Case Study 2 (Production and Storage Buildings) - Spain OBJECTIVE Developed by the SFPE Spanish Chapter Editor: Jimmy Jönsson, JVVA Fire & Risk The objective of this case study is to show how a project of this type would have been dealt with in Spain. The case study will clearly show where a performance based approach would have been necessary and for each specific case it will show the general concept to be used. It will also show one of these approaches with greater detail (a detailed analysis will be performed). INTRODUCTION In Spain there is a national code specifically developed for Industrial buildings, RD 2267/2004 [1], that code (prescriptive method) should be used as a first approach to determine to what extent the requirements outlined in this document can be incorporated i.e. for what areas can a code approach not be used. If the code approach require onerous design solutions with no or very low viability of incorporation or simply does not allow for a certain activity due to specific building characteristics it is then necessary to use a Performance Based Design approach (PBD). GENERAL METHODOLOGY The methodology to be used can be summarized with the following points: 1. Prescriptive Analysis The first step is to perform a prescriptive analysis to determine the design requirements for the building and the foreseen activity. 2. Identify areas of non-compliance Based on the result of the prescriptive analysis it is possible to determine where special solutions are required i.e. where it is not possible to incorporate a solution required by the code. 3. Performance based approach Once the areas of non-compliance are known it is essential to develop a performance based approach for each one. It is necessary to follow a basic PBD approach [2]; show the overall objectives of the analysis, the analysis methods to be used, the acceptance criteria to be used, etc.
4. Detailed Analysis Once the different PBD packages have been developed it is possible to start with the detailed analysis. It is considered very important to mention that any type of PBD approach need/should to be discussed and agreed in detail with the Authority Having Jurisdiction (AHJ) before any detailed analysis is started. Not doing so can result in non-acceptance of the PBD analysis once presented to AHJ. BUILDING DESCPRITION The building used for the analysis is one large building divided into three equal sub-volumes, these volumes are being separated from each other by a compartmentation wall. The building has a floor plate area of 180m x 100m and a height of 12m. For design a purposes a normal roof (not lightweight is considered in this analysis). There are three different types of activities, each one located in its own sub-volume: Activity 1 Storage High bay storage (document archives) with 2 levels of catwalks (4m and 8m). Activity 2 Storage High bay storage (car parts warehouse) with man-up system. Activity 3 Production + Storage Production of furniture. Two storage areas (ready products + raw material). The following image shows the concept. Figure 1 Building
PRESCRIPTIVE ANALYSIS The code approach is quite straightforward, the analysis process is well described in the document and for fire engineers familiar with Industrial buildings and how to use of the national code this analysis should be quite easy to perform. Analysis Process The prescriptive analysis process to be used can be described with the following points: 1. Determine building type The first step is to identify the type of building. The code has developed five (5) different types of building (Type A, B, C, D and E) and the building for which the analysis is performed must belong to one of these types. 2. Perform risk level analysis Once the building type has been determined the next step is to perform a risk level analysis. This analysis is based on the activity (production or/and storage) and the type of products to be used (fire load). This analysis will results in a risk value (Low, Medium or High) for the activity. 3. Determine design requirements When the risk level has been calculated it is possible to determine the specific design requirements needed, these requirements depend on two factors, the building type and the risk level (risk value). It might even be that the type of activity foreseen is not possible with a prescriptive code approach. Step 1 Determine Building Type The first step in the prescriptive analysis is to determine the building type. In our case it fits very well with the definition of building Type A. Type A: Building which is sub-divided into different compartments, each one of the compartments contains an industrial process (storage and/or production) or a use which is different from industrial (for example office use). Conclusion: The building is of Type A and it contains three different industrial activities. Step 2 Perform Risk Level Analysis (determine risk value) The second step in the prescriptive analysis is to calculate the risk value for each one of the activities. There are two main formulas to be used, one for production activities and one for storage activities, there is no major difference between them and only one has been shown below. The following formula is used to determine the risk value for each storage activity.
