11 Talavera Road, Macquarie Park Design Development Note 1 ... · This Fire Safety Engineering...

11 Talavera Road, Macquarie Park

Design Development Note 1.3: Preliminary Fire Safety Engineering Strategy

Project: S16284 Date: 07 March 2017 Prepared by: Colin Thomson Reviewed by: Trent De Maria | State Manager NSW | 1

1 Introduction

1.1 Application

A preliminary fire engineering investigation has been undertaken to provide confidence to project stakeholders that the documentation at the current design stage that is being readied for issuance of the planning permit is capable of achieving compliance with the Building Code of Australia (BCA).

The subject design has been observed to exhibit a number of non-conformances with the prescriptive provisions of the BCA. These non-conformances have been to date, and will continue to be identified by the Authority Having Jurisdiction.

Subsequently, it will be necessary for the method of compliance with the building regulations to incorporate a Performance Based approach as supported by the BCA. Olsson Fire & Risk have reviewed the architectural design drawings and proposes the following fire safety strategy for consideration.

We can confirm that based on the strategy documented herein, that an assessment can be undertaken by a C10 Accredited Fire Engineer in consultation with project stakeholders (including the Principal Certifying Authority), to demonstrate that the building will comply with the Performance Requirements of the BCA. This may be via a combination of the following:

Becoming Deemed-to-Satisfy by way of design development.

Comparison to the BCA Deemed-to-Satisfy Provisions to demonstrate equivalence.

Compliance with the BCA Performance Requirements.

It is considered that the preparation of the Performance Solutions and corresponding fire safety measures that are likely to be documented therein will not result in significant changes to the building design presented in the schematic drawings reviewed for the feasibility stage and planning permit.

1.2 Scope & Objective

This Fire Safety Strategy outlines the construction and management requirements considered necessary to achieve an acceptable level of life safety with the building and satisfy the Performance Requirements of the BCA. As a preliminary document the requirements are high level in nature only, meant to assist with detailed design preparation.

The complete fire engineering analysis will form the Fire Engineering Report, and is to be developed as the design progresses. As such, no analysis is documented herein.

1.3 Design Objectives

The aim of the design is to provide an adequate level of fire safety for the building occupants, firefighters and maintenance and other emergency services personnel. The BCA's fire safety objectives are:

Safety of occupants (reduce risk to an acceptable level).

Facilitation of effective emergency services intervention.

Protection of adjoining property and third parties.

1.4 Project Description

The project consists of a new commercial building (’11 Talavera Road’), as well as minor changes to adjacent existing buildings (‘Building A’ and ‘Building B’) in Macquarie Park, New South Wales. The site is bounded by Talavera Road to the north-east, and Lane Cove Road to the south-east. This Fire Safety Engineering Strategy shall focus on the new development, nominated as ‘the building’ for the remainder of this document. This is depicted below.

Figure 1: Site and Surrounding Area

As the site slopes from one side to the other, access to the building is available at grade at two levels (Lower and Upper Ground). It is understood that the main building use will be as a commercial office (Levels 1-10). There are a further 5 levels of basement car parking associated with the building. The typical floorplates are depicted in Figure 2 to Figure 6.

It is noted that an atrium is proposed to extend from Lower Ground to the roof at Level 10. The provision of an atrium will be a key fire safety consideration for this building.




Figure 2: Basement Levels 1-5 (Indicative)

Figure 3: Lower Ground Level

Figure 4: Upper Ground Level

Figure 5: Typical Level (1-9)




Figure 6: Level 10 / Roof Terrace

Figure 7: Roof

Figure 8: Elevation Drawing (North Elevation)




2 Key Design Objectives When developing a design, the stakeholders of the project should take into consideration multiple different aspects. These objectives in design range from preventing a fire from starting, to preventing collapse of a structure, to how do fire services interact with the building. This document does not attempt to detail all of these requirements, their inclusion here is to highlight their importance and signify that these elements will form part of the overall safety strategy for the building as design progresses.

