Booklet14 Graitec Moving Loads

8/12/2019 Booklet14 Graitec Moving Loads

1/32

Advance Design America (VisualDesign)TUTORIAL 14

Moving LoadAnalysis2D &3D

May 2008

CivilDesign Inc1995-2008


2/32


3/32

B A S I C P R I N C I P L E S

CivilDesign Inc. 14-1

GeneralThe Moving Load analysis module computes internal forces, influence lines,and envelopes generated by moving loads such as trucks, trains or cranerunways. The module was developed in such a way that it allows theapplication of customized trucks and design codes. In fact, engineers can usestandardized moving loads, as per codes, or they can create their own.

Pre-Defined Trucks

Advance Design Americaincludes a list of predefined trucks in the MovingLoad Definitionspreadsheet, which is accessible through Common/Trucks.

These trucks are described in several standards (CAN/CSA-S6-88, S6-00 andAASHTO LRFD-04). Each one of these trucks represents a different movingload case according to the position of axles and dynamic load allowance (DLA)factor. Refer to clause 3.8.4.5 of CAN/CSA-S6-00 standard.

Data cannot be modified in this spreadsheet. However, new "customized"trucks can be added at the end of the spreadsheet. For a quicker editing,duplicate an existing row and modify duplicated parameters.

To know the weight and the number of axles that are considered for each truck(load case) listed in the spreadsheet, select theAxles/Wheelstab.

Trucks NomenclatureAdvance Design America is using the following nomenclature to describetrucks listed in theTrucks spreadsheet:

Examples:

[3D] CL1-625 0.25: 3D structural model using a CL-625 truck, Level:Normal and 1, and DLA factor of 0.25.

[2D] CL123-625 0.30a: 2D structural model using a CL-625 truck, Level 1,2 & 3, and DLA factor of 0.3. Letter "a" means that an axle is removed. Thiscase is different from case "b" and "c".

Definition of Mobile Axis

Three moving load axes are available to study forces and displacementsinduced by trucks that are moving on different axes.

Axes can be located along members, plates (one side), and floors (one side).The axis number is selected in respective dialog boxes.

Basic principles


4/32


5/32

B A S I C P R I N C I P L E S


A maximum of 10 envelopes can be generated in a single analysis.Concomitant values (Mx, Vy, Nz, etc.) can be obtained for critical forces, foreach envelope. These concomitant values must be selected in the MovingLoad Analysisdialog box.

Generation of Load CombinationsUse the Load Combination Generation Wizard to generate the requiredload combinations as per selected building code. Select the option that includesthe Lmi envelopes in the generation.

Moving Load Analysis

Open the Moving Load Analysis dialog box by clicking this icon orselect Moving Loadsin theAnalysismenu.

In the displayed dialog box, select options such as envelopes, concomitantvalues, critical scenario (load case), etc.

Results

Results are in the form of envelopes (Lmi), which can be included in loadcombinations. Individual envelope results can be read through the Envelopeactivation mode. Use theView Optionsfor graphic results and select Results/ Envelopeto obtain numerical results.

Design

When a design is launched, the moving load analysis is automatically launchedat each cycle of design because it is part of the design iterative process.

Before launching a design, open the Moving Load Analysisdialog box, selectsome options and close it. Then, launch the design process.


6/32


7/32

3 D M O V I N G L O A D A N A L Y S I S


Definition of the Project

Length of bridge: +/- 50,000 m

Maximum width: 25,200 mNumber of spans: (2) spansLength of spans: +/- 23,500 m

Bridge Deck:Semi-continuous, prefab prestressed concrete beams NEBT 1200 withtransverse post-tensioning and a composite slab of 220 mm.

Moving Loads:Standard: CAN/CSA-S6-00 (Cl-625 truck).

The 3D model is as follows:

Moving Load Axis

2-Way Floors

The moving load axis is located along the sides of floors at the centre of thebridge.

Select the Structure mode and the Floor element.

3D Moving Load Analysis


8/32

A D A T U T O R I A L 1 4

14-6 CivilDesign Inc

Select the strip of floors located at the centre. Click the Propertiesicon to open the Floor Characteristicsdialog box.

Select the moving load axis number and specify on which side of floors ispassing this axis. In our case, side jk. (To know on which side is passing theaxis, display the floor local axis system through theView Options, as

shown below.)


9/32



Click OK to close the dialog box and save data.

Trucks and Load CasesThe CL-625 truck will be used for the design of this bridge (CAN/CSA-S6-00).

