ETABS-Exmple using IS 456.pdf

LEARNING OF ETABS SOFTWARE PROBLEM Beam sizes 300×450 mm Columns sizes 300×450 mm Slab thickness 120 mm Storey Height 3.2 m. Live Load 3 kN/m Floor Finish Load 1 kN/m2 Concrete grade M25 Steel Fe415 Earthquake parameters considered are: Zone V Response Reduction Factor :5 Importance Factor :1 Soil : Medium

STEP BY STEP PROCEURE: STEP 1: (Creation of geometry) Open the ETABS Program. Set the units of the model in the drop down box in the lower right hand corner of ETABS window , click the drop down box to set units in KN.m.

From Main menu  File  New Model  Select No.

Building Pan Grid System and Storey Data Definition will be displayed.  Uniform Grid Spacing No. of lines in X Direction =5 No. of lines in Y Direction =4 Spacing in X Direction = 5m Spacing in y Direction = 4m  Simple Grid Data No. of stories =5 Typical Storey Height = 3.2m Bottom storey height = 3.2m Select Grid only button  OK.

Note: You can change Grid spacing by choosing Custom Grid spacing, for column varying spacing then click Edit Grid you can also change any storey height by choosing Custom Storey Data, then click on Edit Storey Data.

Go to Main menu  Edit Storey data  Edit Storey.

STEP 2: (Design Preference code) From Main menu  Options  Preferences  Concrete Frame design Design code =Indian IS456-2000.  Ok.

STEP 3: (Define Material Properties) From Main menu  Define  Material Property  Add new material  Material Name =M25 Concrete cubic comp. strength fck =25 Bending Reinforcement yield strength fy =415 Shear Reinforcement yield strength fy =415  Ok  Ok.

STEP 4: (Define Frame section) Define Beam: From Main menu  Define  Frame section  Add rectangular  Material name =M25 (select)  Section Name=B300x450.

Dimensions: Depth (3) =0.45m Width (2) =0.30m Click reinforcement Select  Beam  Concrete cover to rebar center Top = 0.04m(=25+8+16/2=41 mm) Bottom =0.04m  Ok  Ok.

Define Column: Add Rectangular  section Name =C300x450. Material name = M25 Dimensions : Depth (3) =0.3m Width (2) =0.45m Click reinforcement Select  Column Select  Rectangular Ties  Rectangular Cover to rebar centre= 0.056 (40+8+16/2=56mm) Bar size =16 d Corner bar =16 d  Reinforcement to be designed  Ok Ok.

Define Slab: From Main menu  define  Wall/Slab /Deck section  Add New slab  Section name = S1 Material name = M25.  Membrane Membrane =0.120 m Bending =0.125m Select  Membrane  Ok  Ok.

STEP 6: (Drawing Beams, Columns and Slabs) Drawing Beams: From Main menu  Draw  Draw line objects  Create lines in regions or at clicks(plan,Elev.,3D) Property = Select required beam size B300x450 Click or Select the beam B300x450 in Plan view (Left window) (with similar storey option) and select all beam B300x450. Close.

Drawing Columns: From Main menu  Draw  Draw line objects  Create column in region or clicks(plan)  Property = C300x450  Select or Click on the column joints in Plan view (Left window) with similar storey option. If necessary change angle =90  Close.

Drawing Slab:

From Main menu  Draw  Draw area objects  Create areas at click or click (Plan, Elev.) (Plan)  Property =S120  Click on the periphery of column joints and press enter (With similar storey option).

Note: To view the assigned Beam in plan Select  Set Building Objects on top of Tool bar. Select  Line sections under object view options. To view the assigned Column in plan Select  Set Building Objects on top of Tool bar. Select  section under view by colour Select  Line labels under object view options To view the assigned Slab in plan Select  Set Building Objects on top of Tool bar. Select  Area sections under object view options. To view the rendered view  Set Building view objects on top of Tool bar  Line section.

Special Effects:  Object Fill  Extrusion  Apply to all windows  Ok.

STEP 7:(Assigning Support Condition) Set Base floor Plan view in left window  Main menu  Select  By storey level  select Base  Ok. Set Column points (with mouse) From Main menu  Assign  Joint/Point  Restraints (supports)  Select Fixed  Ok.

To view Support assigned From top Tool bar  Set Building view option  Visible in view  Supports  Ok. Go to Elevation view 1 and view . For other views click   arrow at top of tool bar. STEP 8 : (Defining Loads) 1.Gravity Loads (Dead Load & Live Load) From Main menu  Define  Static Load Cases  Load = SDL (Super Imposed Dead Load) Type = Dead Self weight multiplier =0  Add New Load  Ok. Load = Wall Type= Dead Self weight multiplier =0  Add New Load  Ok.

Note: For Self weight multiplier will be 1 for beams and columns of dead load. For all other loads, it will be zero. Assigning the Loads: Activate left window and set to Plan view  Activate or select similar storey option (at bottom) and select all slabs  From Main menu  Assign  Shell / Area loads  Uniform  Load case name =SDL  Uniform load Load = 1.50 Kn/m2 (units Kn.m) Direction Gravity  Ok. In the same manner assign Load case name = Live  Uniform load Load = 2.0 Kn/m2 (units Kn.m) Direction Gravity  Ok.

