Firesafe Issue 4.pdf - OneSteel

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Firesafe Issue 4.pdf - OneSteel

FireSafe

CASE STUDIES in

Structural steel

Fire safety engineering by design

Issue 4, May 2007

Alternative solutions in

Fire Safety Engineering

• Uncompromised safety

• Architectural flexibility

• Reduced construction costs

50 Lonsdale Street, Melbourne

www.onesteel.com


Welcome

Welcome to FireSafe Solutions Issue 4,

showcasing steel-framed retail projects

that have benefited from the application of

performance-based Fire Safety Engineering

assessments, to provide alternative solutions

using bare steel construction that can offer

benefits such as:

• INCREASED SAFETY LEVELS

• REDUCED BUILDING COSTS

• ARCHITECTURAL FLEXIBILITY

• FASTER CONSTRUCTION

Advertiser & Sunday Mail Building

Adelaide

THE STRUCTURAL SYSTEM INCLUDES STEEL

HOLLOW SECTION COLUMNS, TYPICALLY

457 MM IN DIAMETER.

4

3

2

1

G

B

office

office

office

office

office

carpark

Figure 1

The Advertiser office building

incorporates 5 levels of offices above a

basement carpark (see Figure 1). The

floor area is approximately 3200 m 2

per storey. It has two full-height atria

connecting all office levels. Each

atrium has plan dimensions of 20.2 m

by 5.8 m. There are three fire-isolated

stairs in addition to a non-required

stair in an atrium.

The structural system includes steel

hollow section columns, typically

457 mm in diameter, filled with

concrete and reinforced internally.

Floor slabs are composite profiled steel

sheeting slabs. Steel beams include

shear connectors to achieve composite

action with the floor slab.

The building is sprinkler-protected

throughout.

atrium

The effective height of the building is

approximately 19.5 m, being less than

the height of 25 m at which sprinklers

are required under DTS. Sprinkler

protection is required under DTS due

to the presence of the atria, however.

Sprinkler protection of the carpark is

also required under DTS, as it contains

more than 40 car spaces.

The building has been approved with

structural fire protection in the office

levels as follows:

• all columns are protected to achieve

an FRL of 120/-/-

• the primary beams, which span

across the shorter dimension of the

building, are protected to achieve

an FRL of 60/-/-

• all other beams are unprotected (all

beams have an exposed surface area

to mass ratio of less than 30 m 2 /t)

The sprinkler system incorporates the

following features:

• separate sprinkler systems for atria

and offices;

• monitored valves at each storey;

• provision for end-of-line testing; and

• fast response heads.

In addition, a sprinkler management

system was specified, incorporating:

• no two zones to be isolated at any

one time;

• sprinkler zones to be isolated only

for single days, reinstated a night;

• fire loads to be reduced if periods

of extended isolation are

unavoidable; and

• end-of-line testing to be performed

after any isolation.

The above fire safety solution has

been justified largely on the basis that

the benefits of the sprinkler system

enhancements provided outweigh any

additional hazard associated with the

reduced FRL of the floor system.

FireSafe : Fire Safety Engineering by Design | Page 2


Furthermore, it was demonstrated

that even a standard sprinkler system

provides about three times the benefit

of fire-rated construction with respect

to limiting the rate of occurrence of

large fires. Since the rate of deaths

and injuries from fires correlates

directly with the rate of occurrence

of large fires, the BCA objectives

are more effectively satisfied using

sprinkler protection rather than

protection of structural elements.

More specifically, the impact of the

proposed solution upon fire spread,

detection and suppression, occupant

avoidance and fire brigade intervention

were considered, as follows:

• fire spread – the enhanced sprinkler

system provides benefits with regard

to reduced likelihood of fire spread,

with sprinklers being more likely to

stop spread than fire-rated floors,

due to the openings and free edges

which always occur. The full-scale

Cardington fire tests [1]

demonstrated the robustness of the

structural form utlilised.

• detection and suppression – the

enhanced sprinkler system

increases reliability.

• occupant avoidance – the egress

time will be about 10 mins,

whereas the real behaviour provides

safety for many times that required.