2.1 Preventative Measures

Measures should be provided to reduce the likelihood of an incident. Measures to be considered by stakeholders should include the following:

Operational plans which minimise occupant risk.

Staff training.

Maintenance of the building and fire safety systems.

Control of combustibles.

Control of potential ignition sources.

2.2 Incident Mitigation

Measures should be provided to mitigate the impact of an incident. Measures to be considered include the following:

Active and passive protection systems including, but not limited to:

o Fire detection & alarm systems;

o Smoke hazard management, specifically within the atrium area;

o Structural protection, fire separation and compartmentation;

o Egress systems;

o Fire suppression systems such as sprinklers;

o Control of combustibles and spread of flame; and

o First attack and communication facilities.

Emergency management:

o Staff training;

o Emergency services training;

o Emergency drills and exercises; and

o Public education.

2.3 Asset Protection

The level of asset protection is a matter for the asset owner and should include consideration of the following:

Life cycle costing with a balance between capital and recurrent expenditure.

Provisions for protection of the structure.

Protection of adjoining critical structures or infrastructure.

Ease of operation, inspection and maintenance.

Provision for protection of fire safety measures from mechanical or accidental damage.

2.4 Structural Damage

As a minimum the level of fire protection to limit structural damage should meet life safety, asset protection and business interruption requirements. Factors to be considered include the following:

Potential for collapse or failure in critical areas.

Protection of emergency services.

Repair technique.

Progressive collapse.

Structural damage resulting in failure of safety systems.

Proposed fire-suppression systems.

Failure of fire-separating elements.

2.5 Emergency Services Intervention

The design for emergency services should include the following:

Level of emergency services intervention required.

Regulatory requirements.

Emergency services intervention policy.

Response time and capability.

Intervention access (terrain).

Water supply.

Emergency services interface with safety measures and normal operational systems.

2.6 Constructability

Fire safety solutions will be influenced by the constructability of the building.

Constructability will be constrained by factors such as the architectural design aspiration, building geometry, terrain, ground type, groundwater, construction method and costs.

2.7 Other Considerations

Other aspects to be considered may include the following:

Maintainability, reliability and redundancy of the design

Safety in design requirements

Need for fire safety measures to cater for emergencies other than fire or other operational requirements.

Environmental regulation, contaminated fire water management, points of discharge of smoke.




3 Fire Engineering Process

3.1 Scope

This Section provides a framework to guide both the project parties and external groups in their input to the project. The parties noted are restricted to those directly relevant to the facility’s fire safety.

Stakeholders should be involved in the fire safety engineering process. Stakeholder roles within the project should be clearly defined in the Fire Engineering Brief (FEB). Roles may be defined by legislation, contract documentation or other project requirements.

3.2 Stakeholders

1. Authority Having Jurisdiction (AHJ) - The AHJ has responsibilities in relation to administering the fire safety requirements including the following:

a. Approval of the trial concept design and relevant fire and life safety elements.

b. Defining the project objectives and performance requirements applicable to the trial concept design and relevant fire and life safety elements.

c. Providing advice during the FEB/FER process.

d. Carrying out the appropriate regulatory functions.

e. Accepting third-party review of the trial concept design.

f. Arbitration where there is a dispute between the stakeholders.

2. Principal and/or Proponent - The Principal is usually the owner, whilst the Proponent is taken to mean the entity that has contracted with the Principal to build the building.

3. Contractor - The contractor is the entity that will engage staff and resources to build the project. It may be part of the proponent organisation or separate to it.

4. Design entities - The Principal, the proponent or the contractor arranges for design work for the project to be done by one or more design entities who are responsible for translating the relevant fire safety engineering reports into detailed design and documentation for construction.

5. Fire Safety Engineer - The role of the fire safety engineer is to develop the fire safety design and demonstrate the adequate performance of that design to the satisfaction of the Principal and the Authority Having Jurisdiction.

6. Fire authority - The fire authority provides input to the fire engineering process in relation to its statutory role. This input may include—

a. Protection of persons, property and the environment from fire and hazardous materials emergencies;

b. Management of emergencies; and

c. Provision of an advisory service and undertaking of other activities, to promote fire safety and operational requirements.

