Research in New Zealand is leading to advances in fire engineering design and protection. We look at some of the work under way at BRANZ and the universities.
THE MAJOR RESEARCH EFFORT BY BRANZ and The University of Canterbury to develop a risk-informed design fire tool for fire safety engineering is nearing completion with the B-RISK software entering a beta testing phase.
Experimental results ensure accuracy
A practical issue for the research project team has been getting suitable data to test the tool – experimental results that can be compared against the B-RISK modelling prediction.
Recently approved funding from the Ministry of Business, Innovation and Employment has allowed the team to conduct an experimental programme to generate this data.
The B-RISK tool estimates what size fire could occur in a room by populating the room with combustible objects from a database of typical items in buildings.
From this, it simulates how the fire in the room will grow and develop as it spreads among the objects.
B-RISK requires information about each of the objects, such as how easily the item will ignite and how large the associated fire will be.
The experiments are generating data for the modelling of room-scale configurations. Results will be compared with B-RISK predictions for the identical configuration to ensure the accuracy of the new tool.
The experiments involve three materials:
- Polyurethane foam – used in upholstered furniture.
- Medium-density fibreboard (MDF) – used for cabinetry.
- Acrylonitrile butadiene styrene (ABS) – used for casing electronic goods.
The experimental programme uses reaction-to-fire testing equipment in the BRANZ laboratories to undertake a range of experiments:
- A series of bench-scale experiments using the cone calorimeter to determine the ignitability of the three materials.
- A series of real-scale tests on items made from the three materials in the furniture calorimeter to determine the fire size of each item (see Figure 1). This information will be used as item property data for the modelling of full-scale multi-item layouts in the standard ISO 9705 room.
- The same multi-item fire experiments in the ISO 9705 room, to compare the results to the B-RISK predictions.
Spill plumes widen application
The effects of balcony spill plumes are also being included in B-RISK with the assistance of Dr Roger Harrison. Spill plumes occur when smoke from a fire flows beneath an upper balcony construction and mixes with air, increasing the smoke volume as it spills around the balcony edge and rises to the ceiling in the adjacent space (see Figure 2).
The inclusion of spill plumes in B-RISK extends the applicability of the model to large public spaces such as atriums and shopping malls. Overestimating smoke production volumes in these can result in costly mechanical extraction equipment, while underestimation can lead to unsafe conditions in the event of a fire.
Compatible with Code changes
Along with new capability to include uncertainty estimates and sensitivity analysis, the fire design tool has been developed to be compatible with the new Building Code Verification Method (C/VM2) Framework for fire safety design. This allows modelling and calculation demonstrating Building Code compliance to be carried out more efficiently.
The Verification Method ensures more consistent design assumptions and safety outcomes by engineers undertaking performance-based fire design than before – design fire loadings and quantitative performance criteria weren’t previously published.
Launch in early 2013
Following the beta testing phase in the last quarter of 2012 where feedback and input will be sought from potential end-users, BRANZ plans to launch the B-RISK tool with a series of training seminars and workshops in March 2013.
- enabling secondary beams to be solid web or to have multiple closely spaced web openings
- amending the detailing requirements for the floor system to remove impractical requirements such as congestion of reinforcement in the slab panel corners
- rewriting the 2006 software to make it more user-friendly.
Victoria University of Wellington
A student is researching the fire safety implications of green or sustainable building features. To date, the most negative impacts appear to be atriums and double-skin façades. Atriums have well developed mitigation measures for fire safety, but double-skin façades do not. Features such as low volatile organic compound (VOC) paints have positive fire safety impacts, and many have no or little impact.
Researchers have also been working with GNS modelling post-earthquake fire spread in Wellington.
For full details of this research project, see www.branzfire.com/frst/.
This 5-year research programme has been funded by the Building Research Levy and the Ministry of Building, Innovation and Employment.
Articles are correct at the time of publication but may have since become outdated.