Where: : Fire load value within sector (Mcal/m 2 ), used to determine risk level : Danger coefficient related to combustibility (dimensionless) : Surface area of sector (m 2 ) : Danger coefficient related to ignition (dimensionless) : Height of storage material (m) : Surface area of storage material (m) : Fire load value for storage material (Mcal /m 3 ) Formula 1 Risk Level The detailed calculations of the risk level can be found in appendix A. The overall results for each activity is shown below. Results: Activity 1 Storage: Risk value = 3062 Mcal/m 2, High Risk (level 8) Activity 2 Storage: Risk value = 1078 Mcal/m 2, High Risk (level 6) Activity 3 Production + Storage: Risk value = 180 Mcal/m 2, Low Risk (level 2) Step 3 Determine design requirements The last step in the prescriptive analysis is to see what implications the risk level has on the building design. Once the risk level and the building type is know it is possible to determine the design requirements. The following sections shows the main code requirements for each one of the three activities. Activity 1 Storage: This industrial activity is not permitted in a Type A building. A code approach would require this activity to be situated in a standalone building (Type C) and the sole use of the building must be related with this specific activity.
A performance based approach would need to identify (interpretation of the code + negotiation with authorities) the necessary requirements to consider this sub-volume to be equally safe as if the activity would have been in a Type C building. These necessary requirements would be: Structural independence (i.e. a fire cannot affect the structure of an adjacent compartment). Fire cannot spread beyond compartmentation limits (i.e. cannot affect another compartments or an adjacent building). On top of that the following general design requirements would apply: Structural capacity (any loadbearing element): R90 Compartmentation (any element): EI90 Structural capacity (loadbearing element separating another activity): R240 Compartmentation (element separating another activity): EI240 Emergency exits: 2 independent exits Travel distance: maximum of 25m (+ 25% if the building is sprinklered) Smoke control system: Yes Detection system: Yes Alarm system: Yes Signage & Emergency lighting: Yes Sprinklers & Hose reels: Yes Activity 2 Storage: This industrial activity is not permitted in a Type A building. A code approach would require this activity to be situated in a standalone building (Type C) and the sole use of the building must be related with this specific activity. A performance based approach would need to identify (interpretation of the code + negotiation with authorities) the necessary requirements to consider this sub-volume to be equally safe as if the activity would have been in a Type C building. These necessary requirements would be:
Structural independence (i.e. a fire cannot affect the structure of an adjacent compartment). Fire cannot spread beyond compartmentation limits (i.e. cannot affect another compartments or an adjacent building). On top of that the following general design requirements would apply: Structural capacity (any loadbearing element): R90 Compartmentation (any element): EI90 Structural capacity (loadbearing element separating another activity): R240 Compartmentation (element separating another activity): EI240 Emergency exits: 2 independent exits Travel distance: maximum of 25m (+ 25% if the building is sprinklered) Smoke control system: Yes Detection system: Yes Alarm system: Yes Signage & Emergency lighting: Yes Sprinklers & Hose reels: Yes Activity 3 Production + Storage: This industrial activity is permitted in a Type A building. The following general design requirements would apply: Sector size: Maximum 1000 m 2 Structural capacity (any loadbearing element): R90 Compartmentation (any element): EI90 Structural capacity (loadbearing element separating another activity): R120 Compartmentation (element separating another activity): EI120
Emergency exits: 2 independent exits Travel distance: maximum of 50m (+ 25% if the building is sprinklered) Smoke control system: No Detection system: Yes Alarm system: Yes Signage & Emergency lighting: Yes Sprinklers: No Hose reels: Yes Conclusion The prescriptive analysis shows that activity 1 and activity 2 are not permitted in this type of building, activity 3 is permitted but would need to have sub-compartments (not a viable solution) to comply with an prescriptive approach. To be able to incorporate these three activities in this type of building (Type A) it is necessary to apply a performance based approach.