3.3 Fire Safety Design Stages

The fire safety design advances in line with the general design process. Initial focus is on the input to the design such as stakeholder objectives and performance expectations. As the general design develops, the fire safety design advances through fire safety strategy at the concept level to more detailed specifications of the fire safety measures. The stages described may overlap and vary in practice but will tend to advance in line with the overall design. The final documentation should be specific to the fire systems that have been adopted and should demonstrate the adequacy of the systems.

3.3.1 Trial Concept Design (Fire Safety Strategy)

The purpose of the trial concept design process is to reach a broad consensus on an appropriate fire safety system and fire safety strategy that meets with the fire safety objectives for the building. This will require an understanding of the physical attributes and likely use of the building and identification of the potential hazards that may arise when the building is put into operation. The trial concept design will identify preliminary fire safety measures that will be assessed from the perspective of achieving acceptable performance in terms of the agreed fire safety objectives in the context of identified hazards and fire scenarios. To develop the trial concept design, a series of workshops with stakeholders may be required and the preliminary fire safety measures may be amended by consensus of the stakeholder group.

3.3.2 Schematic Design (Fire Engineering Brief)

During the schematic design stage, the fire safety strategy and fire safety measures for the building will be developed further and will be documented in a Fire Engineering Brief (FEB). The purpose of the FEB is to document the design parameters and acceptance criteria to gain agreement, in principle, of the stakeholders.

3.3.3 Design Development (Fire Engineering Report)

The aim of the design development stage is to assess and further develop the schematic fire engineering design and develop a fire safety strategy that meets the fire safety objectives by appropriately responding to the identified hazards arising from the use of the building. The process of fire engineering assessment involves testing of the adequacy of the proposed design through a number of scenario analyses, or through a rigorous risk analysis process, as determined at the FEB stage. The fire safety system is considered to be adequate when the outcome of the analysis demonstrates achievement of the acceptance criteria.

3.3.4 Installation and construction

The fire safety design will provide input for the installation and construction stages. If there are modifications made to the fire safety system which alter the fire engineering design as presented to the stakeholders, such changes are to be assessed by a fire safety engineer and reviewed by the stakeholders prior to implementation of the changes.

3.3.5 Commissioning and testing

Adequate commissioning and testing should be undertaken to ensure that the design requirements have been realised in the completed works. The fire safety engineer should witness commissioning and testing to ensure the system performance is in accordance with the FER.

3.3.6 Operation and maintenance

Operation and maintenance of the building's fire safety system need to be in accordance with the trial concept design (fire safety strategy), and incorporated into the building’s incident management and response plans. The fire safety engineer should direct or be involved in the development of the incident management and response plans as well as contribute to the operation and maintenance plan.




4 Building Characteristics

4.1 Introduction

The works involve the construction of a new commercial office building in Macquarie Park, NSW. The building will consist of 5 levels of basement car parking, a Lower and Upper Ground Level featuring a mix of retail and office uses, and Levels 1-10 being for office use.

4.2 BCA Characteristics

The key building characteristics as detailed in the Building Code of Australia and identified by the PCA are as follows:

BCA Classification Class 5, 6, 7a

Rise in Storeys (RIS): 12

Total Storeys Contained 17

Type of Construction: A

Effective Height: 41.45 m

4.3 List of Identified BCA Deemed-to-Satisfy provision DtS non-compliances

The following preliminary list of Building Code of Australia Deemed-to-Satisfy provision DtS non-compliances has been identified by the PCA.

Table 1: List of DtS non-compliances

NO. DtS Clause Description Performance Requirement

1 D1.4, D1.5 Travel distance

Travel distances are expected to be extended over DtS compliant distances for the following areas:

Basement

Travel distances of up to 60 m to an exit in lieu of 40 m.

Lower Ground (Loading Bay)

Travel distances up to 25 m to a point of choice in lieu of 20

m.


Upper Ground (Retail T6)

Travel distances up to 29 m to a point of choice in lieu of 20

m.