• fire brigade intervention – fire brigade

effectiveness is assisted by the

enhancements to the sprinkler system.

• adjacent buildings – the

enhancements to the sprinkler

system reduce the probability of a

large fire occurring, thus

outweighing the impact of the

reduced FRL of the floor system.

References

1. Kirby, B et al, “The Behaviour of

Multi-Storey Steel Framed

Buildings in Fire”, British Steel

Corporation, 1999.

CLIENT

Advertiser Newspapers Pty

Limited

ARCHITECTS

E.G.O Fender Katsalidis

PROJECT MANAGER

E.G.O Group

STRUCTURAL ENGINEER

Wallbridge & Gilbert

BUILDING CONTRACTOR

Baulderstone Hornibrook

ADVERTISER BUILDING – FIRE RESISTANCE REQUIREMENTS SUMMARY

BUILDING ELEMENT

ELEMENT REQUIREMENT

DTS

Office – beams 120/-/-

Alternative Solution

Primary beams: 60/-/-

Other beams: unprotected

Office – columns 120/-/- 120/-/-

Carpark – beams

60/-/- or

30 m 2 /t

30 m 2 /t

Carpark – columns 60/-/- 60/-/-

Sprinklers Yes Yes (with enhancements)

Table 1

FireSafe : Fire Safety Engineering by Design | Page3


Latitude East Building

Sydney

AN ATRIUM OF DIMENSIONS 29 M BY 14.5 M

WILL CONNECT ALL OF LEVELS 12 TO 22.

OWNER

Multiplex

DEVELOPER

Multiplex

ARCHITECT

Crone Partners

STRUCTURAL ENGINEERS

Taylor Thomson Whitting

BUILDER

Multiplex Construction

FIRE ENGINEER

Norman Disney & Young

This new building forms part

of the Latitude development.

A podium structure comprising 8

levels of basement carparking and 3

levels of retail has previously been

extended above its west side with the

construction of the 50-storey Latitude

building. The new Latitude East

building currently under construction

comprises 11 storeys above the east

side of the podium, forming Levels 12

to 22. The new storeys will be used

for offices throughout.

The external dimensions of the

building will be approximately 67 m

by 46 m. An atrium of dimensions

29 m by 14.5 m will connect all of

Levels 12 to 22. Because of this

atrium, there will be no central core.

Overall building stability will mainly be

provided by two concrete structures,

located near the north-east and

south-west corners of the building.

The façade of the building will be fully

glazed on all sides, with a separation

distance to any adjacent building of

more than 3 m on all sides.

There will be two fire-isolated stairs.

These will be partially supported

on steel beams and encased

with masonry walls. In addition,

there will be a non-fire-isolated

communication stair within the

atrium space, enclosed with glazing.

We understand that this stair will

not be classified as a designated or

required exit.

The building will be fully sprinklerprotected

throughout, which is

required under the deemed-to-satisfy

(DTS) provisions of the Building Code

of Australia. The sprinkler system

will be enhanced by the provision of

monitored floor-by-floor valving and

end-of-line testing.

The structure of the new building will

comprise steel beams and columns,

composite slabs and shear studs

providing composite action between

the beams and the slab. Columns will

generally be steel hollow sections of

610 mm diameter, concrete-filled,

containing longitudinal reinforcement

with 40 mm cover and designed

for ambient strength, ignoring the

contribution of the external steel.

FireSafe: Fire Safety Engineering by Design | Page


The building structure will be fireprotected

as follows:

• all columns will be protected to

achieve an FRL of 120/-/-;

• all beams framing directly into

columns at the floor between

Levels 18 and 19 and below will

be protected to achieve an FRL

of 60/-/-;

• secondary beams spanning only

between other beams will not be

protected;

• cantilever beams will not be

protected; and

• transfer beams supporting columns

(if any) will be protected to achieve

an FRL of 120/-/-.

In addition, any beams which support

fire-isolated stairs (either directly or

indirectly) will be protected to achieve

an FRL of 120/-/-.

All steel beams will be left

unprotected at the following levels:

• the floor between Levels 19 and

20, which supports the top office

level; and

• the floor between Levels 20 and

21, which supports the rooftop

plant room.

