Life Safety and Structural Fire Safety of Mega Underground Caverns in Singapore · 2014-10-10 ·...

Life Safety and Structural Fire Safety of Mega Underground Caverns

in Singapore

Principal Investigator: Prof TAN Kang Hai Nanyang Technological University

1

Co-PIs: Asst Prof Yang Enhua, Asst Prof Wan Man Pun Asst Prof Aravind Desari, Dr Nguyen Minh Phuong

Collaborators: Mr Ng Kian Wee and Mr Koh Chwee (JTC)

Director and AC Chris Tan and Major Chong (SCDF) Mr Ho Chee Leong and Dr Rick Tan (DSTA)

Mr Peter Weber

International Collaborators: Prof Venkatesh Kodur Michigan State University) Prof Yao Yao (Northwestern Ploytechnic Unviersity, Xian, China)

Fire hazards of underground structures

Challenges to underground fire safety

1. Occupants have to escape upwards.

2. Hot smoke entering stair cases or vertical shaft will rise upwards and cause hazards to movements.

3. Fire fighter travelling against rising hot smoke.

4. Fire fighting, search and rescue are all difficult as underground caverns have no windows and the visibility is depending on power supply.

5. Smoke tends to be trapped in underground structures.

6. Heat accumulation more severe.

Research Scope

To support development of safe, robust and cost-effective regulatory requirements for fire safety of Singapore underground structures.

• Study the fire safety design of two Singapore underground developments, i.e. Underground Science City (USC) and Underground Warehouse Logistic Facility (UWLF).

• Collaborate closely with JTC, SCDF and DSTA to address practical design issues of underground fire safety design in Singapore.

• Contribute to L2NIC objectives through creation of space

4

Research Objectives

• This research provides an integrated fire safety assessment of underground developments in Singapore using a performance-based approach.

• SCDF has approved performance-based approach for a number of prestigious projects in Singapore.

• The fire safety of Singapore underground development will be assessed holistically with SCDF.

Evacuation strategy

Structural fire safety

Fire detection

and suppression

Provide passive protection system

Provide active protection system

Provide life safety

5

Research novelties

1. To develop a safe, robust and cost-effective fire safety design for Singapore underground developments through a holistic assessment including:

i. Fire detection and suppression system (active

protection system).

ii. Evacuation strategies (life safety system).

iii. Structural stability (passive protection system)

2. To enhance fire resistance of underground structures through usage of novel materials:

i. Engineered Cementitious Concrete.

ii. Carbon nanotube enhanced concrete.

iii. Concrete with metallic and/or polymer fibres

iv. Spray applied polyurea-based with halogen-free

fire retardants.

6

Part 1.

Review International Fire Codes, propose & obtain agreed fire size and loads for

cases applicable to USC & UWLF

SCDF

Accept ?Engage SCDFNo

Part 2.

Evaluate Pre-Flashover Fire Fighting Strategies, e.g. Very Early Detection, for

all possible cases

Yes

SCDF

assessment on

effectiveness

Yes

Engage

SCDF

Determine fire rating using

Performance-Based approach

Part 3. Conduct structural Fire Safety

Part 4a. Conduct evacuation simulation

Part 4b. Conduct smoke control simulation

Part 5. Manual/Automated control of suppression systems.

Part 6. Develop SUFM

2- or 3-hour FRP ?

R&D for fire protection material

Part 7a,b,c. Fire protection materials.

Part 7d. Structural fire testing

No

SCDFAccept ?

Yes Engage SCDF

Prepare Report to provide scientific data for SCDF to update of Underground Fire Code

Yes

End

Co

llab

ora

tio

n w

ith

SC

DF,

JTC

an

d D

STA

No

ISO Standard Fire Tests

Part 7e. Fire protection on beams, columns, slabs and walls.

No

Methodology

• SCDF, DSTA and JTC • Michigan State Univ and • Northwestern Poly. Univ., China

7

Role of team members

NTU faculty members: 4

Research staff members : 8

Government agencies: 3

Private company: 1

Duration: 4 years.

Review interational Fire Codes.

Evaluate Pre-Flashover

Fire Fighting Strategies.

