Aaron Nicholson Beca

by Aaron Nicholson C/VM2 Design vs Non C/VM2 Performance Based Design

Outline – Building Code changes – One building - months apart Geometry C/VM2 vs PBD – what is different C/VM2 vs PBD – what is the same – Risk and Responsibility Discussion points

September 2010 “Proposed changes to Building Code Requirements and associated documents for protection from fire” issued by the DBH for public comment.

September 2010 “Public consultation during the Building Code review established that the level of fire safety currently provided in the building code and the associated Compliance Document is right…”

September 2010 “No change is proposed to the existing minimum level of fire safety required under the Building Code. As a result, there should be no additional costs to the building sector arising from the proposals in either design or construction”.

Building Code Changes April 2012 new C1 to C6 clauses replaced C1 to C4 clauses One aim was to make the building code more specific and quantifiable in the level of protection from fire which is required The changes were supported in part by the introduction of a new Verification Method C/VM2

Building Code Changes Important: The Building Code can still be met in three ways: Full compliance with C/AS1-7 (as applicable) Full compliance with C/VM2 Performance based design solution

Case Study: One building months apart Ground floor

First floor

Second floor

C/VM2 vs PBD – what is the same? FEB process to agree approach, methodology, inputs and tenability criteria Actual Tenability criteria FED CO 0.3, FED Thermal 0.3, Visibility 10m, Assessment height – 2m Fire and or Egress modelling required Peer review

C/VM2 vs PBD – what is different? Actual Inputs Prescribed rather than proposed and agreed Assessed tenability criteria Visibility not considered under C/VM2

PBD for this building: Visibility was the first of the tenability criteria to fail (ASET) at 95 Seconds from ignition Extension of ASET achieved by smoke curtains around voids and mechanical extract from voids Extended ASET failed at 280 seconds which was greater than RSET and therefore complied.

CVM2 Design for this building : Visibility was not considered as the building is sprinklered and less than 1000 occupants FED CO of 0.3 was not exceeded for in excess of 600 Seconds from ignition If visibility were assessed? It failed at 95 Seconds from ignition

Differences in compliant designs: PBD: Sprinklers throughout Smoke detection throughout Smoke curtains around voids Extract from voids – required due to modelling leakage through curtains CVM2 design: Sprinklers throughout Smoke detection throughout

Questions raised: Were we overdesigning buildings pre building code change? Are we now potentially under designing buildings in certain situations? How often does this situation arise? Have we therefore stepped outside of one of the original “Statement of Proposals” which was that “No change is proposed to the existing minimum level of fire safety required under the Building Code”. As a Chartered Professional Engineer where do I sit ethically knowing that visibility is not considered? Where do I sit legally – C/VM2 is deemed to satisfy so I’m safe right. What is the risk to the engineer professionally? What is the risk to the occupants of the building? Who is responsible?

Questions or comments?