A New Zealand Case Study Building Design 11 th International Conference on Performance

Transcription

1 A New Zealand Case Study Building Design 11 th International Conference on Performance Prof Charles Fleischmann University of Canterbury Dept. Civil and Nat Res Eng. Christchurch, New Zealand Carol Caldwell Enlightened Solutions Limited PO Box 8709 Christchurch, New Zealand INTRODUCTION This paper presents the fire safety design of a case study building in accordance with existing New Zealand building legislation presented at the Society of Fire Protection Engineers - 11th International Conference on Performance-Based Codes and Fire Safety Design Methods. The case study building is a large logistical building that includes high rack storage areas, production space, and offices. The building includes a number of fire engineering challenges due to large footprint, high ceilings, and occupants at a high level in the space. This paper is intended to give a New Zealand design perspective. The analysis is based on the fire related clauses of the New Zealand Building Code (NZBC) 1, specifically the C clauses and other relevant building legislation. As stated in the briefing document provided by SFPE, the fire safety and design should meet following fire and life safety goals: 1. Safeguard occupants from injury due to fire and smoke until they reach a safe place. 2. Safeguard fire fighters while performing rescue operations or attacking the fire. 3. Minimize smoke and fire spread inside building. 4. Limit the impact on business continuity The first two goals, safeguarding occupants and fire fighters, are covered under the NZBC. The third and fourth goals are considered to be protection of the owner s property and are not accounted for in the building code. Under the NZ BC, a building owner has a responsibility to safeguard the occupants, allow fire fighters safe access for rescue and firefighting operations, and protecting other people s property. Protecting owner s property is not a requirement of the building code. In New Zealand, performance-based design is typically carried in accordance with C/VM2 Verification Method: Framework for Fire Safety Design 2 (C/VM2). C/VM2 describes a framework for performance-based design of a building in accordance with the NZBC. The verification method is one way to demonstrate compliance with the NZBC Clauses C1-C6 Protection from Fire. C/VM2 provides ten (10) scenarios that must be addressed. Design fires are specified for each scenario as well as the required acceptance criteria that must be achieved. This approach is intended to permit flexibility and innovation in design, while providing consistency between designs for very similar uses. In this study, C/VM2 is used to design this case study building to demonstrate that the design would meet the NZBC. C/VM2 is used a means of demonstrating that the case study building meets the goals of safeguarding occupants and firefighters. Because the third and fourth goals are not included in the NZBC, the associated design fires and acceptance criteria are more subjective and dependent on the building owners risk tolerance therefore these goals are covered in a more qualitative fashion.

2 NEW ZEALAND BUILDING LEGISLATION The Building Act 3 came into effect from 1 July It established a new system of building controls and it included a new performance-based building code. The NZBC was more flexible and significantly different to the previous bylaw system. All elements of building were brought into the scope of the Act including automatic systems such as automatic fire sprinkler systems and lifts. There was a significant revision to the Building Act in and in 2012 a new NZBC was published. The Building Act provides the legislative framework for building fire requirements. The NZBC provides the performance criteria. Council s previous bylaws were prescriptive and as each council had its own bylaws and there were inconsistencies between each local authority. The NZBC is performance based and provides objectives, functional requirements and performance criteria. The NZBC is divided into seven major Sections (Parts B-H). Part C of the NZBC is of particular interest in this case study as it deals entirely with Fire Safety for a building. The major objectives of the NZBC related to fire safety requirements: (a) safeguard people from an unacceptable risk of injury or illness caused by fire, (b) protect other property from damage caused by fire, and (c) facilitate firefighting and rescue operations. The NZBC (2012) provides explicit performance criteria for building design for fire safety which include: Maximum surface temperature for heating appliances Surface spread of flame performance for wall and ceilings linings Minimum critical radiant flux for flooring material Maximum fractional effective dose for carbon monoxide and thermal effects Minimum visibility due to smoke obscuration Firefighting vehicle access requirements Means of delivering water for firefighting to all parts of the building Construction requirements to maintain firefighting access and means of egress to the area of fire origin. Means for firefighters to establish the general location of the fire, identify fire safety systems, and the presence of hazardous materials. Provide structural stability during and after the fires for the protection of other property and safe access to firefighters. It is the responsibility of the designer to demonstrate that the building, as designed, will meet the NZBC. Typically, this is achieved by either following a Compliance Document referred to as an Acceptable Solution or a Verification Method. Although there are other ways to demonstrate compliance with the NZBC, including Alternative Solutions, these are not commonly used. New Zealand s Compliance Documents for Clauses C1-C6 Protection from Fire The Acceptable Solutions (New Zealand s deemed to satisfy documents) can be used for demonstrating compliance with the Building Code clauses C1 to C6 Protection from Fire.