Conceptual Stage

· General reviewof the Base Concep

Design and make comparision with Similar

codes in other countries

· Identify critical fire scenarios for UWLF

and USC

Data from previous

feasibility study (JTC)

Discussion with authorities about current

design codes

(SCDF, DSTA and JTC)

Propose Performance Based Method to

evaluate the requirement of Fire Safety of

current design codes

Structural fire

Safety

Assessments on

EvacuationManual/Automated

Suppression system

Assessments on Smoke

controls

Optimization processInput benefits from

application of SUFM

Presentation and discussion

with SCDF, DSTA and JTC

Scientific data to the fire authorities to support the

development of safe, robust and cost-effective

regulatory requirements

Pre

pa

re R

ep

ort

to

pro

vid

e to

SC

DF

to

up

da

te o

f U

nd

erg

rou

nd

Fire

Co

de

Base line

estimation

Prof. TAN Kang Hai

Prof. TAN Kang Hai

Prof. Tan K. H

Asst. Prof. Yang E. H.

Asst. Prof. Aravind B. D.

Mr. Peter Webber

Prof. TAN K. H. Prof. Tan K. H. Asst. Prof. Wan M. P.

PI with all Collaborators

Prof. Tan K. H.

8

Deliverables for the first objectives 1. To develop a safe and economic design guide for

Singapore underground developments;

2. To recommend amendments to existing prescriptive Fire Code for underground mega structures in Singapore.

3. To improve fire safety and reduce fire risks for underground space utilization;

4. To reduce overall construction cost by having smaller concrete elements.

9

Deliverables for the second objective 1. State-of-the-art Review: to review previous

publication works on fire-resistant construction materials and fire protection coatings.

2. Material fire test: four types of construction materials and Structural tests to examine the effectiveness of these materials.

3. Full scale fire test at an accredited lab to certify the application of new materials to actual size.

4. Final report will provide economic design guideline with detailed information of columns, beams, walls and slabs.

10

Potential contributions and innovation

The potential innovations are:

1. Through the findings of critical parameters that control evacuation in underground structures, SCDF may consider incorporating certain flexible features of performance-based approach for deep underground structures.

2. The development of SUFM (Part 6) will be useful to security agencies since it can manage and visualise the GIS data and Cell Grid system. Through this application, the Fire Command Centre with CCTV can develop phased evacuation strategy of occupants.

3. From application of novelty material to increase fire resistance (Part 7), the research outcomes include saving significant construction cost.

11

Detailed explanations of the project

5/30/2014 12

Contents

Part 1: Review of 1st world codes for fire safety of underground mega space

Part 2: Evaluate pre-flashover Fire Fighting Strategies for all possible cases

Part3: Post-flashover fire analysis of structural safety of underground space

Part 4: Assessment of Simultaneous Evacuation from Cavern Complex

Part 5: Study on Automatic/Manual control of Suppression System

Part 6: Developing the Spatial Underground Fire Mitigation System

Part 7a: Spray-applied polyurea-based with halogen-free fire retardants as a fire resistance coating.

Part 7b: Application of carbon-nanotube to enhance fire resistance

Part 7c: Embedded polymeric fiber and/or steel fiber in concrete mix

Part 7d:Testing of structural concrete members and embedded fibres

Part 7e: ISO certificated fire test

5/30/2014 Page: 13

Singapore fire safety code

The fire authority of Singapore has issued two prescriptive fire codes:

– Fire code (2007)

– Fire Safety requirements for Mega underground developments (2012).

Fire safety of underground structures needs to comply with these codes. For all structural elements, refer to Clause 3.2c:

“All elements of structure/compartment of each cavern unit shall have fire resistance rating of at least 4 hours”

The requirement affects will cause structural elements to become so stocky and massive that pose difficulty in underground construction.


Singapore Underground Science City, conceptual design

• Objectives: Provide scientific data to the relevant authorities to support the development of safe, robust and cost-effective regulatory requirements.


The fire safety of Singapore has two prescriptive fire codes:


–Fire Safety requirements for Mega Underground developments (2012).

Fire safety of Underground Caverns needs to follows these

codes. However, there are concerns in these aspects:

– Structural fire protection.