Select Common/Trucksand consult the list of pre-defined trucks. Sort datato group the [3D]-CL-625 moving loads.


10/32



Moving Load Cases

The Generator is used to quickly define moving load cases. The generatedcases will be listed in the Moving Load Casesspreadsheet, which is accessiblethrough Loads/ Moving Load Cases / Definition.

Select Loads/ Moving Load Cases / Generator. In the Optionspage of the generator, select code CAN/CSA-S6-00 in

the list box. The type of transitory loads will beNormal and Level 1. Justbelow the code, activate the "3D" radio button. Select moving load axis1 and the traffic on the axis.

Lateral displacements of trucks must be specified for 3D project only (at thefar left and right of moving load axis), according to the chosen layout.


11/32



In the 3Dsection of the dialog box, look at the four available layouts.Select the first one, which generates the truck displacements at the leftand right of the moving load axis.

Then, enter the distance at the far left (x2) and far right (x1).AdvanceDesign Americawill generate moving loads between these two ends.

Sign Convention

According to the local axis of the moving load axis, x2 is positive and x1,negative.

Four lanes can be loaded simultaneously. The default distance centre-to-centreof trucks (dM) is 3m. We keep this value.

Number of Loaded Lanes Select the #1, #2, #3, and #4 lanes at theNumber of lanes simultaneously

loadedsection.

Click theNextbutton.The second page of generator shows the moving loads that are to be generated(at the right) according to the offsets listed in the left part of the dialog box.Moving loads are all selected by default, meaning that each one will begenerated using the listed offsets. To withdraw a moving load, click on thename to cancel the selection.


12/32



Advance Design America is planning the generation of five moving loads

(listed at the right) using 12 offsets (listed at the left), which correspond to thefirst, second, third and fourth loaded lanes. Consequently, a minimum of 60moving load cases will be generated. Fatigue moving load cases, which are notconsidering the lane overload, will be added to these moving loads byAdvance Design America.

Click the Finishbutton. The Moving Load Casesspreadsheet appears onthe screen.

15 moving load cases are generated for Fatigue limit states (without laneoverload). The corresponding moving load envelope is named Lm02.

Below the list of fatigue moving load cases, we find 60 Resistancemoving loadcases, which are considered for ultimate limit states design. The correspondingmoving load envelope is named Lm01.


13/32



The nomenclature of generated numbers is as follows:

1F: Fatigue moving load case applied to the moving load axis #1;1R: Resistance moving load case applied to the moving load axis #1;1x1+043: First moving load applied when only one lane is loaded, with a 4.3moffset;5x2+073: Fifth moving load applied when two lanes are loaded, with a 7.3moffset. (To know the second offset, select the Componentstab.)

Select the row that corresponds to the moving load case 1R_5x2+073. Inthe spreadsheet, we can see that the second offset is equal to 4350mm.

Note: The "Factor" column: This factor is applied to concentrated loads andlane overload. It is used as aModification Factorin a 3D model when many lanesare loaded.

View Options

Display the Moving Load axis and a Moving Load Case

Open theView Optionsdialog box and select theAttributestab. Choose themoving load axis number and select a moving load case in the drop-down listbox.


14/32



Moving Load Case #1R_5x3+030

Moving Load Envelopes

Moving load envelopes must be selected in this spreadsheet before launching amoving load analysis. A code must be selected in this spreadsheet to obtain therequired load combinations and corresponding envelopes.

Select Loads / Moving Load Envelopes. Click any cell and right click to open the context menu. Choose the Select

a codecommand.


15/32


16/32


17/32



ClickNext. In the Specific Optionspage, include moving load envelopes.Note: The "Moving Load Envelopes" button opens the Moving LoadEnvelopesspreadsheet. Envelopes are already selected.


18/32



ClickNext.


19/32



Click Finish.The Load Combinationspreadsheet is displayed on the screen.

Close the spreadsheet.

Moving Load Analysis Open the Moving Load Analysisdialog box by clicking the icon on

the Tools toolbar and select analysis options.


20/32



Click theAnalyzebutton to launch the analysis. Close the dialog box whenthe analysis is completed.

Results Moving Load EnvelopesGraphic ResultsThe Envelope mode is automatically selected when the analysis is completed.

Select envelope Lm01or Lm02.

Open theView Optionsdialog box and select the Resultstab. Select atype of result to display.

The image below is showing bending moments on strong axis (Mx), formoving load envelope Lm01.


21/32



Select a bridge axis and use the Maskfunction.

Go back to the Resultstab in theView Optionsdialog box and select theDeflectiondiagram.