3 There are 7 Acceptable Solutions for fire design which cover the various risk groups identified in the NZBC. In cases where there is more than one risk group in a building, it may be necessary to use multiple Acceptable Solutions to demonstrate compliance. All of the New Zealand legislative documents are freely available online at: ( C/VM2 Verification Method: Framework for Fire Safety Design In 2012, MBIE published New Zealand s first edition of C/VM2 Verification Method: Framework for Fire Safety Design for New Zealand Building Code Clauses C1-C6 Protection from Fire (C/VM2). The purpose of C/VM2 is to provide a robust and consistent design framework for specific design that allows creative and flexible performance based fire engineering solutions. C/VM2 is intended for use by design professionals with specific fire engineering expertise and designs are expected to be peer reviewed as part of the Building Consent approval process. C/VM2 defines a set of fire design scenarios including design fires with predetermined characteristics. The output of each fire scenario analysis is evaluated against a set of quantified performance criteria for life safety of occupants, protection of firefighters and protection of other property, with specific acceptance criteria required to be met in order for the design to be deemed compliant with the Building Code. Most building designs are assessed against ten design scenarios to ensure that the required range of challenges to the building has been explored in the design. Some scenarios require quantitative analysis and modelling, for example, ensure that the available safe egress time (ASET) exceeds the required safe egress time (RSET). Other scenarios can be satisfied either by inspection or by the provision of specific features, eg, fire separation, smoke detection systems or a second means of escape. In some cases, additional calculations are required e.g. to determine the required levels of fire resistance or the extent of radiation to a property boundary. A trial design is usually prepared as a first step, then assessed against the ten design scenarios. If the performance requirements of a scenario cannot be achieved, then the trial fire design needs to be altered and re-assessed against the design scenarios. This may result in iterations of a trial design until compliance with the performance requirements of all scenarios of C/VM2 are achieved. The proposed fire design is trialled using building specific fire design requirements agreed upon in the Fire Engineering Brief (FEB) process as described in International Fire Engineering Guidelines or similar. The 10 design scenarios are summarized in Table 1. Only a minimum amount of design methodology is included in C/VM2. The intention is to set up a framework for performance based fire design and it does not provide a detailed design process. It is up to the fire engineer to determine the best methodology to use for their building. The acceptance of the proposed methodology forms part of the Fire Engineering Brief process, for example, is zone modelling adequate for the ASET vs RSET analysis or CFD modelling necessary for the analysis. A number of fire modelling rules, design fire characteristics, pre travel activity times, and other parameters to be used in calculations are also given in C/VM2. In many cases these values are given in C/VM2 to provide guidance and to streamline the FEB process by removing the opportunity for disagreement over these values. The design fire input values are given in Table 2. For other specific values given in C/VM2 the reader is directed to reference [2]. Commentary on the specific values used in C/VM2 can be found in reference [5]