PERFORMANCE BASED APPROACH A PBD approach is necessary to be able to maintain these three activities in one single building. The typical PBD methodology would be used, this methodology is described generally in the following section. Methodology A detailed analysis would be based on a well-known and internationally accepted methodology, SFPE methodology [2] for performance based design projects. The general PBD process is described in more detail in the following section. Process The detailed analysis would follow the general steps outlined below (it is described for the detailed analysis to be performed as part of this case study, smoke movement analysis): 1. Identification of fire scenarios The first step of the analysis is to identify the fire scenarios that will be used for the detailed analysis. It is necessary to understand the use of the different areas (fire load characteristics) to be able to develop the fire scenarios. 2. Development of design fires Once the fire scenarios have been identified is it necessary to develop a design fire that is to be used in the analysis; growth rate, maximum fire size and duration. 3. Development of acceptance criteria It is necessary to develop acceptance criteria. For a smoke control analysis these would normally be smoke layer height, smoke temperature and visibility. 4. Smoke movement analysis In this step the detailed smoke calculations are performed i.e. the smoke ventilation design parameters are determined. 5. Results and conclusions The final results and conclusions are presented in form of a technical report. PBD Analysis Three main PBD analyses would need to be performed, these are described below. These would be applicable to the entire building i.e. all three activity zones. PBD 1 Structural Independence It would be necessary to show that a fire in one sector (Activity zone) would not affect the structural capacity in another sector. The normal PBD process would be used [2].
This would require an advanced structural analysis. This analysis would determine the effect the established fire scenarios would have on the structure. The overall objective would be to prevent failure (collapse) of the structure within the fire zone and indirectly the collapse of the structural elements in any adjacent zone. The typical performance criteria would be a critical temperature for structure or more adequate a critical behavior of the structure. This article does not continue with the detailed analysis of the structure as this would actually require a detailed description the structure (type of elements, connections, etc.). PBD 2 Fire Spread It would also be necessary to show that a fire in one sector (Activity zone) would not spread to another sector or to another building. The normal PBD process would be used [2]. This would require an advanced heat transfer analysis. This analysis would determine the risk of fire spread, for the established fire scenarios, to adjacent sectors and buildings. The overall objective would be to prevent fire spread to other sectors (by conduction) and to other buildings (by radiation). The typical performance criteria for spread to another sector would a critical temperature on the other side of a compartmentation wall and the performance criteria from fire spread to an adjacent building would be a critical radiation level received by the other building. This article does not continue with the detailed heat transfer analysis as this would actually require a detailed description the compartmentation walls (type of elements, materials, etc.) and the separation distances to other buildings. PBD 3 Smoke Movement An important part of the PBD analysis would be to show that tenable conditions are maintained during an evacuation and during the firefighting intervention. The travel distances are not met for Activity 1 and Activity 2, and all three activities need large open volumes for operation (a code approach would require sector limits and smoke reservoirs). This would require an advanced smoke movement analysis. This analysis would determine if tenable conditions can be maintained, for the established fire scenarios, during the evacuation of the building but also during fire fighter intervention. The overall objective would be to maintain tenable conditions (temperature and visibility) within the activity zone during evacuation and firefighting intervention. The typical performance criteria would be temperature of the smoke and visibility within the activity zone. This article describes a detailed smoke movement for the most demanding sector (Activity zone 1).
PBD 3 SMOKE MOVEMENT ANALYSIS A detailed smoke movement analysis will be performed for the building. It is necessary to show the life safety level are no worse for the activity zones even if the travel distances are slightly longer than those required by the code and the each activity zone is one large volume. It should also be mentioned that a strict code approach for the smoke movement analysis would require the volume to be subdivided into several smoke reservoirs, something normally not viable for high bay storage (not compatible with operation) and a PBD approach would also optimize the smoke control design. The following sections shows the overall analysis, a more detailed description of the analysis can be found in Appendix B & C. Analysis Process - Assumptions The following sections shows the main assumptions for the analysis. Building zone The analysis is performed for Activity zone 1, this activity could have people working at high level (8m above floor level) within the single volume. This will require a higher performance of the smoke control system when compared to the other zones, where persons are working at floor level. Objective of the analysis The objective of the analysis is to show that tenable conditions can be maintained in the activity zone during the evacuation of the building but also during firefighting intervention. Fire scenarios There are two fire scenarios developed for the analysis. 