STRUKTRA™ Structural Thermal Breaks

STRUKTRA™ Structural Thermal Breaks take the form of flat plates of any dimensions, which provide Architects with complete design freedom and Structural Engineers the capability to design to standard codes, with a simple configuration.

Farrat offer three independently tested Structural Thermal Break materials, which are designed to balance high structural performance and low thermal conductivity:

1. STRUKTRA™ TBK (Yellow) is most specified across typical connection details, with high compressive strength (312MPa fck) and the best thermal performance in the range (0.187 W/mK).
2. STRUKTRA™ TBF (silver) is the optimum material when fire performance is a consideration, such as within high-rise buildings, due to its high compressive strength (355MPa fck) and low thermal conductivity (0.2 W/mK) performance characteristics, supported by an A2, s1,d0 Non-Combustible Classification.

Designing with STRUKTRA™ materials is directly aligned to the processes involved in designing the connection itself. The high structural and thermal performance of STRUKTRA™ TBF & TBK means that connection numbers and sizes can be reduced without compromise to performance in comparison to other mechanical solutions and without the need to use specialist design tools.

A breakdown of what to consider when designing structural steel connections is contained within the Farrat Structural Thermal Break Technical Guide and supporting SCI, Steel Construction Institute assessment document.

As an overview:

1.  Structural Thermal Break plates should be considered as a “pack” in terms of connection design.
2. All Shear forces need to be accommodated by the connection bolts. As a result of the multiple layers in the connection the grip length of the bolts may be significantly increased, it may also be necessary to reduce the anticipated shear resistance of the bolts in the connection.
3. Reference should be made to BS EN 1993-3 1-8: 2005 Eurocode 3. Design of steel structures.

For ease when detailing, the Farrat extension for Tekla Structures creates Farrat Structural Thermal Break connection plates. The component automatically takes the plate dimensions and holes of the plate it is fixing to.

The exact physical and mechanical properties for Farrat Structural Thermal Breaks are contained in the Farrat Structural Thermal Break Technical Guide.

As a quick guide:

1. Farrat TBF and Farrat TBK materials offer compressive strength comparable with Steel.
2. Structural Thermal Break plates in a connection should only be designed to resist compressive forces.
3. Consideration should also be taken of compressive creep. Farrat materials are formulated to resist long term creep, but this element should be factored into any design.
4. Many materials which exhibit good thermal properties have poor long term creep profiles.
5. Reference should be made to BS EN 1993-3 1-8: 2005 Eurocode 3. Design of steel structures.

The coefficient of friction of a thermal break plate is not a relevant property for the structural design of connections with non-pre-loaded bolts.

Whilst figures for frictional resistance of Farrat Structural Thermal Breaks can be obtained, it will differ depending on the material with which it is in contact and should be treated with caution when designing connections involving Preloaded or TCB bolts.

Structural steel connections that require a 120-minute fire rating will typically need to be protected with either an intumescent coating system or a fire protection board. In all situations, the Structural Thermal Breaks should receive the same level of protection as the steel.

However, Farrat TBF Structural Thermal Breaks have been tested unprotected in fire conditions, in structural steel connections, to temperatures more than 1000°C for 120 minutes and maintained structural integrity.

Different building types and legislators have differing technical and regulatory requirements for fire design, but if fire is a concern that requires addressing, then the use of non-combustible thermal breaks is one way to mitigate that risk.