Structural Bridge Design UK

November 2013

Example Manual

British Standards

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Legal Notices Autodesk

Structural Bridge Design 2014

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Disclaimer

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Table of Contents

v. Introduction

1. Setup and Configuration

2. Section Definition

3. Section Analysis

4. Beam Definition

5. Beam Design

6. Analysis - Model Definition

7. Analysis - Load Definition & Solution

8. Transfer of Data

9. Specialist Analysis Techniques

10. Complete Examples

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Introduction This manual is intended to act as a general guide to the solution of typical examples that are applicable to Autodesk Structural Bridge Design 2014. There are ten sections, each containing a number of workshop examples that the user can work through using the program, by following the described procedures. Most workshops are simple and intended for relatively new users to the system but there are also some more detailed examples providing an insight into some of the more advanced capabilities of the software.

The document is provided as a pdf file which can be accessed through the help menu in the software and is generally displayed through a pdf reader such as Adobe Reader.

The main contents page gives the headings of the main sections. These are hyperlinked in the document so clicking on a title will take the user directly to the appropriate section. The first page of each section shows the contents for that section, listing the workshops included. This is also a hyperlinked page.

Files

Some of the examples require data files to be loaded or opened. All these files can be found in a compressed zip file located in the SBD\Examples\Version 6\BS Data Files folder of the software installation. To use these files you must copy the BS Examples.zip file to a suitable folder on your local hard drive and extract the files to this location.

At the end of some examples the user is asked to save a data file which may be used in a subsequent example. To prevent the overwriting of the supplied files different file names have been used. These files can optionally be used as input instead of the supplied data files if required.

Projects

An example of setting up a project is given in section 1 and this project template is saved. All other examples assume that this project is used throughout, giving default materials, units, titles etc. If you carry out example 1 in section 1 then the Version 6 Examples project will always be available in the list of projects when starting new problems. If this is not the case or you wish to work on an example without setting up your own examples project template then this can be loaded from the supplied file Version 6 Examples.spj when in the Project Templates form.

Semantics

The procedure for each example is given as a series of step by step instructions, making reference to data form names, field names, user input, menu items etc. To enhance the readability of these instructions some basic rules have been followed when preparing these instructions.

1. Text in Bold with a vertical bar separating words indicates a menu item (eg

Options | Project Templates...)

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2. Form names ,data field labels and drop down lists are indicated as coloured italic

text such as Define Beam Loading

3. Text in double quotation marks generally indicates a button found on a data form

or user input (eg ...click on the OK button)

Other Useful Information

Having Auto Redraw switched on will mean that the graphics displayed in the

graphics window will be updated automatically as you progress your work.

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1. Setup and Configuration

Contents 1.1. Project Setup ............................................................................................................. 1-3 1.2. Templates for Multiple Design Codes ........................................................................ 1-7

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1.1. Project Setup

Subjects Covered:

Design Code; Company Identity; Project Template Titles; Project Template Units; Project Template Materials; Preferences; Material Properties

Outline

Autodesk Structural Bridge Design 2014 may be used numerous times within a project and certain data will be common to all jobs within this project. In fact some data will be common to all projects. Much of this data can be set up as a default by defining project templates and completing company information which will stored in the system registry for each user.

In this example we set up the default company information and create two project templates. One called Version 6 Examples with all the necessary titles, units and materials and another with no settings for title and materials but with default units.

Procedure

1. Start the program.

2. Use the menu item Options|Design Code to select British Standards

3. Open the Set Company Identity form by using the menu item Options|Company Identity.

4. Enter your Organisation Name and your Office address

5. Click on the Load button to select a bitmap to display as a logo in the heading of any output that is produced by the program. Browse to the examples folder and select the Autodesk logo. Alternatively use your own logo bitmap.

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6. Click on OK and confirm that the changes should be saved

7. Open the Preferences form using the menu item Options|Preferences and on the general tab ensure that the box for Display Overview form when file is opened is ticked and the other boxes are unticked.

8. On the Graphics tab of the Preferences form, tick the box for Reverse direction of plotted Bending Moments , so that BM diagrams are plotted with sagging moments (Positive) below the beam and switch on Auto Redraw so that graphics displays are automatically updated. Note that the colours used for the chart data series can be defined by the user on this tab.

9. Click on OK to close this form

10. Open the Project Template form using the menu item Options|Project Templates. Create a new template by clicking the + button. This brings up a secondary data form which should be set to Default settings before clicking on OK. Rename the project template to Version 6 Examples by highlighting the generated name in the Project Template field and re-typing it.

11. Use the same name in the Job Title field and set the Job Number to 1

12. Select the Units tab. Change the units for velocity to m/s and ensure that units for acceleration are set to m/s2.

13. Select the Materials tab. Create a BS5400 concrete material by clicking on the dropdown list in the first row of the Type column and select Concrete -

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BS5400. By default this concrete has a characteristic strength of 40 N/mm2 which is grade 40 concrete. Click on the OK button to accept this material.

14. Click in the Type column in the second row to create a second BS5400 concrete material, but change the characteristic strength to 50N/mm2. Click on OK to accept.

15. Create a BS5400 reinforcement material using the default values. Click on OK to accept.

16. Create a Prestressing Strand material for BS5400, again using the default values. Click on OK to accept.

17. Create a Structural Steel material using the default values. Click on OK to accept.

18. Click on the Export Template button and save the file as My Version 6 Examples BS.spj.

19. Click on the OK button of the Project Templates form.

20. Close the program.

Summary

The data created in this example will be used as default values when any new job is started. Of course this data may be changed at any time to reflect local requirements without affecting the project settings. For example, the default value for the SLS compressive stress limit factor is 0.5, which is ok for RC bending sections. However, we would need to alter this if the section under consideration was a compression or pre-stressed section.

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1.2. Templates for Multiple Design Codes

Subjects Covered:

Default materials for different design codes; Templates from existing templates; Saving templates.

Outline

Autodesk Structural Bridge Design 2014 may be used for projects that require design checks to more than one design standard. It is convenient to set up a project template that contains material data relating to design parameters pertaining to specific codes of practice. In this way, when a structure, beam or section is defined using one design code, and then the design code changes, the appropriate materials are automatically re-assigned.

In this example we use the project template created in example 1.1, called Version 6 Examples, to provide the defaults for a new project template called Multiple Codes. This contains materials relating to British Standards only. We then add additional materials for Eurocode design. It is important to have the same number of materials for each design code and they must be in the same order. Finally we export this template to an external file so that it can be loaded by other users checking our work, or as a backup.

Procedure

1. Start the program.

2. Use the menu item Options|Design Code to select British Standards

3. Click on OK on the information form.

4. Open the Project Template form using the menu item Options|Project Templates. and make sure the current template is set to Version 6 Examples. Create a new template by clicking the + button. This brings up a secondary data form which should be set to A Copy of Version 6 Examples before clicking on OK. Rename the project template to Version 6 Examples - Multiple Codes by highlighting the generated name in the Project Template field and re-typing it. Also, change the Job Title to Multiple Codes in the Job Title field.

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5. Use the same name in the Job Title field and set the Job Number to 1.2.

6. Select the Materials tab and make sure the Design Code field in this form is set to Eurocode then create a concrete material by clicking on the dropdown list in the first row of the type column and select Concrete Parabolic Rectangle. By default this concrete has a rect/parabolic stress strain relationship and has a characteristic cube strength, fck, of 50 N/mm

2. Change the cube strength to 40N/mm2. Ensure that the Design Code Section button is set to EN 1992-2 and then click on the OK button to accept this material.

7. Create a second concrete material the same as the first but accept the default characteristic cube strength of 50N/mm2. Click on OK to accept.

8. Create a (horizontal) reinforcing material using the default values. Click on OK to accept.

9. Create a (horizontal) Prestressing Steel material, again using the default values. Click on OK to accept.


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11. Click on the Design Code drop down menu and select Australian and New Zealand Standards from the list.

