evacuation - time to go - boabc · 2015. 11. 21. · title: microsoft powerpoint - evacuation -...

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Evacuation – Time To Go

BOABC – May 27, 2014

PresentersFrankie Victor, EngL, BCQ

Jun H. Kim, BASc, EIT

GHL CONSULTANTS LTDBuilding Codes and Fire Science

950 – 409 Granville StreetVancouver, BC V6C 1T2

Phone 604 689 4449Fax 604 689 4419

www.ghl.ca1

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Copyright and Limitations

This presentation is conceptual and for educationalpurposes only. GHL takes no responsibility for applicationof any concepts or interpretations in this presentation tospecific projects unless specifically retained for that project.

This presentation is intended to be presented by GHL andthese slides must not be considered complete orexhaustive.

This presentation is a copyright of GHL Consultants Ltd andall rights are reserved.

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GHL’s Role

To know and understand the Code.

To know and understand the fire science behind the Code.

To assist in correct application of the Code.

To develop new solutions based on fire science to enable creative safe buildings.

To understand the needs of the client and of the Authorities and First Responders.

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GHL Team

7 Engineers, 4 with Master’s degrees in fire science

1 Architect

4 Certified Professionals (CPs)

2 former Building Officials

4 Building Code Qualified (BCQ)

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Building Code Committee Work

CP Committee (David Graham)

APEGBC Building Code Committee (John Buscemi)

BC Building Code Appeal Board (Frankie Victor)

City of Vancouver Building Bylaw Appeal Board (Teddy Lai)

BC Building Code Interpretation Committee (Teddy Lai)

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Building Code Approach To Risk

Buildings are subject to risks:

Code compliance ≠ no risk. Code compliance = risks at

acceptable level.

Failure will occur:

Limit it to an acceptable level.

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Building Code’s Building

The Building Code’s ‘building’ has:

Maximum travel distance Exits at full capacity Minimum ceiling height (2100mm) Minimum access to exit width (1100mm corridors) 6m dead‐ends in public corridors

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Base = unsprinklered floor area, 30m travel distance

High‐hazard industrial ‐ 5m = 25m Sprinkler* + 15m = 45m Service space + 20m = 50m Open air storage garage + 30m = 60m Perimeter exits 60m apart unlimited travel distance Public corridor** travel distance x 2 “Mall” corridor + 75m = 105m (50% of occupants)

* Does not apply to high-hazard industrial occupancies** Does not apply to “mall” corridors 8

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Example ‐ 45m travel distance, 2 exits, 2.1m ceiling height.

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Elements of Evacuation

Geometry – dimensional and spatial features of the space. Demographics – characteristics of occupants; mobility. Psychology – potential occupant behaviour in fires. Tenability – visibility, breathability, toxicity, heat.

The following presentation focuses primarily on Geometry, which can be expressed in terms of time.

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Travel distance translates to time to walk across the room. All else being equal, increasing travel distance simply

increases time to evacuate.

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Geometry – Travel Distance

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Geometry – Travel Distance

Pathfinder is an agent-based emergency egress simulator developed by Thunderhead Engineering Inc. It utilizes the floor layout, occupant load and predictable elements of occupant behaviour as input to simulate the movement time. The simulator has been well validated through comparison to hand calculations, real life experiments and other software.

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Exit capacity (width) translates to time to pass through a corridor, door or down a stair.

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Geometry – Exit Capacity

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914mm

1828mm


914mm

1828mm

Same floor area. Same occupant load.Increased exit capacity = reduced time.

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2 x 1828mm = 3656mm4 x 914mm = 3656mm

Geometry – Exit CapacityIncreasing number of exits without increased aggregate width has no impact.

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Occupant load determines queuing time.Higher occupant load / longer queue / increased time.

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1.2m2/person

1.2m2/person120 persons

180 persons

Geometry – Exit CapacitySame exit capacity. Same number of exits.Higher occupant load = increased time to egress.

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60 persons10m x 10m

60 persons15m x 15m

Geometry – Exit CapacitySame exit capacity. Same occupant load.Smaller floor area = shorter travel distance.Equal time to egress.

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The Building Code’s factors for exit capacity are a simplified method of determining time to pass through a corridor, door or down a stair.