The plant room will not contain any

equipment required for fire brigade

intervention.

The columns will be required to

achieve an FRL of at least 120/-/-, but

in practice the typical columns being

used are likely to achieve an FRL

between 180/-/- and 240/-/-.

The structural protection solution

was approved on the basis of the

beneficial effect of the enhancements

to the sprinkler system in

substantially reducing the probability

of sprinkler failure, in addition to the

understanding of whole-structure

behaviour gained through full-scale

fire testing conducted at Cardington in

the UK and BHP Research in Australia.

The most likely cause of sprinkler

failure is deliberate isolation of parts

of the system for the purpose of

refurbishment. The proposed sprinkler

design measures will directly mitigate

the effects of this hazard.

Given the large atrium and

consequent lack of a central core

structure (a building feature not

included in the Cardington tests), it

was necessary to protect all beams

framing directly into columns and

thus enhance the stability of the

columns.

The philosophy for not protecting the

floor of the top habitable level was

that the columns passing through this

level are not critical in terms of the

fire safety objectives. Thus, if a fire

occurs in the second top habitable

level (Level 19), the floor of the top

level may deflect and the occupants

will have strong cues to evacuate. If

these columns should fail, only the

roof above would be affected, which

is of limited importance with respect

to life safety. In the current case, the

plant room may also be affected,

but this also is extremely unlikely

to have any impact upon life safety.

Furthermore, regarding fire brigade

safety, any deformations will occur in

a gradual manner, providing adequate

warning to firefighters to enable

escape as necessary.

LATITUDE EAST BUILDING – FIRE RESISTANCE REQUIREMENTS SUMMARY

BUILDING ELEMENT

DTS

office beams 120/-/-

ELEMENT REQUIREMENT

Alternative Solution

Beams framing directly into

columns: 60/-/-

Other beams: unprotected

Top two levels: all beams

unprotected

office columns 120/-/- 120/-/-

sprinklers Yes Yes (with enhancements)

Table 2

FireSafe: Fire Safety Engineering by Design | Page


Flinder's Link Building

Adelaide

Figure 2: Cross-Section Elevation of

Flinders Link Building

DEVELOPER / BUILDER

PT Building Services,

Kambitsis Group and

Hindmarsh Group

ARCHITECT

HASSELL

STRUCTURAL ENGINEER

Wallbridge & Gilbert

The Flinders Link project incorporates

two adjoining buildings, currently

known as Stage 2 and Stage 5. The

Stage 2 building incorporates 9 storeys

of carparks with 2 storeys of offices

above, while the Stage 5 building

incorporates a retail storey, a carpark

storey and 7 storeys of offices above.

The top two storeys of offices in each

building are linked (see Figure 2).

The buildings have been constructed

using a structural steel frame with

composite floor slabs and composite

action between the floor slabs and the

steel beams.

The buildings are sprinkler-protected

throughout. As they are both over 25 m

in effective height, these sprinklers are

required under DTS.

In the Stage 2 building, the carpark

storeys at Levels 5 and below were

protected in accordance with DTS,

resulting in unprotected steel beams

throughout and concrete-filled steel

hollow section columns achieving an

FRL of 60/-/-.

The structural fire protection at Level

6 has been approved as follows:

• all columns are protected to

achieve an FRL of 60/-/-

• all beams in the floor above Level 6

which span directly into columns

are protected to achieve an FRL of

60/-/-

• all other beams are unprotected.

In the Stage 5 building, the following

protection has been used:

• all columns are concrete-filled

steel hollow sections achieving an

FRL of 120/-/-

• all beams which span directly into

columns are protected to achieve

an FRL of 60/-/-

• all other beams are unprotected.

The sprinkler system incorporates the

following features:

• monitored valves at each storey;

• provision for end-of-line testing; and

• fast response heads.

In addition, a sprinkler management

system was specified, incorporating:

• no two adjoining zones to be

isolated at any one time;

• sprinkler zones to be isolated only

for single days, reinstated a night;

• wood-equivalent fire loads per unit

floor area to be reduced below

10 kg/m 2 if periods of extended

isolation are unavoidable; and

• end-of-line testing to be performed

after any isolation.