Assigning Wall loads: 9” wall load = 12Kn/m (For external or outer beams) 41/2” wall load=6 Kn/m (For internal beams). In left side window select all outer beams in top floor by setting similar storey options and view the status bar to know no. of beams selected  From Main menu  Assign  Frame /Line loads  Distributed Load case name = wall. Unit Kn.m  Forces Direction Gravity Uniform load=12 Kn/m  Replace existing loads  Ok. In the same manner apply 41/2” wall udl load to internal beams by setting “all floor options”. To see the load assigned : Right click the particular member corresponding load  Ok. Note: For point load : From Main menu  Assign  Joint/Point loads  Forces Load case name =Dead. Units Kn.m. Forces Global =10 Kn  Replace existing loads  Ok.

To view slab loads: Display  Show Loads  Shell/Area view. To see the loads on beam: Right click on any beam, we can see number of information on loading on beam.

2. Wind Loads : In ETABS there are two ways to define lateral loads (Wind, earth quake). Built in option will automatically calculate lateral loads as per available design codes. Define wind load parameters as per IS 875 --Part 3 (1987) From Main menu  Define  Static Load cases  Load = Wind X or Wind Y

Type = Wind Self weight multiplier =0 Auto Lateral load =IS 875—1987  Add New Load  Select wind X load and click on modify lateral loads to specify required wind load parameter as per IS 875  Ok  Ok. Creating dummy areas with property =None Set required elevation view in right window  From Main menu  Draw  Draw area objects  Draw rectangular areas  Property = None  Click on the perimeter of area and press enter. Foot Note: Apply wind load for selections. To select wind area Main menu  Select  By area object type  select null  Ok. Assigning wind loads Select drawing area of required elevation  From Main menu  Assign  Shell/area loads  Wind Pressure coefficients  Wind load case name =Wind X Coefficient Cp= - (Change if required)  Ok. To see wind load selection  Set Building view option   Area section  Line section  Ok. 3. Earthquake Analysis In building, slab is considered as single rigid member during earthquake analysis. Select left side window. Select all slabs by setting all floors/ similar storey option  From Main menu  Define  Diaphragms  Select D1  Modify/ Show diaphragms  Select  Rigid  Ok  Ok.

Define Mass Source As per IS 1893--2002 25% of Live load is considered on all floors of building. From Main menu  Define  Mass source  select  From Loads  Load =Dead; Multiplier --1.0  Add Load = Live; Multiplier =0.25  Add Load =SDL; Multiplier =1.0  Add Load = Wall; Multiplier =1.0  Add  Ok.

Define Earthquake Load (Static Method) From Main menu  Define  Static Load cases  Load =EQX Type = Quake Default Multiplier =0 Auto Lateral load = IS 1893—2002   Add New Load  Select the load EQX  Modify lateral load  If required change values as per IS 1893  Select  X Direction

Select  Program calc  Ok  Ok.

 per code =0.16 (change as per requirement)

Assigning Diaphragms Set all storey option and select all slabs  From Main menu  Assign  Shell area  Diaphragms  D1  Ok. Define Earthquake Load (Response Spectrum or Dynamic method)

From Main menu  Define  Response Spectrum Functions  IS 1893 -2002  select IS 1893-2002Spectrum  Ok. Select IS1893  Modify/Show Spectrum  Spectrum case name =IS1893 Damping =0.05 Modal combination  CQC Directed Combination  SRSS Function name=1893; Function damping ration=0.05 Seismic zone factor z=0.16 ; Soil type =1  Ok. To view the Diaphragm Go to  Set Building View objects  Diaphragm STEP 8 : ( Design) Selecting Indian Code From Main menu  Options  Preferences  Concrete Frame  Design code = Indian IS 456-2000.  Ok. Defining Load Combination From Main menu  Define  Load Combinations  Add New Load Comb  Load Combination Name =DL+LL Load Combination type =Add  Change scale factor =1.5 for DL and LL by clicking add button  Add New Load Comb  Load Combination Name =DL+WL Load Combination type =Add  Change scale factor =1.5 for DL and WL by clicking add button  Add New Load Comb  Load Combination Name =DL+EQX Load Combination type =Add  Change scale factor =1.5 for DL and EQX by clicking add button  Ok  Ok. Selecting Design Load ( i.e. DL+LL) From Main menu  Design  Concrete Frame design  Select design comb  Select our combination load from the list  Add  Ok.

STEP 9 : (Analysis) From Main menu  Analysis  Run analysis.

After completing process, the model automatically displaces deformed shape view and the model is locked (you cannot do any changes ).

STEP 10 : (Running the Design Process) From Main menu  Design  Concrete frame design  Start Design/ Check of Structure  Design results will be displayed on the model. Graphical output: Activate 3D view in right window by clicking title bar  Set elevation view =1  From Main menu  Display  Show member force/Stresses diagrams  Frame/Pier/Spandrel forces  Select any load case say DL +LL. Select moment – 3 option  Uncheck the fill diagram. If it is checked, we have to deselect.  check the showed values on the diagram check box  Ok. Right click on any beam in right window which will display diagrams for the beams.

Select  scroll for values (Right top window which will show at different distances along the beam.

To clear the display: Activate right window  From Main menu  Display  Show un deformed shape  Click on 3D button from top tool bar to display 3D view. To view reinforcement detail: Running the Design Process From Main menu  Design  Concrete Frame Design  start design /Check of Structure Design results will be displayed in the model.

Set to Elevation view=1 in right window  Reinforcement area will be displayed on the frame. Right click on any beam or column. We can select various options: - Summary - Flexural details - Shear details etc. - Envelope  Ok.

View the % of steel on beams and columns

From Main menu  Design  Concrete Frame Design  Display design information  select  Design output=rebar percentage  Ok.