12. Create a concrete material and change the Characteristic Strength to 31.875N/mm2. Click on OK to accept. Create another concrete property and change the Characteristic Strength to 40N/mm2. Click on OK to accept.

13. Create a Reinforcement material using the default values. Click on OK to accept.

14. Create a Prestress Strand material using the default values. Click on OK to accept.


16. Click on the Design Code drop down menu and select AASHTO from the list.

17. Create a concrete material with a Characteristic Strength to 31.875N/mm2. Click on OK to accept. Create another concrete property and change the Characteristic Strength to 40N/mm2. Click on OK to accept.

18. Create a Reinforcing Steel material using the default values. Click on OK to accept.

19. Create a Prestressing Steel material using the default values. Click on OK to accept.


21. To save this project template for use by other users click on the Export Template... button and save as a file called Multiple Codes.spj in a suitable location.

22. Click on the OK button of the project templates form.


Summary

The data created in this example is just an illustration of how project templates can be used for multi-code projects. It also shows how project templates can be saved and used by other users. This is particularly important when our work is being checked by others as they may not have the same projects set up. This does not cause a problem as all data is local to the data file but warning messages will be displayed warning that the assigned project template could not be found.

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2. Section Definition

Contents 2.1. Simple Edge Section .................................................................................................. 2-3 2.2. Voided Slab ................................................................................................................ 2-7 2.3. Reinforced Concrete Column ................................................................................... 2-11 2.4. Plate Girder .............................................................................................................. 2-15 2.5. Encased Steel Column............................................................................................. 2-19 2.6. Composite Section ................................................................................................... 2-23 2.7. Pre-stressed section ................................................................................................ 2-27

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2.1. Simple Edge Section

Subjects Covered:

Titles; Material property changes; Section Definition; Parametric Shapes; Define shapes; Inserting points; Arcs

Outline

The shape below is created by using a parametric L section and then modify by inserting points, changing vertex coordinates and changing segments to arcs. Grade 40 concrete is assigned to the section

Procedure

1. Start the program and ensure that the current Project Template: is set to Version 6 Examples using the Options|Projects Templates menu item.

2. Begin a new section using the menu item File|New Section.

3. Use the menu item Data|Titles... to set the title as Grillage Edge Section with a sub-title of Example 2.1. Also add your initials to the Calculated by data item. Click on OK to close the titles form.

4. Open the Define Material Properties data form using the menu item Data|Define Material Properties... Delete the structural steel (Redundant Property) and prestress properties (Prestress Strand) by clicking twice in the Name field and then using the delete key. Click on OK to close the form.

5. Open the Define Section form using the menu item Data| Define Section...

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6. In the first row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Use the dropdown list to change the shape from rectangle to L and set the width to 1000mm, the height to 750mm, the thickness of horizontal to 200mm and vertical to 250mm.

7. Click on OK to close this secondary form.

8. Using the dropdown list, change the Parametric Shape to Define Shape. This will display a secondary form and a graphic showing all the vertices and coordinates.

9. Click on the second point in the vertices (Y) list and notice that the circle around the point at the bottom right of the L has turned red. This is the current point. Select the + button to insert a point midway along the bottom edge of the L.

10. Now click on the fifth point in the vertices list and use the + button to add a point midway along the top of the bottom flange.

11. Now click on the eighth point in the vertices list and use the + button to add a point midway along the top edge of the vertical.

12. Change the coordinates in the table to the following;

13. Double click on the Arc tick box for the point (as shown) at the centre of the top of the vertical to create the curve on the top. Change the Name field to Edge Section.

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14. Click on OK to close the Define Element Shape form and then select the grade 40 material from the dropdown list of properties in the Define Section form.

15. Click on OK to close the Define Section form.

16. Used the menu item File|Save as to save the section with a file name My BS Example 2_1.sam.


Summary

Section shapes can be created in a number of ways. There are many predefined parametric shapes and standard beams stored in the program library, which can be used unaltered. These can be converted to a general defined shape and modified.

This example shows how to do this and how to assign a particular material to a section component.

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2.2. Voided Slab

Subjects Covered:

Creating Voids, Continuous faces, Reinforcing faces, Manipulation of hook points

Outline

A hole can be created in a section by defining a second component, entirely contained within the first component and assigning it a void property. If a section is part of a larger section then the torsion property calculations need to know this, so the continuous faces must be identified. Reinforcement can be defined relative to a face with a specific diameter, spacing and cover. The section below can be created to illustrate all these aspects.

Procedure


2. Begin a new section using the menu item File|New Section....

3. Use the menu item Data|Titles... to set the title as Voided Slab Section with a sub-title of Example 2.2. Also add your initials to the Calculated by data item. Click on OK to close the titles form.

4. Open the Define Material Properties form using the menu item Data|Define Material Properties... Delete the structural steel (Redundant property) and prestress properties (Prestress Strand) by clicking twice in the Name field and then using the delete key. Click on OK to close the Define Material Properties form.

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5. Open the Section Definition data form using the menu item Data| Define Section...

6. In the first row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Use the dropdown list to select Rectangle (if it is not selected automatically) and set the width to 1200mm and depth to 900mm. Click on OK to close this secondary form.

7. Assign Grade 40 concrete to this component by using the drop down selection of the Property field.

8. Click on the two vertical edges (once) and the solid lines change to dashed lines. This signifies that these are continuous faces.

9. Create a second parametric component using the drop down list in the field and change the shape to Circle (in the Shape Reference field) with a diameter of 550mm. Close this form using the OK button.

10. Change the Hook point number for both components to 0.

11. Change the X Coord and Y Coord of both components to 0.

Click twice and press the delete key to delete this entry

Click once to make dashed

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12. Leave the Property of the second component as Void as this will form the hole and then close the Define Section form using the OK button.

13. Open the Define Bars and Tendons form from the Data|Define Bars... menu item.

14. Change the Generate option to Reinforce Faces and change Position By to Exact Spacing with a spacing of 100mm.

15. Set the Bar diameter to 40mm and then click on the bottom face of the rectangle in the graphics window to display a data form allowing the definition of the reinforcement cover. Set this cover to 50mm and then close the form using OK.

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16. Note that the reinforcement material property is automatically selected (but could be changed if a second reinforcement property is defined).

17. Close the Define Bars and Tendons form using OK.

18. Save the data file using the File|Save as... menu item as My BS Example 2_2.sam.


Summary

Voided slab sections are often used to represent the longitudinal stiffness of a grillage beams. It is important that the torsion properties are calculated correctly and that if Cracked section properties are required then the reinforcement is correctly defined.

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2.3. Reinforced Concrete Column

Subjects Covered:

Reinforcement to two covers; Snapping to reinforcement; editing reinforcement cover and size

Outline

A simple reinforced concrete section is required to represent a section of a column as shown below. Initially 25mm bars are placed in the positions shown below. This is done by placing a bar in each corner, with the appropriate cover, and then using these bars as snap points drawing a number of bars between them. This creates duplicate bars in the corners but these are automatically deleted when the form is closed.

It is then realised that 32mm bars should have been used instead. The bars are edited to change the diameter but then the cover needs adjusting back to 46mm.

Procedure



3. Use the menu item Data|Titles... to set the title as RC Column Section with a sub-title of Example 2.3. Also add your initials to the Calculated by data item. Click on OK to close the titles form

4. Open the materials data form using the menu item Data|Define Material Properties... Delete the structural steel and prestress properties by clicking twice in the name field and then using the delete key. Click on OK to close the Define Material Properties form

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6. In the first row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Use the dropdown list to select Rectangle and set the width to 500mm and depth to 400mm. Click on OK to close this secondary form.


