Life Safety and Structural Fire Safety of Mega Underground Caverns in Singapore

Transcription

1 Life Safety and Structural Fire Safety of Mega Underground Caverns in Singapore Principal Investigator: Prof TAN Kang Hai Nanyang Technological University 1

2 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)

3 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.

4 Research Scope To support development of safe, robust and costeffective 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

5 Research Objectives This research provides an integrated fire safety assessment of underground developments in Singapore using a performance-based approach. Structural fire safety Provide passive protection system 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 Provide life safety Fire detection and suppression Provide active protection system 5

6 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 ii. protection system). 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. Research novelties 6

7 Part 1. Review International Fire Codes, propose & obtain agreed fire size and loads for cases applicable to USC & UWLF Methodology SCDF Accept? Yes No Engage SCDF SCDF, DSTA and JTC Michigan State Univ and Northwestern Poly. Univ., China Collaboration with SCDF, JTC and DSTA Part 2. Evaluate Pre-Flashover Fire Fighting Strategies, e.g. Very Early Detection, for all possible cases SCDF assessment on effectiveness Yes No 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? No No R&D for fire protection material Part 7a,b,c. Fire protection materials. Part 7d. Structural fire testing ISO Standard Fire Tests Yes Engage SCDF Part 7e. Fire protection on beams, columns, slabs and walls. Yes SCDF Accept? Prepare Report to provide scientific data for SCDF to update of Underground Fire Code End 7

8 Review interational Fire Codes. Evaluate Pre-Flashover Fire Fighting Strategies. Prof. TAN Kang Hai Role of team members Data from previous feasibility study (JTC) Base line estimation Structural fire Safety Input benefits from application of SUFM 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 Propose Performance Based Method to evaluate the requirement of Fire Safety of current design codes Assessments on Evacuation Prof. TAN Kang Hai PI with all Collaborators Manual/Automated Suppression system Prof. TAN K. H. Prof. Tan K. H. Asst. Prof. Wan M. P. Optimization process Prof. Tan K. H Asst. Prof. Yang E. H. Asst. Prof. Aravind B. D. Mr. Peter Webber Discussion with authorities about current design codes (SCDF, DSTA and JTC) Assessments on Smoke controls Prof. Tan K. H. Presentation and discussion with SCDF, DSTA and JTC Prepare Report to provide to SCDF to update of Underground Fire Code NTU faculty members: 4 Research staff members : 8 Government agencies: 3 Private company: 1 Duration: 4 years. Scientific data to the fire authorities to support the development of safe, robust and cost-effective regulatory requirements 8

9 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

10 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

11 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

12 Detailed explanations of the project 5/30/

13 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

14 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 fire safety code Singapore Underground Science City, conceptual design

15 Singapore fire safety code Objectives: Provide scientific data to the relevant authorities to support the development of safe, robust and cost-effective regulatory requirements.

16 Part 1. Review of first world codes The fire safety of Singapore has two prescriptive fire codes: Fire code (2007) 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

17 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)]

18 Part 1. Review of first world codes 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

19 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

20 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; Part 3. Post-flashover structural fire analysis 20

21 Part 3. Post-flashover structural fire analysis 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

22 Part 3. Post-flashover structural fire analysis 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

23 Structural stability in fire condition Time analysis: 1. Choose the worst fire scenario. 2. Evacuation analysis RSET. Part 4a. Assessment of Evacuation 3. Structural analysis fire resistance of the supporting structures. Requirement for occupant safety: RSET + Safety margin < ASET.

24 Our evacuation software - FeSim (by Prof. Yuan Weifeng) Part 4a. Assessment of Evacuation

25 Part 4a. Assessment of Evacuation 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

26 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.

27 Part 4b. Assessment of Engineered Smoke Control 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

28 Part 5. Manual and Automated Suppression System 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

29 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

30 Method: a) Convert data for the following networks so that they are GIS ready. i. Floor plans ii. iii. iv. Fire alarm System network Fire-Fighting apparatus network 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. Part 6. Application of SUFM 30

31 Part 7. Fire resistance to EC2 Part 1-2 Columns R x500 mm R x400 mm R x350 mm Based on standard section 300x300mm with 45mm cover for RE90 31

32 Part 7. Fire resistance to EC2 Part 1-2 Walls R mm R mm R mm Based on standard section 140mm with 10mm cover for RE90 32

33 Increase volumne of concrete Part 7. Fire resistance to EC2 Part 1-2 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. 200% Column with load ratio of % 160% Walll with load ratio of % 80% Fire rating 120 Fire rating % Fire rating % 40% 36% 50% 0% 21% Fire resistance (minutes) Will structural elements become so stocky and massive?

34 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

35 Part 7. Fire protection material 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 halogenfree 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.

36 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 7. Fire protection material

37 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.

38 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 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.

39 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

40 Part 7c. Using fibres in concrete mix Spalling of concrete in fire conditions is one of the major concerns for low porosity (low watercement ratio) or dense concrete mix. Polypropylene and/or steel fibers can be added to concrete mix to mitigate the effects of fireinduced 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 , April 2010

41 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

42 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).

