SAP2000-Example Moving Load

Moving Load Analysis of Box Girder Using SAP2000

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SAP2000 Tutorial Example

Moving Load Analysis of Box Girder Using SAP2000 Table of Content Objective ...................................................................................................................................................... 3 Problem ........................................................................................................................................................ 3 Material .................................................................................................................................................... 3 Plan and Elevation View .......................................................................................................................... 3 Sections .................................................................................................................................................... 3 Step-by-Step Solution................................................................................................................................... 4 Start modeling by template....................................................................................................................... 4 Modify Structure ...................................................................................................................................... 5 Define Material Properties ....................................................................................................................... 8 Define Frame Section Properties.............................................................................................................. 9 Assign Frame Sections ........................................................................................................................... 11 Define Lanes and Vehicles ..................................................................................................................... 13 Define Moving Load Cases .................................................................................................................... 17 Set Analysis Options and Start Analysis ................................................................................................ 18 View Results........................................................................................................................................... 20

Moving Load Analysis of Box Girder

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Objective To demonstrate and practice step-by-step on the modeling, moving load analysis

Problem Plot influence line for vertical displacement at point A in Lane 1and plot moving load M33 moment for bridge as shown below for worst case of HS20-44 truck load and HS20-44L lane load applied to each lane simultaneously.

Material SteelEc = 5,000 ksi Poissons Ratio =

0.2

Lane 2 Centerline Frame Elements Centerline Lane 1 Centerline

20'

50'

6'

6'

Plan and Elevation View

100'

100'

100'

Sections Box Girder A = I = AShear =

35 500 12 ft2

ft2 ft4

40 400 30 ft2

ft2 ft4

Column A = I = AShear =


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Step-by-Step Solution Start modeling by template

Step 1-1: Start up screen of SAP2000, click on or go to File > New Model. Select working unit = “Kip, ft, F” and select “Portal Frame”.

Step 1-2: Enter “Portal Frame” parameters as shown in above figure and click OK.


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Step 1-3: Back to main screen, showing structure in “3D view” (left window) and “XZ Plane” view (right window). Close “3D view” window to enlarge “X-Z Plane” by clicking at top-right of “3D View” window.

Modify Structure

Step 2-1 (Display Joint & Frame Labels): Click on or go to View > Set Display Options, check the “Labels” box in “Joints” and “Frames/Cables” and click “OK”.


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Step 2-2 (Delete Columns at both ends):Select Frame 1 and 4 by clicking on them one by one and press “Delete” button in keyboard.

Step 2-3 (Assign Restraints): Select Joint 2 and 8. Click on or go to Assign > Joint > Restraints, click on Hinge support button and click “OK”.


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Step 2-4 (Move Joint 5): Click on Joint 5 and go to Edit > Move. Specify Delta Z = “20” (ft) and click “OK”.

Step 2-5 (Divide Frame 5, 6 and 7): Select Frame 5, 6 and 7 by drawing selection rectangular to cover all of them. Go to Edit > Divide Frame, enter Divide into “2” Frames and click “OK”.


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Define Material Properties

Step 3-1 (Change Working Unit): Select “Kip, in ,F” from drop-down menu at the bottom-right of screen.

Step 3-2 (Define Concrete Material): Click on or go to Define > Materials. Select “CONC” and click on “Modify/Show Material”, enter “5000” (ksi) and click “OK” 2 times.


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Define Frame Section Properties

Step 4-1(Change Working Unit): Select “Kip, ft ,F” from drop-down menu at the bottom-right of screen.

Step 4-2 (Define Column Section): Click on or go to Define > Frame/Cable Sections. Select “Add General” from second drop-down menu and click on “Add New Property”


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Step 4-3 (Define Column Section): Enter section property as shown above figure and click “OK”.

Step 4-4 (Define Column Section): Enter Section Name = “COLUMN”, select Material = “CONC” and click “OK”.


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Step 4-5 (Define Girder Section): Repeat Step 4-2 to Step 4-5 to define ”BOXGIRDER” section property.

Step 4-6: Back to “Frame Properties” dialog shows “BOXGIRDER” and “COLUMN” section have been added in the list and click “OK”.