8. Open the Define Bars... form from the Data|Define Bars... menu item.

9. Change the Generate option to 1 bar by 2 covers and change Diameter to 25mm.

10. Click on one of the corners of the rectangle in the graphics window to display a data form allowing the definition of the reinforcement cover. Set this cover to 46mm on both faces and then close the form using OK.

11. Repeat step 9 for the other three corners noting that the cover is automatically set to the last defined.

12. Change the Generate option to Draw Bars and set Position By to Number. Set the No. of bars to 4 and leave the Diameter as 25mm.

13. In the graphics window toolbar, set the snap option to Bar/tendon then click on the bottom left hand bar in the graphics window followed by the bottom right

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hand bar. This will create an extra 4 bars, 2 of which will be superimposed on the corner bars.

14. Repeat this with the two top corner bars.

15. Change the No. of bars to 3 and draw in the bars along the remaining two vertical edges in the same way.

16. Close the Define Bars and Tendons form using the OK button and a message should be displayed saying Superimposed bars have been deleted.

17. Re-open the Define Bars and Tendons form using the menu item Data|Define Bars...

18. Click on the Edit bars.. button and then draw a window around all bars in the graphics window by clicking once in one corner and then clicking again in the opposite corner of the rectangular section. The bars should turn red and a secondary Edit Reinforcement form should be displayed. Change the Edit Option to Change bar diameter and set the Bar Diameter to 32mm. Close the Edit Reinforcement form using the OK button and the bars are updated.

19. The cover to these bars has then been reduced to 42.5mm so we need to move the bars to re-establish 46mm cover. This can also be done using the Edit Bars... button but can only be done one face at a time. Click on Edit Bars... and then window round the topmost row of bars. Change the Edit

First click

Second click

Snap mode

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Option to Reset Cover in the Edit Reinforcement data form and set the cover to 46mm before closing the form with the OK button. The cover to these bars has now been adjusted.

20. This can be repeated for the bottom row of bars and each side row, remembering to click on the Edit Bars... button each time before selecting the appropriate bars. Close the Define Bars & Tendons form using the OK button.

21. The data can then be saved, using the menu item File|Save as..., to a file called My BS Example 2_3.sam.


Summary

This is a simple example that illustrates the creation of a reinforced section which is then needed to be modified. This is a process that can happen frequently in a real design cycle. For this simple section it would probably be just as simple to delete the bars and re-specify them but for more complex sections this may be time consuming.

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2.4. Plate Girder

Subjects Covered:

Multiple components; joining components; copying components; rotating components; using Shove to locate components accurately; User defined library shapes.

Outline

The shape below is created by using a parametric I section and then adding four parametric Angle shapes as the cleats. Standard structural steel properties are applied to all components. The section is edited using the join facility to combine the components into one defined shape.

Procedure



3. Use the menu item Data|Titles... to set the title as Cleated Plate Girder Section with a sub-title of Example 2.4. Also add your initials to the Calculated by data item. Click on OK to close the Titles form.


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5. In the first row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Use the dropdown list to change the shape from Rectangle to I and set the width of both flanges to 500mm, the overall height to 900mm, the thickness of top & bottom flanges to 40mm and the thickness of the web to 20mm. Click on OK to close this secondary form.

6. Resize the graphics window to a reasonable size by clicking on the corner of the window and with the mouse button held down, drag to the new position. Zoom the graphics so that the shape fits the new screen size by clicking on the fit view button in the toolbar of the graphics window.

7. In the second row of the Library column select Parametric Shape from the dropdown list. Use the dropdown list to change the shape from rectangle to L and set the width and height to 75mm and the thicknesses of both horizontal and vertical to 12mm. Click on OK to close this secondary form.

8. The angle will appear in red with a circle shown at the reference point. Click once on this little circle, releasing the mouse button, and drag the shape to a new location beneath the top flange and to the right of the web, as show below. Place the angle at this location by clicking the left mouse button again.

9. Use the rotate edit button to orientate the angle with the arms pointing to the right and vertically down (This could be achieved by entering the angle in the correct column in the table).

10. Now use the Shove Up and Shove Left edit buttons to locate the angle in its final position.

11. Now use the Copy icon in the graphics toolbar to create a second angle component and repeat 8, 9 and 10 to place it in the top left internal corner.

12. This can be repeated twice more to place angles into the bottom internal corners.

Shove Left Copy

Rotate

Fit View

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13. At the moment, all components have a material property void, so apply the Steel property to all components.

14. Although this section can be left as five separate components it may sometimes be desirable to join these components into one shape. This is done by selecting one of the angle components and then using the Join edit toolbar button to combine it with the component touching or overlapping with it. This is then repeated with the other three angles to give the one define shape component. (The user may find that clicking just once on the Join button simultaneously joins all of the components together).

15. Open up the Define shape form by clicking on define shape and re-selecting it from the drop down list. Change the name to 500 by 900 plate girder then click on the Add button to add it to a library file. This will open a file browser form which will allow you to choose an existing library file, if it exists, or to create a new one. We will create a new one by entering a library file name of My Useful_Sections.lib and then clicking on the save button.

16. Close the Define Element Shape data form using the OK button.


18. Use the menu item File|Save as... to save the section with a file name My BS Example 2_4.sam.


Summary

Sections can be built by combining many different simple components to create more complicated shapes. For composite sections where the components have different material properties then the components will remain as individual entities but if the material is the same they may be joined to form a single shape. This will allow the section to be stored as a single user defined library section.

The edit toolbar on the graphics window provides many tools for manipulating components of a section.

Join

Rotate

Shove

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2.5. Encased Steel Column

Subjects Covered:

Enclosing one section in another, adjusting material properties; Universal Columns; Import shape from Autodesk AutoCAD; Copying components

Outline

An oval shaped concrete column casing, with major axis 800mm and minor axis 600mm is cast concentrically around a steel Universal Column (356x368x202) as shown below. The concrete is grade 30 and the structural steel has a yield strength of 355N/mm2 and elastic modulus 205kN/mm2.

The oval outline has previously been created in AutoCAD and saved in a dxf file. This can be imported into the program before adding the standard steel shape. This shape is added twice, once with void properties (to create a hole in the concrete) and a second time with steel properties.

Procedure



3. Use the menu item Data|Titles... to set the title as Encased steel section with a sub-title of Example 2.5. Also add your initials to the Calculated by data item. Click on OK to close the titles form.

4. Open the Define Material Properties form using the menu item Data| Define Material Properties... and then open the Property Details for the grade 40 concrete by clicking on it in the table. Change the Characteristic Strength to

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30N/mm2 and then click the OK button on both the Define Property Details and Define Properties form to close the forms and ensure that any changes are saved.

5. Open the Define Section data form using the menu item Data| Define Section... . In the first row of the Library column select Import Shapes from the dropdown list which will open a file browser. Navigate to the file called BS Example 2_5 Elipse.dxf and open it. Click the Next button on the Import Shapes form which has appeared on the screen. This will display the general define shape in the graphics window and show the coordinates in the data form. Enter a Name for this component as Encased Concrete in the Define Element Shape form and close it with the OK button.

6. Assign a material property from the Property column drop down list as the 30N/mm2 concrete.

7. In the second row of the Library column select Steel Sections from the dropdown list which will open a secondary form in which British Sections are chosen and a Universal Column is selected from the choice of Steel Section Range. The serial size is set to 356x368 with a weight of 202kg. Close the Define Section Details form with the OK button.

8. For both the section components change the hook point to number 0 and set the coordinates to (0,0). Zoom the image in the graphics window to fit the

screen using the Fit View toolbar button.

9. If the steel section is not already set, then set the focus on the steel section by clicking on it (it will turn red if a line becomes a dashed line then click on it again to make it a solid line). Use the Copy toolbar button to create a second instance of this shape

. Set the Property of this second shape to be that of Steel and again set the Hook point to 0 and the coordinates to (0,0).