– Life Safety including:

• Evacuation;

• Application of Spatial Underground Fire Mitigation to help in the identification of fire source, evacuation, and rescue operations

Part 1. Review of first world codes

• Structural Fire Precautions

– The element of structure/compartment of each cavern unit shall have fire resistance rating of at least 4 hrs. [Clause 3.2 (c)]

• Vehicular Access

– Fire engine access road having minimum 4m width and overhead clearance of at least 4.5m for access by pump appliance shall be provided for fire-fighters and rescuers to conduct fire fighting and rescue operations. [Clause 3.3 (a)]

– Provision of alternative means of vehicle access into the underground development shall be considered on a case by case basis. [Clause 3.3 (b)]


Method:

a) Extensive review of fire safety for large and complex mega underground to maintain adequate level of protection from fire.

b) Include fire safety developments of some countries which have large underground systems such as Norway, Sweden, Switzerland, Hong Kong and Japan.

Deliverables:

Literature review on fire resistance requirements of underground structural members of available code in the world.

18


Method:

Study on Earlier Possible Automatic Fire Detection System including:

a) Analyse fire signature (thermal, particle size, temperature) based on study data

b) Identify suitable detection system. c) Analyse the performance and limitations of detection

systems (e.g., spacing, height, discharge rate) d) Model the response time of the proposed detection

system.

Deliverables:

a) Recommendations of suitable early fire detection system and report.

b) Modelling assessment of the response time of recommended early fire detection system and report.

c) Verification fire tests and predictions of results for JTC underground facilities.

Part 2. Automatic Early Detection System

Part 3. Post-flashover structural fire analysis

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Method:

1. Determine the fire load in consultation with SCDF;

2. Determine natural parametric fire curves;

3. Conduct CFD analysis using Fire Dynamic Simulators;

4. Distinguish the fire characteristics in cavern structures versus infrastructures;

5. Conduct a review between CFD and parametric fire;

6. Identify the type of fire curve and approach for subsequent structural fire analyses;

7. Conduct heat transfer analyses to ascertain temperature domains;

8. Determine temperature developments in concrete structures for worst fire scenario;

9. Assess stability of structures under fire; 10. Determine the failure criteria from Eurocode; 11. Establish the upper bound baseline to see if the

structure can satisfy 4-hour FR; 12. Conduct a sensitivity study for a range of fire curves to

obtain a range of structural performance; 13. Determine reduction on concrete volume for structural

members; 14. Produce a technical report 15. Engage a structural fire expert to review this part.

21


Deliverables:

a) To conduct a credible fire scenario (in agreement with SCDF) considering sprinklers and smoke extraction (if the latter can be modelled by the software).

b) To evaluate structural fire resistance of one or two concrete tunnel sections subjected to the worst fire scenario. Comments will be given with regard to

(i) structural stability of the sections after fire and

(ii) possibility of having reduced FR.

c) To assess the possibility of reduction in concrete cover and dimensions of concrete elements under realistic natural fires and to discuss the outcomes with FSSD;

d) To propose cost-effective fire protection schemes if really needed.

22


• Structural stability in fire condition – Time analysis:

1. Choose the worst fire scenario.

2. Evacuation analysis RSET.

3. Structural analysis fire resistance of the supporting structures.

Requirement for occupant safety: RSET + Safety margin < ASET.

Part 4a. Assessment of Evacuation

• Our evacuation software - FeSim (by Prof. Yuan Weifeng)


Part 4a: Evacuation Assessment

Deliverables:

a) Preliminary evacuation strategy and a report

b) Assessment of escape time from caverns, tunnels, protected corridors and entire complex in the worst fire scenarios as a lower bound baseline.

c) Assessment of possible routes into the complex to facilitate search & rescue operations by the CERT team and Fire Brigade.

d) Assessment of time taken for the search & rescue operations by Fire Brigade personnel.

e) Final evacuation strategy and report

25


Part 4b. Assessment of Engineered Smoke Control

Part 4b: Assessment of Engineered Smoke Control System

a) Propose and assess potential smoke control strategy for caverns, tunnels and protected corridors.

b) Perform CFD modelling and analysis for the aforementioned locations to substantiate the smoke control strategy.

c) Provide inputs on the smoke control provisions in the cavern complex to permit overall evacuation to be completed in 1 hr, 2 hr and 3 hr.

d) Incorporate tenable conditions in the cavern complex to permit for the overall evacuation strategy conducted above.

e) Determine the number of simulation runs through consultation with the FSSD.

f) Consider potential worst fire scenarios which will affect the capacity of the smoke control system in CFD smoke modelling.

g) Consider the impact of the study on the overall proposal of reduction in structural fire resistance level.

h) Highlight any potential deviations to the DTS provisions of the Singapore Fire Code for the Engineered Smoke Control System.