22/32



Member Forces and Concomitant ValuesDouble click on a member to open this spreadsheet. Minimum and maximumforces are listed and concomitant values also (if they were selected in theMoving Load Analysisdialog box).

Support Reactions (min/max)Double-click on a support to open this spreadsheet or select many supportsand select Results / Envelope / Support Reactions (min / max).

Load Combinations and Design Results

Launch a bridge design by clicking the Design icon.

The moving load analysis is part of the design iterative process. It isautomatically launched at each cycle of design (steel, concrete, or prestressedconcrete design, etc.). Therefore, we suggest selecting appropriate options inthe Moving Load Analysisdialog box before launching the design process.


23/32



Project Definition

Composite beam of 20m long on a single span;Stud: Neilson 22mm;Concrete slab of 200mm.

Moving Loads: CAN/CSA-S6-00

2D Axle Factors

Axle factors are required for a 2D project. These factors are applied to thecalculated forces that are transmitted to supports and spans.

Use the tables included in Section 5.7.1 of the S6-00 standard and calculate Fvand Fm. Then, from these values, calculate Vg and Mg along with axle factors.

In Advance Design America, the axle factor, Fa, multiplies the totalmaximum force (shear and bending moment) as follows:

Vg = Fa *Vt

Where Vt is the maximum shear force per lane acting on a section of thestudied span.

Mg = Fa * Mt

Where Mt is the maximum bending moment induced by one truck on a sectionof the studied span.

2D Axle Factors SpreadsheetWhen axle factors are calculated:

Open the 2D Axle Factorsspreadsheet (Loadsmenu) Insert a row and give a name to axle factors (spans and supports).

2D Moving Load Analysis


24/32



Click in each cell and enter factors.

Close the spreadsheet.Assign 2D Axles Factors to Span and Supports Select the Member element and double click the beam. On the Membertab of the MemberCharacteristicsdialog box, select

Axis 1as the moving load axis and the Span_1as the 2D axle factors to beconsidered, in the "Moving Load Axis" section.


25/32



To learn more about composite beam design, please refer to Tutorial 4.

Close the dialog box. Select the Support element on the Elements toolbar and select both

supports. Click the Propertiesicon. Select Support_1as the 2D axle factorson the Support tabof the Node Characteristicsdialog box.

Close the dialog box.


26/32



Trucks

CL-625 trucks are used for this project, according to the CAN/CSA-S6-00code. To consult the list of pre-defined [2D]-CL-625 trucks, select Trucks in

the Common menu.

Moving Load Cases

Use the Moving Load Case Generator, located under Loads / MovingLoad Cases/ Generator to quickly generate required cases according tocode S6-00.

In the first page, select the S6-00 code and the type of transitory loads.Activate the "2D" radio button, select the moving load axis and specifytraffic on the bridge.

Click theNextbutton.In the next page, we can see that five moving loads are applied at an offset of0.0m from the moving load axis because it's a 2D model. To remove a movingload from the list, click the name to cancel the selection.


27/32



Click the Finishbutton.The following moving load cases are generated. Please refer to the previousexample to know the nomenclature that is used for the numbering of cases.

Close the spreadsheet.Moving Load Envelopes

Moving load envelopes must be activated in this spreadsheet before launching

a moving load analysis. When a code is selected in this spreadsheet, you obtainthe required load combinations to analyzed, 2D axle factors to defined andcorresponding envelopes.

Select Loads / Moving Load Envelopes. Click in any cell and right click to open context menu. Choose the

command Select a code.

In the Selectiondialog box, select code S6-00 and click the "Reinitialize"button.


28/32



Activate (double click) moving load envelopes Lm01 and Lm02.

Load Cases and Load Combinations

Load CasesThe following load cases are defined in the Loads Definition spreadsheet(Loads / Load Cases / Definition) for the composite beam. Theycorrespond to construction stages that we specified in the Composite Beamtab of ProjectConfigurationdialog box.

Load Combinations

Construction stage load combinations are defined "by hand" in the LoadCombination spreadsheet before using the Load Combination Generator.


29/32


30/32



Include moving load envelopes in the generation and clickNext.


31/32



Click Finish.The Load Combinationspreadsheet is displayed on the screen.

Close the spreadsheet.Steel Specification

Open the Steel Specificationsspreadsheet (Structure/ Specifications).Consult the default values associated to the S6-00 Verificationspecification.Modify parameters if necessary.


32/32

Booklet14 Graitec Moving Loads

Documents

Transcript of Booklet14 Graitec Moving Loads