Levels 1-9


DP4, EP2.2

NO. DtS Clause Description Performance Requirement

Roof Terrace


2 D1.7, D2.4 Travel by Fire Isolated Exits

Fire isolated exits within the building share a common path, therefore not providing independent egress nor separation of rising and descending flights.

DP4, EP2.2

3 C2.2, G3.3, G3.4, Spec G3.8

Atrium Provisions

It is anticipated that the atrium spanning from Lower Ground to Level 10 will not meet all of the prescriptive atrium provisions, in particular:

Atrium Smoke Exhaust Rates and Zone Smoke Control System

Requirements will be rationalised.

Bounding construction will not be provided on all levels, or not

provided within the prescriptive distances.

Further, due to the open connection between floors the general floor area and volume limitations of Clause C2.2 may be exceeded.

CP1, CP2, EP2.2




5 Fire safety strategy The following table lists the DtS requirement for the subject building relevant to fire safety. At this stage, the list is not intended to be exhaustive, but does provide indication of the fire safety requirements that can be expected for the building design.

Table 2: Fire Safety Schedule

Fire Safety Measure Description

General Unless identified in Table 1 of this document, the building shall be expected to meet all Deemed-to-Satisfy requirements of the BCA that apply to the building with regards to fire safety. This includes, but is not limited to, the following Sections:

Section C – Fire Resistance

Section D – Access and Egress

Section E – Services and Equipment

In addition to meeting the above Sections of the BCA in a general sense, the following specific Clauses and Australian Standards are expected to apply and form part of a draft Fire Safety Schedule:

Emergency lifts (BCA Clause E3.4, AS 1735.2-2001)

Emergency lighting and exit signs (BCA Clause E4.2, E4.4, E4.5, E4.6, E4.8, AS 2293.1-2005)

Fire alarm monitoring (AS 1670.3-2003)

Fire detection and alarm system (BCA Clause E2.2a and AS 1670.1-2015)

Fire doors (BCA Clauses C3.2-C3.8, AS 1905.1-2015)

Fire dampers (BCA Clause E2.2, C3.15 AS 1668.1-2015, AS 1682.1)

Fire hose reels (BCA Clause E1.4, AS 2441-2005)

Fire hydrant system (BCA Clause E1.3, AS 2419.1-2005)

Fire seals (BCA Clause C3.15, AS 1530.4-2014)

Fire sprinkler system (BCA Clause E1.5, AS 2118.1-1999 and potentially AS2118.6-2012)

Portable fire extinguishers (BCA Clause E1.6, AS 2444-2001)

Smoke hazard management systems, including mechanical air handling, stair pressurisation, zone smoke control, and smoke exhaust (BCA Part E2, AS 1668.1-2015 and AS 1670.1-2015)

Sound Systems and Intercom Systems for Emergency Purposes (BCA Clause E4.9, AS 1670.4-2015)

Wall wetting sprinklers (BCA Clause C3.4, AS 2118.2-2010)

Sprinklers Sprinklers are to be provided throughout the building in accordance with BCA Clause E1.5 and AS2118.1-1999.

Any glazing that requires protection due to proximity of exit discharge shall have internal wall-wetting sprinklers to AS 2118.2 applied to the glazing to the extent required. The glazing shall be fixed closed and be of toughened, Grade A safety glass of at least 6mm thick.

In addition, the following requirements are expected based on the Performance Solutions:

Fast response sprinklers shall be provided throughout the basement carpark levels. The sprinklers shall have a maximum RTI of 50 m0.5s0.5 and activation temperatures no greater than 68 oC.

Atrium The provision of the atrium construction shall be in accordance with BCA Clause G3 and Specification G3.8. The extent of the Performance Solution to be provided is still to be determined, however it is expected that the following Clauses shall apply:




Fire Safety Measure Description

G3.7 - Means of Egress – All areas considered part of the atrium must have access to at least 2 exits.

Specification G3.8

2.1 Sprinklers required for building – Sprinklers are already required as the building is greater than 25m, as well as being required for atrium design.

