SAP2000-Example 2D Steel Tower

Static Analysis and Design of

2D Transmission Tower

Using SAP2000 (Metric Units)

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SAP2000 Tutorial Example: Analysis and Design of 2D Transmission Tower 2/23

Static Analysis and Design of

2D Transmission Tower Table of Content

Objective ......................................................................................................................................................... 3

Problem ........................................................................................................................................................... 3

Step by Step..................................................................................................................................................... 5

1. Start Model with Template................................................................................................................. 5

2. Modify Model .................................................................................................................................... 7

3. Define Material Properties ................................................................................................................. 8

4. Import Angle Members and Define Auto Selection Member ............................................................ 9

5. Assign Frame Member ..................................................................................................................... 11

6. Define Load Case ............................................................................................................................. 12

7. Assign “WIND” Load Case ............................................................................................................. 13

8. Assign Groups .................................................................................................................................. 14

9. Analysis the Model........................................................................................................................... 18

10. Design Steel Members ..................................................................................................................... 19

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Objective

To demonstrate and practice step-by-step on the modeling, static analysis and design of 2D transmission tower.

Problem Find the suitable steel angle members for 2D transmission tower by using AISC-LRFD93 design code with the following details

Material Properties (Steel)

Young Modulus of Steel (Ec) = 2,000,000 kg/cm2

Unit Weight of Steel = 7,800 kg/m3

Yield Stress of Steel (Fy) = 2,400 kg/cm2

Tensile Stress of Steel (Fu) = 4,000 kg/cm2

Load Case

Load Name Load Type Details

DEAD Dead Load Self Weight: Calculate automatically using Self Weight Multiplier in SAP2000

WIND Wind Load See in Elevation View

Load Combination for Pushover Analysis

Name Details

DSTL1 1.4 DEAD

DSTL2 1.2 DEAD +1.6 LIVE

DSTL3 1.2 DEAD + 0.5 LIVE + 1.3 WIND

DSTL4 1.2 DEAD - 0.5 LIVE + 1.3 WIND

DSTL5 0.9 DEAD + 1.3 WIND

DSTL6 0.9 DEAD - 1.3 WIND

Note: No LIVE load case in this example

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Step by Step

1. Start Model with Template

Step 1-1: Select Working Unit and Start New Model with Template Start up screen of SAP2000, select working unit to be “kg-m” at drop-down menu on the bottom-right of screen and click on to start new model with template

Step 1-2: Select Template Type Select “Braced Frame” from template list

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Step 1-3: Specify Geometry Properties Specify two “Braced Frame” geometry properties as shown in above figure.

Step 1-4: Create Model 2 bays tower has been created from parameters that specified from previous steps. The left bay will be deleted in the next step. Close left window by clicking on .

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2. Modify Model All leg and horizontal members will be deleted in this step.

Step 2-1: Select Leg Members in Left Bay Click on to change to selecting mode and draw rectangular selection to cover leg member in left bay as shown in above figure.

Step 2-2: Select Horizontal Members Click on to change to “Select using Intersecting Line” and draw selecting line to pass all horizontal members in left bay as shown in above figure. Press “Delete” to delete all selecting members.

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3. Define Material Properties

Step 3-1: Change Working Unit and Select Material Change working unit to “kg, cm”, go to Define > Material, select “STEEL” and click on “Modify/ Show Material” button.

Step 3-2: Specify Steel Material Properties Specify material properties as shown in above figure.

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4. Import Angle Members and Define Auto Selection Member All angle member properties will be imported from built-in database first and define all imported L-Shaped member to the list of section (“AUTO1”) for auto member selection in design step.

Step 4-1: Import Angle Go to Define > Frame/Cable Section, select “Import Angle” from first drop-down menu as shown in above figure and click on “Add New Property” button

Step 4-2: Specify Steel Member Database Go to folder that SAP2000 has been installed (normally should be “C:\Program Files\Computers and Structures\SAP2000 8”) and select database name “AISC3.PRO”.

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Step 4-3: Select All Angle Members Select all angle members by clicking on first member and clicking on the last member by holding “shift” button and click on “Ok” button in “Angle Section” dialogue.