4 Design Scenario Title Brief Outcome required BE Fire blocks exit A fire starts in an escape route and can potentially block an exit. Demonstrate that a viable escape route (or multiple routes where necessary) has been provided for building occupants. UT Fire in normally unoccupied room threatening occupants of other rooms A fire starts in a normally unoccupied room and can potentially endanger a large number of occupants in another room. Demonstrate ASET>RSET for any rooms or spaces that can hold more than 50 people given a fire occurs in the normally unoccupied space. Solutions might include the use of separating elements or fire CS Fire starts in a concealed space A fire starts in a concealed space that can potentially endanger a large number of people in another room. suppression to confine the fire to the room of origin. Demonstrate that fire spread via concealed spaces will not endanger occupants located in rooms/spaces holding more than 50 people. This scenario is deemed to be satisfied by the use of separating elements, automatic detection or suppression. SF Smouldering fire A fire is smouldering in close proximity to a sleeping area. Provide an automatic smoke detection and alarm system throughout the building that has been designed and installed to a recognised national or international Standard. HS Horizontal fire spread A fully developed fire in a building exposes the external walls of a neighbouring building or firecell. Demonstrate that the criteria in C3.6 and C3.7 are not exceeded by calculating the radiation from unprotected areas in the external wall to the closest point on an adjacent boundary and at 1.0 m beyond an adjacent boundary, and specifying exterior cladding materials with adequate resistance to ignition. Control horizontal fire spread across a notional boundary to sleeping occupancies and exitways in buildings under the same ownership. VS External vertical fire spread A fire source exposes the external wall and leads to significant vertical fire spread. Demonstrate that the building s external claddings do not contribute to excessive vertical fire spread using one of the methods described. IS Rapid fire spread involving Interior surfaces are exposed to a growing fire that Demonstrate that surface finishes comply with these performance internal surface linings potentially endangers occupants. requirements. FO Firefighting operations Provide for the safe operation of firefighters in a building. Show that the performance requirements are satisfied. CF Challenging fire A fire starts in a normally occupied space and presents a challenge to the building s fire safety systems, threatening the safety of its occupants. Demonstrate ASET>RSET for design fires in various locations within the building. RC Robustness check The fire design will be checked to ensure that the failure of a critical part of the fire safety system will not result in the design not meeting the objectives of the Building Code. Demonstrate that if a single fire safety system fails, where that failure is statistically probable, the building as designed will allow people to escape and fire spread to other property will be limited. Table 1- Summary description of the 10 design scenarios required in C/VM to demonstrate compliance with the Building code

5 Table 2 - Pre-flashover design fire characteristics specified in C/VM2 2. Building use Fire Growth Rate (kw) Peak HRR/HRR/m 2 All buildings including storage t 2 20 MW with a stack height of less kw/m 2(1) than 3.0 m 250 kw/m 2(2) Carparks (no stacking) t 2 Capable of storage to a stack 0.188t 2 height of between 3.0 m and 50 MW 5.0 m above the floor Capable of storage to a stack t 3 H kw/m 2(1) height of more than 5.0 m 250 kw/m 2(2) above the floor and car parks Species Ysoot=0.07kg/kg YCO=0.04kg/kg Hc=20MJ/kg YCO2=1.5kg/kg (3) YH2O=0.82kg/kg (3) with stacking systems Note: t time in seconds H height to which storage is capable of in metres Yi mass yield of species i (kg/kg) Hc heat of combustion (MJ/kg) (1) In a CFD model the fire is intended to be modelled as a plan area where the size is determined from the peak HRR/m 2. A range is provided for HRR/m 2 to accommodate different HRR and mesh sizes. (2) Use in a zone model. (3) As an alternative to CO2 + H2O yields use generic fuel as CH2O0.5 and calculate yields. BUILDING DESCRIPTION Building description as given by Society of Fire Protection Engineers Brief The structure is a large speculative logistic building to be constructed on an unknown site. The building is divided into three equal tenant spaces separated by compartment walls. The building is 180m by 100m and has a 12m ceiling height. The tenant spaces include a range of activities as shown in Figure 1. The west tenancy is 60m by 100m with a 12m ceiling which is used as high bay storage for document archive. There are 2 levels of cat-walks at 4m and 8m above the ground. There is also 860m 2 of office space that is located above the docking area to the south of this space. The centre tenancy is 60m by 100m with a 12m ceiling used for high bay storage of auto parts and includes a man-up system in which the lift operator can be raised to the upper levels. The east tenancy is 50m by 100m with a 12m ceiling that includes furniture production and low level storage (3.8m storage height) for raw materials and finished products. There is also a 10m x 100m of office space on two levels included in this tenancy. There were no details provided regarding building access, construction materials, racking plans or site boundaries. Features of the building that have been assumed in the analysis Two fully enclosed fire rated stairways have been added from the office levels directly to the outside of the building to provide egress. Two egress doors have been added from each tenant