2.3 Atrium Floor Protection – The floor area requires sprinkler protection and coverage.

2.4 Sprinklers to Glazed Walls – Where specified, glazed walls require these protection requirements.

2.5 Stop Valves – Stop valves to be provided as required.

3.1 General Air Handling to comply with AS1668.1 – The general air handling system requirements from AS1668.1 shall apply.

3.2 Atrium Mechanical Air Handling System – The air handling system requirements shall apply.

3.3 Activation of Smoke Control System – The activation of the smoke control system is to be activated as expected by the BCA.

3.6 Exhaust Fans Requirements – The operability of the fans in fire conditions and redundancy are to be provided.

3.8 Make-Up Air Supply – Make-up air is to be provided at or near the lowest storey level of the atrium and relief air from the non-fire storeys, and shall be distributed uniformly. The make-up air supply

is recommended to be mechanically supplied in order to provide a reliable source.

4.1 Compliance with AS1670.1 – Automatic detection systems are expected to comply with AS1670.1.

4.2 Smoke detection within Atrium – The requirements of smoke detection are expected to be complied with.

4.3 Smoke detection in spaces separated by bounding wall – The requirements of smoke detection are expected to be complied with.

4.4 Alarm Systems – The additional provisions for the alarm systems are expected to be provided.

5 Sound Systems and Intercom Systems for Emergency Purposes – A SSISEP is already required as the building is over 25 m and shall be provided.

7 System for excluding smoke from fire isolated exits – Stair pressurisation is required as the building is also over 25 m and shall be provided.

The provisions of bounding construction and smoke exhaust are expected to be determined in later analysis.




The following table lists the method of assessment for the Performance Solutions, expected fire safety requirements and recommendations.

Table 3: Performance Solutions

Solution DtS Clause Description Performance Requirement

Method of assessment/Fire safety requirement

1 D1.4, D1.5 Travel distance

Travel distances are expected to be extended over DtS compliant distances for the following areas:

Basement


Lower Ground (Loading Bay)

Travel distances up to 25 m to a point of choice in lieu of 20 m.


Upper Ground (Retail T6)

Travel distances up to 29 m to a point of choice in lieu of 20 m.

Levels 1-9


Roof Terrace


DP4, EP2.2 The Basement carpark and Lower Ground (Loading Bay) extended travel distances may be supported via the inclusion of fast-response sprinkler heads in lieu of standard response sprinkler heads. The Performance Solution shall asses the difference in activation times quantitatively in proposing a comparative assessment. The analysis shall show that the earlier activation of the sprinkler system will sufficiently offset the increased travel times experienced.

The Upper Ground retail and Levels 1-9 commercial extended travel distances may be supported via the inclusion of either the smoke exhaust system for the atrium (where relevant), or reduced spacing for the smoke detection system. The Performance Solution shall asses the difference in activation times quantitatively in proposing a comparative assessment. The analysis shall show that the earlier activation of a reduced spacing detection system will sufficiently offset the increased travel times experienced. Further, for any tenancy open to the atrium, Computational Fluid Dynamic modelling shall determine the acceptability of the design and increased travel distances.

When required by the detailed analysis, additional doors, pathways or exits may be

required to reduce travel distances to supportable levels.

2 D1.7, D2.4 Travel by Fire Isolated Exits

Fire isolated exits within the building share a common path, therefore not

providing independent egress nor separation of rising and descending flights.

DP4, EP2.2 The Performance Solution shall be tailored to the determined Deemed-to-Satisfy non-compliances and assessed accordingly. The performance solution is expected to be assessed in an absolute and qualitative manner, describing the provided additional design requirements and their utility in safeguarding occupants during their egress.

Potential design requirements may include additional signage to increase wayfinding of

occupants, to ensure occupants do not travel past the point of discharge, and increased

degrees of separation between the stairs.

When required by the detailed analysis, compliant, independent discharge paths may be

specified, depending on scenario.