Geometry – Configuration of Exits

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Effective width= 4 x (914mm-300mm)= 3536mm

2 x 1828mm = 3656mm4 x 914mm = 3656mm

Effective width= 2 x (1828mm-300mm)= 3596mm

Geometry – Configuration of ExitsReduced total effective width = increased time to egress.

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Geometry – Configuration of Exits,Pinch Points and Obstructions

Elements that hinder egress by creating pinch points or reducing capacity of access to exit:

Vestibules at exits (interconnected floor space).

Use of entry for ticket collecting, security, displays.

Retail anti‐theft equipment.

Turnstiles.

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Geometry – Ceiling Height

Relationship between ceiling height, or volume of space, and time to egress is codified in Sentence 3.4.2.5.(1):

Corridor 1100mm x 2100mm / Travel distance 45m

Corridor 9000mm x 4000mm / Travel distance 105m

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Ceiling height translates to time before smoke descends to head level.

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Occupants with locomotive disability are considered in the average occupant travel speed.

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Demographics

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Psychology

Human behaviour is predictable….and unpredictable.

True “panic” is mostly a myth per studies and expert opinion.• R.F. Fahy, G. Proulx. ‘Panic’

and human behaviour in fire. (2009)

Not necessary to consider in most timed egress analyses.

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Psychology – Human Behaviour

Human behaviour can be predicted to a degree:

Behaviour upon alert to a hazard depends on occupancy: Nightclub – unfamiliar, dark, crowded, impaired,

noisy. Home/work – familiar, sense of ownership,

protective of others. School – familiar, additional preparedness,

leadership. Weather, gender, commitment to a task, alone or

in a group, focal point/leader.27

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Psychology – Human Behaviour

Psychology is independent of timed egress analysis.

Not necessary to try and predict behaviour prior to movement provided comparison is of the same:

People Space Conditions

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Psychology - Panic What is panic? An overwhelming fear, with or without

cause, that produces an irrational response and may spread through a group.

When do people panic? When they can see no way out of a situation.

When does it matter? When it causes action without assessment of safety

What do people mean when they say panic? What do building officials mean when they say panic?Real panic in an emergency is rare; experts considered it a myth since about 1970…but the movies and news channels like it.

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Psychology – Timed Egress AnalysisTimed egress analysis is a comparison of the measurable elements of evacuation. (SFPE Handbook 4th Ed.)Available Safe Egress Time (ASET)

Required Safe Egress Time (RSET) Margin of Safety

Evacuation Time

Pre‐movement Movement

Response

Recognition

Alarm

Detection

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Psychology – Timed Egress Analysis

Available Safe Egress Time (ASET)

Required Safe Egress Time (RSET) Margin of Safety

Movement Time

Detection / Alarm

Alert stage can be adjusted by detection (smoke detector activates sooner than sprinkler)

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Tenability

Upper Layer Height Visibility Heat flux / Temperature Toxicity

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Tenability

Two types of computer models are used to gauge tenability:

Zone Model: Upper layer height Simpler spaces

CFD Model: Tenability parameters 3D complex spaces

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Tenability

Where a straight comparison to Building Code scenarios doesn’t tell the whole story: Don’t meet cumulative exit

capacity in an interconnected floor space.

Using open stair for egress. Converging egress routes.

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Elements of Evacuation

Geometry – dimensional and spatial features of the space.

Demographics – characteristics of occupants; mobility.

Psychology – potential occupant behaviour in fires.

Tenability – visibility, breathability, toxicity, heat.

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Hand Calculation

Time to egress is the time for either:

First occupant to reach door (t1) + time to queue at door (t2)

OR

Last occupant to reach door (t3)

Time to commence movement is not considered; assumed to be the same for Building Code and actual scenarios.

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Hand Calculation

Example: Comparing Building Code and alternative solution

Building Code Scenario Alternative Solution

Travel Distance 45m 60m

Exits 2 x 914mm door 2 x 914mm door

Occupant Load 2 x 914 ÷ 6.1 = 300 2 x 914 ÷ 6.1 = 300

Assumption Nearest person 5m from exit

Furthest persons 45m from exit

Nearest person 5m from exit

Furthest person 60m from exit

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Hand Calculation

Queuing (t2) is the limiting factor, hence 15m extra travel distance does not contribute to added evacuation time.

