act on fire! bca compliance and fire safety engineering€¦ · · 2016-09-17bca compliance and...

ACT on fire!BCA compliance and fire safety engineeringCanberra Rex Hotel

150 Northbourne Avenue, Braddon

5 August 2015

Outline

• Defire

• Building legislation

• National Construction Code – Building Code of Australia (BCA)

• Alternative solutions (fire and non‐fire related)

• Smoke control systems

– Enclosure of shafts

– Smoke damper vs fire damper requirements

– Air pressurisation systems

– Impulse fans in carparks

– Open deck carparks

• Zone and computational fluid dynamics (CFD) fire models

• Evacuation models

• Summary of alternative solution process

Defire – our team

Legislative requirements

The BCA is empowered by various State, Territory andCommonwealth building legislation.• The general rules of building legislation require:

– All new buildings to comply with the BCA in force at the time of building approval / construction certificate stage.

– All new building works must also comply and not reduce the safety of the existing building.

– Where the works exceed 50% of the volume / area –depending on the State or Territory – of the existing building, then the entire building may need to comply.

– Similar rules apply in other States, Territories and Commonwealth jurisdictions – ie Defence.

Legislative requirements - QLD

The Governing document pertinent to fire engineers in QLD is Building Act 1975:• Clause 30 – requires new works to comply with the BCA and

any relevant portions of the QDC.

• Clause 81 ‐ for most existing buildings full compliance istriggered for alterations and additions if the:

– alterations affect more than 50% of the volume including any works completed in the previous three years

– certifier determines works pose a risk to safety of occupants or risk of fire spread to adjoining buildings

Legislative requirements – NSW (continued)

Under clause 94 of the EPAR 2000, the local consent authority may require certain buildings to be upgraded. This includes buildings in which:

• The proposed building work together with any other building work completed orauthorised in the last three years represents more than half the total volume ofthe building measured over its roof and external walls,

• The measures within the building are inadequate:

– To protect persons using the building, and to facilitate their egress from the building in the event of a fire

– To restrict the spread of fire from the building to other buildings nearby.

In determining an application to which this clause applies, a consent authority may take into consideration whether it would be appropriate to require the existing building to be brought into partial or total conformity with the BCA.

Legislative requirements – ACT

Substantial alteration—Act, s 29 (2) (a)(1) An alteration of a building is a substantial alteration if, during the 3 years immediately before the day the application for building approval for the alteration is made –

(a) for a class 1 building—the total floor area of the proposed alteration, not including any internal alteration, is more than 50% of the floor area of the original building; and(b) for a class 2, 3, 4, 5, 6, 7, 8 or 9 building—the total floor area of the proposed alteration, including any other alteration, is more than 50% of the floor area of the original building.

(2) However, neither refitting a building nor replacing the internal elements of the building is an alteration of the building unless the layout and function of the internal spaces of the building are changed.’

BCA - Hierarchy

Compliance with the BCA is achieved by meeting the performance requirements. This is done by either complying with the deemed‐to‐satisfy (DTS) provisions or by alternative solutions or more commonly a combination of both methods.

BCA - Alternative solution report structure

• Where an alternative solution is proposed to address adeparture to the deemed‐to‐satisfy (DTS) provisions of theBCA, the alternative solution must demonstrate compliancewith the performance requirements of that code.

• The alternative solution must detail the methodology ofmeeting the performance requirements of the BCA, inparticular clauses A0.5, A0.9 and A0.10.

• The development of fire‐related alternative solutions shouldalso be in accordance with the International FireEngineering Guidelines 2005 (IFEG).

International Fire Engineering Guidelines

• Methodology for delivery of fire safety engineered design solutions

• FEBs & FERs

• Endorsed by:• AFAC

• AIBS

• SFS

BCA – typical objective

Part E2 – Smoke hazard management

EO2The objective of this part is to –

a) safeguard occupants from illness or injury by warning them of a fire so that they may safely evacuate, and

b) safeguard occupants from illness or injury while evacuating a building during a fire.

BCA – typical functional statement

Part E2 – Smoke hazard management

EF2.1A building is to be provided with safeguards so that—

a) occupants are warned of a fire in the building so that they may safely evacuate, and

b) occupants have time to safely evacuate before the environment in any evacuation route becomes untenable from the effects of fire.

BCA – typical performance requirement

Smoke control systems

The BCA has a number of options for smoke control including but not limited to:

• Physical containment

• Air‐pressurisation systems

• Zone smoke control

• Smoke exhaust, and

• Smoke and heat vents

The remainder of this presentation is focussed on common (mis)interpretations related to compliance with the DTS provisions of the BCA for mechanical design .