6 space, one in the north wall and one in the south wall. All of the features added to the case study description have been marked in red on Figure 1. The number of occupants in the building is based on the floor area and the occupant densities given in Table 3.1 of C/VM2. However, under special circumstances such as in the furniture production space, the occupant load can be based on an agreed value with the owner s signed confirmation. Occupant load calculations are summarized in Table 3. Table 3 - Occupant Loads of all major spaces within the building as defined by C/VM2 and C/AS Floor Area Occupant Density (m 2 /person) Occupants Load (# Persons) Space m 2 Document archive storage Office over dock Auto part storage Furniture production 5000 * 60 East office ground level East office level *Occupant load based on agreed value

7 Figure 1 - Concept drawings for corporate office building used in SFPE case study. C/VM2 VERIFICATION METHOD: FRAMEWORK FOR FIRE SAFETY DESIGN This section covers the performance-based design for the SFPE case study building of a large logistical building that includes high rack storage areas, production space, and offices. The design follows C/VM2 design framework and applies this methodology without prejudice or justification. All 10 design fire scenarios will be evaluated to demonstrate that the building design meets the Building Code C-clauses: Protection from Fire. Primary Fire Safety Design Features for the Building for Performance-Based Design The building will include a fully compliant sprinkler system that is designed in accordance with NZS The upper level office spaces are considered to be separate firecells to the ground which requires that the floor and supporting structure are able to resist collapse for a period of 60 minutes. Design scenario BE - Fire blocks exit Design scenario BE addresses a fire that starts in a location that potentially blocks the use of an escape route. The scenario applies when there are more than 50 people that could be affected by such an event. Any space where the escape routes serve more than 50 people is required to have at least two exits. The exits must either: diverge by more than 90 degree, or if not suitably divergent, be separated by a distance of: o at least 8m when up to 250 occupants are required to use the escape routes, or

8 o at least 20m when more than 250 occupants are required to use the escape routes. if there is an escape route with a single direction of travel, the maximum length of that single direction shall not be greater than 50 m if occupants are familiar with the building From inspection of the floor plan in Figure 1, it can be seen that main floor spaces have at least two escape routes on opposite sides of the building. The office spaces each have two means of escape through stairways one on each end office areas. There are no details for the cat-walks thus this would require final approval once a layout is proposed. Therefore, the design complies with the design scenario BE: Fire blocks exit. Design scenario UT - Fire in normally unoccupied room threatening occupants of other rooms Design scenario UT deals with a fire in a normally unoccupied room remaining unnoticed and threatening a large number of occupants in an adjacent space. Because the building is fully sprinklered and this is expected to contain the fire to the room of origin, no other analysis is required. The design complies with design scenario UT: Fire in normally unoccupied room threatening occupants of other rooms. Design scenario CS - Fire starts in a concealed space Design scenario CS addresses the concern of a fire developing undetected in a concealed space and spreading into any space containing a large number of occupants. Because the building has a fully compliant sprinkler system throughout the building that requires sprinklers in the concealed space that will provide a means of early detection as described in methodology b) in Paragraph 4.3 of C/VM2, no additional analysis is required. The design complies with Design scenario CS: Fire starts in a concealed space. Design scenario SF - Smouldering fire Design scenario SF addresses the concern that a smouldering fire can threaten sleeping occupants. The only methodology available is to install smoke alarms in all sleeping spaces. Because this building does not include any sleeping space this scenario is not required. Design scenario HS: Horizontal fire spread Design scenario HS addresses the concern that a fire in a building will damage adjacent property. To comply with this scenario, it is necessary to do one of the following: if the separation distance is 1.0m or less, completely fire rate the boundary wall, or if the separation distance is more than 1.0m, limit the area of unprotected openings to control the thermal radiation to the adjacent property.