1. Fire within the high bay storage 2. Fire at floor level within the activity zone The high bay storage is equipped with in rack sprinklers and the entire activity zone is equipped with sprinklers, so both fire scenarios are sprinkler controlled. A fire controlled by the in rack sprinklers will be of a much smaller size than a fire controlled by the roof sprinklers. The smoke production rate is also higher for the fire controlled by the roof sprinklers, and this fire scenario will be evaluated in more detail. Design fire For the roof sprinklers a mesh of 3m x 3m with standard response sprinklers has been assumed. This gives a fire size of approximately 6.0 MW (safety factor of 1.5). The design fire curve used in the calculations have the following characteristics:
Growth 0.047 (kw/s 2 ), Fast Maximum size 6.0 MW Duration continued at maximum size Decay not included Acceptance criteria Two types of acceptance criteria have been used; temperature and visibility. These values are based on the guidance presented in PD 7974:6 [3]. The document recommends the use of 10m visibility in large enclosures. The document also states that thermal burns to the respiratory tract can occur upon inhalation of air above only 100 C when dry conditions or 60ºC in humid conditions (i.e. presence of sprinklers). The tenability criteria will be examined at 2.0m above head height of the occupants (2m above the catwalk level) i.e. 10m above floor level. Temperature: 60 deg ºC (sprinkler controlled fire) Visibility: 10 m Smoke Movement Analysis This section describes the analysis performed for Activity zone 1. Fire & Smoke Modelling Smoke movement calculations have traditionally been undertaken using empirical formulae which assume a steady state fire at a given heat release rate, producing a constant quantity of smoke. However, those formulae (that are based on zone models) are weak if applied to large enclosures and when used to calculate the mixing between hot and cold layer may be not accurate. Zone models are indeed limited by their use of two horizontal layers without any temperature variation within a zone. Computational Fluid Dynamics (CFD) has been used to analyze the smoke movement as this method assesses the transient movement of smoke in the space and takes account of complex flow patterns and geometries. Ventilation System A mechanical ventilation system has been foreseen for the area. The inlet air will come directly from outside via automatically opening vents (the loading bays). It has been assumed that four (4) openings can be provided, two from one side and two from the opposite side, each one with an area of approximately 16.0 m² (4.0m x 4.0m), a total of 64.0 m².
The smoke will be extracted locally at high level. Ten (10) extract fans have been provided, each one with a capacity of 12 m 3 /s, a total of 120 m 3 /s. Results The results show that the acceptance criteria are met during the evacuation of the building and also during a possible firefighting intervention. The following sections shows the results, visibility and temperature, from the analysis. Visibility Visibility is an accurate instrument to quantify the thickness of the smoke layer (indirectly the smoke layer height), as it is directly related with the density of particles contained in this layer. The following images shows the visibility slice files (cut at 10m) within the space. Figure 2 Slice visibility, 240s
Figure 3 Slice visibility, 240s Figure 4 Slice visibility, 300s
Figure 5 Slice visibility, 300s Figure 6 Slice visibility, steady state (600s)
Figure 7 Slice visibility, Steady state (600s) Temperature The following images show temperature slice files (cut 100ºC) within the space. Figure 8 Slice temperature, 300s
Figure 9 Slice temperature, 300s Figure 10 Slice temperature, Steady state (600s)
Figure 11 Slice temperature, Steady state (600s) Conclusion The smoke movement analysis has shown that tenable conditions can be maintained during the evacuation and firefighting intervention (steady state conditions are achieved). The small increase in evacuation distances does not affect the safety level of the occupants and having one large compartment does not have any negative effect upon evacuation. It would be necessary to show an more detailed evacuation analysis i.e. that the catwalk levels should be able to evacuate within 300 s (when tenable conditions at this level no longer can be maintained), this should not be an issue if additional measures such as an aspirating detection system and a voice alarm system is introduced. Conditions for firefighting is kept good all the time (steady state), the smoke layer is maintained at a high level and conditions for intervention (visibility and temperature) is good. Showing, by the earlier mentioned PBD analyses, that a fire cannot spread to other compartments or buildings and that it won t affect the structural capacity of an adjacent compartment will conclude the PBD approach. It would then be possible to argue that this type of building with these three activities, even if not code compliant, is as safe for the occupants as the building type required by the prescriptive code.
