Unprotected Beam Temperature Curves
Next, we must define the temperature growth profile in the unprotected beams:
Unprotected steel will have a relatively rapid temperature increase. At present, Vulcan does not provide a means for analysing the temperature rise for heated components, but a variety of alternative ways are available for these to be specified.
In this example, the unprotected beams approximately follow the temperature of the Standard Fire Curve, with a slight reduction due to the thermal inertia of the steel (the temperatures were determined using a simple thermal model based on the equations in the Eurocodes). For this, we must generate a text file with the required temperature data included and then load it into Vulcan.
To generate a custom temperature curve:
In order to create your own temperature curve, you must create a text file using the correct format, as shown below:
This is a simple process and may be done using 'MS Notepad' or any similar text-editing software. For the curve data it is advisable to generate the time and temperature values using spreadsheet software, such as 'MS Excel'; cutting and pasting directly into the text file.
Sample data for the fire curves used in this example is available here.
To do this:
1. Open the "Properties | Temperature Curves" dialog box.
2. Select the 'Add' tab. A new curve (curve '2') is automatically generated.
3. In the 'Type' drop-down box, select the 'From File' option. Click the 'Browse' button and locate the required text file. A description of the curve will appear in the appropriate box and a graphical representation will be generated in the preview window:
4. Click the 'Attach' tab and select curve 2 from the drop-down menu. In the 'Attach to' section, choose the 'Beams' check-box.
5. In the main screen, select all of the steel beam elenents:
The entire structure is now regarded as being 'cold'. From this point forward, the elements that are not to be treated as 'cold' will have their own temperature curves defined and attached to them...