Step 4-4: Define Auto Selection Member Back to “Frame Properties” dialogue, shows all angle members have been imported to the properties list at left column. Select “Add Auto Select” from second drop-down menu and click on “Add New Property” button.

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Step 4-5: Select Section Properties for Auto Selection Member Select all angle members (same method as previous step) and click on “Add->” button to move all angle members from list (left column) to auto selection list (right column).

5. Assign Frame Member

Step 5-1: Select all Members Click on to select all members in model.

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Step 5-2: Assign Frame Selection Go to Assign >> Frame/Cable >> Sections, select “AUTO1” and click “OK” button.

6. Define Load Case

Step 6-1: Add “WIND” Load Case Go to Define >> Load Case, specify “WIND” load case as shown in above figure and click on “Add New Load” button.

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7. Assign “WIND” Load Case

Step 7-1: Select Nodes Select 5 nodes from top by selecting and drawing rectangular line to cover desired nodes as shown in above figure.

Step 7-2: Assign “WIND” Load Case Go to Assign >> Joint Load >> Forces, select load case and specify “Force GlobalX” as shown in above figure.

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Step 7-3: Assign Windward Pressure Coefficients Repeat step 7-1 and step 7-2 to assign nodal force to the remaining nodes

8. Assign Groups 3 member groups are required in this example (Leg, Horizontal and Brace) for steel design.

Step 8-1: Select Leg Members Click on and draw 2 selection rectangular to cover all leg members as shown in above figure.

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Step 8-2: Add New Group Go to Assign >> Assign to Group and click on “Add New Group” button.

Step 8-3: Assign “LEG” Group Specify “LEG” group name and click “OK”.

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Step 8-4: Select Horizontal Members Draw selection rectangular to cover all horizontal members one by one. To check all horizontal members are selected or not by selecting View >> Show Selection Only to view only selected members

Step 8-5: Assign “HORIZONTAL” Group Go to Assign >> Assign to Group and repeat step 8-2 and 8-3 to assign “HORIZONTAL” group.

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Step 8-6: Select Bracing Members To show all members, go to View >> Show All. Clicking on and draw selection line to pass all members as shows in figure. This selection will select all horizontal and bracing members.

Step 8-7: Deselect Horizontal Members Go to Select >> Deselect >> Groups and select. Only bracing members are selected now. That can be checked from View >> View Selection Only.

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Step 8-8: Assign “BRACING” Group Go to Assign >> Assign to Group and repeat step 8-2 and 8-3 to assign “BRACING” group.

9. Analysis the Model

Step 9-1: Start Analysis Go to Analyze >> Run Analysis, and click on “Run Now” button.

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Step 9-2: Check Error Message Check error message after analysis status show “ANALYSIS COMPLETE”.

10. Design Steel Members

Step 10-1: Select Design Code Go to Options >> Preference >> Steel Frame Design and select “AISC-LRFD93” from design code

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Step 10-2: Select Design Group Go to Design >> Steel Frame Design >> Steel Design Group and select all 3 groups as shown in above figure by selecting and clicking “Add - >” button.

Step 10-3: Select Design Load Combination Go to Design >>Steel Frame Design >> Steel Design Combo, all design combination according to specified design code are added in the list. To view detail of each combination, select one of them and click on “Show”

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Step 10-4: Assign Effective Length Factor Select all members by clicking on , go to Design >> Steel Frame Design >> View/Revise Overwrites and change parameters as shown in above figure.

Step 10-5: Start Design Go to Design >>Steel Frame Design >> Start Design/ Check of Structures and wait until SAP2000 show the design output.

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Step 10-6: Check Analysis and Design Section Go to Design >>Steel Frame Design >> Verify Analysis vs Design Sections, to see number of difference sections between analysis and design. Click on “OK” button.

Step 10-7: Reanalysis Go to Analyze >> Run Analysis, and click on “Run Now” button

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Step 10-8: Redesign and Reanalysis Repeat Step 10-5 to Step 10-7 until there is no difference between analysis and design member.

Step 10-9: View Design Member Go to Design >> Steel Frame Design >> Display Design Info and select second drop-down menu and select “Design Sections” as shown in above figure.

Documents

SAP2000-Example 2D Steel Tower