10. Close the Define Section form using the OK button and then use the menu item File|Save as... to save the section with a file name My BS Example 2_5.sam.

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Summary

This method is the easiest way of enclosing one shape within another as the Merge facility used in example 2.7 only works when boundaries overlap with each other. This process can be repeated several times to create sections such as a concrete tube enclosed between two concentric steel tubes of different radii.

A second method, which may be necessary in some circumstances, is to create the encasing component as a single component, without a void component, by applying a split between the external and internal surfaces (look at the parametric shape of an annulus as an example). Alternatively the encasement can be made up of a number of separate components, touching at the boundaries (e.g. a box section made up from two rectangular webs and two rectangular flanges), although this would not represent the torsion properties correctly.

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2.6. Composite Section

Subjects Covered:

Multiple components with different materials; Standard steel library shapes; Reinforce faces; Hook Points

Outline

A composite steel girder and concrete slab is shown below. The slab is 200mm thick and the effective width is 1500mm. Reinforcement is placed in the bottom of the slab using 12 no. 25mm diam. Bars, equally spaced with 50mm cover to the bottom face. The steel girder is a standard steel universal beam section classified as UB 914x419x388. Grade 40 concrete is used for the slab and the standard steel and reinforcement materials are applied respectively. The slab is part of a wider continuous slab.

Procedure



3. Use the menu item Data|Titles... to set the title as Composite steel/concrete Section with a sub-title of Example 2.6. Also add your initials to the Calculated by data item. Click on OK to close the titles form.


5. In the first row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Set the width to be 1500mm and the height to 200mm, and then click on OK to close this secondary form. The slab is to be positioned so that the midpoint of the bottom face is to be at the origin. This is

2-24

done by changing the Hook Point to be -1 and then setting the coordinates to (0,0).

6. The two short edges of the slab are identified as continuous faces by clicking once on each (they turn to dashed lines) and the material for the slab is set to grade 40 concrete by using the drop down list in the Property column.

7. In the second row of the Library column select Steel Sections from the dropdown list. Use the dropdown list to ensure that the Steel Sections Library is set to British Sections and the Steel section range to Universal Beam. Then select the Serial size as 914x419 and the weight to 388kg. Select Steel from the Property dropdown menu. Close the form by clicking on the OK button.

8. To locate the top of the flange at the centre of the underside of the slab, change the Hook Point of the steel section to -5 and set the coordinates to (0,0). The material of the steel beam should be set to the structural steel property.

9. Close the Define Section form by clicking on the OK button.

10. Open the Define Bars form using the menu bar item Data|Define Bars. Set the Generate field to Reinforce face(s), set the number of bars to 12, set the bar diameter to be 25mm and then click on the bottom edge of the slab, which will open a secondary data form.

Click on Bottom Face

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11. In this form set the cover to be 50mm and the number of faces to be 1 and then click on OK to draw the bars.

12. Close the Define Bars and Tendons data form using the OK button.

13. Use the menu item File|Save as to save the section with a file name My BS Example 2_6.sam.


Summary

Sections can be built by combining many different simple components to create more complicated shapes. Special libraries have been built containing the major shapes for steel sections which can be used to build up the section. This covers UK, American, Australian, European and Japanese standard sections

2-27

2.7. Pre-stressed section

Subjects Covered:

Precast concrete beams; Tendon definition and placement; Section outline from text file; Initial Prestress forces; Arcs; Merging; Hook points;

Outline

It is required to generate a section of a precast edge beam comprising of a standard YE3 precast beam (Grade 50 concrete) and an insitu slab and edge detail (Grade 40 concrete) as shown below. The section is created using 3 components, 1) a standard precast section from a built in library, 2) a parametric rectangular section for the slab and 3) a general defined shape with specific coordinates for the edge detail. These sections will overlap so they must be merged to eliminate the duplicated material.

Two rows of tendons are placed in the bottom of the beam (11 in the bottom row and 14 in the second) together with two tendons in the top. The bottom row is placed 60mm from the bottom face of the beam with the end tendons 100mm from the vertical faces. The second row is placed 110mm from the bottom face of the beam with the edge tendons 60mm from the vertical faces. The top two tendons are placed 800mm from the bottom face and 72mm from the edge faces. Each tendon (Grade 1776) consists of one strand of 15.2mm diameter and is initially stressed to 225kN.

X Y

1 -100 1350

2 -350 1350

3 -400 1100

4 -550 850

5 -554 753

6 -450 690

7 -100 690

8 -100 1350

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Procedure



3. Use the menu item Data|Titles... to set the title as Prestressed Section with a sub-title of Example 2.7. Also add your initials to the Calculated by data item. Click on OK to close the titles form.

4. Open the Define Material Properties data form using the menu item Data|Define Material Properties... Delete the structural steel by clicking twice in the name field and then using the delete key. Open the data form for the prestress material and set the characteristic strength to 1776N/mm2. (This gives a force of 225kN when 70% is applied to a 15.2mm diameter strand).

5. Click the OK button on both the Define Property Details and the Define Material Properties form to close both forms and ensure that any changes are saved.

6. Open the Define Section data form using the menu item Data| Define Section...

7. In the first row of the Library column select Concrete Beams from the dropdown list. This will display a secondary form (with graphic showing a standard bridge beam). Use the dropdown list Concrete beam range to select a YE beam and set the Shape no. to YE3. Click on OK to close this secondary form.

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9. In the second row of the Define Section form create a second component by picking Parametric Shape from the dropdown list. Set the width to 600mm and the depth to 160mm. Assign Grade 40 concrete to this component.

10. Now manipulate the positions of the components so that the origin is at the midpoint of the bottom face of the beam. This is done by setting the hook point of the concrete beam section to -1 and setting the coordinates to (0,0). The insitu slab can be positioned by also setting the hook point to -1 and the coordinates to (200,870) (allowing 20mm for permanent formwork above the rebate).

11. The two components overlap, so, to cut out the insitu slab around the beam, select the slab in the list of components and, in the graphics window toolbar, click on the Merge button.

12. The insitu edge detail now needs to be defined. Create a third component, using the dropdown list in the Library column, as a define shape. The coordinates, as defined in the table above, can be entered by either typing the coordinates directly into the shape coordinates table (using the + button to add a row), or by entering the coordinates into a text file such as notepad, copying them to the clipboard (Control/C) and then using the right mouse button menu option in the coordinate table, pasting them in. Set the section name to Edge Detail.

Merge

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13. A more accurate shape can be given by fitting arcs where appropriate. Tick the arc box in rows 3 & 5 and click on OK to close the Define Shape form. A form appears telling you that the sections intersect. Click the OK button on this form.

14. Assign Grade 40 concrete to this component.

15. Again the two components overlap, so, to cut out the edge detail around the beam, select the Edge Detail in the list of components and, in the graphics window toolbar, click on the Merge button. Click on the OK button to close the Define Section form.

16. Click No on the confirm form. To define the tendons select the menu item Data|Define Bars.

17. Select 1 tendon by 2 covers from the dropdown list in the Generate field and set the area of strand to 181mm2 (the area of a 15.2mm diameter strand). In the graphics window click on the left vertical face of the precast beam (becomes bold) and then on the bottom face which displays a secondary form. Set the Cover to face 1 to 100mm and Cover to face 2 to 60mm. Click OK on the Locate Tendons form. Notice that the force in the tendon is 225kN (but this could be changed as necessary). Repeat this for the bottom right corner of the beam. Repeat on the bottom right corner with covers to face 1 and 2 60mm and 110mm respectively and then again on the bottom left.

18. Select Draw tendons from the dropdown list in the Generate field and change the snap option in the graphics window toolbar to bar/tendon. Set Position By to Number and No. of tendons to 11. Now click on the bottom left hand tendon in the graphics window and then again on the bottom right (generating

Face 1 Face 2

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11 extra tendons with superimposed tendons in the corners). Repeat this for the second row but setting the No. of tendons to 14.

