Mass Source

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Mass Source. Choose how to define the mass of the structure using either or both of the

following options: 

Element Self Mass and Additional Mass  option. This is the default. With this option,

mass is calculated from the following specifications: 

Mass density specified for materials materials..

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Mass specified for link for link properties. properties.

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 Additional mass assigned directly to the joints the joints..

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 Additional line line mass assigned to frame to frame or cable cable objects.  objects.

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 Additional area mass assigned to area area objects.  objects.

Specified Load Patterns  option. With this option, mass is calculated from a scaled

combination of load patterns see !efine Mass Multiplier for "oads, below#. The net load acting downward in the negati$e global % direction# on each element is di$ided by the acceleration due to gra$ity, in the current units, and is used for the mass in the three translational directions. &ee '!etailed Calculations' below. "oad patterns should generally represent weight, and should not contain self(e)uilibrating self(e)uilibrating loads, such as temperature and prestress. 

*f both options are selected, the total mass is the sum of the mass from each option. +e careful not to include load patterns containing self(weight when using the lement &elf Mass, or the mass may be double(counted.

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-esponse(spectrum and modal time(history load cases use the Mass &ource of their corresponding modal load case. ote: /. 0a$e you you considered considered 1ero 1ero li$e li$e load load for terrac terraces es for seismi seismic c load combos2 please check. 3. 4loor finishing load taken by you /.5 k6s).m# seems to b e slightly on lower side. *t depends upon the actual floor finishing material used. 7lease re$isit. 8. The base shear coefficient used by use is 5.59 while it is 5.5; for buildings with time period upto / se cond as per +C 35<. Also, the formula T=5.5>06s)rt!## T=5.5>06s)rt!## is preferable for buildings with infill wall. 7lease check.

3.

 Mass source is meant for auto-generation of seismic load in SAP2000. As per IS 1893-2002 and NN! 10"# $ou %a&e to consider dead load' speci(ed percentage of li&e load )%ile calculating seismic )eig%t of a *uilding. So# Mass source s%ould *e gi&en accordingl$. +or e,ample# )%ile gi&ing mass source from loads# factor s%ould *e 1 for eac% of t%e dead load items and 0.2" or 0." depending upon li&e load intensit$ for li&e load items. ne ma$ use separate li&e load for roof so t%at it ma$ not *e included in mass source since li&e load is to *e taen as /ero for roof as per codal pro&ision. As said a*o&e# *e sure of t%e meaning of eac% command *efore using t%em.oo Mass source is meant for auto-generation of seismic load in SAP2000. As per IS 1893-2002 and NN! 10"# $ou %a&e to consider dead load' speci(ed percentage of li&e load )%ile calculating seismic )eig%t of  a *uilding. So# Mass source s%ould *e gi&en accordingl$.

%ile I appreciate $our eagerness to learn design and anal$sis of a *uilding# it appears from $our 4ueries t%at $ou are not sure a*out $our modeling. 5ence# I personall$ feel t%at follo)ing points s%ould *e ept in mind *$ all learners of structural anal$sis and design.  6%ese are m$ personal feelings. +ello) Se(ans ma$ add t%eir &ie)s to guide $oungsters.oo 1. Anal$sis and design soft)are is a tool )%ic% %as to *e used 7udiciousl$. rong input ma$ not *e noti(ed *$ t%e soft)are and it ma$ gi&e output )%ic% ma$ not *e correct at all. ear in mind t%e sa$ing- ar*age Inar*age ut :I;<. 6%us one %as to *e cautious )%ile modeling a structure in a soft)are. 6%e onl$ )a$ is more stud$ and more learning. =ou need to stud$ tutorials and e,amples (rst and t%en &enture out into real pro*lem. A senior in t%is (eld ma$ *e of immense %elp to $ou.oo 2.  6utorial e,amples are a&aila*le in SAP2000 itself including %elp< )%ic% can *e accessed inside