43 Summary This research provides an integrated fire safety assessment of underground developments in Singapore using a performance-based approach. Structural fire safety Provide passive protection system The fire safety of Singapore underground development will be assessed holistically with SCDF. Evacuation strategy Fire detection and suppression Provide life safety Provide active protection system 43

44 Collaborators Thank you for your kind attention. 5 % 5 % 5 % Lead Principal Investigator Prof. TAN Kang Hai CEE, NTU 30 % Part 1 & 3 & 4 Structures and Evacuation Analysis Prof. TAN Kang Hai CEE, NTU 10 % Part 2 & 5 Fire detection Asst. Prof. WAN Man Pun MAE, NTU 5 % Part 6 SUFM Mr. James Chua Part 7a, 7b, 7c Part 7a Asst Prof. Aravind Dassari MSE, NTU Part 7b MSEE Peter W. Weber ceentek Pte Ltd Part 7c Asst Prof. YANG En-Hua CEE, NTU 10 % 5 % 10 % Part 7d 5 % Part 7d Prof. Venkatesh Kodur College of Engineering, Michigan State University 5 % Part 7d Prof. Yao Yao Northwestern Polytechnic University, Xi an, China 30 % % of time committed on the project 44

45 Thank you

46 On-going structural fire tests 1. Testing of Composite beam-slab Systems at Elevated Temperatures Temperature rate: 50 o C per minute

47 Tests of Composite beam-slab Systems Achievements o o o 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. Numerical model was able to predict accurately the thermal/structural behaviour of composite slab-beam systems subjected to fire conditions. Tensile membrane action was mobilized in all specimens. 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.

48 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 Temperature rate: 50 o C per minute

49 Columns subjected to uniaxial bending Achievements Development of Thermal-induced restraint forces at elevated temperatures: o o o o o Restrained columns at elevated temperatures are subjected to additional axial force (thermal- induced restraint forces); Columns under higher load eccentricities experienced higher normalised restraint forces; Columns under lower initial load level had higher normalised restraint forces; Normalised restraint forces were higher in biaxial bending compared to uniaxial bending; FE analyses simulate similar trends but give higher normalised restraint forces than test results.

50 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 o o Columns subject to biaxial bending are more susceptible to restraint forces than uniaxial bending; For the same restraint ratio, normalised restraint forces increase with concrete grade; FE analyses simulate similar trends with test results. Effects of uniaxial and biaxial bending

51 1100 mm Completed structural fire tests 2. Structural behaviour of CHS T-joints at elevated temperatures Temperature rate: ISO-834 (or 100 o C per minute) M Chord Brace d t Weld = 2L/D = d/d T = D/2T Saddle Crown Weld toe Tenssion part Compression part L = 2200 mm D

52 In-plane bending moment (knm) In-plane bending moment (knm) Tubular joints at elevated temp. Achievements 50 o o o Fourteen CHS T-joints were tested. The joint strengths were significantly reduced together with changes of failure modes. 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. Parametric studies performed to find the effect of temperature on major factors controlling joint strength Yield (30.88) Yield (23.67) Yura's deformation limit (43.25) Yield (6.74) (a) Rotation (rad) IB.T IB.T IB.T IB.T IB.T IB.T (b) Rotation (rad)

53 Completed structural fire tests 3. Composite steel top-and-seat-and-web angle joints at elevated temperatures Temperature rate: 36 o C per minute

54 Composite TSW joints at elevated temp. Outcomes o o o Composite steel TSW angle joints possess significant rotational stiffness, high moment resistances and large rotational capacities in fire conditions. Increasing temperature will weaken the joint strength and stiffness, and influence the failure mode. 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.

55 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 Q wall Compartment Q wall Q wall Window HRR m u m a Q wall 2-Zone model for ventilation flow T u T l

56 Gas temperature, oc Intewrface Height, m. Achievements Validation with OZone and CFAST. Completed project: fire modelling Model Wall HT Coeff. Gas Radiation CFM FAN Natural Convection Network Analysis (12 Wall) Wall Radiation Heat Flux Computed OZone Constant Ignored Ignored CFAST Natural Convection Computed Computed Switch-over Any of 3 Conditions Gas Temperature/ Fire Area User-defined fire duration Fire stage Comb. Outside Comprt 3 N 3 Y 1 N Hot Gas Temperature Interface Height Variation NTU CFAST OZone Series1 CFAST OZone Time, min Time, min

57 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

58 On-going project: structural analysis Outcomes o o o o A simplified assessment procedure for fire resistance of RC columns. Consider the interactions between a heated column with adjacent structural member in a building frame through axial restraints and thermal induced forces. Analysis based on equivalent concrete stress block and equivalent temperature in reinforcing bars. Proposed method is compatible with Eurocodes 2 specification, and reliable for design purpose. Failure modes of columns tested at elevated temp.

59 59 On-going project: structural analysis Using ABAQUS/Explicit to study Composite beam-slab Floor Systems Exposed to ISO Fire Reinforced Concrete Slab Protected secondary beam (PSB) Protected main beam (MB) Unprotected interior beam (USB) Model verification with a published test Deformation contours of the slab system 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

60 Displacement (mm) On-going project: structural analysis 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 Time (min) Test-Slab Slab Test-MB MB Test-USB USB Test-PSB PSB

61 Local Fire Code The fire safety of Singapore has two prescriptive fire codes: Fire code (2007) 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

62 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)]

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