Enclosure of shafts

• Clause 2.7 of specification C1.1 of the BCA requires riser shafts (that need an FRL) to be enclosed at the top and bottom by construction having an FRL not less than that required for the walls of a non‐loadbearing shaft in the same building.

• There is a conflict between the requirements of the BCA and Australian Standard AS/NZS 1668.1:1998, which allows for either the top or bottom fire compartment to form part of the same mechanical shaft.

Enclosure of shafts – continued

Enclosure of shafts - continued

• It is noted that clause C3.15(b) of the BCA allows for treatment of penetrations through elements that are required to achieve an FRL to be in accordance with AS/NZS 1668.1:1998.

• It is interpretive which clause of the BCA takes precedence.

• Where a conflict exists, it is possible to address the departure to the DTS provisions of the BCA in an alternative solution report.

Smoke damper vs fire damper requirements

Clause E2.2(b) of the BCA requires that each sole‐occupancy unit in a class 2 or 3 building be treated as a separate fire compartment.

A question that often arises is whether mechanical penetrations through fire‐rated bounding walls of residential apartments require fire or smoke dampers.

Note. A smoke damper is by definition also a fire damper in addition to the extra parts to also be considered to resist smoke.

The requirements of clause E2.2(b) and AS/NZS 1668.1:1998 are:

Clause E2.2(b)

An air‐handling system which does not form part of a smoke hazard management system in accordance with table E2.2a or table E2.2b and which recycles air from one fire compartment to another fire compartment or operates in a manner that may unduly contribute to the spread of smoke from one fire compartment to another fire compartment must—

Smoke damper vs fire damper requirements - continued


Clause E2.2(b)• be designed and installed to operate as a smoke

control system in accordance with AS/NZS 1668.1; orSmoke control = stairway or zone pressurisation, smoke exhaust, system shut‐down. It is interpretive as to whether passive system could also be considered as smoke control.It is noted that service penetrations are listed as a ‘smoke control priority’ in appendix A3 of AS/NZS 1668.1. However as the heading suggests, it is for smoke control, not fire control. As such, having fire dampers only is not considered to meet the intent of this clause for penetrations in bounding walls for smoke control.

Clause E2.2(b)• incorporate smoke dampers where the air‐handling ducts

penetrate any elements separating the fire compartments served; and

• be arranged such that the air‐handling system is shut down and the smoke dampers are activated to close automatically by smoke detectors complying with clause 4.10 of AS/NZS 1668.1; and The part about the closing of smoke dampers by smoke detectors is clear and would be required.

The shut down requirement is interpretive given that AS/NZS 1668.1 allows for minor systems to continue to run. Same in parts of tables E2.2a and E2.2b. As such it can be considered acceptable (DTS) to have the minor system continue to run and be compliant with this clause.


Clause E2.2(c)

Section 11 of AS/NZS 1668.1 relates to kitchen hoods and is not applicable for penetrations in fire‐rated bounding construction. Not relevant to this presentation.


Section 5 of AS/NZS 1668.1

5.3.1 Minor exhaust systems protected with fire dampers, in accordance with Clause 3.3, may operate in the fire mode.

A minor exhaust is a system having openings from a fire compartment not exceeding 0.1 m2 into a separate shaft or duct within a shaft.

This clause allows the toilet exhaust system to continue to run, but its not mandatory. Fire damper is required by clause 3.3 as the toilet exhaust is not smoke‐spill or minor system protected with sub‐ducts.


• The term unduly needs to be taken into context.

• A 0.1m2 opening is fairly large (ie 0.33m x 0.33m) and would easily represent the largest opening in an SOU. Typical fire doors (no smoke seals) have an equivalent area of approximately 0.02m2, which is five time less than the mechanical vent.

• The use of an intumescent/heat activated fire damper is unlikely to activate and stop the spread of smoke during the early stages of a fire or during a sprinkler controlled fire. This is noted by BS 9999, CISBE guide and NZ building code.

• Historically, failure of smoke/fire dampers in sleeping tenancies (ieMGM hotel fire) has resulted in catastrophic consequences therefore should be taken very seriously.


Summary

BCA requires:

• smoke dampers in bounding walls of residential units where penetrated by air‐handling systems unless mechanical engineer is confident that arrangement will not unduly spread smoke.

• When required, smoke dampers to close automatically when activated by smoke detectors complying with clause 4.10 of AS/NZS 1668.1

• Not necessary for the minor toilet exhaust system to shut down provided this complies with AS/NZS 1668.1


Air pressurisation systems

• Table E2.2a specifies that air pressurisation systems be installed in fire‐isolated stairways in buildings exceeding 25m in effective height and fire passageways greater than 60m in length. The installation is to be in accordance with AS/NZS 1668.1:1998.