3 C2.2, G3.3, G3.4, Spec G3.8 Atrium Provisions

It is anticipated that the atrium spanning from Lower Ground to Level 10 will not meet all of the prescriptive atrium provisions, in particular:

Atrium Smoke Exhaust Rates and Zone Smoke Control System Requirements

Bounding construction is potentially omitted on levels, or not provided within the

prescriptive distances.

Further, the open nature of the Atrium will likely exceed the general floor area and volume limitations of the BCA.

CP1, CP2, EP2.2

The Performance Solution is to be assessed in an absolute and quantitative manner, utilising Computational Fluid Dynamics modelling to determine the acceptability of the Atrium Design. Any design constraints and fire safety requirements will also be determined through the modelling.

The acceptability will be based on demonstrating occupants are able egress safely before the onset of untenable conditions.

Preliminary design guidance has been provided in Section 6 of this document.




6 Atrium Design The atrium, which connects Lower Ground to Level 10, presents opportunity for smoke migration throughout the building. Subsequently, the mechanical design for the building needs to account for the mitigation of smoke spread to the degree necessary to enable safe evacuation of occupants and fire brigade intervention.

A BCA DtS compliant design is likely to be considered architecturally restrictive. This would include smoke exhaust rates exceeding 300 m3/s (and corresponding make up air quantities), bounding wall construction on each level and required setbacks would significantly reduce the effectiveness of the atrium in providing a light filled, open and communicative space.

The goal from a fire safety perspective is therefore to ensure that the life safety of occupants is maintained, while allowing many of the prescriptive provisions to be modified.

To that end, the following section discuss and presents opportunities for the atrium design.

It is highlighted that these comments, and any values provided herein, are preliminary and need be modified through detailed design.

6.1 Design Considerations

Atriums present a unique fire safety design problem. Much of the BCA relies upon compartmentation through the use of fire resisting construction such as fire walls to slow the spread of fire and smoke, such that occupants can safely egress. Atriums however eschew this approach, opening up multiple levels of compartmentation, especially to the effects of smoke. The Deemed-to-Satisfy provisions have attempted to compensate for this by prescriptively requiring smoke exhaust, level by level separation at the atrium, increased smoke detection requirements and other specifications.

But like much of the BCA, the one-size-fits-all approach rarely achieves the flexibility necessary for architectural design, and can often over-design elements with regards to fire safety.

To that effect, this Fire Safety Engineering Strategy has broken down each element of the BCA Atrium requirements to identify where flexibility may exist for the design, as well as giving a broad range of where that flexibility can be applied. This has been done with an eye to maintaining fire safety for the entire building as the primary goal. If at any time a reduction or removal of an element would result in occupant safety being compromised, the element shall be identified as being prescriptively required.

6.2 Exhaust Rates and Bounding Construction – Performance Solutions

The two elements most often that can exhibit potential performance solutions are the use of bounding construction for each level, and the overall exhaust rate required for the atrium design. For a DtS compliant design for this building, each level above the bottom three storeys would require full-height glazed or solid wall bounding construction, and the smoke exhaust rate would exceed 300 m3/s.

A Performance Solution may allow for the removal of much of the bounding wall construction, allowing for more open plan architectural design, as well as the rationalisation of the smoke exhaust rates. The reasoning that both these elements are possible are based on a number of factors, but primarily because the BCA is required to cover a multitude of design factors for atriums, which can come in all shapes and sizes. In order to cover such a large spectrum of design, the fire safety elements of the BCA are necessarily conservative. However, when applied to a singular design, aspects of the design may be modifiable with no reduction to the life safety of occupants. This is depicted in Figure 9.

Figure 9: Deemed to Satisfy and Performance Solution Design of Atrium

In order to support any alteration to the prescriptive requirements of the BCA, the Performance Solution must demonstrate that occupant life safety has not been adversely affected and that occupants can egress safely. To do this, detailed Computational Fluid Dynamic modelling would be undertaken, demonstrating not only occupant tenability but also the containment (or lack thereof) of the effects of a fire and any potential impacts on the building.

