Case Study 1 Underground Car Park Dorota Brzezińska 1, Janusz Paliszek 2, Piotr Smardz 2, Renata Ollesz 1, Karol Kaczor 2 1 Lodz University of Technology, GRID - Lodz, 2 INBEPO Wroclaw, Poland
Building Description A two storey enclosed underground car park 13 000 sqm of net area Height 2.9 m from the floor to the ceiling The ceiling structure is of a flat smooth surface Car stackers only at level -2 (magenta hatch)
Polish Requirements for Enclosed CP Maximum travel distance up to 40 m (regardless if single or alternative), extended to 60 and/or 80 m if smoke control / sprinkler protection provided and counted for MoE At least two exits required if car park area exceeds 1 500 sqm No special requirements for MoE for disabled occupants Maximum allowed compartment size up to 5 000 sqm (doubled if fire suppression provided) Fire resistance of structural elements typically R 120, REI 120 floors, compartment walls REI 120 (EI 60 doors) The minimum clear height to the underside of structural elements 2.2 m Smoke control system required if car park area exceeds 1 500 sqm Large car parks also require automatic FDAS, fire hose reels and emergency escape lighting Any deviations from the National Regulations require special exemption approval by the Ministry of Infrastructure
Requirements for Smoke Ventilation in Car Parks Maintain tenable conditions for occupants for required safety escape time (i.e. REST) Acceptance criteria (adopted typical values - not directly indicated in the regulations): temperature not exceeding 60 o C, minimum visibility of light-reflecting signs not less than 10 m (both measured at 1.8 m above FFL) Should have a reliable inlet of fresh replacement air The main smoke extract fans should be temperature class F 400 120 if the predicted smoke temperature is less than 400 o C, otherwise F 600 60 Lower temperature ratings allowed if safe conditions for fire brigade operations can be demonstrated however, these are not defined in the Polish regulations Both traditional (ducted) and jet-fan systems allowed, with the later currently more often used
Examples of Designs Complying with Polish National Requirements Unsprinklered car park Maximum travel distance up to 40 m or 60 m if the smoke control system allows for extended TD by 50% Sprinkler protected car park Maximum travel distance up to 40 m or 80 m if the smoke control system and use of the fire suppression system allow for extended TD by sum of two 50% allowances Maximum fire compartment size up to 5 000 sqm (approximately four fire compartments at each level) Higher main extract fans capacities and temperature rating predicted Maximum fire compartment size up to 10 000 sqm (approximately two fire compartments at each level) Lower main extract fans capacities and temperature rating predicted
Main Design Assumptions for Analysis Designs not fully complying with National Requirements (i.e. fire compartmentetion) Both levels considered as separate fire compartments Unsprinklered and sprinklered design solutions considered, two different proposals are provided for each Similar solutions and FS measures provided for both scenarios Design study based on level -2 as more demanding (stackers) A ductless jet fan ventilation system is proposed Simple solutions prefered rather than more complex More flexible approach for sprinkler protected cases
Optional Solutions Considered in the Case Study Four different solutions were considered for the case study purpose: CASE 1A. Unsprinklered. Each storey not divided into fire zones. CASE 2A. Unsprinklered. Each storey additionally divided into fire zones. CASE 1B. CASE 2B. Sprinklered. Each storey not divided into fire zones. Sprinklered. Each storey additionally divided into smoke compartments.
Fire Safety Measures and Design Approach Fire safety measures and systems Unsprinklered car park Sprinklered car park Sprinkler system No Fast response system to meet life safety requirements RTI < 80 T= 68 o C OH2 design group (minimum) Passive fire protection measures (i.e. fire/smoke compartmentation subdivision) No (1A) / Yes (2A) No (1B) / Yes (2B) Passive or active smoke barriers smoke curtains, walls separating car park stacker platforms are provided (every three spaces) Provided (no compartmentation subdivision) - walls separating car park stacker platforms are provided (every three spaces) Voice alarm system Yes Yes (option) Two stage automatic fire and smoke detection Yes Yes system Way finding and active evacuation signage (for subdivision) Yes Yes (option) Smoke control system for evacuation purpose (for Yes Yes subdivision) Fire management level of a higher standard of a higher standard Fire compartmentation between floor levels between floor levels Fire brigade access point at the ground floor entrance hall at the ground floor entrance hall
Detailed Design Analysis Short Summary Means of Escape Location Basement Car park Area (m 2 ) 13 200 Usage Storage Occupant Load Factor (m 2 /Person) 30 Estimated Peak Occupant Level (Persons) 440 Number of final storey exits in accordance to case study project 6 Calculated minimum single exit width (m) 0.73 Proposed minimum single exit size (m) 0.9 Type Recommended Limits (m) Maximum Proposed (m) Dead End Alternative Dead End Alternative Basic 40 60 62 Extended (vent. + sprinkl.) (up to 80)
Detailed Design Assumptions Schematic layout of the subdivision into fire/smoke ctrl. zones Typical subdivision for all options considered in this case study for comparison purpose Three fire or smoke compartmens Seven smoke control zones (2+3+2)
Detailed Design Analysis Design Fire Sizes and Fire Curves a) Sprinklered fire of one burning car 4MW (case 1B/2B) b) Sprinklered fire of two car stacker platform 6MW (case 1B/2B) c) Unsprinklered fire of two burning cars 8MW (case 1A/2A) d) Unsprinklered fire of three/four burning cars in stacker platform 12/15MW (case 1A/2A)
