Staad Pro Warnings

Warnings in output of Staad Pro

Two warnings : 1. Inst Instab abiility lity 2. Ze Zero ro Stif Stiffn fnes ess. s. 1.0 Instability Warnings: Warnings : Truss member: Defining a member as a TRUSS member when it needs to carry Shear and oment. !e.g" In the truss #oint$ %ertical member will transmit shear forces to the hori&ontal members. If the members are s'ecified as TRUSS elements$ then they cannot carry shear forces and hence will re'ort instability as the load from the %ertical members cannot go through the hori&ontal members. To eliminate this 'roblem$ instead of s'ecifying TRUSS elements$ you s'ecify them as a member with 'artial moment release o'tion. Use member Release s'ecification with 'artial release of (.)) instead of TRUSS s'ecification. Im'ro'er Su''orts: *or e+am'le in a single storey bay ,ortal frame$ if both the su''orts are rollers$ then the frame is instable and hence you will get instability message. -ou must mae one su''ort to be 'inned. Stiffness: /onnecting %ery stiff member with a %ery wea member will gi%e instability. This is due to large %ariation in stiffness of ad#acent members which maes the matri+ in%ersion to re'ort instability. -ou need to ad#ust the I for both the members to eliminate this error. Du'lication: Du'lication nodes at #oint$ o%erla''ing elements$ ,lates will lead to instability. -ou need to go to Tools

 /hec

facilities to detect and eliminate these issues.

There are two checs that you can do to %erify the correctness of results with instability messages. *irst you can study the static chec results. The a''lied loading and su''ort reactions should cancel each other for e0uilibrium. If not$ there is some 'roblemms in the model.

Second is the #oint dis'lacement chec. If you notice e+cessi%e dis'lacement at a node there may be instability at that node. -ou can %iew the instability in 'ost 'rocessing mode. o to odes tab in ,ost 'rocessing and you will see the instability sub tab if there is instability in the mode. /lic this sub tab to %iew the details in table.

2.(

 Zero Stiffness: Stiffness :

The warning will will a''ear when you ha%e a structure structure in which there is no stiffness in a 'articular degree of freedom. 3hile assembling global stiffness matri+ if the stiffness in an acti%e degree of freedom is &ero$ then the structure is considered unable to resist load acting along that degree of freedom. This is re'orted as &ero stiffness messages. This message can be used to in%estigate the cause of instability of the model. The &ero stiffness messages can indicate whether any of the degree of  freedom obstructs the load transmission to the su''orts. Zero stiffness can ha''en in many situations. *or !e.g" a frame with truss members meeting at a #oint a shear and moment and hence no relational stiffness offered at the #oint. This will gi%e &ero stiffness warning. 3e can use ember Reease o'tion instead of truss o'tions. 4nother !e.g" a 'ost held by cables which are 'inned at their base will get warnings for rotational degree of freedom at the cable su''orts. 3e ha%e to use 'artial moment release at one end of cable su''orts to eliminate the message.

Short/uts 5eys used in Staad ,ro Shortcut key

Fuction

Y

STAAD A. Set up

X 1. Global coordinate for Structure : X : as x axis as usual

Z

Y : as y axis as usual Z : perpendicular to paper to top

2. ocal coordinate for indi!idual "e"ber alon# the len#th of the "e"ber is taken as local X axis =o "ethods of creatin# Structure +ata 1. 6sin# co""and file 2. 6sin# Graphical user /nterface

$. %e"bers & 'odes 1. (reation of Geo"etry 2. General para"eters to be fixed ). Analysis *. +esi#n  Geometry

 'ode: co ordinate of all the points of the plan is to be calculated as  'ode 1 2 ) File - 'e -

X aaa ccc

Y ,,, ,,,

Z bbb ddd

/ndian desi#n code 0 check   'e proect

enter3

File 'a"e  3 4 location  3

en#th unit 5 Force 6nit 0 check  Space 0 check   'ext

enter3

Finish

enter3

S=AA+ Screen %enu bar 0 on top =ool bar - on top ?a#e control 0 left side +ata area 08i#ht side %ain drain# area 0 center 

Node

Gi!e +ata for nodes 7ies a!ailable for

Front5 back5 top & iso"etric

8t. (lick 0 labels 0 node no - apply - 9  ;dit < =op "enu bar > to edit data Add Beam : to add bea" or to connect to nodes

@After Add bea"5 #rid ill appear (reate < in +ata area> 6se linear 4 8adial 4 irre#ular  6se plane 4 constr. line etc.

Add beam from left to right & top to bottom.

