ada booklet4.pdf

Advance Design America (VisualDesign) TUTORIAL 4

Composite Beams

Static Analysis &Steel Design

May 2008

© CivilDesign Inc 1995-2008

C O M P O S I T E B E A M S - S T E E L D E S I G N

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Basic Principles Project Configuration If composite beams are not shored during construction, you must define construction stages on the Composite Beam tab of Project Configuration dialog box if you own the Steel Design module. If not, composite beams will be considered as shored.

Creating a Slab Create a Composite slab in the Composite Slabs spreadsheet (Structure menu).

Defining a Composite Beam Open the Member Characteristics dialog box. On the Member tab, activate design criteria, select the Composite Beam option in the "Composition" field and specify the construction stage where the steel member is effective (usually, stage 1).

Then, select the Composite Beam tab. Select the composite slab, effective and current widths and others. You must indicate the construction stage where the composite member is effective.

If you want to get stresses on other points on the steel beam, click the "Extra Calculation – Stresses" button and indicate the location of these points in the specific dialog box. Results are available the in Results / Load Combinations / Stresses – Composite Beams menu when the design is completed.

Load Cases Define one load case per construction stage. Add other load cases if necessary.

Load Combinations Define a load combination per construction stage in the Load Combination Definition spreadsheet and indicate the stage number in the appropriate cell. These load combinations must have an appropriate status such as Service.

Use the Load Combination Generator to create required load combinations according to selected code.

If you want to obtain graphic results for load combinations other than construction stages, select a Service status or ULS no 1 status (CAN/CSA-S6-00) for these.

Results Graphic Results for Composite Beams (Beams Not Shored) When the steel design is completed, select Results / Load Combinations / Stresses – Composite Beams.

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Stresses in Composite Beams (Shored) The spreadsheet Variation of Stresses in Member, which is available in menu Results / Envelope, is only valid for composite beams with no construction stages. Stresses are calculated for the steel shape only, none for the slab.


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A composite beam of 20 meters long will be designed according to code CAN/CSA-S6-00. This beam is not shored during construction so construction stages will be defined. Load cases are: Concrete slab, bitumen and new jerseys. 2D moving loads are also applied. This simple model looks like this:

Project Configuration • Select Project Configuration in the File menu.

Composite Beam Design


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• Select construction stages that apply to the project.

Stage 1 represents the dead load of the steel beam. Stage 2, the casting of the slab; Stage 6, the dead load of wearing surface; and stage7, the dead load of new jerseys.

This composite beam is part of a bridge and we keep the default values entered in section Bridge Design – Fatigue in Studs. Therefore, Fatigue load combinations will be generated, as you will see further on.

• Click OK to save data and exit the dialog box.

Moving Load Cases For the purpose of this example, we only considered two moving load cases (one for ultimate limits states and the other for fatigue). They represent the same moving load case except that the lane overload in not considered for fatigue, in accordance with CAN/CSA-S6-01 Standard. The moving load envelope Lm02 is assigned to the fatigue moving load case. This spreadsheet is accessible through Loads / Moving Load Cases / Definition.

2D Axle Factors 2D axle factors for span and support have been fixed to 1.0.

N O T E S :

2D axle factors for spans are assigned to beams through the Member Characteristics dialog box, as you will see further on.

2D axle factors for supports are assigned to supports through the Supports tab of Node Characteristics dialog box


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Modeling Nodes • Activate the Structure mode and the Node icon. Open the Nodes

spreadsheet through the Structure menu. Add two rows, enter nodes coordinates and select the Support option as type of nodes.

Member

• To create the member, activate the Member icon and the Add mode . Click the first node (i) and the end node (j). The Member

Characteristics dialog box will appear on screen.

• Select a preliminary steel shape and a steel grade. The member end conditions are hinged. Activate design criteria and select the Composite Beam option in the "Composition" field.


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• The construction stage where the member is considered as effective must be selected in the "Effective at stage" field.

• In the "Moving Load Analysis" section, assign "Axis 1" to the member and select 2D axle factors to be applied to this span.

• Click OK.