9 This design scenario also prevents an owner from constructing their building with an external cladding that is easily ignited within 1.0m of their boundary (in case of fire in the adjacent property). According to the Building Code clause C3.6: Buildings must be designed and constructed so that in the event of fire in the building the received radiation at the relevant boundary of the property does not exceed 30 kw/m² and at a distance of 1 m beyond the relevant boundary of the property does not exceed 16 kw/m². C/VM2 states that the maximum width of the radiator is 30m (for buildings with high fuel load) and that the height shall be the height from the floor to ceiling, 12m in this case. Further, the heat flux from a storage building is 144kW/m 2. Using these values for the radiation from a rectangular radiator to a point opposite the centre, the building must be setback at least 20.4 m from the boundary. If the separation is less than 20.4 m then some portion of the exterior wall would be required to be fire separated to reduce the size of the assumed radiator. To address the ignitability of the boundary wall, any external wall located closer than 1.0m to the relevant boundary must be externally clad with either: materials that are not combustible, or materials that, when subjected to a radiant heat flux of 30 kw/m 2, do not ignite for 15 minutes (Importance level 2). These measures mitigate fire spread from a neighboring property. Typically, in New Zealand a building like this would have either steel or concrete cladding which are both noncombustible and are not able to be easily ignited. In the absence of details regarding the boundary separations, the design is considered to comply with Design scenario HS: Horizontal fire spread. Design scenario VS: Vertical fire spread involving external cladding Design scenario VS deals with fire spread up the exterior of a building that: is greater than 10 m high, or has sleeping occupants above the ground floor. There are two facets to this scenario: Part A: External vertical fire spread over the façade materials, and Part B: Fire plumes spreading fire vertically up the external wall via openings and unprotected areas. For Part A, the exterior cladding of this building is assumed to be non-combustible (i.e. noncombustible as determined by the test specified in AS ). For Part B, the risk of fire spread via openings and unprotected areas is mitigated by the presence of the automatic sprinkler system.

10 The design complies with Design scenario VS: Vertical fire spread. Design scenario IS: Rapid fire spread involving internal surface linings Design scenario IS deals with the condition where a fire within a building can develop too rapidly to allow occupants sufficient time to escape. Controlling the flammability of the internal surface linings reduces the likelihood of a fire developing more rapidly than the design fires given in Table 2.1 of C/VM2. Surface finishes within the building are required to meet the following requirements for sprinkler protected buildings (C/VM2 Paragraph 4.7). Surface linings; walls and ceilings Group numbers are derived from testing to ISO 5660 or ISO Exitways (fire separated stairs) and internal ducts: Group number 2 (or lower) All other occupied spaces: Group number 3 (or lower). Flooring Minimum critical radiant fluxes (CRF) are assessed according to ISO Flooring within exitways (fire separated stairs) shall have a CRF 2.2 kw/m 2 Flooring within all other occupied spaces shall have a CRF 1.2 kw/m 2. Foamed plastics Where foamed plastics or combustible insulating materials form part of a wall, ceiling or roof system, the completed system shall achieve a Group Number as specified for surface linings above and the foamed plastics shall comply with the flame propagation criteria as specified in AS 1366 for the type of material being used (C/VM2 Paragraph 4.7). In the absence of details regarding the interior surface finish, final design would require the fire engineer to approve all surface lining material in order to comply with Design scenario IS - Rapid fire spread involving internal surface linings. Design scenario FO - Firefighting operations Design scenario FO ensures the provision of the safety of firefighters conducting search and rescue and firefighting operations. Design scenario FO is prescriptive in nature simply because there is no design methodology available to address these issues. The following items address all the issues specified in C/VM2 for design scenario FO. As the building is fully sprinklered, it is not necessary to analyze the fire environment at the time firefighters first apply water as described in NZBC Clause C3.8. Clause 5.3 requires a hard-stand from which there is unobstructed access to the building. This is expected to be provided on the North and South sides of the building. Clause 5.5 requires a means of delivering water for firefighting to all parts of the building which is achieved by providing hard-stand near the external doors on the north and south