• There are different requirements depending whether the pressurisation system is in a stair or a passageway.

• For a stair, AS/NZS 1668.1:1998 requires that the minimum air‐velocity be maintained into the fire affected compartment with the main discharge doors and all doors to the fire affected compartment fully open.

• This requirement is sometimes missed in design, or otherwise creates an onerous requirement.

Air pressurisation systems – continued

• For example, a building that has a stair that serves floor by floor compartments only needs to account for 2 doors being open. Assuming 2m2 per door at 1m/s equates to a minimum airflow of 4m3/s.

• Every storey of a fire compartment that opens to the same stair adds to this requirement – eg a four level carpark would require 10m3/s.

• Whilst variable speed fans can assist, the long term ability to maintain door opening forces is difficult.

• An option is to address this requirement in an alternative solution to rationalise the current requirements.

Impulse fans in carparks

• Clause F4.11 of the BCA requires that carparks – that are not open deck – have a ventilation system in accordance with AS 1668.2, or a system of natural ventilation complying with AS 1668.4‐2012.

• Since BCA 2013, AS 1668.2‐2012 has been adopted .

• Under AS 1668.2‐2012, exhaust and supply air is required to achieve certain flow rates, dependant on the geometry and available natural ventilation.

• Impulse fans are only permitted by AS 1668.2‐2012 as supplementary to the exhaust and supply air flow rates.

Impulse fans in carparks – continued

• Where impulse fans are used as the only means of ventilating a carpark, an alternative solution addressing the departure to the DTS provisions of clause F4.11 and performance requirements FP4.3 and FP4.4 of the BCA and AS 1668.2 is required to be completed by the mechanical engineer for the project.

• Because AS 1668.2‐2012 has related provisions in table E2.2a, an alternative solution addressing the performance requirement EP2.2 (and EP1.4 in sprinklered carparks) and the provisions of AS/NZS 1668.1‐1998 is also required.


• Whilst the primary role of a carpark ventilation system is to maintain air quality and remove CO emissions, it has a secondary requirement to incorporate provisions to enable manual control by firefighters for smoke clearance.

• This is because carparks, particular those below ground, are difficult to clear smoke from after a fire event.

• For this reason, BCA table E2.2a requires class 7a buildings that are provided with a mechanical ventilation system in accordance with AS 1668.2 must also comply with clause 5.5 of AS 1668.1 except that:

– fans with metal blades suitable for operation at normal temperature may be used, and

– the electrical power and control cabling need not be fire rated.


Clause 5.5 of AS/NZS 1668.1.• Part 5.5.3 of AS 1668.1 requires manual control of fans for fire personnel

and requires each fan shall be provided with an ON‐AUTO‐OFF control device installed in the FFCP in compliance with clause 4.13.2

• Part 5.5.4 of AS 1668.1 requires smoke detectors in accordance with clause 4.10.1 to be installed in the supply air system in accordance with clause 4.10.5(b).

• Clause 4.10.5 (b) of AS 1668.1 requires detectors for supply or outdoor air‐handling systems to indicate on the FIP. These detectors shall not raise a fire alarm and shall only provide control of the supply air fan operation, with the supply fan stopping upon detection of smoke.

• Smoke detectors are required within the carpark but only in supply air system (ie not throughout the carpark) and they only need to indicate on the FIP but not raise a fire alarm.


• The fire safety issues that arise are from a system that only incorporates impulse fans are:– Whether the normal running of the impulse fans to clear CO

emissions will cause a delay in sprinkler activation owing to air movement around the sprinkler head.

– Whether the fans will cause smoke to be present throughout more areas of the carpark in the early stages of fire.

– Whether impulse fans should run or stop in fire mode.

– Where smoke detectors need to be located to comply the supply air stream requirements.

– Does each impulse fan need a ON‐AUTO‐OFF switch at the FIP?


• Use of 2012 version of AS 1668.2 does not require an alternative solution if the system fully complies with the standard. In this instance, the additional firefighting facilities and smoke detection requirements of table E2.2a of the BCA and AS/NZS 1668.1 can be met.

• Where the design only includes impulse fans, an alternative solution which addresses the performance requirements of part F and part E of the BCA. These may be by different engineers – ie mechanical engineer for part F and fire engineer for part E provisions.


• Smoke clearance requirements will need to form part of an alternative solution report and will be assessed on a case by case basis by ACTF&R, but in general will require:– Non‐latching smoke detectors are provided within the

carpark to control the system.

