Beam Definition

In theory only three different design beams (one internal, one north edge and one south edge) are require as the spans and carriageway are completely symmetrical. This is only true if the beam directions can be reversed, which is ok for a refined analysis but unfortunately not for a line beam analysis.

So, four beams are required, one edge and one inner for each span (The north edge in span 1 can also be used for the south edge of span 2 and vice versa). Initially we will create the inner beam for span 1.

(If not continuing from last section, open "EU Example 10_1 Materials.sst" via Help | Tutorials | Open Tutorial Model... from the main menu.)

1. In the Design Beams navigation window click on the toolbar button to select New Pre-tensioned Prestressed beam from the available list.

2. The Beam length is “21m” and Location is “Interior beam”. Cross section is “varying” and No. of different sections is “2”.

3. Use the Suggest size of: dropdown to select “Y Beam” which will open the Initial Sizing sub form.

4. On the sub form set the Beams at: “2000 centres” and select the “Y7” beam type.

5. Click ✓ OK on the sub-form.

6. Select “Section 1” in the Define field, click the table insert + button, select “In situ – regular” component, and define width 2000 x depth 200mm.

7. Click ✓ OK on the sub form and ensure that the Z offset of the slab is 1270mm.

8. Click the Merge by stage # button and click on the vertical edges of this slab component in the graphics window to ensure that it is continuous.

   

9. Also check that the Stage for the slab is set to “Stage 1A”.

10. The Concrete Property for the beam and slab should be C50/60 and C32/40 respectively. Close the section definition form with ✓ OK.

11. For “Section 2” the program assumes the same section as section 1 so just change Stage for the slab to “Stage 1B”. Note that for both beams the age of the precast concrete is 4 days at transfer and 60 days when it is made composite with the slab.

12. Click ✓ OK on the Pre-tensioned Beam Section Definition form.

    

13. To define the reinforcement, select “Reinforcement” in the Define field.

14. Click the + button near the bottom of the form to open the Define Reinforcement form.

15. Set the fields to those as shown on the right-hand part of the Define Reinforcement sub form and define the cover as 50mm when clicking on the top face of the slab to define the bars.

    

16. Close both the Reinforcement along face(s) sub form and the Define Reinforcement sub form with ✓ OK.

17. On the Define Pre-Tensioned Beam Reinforcement form, highlight all 10 rows in the table (<Ctrl A>) and click on the Edit icon near the bottom of the form to open the Edit Reinforcement Attributes form.

18. Tick the Modify? tickbox and enter “15” in the Dimension/Start field.

19. Close both the Edit Reinforcement Attributes form and the Define Pre-Tensioned Beam Reinforcement form with ✓ OK.

20. Select “Section Locations” in the Define field and set the values as shown below in the Beam Feature Definition sub-form. (Use the table insert + button to add the additional rows).

    

21. Close this sub-form and the Pre-tensioned Beam Definition form with ✓ OK.

    Parameters that affect differential temperature calculations and time dependant effects are also stored with the beam data so these can be defined now.

22. In the Design Beams navigation window, select the defined prestressed beam and then click on the toolbar Analysis button to open the Pre-tensioned Beam Analysis form.

23. Click on the Analyse for drop down and select “Differential temperature primary stresses” to open the Differential Temperature Analysis sub form.

24. Set the Type of Deck field to “Type 3b: concrete beams”, the Surfacing field to “Surfaced” and the surface thickness to “0.075mm”. The resulting diff temp profile can be seen in both the table and the graphic.

25. Close this form with ✓ OK.

26. Click on the Set parameters for drop down and select “Time dependent effect calculations”.

27. On the Time Dependent Effect Calculation sub form set the value in the Age (in days)... field to “2” and ensure that all the other values are set to those shown below.

28. Click ✓ OK to close this sub form.

    

29. Finally, click ✓ OK to close the Pre-tensioned Beam Analysis form. Save the file as “My EU Example 10_1 First Beam.sst”.

Other Beams

It is now necessary to copy and modify this beam to create the three other beams.

30. With the first beam selected (SB1: Pre-tensioned Prestressed) right mouse click in the navigation window to Rename this beam “Inner Beam Span 1”.
31. Right mouse click again and select Copy from the list of options.
32. Right mouse click again and select Reverse to reverse the direction of the in-span features.
33. Right mouse click yet again to Rename the new beam “Inner Beam Span 2”.
34. To create the north edge beam of span 1, first copy “Inner Beam Span 1 and then open the Beam Definition form for the new beam.
35. Change the Location to “Exterior Beam”.
36. Open the section definition for “Section 1” and make the following changes:
    • Change the Y7 Beam to a YE7 beam (re-select "PC beam - standard", then change "Concrete Beam Range" and "Reference Within Range"), answering "yes" when prompted to update section 2 for this and following changes
    • Change the In-situ slab to a 1500 by 200 section (select "Insitu - regular")
    • Change the y offset for the slab to 250
    • Define an additional In-situ regular section (Stage 2) 200 by 500
    • Set the offsets for this parapet to (-600, 1270)
    • Merge by stage #
    • Do the same for Section 2 where necessary (if selected yes when prompted to "Update Section 2", the parapet should be added)
37. Delete the two reinforcing bars that are now outside the boundary of the section.
38. Rename the beam as “Edge Beam Span 1”.
39. The north edge beam of span 2 can be created by simply copying “Edge Beam Span 1”, reversing it and renaming it.
40. For completeness the differential temperature profile for each of the edge beams needs modifying to take into account the parapet edge. This is done by changing the profile Type to “User Defined” and then adjusting the table values (by copy-paste) as shown below:

41. Save the file as “My EU Example 10_1 Created_Beams.sst”.