11 sides of the building allowing pumping appliance park close to the building such that any point within the building may be reached within 75 m (~3 hose lengths) of the pumping appliance Figure 2 Floor plan of the building shows a 65 m arcs from the building access points allowing the fire service park up to 10m from the building demonstrating adequate coverage from the pumping appliances. Clause 5.6, 5.8 & 6.3 require that firefighter have safe access to the building. Because the building escape height 10m there is no requirement to protect the exterior walls or roof for this building. The two office spaces are separate firecells to the ground floor and fire separated to 60 minute fire rating. ;. Clause C5.7 requires a fire alarm panel that provides information about the general location of the fire, fire safety systems in the building, and the presence or hazardous substances or processes. The location of the fire alarm panel and fire service inlet would be expected to be discussed and agreed as part of the FEB process. These will have to be located close to the NZFS attendance point. The design complies with Design scenario FO: Firefighting operations. Design scenario CF: Challenging fire Design scenario CF is concerned with a fire that starts in a normally occupied space that will challenge the building s fire safety systems and threaten the occupants. Compliance with the CF scenario is achieved by demonstrating that ASET>RSET.

12 When evaluating a building design for the CF scenario, one of the most important decisions is the location of the challenging fires. Typically, there are multiple locations where a challenging fire needs to be considered. The locations where the CF fire will be evaluated is agreed upon by all parties during the Fire Engineering Brief process. (Although not applicable to this building, if a space is less than 500m 2 and less 150 people than tenable conditions do not have to be assessed within that space but the effect on the rest of the building must still be considered.) The ASET is generally defined as the shortest time to reach any of three tenability criteria specified in NZBC Clause C4.3 1 : C4.3 The evacuation time must allow occupants of a building to move to a place of safety in the event of a fire so that occupants are not exposed to any of the following: (a) a fractional effective dose of carbon monoxide greater than 0.3: (b) a fractional effective dose of thermal effects greater than 0.3: (c) conditions where, due to smoke obscuration, visibility is less than 10 m except in rooms of less than 100 m 2 where visibility may fall to 5 m. C4.4 Clause C4.3 (b) and (c) do not apply where it is not possible to expose more than 1000 occupants in a firecell protected with an automatic fire sprinkler system. As this building is sprinkler protected with less than 1000 people exposed to the fire, Clause C4.4 applies and the tenability requirements are limited to C4.3.(a); i.e. the FED(CO). In this case study, two locations for the challenging fire have been included to demonstrate how C/VM2 is applied in performance-based design. These include: Fire centered in the document archive high-bay storage area with the cat-walks at 4m and 8m. Placing the fire 0.5m above the floor is expected to give the longest time between ignition and sprinkler activation and the largest sprinkler controlled fire. The largest fire leads to the greatest release of toxic products from the fire. 1. Figure 3 shows the location of the fire within the building as modelled in the Fire Dynamics Simulator version (FDS6). Figure 3 - Challenging fire in high bay storage of document archive with cat-walks at 4m and 8m. 2. Fire in the open plan office space on the east side of the building is required because the office space is greater than 500m 2. This space was modeled as a single level open plan space. It was assumed that each level is separated and was modelled in