19. The top two tendons are created by using 1 tendon by 2 covers option and selecting the vertical and bottom edges with covers of 72mm and 800mm for both corners.

20. Close the Define Bars and Tendons form using the OK button. An information message is displayed informing that superimposed tendons have been automatically removed.

21. Use the menu data item File|Save As to save the data file as My BS Example 2_7.sam.


Summary

This section is now ready for section property calculations and stress analysis. The example shows the build up of components, using merge, arc, and hook point facilities as well as illustrating the use of standard library shapes. The edge detail illustrates the ability to cut and paste geometry from a spread sheet or text file. Inserting tendons demonstrated that a tendon could be placed with respect to two faces (which dont have to be contiguous). The default tendon force is calculated from the characteristic strength, the initial percentage and the tendon area, although this will generally be adjusted to take care of losses.

3-1

3. Section Analysis

Contents 3.1. General Section Properties ..................................................................................... 3-3 3.2. Torsion & Shear Section Properties ...................................................................... 3-13 3.3. Differential Temperature ....................................................................................... 3-19 3.4. Early Thermal Cracking Calculations .................................................................... 3-23 3.5. ULS Capacity and stresses of an RC Section ....................................................... 3-29 3.6. Crack Width & Stress Calcs of an RC Section ...................................................... 3-41 3.7. General Stress Strain Analysis .............................................................................. 3-47 3.8. Stresses at transfer of a prestress section ............................................................ 3-53 3.9. Staged Construction of a Composite Section ........................................................ 3-59 3.10. Interaction Curves for Columns ............................................................................. 3-65

3-3

3.1. General Section Properties

Subjects Covered:

Gross section properties; Transformed section properties; Net Transformed section properties; Full plastic moments; Moving the section origin; Reinforcement bar translation.; Results viewer; PDF results viewer

Outline

The calculation of section properties for three of the sections defined in section 2 will be considered as follows:

Example 2.6

Calculate

Section properties of the gross section (neglecting any difference between material properties).

Section Properties of the transformed section (transformed to grade 40 concrete).

Transformed bending Inertia Ixx about an axis 200mm below the bottom of the slab (the global centroid axis of the complete bridge deck cross section).

Example 2.2

Calculate

Net transformed Ixx (cracked section properties) transformed to grade 40 concrete.

Example 2.4

Calculate

Full plastic moment of the section according to BS5400 Part 3.

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Procedure

1. Start the program and use the menu item File |Open to open the file BS

Example 2_6.sam created in example 2.6.

2. Use the menu item Data Titles to open the Titles form. Change the Sub-title to Example 3.1a and the Job Number to 3.1a. Click on OK to close the Titles form.

3. Ensure that Analysis Type is set to Section Properties by using the menu item Data |Analysis Type then use the menu Calculate |Analyse to open the Calculate Section Properties form.

Gross Section Properties

4. Click on the Section properties for drop down and select Gross Section from the list. This will display the results shown below.

5. Click on the Results button to see the detailed results as a text file. This can be saved as a Rich Text Format (rtf) file if required

6. Click on the PDF View tab at the bottom of the results viewer to display the results with the graphics in the form of a PDF document. This can then be saved as a PDF file if required. Page numbering, User defined titles and margins can be configured using the Preferences button at the top of the viewer.

3-5

7. Close the results viewer using the green EXIT Button at the top.

Transformed Section Properties

8. Click on the Section properties for drop down and select Transformed section. This will display the results shown below.

3-6

9. Click on the Results button to see the detailed results.

10. Close the results viewer.

11. Click on OK to close the Calculate Section Properties form.

Section Properties about a specified axis

For properties about a specific axis we need to define the origin of the section at the level of the required axis. One set of properties calculated are about the global axes.

12. Use the Data |Define Section... menu to open the Define Section form.

13. In the first row, change the Y coordinate to 200.

14. In the second row, change the Y coordinate to 200.

15. Click OK to close the Define Section form.

16. Use the Data |Define bars menu to open the Define Bars and Tendons form.

17. Click on the Edit bars... button.

18. Click once on the graphics window to the bottom left of the section, then move the mouse until the selection box contains all the bars. Click again to select the bars which will be highlighted in red. The Edit Reinforcement form will open.

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19. Click on the Edit Option drop down menu and select X-Y Translation.

20. Change the value in the Translation dimensions y field to 200.

21. Click on OK to move the tendons and close the Edit Reinforcement form.

22. Click on OK to close the Define Bars and Tendons form.

23. Use the Calculate |Analyse menu to open the Calculate Section Properties form.

24. Click on the Section properties for drop down and select Transformed section. This will display the results shown below.

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25. Click on the Results button to see the detailed results and scroll down the page until the table for Transformed Section area & Properties about global axes (through x=0,y=0): is shown

26. Close the results viewer.


28. Use the File |Save As... menu to open the Save As form.

29. Change the filename to My BS Example3_1a.sam And click on the Save button.

Net Transformed Section Properties

30. Use the menu item File |Open to open the file BS Example 2_2.sam created in example 2.2.

31. Use the menu item Data |Titles to open the Titles form. Change the Sub-title to Example 3.1b and the Job Number to 3.1b. Click on OK to close the Titles form.

32. Select the menu item Data |Analysis type |Section Properties.

33. Use the menu Calculate |Analyse to open the Calculate Section Properties form.

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34. Click on the Section properties for drop down list and select Net transformed Section (BS5400).

35. Click on the Transformed to drop down list and select MP1: C40 Es 31.0 fcc 0.5. This will display the results shown below:

36. Click OK to close the Calculate Section Properties form.


38. Change the filename to My BS Example 3_1b.sam And click on the Save button.

Plastic Section Properties

39. Use the menu item File |Open to open the file BS Example 2_4.sam created in example 2.4

40. Use the menu item Data |Titles to change the Sub-title to Example 3.1c and the Job Number to 3.1c. Click on OK to close the Titles form.

41. Select the menu item Data |Analysis type |Section Properties. Use the Calculate |Analyse menu to open the Calculate Section Properties form.

42. Click on the Section properties for: drop down and select Plastic section. Also set the Transformed to: field to the Structural Steel material. The form will now display the results shown below.

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43. Click on the Results button to see the detailed results for the Plastic Modulus of the Section.

The top of the results file is shown below

This indicates that to obtain the correct results for Plastic Moment and Plastic Modulus, according to the rules in BS5400 part 3 (9.7.1), we should change the gamma value for structural steel in the defined material properties from 1.05 to 1.0

44. Close the results viewer and the Calculate Section Properties form by clicking the OK button on the Calculate Section Properties form.

45. Use Data |Define Material properties... to open the Define Material Properties form and click on the Structural Steel property. Change the Material Partial Factor to 1.0 and then close both of the open forms with the OK button on each form.

46. Click on the Calculate |Analyse menu to open the Calculate Section Properties form. The form now displays the correct results.

3-11



49. Change the filename to My BS Example 3_1c.sam And click on the Save button.


Summary

The calculation of section properties is very easy, but very powerful as gross, transformed and cracked section properties can be obtained. The choice of which property to use will depend on the type of analysis to be performed using these properties. Reinforced concrete sections for Ultimate Limit State calculations will generally use gross properties whereas Composite steel and Prestressed concrete sections will normally be transformed. Net transformed properties (cracked) are most useful when considering the deflections of a reinforced concrete structure. Fully Plastic Moments and Modulus of a steel section are useful as input to a plastic hinge analysis of a structure and would be applied as Member Limits to a the program structural analysis.