OVERALL CONCLUSION A Spanish approach to this project would start with a prescriptive analysis, as have been shown all three activities would have problems to fulfill the code requirements derived from a prescriptive approach. Activity 1 and Activity 2 would even not be allowed in this type of building. The national code does allow for a performance based approach and this is a clear case where such approach would make this a viable project. It is mainly three areas that would need to be analysed in this way; structural behavior (there is a need to show structural independence between sector), fire spread (a fire in one sector is not allowed to spread to another sector or another building), smoke movement (tenable conditions must be maintained during evacuation and firefighting intervention). The detailed analysis, smoke movement, shown in this article shows that tenable conditions can be maintained during evacuation and firefighting intervention. This in conjunction with the other PBD analyses would form the base to justify these activities in this type of building. It is considered very important to mention that any type of PBD approach need to be discussed and agreed in detail with the Authority Having Jurisdiction (AHJ) before any detailed analysis is started. Not doing so can result in non-acceptance of the PBD analysis once presented to AHJ.
REFERENCES 1. RD 2267/2004, Reglamento de Seguridad Contra Incendios en Los Establecimientos Industriales, 3 rd of December, 2004, Spain 2. SFPE Engineering Guide to Performance Based Design, Analysis and Design of Buildings, 2 nd Edition, 2007 3. PD 7974-6:2004, Application of fire safety engineering principles to fire safety design of buildings. Human factors: Life safety strategies - Occupant evacuation, behavior and condition. 4. NIST Special Publication 1018 - Sixth Edition - Fire Dynamics Simulator - Technical Reference Guide Volume 1-4, Kevin McGrattan, Simo Hostikka, Randall McDermott, Jason Floyd, Craig Weinschenk, Kristopher Overholt - National Institute of Standards and Technology (NIST),(VTT), 2013. 5. Principles of Fire Behavior James G. Quintere, Delmar Publishers 1998. 6. Alpert, R.L., Calculation of Response Time of Ceiling Mounted Fire Detectors, Fire Technology, Vol 8, No. 3, August 1972, 181-195
APPENDIX A RISK LEVEL ANALYSIS The detailed risk level analysis has been shown for Activity zone 1, the following sections shows the main assumptions for this analysis. Formula The following formula is used to determine the risk value for storage areas. Where: : Fire load value within sector (Mcal/m 2 ), used to determine risk level : Danger coefficient related to combustibility (dimensionless) : Surface area of sector (m 2 ) : Danger coefficient related to ignition (dimensionless) : Height of storage material (m) : Surface area of storage material (m) : Fire load value for storage material (Mcal /m 3 ) Area of sector 6000 m 2 Storage volume The storage area is approximately 72m x 48m. It has been assumed that twelve (12) rows, each one 72m (length) x 2m (width) x 10m (height), is situated within this storage area. This gives a total storage volume of 17.280 m 3 Storage products & Material coefficients The products stored are document archives. In the national code [1] the following values should be used for that type of storage material. Energy value 409 Mcal/m 2 Ci 1.3 Ra 2.0
Calculation By suing the formula and the input data shown above the following risk value is calculated. Q s 3062 Mcal/m 2 This is gives the following risk level: High Risk (Level 8)
APPENDIX B FIRE SCENARIOS Fire Scenarios There are two fire scenarios developed for the analysis. 1. Fire within the high bay storage 2. Fire at floor level within the activity zone The high bay storage is equipped with in rack sprinklers and the entire activity zone is equipped with sprinklers, so both fire scenarios are sprinkler controlled. A fire controlled by the in rack sprinklers will be of a much smaller size than a fire controlled by the roof sprinklers. The smoke production rate is also higher for the fire controlled by the roof sprinklers, and this fire scenario will be evaluated in more detail. The following images shows the concept. Figure 12 Fire Scenario 2 (Fire at floor level within the activity zone 1)
Figure 13 Fire Scenario 2 (Fire seat at floor level within the activity zone 1) Figure 14 Fire Scenario 2 (extract points at roof level)
Design Fires Once the fire scenario has been established it is necessary to develop a design fire curve that will be used for the calculations. In this case the design fire curve is based on a sprinkler controlled fire. It is assumed that the fire grows until the sprinklers are activated and is then maintained at that size, a safety factor of 50% (increasing the maximum fire size) is also applied. The calculations are based on the Alpert formula [6] incorporated in a calculation tool developed by JVVA Fire & Risk.