Note: To learn more about moving load analysis and 2D axle factors, refer to Booklet 14.

• Activate the Restricted Window selection mode to exit the Add mode.

Supports • Activate the Support icon. Select the supports and click the Properties

icon to open the Node Characteristics dialog box. Define the support restraints.

• Select 2D axle factors for supports.

• Click OK.

Composite Slab • Select Structure / Composite Slabs. Insert a row and enter the direction

and thickness. The rebar and concrete materials are required. This slab will be selected when defining the composite beam.


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Press the control key F1 when a spreadsheet is open. It will open the Online Help right at this topic. It is useful to look at the definition of parameters included in spreadsheets.

Defining the Composite Beam • Activate the member icon and double click the beam. Select the

Composite Beam tab.

• Select the composite slab and choose a stud among the drop-down list. Enter the slab effective and actual widths. By default, the shear connectors located between the point of maximum and zero bending moments are 100% effective.


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• Activate the "Use composite properties for analysis" option for considering the transformed-section properties during analysis.

• Select the construction stage where composite effects are effective.

• Close the dialog box.

Options: Add the slab self-weight: Do not select this option when construction stages are defined.

Consider Reinforcement for Mfx - or Mfx +: This option considers the slab reinforcement in the zone of negative or positive bending moment for the calculation of neutral axis.

Extra Calculations – Stresses This function opens a tool that allows defining other points on the steel beam, to obtain stress at these points.

Design Criteria and Specifications Steel Specifications • Select Structure / Specifications / Steel. Insert a row, enter a name to

the specification and select the S6-00-Design steel specification. Select a W shape and the USA section group and corresponding material.

Steel Design tab • Go back to the Member Characteristics dialog box (double click the

beam) and select the Steel Design tab. Select specification S6-00-Design among the drop-down list. Specify a continuous lateral support at the top of the section.


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Load Cases • Select Loads / Load Cases / Definition.

• Insert 3 rows and enter a name to load cases.

• Double-click the "Type" column and select a load case types according to the S6-00/06 standard.

The "Stage" column is completed when the analysis is complete to inform the engineer about the stage number where the load case was applied.

• Press OK.


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Applying Loads • Activate the Load case mode and apply load cases to the beam.

• Slab: -11.28 kN/m

• Bitumen: -6.0 kN/m

• New jersey: -2.5 kN/m.

Load Combinations Construction Stages • Select Loads / Load Combinations / Definition.

• Insert four rows; each one representing a construction stage.

• Select a Construction Stage status and select the stage number in the "Stage" drop-down list.

• Select the Load Factors tab.

• Highlight a load combination in the left part of the dialog box and insert a row in the right part. Select the appropriate load case in the "Load Case" column. The load factor must be equal to 1.0 (service loads).

• Do the same for each construction stage load combination.


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• Press OK.

S6-00/06 Load Combinations We use the Load Combination Generator to generate load combinations in accordance with the S6-00/06 code.

• Select Loads / Load Combinations / Generator.



• Select S6-00 code in the drop-down list and select the Add generated load combinations to existing ones option to keep construction stage load combinations.

• Click "Next".

• On the Specific Options page, include the moving load envelopes in the generation by checking the box Moving load Envelope (Lm).

• Click the Moving Load Envelopes button to open the Moving Load Envelopes spreadsheet.

• Click a cell, right click to open the context menu and select the Select a Code function.



• Select the S6-00/06 code and click the "Reinitialize" button to obtain the

required load combinations and envelopes for this code.

• The spreadsheet appears again with required load combinations and 2D axle factors to use.

• Select the moving load envelopes Lm01 and Lm02 in the "To analyze"

column and click OK to exit the spreadsheet.

• The Specific Options page is still open. Click the Next button. The Selection page shows the load combinations that will be generated when the Finish button will be clicked.



• Click Finish to generate load combinations.

• The Load Combinations spreadsheet is displayed on screen.

Graphic results are available for Construction Stage, SLS 1 (Serviceability Limit States) and Fatigue load combinations statuses.



Special Load Combinations Construction Stages in "Design" mode Steel design results (spreadsheet and design brief) are available for each construction stage if an "Ultimate" status is selected along with a construction stage number.