3-13

3.2. Torsion & Shear Section Properties

Subjects Covered:

Torsion Constant; Shear Area; Shear Centre;

Outline

It is required to calculate torsion and shear section properties for three of the sections defined in section 2 as follows:

Calculate

The torsion constant for this voided slab section (taking 50% of the beam value as it is to be used in a grillage)

The torsion constant as above but ignore the continuous edges

(Use a torsion grid of 20 by 20)

Calculate

The transformed torsion constant for this encased column (transformed to concrete units)

(Use a torsion grid of 100 by 50 for the concrete and 100 by 200 for the steel column)

Calculate

The shear areas in both x and y direction

The shear centre coordinates

(Use a grid of 100 by 100)

Poissons Ratio = 0.3

3-14

Procedure

1. Start the program and use the menu item File|Open to open the file BS Example 2_2.sam created in example 2.2.

Voided Slab

2. Use the menu item Data|Titles to open the Titles form. Change the Sub-title to Example 3.2a and the Job Number to 3.2a. Click on OK to close the Titles form.

3. Use the menu Data|AnalysisType to set the analysis type to Torsion and shear.

4. Use the menu item Calculate|Analyse to open the Calculate Torsion and Shear form.

5. Click in the Divisions in X direction field and enter a value of 20. Click in the Y direction field and enter a value of 20.

6. Click on the Display results for drop down menu and select Torsion Stress Function from the list. Click on the Analyse button.

7. Click on the Results button to display the Results Viewer. Note that 50% of C = 1.3069E11mm4. Close the viewer.

8. Click the OK button to close the Calculate Torsion And Shear form.

9. Use the menu item Data|Define section to open the Define Section form.

10. On the first row of the table, click in the Library column and select Parametric Shape from the drop down list. This will open the Define Section Details form. Click on the OK button to automatically change the section to a discontinuous section.

11. Click on the OK button to close the Define Section form.

3-15

12. Use the Calculate|Analyse menu to open the Calculate Torsion And Shear form. Click on the Analyse button. Click on the Results button to display the Results Viewer.

Note that 50% of C = 0.66865E11mm4

13. Click on the OK button to close the Calculate Torsion And Shear form.

14. Use the File |Save As... menu to open the Save File form.

15. Change the filename to My BS Example 3_2a.sam and click on the Save button to save the data file.

Elliptically Encased Steel Column

16. Use the menu item File |Open to open the file BS Example 2_5.sam created following the steps in example 2.5.

17. Use the menu item Data |Titles to change the Sub-title to Example 3.2b and the Job Number to 3.2b. Click on the OK button to close the Titles form.

18. Use the Data |Analysis Type menu item to set the analysis type to Torsion and Shear.

19. Use the Calculate |Analyse menu to open the Calculate Torsion And Shear form.


21. Click on the Analyse button.

Note that the value of C in Concrete units is 1.89E10mm4.

3-16

22. Click in the Y direction field and enter a value of 200. Click in the Element to be analysed field and enter a value of 3 (this is the steel column).

23. Click on the Analyse button. Note that the value of C in Steel units is 5.57E6mm4. To convert this to concrete units we multiply by the modular ratio of the elastic modulus = 205/28 = 7.32

Therefore C of steel section in concrete units is 4.08E7

The combined C is the sum of the two components = 1.89E10

This is a lower bound value as it is assumed that in torsion, the two components are not acting compositely and warping is not constrained.

24. Click on the OK button to close the Calculate Torsion and Shear form.

25. Use the File |Save As... menu to open the Save File form.

26. Change the filename to My BS Example 3_2b.sam and click on the Save button to save the data file.

Shear Centre & Area of RC Edge Section

27. Use the menu item File |Open to open the file BS Example 2_1.sam created following the steps in example 2.1.

28. Use the menu item Data |Titles to change the Sub-title to Example 3.2c and the Job Number to 3.2c. Click on the OK button to close the Titles form.

29. Use the menu Data |Analysis Type to set the analysis type to Torsion and shear.

30. Use the menu item Calculate |Analyse, to open the Calculate Torsion and Shear form.


3-17

32. Click on the Display results for drop down menu and select Shear Stress Function from the list. Click on the Analyse button.

Note that the shear centre is given on the analysis form at coordinates (209, 207) and is shown by a symbol on the graphic display.

The shear area calculated, 63139mm2, is that associated with a shear force applied parallel to the y (vertical) axis.

The shear stress distribution due to a vertical force of 1kN can be shown graphically by changing Display results for: to Shear stress YZ (for vertical shear stresses) or Shear Stress XZ (for horizontal shear stresses) and clicking the Analyse button.

Close the Calculate Torsion And Shear data form with the OK button

To calculate the shear area in the X (Horizontal) direction, the section must be rotated around by 90 degrees. This is simply done by opening up the Define Section form using the menu Data | Define Section.... and entering 90 degrees in the Rotation column of the single component. The Hook point coordinates should also be set to (250, 0) so that the origin is in the same relative place. Close the Define Section form with the OK button.

33. Open up the Analysis form again, set Display results for: to Shear Stress Function and click on the Analyse button.

3-18

Note that the shear centre is given as (207, -209) which is the same as before except rotated by 90 degrees.

The shear area is, 92476mm2, and is that associated with a shear force applied parallel to the horizontal axis in the original section orientation.

Click on the OK button to close the Calculate Torsion and Shear form.

Use the File|Save As... menu to open the Save File form.

Change the filename to My BS Example 3_2c.sam and click on the Save button to save the data file.


Summary

The first example shows the effect on the torsion constant of including the specification of continuous edges. This almost doubles the value. The 50% value would be used in a grillage analysis because the transverse members would also have a torsion stiffness so the total torsion stiffness is split between longitudinal and transverse members (hence 50%).

The second example illustrates how to deal with sections made up from multiple components having different material properties. (If they were of the same material we could have just joined them). The program cannot deal with composite sections directly in one pass but if we make a few assumptions, many sections can be analysed by considering both sections separately and using a modular ratio to combine them into one torsion constant transformed to one of the materials.

The third example illustrates how to obtain shear stress distribution in a section with the shear centre coordinates and shear areas.

3-19

3.3. Differential Temperature

Subjects Covered:

BS5400 Temperature Profile; Restraining Moments; Primary differential temperature stresses; User defined profile.

Outline

The composite section shown above has been defined and saved in example 2.6 with a slight modification to include a 200mm by 200mm upstand on the left hand edge constructed with grade 40 concrete. The previously defined continuous face on this edge is made non-continuous. A standard temperature gradient, according to appendix C of BS5400, is applied to the section but it requires modifying it to take account of the upstand, as shown above. It is assumed that the temperature in the upstand will be constant and at the same value as that at the top of the slab. The effect of the reinforcement is to be included in the calculations. It is required to determine:

The overall restraining moments and axial forces for both positive and negative cases.

The unrestrained (self equilibrating) primary stresses at the top and bottom of each of the three components for both positive and negative cases.

Procedure

1. Start the program and click on the menu item File |Open... to open the file BS Example 2_6.sam created in section 2.6 of this guide.

2. Use the menu item Data |Titles to change the Sub-title to Example 3.3 - Differential Temperature and the Job Number to 3.3. Click on OK to close the Titles form.

3-20

3. Open the Define Section form using the menu item Data | Define Section...

Add Upstand Edge Detail

4. In the third row of the Library column select Parametric Shape from the dropdown list. This will display a secondary form (with graphic) showing a rectangular shape. Set the width and depth to 200mm then click on OK to close the form. The edge detail is positioned by setting Hook point 1 coordinates to (-750,200).

5. The material for the edge detail is set to grade 40 concrete using the drop down list in the Property column.

6. The left hand edge of the slab is made non-continuous by clicking on the slab component in the table, to get focus, then clicking on the left hand edge of the slab. This will change it from a dashed to a solid line. Click on OK to close the Define Section form.