Figure 15 Sprinkler activation The design fire curve used in the calculations have the following characteristics: Growth 0.047 (kw/s 2 ), Fast Maximum size 6.0 MW (safety factor included) Duration continued at maximum size
Decay not included This is considered to be a conservative design fire that will cover a large amount of different fire types. The fire curve can be seen graphically in the following image. Ventilation System Figure 16 Design fire curve A mechanical ventilation system has been foreseen for the area. The inlet air will come directly from outside via automatically opening vents (the loading bays). It has been assumed that four (4) openings can be provided, two from one side and two from the opposite side, each one with an area of approximately 16.0 m² (4.0m x 4.0m), a total of 64.0 m². The smoke will be extracted locally at high level. Ten (10) extract fans have been provided, each one with a capacity of 12 m 3 /s, a total of 120 m 3 /s.
APPENDIX C FIRE AND SMOKE MODELLING The following sections describes the Fire and Smoke Modelling analysis performed as part of this case study. Smoke Movement Smoke development and movement calculations have traditionally been undertaken using empirical formulae which assume a steady state fire at a given heat release rate, producing a constant quantity of smoke. However, those formulae (that are based on zone models) are weak if applied to large enclosures and when used to calculate the mixing between hot and cold layer may be not accurate. Zone models are indeed limited by their use of two horizontal layers without any temperature variation within a zone. Computational Fluid Dynamics (CFD) has been used to analyze the smoke movement as this analysis method assesses the transient movement of smoke in the space and takes account of complex flow patterns and geometries. CDF simulations The fire modelling of the main atrium utilized the CFD program called Fire Dynamics Simulator (FDS). FDS is a CFD model that utilizes a large eddy simulation (LES) turbulence package. FDS has been developed by the National Institute for Standards and Technology (NIST) for fire-driven fluid flow. The software numerically solves a form of the Navier-Stokes equations appropriate for low-speed, thermally driven flow with an emphasis on smoke and heat transfer from fires. Throughout its development, FDS has aimed to solve practical fire problems in fire protection engineering, while at the same time providing a tool to study fundamental fire dynamics and combustion. FDS Version 6.4.0 has been used in this study. For further information on the background and modelling equations of FDS readers are referred to the FDS User Guide and Technical Guide. These can be downloaded from: http://firemodels.github.io/fds-smv/. Model The model includes all the relevant feature of the building, the following images show different screenshots of the model.
Figure 17 Model Figure 18 Model
Figure 19 Model Mesh cell size The quality of the resolution depends on both the size of the fire and the size of the grid cells [4]. The characteristic fire diameter D* represents the combined effect of the effective diameter of the fire and its size, defined as follows: Where: D*: characteristic fire diameter, m; D : effective diameter, m; Q : total heat release rate, kw; r : density at ambient temperature, kg/m 3 ; cp : specific heat of gas, kj/kg.k; T : ambient temperature, K; g: acceleration of gravity, m/s².