Part 4b: Assessment of Engineered Smoke Control System

Deliverables:

a) Preliminary smoke control strategy and report

b) CFD assessment of tenable conditions in caverns, tunnels and protected corridors during the worst fire scenarios as a lower bound baseline.

c) Preliminary smoke control strategy and report

d) Final CFD smoke control strategy and report

Part 4b. Assessment of Engineered Smoke Control

Study on using better means of fire suppression equipment by CERT

a) Analyse fire characteristic (growth rate, combustion yields) based on study data

b) Identify suitable manual and automatic fire suppression system

c) Analyse the performance or limitation of the manual fire suppression equipment (e.g., fire size, deployment time)

d) Develop a model that can provide design parameters for the automatic system

Part 5. Manual and Automated Suppression System

Part 6. Application of SUFM

Background:

• Difficult to direct the crowd during evacuation without a proper locating reference system.

• A locating reference system, namely, Cell Grid system is proposed.

• During a fire incident, after sizing the fire, if it is serious, the FCC will announce the location of the fire threat at a specific Cell Grid, e.g L1F2d, and issue evacuation instructions.

29

Part 6. Application of SUFM

Method:

a) Convert data for the following networks so that they are “GIS ready”.

i. Floor plans

ii. Fire alarm System network

iii. Fire-Fighting apparatus network

iv. Life-saving Apparatus network

b) Create suitable Cell Grid locating reference system for layers that have linkages with GIS data.

Deliverable:

a) Design an application for FCC to manage and visualise the GIS data and Cell Grid system.

b) The work will include provision of specifications and maintenance plan for this critical safety system.

30

31

R240-500x500 mm

R180-400x400 mm

R120-350x350 mm

Columns

Based on standard section 300x300mm with

45mm cover for RE90

Part 7. Fire resistance to EC2 Part 1-2

32

Walls

R240 - 230mm

R180 – 210mm

R120 – 170mm

Based on standard section 140mm with 10mm cover for RE90


• The increase of concrete volumes with different fire ratings based on design followed the prescriptive code EC2 Part 1-2 (2005).

The design will result in exorbitant cost and massive dimensions which will cause difficulties in underground construction.

36%

78%

178%

21%

50%

64%

0%

40%

80%

120%

160%

200%

60 90 120 150 180 210 240 270

Incr

eas

e v

olu

mn

e o

f co

ncr

ete

Fire resistance (minutes)

Column with load ratio of 0.5

Walll with load ratio of 0.35

Fire rating 120

Fire rating 180

Fire rating 240

Will structural elements become so stocky and massive?


Part 7. Fire protection material

Background:

• In case the underground structure needs to comply to FRP of 4-hour, it is challenging to design concrete structures economically to satisfy 4-hour fire rating.

• Typically, thickening of concrete cover and enlarging dimensions of members following Eurocode 2 will satisfy the 4-hour fire rating requirement.

• But it will result in exorbitant cost and massive dimensions which pose difficulties in underground construction.

34

Objectives: Optimizing resources in designing underground structures to comply 4-hour fire rating.

Targeting: Reducing size, weight of concrete members while still maintaining 4-hour fire resistance.

Method: Application of new materials.

– Coating method

• Spray-applied polyuria-based with halogen-free fire retardants.

• Concrete fibers as a coating.

– Adding fiber into concrete mix

• Adding fibers/ hybrid fibers/ nano-fibers in the concrete mix to increase fire resistance.


• Mineral fibre & binders

• Vermiculite & cement

• Advantages: – Fast application – Low cost – Easy to cover complex details – Often applied to non primed

steel – Some types may be used

externally

• Disadvantages: – Poor appearance

– Wet application on site

– Over-spray needs shielding

– Restricts other trades


Part 7a. Using Coating Materials

To satisfy the fire requirement using spray-applied polyuria-based with halogen-free fire retardants (SPBH).

Characterization of thermal properties of innovative coating materials.

Material model to describe the performance of SPBH based on (i) strain limits, (ii) surface temperature and (iii) thickness and composition of SPBH.

Fire tests on concrete cylinders and protected columns to provide database and numerical calibration.

Parametric study to propose design for fire protection materials.