13 isolation of the rest of the building. Figure 4 shows the open plan office area with a fire in the center of the room, 100 s after ignition. Figure 4 - Challenging Fire on open plan office showing the fire centered in the space at 100s after ignition. Other locations in the building were considered but discounted for analysis, these include: 1) High bay storage of car parts with man-up system space was considered to be substantially similar to the document archive with less complex egress. The manup system was assumed to be a forklift with the ability to take an operator up high to reach items on the upper levels. With such a system, a trained operator would be able to quickly lower themselves out of any smoke and then egress the building from the ground level before the ASET is exceeded. 2) Furniture production and storage according to C/VM2 it has a slower fire growth rate than the high bay storage spaces and similar occupant load. The space is therefore considered to be a longer ASET than the document archive storage area already considered. 3) Office above docking - space was considered to have similar fire development to the 2 floor office space with fewer occupants which would lead to a similar ASET and a smaller RSET. Fire Modelling Analysis Due to the size and shape of the building FDS6 was used to evaluate the ASET. The geometry is as shown in the Figure 5 depicting a fire in document archive storage of the high bay space. The entire area was modelled as a single mesh 0.5m by 0.5m by 0.5m. Tenability was monitored at 60 points throughout document archive and at three levels 2m, 6m and 10m which is 2m above each occupied level including the 2 cat-walks. The green dots in Figure 5 show the locations for monitoring the tenability. The locations of the fire, sprinkler heads, and smoke detectors are barely visible in Figure 5. The sprinklers are spaced on 4.6m spacing which gives the C/VM2 required radial distance of 3.25m. Standard response sprinkler heads were used in the analysis with the following properties specified in C/VM2: Standard Response Sprinklers RTI = 135m 1/2 s 1/2 C = 0.85 m 1/2 s 1/2 Tact = 68ºC Radial distance = 3.25m Distance below ceiling = 25 mm According to C/VM2 smoke detectors are assumed to activate when the optical density outside the detector reaches m -1. Detectors are placed at 10m spacing which

14 corresponds to 7 m radial distance from the center of the fire. Smoke detectors were included in the initial design phase but have not been incorporated in the final design. Walls and ceiling storage spaces were modeled as sheet metal and the floor was assumed to be concrete using common thermophysical properties taken from reference 7. Figure 5 - Plan view showing an exemplar floor plan, the fire is visible in the document archive storage in the high bay space. The design fire characteristics were consistent with the parameters given in C/VM2 as described in Table 2. In the high bay storage with a 12m ceiling height, the growth rate of Q= t 3 H for rack storage with a physical size based on 1000kW/m 2 HRRPUA 2500kW/m 2. (Note C/VM2 has taken the growth rate for storage from work by Ingason 8 ). The height of storage was assumed to be 1m less than the ceiling height, 11m in this case. The fire is controlled by sprinklers that activate at 125s which gives a maximum heat release of 14,600kW. The D*/x is consistent with the range for validation work for hot gas layer analysis found in the FDS validation guide 9 of 4 D*/x 16. D*is calculated as: * Q D c pt g 2/ / * D x 0. 5 Thus the D*/x is within the desired range so no specific sensitivity analysis was considered. The layout for the office space along the eastern side of the building is shown in Figure 6. According to C/VM2 an office fire is considered to be a fast t 2 fire growth rate with physical size based on 500kW/m 2 HRRPUA 1000kW/m 2. With an assumed 3m ceiling height, sprinklers activate 175s which gives a maximum heat release rate of 1430kW. Due to the lower peak heat release rate and lower ceiling height, the mesh size was 0.2 m in all directions which gives a D*/x=5.5.

15 Figure 6 - Plan view of the open plan office space along the Eastern side of the building. Tenable Criteria The tenability criteria given in C/VM2 were used for determining ASET. Because the building includes a compliant NZS4541 sprinkler system and less than 1000 occupants, only the FED(CO) is assessed. In the document archive space, the FED(CO) was monitored at 60 points at three different levels above the floor: 2m, 6m, and 10m. The 3 levels were monitored to assess the tenability 2m above the main floor and 2m above each level of the cat-walk. In the office space, FDS(CO) was monitored at 20 points at a height of 2m above the floor. This gives a maximum spacing between tenability monitoring points of 10m. The locations can be seen as the green dots in the Figure 5 & Figure 6. ASET Results In each of the challenging fire locations the FED(CO) never exceeded 0.3 for the entire 900s simulation. For the 900s simulation time, the maximum FED(CO) in the document archives was FED(CO) = 0.17 at a height of 10m above the floor. Figure 7 shows the average FED in the document archives at 10m, 6m, and 2m above the floor. It shows that the FED(CO)<0.3 for the entire 900s simulated meaning that the ASET for this space is greater than 900s. In the open plan office space, the FED(CO) never exceeds 0.3 in the 900s simulation. TheFED(CO) values at all 20 monitoring points are shown in Figure 8. For all 20 monitoring location within the office space, the maximum value was FED(CO)=0.21. Therefore, the ASET for the office is >900s.