*assumed 5m for nearest occupant to an exit. This may vary depending on floor layout.

Building Code Scenario Alternative Solution

t1* 5 1.1 4.5 5 1.1 4.5

t2 3002 0.914 0.3 1.32 185

3002 0.914 0.3 1.32 185

t3 45 1.1 41 60 1.1 55

t1 t2 185 4.5 189.5 t1 t2 185 4.5 189.5

t 189.5s 189.5s

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Project Examples

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1. Egress via Open Stair.2. Cumulative Exiting (interconnected floor space).3. Egress from Two Storey Dwelling Unit.4. Converging Egress (Department store travel distance).5. Parkade 70m Travel Distance.

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Example 1 – Egress via Open StairSingle exit and open egress stair.

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Sentence 3.4.2.1.(1) ‐ at least two exits required Building divided into two storey suites each served

by one exit from upper storey. Travel distance and exit capacity met by exit stair.

Open stair provided second egress route. Timed egress, smoke model to confirm tenability. Additional features included smoke detection for

early alert.

Example 1 – Egress via Open Stair

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Example 2 – Cumulative Exiting

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Sentence 3.4.3.2.(6) ‐ Exit stairs serving interconnected floor space based on cumulative occupant load.

Cumulative exiting not met. Used convenience stair leading to exit on 1st storey

as a means of egress. Timed egress, smoke model to confirm tenability. Additional features included smoke detection and

smoke exhaust to keep open stair tenable.

Example 2 – Cumulative Exiting

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Example 3 – Egress from Two Storey Dwelling Unit

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Sentence 3.3.4.4.(2) ‐ describes egress doors in multi‐level dwelling units at both the upper and lower storeys.

Egress door was not provided at the upper storey Timed egress confirmed increased egress of 3 seconds. Concern was tenability at route from upper storey. Smoke model confirmed tenable conditions. Draft stop was necessary. Additional features included smoke alarms for early

alert, emergency lighting linked to smoke alarm. Fire alarm annunciation – both storeys at lower.

Example 3 – Egress from Two Storey Dwelling Unit

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Example 4 – Converging Egress

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Mall Corridor

Back-of-house Corridor

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Example 4 – Converging Egress

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Clause 3.4.2.5.(1)(d) ‐ 50% of occupants exit via mall corridor with travel distance of 105m.

Rear corridor converged with mall corridor. Used mall corridor as a means of egress for 100% of

occupants. Timed egress, smoke model to confirm tenability. Additional features include passive smoke venting to

maintain tenability. Code compliant solution = tunnel out of the building.

Are people willing?

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Example 5 – Parkade 70m Travel Distance

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Example 5 – Parkade 70m Travel Distance

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Scenario

Number of Occupantsper Exit (persons)

MaximumTravel

Distance (m)

Time toEvacuate(sec)

1. Code Minimum using full door capacity 149 45 219

2. Proposed Scenario 54 70 110

Sentence 3.4.2.5.(1) ‐ prescribes 45m travel distance. Increased travel distance from centre areas. Increased total exit width (extra doors). Low occupant load eliminated queuing at exits. Timed egress. Additional features include exit signage, increased light

levels.

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Comparison of BC to IBC and NFPA 101 (sprinklered)

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Occupancy BC IBC NFPA 101

Assembly 45m 76m 76m

Care 45m 76m 61m

Business / service 45m 90m 91m

Residential 45m 76m 61m

Retail 45m 76m 76m

Industrial F1/F2/F3 25/45/45m 23/76/120m 30/122/unlimited

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Summary

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Building Code limits ‐ travel distance, ceiling height, exit capacity ‐ define a space, create a scenario.

Real‐life scenarios are compared to Building Code scenario.

Human behaviour is predictable / unpredictable. Can reduce detection / alert stage by smoke detection

(operate earlier than sprinklers). Can ‘buy time’ by increasing ceiling height or exit

capacity.

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Questions?GHL CONSULTANTS LTD

950 – 409 Granville StreetVancouver, BC

V6C 1T2

Phone 604 689 4449 Fax 604 689 4419

Email [email protected] / [email protected]

Web www.ghl.ca

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evacuation - time to go - boabc · 2015. 11. 21. · title: microsoft powerpoint - evacuation -...

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