Part 7b. Application of carbon-nanotube to enhance fire resistance

• To investigate the behaviour of ceUHPC under heat/fire:

– Impact of average length of CNT

– Impact of % of CNT in the water. While the overall percentage of CNT is limited by the dispersion quality, ratios of up to 0.66% have been tested. A higher percentage of CNT may further increase the insulation effect.

– Impact of compression strength on fire resistance. Typically a compression strength of 170 – 180 MPa is achieved without using specific curing techniques..

– Impact of curing technologies on the fire resistance of ceUHPC. Various curing technologies like steam-curing, warm-water curing and others and their potential impact impact on the fire resistance of the material will be evaluated.

Part 7c. Using fibres in concrete mix

This part is to study embedding suitable polymer-based and/or steel fibres into concretes to develop greater inherent fire resistance.

Method:

To investigate the failure mechanisms of reinforced concrete member at elevated temperature, including the evaluation of thermal properties.

This part will look into developing structural concrete with improved spalling, heat, and fire resistance through advanced materials technology such as the control of micro-porosity, inclusion of micro-/macro-fibers (single type or hybrid system) and/or the addition of fire retardants.

Deliverables:

Formulation of fire resistant structural concrete.

Evaluation of mechanical and fire performance of fire resistant structural concrete.

Constitutive model of fire resistant structural concrete under elevated temperature.

39

• Spalling of concrete in fire conditions is one of the major concerns for low porosity (low water-cement ratio) or dense concrete mix.

• Polypropylene and/or steel fibers can be added to concrete mix to mitigate the effects of fire-induced spalling and reduce the required concrete covers.

Targeting:

Four types of materials will be studied including:

– Steel fibre-reinforced concrete.

– Steel and PP fibre-reinforced concrete.

– ECC concrete.

Integrity of a fibers reinforced concrete column (250x250mm) after

two hours fire (ISO-834)

Rodrigues, J. P. C. et al.(2010) “Behaviour of fiber reinforced concrete columns in fire” Composite Structures, v 92, n 5, p 1263-1268, April 2010

Part 7c. Using fibres in concrete mix

Part 7d. Testing of structural members

This part of the project aims at to carry out fire resistance studies on concrete columns, beams and slabs to enhance fire resistance

Method:

State-of-the-art Review: to compile the previous work that has been conducted on fire induced spalling in concrete. Limitations in the current code provisions will be identified and steps to overcome these drawbacks will be suggested.

Full scaled fire tests: To develop test data on spalling resistance of concrete, large-scale fire experiments tests will be conducted on 4 concrete columns, 2 beams and 2 slabs.

Deliverables:

Recommendations for fibre and cement content, such as adding a certain amount of fibers or limiting the extent of silica fume.

The final report will also provide details of column, beam and slab design, test results, analyses and predictions.

41

Part 7e. Testing of structural members

This part provides fire resistance testing of columns, beams, walls and slabs to resist 4 hour fire rating under standard ISO834 fire curve.

Method:

Full scale test program consisting of 4 columns, 2 beams, 2 slabs, and 2 walls will be tested to ISO834 fire curve in an accredited laboratory that conforms to EC standard.

The suitable mix design for coating and fibres will be determined from Part 7(a) and Part 7(b) and structural tests from Part 7(c).

Deliverables:

A report will be drafted by the accredited laboratory for all the tests conducted.

Additional report will be drafted to link material test results from Part 7(a), 7(b) and 7(c) together with Part 7(d).

Summary

• This research provides an integrated fire safety assessment of underground developments in Singapore using a performance-based approach.

• The fire safety of Singapore underground development will be assessed holistically with SCDF.

Evacuation strategy

Structural fire safety

Fire detection

and suppression

Provide passive protection system

Provide active protection system

Provide life safety

43

Thank you for your kind attention.

44

Part 7c Asst Prof. YANG En-Hua CEE, NTU

Part 7a Asst Prof. Aravind Dassari MSE, NTU

Part 7a, 7b, 7c

Part 7d

Co

llab

ora

tors

Prof. TAN Kang Hai CEE, NTU

Lead Principal Investigator

Part 1 & 3 & 4 Structures and Evacuation Analysis

Prof. TAN Kang Hai CEE, NTU

Part 2 & 5 Fire detection Asst. Prof. WAN Man Pun MAE, NTU

Part 6 SUFM Mr. James Chua

Part 7d Prof. Venkatesh Kodur College of Engineering, Michigan State University

Part 7b MSEE Peter W. Weber ceEntek Pte Ltd

30%

10% 5

%

5%

5%

10%

10%

5%

5%

5%

30% % of time committed on the project

Part 7d Prof. Yao Yao Northwestern Polytechnic University, Xi’an, China

5%

Thank you

On-going structural fire tests

1. Testing of Composite beam-slab Systems at Elevated Temperatures

• Temperature rate: 50oC per minute

Tests of Composite beam-slab Systems

• Achievements

o Eight composite beam-slab floor systems tested

under fire conditions and validated with

numerical models. All specimens can

experience large deflection without global

collapse.

