingstrain(cu=0.029orsu=0.14)

Giveanametotheloading

pattern

Hitrun,

then

check

the

projectmanagerandexplore

theoutputsoftheanalysis

EXERCISE 2: MOMENT-CURVATURE ANALYSIS

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Step6intheM

relation

Stateofthebottomsteel

@Step6

Stateofthesection

@Step6:

bottom

steel

yielded,neutralaxis

abovemiddepth steel

Stateofthebottom

steel@

Failure

Stateoftheextremefiber

ofconfinedconcretein

compression@Step6

Stateoftheconcrete

@Failure

.Thisiswhy

theanalysisended!!!

EXERCISE 2: MOMENT-CURVATURE ANALYSIS

EXERCISE 2: MOMENT-CURVATURE ANALYSIS

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EXERCISE 3: PM-INTERACTION DIAGRAM

GotoLoading/PMInteraction

(Crtl+T)

Herethereductionfactorgivenbythe

buildingcodescanbeapplied.

Theobjectiveofthisexampleistoshowhowtoconstructionanaxialloadmoment(PM)interaction

diagram.

Onlyhalfdiagramisrequired

becausethesectionis

symmetricaboutthehorizontal

andverticalaxes.

0deg willapplythemoment

incrementsaroundtheXaxis

Giveanametotheloading

pattern

Defaultvalueswillgivea

smoothandaccuratecurve

EXERCISE 3: PM-INTERACTION DIAGRAM

Hitrun,thenchecktheprojectmanagerandexplore

theoutputsoftheanalysis