Table 3

Approval for this solution was

obtained on the basis that the

benefits of the enhanced sprinkler

system outweighed any additional

hazard due to the reduction in FRL.

Also discussed was the greater

effectiveness of sprinklers in

comparison with FRLs in satisfying

the BCA objectives.

Test evidence was also presented

from the Cardington fire tests [1]

and further work demonstrating the

robustness of partially protected floor

systems by Bailey [2] was used.

References

1. Kirby, B et al, “The Behaviour of

Multi-Storey Steel Framed

Buildings in Fire”, British Steel

Corporation, 1999.

2. Bailey, C G and Toh, W S,

“Experimental Behaviour of

Concrete Floor Slabs at Ambient

and Elevated Temperatures”,

Fourth International Workshop on

Structures in Fire, Portugal, 2006.

FLINDERS LINK BUILDING – FIRE RESISTANCE REQUIREMENTS SUMMARY

BUILDING ELEMENT

DTS

Office – beams 120/-/-

ELEMENT REQUIREMENT

Alternative Solution

Beams framing directly into columns:

Stage 2, Level 6: 60/-/- Stage 5: 120/-/-

Other beams: unprotected

Office – columns 120/-/- Stage 2, Level 6: 60/-/- Stage 5: 120/-/-

Retail – beams 180/-/-

Retail – columns 180/-/- 120/-/-

Carpark – beams

60/-/- or

30 m 2 /t

Beams framing directly into columns: 120/-/-

Other beams: unprotected

30 m 2 /t

Carpark – columns 60/-/- 60/-/-

Sprinklers Yes Yes (with enhancements)

FireSafe : Fire Safety Engineering by Design | Page


50 Londsdale Street

Melbourne

5 LEVELS OF BASEMENT

CARPARK AND 33 STOREYS

ABOVE GROUND.

The new office building at 50

Lonsdale Street is known as The

Urban Workshop. It incorporates 5

levels of basement carpark and 33

storeys above ground. A 5-storey

atrium connects all levels between

Ground Floor and Level 4. There are

retail spaces at Ground Floor, Level

1 and Level 2. The remainder of the

building is generally office space.

The below-ground part of the building

is reinforced concrete construction,

while the above-ground part is steelframe

with composite floor slabs and

has composite action between the

beams and the slab.

All primary and secondary steel

beams are unprotected throughout

the building, with the exception of

beams passing through the atrium.

All columns and transfer beams are

protected in accordance with DTS, ie

120/-/- FRL in offices and 180/-/- FRL

in retail spaces.

The building is sprinkler-protected

throughout. Enhancements to the

sprinkler system have been included

to provide increased reliability in

comparison with a DTS-compliant

design. These enhancements include

floor-by-floor monitored valves,

end-of-line testing and specific

management procedures.

with the structural engineers for the

project to evaluate the performance

of both the connections and the

columns when the unprotected

beams are at elevated temperatures.

This scenario assumes sprinkler

failure and is thus a low-probability

event.

A risk assessment has been

performed and it has been shown

that, given the enhancements

to be included in the design, the

probability of structural failure of the

unprotected steel beams in fire will

be no greater than that of the beams

at ambient temperature.

DEVELOPER

ISPT

ARCHITECT

John Wardle Architects in

association with Hassell

and NH Architecture

STRUCTURAL ENGINEER

Connell Mott MacDonald

BUILDER

Multiplex Constructions

FIRE ENGINEERING

Norman Disney & Young

Use has been made of the results of

the large-scale fire tests conducted

on a similar structural system,

being the 140 William Street tests in

Australia and the Cardington tests in

the UK. In addition, consideration has

been given to the robustness of the

structural system in the event of a

fully-developed fire at any one storey.