Assign Frame Sections

Step 5-1 (Select Girders): Draw selection rectangular to cover frame 8 to 13. Selection Status at the bottom-left of screen shows “7 Points, 6 Lines Selected”.


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Step 5-2 (Assign Girder Sections): Click on or go to Assign > Frame/Cable > Sections, select “BOXGIRDER” and click “OK”.

Step 5-3 (Select Columns): Change back to undeformed mode by clicking on from Display > Show Undeformed Shape. Click on frame 2 and 3 one by one.


or

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Step 5-4 (Assign Columns): Click on Sections, select “COLUMN” and click “OK”.

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or go to Assign > Frame/Cable >

Define Lanes and Vehicles

Step 6-1 (Define Lane 1): Click on or go to Define > Bridge Loads > Lanes and click “Add New Lane”. Enter Frame = “8”, Eccentricity = “-6” and click on “Add”. Repeat this step to define eccentricity = “-6” to frame 9 to 13 and click “OK”.


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Step 6-2 (Define Lane 2): Back to “Define Bridge Lanes” dialog and click “Add New Lane”. Enter Frame = “8”, Eccentricity = “6” and click on “Add”. Repeat this step to define eccentricity = “6” to frame 9 to 13 and click “OK” 2 times.

Step 6-3 (Select Vehicles): Click on or go to Define > Bridge Loads > Vehicles, select “Add Standard Vehicle” and click on “Add Vehicle”.

Step 6-4 (Select Vehicles): Select Vehicle Type = “HSn-44”, enter Scale Factor = “20” and click “OK”.


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Step 6-5 (Select Vehicles): Back to “Define Vehicles” dialog, click on “Add Vehicle”. Select Vehicle Type = “HSn-44L”, enter Scale Factor = “20” and click “OK” .

Step 6-6 (Select Vehicles): Back to “Define Vehicles” dialog shows 2 vehicle types have been added in list. Click on “OK” to finish this step.


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Step 6-7 (Define Vehicle Classes): Click on or go to Define > Bridge Loads > Vehicle Classes, select “Add new Class”. Select “HSn441”, enter Scale Factor = “1” and click “Add”. Select “HSn442”, enter Scale Factor = “1” and click “Add”. Click “OK” 2 times.

Step 6-8 (Define Bridge Response): Click on or go to Define > Bridge Loads > Bridge Responses, select all response results, select Method of Calculation = “Exact”. Click “OK”.


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Define Moving Load Cases

Step 7-1: Click on

or go to Define > Analysis Cases. Click on “Add New Case”.

Step 7-2: Specify parameters shown in above figure and click “OK”


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Set Analysis Options and Start Analysis

Step 8-1 (Set Analysis Options): Go to Analysis > Set Analysis Options. Select “XZ Plane” and click “OK”.

Step 8-2: Click on or go to Analysis > Run Analysis. Select “MODAL” case and click on “Run/Do Not Run Case” (not required in this example). Click on “Run Now”.


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Step 8-3: After analysis is complete, check error messages in analysis window. If no error report, click on “OK” to finish analysis step.

Step 8-4: Click on

to change back to undeformed mode.


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View Results

Step 9-1 (View Influence Line): Go to Display > Show Influence Lines > Joints. Specify “LANE1”, Joint ID = “10” (middle of bridge), Vector Type = “Displacement” and Component = “U3”. Click “Tables” to view in tabular form or click on “OK” to view influence line in diagram.


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Step 9-2 (View Moment 3-3 Diagram): Click on or go to Display > Show Forces/Stresses > Frames/Cables. Specify parameters as shown in above figure and click “OK”.

Step 9-3 (View Moment 3-3 Diagram): Click on or go to Display > Show Forces/Stresses > Frames/Cables. Specify parameters as shown in above figure and click “OK”.


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Step 9-4 (View Moment 3-3 Diagram): Force diagram in each frame can be displayed by right-mouse clicking. When move mouse over particular diagram, distance and force value will be displayed at the bottom of diagram.


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SAP2000-Example Moving Load

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