Plate Element Stress - Mx_My vs Global Moment - Bentley_ STAAD Products - Eng-Tips
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Home > Forums > Engineering Computer Programs > Engineering Programs > Bentley: STAAD products Forum Plate Element Stress Mx/My vs Global Moment thread750252946 Share I'm new to using STAAD for plate element design. I am trying to design a mat foundation using plate elements. In postprocessing, there are Mx and My moments as well as 'Global Moment' as options for the stress types. The Mx and My can be used to determine the appropriate rebar needed to resist the moments in thier respective directions for the plate element. But where does the gloabl moment come into play? At first I thought that it was a resultant moment, but the Mxy is the resultant moment leading to torsion in the plate element. Any clarification would be greatly appreciated. Don't know if it will help, but I am attaching screen clips for Mx, My, and Global Moment postprocessing stresses. Mx Local Moment http ://files.e ngineering .com/getfi le.aspx?fo lder=ee582 b7d9cbc4 6e38653f 0628fa0633 9&file =Mx_Local_ Moment.bmp My Local Moment http ://files.e ngineering .com/getfi le.aspx?fo lder=d9734 8c58a004 5e5893d2 fc11e5fc7a 1&file =My_Local_ Moment.bmp Global Moment ht tp://files .engineeri ng.com/get file.aspx? folder=28d 461dbef38 40f2b435 977e78be0 8a5&fi le=Global_ Moment.bmp Thanks Hi! Global moment should have the same answer with the local Mx and My. I think global moment is convenient when the plates are divided triangularly. Actually, global moments are not quite the same as the Mx and My. This is because of the effect of the Mxy moment as you have mentioned. Refer to the WoodArmer method of combining plate moments together to get design moments. That will give true design moments in the Mx and My local directions. See this thread for more detail: http://www.engtips.com/viewthread.cfm?qid=24256 Josh PS Why am I (a RISA guy) answering questions on STAAD's forum? Thanks for the information on the WoodArmer method. That should help out a lot. As for you question Josh, from a STAAD guy to a RISA guy, maybe this is the first step to program compatibility. LOL. Thanks again.
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Transcript of Plate Element Stress - Mx_My vs Global Moment - Bentley_ STAAD Products - Eng-Tips
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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.
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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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