– That impulse fans stop in fire mode and exhaust fans begin or continue to run at full capacity.

– Appropriate controls are provided for brigade operation.


Fire & Rescue NSW have also released a guideline on the use of impulse fans in car parks which can be found at http://www.fire.nsw.gov.au/gallery/files/pdf/guidelines/impulse_fans_in_carparks.pdf

This guideline has a similar intent to that of ACTF&R.

Open deck carparks

The open‐deck requirements of part A1.1 of the BCA are that:

• all parts of the parking storeys are cross‐ventilated by permanent unobstructed openings in not fewer than 2 opposite or approximately opposite sides, and—

‐ each side that provides ventilation is not less than 1/6 of the area of any other side; and

‐ the openings are not less than ½ of the wall area of the side concerned.

Open deck carparks – continued

Extract from Onesteel ‘Economical Carparks – A Guide to Fire Safety’ – April 2005


Neither the BCA nor the Guide to the BCA provides any clarification on the requirement to provide ventilation in opposite walls. AS1668.2 states that ‘positioning of external openings on opposite or adjacent sides of the building should maximise the cross‐ventilation benefit of wind effects’.


DTS options for compliance

• Meet the dimensional requirements of the BCA for an open‐deck carpark. If this occurs, no further mechanical review is necessary.

• If a carpark does not strictly meet the requirements of an open‐deck carpark, then either the mechanical ventilation requirement of AS 1668.2 or the natural ventilation requirements of AS 1668.4 need to be met.


Alternative solutions for compliance

• If the carpark does not meet the provisions of clause F4.11 of the BCA, then an alternative solution that address BCA performance requirements FP4.3 and FP4.4 is required.

• Because of the related smoke hazard management provisions, the alternative solution must also address performance requirement EP2.2 – and depending on the State or Territory requirements – may also need to be submitted to the local fire service for support – ie would need to be referred to ACT Fire & Rescue in ACT.


Alternative solutions for compliance - continued

• It is not permitted to do an alternative solution to a definition in the BCA.

• For example, if a mechanical engineer does an assessment that demonstrates a carpark is at least ‘equivalent’ to an open‐deck carpark, that does not mean there is an automatic concession to other open‐deck requirements.

• Each DTS provision that has a requirement related to open‐deck carparks needs to be assessed independently – ie concessions for fire resistance levels and / or sprinklers would need to be assessed by a fire engineer and ventilation by a mechanical engineer. Two alternative solutions are required.

Fire safety engineering

Engineers Australia definition is that:

fire safety engineering is multidisciplinary in nature, having substantial relationships with building services, mechanical, electrical, electronics, chemical, structural and civil engineering and embraces an understanding of human behaviour.

Typical fire engineering IFEG process

Prepare FEB

Carry out analysis

Collate and evaluate results

Draw conclusions

Prepare report

Fire engineering brief

• secure agreement from all parties

• establish trial concept design(s) / fire safetymeasures, and

• specify the requisite• fire scenarios

• design fires

• acceptance criteria

IFEG Sub-systems

Sub‐system A – Fire initiation and development and control

Sub‐system B – Smoke development and spread and control

Sub‐system C – Fire spread and impact and control

Sub‐system D – Fire detection, warning and suppression

Sub‐system E – Occupant evacuation and control

Sub‐system F – Fire services intervention

Approaches and methods of analysis

The IFEG lists the following approaches:

• Comparative

• Absolute

• Qualitative

• Quantitative

• Deterministic

• Probabilistic

It is typical that assessments use more than one approach – ie comparative absolute.

Zone and field (CFD) modelling

• Examples of deterministic fire models– Zone

– Field: Computational Fluid Dynamics (CFD)

• The use of either zone or CFD models will dependon the required outputs.

• For example, if smoke layer height only isrequired for simple scenarios, then zone modelsmay be appropriate, or if visibility, temperature,toxicity etc. are also required, then CFD modelsshould be used.

Zone models

• A zone model uses a simplified geometry andrepresents the compartment as two distinctlayers:– a hot upper layer, and

– a cooler lower layer.

• The layering results from the buoyancy of the hot smoke.

• Each layer is assumed uniform in structure or composition and the interface between the two is taken as horizontal.

Zone models

• The calculations for smoke production are quite complex,but basically work on the assumption that the rate ofsmoke production is approximately equal to the totalvolume of air entrained. This is because the other productsof combustion are relatively small when compared to thisamount.

• The user must be familiar with limitations on compartment size, number of rooms, impact of supply air and smoke layering.