The fire safety engineers have worked

50 LONDSDALE STREET – FIRE RESISTANCE REQUIREMENTS SUMMARY

BUILDING ELEMENT

ELEMENT REQUIREMENT

DTS

Alternative Solution

Office – beams 120/-/-

Office – columns,

transfer beams

Retail – beams 180/-/-

Retail – columns,

transfer beams

120/-/- 120/-/-

180/-/- 180/-/-

Atrium: 120/-/-

Other: unprotected

Atrium: 120/-/-

Other: unprotected

Sprinklers Yes Yes (with enhancements)

Table 4

FireSafe : Fire Safety Engineering by Design | Page


Forum Apartments

Adelaide

THE BUILDING INCLUDES SOME 2-STOREY

AND 3-STOREY APARTMENTS BETWEEN

GROUND FLOOR AND LEVEL 2.

5

4

3

2

1

G

B1

apartments

apartments

apartments

apartments

apartments

carpark / office / retail

carpark

light well / walkways

internal

windows

2-storey &

3-storey

apartments

The structural protection is as follows:

• the basement carpark is constructed

using reinforced concrete and

achieves an FRL complying with DTS

(ie 60/60/60 FRL)

• columns and primary beams at

Ground Floor are protected to

achieve an FRL of 60/-/-

• secondary beams at Ground Floor

are unprotected

• steel beams and columns are

unprotected in apartment storeys.

The solution was approved on the basis

that, in the apartment storeys, sprinklers

are more effective in achieving the BCA

objectives than FRLs. At Ground Floor,

the required FRL of 60/-/- has been

determined by consideration of the

likely maximum fire size and duration

and estimation of the FRL necessary to

survive burnout.

Figure 3: Cross-Section Elevation of Forum Apartments Building

DEVELOPER/BUILDER

Commercial & General

ARCHITECT

David Dawson Architects

STRUCTURAL ENGINEER

KBR

FABRICATOR

MWS Group of Companies

The Forum Stage 2 building has a

basement carpark, mixed uses at

Ground Floor and five storeys of

apartments above. Ground Floor

includes small areas of carpark,

office, retail and apartment uses.

The building includes some 2-storey

and 3-storey apartments between

Ground Floor and Level 2.

The building has a light well connecting

Levels 1 to 5. The apartments have

internal windows facing this light well.

The building is sprinkler-protected

throughout. It has an effective height of

less than 25 m. The carpark contains

more than 40 car spaces.

FORUM APARTMENTS – FIRE RESISTANCE REQUIREMENTS SUMMARY

BUILDING ELEMENT

DTS

ELEMENT REQUIREMENT

Apartments – beams 90/-/- Unprotected

Apartments – columns 90/-/- Unprotected

Retail / office – beams 180/-/-

Carpark – beams

60/-/- or

30 m 2 /t

Alternative Solution

Primary beams: 60/-/-

Other beams: unprotected

Retail / office – columns 180/-/- 60/-/-

60/-/-

Carpark – columns 60/-/- 60/-/-

Sprinklers Yes Yes (with enhancements)

Table 5

9 3 2 0 0 7 5 0 4 5 6 3 0

This publication has been prepared by OneSteel Market Mills an operating business group of which OneSteel Manufacturing Pty Limited ABN 42 004 651 325, OneSteel NSW Pty

Limited ABN 59 003 312 892, OneSteel Wire Pty Limited ABN 59 000 010 873, OneSteel Trading Pty Limited ABN 50 007 519 646, OneSteel MBS Pty Limited ABN 76 096 273

979 are a part. Please note that any specifications or technical data referred to in this publication are subject to change and/or variation or improvement without notice and no

warranty as to their suitability for any use is made. Users of this publication - to ensure accuracy and adequacy for their purposes - are requested to check the information provided

in this publication to satisfy themselves as to its appropriateness and not to rely on the information without first doing so. Unless required by law, the company cannot accept any

responsibility for any loss, damage or consequence resulting from the use of this publication. Photographs shown are representative only of typical applications, current at May 2007.

This publication is not an offer to trade and shall not form any part of the trading terms in any transaction. © Copyright 2002-2007. OneSteel Market Manufacturing Pty Limited,

ABN 42 004 651 325. Registered Trademarks of OneSteel Market Mills: 300PLUS ® and FireSafe. Issue 4 Printed May 2007. 17530

ONESTEEL DIRECT Freecall 1800 178 335 Website www.onesteel.com Freefax 1800 101 141 Email onesteeldirect@onesteel.com

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