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					EGN-5439 The Design of Tall Buildings Lecture 40

ETABS – Getting Started

Disclaimer by Computer and Structures Inc. Disclaimer by Computer and Structures Inc. “Considerable time and expense have gone into the development and “Considerable time and expense have gone into the development and documentation of ETABS. The program has been thoroughly tested and documentation of ETABS. The program has been thoroughly tested and used. In using this program, however, the user accepts and understand used. In using this program, however, the user accepts and understand that no warranty is expressed or implied by the developers or distributors that no warranty is expressed or implied by the developers or distributors on accuracy or the reliability of the program. on accuracy or the reliability of the program. The user must understand the assumptions of the program and must The user must understand the assumptions of the program and must independently verify the results.” independently verify the results.” In other words, it becomes the structural engineer’s responsibility to check In other words, it becomes the structural engineer’s responsibility to check the ETABS results via simple assumptions and hand calculations. the ETABS results via simple assumptions and hand calculations.

ETABS allows the user to: ETABS allows the user to: Create and modify computer models. Create and modify computer models. Create structural elements (columns, slabs, shear-walls, beams). Create structural elements (columns, slabs, shear-walls, beams). Analyze multiple scenarios and conditions, such as, Analyze multiple scenarios and conditions, such as, Earthquake and wind loads, Earthquake and wind loads, Sequential loading of construction, Sequential loading of construction, When the analysis is run, it goes from an object based to an element When the analysis is run, it goes from an object based to an element based model, based model, The analysis consist of frames, joints, linked with shell elements. The analysis consist of frames, joints, linked with shell elements. Design and optimize multistory buildings (steel/composite, concrete frame and Design and optimize multistory buildings (steel/composite, concrete frame and shear-walls.) shear-walls.) All these steps through a single graphic user interface (GUI). All these steps through a single graphic user interface (GUI).

Initial steps to model a building. Initial steps to model a building.
1. Define the building’s geometry (it’s footprint, including the adjacent 1. Define the building’s geometry (it’s footprint, including the adjacent structures, establish the gridlines, etc…). structures, establish the gridlines, etc…). 2. Consider the implications of the geographic location of the building. 2. Consider the implications of the geographic location of the building. 3. Establish the codes, analysis procedures and design criteria to be applied 3. Establish the codes, analysis procedures and design criteria to be applied (for example, ASCE 7, UBC, IBC2000, Florida Building Code, ACI 318). (for example, ASCE 7, UBC, IBC2000, Florida Building Code, ACI 318). 4. Define the loads (dead, live, reduction factors, wind and seismic). 4. Define the loads (dead, live, reduction factors, wind and seismic). 5. Choose the structural elements, such as columns, shear-walls, etc. 5. Choose the structural elements, such as columns, shear-walls, etc. 6. Define the working units (for example, lb-in, kips-ft, 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.). 7. Define the various concrete strengths (eg, 4000 psi, 8000 psi, etc.). 8. Define the modulus of elasticity for concrete. 8. Define the modulus of elasticity for concrete. 9. Define and create columns sizes and strengths for all different levels. 9. Define and create columns sizes and strengths for all different levels. 10. Define wall strengths and thickness. 10. Define wall strengths and thickness. 11. Define steel strength and modulus of elasticity. 11. Define steel strength and modulus of elasticity. 12. Place columns and shear-walls upon the gridlines. 12. Place columns and shear-walls upon the gridlines.

Parameters:

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

Shear Wall Preliminary Design

Define a New Model

• Choose “NO”

Define the 1st story.

o Choose “Grid Only”. o Model of 1 story properly, run analysis, and check for any improperly connected nodes.

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

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

Ready to begin:

Define Properties: - Material Properties - Frame Sections - Slab/Wall Sections - Static Load Cases - Load Combinations

Material Properties: Add new material

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

Frame Sections Add new Rectangular Sections

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

Add Beam

Add Wall Sections - Always choose Shell for walls and slabs.

- Membrane and Plate are remnants from previous versions.

Add the slab.

Define the Load Cases
The Self Weight is to be counted as a dead load.

Load Combinations DDL = Design Dead + Live SDL = Service Dead + Live

Draw the columns

Draw the beams

Delete the beams and columns to place the shear walls.

Draw the shear walls.

Draw the slab.

Turn on the Object Fill.

Delete the slabs inside the core.

Draw the slabs around the core.

Mesh the slabs.

Select the frame elements that overlap the shear walls.

Delete the overlapping frame elements.

Apply the Loading.

Apply the Loads.

Run Analysis: - Run analysis and view animation looking for any disconnected nodes/abnormalities. - Resolve all errors before proceeding.

Replicate all stories.

Edit the story data.

Modify the story heights.

Place a slab above core.

Assign loading to the new slabs.

Run the analysis.

View Bent B.

Show the member Forces.

Zoom in to lower stories.

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

DILBERT DILBERT


				
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