o Numerical model was able to predict accurately

the thermal/structural behaviour of composite

slab-beam systems subjected to fire conditions.

o Tensile membrane action was mobilized in all

specimens.

o Test results showed that it is possible to leave

interior secondary beams unprotected without

compromising safety of composite steel-frame

buildings under fire conditions. This results in

significant cost savings for building structures.

Completed structural fire tests

1. Structural responses of reinforced concrete columns subjected to uniaxial bending and restraint at elevated temperatures

Bulkhead

5000 kN Actuator

Pinned end

Test rig

Test rig

Test specimen

Pinned end Bulkhead


Columns subjected to uniaxial bending

• Achievements

Development of Thermal-induced restraint

forces at elevated temperatures:

o Restrained columns at elevated temperatures

are subjected to additional axial force

(thermal- induced restraint forces);

o Columns under higher load eccentricities

experienced higher normalised restraint

forces;

o Columns under lower initial load level had

higher normalised restraint forces;

o Normalised restraint forces were higher in

biaxial bending compared to uniaxial bending;

o FE analyses simulate similar trends but give

higher normalised restraint forces than test

results.

Columns subjected to uniaxial bending

• Achievements

Effects of uniaxial/biaxial bending, restraint

ratio, and concrete grade on restraint forces:

o Biaxially-loaded columns were more

susceptible to concrete spalling than those

under uniaxial bending;

o Columns subject to biaxial bending are

more susceptible to restraint forces than

uniaxial bending;

o For the same restraint ratio, normalised

restraint forces increase with concrete

grade;

o FE analyses simulate similar trends with

test results.

Effects of uniaxial and biaxial bending


2. Structural behaviour of CHS T-joints at elevated temperatures

11

00 m

m

L

d

t

D

T

= 2L/D

= d/D

= D/2T

Brace

ChordWeld

Crown

Weld toe

Saddle

M

Tenssion

part

Compression

part

= 2200 mm

• Temperature rate: ISO-834 (or 100oC per minute)

Tubular joints at elevated temp.

• Achievements

o Fourteen CHS T-joints were tested. The

joint strengths were significantly reduced

together with changes of failure modes.

o Material tests were carried out to quantify

fracture strains of heat affected zone. The

tests showed great reduction on ductility

of material when subjected to high

temperature.

o Parametric studies performed to find the

effect of temperature on major factors

controlling joint strength.

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16

0

10

20

30

40

50

(a)0.082 0.035 0.082

8.4

30.55

Yield (23.67)

In-p

lan

e b

end

ing

mo

men

t (k

Nm

)

Rotation (rad)

IB.T.069.20

IB.T.069.550

IB.T.069.700

Yura's deformation limit

(43.25)

Yield (30.88)

Yield (6.74)

0.00 0.02 0.04 0.06 0.08 0.10 0.12

0

10

20

30

40

(b)0.082

30.55

0.0690.056

35.88

In-p

lan

e b

end

ing

mo

men

t (k

Nm

)

Rotation (rad)

IB.T.069.550

IB.T.079.550

IB.T.047.55012.4


3. Composite steel top-and-seat-and-web angle joints at elevated temperatures


Composite TSW joints at elevated temp.

• Outcomes

o Composite steel TSW angle joints possess

significant rotational stiffness, high moment

resistances and large rotational capacities in

fire conditions.

o Increasing temperature will weaken the joint

strength and stiffness, and influence the failure

mode.

o Composite joints with larger beam sections will

generally possess higher rotational stiffness and

greater moment strength. Besides, the bolt

slips and shearing deformation will increase

the non-linearity of joint moment–rotation

behaviour.

o Mechanical models were developed and

validated. The models can be used in PB to

predict strength of joint at high temperatures.

