Introduction to Etabs

Frame and Grid Model• The structure represented by rod or

bar type elements

• Does not model the cross-section dimensions

• Suitable for skeletal structures

• Sometimes surface type structures can also be represented by frame model

• The simplest and easiest model to construct, analyze and interpret

• Can be in 2D or in 3D space

3D Frame

2D Grid

2D Frame

Membrane Model

• Ignore bending stiffness

• Tension / Compression

• In- plane Shear

• For in plane loads

• Principle Stresses

• suitable for very thin structures / members

• Thin Walled Shells,

• Specially Suitable for Ferro Cement Structure

General Plate-Shell Model

• Combined Membrane and Plate

• Suitable for general application to surface structures

• Suitable for curved structures

• Thick shell and thin shell implementations available

• Membrane thickness and plate thickness can be specified separately

• Numerous results generated. Difficult to design the section for combined actions

Shear Wall Design –Meshing

• Shell Deformations:

– Three types of deformation that a single shell element could experience

– A single shell element in the program captures shear and axial deformations well.

– But a single shell element is unable to capture bending deformation.

Connecting Walls to Slab

In general the mesh in the slab

should match with mesh in the

wall to establish connection

Some software automatically

establishes connectivity by

using constraints or “Zipper”

elements

“Zipper”“Zipper”

Shear Wall & Frame

Shear Wall Behavior Frame Behavior

Column – Beam Connection

Scale factor for Response Spectrum

The design spectrum of IS:1893 is actually the MCE(Maximum considered EQ)-level spectrum which must be reduced by dividing this value by a factor of 2R

SF = I*g/(2R)

R is the response reduction factor

I is the importance factor

g is the gravitation force i.e 9.81m/s

Note:-Increase the scale factor of the first run such that the resultant base shear matches the code specification.

Similar Stories Drop Down List

• One Story option. An object drawn in plan occurs only at the level where it is drawn. An assignment made in a plan view applies only to the object(s) actually selected.

• Similar Stories option. An object drawn in plan or 3D view will occur at all stories that are designated as similar to it, if it is designated as a master story.

• All Stories option. An object drawn in plan occurs at all story levels, except the base (or support) level. An assignment made to an object in a plan view also occurs at all story levels, except the base level,

Modeling1.Import DXF file of architectural gridTo ensure that the architectural grid is appropriately imported in ETABS, make sure that the DXF layer names are consistent with the architectural grid you need to import.

2.Import DXF floor planTo ensure an accurate geometric modelling in ETABS, it is recommended that the structural floor plan is used as far as possible. Make sure that appropriate layers are selected to be imported.

• Draw diagonal lines for columns

• Draw centerlines of transfer / lateral beams

• Draw centerlines for shear walls

• Draw X-Y axis to represent origin in ETABS (geometric center of floor)

• Save drawings as *.DXF file

• Import *.DXF file in ETABS as outlines above

3.Define the Grid system

Draw menu objects

Edit Options

Define Menu Assign Menu Display Menu

Design Menu Detailing Menu

Basic load cases

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Dead load (DL)- Self weight + Floor finish

Live load (LL)

Earthquake load in X-direction (EQX)

Earthquake load in Y-direction (EQY)

Load combination(Factored)S.No Load

caseLoad combination

1 Com1 1.5 (DL+LL)

2 Com2 1.2(DL+LL+EQX)

3 Com3 1.2(DL+LL-EQX)

4 Com4 1.2(DL+LL+EQY)

5 Com5 1.2(DL+LL-EQY)

6 Com6 1.5(DL+EQX)

7 Com7 1.5(DL-EQX)

8 Com8 1.5(DL+EQY)

9 Com9 1.5(DL-EQY)

10 Com10 0.9DL+1.5EQX

11 Com11 0.9DL-1.5EQX

12 Com12 0.9DL+1.5EQY

13 Com13 0.9DL-1.5EQY 22

Load combination(UnFactored)

S.No Load case

Load combination

1 FT1 DL+LL

2 FT2 DL+LL+EQX

3 FT3 DL+LL+EQY

4 FT4 DL+LL-EQX

5 FT5 DL+LL-EQY

6 FT6 DL+EQX

7 FT7 DL-EQX

8 FT8 DL+EQY

9 FT9 DL-EQY

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THANK

YOU