 'ode crusher 4 $ea" crusher : for selection of node or bea" 8t. (lick 0 labels 0 $ea" no 4 bea" orientation - apply - 9  (ha#e to /so"etric !ie 4 top

 'ode bea" eble 7ie - Structure +ia#ra" 0 eble

 'ode crusher enter3 Select node

< use ctrl key for "ultiple selection>

For column to repeat for floor

Geo"etry < =op "enu bar > 0 =ranslation repeat enter3 Global direction Y check3  'o of steps - xxx

=o chan#e /nput 6nit /nput unit /con 4 =ool - set current input unit

Step spacin# - xxx ink step 0 0 check 9k enter3 For beam to repeat for floor

(han#e to front !ie $ea" crusher select3

 'ode bea" eble 7ie - Structure +ia#ra" 0 eble %e"ber 9ffset $ea" crusher Specification pa#e icon 4 General - Spec. pa#e 6se both start & end point

Select bea"s to be copied by rubber band "ethod 4 pickin# etc. Geo"etry < =op "enu bar > 0 =ranslation repeat enter3 Global direction Y check3  'o of steps - xxx Step spacin# - xxx ink step 0 0 check 9k enter3

=o #et %e"ber infor"ation Select - by all - all bea"s (o""and - pre analysis  print - "e"ber property

For foundation

Si"ilar to abo!e5 but y is -!e. Select ection General ! left ide of creen" #  $roperty

=o 7ie)+ "odel 8t. (lick - structure 0 4 7ie - Structure dia#ra" "enu

Define

=ype of section =o edit input file ;dit input file 4 S=AA+ editor 

%aterial of section For colu"n : ocal B C Global B ocal x C Global y i.e len#th of colu"n ocal y C other side. For $ea" :

ocal y C Global y ocal x C Global y i.e len#th of bea" ocal B C other side i.e. idth of bea".

(olu"n section Y

$ea" section Z

Z

Y

Gi!e data enter3 add  enter 3 . . close  enter3 After selectin# the specific section in the property box5 the sa"e is assi#ned to the "e"bers. (trl - Select "e"ber - assi#n 0 sa!e enter 3 To ee the hape and i%e of column.

8t. (lick 0 labels 0 structure - section out line 0 apply - 9  For center line 8t. (lick 0 labels 0 structure - section out line 0 none - 9  To check the property of any ection i miing

Select < top "enu bar> - "issin# attributes - "issin# property enter3

Adding upport General ! left ide of creen" # 

Support (reate < left side box> Fixed end Add enter3 Front !ie  'ode crusher acti!e3 Select the supportin# nodes

Assi#n To 'ie( (hole tructure

9n top "enu bar  enter3 )oading

+efinition %axi"u" !alue Factor Add (lose oad case detail Add  'u"ber - K5 =itle - load cae #05 Hind in Z dir  Add (lose oad case - K5 Add Hind load5 +irection Z +efine y ran#e %ini"u" 7alue < Gi!e data "ini"u" "ay be 2.1 "> %axi"u" !alue Factor 1 Add (lose oad case detail

Add  'u"ber - D5 =itle - load cae #15 Hind in Z dir  Add (lose oad case - D5 Add Hind load5 +irection Z +efine y ran#e %ini"u" 7alue < Gi!e data "ini"u" "ay be 2.1 "> %axi"u" !alue Factor Add (lose  JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ  *( Load case for Dead load)

oad case detail Add  'u"ber - E5 =itle - load cae #25 +ead oad Add (lose oad case - E5 Add Floor oad ?ressure C ). '4 "2 Y ran#e - Add (lose @oad case detail Add +efine co"bination  'a"e : 4ombination )oad 4ae * : 1.2  'or"al Factor : 1. =ransfer dead & li!e loads to ri#ht !55 Seimic Definition for Spro : 3- & on(ard

/n the seis"ic definition belo self ei#ht 1.

=he "e"ber load copied and pasted ith load chan#in# to ei#ht

2.

=he -!e si#n chan#ed to L !e si#n5 GY to be deleted

).

Also5 the Floor load copied and pasted ith load chan#in# to ei#ht

*.

=he -!e si#n chan#ed to L !e si#n GY to be deleted

.

=he li!e load "ay be reduced to ,. instead of 2 >

 JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ 

*( Analysis )

Analysis < fro" left side "enu bar> ?erfor" analysis  'o print 9  ?re print acti!e +efine co""and < 8t. Side of screen> Support infor"ation acti!e3 Add (lose  'ode crusher acti!e3 M ?rint support infor"ation  acti!e3 Select Supports Assi#n (lose ?ost print acti!e3

+efine co""and < 8t. Side of screen> oad ist acti!e3 =ransfer load list 12 < as foundation is #enerally desi#ned for  & + ith Factor of sefty 1> Support 8eaction acti!e3 Add (lose  'ode crusher acti!e3 M ?rint support reaction  acti!e3 Select Supports Assi#n (lose