Single Point of Failure and Inter-relationship between Stair Pressurisation System and Evacuation Strategy for Tall Buildings

Transcription

1 5 th International Tall Building Fire safety Conference 19 June 2018 Single Point of Failure and Inter-relationship between Stair Pressurisation System and Evacuation Strategy for Tall Buildings M.C. Hui (CEng, CPEng, FIFireE, MSFPE, MIEAust) Fire Engineering Manager BCA Logic Pty Ltd

2 Contents Overview of occupant fire safety strategy Review egress provisions for buildings Single point of failure in egress system and protection options Pressurisation of escape stairs Inter-relationship between stair pressurisation and egress strategy Conclusions 2 of 21

3 WHY Occupant DO WE Fire NEED Safety TO Strategy PROVIDE A Our homes are our castles 3 of 21

4 WHY Provision DO WE of NEED Exits TO PROVIDE A Minimum number of exits (Hagiwara and Tanaka, 4 th IAFSS Proceedings, pp , 1994) USA International Building Code of 21

5 WHY Provision DO WE of NEED Multiple TO Exits PROVIDE Why? A Provide redundancy if one exit becomes unavailable, then there is an alternative exit. Reduce queuing time when there is a large population on the floor. 5 of 21

6 WHY Provision DO WE of NEED Multiple TO Exits PROVIDE The Inevitable A Layout The two stair entries are at 4.3m to 5.8m apart 6 of 21

7 Distance Between Alternative Exits Building Code of Australia (Class 2 to Class 9 Buildings) 2016 edition 7 of 21

8 Distance Between Alternative Exits Approved Document B (Buildings other than Dwellinghouses) 2006 edition including 2010 & 2013 amendments 8 of 21

9 The Blind Spot (Single Point of Failure) When the common corridor is significantly smoke logged, no occupants can reach the exit stairs 9 of 21

10 Options to Protect The Common Corridor Self-closing fire doors for the units Self-closing fire doors for the units complete with medium temperature smoke seals and intumescent fire seals Ventilating the corridor Smoke exhaust system for the corridor Pressurise the corridor Sub-dividing the corridor by fire door or smoke proof walls does not protect the corridor but discriminates a portion of the occupants on the floor! 10 of 21

11 The Escape Stair Is this the safe haven? Stair can be non-fire-isolated (Building Code of Australia) Connects not more than 3 consecutive storeys in apartment buildings, plus an extra storey if such storey is for car parking or other ancillary purposes Connects not more than 2 consecutive storeys in hotels, motels, hostels and the like, plus an extra storey if such storey is for car parking or other ancillary purposes Connects not more than 2 consecutive storeys of non-patient care areas in health-care buildings 11 of 21

12 The Escape Stair Is this the safe haven? Under the BCA, a stair does not need to be pressurised if it does not serve any storey above an effective height of 25m more than 2 below ground storeys an atrium a health-care or aged care building with a rise in storeys of not more than 2 12 of 21

13 Pressurised Escape Stair Requirements on pressure within the stair, velocity across the stair entry door, and door opening force vary amongst countries. The more important issue how many stair entry doors are assumed to be open in the stair pressurisation system design. 13 of 21

14 Pressurised Escape Stair AS/NZS :2015 Zone pressurisation dependent system or hot layer smoke control system: Fire stair entry door from fire-affected compartment Main discharge door from fire stair Air purge system, shutdown system and carpark ventilation system: Fire stair entry door from fire-affected compartment Door immediately above/adjacent to the fire-affected compartment Main discharge door from fire stair 14 of 21

15 Pressurised Escape Stair BS EN :2005 System Examples of use Design conditions A For means of escape. Defend in place Stair entry door on fire floor B C For means of escape and firefighting (lift shaft also pressurised) For means of escape by simultaneous evacuation Stair entry door on fire floor and floor above, door to lift lobby, final exit door Stair entry door on fire floor or final exit door D For means of escape. Sleeping risk Stair entry door on fire floor and final exit door E For means of escape by phased evacuation Stair entry door on fire floor and floor above, and final exit door 15 of 21

16 Pressurised Escape Stair NFPA and NFPA Number of doors assumed to be open is up to the stair pressurisation system designer. 16 of 21

17 WHY How DO does WE Stair NEED Pressurisation TO PROVIDE System A Work Building leakage 1.0 m/s Relief Ref: John H. Klote, Smoke Control in SFPE Handbook of Fire Protection Engineering, 5 th edition, Chapter 50, of 21

18 Occupant Evacuation Strategy and its Interrelationship SMOKE with Stair EXHAUST Pressurisation SYSTEM? System Highrise residential buildings Potentially long pre-movement times and no particular evacuation pattern Proulx and Fahy, Fire Safety Science Proceedings of the 5 th International Symposium, pp , of 21

19 Occupant Evacuation Strategy and its Interrelationship SMOKE with Stair EXHAUST Pressurisation SYSTEM? System Highrise buildings (other than private residential) Managed evacuation: Is the evacuation strategy compatible with the stair pressurisation system assumptions? Particular tenancy Work Health and Safety requirement: The evacuation protocol may pose significant challenges on the stair pressurisation system. 19 of 21

20 WHY Conclusions DO WE NEED TO PROVIDE A The path of travel to the fire escape stairs needs to be protected from the effect of fire and smoke to facilitate occupant evacuation, not just the stairs. Stair pressurisation system design must take into account the occupant evacuation strategy implemented for the building which dictates the number of stair entry doors being open at the same time, not just following the national engineering standards. 20 of 21

21 QUESTIONS? THANK YOU FOR NOT FALLING ASLEEP 21 of 21