Técnicas de procesamiento y análisis de datos

Modify Materials Loaded from the Template

5. Next we will change the material properties loaded from the template.

Click on the Data |Define Material Properties... menu to open the Define Material Properties form. Double-click in the Name column on row 5 (Structural Steel material) then press the Delete key on your keyboard to delete the redundant material property.

Click in the Name column on row 1 to open the concrete material properties.

Change the Characteristic strength, f’c to “50MPa”. Click “OK” to close the Define Property Details form. Click in the Name column on row 2 to open the other concrete material properties. Ensure that the Characteristic strength, f’c is set to “40MPa”. Click “OK” to close the Define Property Details form.

Click in the Name column on row 4 to open the prestress material properties.

Ensure that the Tensile strength, fp is set to “1750MPa”, the Initial Prestress Force to “75%”. Change Maximum Relaxation After 1000 Hours to “7%” and the Relaxation at Transfer to “50%” (note: this is 50% of the total relaxation loss).

Click “OK” on both forms to save the new material properties.

6. The next step is to define the geometry of the beam.

Click on the Data|Define Beam... menu item to open the Pre-tensioned Beam Definition form. In the Beam length field, enter a value of “22m”. Make sure Cross section is is set to “Uniform” and Location is is set to “Interior beam”.

Suggest Section Size

7. Next we will briefly look at how we can get the program to suggest a sizing for the beam cross section.

4-5

Click on the Suggest size of drop down and select “Super T-Girder” from the list of options. This will open the Pre-tensioned Beam Initial Sizing form.

The form shows that a 1000mm Deep Super-T Type T2-2 T2 Girder may be a suitable initial size for this beam. However, this beam type is not going to be used in this particular example, so click “Cancel” to close the sub-form without selecting the beam.

Define Beam & Slab

8. Click on the Define drop down and select “Section” from the list of options.

This will open the Pre-tensioned Beam Section Definition form. Click on the Component column in the first row of the table and select “PC Beam - Standard”. This will open the Define Precast Beam Component form.

Click on the Concrete beam range drop down and select “Super-T Girder” from the list of options. Click on the Shape no. within range drop down and select

“T3-2 Open Top” (this is the 1200m Deep girder to AS5100.5 Appendix B shape definition) from the list of options. Click “OK” to close the sub-form.

The default beam has a 2100mm wide top flange. To reduce this to 2000mm wide for this example, from the Pre-tensioned Beam Section Definition form click on the Component column in the first row of the table and select “PC Beam - define”. This will open the Define PC Beam form. Edit the flange dimensions to suite a 2000mm wide flange. Click “OK” to close the sub-form.

9. The next step is to define the slab.

Click on the Component column in the second row of the table and select “In situ – regular”. This will open the Define Precast Beam Component form. The Shape Reference will be set to “Rectangle” already so enter “2000mm” in the width field and “200mm” in the depth field then click “OK”.

4-6

Ensure that the Y offset for the slab is set to “1200”, putting the slab in the correct location.

Check that the Transfer Property for the beam and the Final Property for the slab are both set to grade 40 and the Final Property for the beam is set to grade 50, then click on the “OK” button to close the Pre-tensioned Beam Section Definition form. Click on “OK” to close the Pre-tensioned Beam Definition form.

10. Finally we will save the beam file.

Click on the File |Save as... menu item and save the file as “My AU Example 4_1.sam”.

11. Close the program.

Summary

This example shows how to enter a simple pretensioned prestressed beam into Autodesk^® Structural Bridge Design 2014. A default Super-T shape is defined and the method of editing the default shape is described. The construction stages are defined, being the precast beam and a single stage composite deck construction. The properties of the concrete at each stage of construction are defined using the program defaults. Tendon definition is also produced in the program default locations.

4-7

4.2. Prestress Beam Definition (Advanced)

Prestress beam; Edge beam; Exterior beam; Varying cross section; Merge by stage;

Edge upstand; Section locations; Remove unwanted tendons; Debond tendons;

Define reinforcement; Curtail of reinforcement Outline shape beam with just 4 tendons in the top of the beam and four at transfer). The concrete strength at transfer is 35 MPa.

4-8

The slab is cast in two stages: the first (Stage 1a) being the central 10m portion and the second (stage 1b) being the two end slabs being 6m from each end (this staging reduces the mid span stresses as composite action is achieved prior to casting the end slabs). The kerb upstand (stage 2) is then added as an additional stage and is cast along the complete length. All insitu concrete is grade 40.

Reinforcement is placed in the composite slab (N16-200 Top and Bottom). The top layer of slab reinforcement is curtailed such that it extends 7.0m into the slab form both ends.

Reinforcement is also in the side faces of the webs (5/N16) as