From a design perspective, the primary constraint identified at this stage is with regards to the top levels of the atrium. In order to form a smoke reservoir and allow for the smoke exhaust to effectively capture and extract the effects of a fire, it is anticipated that the top level of the atrium will require a fixed closed design. Depending on the detailed design of the building, including level heights, level compartmentation, make-up air pathways and exhaust rates, this compartmentation may be required to extend further downwards.

This can be seen from a very high level in the expected smoke layer height that occurs when varying smoke exhaust rates. A high level calculation has been performed on the atrium design, which gives early indication of exhaust requirements based on what height of smoke layer a specific exhaust rate can maintain. The height of the smoke layer would correspond to the levels that could be open to the atrium. The values expected for the Performance Solution would be comparatively lower than the expected Deemed-to-Satisfy exhaust rate from Specification G3.8, and depicted in Figure 10. It should be noted that these values are highly conservative and with detailed CFD analysis it would be expected that the exhaust rates required could be further reduced, depending on the bounding requirements and floor layouts.




Figure 10: Calculated Exhaust Rate Required versus BCA Specified Exhaust Rate

6.3 Design Considerations

Design objectives are considered to be as follows:

1. Delay smoke layer interface from descending to critical position.

2. Limit properties of smoke layer proportional to the degree of smoke exhaust provided

a. temperature

b. gas concentrations

c. light obscuration/visibility

To achieve these objectives, three design options are presented.

6.3.1 Enclosed Atrium

In this design, the atrium features glazed (or solid) walls encasing the atrium. From a fire engineering perspective, this is the closest to a ‘compliant’ design. The BCA allows an atrium to be open to circulation for the bottom 3 storeys in a compliant design (with numerous other requirements).

The glazing/walls would either need to be fire rated or have wall-wetting sprinklers if glazed. An exhaust system at the top of the atrium would also be required.

The BCA would specify substantial rates given the height of the atrium (300 m3/s+) but a Performance Solution likely could reduce that value significantly to below 100 m3/s. Of the three options, this would be the least restrictive in terms of performance of the atrium exhaust and on future uses of the space, as each level is compartmentalised.

6.3.2 Open Atrium

In this design, the atrium is open on all levels.

There will likely still need an enclosure at the topmost level, or creation of a reservoir to limit the migration of smoke into the floor plate.

This may extend to the top two levels depending on the final design and size of the atrium, but the majority of levels will be open to the void space.

A greater quantity of smoke exhaust system would be required compared to the enclosed atrium design of Section 6.3.1, as the exhaust will be working not only to maintain smoke from leaving the reservoir at the top, but to also ensure smoke that gets into the atrium moves into the smoke reservoir, rather than moving between balconies and into other floors.

Correspondingly, a substantial amount of make-up (forced or natural) air will also be required for this design. Preliminary analysis puts the exhaust anywhere in the range of 100 – 300 m3/s as being required. At this stage, the numerous variables that impact the potential exhaust rates (make up air locations, exhaust locations, ceiling heights, balcony heights, etc.) mean such a range of potential exhaust is necessarily conservative.

6.3.3 Variable design, with some open levels and some enclosed

A design allowing some levels to be open while enclosing others will result in a hybrid design to that offered in Section 6.3.1 and 6.3.2 . Other than the potential restriction of the top area being enclosed and being used as a smoke reservoir, the remainder of the levels may feature some degree of compartmentation/separation from the atrium. This would in effect vary the exhaust and fire safety requirements significantly based on the preferred design.

It should be noted that the design and fire safety requirements would be valid based on the compartmentation planned at time of occupancy for the building.

For a more robust design which may allow future tenancy changes to compartmentation (i.e. a tenant which previously was compartmentalised from the atrium wishes to have balconies instead of walls), a more conservative approach to the design levels would incorporate the Section 6.3.2 approach of having all available levels open to the atrium, as that would be the ‘worst case’ design from a smoke exhaust perspective. This would provide the utmost level of flexibility in the design of the building, not just in the initial handover but for the future of the building as well, but come at the drawback that it may provide an oversized exhaust system for the actual end use of the atrium. Stakeholder direction will determine the direction of design in this regard.

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