The ratio D*/ max(δx, δy, δz) is an indication of the number of cells in the fire region, where δx, δy, δz = grid size in metres. As the ratio D*/ max(δx, δy, δz) increases, the accuracy of the fire dynamics solution and simulation also increases. Past experience has shown that ratios of 5 to 10 normally produces favorable results with a moderate computation time. Fire size D* max (δx, δy, δz) D*/ max (δx, δy, δz) 6000 kw 1,963643 0,4 5 Table 1 Mesh size Assumptions The most important assumptions are shown in the following table. Fire Parameters Inputs and assumptions Comments Fire size/ Fire growth Fast fire growth with a Heat Release rate of 6.0 MW. Fire location Characteristics of chemical reaction Floor Level in Activity Zone 1 SOOT_YIELD = 0.10 g/g Carbon atoms= 1.0 Hydrogen atoms= 1.7 Oxygen atoms= 0.3 This was considered the worst possible scenario Polyurethane has been used, this is considered a conservative estimate. Ventilation Parameters Inputs and assumptions Comments Ventilation There is a Smoke control system in the building. Inlet air is provided through natural openings at low level (see main report) Extract rate of 120 m 3 /s Inlet air 64 m²
Ambient conditions Parameters Inputs and assumptions Comments Temperature Wind Environment temperature, both indoors and outdoors is set to 20 ºC. The smoke control system is mechanical and for these reason it won t be affected by potential wind conditions. Geometry Parameters Inputs and assumptions Comments Material properties. MATL ID='Glass', FYI='Principles of Fire Behavior - J.Quintere 1998 - Delmar publishers, pg.238', SPECIFIC_HEAT=0.84, CONDUCTIVITY=0.76, DENSITY=2700.0/ &MATL ID='STEEL_MATL', SPECIFIC_HEAT=0.46, CONDUCTIVITY=45.8, DENSITY=7850.0/ &MATL ID='CONCRETE', FYI='Quintiere, Fire Behavior', SPECIFIC_HEAT=0.84, CONDUCTIVITY=0.48, DENSITY=1440.0, EMISSIVITY=0.6/ &MATL ID='Wood', FYI='Oak - Principles of Fire Behavior - J.Quintere 1998 - Delmar publishers, pg.238', SPECIFIC_HEAT=2.38, CONDUCTIVITY=0.17, DENSITY=800.0/ &MATL ID='PVC', FYI='NISTIR 1013-1 - NIST NRC Validation', SPECIFIC_HEAT=1.0, CONDUCTIVITY=0.1, DENSITY=1380.0, EMISSIVITY=0.95/ [5]
Thermal boundary conditions All materials have been set as thermally thick Computational Parameters Inputs and assumptions Comments Mesh size Mesh size - 0.4m The grid resolution for the fire mesh (0.4m) is considered to be adequate and consistent with the D*[4] Cells ratio 1:1 in all domain Table 2 CFD input Testing has shown that the closer a cell is to square the more accurate the results obtained from the FDS simulation. This is due to the Eddies within the zone being calculated based on the longest side of the cell.[] Design fire curve The following image shows the design fire curve. The fire development is limited by the activation of the sprinkler system. Figure 20 Design fire curve
Simulations output All FDS output must be specified before starting the simulation. The output data specified by all scenarios can be found in the following table. Output Parameters Inputs and assumptions Comments Slice Files Temperature Visibility Slices files were provided in 6 locations across the volume. These include cutting through the fire and at head height in order to show the progression of the Temperature and Visibility components of the fire and smoke. Their positions are best visualized in the figure below. Location of the slice files (yellow) in the X and Y directions Plot3D output quantities Temperature Visibility Recorded every 60 seconds Table 3 FDS output
Results The following sections shows the results, visibility and temperature, from the analysis. Visibility Visibility is an accurate instrument to quantify the thickness of the smoke layer (indirectly the smoke layer height), as it is directly related with the density of particles contained in this layer. The following images shows the visibility slice files (cut at 10m) within the space. Figure 21 Slice visibility, 60s
Figure 22 Slice visibility, 60s Figure 23 Slice visibility, 120s
Figure 24 Slice visibility, 120s Figure 25 Slice visibility, 240s
Figure 26 Slice visibility, 240s Figure 27 Slice visibility, 300s
Figure 28 Slice visibility, 300s Figure 29 Slice visibility, Steady state (600s)
Figure 30 Slice visibility, Steady state (600s) Temperature The following images show temperature slice files (cut 60ºC) within the space. Figure 31 Slice temperature, 300s
Figure 32 Slice temperature, 300s Figure 33 Slice temperature, steady state (600s)
Figure 34 Slice temperature, Steady state (600s) Conclusions The analysis shows that the established acceptance criteria are met within the space for the chosen fire scenario. Visibility and temperature within (along the evacuation routes) are well above the set limits. The smoke layer is maintained at a high level, approximately at 2m above the highest catwalk level. The smoke extract rate needed to maintain these criteria is 120 m 3 /s, the extract points are located at high level, there are ten (10) extract fans and each one is extracting 12 m 3 /s. The inlet air areas required (via automatically opening vents), the loading bays, are situated low level. The total amount of inlet air surface used in the analysis is 64 m². The inlet air velocity produced is around 2 m/s, which is below the normally used limit of 5 m/s, and therefore acceptable.