Completed project: fire modelling

• Developed our own software – CFMFAN for compartment fire Modules:

• Ventilation flow

– Mass Flow In & Mass Flow Out through Window

• Heat release rate

• Heat transfer

– Radiative and Convective Heat

Transfer through Window

– Radiative and Convective Heat

Transfer from Wall

• Governing equations

– Mass Balance

– Energy Balance

– First Law of Thermodynamics

Compartment

wallQ

wallQ

wallQ

Window

HRR

ma

mu

wallQ

Tl

Tu

2-Zone model for ventilation flow

Completed project: fire modelling

• Achievements – Validation with OZone and CFAST.

Hot Gas Temperature

0

50

100

150

200

250

0 10 20 30 40 50Time, min.

Gas tem

pera

ture

, oC

NTU

CFAST

OZone

Interface Height Variation

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50Time, min.

Inte

wrf

ace H

eig

ht, m

.

Series1

CFAST

OZone

Model Wall HT Coeff. Gas Radiation Wall Radiation Heat

Flux Switch-over Fire stage

Comb. Outside

Comprt

CFM FAN Natural Convection Network Analysis

(12 Wall) Computed

Any of 3

Conditions 3 N

OZone Constant Ignored Ignored Gas Temperature/

Fire Area 3 Y

CFAST Natural Convection Computed Computed User-defined fire

duration 1 N

Completed-project: structural analysis

• Using SAFIR

SAFIR model of a column subjected to fire

Tan, Kang-Hai; Nguyen, Truong-Thang “Structural responses of reinforced concrete columns subjected to uniaxial bending and restraint at elevated temperatures” Fire Safety Journal, v 60, p 1-13, 2013

On-going project: structural analysis

• Outcomes

o A simplified assessment procedure

for fire resistance of RC columns.

o Consider the interactions between a

heated column with adjacent structural

member in a building frame through

axial restraints and thermal induced

forces.

o Analysis based on equivalent concrete

stress block and equivalent

temperature in reinforcing bars.

o Proposed method is compatible with

Eurocodes 2 specification, and reliable

for design purpose.

Failure modes of columns tested at elevated temp.

Model verification with a published test

Unprotected interior beam (USB)

Protected main beam (MB)

Protected secondary beam (PSB)

59

Reinforced Concrete Slab


• Using ABAQUS/Explicit to study Composite beam-slab Floor

Systems Exposed to ISO Fire

Nguyen, T. T. and Tan, K. H. (2011). "Numerical Investigations of Composite beam-slab Floor Systems Exposed to ISO Fire". Application of Structural Fire Engineering (ASFE). Prague, Czech Republic. 155-161.

Deformation contours of the slab system


• Outcomes:

o Proposed model consisted of material

and geometric nonlinearities, and large

deformations.

o Predict well the thermal/structural

behaviour of composite slab-beam

systems.

o Provide an efficient, economical and

yet accurate tool to study the membrane

behaviour of the composite slab-beam

systems under fire conditions.

-600

-500

-400

-300

-200

-100

0

0 50 100 150

Dis

pla

cem

ent

(mm

)

Time (min)

Test-Slab Slab Test-MB MB

Test-USB USB Test-PSB PSB

Local Fire Code

The fire safety of Singapore has two prescriptive fire codes:


–Fire Safety requirements for Mega Underground developments (2012).

Fire safety of Underground Caverns needs to follows these

codes. However, there are concerns in these aspects:

– Structural fire protection.

– Life Safety including:

• Evacuation;

• Application of Spatial Underground Fire Mitigation to help in the identification of fire source, evacuation, and rescue operations

Fire Safety Requirements

• Structural Fire Precautions

– The element of structure/compartment of each cavern unit shall have fire resistance rating of at least 4 hrs. [Clause 3.2 (c)]

• Vehicular Access

– Fire engine access road having minimum 4m width and overhead clearance of at least 4.5m for access by pump appliance shall be provided for fire-fighters and rescuers to conduct fire fighting and rescue operations. [Clause 3.3 (a)]

– Provision of alternative means of vehicle access into the underground development shall be considered on a case by case basis. [Clause 3.3 (b)]

Life Safety and Structural Fire Safety of Mega Underground Caverns in Singapore · 2014-10-10 ·...

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Transcript of Life Safety and Structural Fire Safety of Mega Underground Caverns in Singapore · 2014-10-10 ·...