BRANZ TR8 Concrete floor systems
About this tool
TR8 is a specialist software tool used to predict the fire resistance of concrete beams and floor systems.
It supports the fire engineering design of reinforced and prestressed concrete floor systems where a required fire resistance rating must be demonstrated. The tool applies established structural engineering principles to assess how concrete elements perform when exposed to fire.
TR8 is based on BRANZ Technical Recommendation TR8 and is referenced in NZS 3101 (Concrete structures standard) as an acceptable calculation method for determining fire resistance of concrete floor systems.
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How to use this tool
TR8 is provided as downloadable software, with supporting guidance material.
To get started:
- Download and install the TR8 software
- Read the TR8 user guide to understand inputs, assumptions and outputs
- Enter details of the concrete floor or beam being analysed, including geometry, materials and reinforcement.
The tool can be used to assess concrete floor systems that:
- Are reinforced or prestressed
- Use normal‑weight or lightweight concrete
- Include slab, beam, or tee‑beam configurations
- Are simply supported or continuous over supports.
TR8 calculates fire resistance by modelling how structural capacity reduces as temperatures rise. Fire resistance is assessed as the time at which the element can no longer safely carry the applied load under fire conditions.
The software is intended for use alongside the supporting TR8 technical document, which explains the underlying theory and design approach.
Background
TR8 was developed by BRANZ to provide a rational, engineering‑based approach to fire resistance design for structural concrete elements.
The method considers:
- Material behaviour of concrete and steel at elevated temperatures
- Flexural failure as the governing mode
- Reduced loading conditions typically allowed in fire design
- Built‑in safety factors consistent with structural design standards.
It assumes that concrete has reached normal equilibrium moisture levels and that concrete spalling during fire is minimal. The tool has been validated through experimental comparisons with real fire test data.
TR8 is intended for trained practitioners and is most suitable for performance‑based fire engineering analysis rather than prescriptive design