Detailed Design Analysis - Assumptions Clear height of the both car park storeys (from FFL to the ceiling) is 2.9 m; The smoke curtains with the bottom edge at height 2.2 m are placed below the ceiling slab; Smoke extraction is provided through mechanical ventilation inlet and exhaust points NW ( NW1, NW2, NW3, NW4, NW5, NW6, NW7 ) Air supply is provided through mechanical ventilation inlet and exhaust points NW ( NW1, NW2, NW3, NW4, NW5, NW6, NW7 ) and four natural air inlets points N of the effective area (net area) 5 m 2 each, located at the floor level of the car park on each storey; Maximum air flow rate through the ventilation points (net cross-section) was assumed at: 10 m/s for exhaust points, not more than 5 m/s for mechanical inlet points and 2.5 m/s for natural air inlet points;
Detailed Design Analysis - Assumptions The extract points activated immediately after the fire is detected (by two smoke detectors - two stage alarm system) in the same smoke detection zone or one smoke detector and brake glass unit; Full operation capacity achieved within not more than 140 seconds from the start of the fire (i.e. after about 60 seconds from the detection of the fire); The analyzed jet fans are: unidirectional fans with capacity at low speed 0.91 m 3 /s and full speed 1.79 m 3 /s and reversible jet fans with capacity at low speed 0.82 m 3 /s and full speed 1.6 m 3 /s Temperature rating 400 0 C/2h for unsprinklered, lower for sprinklered (i.e. 300 0 C); in case of a jet fan located directly above the fire, it was assumed as non-operating since it may be damaged by the fire at the early stage; Height of the bottom of the jet fans from the floor is no less than 2.1 m; During operation of the system in the smoke ventilation mode the fans operate on at full speed. It was assumed that the jet fans shall be activated after 300 seconds from the start of the fire (i.e. after about 220 seconds from the detection of the fire);
Detailed Design Analysis CFD Software Used The simulations were performed by means of Fire Dynamics Simulator (FDS), software developed by the National Institute of Standards and Technology U.S. Department of Commerce. Three versions of the software have been used for the purpose of this analysis, including ver. 4.0.7; 5.5.3 and 6.3.2 of FDS, which required high computer power to be involved. The older versions were used mostly for preliminary design studies. For later stage of the works two versions (ver. 553 and 632) for sprinklered scenarios were used simultaneously and their results were directly compared. FDS 632 results are provided. Sprinkler heads based on the proposed sprinkler system parameters are physically modelled in both FDS 553 and 632 versions input files.
Detailed Design Analysis CFD Simulation Main Parameters Extract points Ambient (initial) temperature 20 o C Soot yield was 0.091 / 0.1, Heat of combustion = 36904 kj/kg. The computational domain was represented by the multiple meshes build up of rectilinear cells Mesh resolution 0.30 m in all x, y, z directions. The model size was 1.9 mln cells The minimum run time is 900 s 50% car spaces filled with cars Inlet points
Detailed Design Analysis CFD Simulation Main Parameters Two-stage FDAS assumed as activated even before 80 s form the start of the fire (for the given fire type and object height 60 s would be resonable) 20 m Expansion range of smoke after 80 seconds from the start of the fire according to CFD detailed analysis. Smoke control system activated after 90 s from the start of fire
Aim of the study: Detailed Design Analysis Analysed Simulation Parameters Determine the tenability conditions during fire within the time required for safe evacuation for the proposed smoke control system. According to the literature data the threshold values of each analysed parameter are as follows: life hazard temperature 60 o C, however the boundary temperature on the evacuation routes obtained from the simulation is assumed at lower level of 52 o C), visibility range 10 m for structural elements, which is equal to 30 m visibility of illuminated signs Simplyfied check for fire-fighters access conditions (after 15 min) - 100 o C at 1,5 m above FFL within 10 m Limit the smoke spread within the car park to the smoke zone where fire occured - ideally
CASE 1A. Unsprinklered, without Compartmentation Each level is divided into seven smoke detection zones SZ: SZ1 SZ7 No fire compartmentation within each level Smoke barriers along the smoke control boundaries (not full height)
CASE 1A. Unsprinklered, without Compartmentation
CASE 2A. Unsprinklered, with Compartmentation Each level is divided into seven smoke detection zones SZ: SZ1 SZ7 Fire compartmentation at each level 3 fire compartments/zones Full smoke and fire separation provided between fire zones/compartments
CASE 2A. Unsprinklered, with compartmentation
CASE 1B. Sprinklered, without Compartmentation Each level is divided into seven smoke detection zones SZ: SZ1 SZ7 No fire compartmentation within each level Smoke curtains/barriers provided along smoke control zones (full height) and 2,2 m above drive ways
CASE 1B. Sprinklered, without Compartmentation
CASE 2B. Sprinklered, with Fire/Smoke Compartmentation Each level is divided into seven smoke detection zones SZ: SZ1 SZ7 Fire or smoke compartmentation at each level 3 fire/smoke compartments Active or passive smoke curtains/barriers to be used (more flexible approach)
CASE 2B. Sprinklered, with Compartmentation
Simulations Results HRR Plots Unsprinklered HRR curve Sprinklered HRR curve Example of fires (sprinklered) 4 MW Case 1A. Fire growth rate for two burning cars total HRR of 8 MW. Case 1B. Fire curve for one burning car with sprinkler protection total HRR of 4 MW. 6 MW (stacker) Case 2A. Fire growth rate for four burning cars total HRR of 12 MW. Case 2B. Fire curve for two car stacker with sprinklers protection total HRR of 6 MW.