7. Use the menu item Data |Analysis Type to set the analysis type to Differential Temperature.

Apply Temperature Profile

8. Select the menu item Data |Define Loads |Temperature |BS 5400 Part 2 Appendix C...

9. Click on the Group drop down and select Concrete deck on steel box, truss or plate girders. Set the Surfacing thickness to 0.05m. Click on OK to close the BS 5400 Part 2 Appendix C Temperature Profile form.

This shows a profile as defined in BS5400 Appendix C but the program assumes the top of the section is the top of the upstand. We therefore need to lower this profile so the top of it is aligned to the top of the slab. We also need to add a constant temperature portion from the top of the slab to the top of the upstand.

10. Select the menu item Data |Define Loads |Temperature |Defined Profile... This allows the temperature profile to be modified.

3-21

11. In the Positive Temperature Diff and Reverse Temperature Diff columns, change the height and temperature values to those shown below. It is easiest to start at the bottom of the list and work your way up.

Click on OK to close the Define Differential Temperature Profile form.

12. Select the menu item Calculate |Analyse and the program will automatically calculate the Relaxing moments and Axial loads, showing them on the displayed form. Untick the Ignore reinforcement? check box to include the effect of reinforcement in the calculations.

13. Click on the Results button to see all the results including the self equilibrating stresses.

3-22

14. Close the results viewer and click on OK on the Calculate Temperature Stresses form to close it.

15. Select the File |Save As... option and change the filename to My BS Example 3_3.sam then click on the Save button to save the updated section file.


Summary

This example shows how to define a user specific temperature profile on a composite steel/concrete section. If a beam, made up from this section and temperature profile, was fully constrained along its length then the following forces and moments would be induced along the span: Temp rise Temp fall

M Sagging F Comp M Sagging F Tension 370kNm 1228kN 269kNm -798kN

The self equilibrating Primary Stresses at the top and bottom of each component can be seen in the results shown above.

3-23

3.4. Early Thermal Cracking Calculations

Subjects Covered:

Thermal Strains; Restraint Factor; BD28/87; Reinforce faces on an elliptical surface; Short & Long term Temperature Fall.

Outline

The RC column section below is required to resist early thermal cracking stresses according to BD28/87.

The section is the outline of the encased column generated in Example2.5. It is necessary to remove the steel column (and void) before adding the 16 no 25mm reinforcing bars equally spaced around the perimeter with 50mm cover. To position the reinforcement symmetrically about the X axis, as shown, it is necessary to reinforce faces with 16 equally spaced bars, choosing the first face as one with a vertex on the x axis. Early thermal cracking calculations are to be done according to design guide BD 28/87 with the following parameters:

Short term temperature fall to represent that which would occur using 350Kg/m3 cement content and forming the section with 18mm plywood in the winter (Use the help file here)

Long term temperature fall in the winter

A restraint factor of 0.5 (Internal restraint)

Permissible Crack width for severe environment (Table 1 BS5400 part 4)

Ribbed bars are used for all reinforcement (Type 2 Deformed)

Shrinkage strain (modified by creep) has been calculated as -0.000085

Use recommended values for Ultimate tensile strain (-0.0002)

What is the reinforcement requirement to resist early thermal cracking?

3-24

Procedure

1. Start the program and click on the menu item File |Open to open the file BS Example 2_5.sam created in Example 2.5 of this guide.

2. Use the menu item Data |Titles to change the Section Title to Elliptical Reinforced Column, the Sub-title to Example 3.4 - Early Thermal Cracking and the Job Number to 3.4. Click on OK to close the Titles form.

Modify section and check vertex locations


4. Click on the second row in the Library column and press the Delete key on your keyboard to delete the void. Press the Delete key again to remove the steel beam.

5. Click on the first row in the Library column and select Define Shape from the drop down list. This opens up the Define Element Shape sub-form. Note the location of the vertex on the x axis.

6. Click on Cancel to close the Define Element Shape sub-form.


Define Bars Around Perimeter

8. Use the Data|Define Bars... menu item to open the Define Bars and Tendons form.

9. Click on the Generate drop down and select Reinforce face(s). Put 16 in the No. of bars field and set the Diameter to 25mm.

10. Click on the graphics window where there is a vertex on the x axis as shown below. Enter a value greater than the no. of segments in the boundary (100 say) in the No. of Faces field. Click on the OK button and a symmetrical pattern of reinforcement is created. Click on OK to close the Define Bars and Tendons form.

3-25

11. Use the Data |Analysis Type menu to set the analysis type to Early Thermal Cracking. The program displays the following warning message:

Click OK to close the warning message.

Remove Unused Material Properties

12. Use the Data |Define Material Properties menu to open the Define Material Properties form.

13. Double click on the fifth row in the Name column and press the Delete key on your keyboard to delete the structural steel material property. Click the OK button to close the Define Material Properties form.

14. Use the Data |Analysis Type menu to set the analysis type to Early Thermal Cracking.

Set the Analysis Parameters

15. Use the Calculate |Analyse menu to open the Early Thermal Cracking form.

16. Click on the Design Code drop down and select BD 28/87 from the list of available design codes.

17. Click on the Help button to open the help page for the form.

3-26

18. Click on the Locate Field Help button and select Short Term temp. fall T1 from the list. This will display the table below:

The value of T1 for 18mm plywood in winter with a cement content of 350kg/m3 is 27.

19. Look at the next section of the Help headed Long term temp. fall T2. It is recommended to use 10 degrees for winter concreting.

20. The field help for Permissible crack width suggests that Table 1 in BS5400 part 4 will give values for appropriate environmental conditions. For severe conditions the value is 0.25mm.

21. Close the Help window

22. Enter 27 in the Short term temp. Fall T1 field.

23. Enter 10 in the Long term temp. Fall T2 field.

24. Enter 0.5 in the Restraint Factor R field.

25. Enter -0.000085 in the Shrinkage Strain: field.

26. Enter 0.25 in the Permissible Crack Width: field.

27. All other values should be left at the default values.

28. The reinforcement area required is automatically calculated and shown on the Early Thermal Cracking form. The value is 1430mm2 as shown on the Early Thermal Cracking analysis form below. More detailed results can be obtained by clicking on the Results button and these can be printed or saved

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29. Click on the OK button to close the Early Thermal Cracking form.

30. Use the File|Save As... menu to open the Save File form.

31. Change the filename to My BS Example 3_4.sam and click on the Save button to save the data file.


Summary

The area of reinforcement calculated here is based upon the recommendations of DMRB document BD 28/37 and assumes a basic core of concrete 250mm from the surface of the section. This value can be changed if necessary. The restraint factor R has been chosen for an internal restraint (0.5) but this is not strictly correct as the least dimension of the column is greater than 1.0m, but if we assume it is correct for this exercise the process shows the basic principles that may be adopted. As this is an internal restraint the calculated reinforcement should be provided in both horizontal and vertical directions, but this can be provided by the reinforcement designed for other reasons. The vertical reinforcement is provided adequately by the main bars in the column. The horizontal bars would be provided in the form of links. If the column is 4.0m high and 10mm diameter links are used then the minimum link spacing required would be 4000/(1430/(pi*25)) = 220mm.

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3.5. ULS Capacity and stresses of an RC Section

Subjects Covered:

Reinforce faces; 1 bar by 2 covers; Nominal Load; Gamma factors; Biaxial bending; ULS Shear design; Iterations fail to converge

Outline

Ultimate limit state section capacities, for moments and axial force, are to be calculated for two of the sections defined in section 2 as follows:

This precast section has 7no. 25mm bars in the bottom faces with 50mm cover. The end bars have 50mm cover to the vertical faces. Additionally, 2no. 16mm bars are placed in the top of the upstand with 50mm cover to both faces.

The precast beam is lifted at its ends through the centroid of the section which generates a nominal Mx bending moment of 218kNm due to its self

weight (fl = 1.2 f3 = 1.1). Check that the Mx ULS capacity of the section exceeds this. What is the angle of the neutral axis?