SAP2000 after installation is complete. Please stud$ t%em t%oroug%l$. In t%at )a$# $ou )ill *e a*le to interpret t%e results or output gi&en *$ t%e program. Similarl$# $ou %a&e to *e a)are of limitations of t%e soft)are-)%at can *e modeled and )%at cannot *e modeled or designed *$ t%e particular soft)are. If $ou are not sure a*out a command in t%e soft)are# it is *etter not to use it. Man$ resources are a&aila*le in t%e )e* too. =ou can use atc% and learn< &ideos from !SI )e*site.oo 3. >egarding $our 4uer$ on staircase modeling# one )a$ is using t%e s%ell element )%ic% $ou seem to %a&e used in $our model. t%er )a$ is t%e simpli(ed &ersion of taing loads from staircase onto t%e frame )it%out using t%e s%ell element :i.e. not actuall$ modeling t%e staircase *ut taing loads from staircase onl$;. f course t%e latter approac% )ill not model t%e strut e?ect of t%e staircase.oo @. Pus%-o&er anal$sis is an ad&anced topic for a *eginner. =ou are ad&ised to enter into it )%en $ou are familiar )it% ordinar$ linear staticd$namic met%od.oo ". Mass source is meant for auto-generation of seismic load in SAP2000. As per IS 1893-2002 and NN! 10"# $ou %a&e to consider dead load' speci(ed percentage of li&e load )%ile calculating seismic )eig%t of a *uilding. So# Mass source s%ould *e gi&en accordingl$. +or e,ample# )%ile gi&ing mass source from loads# factor s%ould *e 1 for eac% of t%e dead load items and 0.2" or 0." depending upon li&e load intensit$ for li&e load items. ne ma$ use separate li&e load for roof so t%at it ma$ not *e included in mass source since li&e load is to *e taen as /ero for roof as per codal pro&ision. As said a*o&e# *e sure of t%e meaning of eac% command *efore using t%em.oo . Be(ning load t$pe as reduci*le li&e load alone )onCt automaticall$ reduce li&e load in SAP2000.oo D. %en appl$ing load to area elements# if $ou use area load to s%ell# it )ill *e applied at nodal points of t%e s%ell and for t%is# $ou %a&e to mes% t%e area element in appropriate )a$. If $ou use area load to

frame# t%e same load )ill *e s%o)n as triangles and trape/oids onto t%e frame elements. =ou can searc% t%e SE+I forum for more materials on t%is topic. If t%ere are *eams on all sides of t%e sla*# $ou %a&e to use t)o )a$< distri*ution so t%at load is distri*uted to t%e supporting *eams in one )a$ or t)o )a$ depending upon t%e aspect ratio of t%e sla*.oo 8. >egarding $our 4uer$ on practical reinforcement<# %o) do $ou arri&e at itF Is it from some t%um* ruleF If $ou do correct modeling# t%ere is no 4uestion of )rong output or results. I rel$ on t%e results *ut sometimes# $ou ma$ )is% to &erif$ some elements t%roug% manual c%ecing.oo 9. After anal$sis is complete# element design can *e done. +or t%is $ou %a&e to de(ne )%ic% load com*inations to tae. t%er)ise# SAP2000 )ill tae some default load com*os for designing )%ic% ma$ not *e )%at $ou )ant as per t%e codal pro&ision. So go to t%e design menu and c%oose appropriate load com*os )%ic% $ou %a&e de(ned *efore e,ecuting design command. f course# SAP2000 automaticall$ designs for t%e )orst load com*os at eac% section of *eam after preparing en&elope internall$. =ou can &ie) e&er$ detail of element design meaning t%at )%ic% com*o is ma,imum at left end at top# at left end at *ottom# and so on. +or column# eac% set of PG# Mu, and MG$ %as to *e indi&iduall$ considered for eac% load com*os.oo 10.  =ou are re4uested to start )it% a simple model# sa$ a simpl$ supported *eam# t%en a continuous *eam # t%en a simple 2B-frame so t%at $ou full$ understand t%e *asics. =ou can tae a sol&ed e,ample from a >! *oo to model in SAP2000 and compare t%e result from SAP2000 )it% t%e manual solutionoo Please eep on $our e?orts to learn more.