Results of the Simulation A2 Fire in Smoke Detection Zone SZ2 A2
Results of the Simulation A2 Fire in Smoke Detection Zone SZ2 A2
Results of the Simulation A2 Unsprinklered - SZ2 A2
Results of the Simulation A2 Unsprinklered - SZ2 A2
Results of the Simulation A3 Fire in Smoke Detection Zone SZ3 A3
Results of the Simulation A3 Fire in Smoke Detection Zone SZ3 A3
Results of the Simulation A5 Fire in Smoke Detection Zone SZ5 A5
Results of the Simulation A5 Fire in Smoke Detection Zone SZ5 A5
Results of the Simulation-Case 1B (Sprinklered)
Results of the Simulation-Case 1B (Sprinklered)
Results of the Simulation-Case 2B (Sprinklered)
Results of the Simulation-Case 2B (Sprinklered)
Results of the Simulation-Case 2B (Sprinklered)
Results of the Simulation-Case 2B (Sprinklered)
Summarised Comparison of Considered Cases Case Sprinklers Fire / smoke compartmentation Volume flow of smoke exhaust system [m 3 /h] 1A No No 140 000-480 000 1B Yes No 140 000-180 000* 2A No Yes (fire) 160 000-320 000 2B Yes Yes (smoke) 90 000 * for 1B (smoke zone SZ6) it would be advisable to increase the extract volume capacity by 15-20% to 210/240 000 m 3 /h
Sprinklers in the CFD Model Sprinklers heads were modelled (1B and 2B cases). In the course of the simulations it was noted that 24 sprinklers heads were activated for stacker fire scenario (less for others). It suggests that OH2 could not be sufficient for car park fire scenarios. 18 heads active 24 heads active Both, ceiling jet and ventilation influence were observed as the majnor contributors for the sprinklers activation. No jet fans influence in large extence was observed in terms of sprinklers activation.
FDS Results Comparison Extract Rates Different extract volumes were checked for all smoke zones. 180 000 m 3 /h 240 000 m 3 /h 180 000 m 3 /h 240 000 m 3 /h Direct comparison of 180 000 m 3 /h vs 240 000 m 3 /h (FDS 6).
FDS Comparison - Results Different versions of the software were used. Sprinklered scenario 1B, 240 000 m 3 /h 810s (time) Identical input parameters Direct comparison of FDS 6.3.2 and 5.5.3 versions.
Conclusion and Summary 1 The analysis of the temperature and visibility distribution at the height of 1.8 m above FFL shown that in the analyzed fire scenarios the threshold values of temperature 60 o C (50 o C from simulation) and visibility below 10 m on evacuation routes and near the evacuation exits are not exceeded within the required time for evacuation (RSET= 300s) in large extent. For fully developed design fire in cases without sprinklers and compartmentation the smoke propagation exceeded the smoke control zone where fire occurs, so for the unsprinklered scenarios, it is advised that the car park area should be fire compartmented (internally subdivided). Conditions for fire-fighters intervention in case of temperature range below threshold of 100 o C measured at 1.5 m at 900 s simulation time in all shown sprinklered cases and the unsprinklered cases with compartmentation allow for access within 10 m to the bed of fire It is noted that the longest dead end travel distance is at the very low bottom right corner (60 m). Although it complies with the national fire requirements and regulations, it would be advised to reduce the travel distance by moving the staircase to the far end (cul de sac) or to reverse the staircase so that the travel distance is shortened or no dead end is present.
Conclusion and Summary 2 For sprinklered scenarios much lower smoke extract capacities are required. Also lower temperature rating for exhaust fans is possible. For the unsprinklered scenario, provision of the walls separating the stacker platforms provided good result in terms of protection against uncontrolled fire growth and high temperature range at fully developed fire. In both cases (2A unsprinklered and 2B sprinklered) best results were achieved for rather high degree of separation dividing the car park into separated zones/compartments. Also much lower extraction volumes were sufficient in those cases. However it is noted that in this case a direct visual contact of the occupants present at the car park with the fire or exits will be limited. This can result with necessity of use an active evacuation signage system so that no occupants would evacuate through the smoke/fire zone where fire occurred. Nevertheless it brings a higher degree of safety, as in both cases, smoke propagation is limited mostly to the smoke control zone where the fire occurred.