The Duplicate function (context menu) is used to simultaneously copy data included in all tabs. Duplicated rows are inserted at the end of the spreadsheet.

Procedure • Select row 1, right click to open the context menu and select the Duplicate

function.

The new load combination is copied at row 12.

• Change the name and select an ultimate status.

• Follow the same procedure for other construction stage load combinations.

Analysis and Results

• Open the Analysis and Design dialog box by clicking the icon on Tools toolbar. Launch the steel design by pressing the "Analyse" button. When the design is completed, close the dialog box.

The Design Results icon is automatically on when the design results are available.

• Click the arrow on Activation toolbar to open the Title selection box, which includes a list of available steel design results.

The "Standard" steel design results are those considering ultimate limits states load combinations. Other titles correspond to "ultimate" construction stage load combinations.



Steel Design Results Spreadsheet Standard Results • Select the Standard steel design results on activation toolbar.

• Double click on the beam to open the Steel Design Results spreadsheet or select Results / Structure Design / Steel. The W1000x222 shape was selected.

Note: Results correspond to the most critical load combination, which controlled the design for this member. At the far right of the spreadsheet, you will find the required number of studs in the positive bending zone.

Construction Stage Results • Select an "ultimate" construction stage load combination on Activation

toolbar and look at the design load in the steel design results spreadsheet.



Properties of the Transformed-section The specified ratios "n" (where n = Es/Ec), on the Composite Beam tab of Project Configuration, are used for calculating short-term and long-term deformations. Default values are n=1 for short-term and n=3 for long-term.

The transformed-section properties for short-term and long-term are supplied in the Members spreadsheet in the Structure activation mode.

Short-term

Long-term

Graphical Results (Stresses) for Composite Beams Graphic results provided stresses at the top and bottom of the section and slab, among others.

• Click the beam and select Results / Load Combinations / Stresses – Composite Beams.

• Select a serviceability load combination (construction stage or SLS).



• Select a diagram among the drop-down list.

Note: Available diagrams at "Other points" are the stresses obtained at other points on the steel beam. This tool is accessible through the "Extra calculation – Stress" button on the Composite Beam tab of the Member Characteristics dialog box. The tool is described further on.



Stresses - Load Combination SLS_1_6:

Curves must be located within the allowable limits for maximum tension and compression stresses, which are around +/- 300 MPa.

Calculated Stress:

Sigma Ct = Stress at the top of concrete slab

Sigma Cb = Stress at the bottom of concrete slab

Sigma St = Stress at the top of the section

Sigma Sb = Stress at the bottom of the section

The maximum stress (Sigma Sb) occurs at the bottom flange of W1000x222.

Place your cursor on the curve and right click to display coordinates. The maximum stress is 272.3 MPa.



Stresses due to fatigue: N. B. At least one "fatigue" envelope or two "fatigue" load combinations are required to obtain such results.

Spacing of Studs



Stresses at Other Locations on the Beam Advance Design America has a tool that consists in calculating stresses anywhere on the steel shape. Up to four points can be defined by the user. We are going to use this tool, which is available on the Composite Beam tab of Member Characteristics dialog box.

Positions must be defined with respect to the direction of arrows.

Procedure: • Before activating this tool, we have to take not of the shape dimensions.

• Select Common / Shapes / I Shapes.

• Locate the W1000x222 shape in the spreadsheet. Click in a cell, right click to open the contextual menu and choose the Detail function to open the Shape Properties dialog box.



Take note of dimensions d, b, t, and w (653mm, 330mm, 39.9mm, and 22.1mm). Close the dialog box and spreadsheet.

We want to get stress results at these points on the beam:

• Select the Composite Beam tab of Member Characteristics dialog box

and click the "Extra Calculations – Stresses" button.

• The following dialog box appears on screen. Select faces on the beam and specify the distance to each point with respect to the convention shown in the right part of the dialog box.




Launch the design again • Click the member and select Results / Load Combinations / Stresses –

Composite Beams.

• Select the Stresses in Composite Beam (Other Points) diagram.



• Close the dialog box.

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