Post on 26-Sep-2015
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5/11/2015 PlateElementStressMx/MyvsGlobalMomentBentley:STAADproductsEngTips
http://www.engtips.com/viewthread.cfm?qid=252946 1/2
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PlateElementStressMx/MyvsGlobalMomentthread750252946
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I'mnewtousingSTAADforplateelementdesign.Iamtryingtodesignamatfoundationusingplateelements.Inpostprocessing,thereareMxandMymomentsaswellas'GlobalMoment'asoptionsforthestresstypes.
TheMxandMycanbeusedtodeterminetheappropriaterebarneededtoresistthemomentsinthierrespectivedirectionsfortheplateelement.Butwheredoesthegloablmomentcomeintoplay?AtfirstIthoughtthatitwasaresultantmoment,buttheMxyistheresultantmomentleadingtotorsionintheplateelement.Anyclarificationwouldbegreatlyappreciated.
Don'tknowifitwillhelp,butIamattachingscreenclipsforMx,My,andGlobalMomentpostprocessingstresses.
MxLocalMomenthttp://files.engineering.com/getfile.aspx?folder=ee582b7d9cbc46e38653f0628fa06339&file=Mx_Local_Moment.bmp
MyLocalMomenthttp://files.engineering.com/getfile.aspx?folder=d97348c58a0045e5893d2fc11e5fc7a1&file=My_Local_Moment.bmp
GlobalMomenthttp://files.engineering.com/getfile.aspx?folder=28d461dbef3840f2b435977e78be08a5&file=Global_Moment.bmp
Thanks
Hi!
GlobalmomentshouldhavethesameanswerwiththelocalMxandMy.Ithinkglobalmomentisconvenientwhentheplatesaredividedtriangularly.
Actually,globalmomentsarenotquitethesameastheMxandMy.ThisisbecauseoftheeffectoftheMxymomentasyouhavementioned.
RefertotheWoodArmermethodofcombiningplatemomentstogethertogetdesignmoments.ThatwillgivetruedesignmomentsintheMxandMylocaldirections.
Seethisthreadformoredetail:http://www.engtips.com/viewthread.cfm?qid=24256
Josh
PSWhyamI(aRISAguy)answeringquestionsonSTAAD'sforum?
ThanksfortheinformationontheWoodArmermethod.Thatshouldhelpoutalot.
AsforyouquestionJosh,fromaSTAADguytoaRISAguy,maybethisisthefirststeptoprogramcompatibility.LOL.
Thanksagain.
5/11/2015 PlateElementStressMx/MyvsGlobalMomentBentley:STAADproductsEngTips
http://www.engtips.com/viewthread.cfm?qid=252946 2/2
Iknowthisisalittleafterthefact,butbetterlatethannever...
WhenreferingtoMxandMyforplatemoments,besuretokeepthenomenclaturestraight.Mxdoesnotmeanmomentabouttheplatelocalxaxis.ItactuallymeansmomentontheXface,wherethexfaceistheedgethatthelocalxaxis"pokesoutof".ItturnsoutthatMxisactuallythemomentABOUTtheplatelocalyaxis,whichcanbealittleconfusing.Butitmayhelptothinkofitthisway...Mxisthemomentyouwanttousetodesigntherebarthatrunsparalleltotheplatelocalxaxis.
STAAD
SodoyoumeantosaythatusingtheWoodArmermethodasJoshPlumreferencedisincorrect?
WoodArmerisadesignmethod.
Mx,My,Mxy,andGlobalMomentsareanalysisresults.
Let'ssaywehaveameshofquadplatesthatisorientedasfollows:
platelocalxaxespointinthepositiveglobalXdirection
platelocalyaxespointinthenegativeglobalZdirection
platelocalzaxespointinthepositiveglobalYdirection
ThenMxisthemomentonthexfaceoftheplate.ThisismomentABOUTtheplatelocalyaxis,whichisthesameasdescribingmomentABOUTtheglobalZaxisfortheorientationdescribedabove.NowamomentABOUTtheglobalZaxisproducestensileandcompressivestressesintheglobalXdirection.Soifyouweretoreviewtheglobalmomentsforthesameplate,lookinthecolumnsthatrelatetotheGlobalXstressdirection,usethecolumnthatiscoordinatedwithourplate"top"orientationofY(+ve),youwillreadtheexactsamemomentaswasreportedforMxforthesameplate.
Hopethathelps.
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