Performance Based Fire Life Safety for Road Tunnels Craig Hiscock

22 November 2013

Reference Design Solution

Contractual prescriptive

design requirements

Stakeholder influences

Uniformity in tender

designs

Factors influencing recent design processes

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Examples of prescriptive design requirements

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•  Twin tubes •  Cross-passage spacing 120m •  Smoke exhaust or management for large fires •  Fire rated concrete to modified hydrocarbon fires •  Fire resistant architectural panelling

Need for a tunnel identified

Austroad’s - Guide to road tunnels Part 2

AS 4825 – Tunnel fire safety

Tunnel FLS concept or reference design

AGRT Intended design development process

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•  AGRT – 1 Section 10.3 states “The practice described in the forthcoming Australian Standard AS 4825 forms the basis of the requirements of the Austroads Guide to Tunnels”.

•  AS 4825 recommends using risk, but, provides no risk acceptance criteria.

•  AS 4825 provides process, but, allows process to be adapted to suit the circumstance.

•  Neither Austroads or AS 4825 specifically cater for existing tunnel upgrades.

•  AS 4825 read as a prescriptive document limits opportunities or innovation achieved by performance based design.

Limitations to current AGRT process

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•  Quantitative or Qualitative? •  Likelihood or frequency of events? •  Consequence criteria – Life Safety, Asset, Operational? •  Acceptance criteria – Fixed number, ALARP or Other? •  Construction influences? •  Operational influences? •  Cost influences?

Risk and risk acceptance

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• New tunnel concept or existing tunnel upgrade

• Get the fire and ventilation engineers in early

• Consultatively quantify clients requirements

• Consultatively quantify stakeholder needs

• Document preliminary design (nuts and bolts)

• Demonstrate preliminary designs risk is ALARP

• Agree preliminary design is appropriate

• Proceed to tender or construction

Idealised design development process

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ALARP Assessment and Cost Benefit Analysis

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Example – Double stacked carriageway

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AS 4825 provides guidance on exit spacing and states: •  Section 7.1 states - Spacing between exits within

tunnels are typically at a maximum of 120 m for road tunnels.

•  Item (d) of the Preface states – “Specifically, this standard does not restrict innovative approaches or new technologies provided that the required performance can be demonstrated”.

•  Section 5.9 Egress – provides performance requirements relative to occupant safety, therefore, provided appropriate egress outcomes are achieved, there may be opportunity to vary from the 120m spacing.

Example - Increasing cross-passage spacing

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Example - Fire Resistance and Suppression

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Example - Maximising smoke management opportunities

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Removal of smoke exhaust

Example - Smart lining solutions

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Example - Smart lining solutions

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AGRT Part 1: Section 3.3.6 provides guidance on the passage of DGV’s and states

•  Whether to allow the free passage of dangerous goods vehicles operating within the law should be determined through a risk management approach and involve all relevant stakeholders (e.g. the tunnel owner and operator, fire and rescue authorities and regulators).

•  One consideration is that diverting such vehicles off the major road system could transfer risk to locations that may not have facilities or ready access to deal with any emergency incident involving fire or spillage.

•  In any case, the operational requirements for the tunnel will need to be designed to accommodate the possibility of an incident involving an illegal entry of a vehicle transporting dangerous goods.

•  AS 4825 recommends that DGVs be assessed by a separate risk assessment process.

Example - Dangerous Goods Passage

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•  Designs can sometimes be focussed on capital costs, therefore operational and ongoing cost may not be considered.

•  Operational and ongoing cost can influence viability of a project.

•  Innovative operational strategies can minimise running costs.

•  Smart design solutions can minimise tunnel closures thereby improving level of service or availability of the tunnel.

•  Clever use of equipment layouts and arrangements can minimise recovery time post incident.

Example - Whole of Life Costs

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Developed NZ specific supplement for NZ tunnels

Caters for both new and existing road tunnels

Focussed on minimising both physical provisions and Whole of Life costs

Utilises risk to determine appropriateness of outcomes

New Zealand’s approach to Austroads

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Austroads guide to road tunnels allows the provision of performance based design and innovation. To achieve better project outcomes, all parties need to give appropriate consideration the performance of a design including the whole of life and operational costs.

The final word

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Thank-you