• Zone models are largely based on empirical data and are only suitable for simple analyses.

• The benefit is that they are quick to use and may assist where a large number of scenarios require assessment.

CFD models

• CFD modelling is the process of discretising and then solving the fundamental equations of fluid dynamics

• CFD models are grid dependant and allow for modelling of complex geometries.

• They can provide a representation of smoke density/temperature and a range of different outputs.

• Different models have varying degree of empirical data versus numerical solution – eg. Large Eddy Simulation or Direct Numerical Simulation models.

• They are suitable for detailed analysis, but because of the time taken are generally only used for modelling of a few fire scenarios.

CFD model

CFD smoke spread

CFD visibility slice file

Evacuation models

Required Safe Egress Time (RSET)

The IFEG states that the required safe egress time (RSET) is the time from when a fire initiates to the time when occupants reach a place of safety. The calculation is generally the addition of four periods:• Cue period (Pc) – taken from the time of fire initiation to the time a cue indicates

the occurrence of a fire – ie intrinsic or alarm.• Response period (Pr) – taken from the time a cue indicates the occurrence of a

fire to the time occupants recognise the cue as an indication of a fire.• Delay period (Pd) – taken from the time occupants recognise the cue as an

indication of fire to the time occupants commence evacuation.• Movement period (Pm) – taken from the time occupants commence evacuation to

the time when occupants reach a place of safety. This period is calculated on the basis of human walking speeds and queuing at exits affected by crowding.

Movement time parameters

Occupant movement times are generally based on three deciding criteria:

• Travel distance• Path of travel and exit width, and• Crowding

Evacuation speed as a function of density

constant.

.persons/min density =D

(m/s). travelof line thealong speed =S

:where

0.266kD-k=S

2

k

Equation 1 Evacuation speed as a function of density

Figure 1 Evacuation speed as a function of density

Evacuation Speed as a Function of Density

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.5 1 1.5 2 2.5 3 3.5 4

Density (persons/m2)

Mo

vem

ent S

pee

d (m

/s)

Corridor, Aisle, Ramp, Doorway

Stair A (Riser = 190mm/Tread =255mm)

Stair B (Riser = 180mm/Tread =280mm)

Stair C (Riser = 170mm/Tread =305mm)

Stair D (Riser = 170mm/Tread =330mm)

SFPE effective width

Exit Route Element Boundary Layer (mm)

Stairways – wall or side tread 150

Railings, handrails (and balustrades)

Note. Where handrails are present, use the value if it results in a less effective exit width

90

Theatre Chairs, stadium benches 0

Corridor, ramp walls 200

Obstacles 100

Wide concourses, passageways 460

Door, archways 150

Egress modelling - Pathfinder simulator

Inputs for comparative assessment of different models

• Single storey building used as a performance hall.

• All occupants in the building are assumed to commence evacuation at 0 seconds.

• Floor area of approximately 610m2.• Peak population of 600 occupants based on

maximum number of seats able to be accomodated.

• Total exit width of 15m over 9 doors (effective width 12.3m).

Defire spreadsheet using SFPE methodologies

Exit element Effective width (m) Effective flow rate (persons/min)

Exit 01 - double-leaf doorDoorway (unobstructed)

1.20 94


1.20 94


1.20 94


1.20 94


1.20 94


1.70 133


1.70 133


1.70 133


1.20 94

Population 600

Total effective flow rate (persons/min) 959 From SFPE Handbook

Queuing time (s) 38 = 0.7 mins

Travel distance (m) 40

Travel speed (m/s) 1 From SFPE Handbook

Travel time (s) 40 = 0.7 mins

Total evacuation time (s) 40 = 0.7 mins Note: Travel time exceeds queuing time

Effective flow rates of elements

Queuing calculation

Travel time calculation

Summary

Pathfinder simulation – no walls

Simulex simulation

Pathfinder simulation – with seating

Egress modelling - Pathfinder simulator

Summary of alternative solution process

• Summary of fire engineering alternative solution process:– Identify departures to DTS provisions of the BCA

– Identify performance requirements

– Chose a method (qualitative/quantitative, absolute/comparative)

– Undertake a fire engineering brief meeting with stakeholders

– Assess the alternative design

– Show compliance with performance requirements

– Issue report to regulators for review and to stakeholders for comment

– Prepare inspection checklist

– Undertake inspection and prepare report for regulatory authorities

Conclusion

Thanks for your time

Stephen Wise

[email protected]

02 6260 8488

www.defire.com.au

act on fire! bca compliance and fire safety engineering€¦ · · 2016-09-17bca compliance and...

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