EGNEGN--5439 The Design of Tall Buildings5439 The Design of Tall Buildings

Lecture 40Lecture 40

ETABS – Getting Started

Disclaimer by Computer and Structures Inc.“Considerable time and expense have gone into the development and

documentation of ETABS. The program has been thoroughly tested and used. In using this program, however, the user accepts and understand

that no warranty is expressed or implied by the developers or distributors on accuracy or the reliability of the program.

The user must understand the assumptions of the program and must independently verify the results.”

In other words, it becomes the structural engineer’s responsibility to check the ETABS results via simple assumptions and hand calculations.

Disclaimer by Computer and Structures Inc.“Considerable time and expense have gone into the development and

documentation of ETABS. The program has been thoroughly tested and used. In using this program, however, the user accepts and understand

that no warranty is expressed or implied by the developers or distributors on accuracy or the reliability of the program.

The user must understand the assumptions of the program and must independently verify the results.”

In other words, it becomes the structural engineer’s responsibility to check the ETABS results via simple assumptions and hand calculations.

ETABS allows the user to:

Create and modify computer models.

Create structural elements (columns, slabs, shear-walls, beams).

Analyze multiple scenarios and conditions, such as,

Earthquake and wind loads,Sequential loading of construction,

When the analysis is run, it goes from an object based to an element based model,

The analysis consist of frames, joints, linked with shell elements.

Design and optimize multistory buildings (steel/composite, concrete frame and shear-walls.)

All these steps through a single graphic user interface (GUI).

ETABS allows the user to:

Create and modify computer models.

Create structural elements (columns, slabs, shear-walls, beams).

Analyze multiple scenarios and conditions, such as,

Earthquake and wind loads,Sequential loading of construction,

When the analysis is run, it goes from an object based to an element based model,

The analysis consist of frames, joints, linked with shell elements.

Design and optimize multistory buildings (steel/composite, concrete frame and shear-walls.)

All these steps through a single graphic user interface (GUI).

Initial steps to model a building.

1. Define the building’s geometry (it’s footprint, including the adjacent structures, establish the gridlines, etc…).

2. Consider the implications of the geographic location of the building.3. Establish the codes, analysis procedures and design criteria to be applied

(for example, ASCE 7, UBC, IBC2000, Florida Building Code, ACI 318).4. Define the loads (dead, live, reduction factors, wind and seismic).5. Choose the structural elements, such as columns, shear-walls, etc.

6. Define the working units (for example, lb-in, kips-ft, etc.).7. Define the various concrete strengths (eg, 4000 psi, 8000 psi, etc.).

8. Define the modulus of elasticity for concrete.9. Define and create columns sizes and strengths for all different levels.

10. Define wall strengths and thickness.11. Define steel strength and modulus of elasticity.

12. Place columns and shear-walls upon the gridlines.

Initial steps to model a building.

1. Define the building’s geometry (it’s footprint, including the adjacent structures, establish the gridlines, etc…).

2. Consider the implications of the geographic location of the building.3. Establish the codes, analysis procedures and design criteria to be applied

(for example, ASCE 7, UBC, IBC2000, Florida Building Code, ACI 318).4. Define the loads (dead, live, reduction factors, wind and seismic).5. Choose the structural elements, such as columns, shear-walls, etc.

6. Define the working units (for example, lb-in, kips-ft, etc.).7. Define the various concrete strengths (eg, 4000 psi, 8000 psi, etc.).

8. Define the modulus of elasticity for concrete.9. Define and create columns sizes and strengths for all different levels.

10. Define wall strengths and thickness.11. Define steel strength and modulus of elasticity.

12. Place columns and shear-walls upon the gridlines.

Parameters:Parameters: Columns 30Columns 30””x 30x 30””Beams 24Beams 24””x 24x 24””Shear walls: Shear walls: Outer walls: 84Outer walls: 84”” / Inner wall: 24/ Inner wall: 24””Transverse wall: 8Transverse wall: 8””

Shear Wall Preliminary DesignShear Wall Preliminary Design

Define a New ModelDefine a New Model

•• Choose Choose ““NONO””

Define the 1Define the 1stst story.story.

oo Choose Choose ““Grid OnlyGrid Only””..oo Model of 1 story properly, run analysis, and check for Model of 1 story properly, run analysis, and check for

any improperly connected nodes.any improperly connected nodes.

Alternatively, use ETABS’ uniform grid spacing.Alternatively, use ETABSAlternatively, use ETABS’’ uniform grid spacing.uniform grid spacing.

… or ETABS’ custom grid spacing.… or ETABS’ custom grid spacing.

Ready to begin:Ready to begin:

Define Properties:Define Properties:

-- Material PropertiesMaterial Properties-- Frame SectionsFrame Sections-- Slab/Wall SectionsSlab/Wall Sections-- Static Load CasesStatic Load Cases-- Load CombinationsLoad Combinations

Material Properties:Material Properties:

Add new materialAdd new material

…or define material properties (for example, concrete of f’c = 4 ksi).…or define material properties (for example, concrete of f’c = 4 ksi).

Frame SectionsFrame Sections

Add new Rectangular SectionsAdd new Rectangular Sections

Place the concrete columns on the grid.Place the concrete columns on the grid.

Add BeamAdd Beam

Add Wall SectionsAdd Wall Sections

-- Always choose Shell for walls and slabs.Always choose Shell for walls and slabs.-- Membrane and Plate are remnants from Membrane and Plate are remnants from

previous versions.previous versions.

Add the slab.Add the slab.

Define the Load CasesDefine the Load Cases

The Self Weight is to be counted as a dead load.The Self Weight is to be counted as a dead load.

Load CombinationsLoad Combinations

DDL = Design Dead + LiveDDL = Design Dead + LiveSDL = Service Dead + LiveSDL = Service Dead + Live

Draw the columnsDraw the columns

Draw the beamsDraw the beams

Delete the beams and columns to place the shear walls.Delete the beams and columns to place the shear walls.

Draw the shear walls.Draw the shear walls.

Draw the slab.Draw the slab.

Turn on the Object Fill.Turn on the Object Fill.

Delete the slabs inside the core.Delete the slabs inside the core.

Draw the slabs around the core.Draw the slabs around the core.

Mesh the slabs.Mesh the slabs.

Select the frame elements that overlap the shear walls.Select the frame elements that overlap the shear walls.

Delete the overlapping frame elements.Delete the overlapping frame elements.

Apply the Loading.Apply the Loading.

Apply the Loads.Apply the Loads.

Run Analysis:Run Analysis:-- Run analysis and view animation looking for any disconnected Run analysis and view animation looking for any disconnected

nodes/abnormalities.nodes/abnormalities.-- Resolve all errors before proceeding.Resolve all errors before proceeding.

Replicate all stories.Replicate all stories.

Edit the story data.Edit the story data.

Modify the story heights.Modify the story heights.

Place a slab above core.Place a slab above core.

Assign loading to the new slabs.Assign loading to the new slabs.

Run the analysis.Run the analysis.

View Bent B.View Bent B.

Show the member Forces.Show the member Forces.

Zoom in to lower stories.Zoom in to lower stories.

RightRight--click on the lower middle column to view the Forces.click on the lower middle column to view the Forces.

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