Vulcan is a three-dimensional frame analysis program, which has been developed mainly to model the behaviour of skeletal steel and composite frames, including the floor slabs, under fire conditions. Temperature distributions across members can be non-uniform, causing differential thermal expansion and a spread of elastic and inelastic properties across the section, and a range of cross-sections can be defined, allowing different shapes and materials to be represented.
The structure is modelled as an assembly of finite beam-column, spring, shear connector and slab elements. It is assumed that the nodes of these different types of element are defined in a common fixed reference plane, which is assumed to coincide with the mid-surface of the concrete slab element. The beam-columns are represented by 3-noded line elements. The cross-section of each element is divided into a number of segments to allow variations in the temperature, stress and strain through the cross-section to be represented. Both geometric and material non-linearities are included. To represent the characteristics of steel-to-steel connections in a frame, a 2-noded spring element of zero length, with the same nodal degrees of freedom as a beam-column element, is used. The interaction of steel beams and concrete slabs within a composite floor is represented using a linking two-noded shear-connector element of zero length, with three translational and two rotational degrees of freedom at each node.
The analysis includes geometric non-linearity in the slabs, using a quadrilateral 9-noded higher-order isoparametric element. This includes a modified layered orthotropic formulation based on Mindlin/Reissner theory, and using an effective stiffness model to model the ribbed nature of typical composite slabs. The temperature and temperature dependent material properties can be specified independently. A maximum-strain failure criterion has been adopted for the concrete, and a smeared model has been used in calculating element properties after cracking or crushing. After the initiation of cracking in a single direction, concrete is treated as an orthotropic material with principal axes parallel and perpendicular to the cracking direction. Upon further loading of singly cracked concrete, if the tensile strain in the direction parallel to the first set of smeared cracks is greater than the maximum tensile strain then a second set of cracks forms. After compressive crushing, concrete is assumed to lose all stiffness. The uniaxial properties of concrete and reinforcing steel at elevated temperatures, specified in EC4, have been adopted in this model.
Vulcan is a unique Structural Fire Engineering tool which delivers technical excellence in an easy to use Windows format on a desk-top. It represents an excellent synergy between engineering software and academic research.
- Geometries and user inputs are created visually in a Windows based user interface
- Users are able to input models directly or import them from CAD
- The user interface is fully functional and provides graphical output
- It is not necessary to edit complex data files