Thermal Analysis of a Steel Section (arbitrary)


This tutorial deals with the Thermal Analysis of an arbitrary Steel Section. The geometry of the cross section is entered graphically via cross-section editor CSE in SOFiPLUS.


A basic SOFiSTiK knowledge is required for this tutorial. Inside this tutorial we show only the project specific workflows, which are different from the basic workflow.


  • Define Cross Section via CSE

  • Prepare edges for fire loads

Project Description






Structural Steel

S 235

Cross sections





Rolled Steel

SHS 300 x 300 x 12

Design code

This tutorial is based on Eurocode DIN EN 1993.

Step by Step Instructions

Project Overview

  • Create a new SSD project based on DIN EN 1993

  • Create the required materials

  • Create a new solid cross section with task Cross Sections ‣ New Solid Section ‣ Composite or Steel

  • Generate Cross Section inside SOFiPLUS with Cross Section Editor

    • Insert a standard rolled steel profile into the current section

    • For Fire Design you have to save the mesh in a subdirectory

    • Save the section

  • In SSD insert the task Thermal Analysis

  • Define fire curve, time, protection class, etc.

  • With OK you can start the thermal analysis

Starting a new project

See chapter Start New Project in General Workflow description.

Defining materials

Generate all necessary materials listed above. Follow the procedures explained in chapter Material Definition in General Workflow description.

Defining cross sections

Follow instructions in Thermal Analysis of a Steel Section (I-Profile) until opted for cross section selection.

Insert a standard rolled steel profile into the current section.

New Rolled Steel Shapes

New Rolled Steel Shapes

Insertion point is (0.00, 0.00)

|SOF+| - Cross Section Editor

task_sofiplus_small SOFiPLUS(-X) - Cross Section Editor (click to enlarge)

Preparing edges for fire loads


For I-profiles there are already predefined flammable edges (Z-,Z+,Y-…). For other steel profiles, these edges still need to be defined.

  1. Use SOFIPLUS Panel ‣ Cross Section Editor ‣ Common Elements ‣ Rolled Steel Shapes (Explode) and select the steel section.

  2. Define boundary properties for the edges to allow for later application of fire loads by SOFIPLUS panel ‣ Boundary (Modify properties) and select edges relevant for the thermal analysis.

  3. Click Modify material properties ‣ New, enter a name and confirm with OK. Make sure to tick the box for ‘Temperature Environment’ in all property sets to initialize the edges for further calculation. The settings themselves will be handled in the task ‘Thermal Analysis’ in SSD.

  4. Repeat the previous steps as many times as needed. Note that there are two approaches, both with their own advantages and disadvantages:

    Method A:

    Define two property sets ‘FIRE’ and ‘NONE’ and assign the appropirate sets to your edges depending on your needs.

    Extended Material Values

    task_sofiplus_small SOFiPLUS(-X) - Extended Material Values (click to enlarge)


    This approach is easier to set up, but requires to go back into Cross Section Editor whenever the flamed edges change.

    Method B:

    Define individual property sets for each edge, similar to the unchanged I-section.


    This approach is more work initially, but allows for more flexibility when flamed edges change because it can be done directly in the ‘Thermal Analysis’ task.

Defining fire load via thermal analysis

The following steps are once again similar to Thermal Analysis of a Steel Section (I-Profile).