The precast beam is stitched to a continuous insitu slab which forces the neutral axis to be horizontal. What is the Mx ULS capacity now?

By keeping the neutral axis horizontal there is an out of balance My moment which is resisted by a transverse membrane force in the slab. What is the value of this force if the beam is 10m long?

Save this section for use in other examples.

This column has a nominal concentric axial load of 1000kN together with a nominal My moment of 100kNm. What is the maximum additional nominal

Mx moment that can be applied at ULS. (fl = 1.2 f3 = 1.1)

The design moments and forces at ULS are

Mx = 350kNm

Axial = 1320kN

Shear along y = 180kN

What links of 10mm diameter are required? At what value of shear force will it be necessary to have additional links?

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Procedure

1. Start the program and use the menu item File |Open to open the file BS Example 2_1.sam created in section 2.1 of this manual.

Section 1

2. Use the menu item Data |Titles to change the Section Title to Grillage Edge Section with Reinforcement, the Sub-title to Example 3.5a and the Job Number to 3.5a. Click on OK to close the Titles form.

3. Change the analysis type using the Data |Analysis Type |Bending, Axial and Shear menu item.

Define Reinforcement

4. Open the Define Bars and Tendons form using the menu item Data |Define Bars...

5. Click on the Generate drop down menu and select Reinforce Face(s) from the list.

6. Click in the No. Of bars field and enter a value of 7.

7. Click in the Diameter field and enter a value of 25mm.

8. Click on the sloping bottom face of the section on the graphics window. The face will be highlighted in black and the Reinforcement along face(s) form will open.

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9. Click in the No. of faces field and enter a value of 2 (the default cover of 50mm is assumed) then click OK.

10. Click on the Generate drop down menu and select 1 bar by 2 covers from the list.

11. Click in the Diameter field and enter a value of 16mm.

12. Click on the left hand vertical and the top curved faces of the section on the graphics window. Both faces will be highlighted in black and the Locate bar by 2 covers form will open.

13. Enter values of 50mm in both the Cover to face 1 and Cover to face 2 fields then click OK.

14. Repeat 12 and 13 for the top right hand corner.

15. Click on OK to close the Define Bars and Tendons form.

Define Applied Forces

16. Open the Define loads form using the Data Define Loads |Applied Forces... menu item.

17. Click on the Insert record button to add a load case. Then click on the other Insert record button near the bottom of the form to add a row to the table at the bottom of the form.

18. On the first row of the table, click in the Type column and select X Moment from the drop down list.

19. Enter a value of 218kNm in the Nominal Load column.

20. Enter a value of 1.1 in the Ultimate f3 column.

21. Enter a value of 1.2 in the Ultimate fL column.

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22. Click on OK to close the Define loads form.

Calculate Capacity

23. Use the Calculate |Analyse menu to open the Bending, Axial and Shear form. The program displays the following Reinforcement is not fully yielded warning message:

This suggests that the section is over reinforced and the section fails at ULS by the crushing of the concrete

24. Click on the OK button to close this message.

25. Ensure that the Analysis type field is set to BS 5400 Ultimate Limit State. Click on the Loadcase drop down menu and select Loadcase: 1 from the list.

26. Click on the Capacity drop down menu and select X Moment Positive from the list.

27. Click on the Neutral Axis angle drop down menu and select Free from the list.

28. The limiting additional load is 177.417kNm. The neutral angle axis is 35.3527.

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29. Click on the Neutral Axis angle drop down menu and select Fixed horizontal from the list. The Reinforcement is not fully yielded warning message will appear again. Click on the OK button.

30. The limiting additional load is now 493.424kNm.

31. The associated My moment is -552.37kNm but this bending will be restrained by the membrane action in the adjoining slab. If the beam is 10m long and we assume a uniformly distributed membrane force acting in the interface between the edge beam and slab it will be 8* My/L2 = 44.2kN/m and will be compressive.

32. Click on the OK button to close the Bending, Axial and Shear form.

33. Use the File |Save As menu to open the Save File form.

34. Change the filename to My BS Example 3_5a.sam and click on the Save button to save the data file.

Section 2

35. Use the menu item File |Open to open the file BS Example 2_3.sam created in section 2.3 of this manual.

36. Use the menu item Data |Titles to change the the Sub-title to Example 3.5b and the Job Number to 3.5b. Click on OK to close the Titles form.

37. Change the analysis type to Bending, Axial and Shear using the Data |Analysis Type | Bending, Axial and Shear menu item.

Define Applied Forces

38. Open the Define loads form using the Data |Define Loads |Applied Forces... menu item.

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39. Click on the Insert record button to add a load case. Click on the other Insert record button near the bottom of the form to add a row to the table at the bottom of the form.

40. On the first row of the table, click in the Type column and select Axial from the drop down list. This will display the Eccentric Axial Loads form.

41. Click in the Axial load value: field and enter a value of 1000kN. For this exercise we are going to assume a short column with effective length of 0.0 so that no slenderness moments are generated. No eccentricity moments will be applied either.

42. Click on the OK button to close the Eccentric Axial Loads form.

It can be seen that applying an axial load also generates moment in both direction (0.0 in this case) to represent the slenderness and eccentricity moments.

43. Click on the Insert record button near the bottom of the form to add a fourth row to the table at the bottom of the form. On the new fourth row of the table on the Define loads form, click in the Type column and select Y Moment from the drop down list. Enter a value of 100kNm in the Nominal Load column.

44. For all rows in the table, enter values of 1.1 in the Ultimate f3 column and 1.2 in the Ultimate fL column.


46. Use the Calculate |Analyse menu to open the Bending, Axial and Shear form. Ensure that the Analysis type field is set to BS 5400 Ultimate Limit State. The Reinforcement is not fully yielded warning message will appear again. Click on the OK button.

47. Click on the Loadcase drop down menu and select Loadcase: 1 from the list. Click the OK button on the warning message.

48. Click on the Capacity drop down menu and select X Moment Positive from the list. Click the OK button on the warning message.

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49. The maximum additional Design Mx moment that can be applied is 441.21kNm. The max nominal moment is therefore 441.21/1.1/1.2 = 334.25kNm


51. Open the Define loads form using the Data|Define Loads|Applied Forces menu item.

52. Click on the Insert record button near the top of the form to add a load case and decline to copy the active load case.

53. The ULS design moment (as opposed to nominal moments) are entered directly into the top part of the table. In the second row, in the Mx column (under the Ultimate group) enter 350. Enter 1320 in the Ax column and enter 180 in the Vy column.


55. Use the Calculate |Analyse menu to open the Bending, Axial and Shear form. Click the OK button on the warning message.

56. Click on the Capacity drop down menu and select *Not used* from the list. Click the OK button on the warning message.

57. Tick the Shear Force Calcs check box.

58. Click on the Results button to display the Results Viewer.

59. Scroll to the bottom of the Results Viewer to find the Link arrangement. The links of 10mm diameter that are required are 314.316 for 2 legs and 628.633mm for 4 legs.

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The output shows the maximum spacing for columns is 384mm so we would use single links at 300mm spacing.

60. The links defined above are minimum reinforcement requirements as the actual shear stress v (1.0651N/mm2) is less than the value of vcrit (1.5372N/mm

2). This value of vcrit corresponds to a shear force of 259.78KN as shown on the Bending, Axial and Shear form. If the actual shear force exceeds this value then additional links will be required. The shear force must always be below 801.64kN no matter how much shear reinforcement is required


62. Use the File|Save As... menu to open the Save File form.

63. Change the filename to My BS Example 3_5b and click on the Save button to save the data file.

Section 3

64. Use the menu item File | Open to open the pre-prepared data file BS Example 3_5c.sam.

65. Ensure that the analysis type is set to Bending, Axial and Shear using the Data | Analysis Type menu item.

66. Use the Calculate | Anal

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