SAP2000-Example Moving Load

Moving Load Analysis

of Box Girder

Moving Load Analysis

of Box Girder

Using SAP2000

Table of Content

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

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

Plan and Elevation View

6' 6' Lane 2 Centerline Lane 1 Centerline Frame Elements Centerline 100' 100' 100' 50 ' 20 '

Sections

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 1-3: Back to main screen, showing structure in “3D view” (left window) and

“X-Z Plane” view (right window). Close “3D view” window to enlarge “X-“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”.

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”.

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”

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.

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

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”.

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”.

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 or

Step 5-4 (Assign Columns): Click on or go to Assign > Frame/Cable >

Sections, select “COLUMN” and click “OK”.

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”.

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 >

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

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 =

Define Moving Load Cases

Step 7-1: Click on or go to Define > Analysis Cases. Click on “Add New Case”.

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 8-3: After analysis is complete, check error messages in analysis window. If

no error report, click on “OK” to finish analysis step.

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.

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

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.