16 FED(CO) FED(CO) FED(10m) FED(6m) FED(2m) Time (s) Figure 7 Tenability results in the document archive based on the average FED(CO) at 10m, 6m and 2m above the floor level Time (s) Figure 8 - Tenability results in the open plan office based on the FED(CO) at all 20 monitoring points. RSET Analysis The RSET is defined as the time required for all occupants to reach a place of safety. C/VM2 Paragraph 3.2 states that the RSET is the sum of the detection time, notification time, pre-travel activity time, and the greater of the travel time or the flow time. C/VM2 gives times for the

17 pre-travel activity times that are intended to account for the occupant behavior and are dependent on the use of the space. These times may be considered optimistic in some countries, however, in New Zealand there exist the Evacuation Regulations which require most commercial buildings open to the public to have an approved evacuation scheme. As part of the scheme, regular trial evacuations are required which has resulted in a widespread culture of evacuating a building promptly when the fire alarm sounds. C/VM2 includes a basic methodology for modeling the evacuation based on the simple hydraulic flow analogy. For more sophisticated egress analysis the designer is directed to The SFPE Handbook of Fire Protection Engineering 4 th edition, Section 3 Chapter 13 which provides additional information on calculating the RSET. Because the ASET is large (tenability criteria of FED(CO)=0.3) was never reached in the 900s simulation) a simple calculation that results in a conservative value for the RSET time can be used to demonstrate that the ASET > RSET. Although more sophisticated egress analysis could be performed such analysis is not warranted. The following steps show how the RSET was obtained: 1. From the FDS results the sprinklers activated at 125s for the fire in the document archive. In the east office fire scenario, the sprinklers activated at 175s. The longer sprinkler activation time for the office fires is due to the slower fire growth compared with the growth rate for the storage fire. 2. C/VM2 section specifies an alarm notification of 30 s should be included in the RSET analysis. 3. The pre-travel activity times are given in Table 3.3 of C/VM2. For a building where the occupants are considered to be awake, alert, and familiar such as offices and warehouses not open to the public, the pre-travel activity is given as 30s for the enclosure of fire origin and 60s for the enclosures remote from the fire. In this case 30s is used for space of fire origin (document archive space) and 60s would be used for all other spaces. 4. The layout of the egress in all storage spaces is assumed to be the same and is taken as the orthogonal distance to the closest exit. It is assumed that two exits are provided from each large space given and these exits are in opposite corners of each space as shown in Figure 1. In this case the travel distance is taken as half the width plus have the length of the space (30m + 50m=80m). Due to the low occupant load, the occupants are assumed to be able travel at the maximum walking speed of 1.2 m/s which gives a maximum horizontal travel time of 67s. This value also applies for the travel time from car parts storage and production space. An additional 30s will be added to the manup space to allow the lift operator to descend to the ground level. Such a value would be agreed on by all interested parties during the FEB process. 5. For the office the orthogonal length is (5m + 50m=55m) giving a horizontal travel time of 46s for the office. 6. With no detail given regarding the cat-walk layout, the occupants on the cat-walk are assumed to have the same horizontal travel distance as the ground level given above plus an additional travel time to traverse the stairs. The stairs are assumed to be accessible stairs as defined in D1/AS1Access Routes 10 with a tread length of 310mm and a riser height of 180mm. Thus for a 4m vertical distance between cat-walks and cat-walk to floor there would be 23 stairs required for each 4 m of vertical distance. Giving a distance of 4m for the stairs and 7.1 m for the treads that results in a diagonal travel distance for the stairs of 8.2m. In addition, one landing is also required between

18 each level that must be a minimum of 0.9m, giving a total travel distance for the stairs between levels of 9.1m. Travel speed down the stairs is 0.95 m/s taken from Table 3.4 of C/VM2 thus giving a travel time from each level of 9.1m/0.95m/s = 10s. This 10s travel time down the stairs is also used for the egress from the office stairs that are only 3m vertically but do not warrant a separate calculation. 7. Assuming a maximum travel time from the 8m cat-walk would be: a. 67s from location to catwalk stairway b. 20s to travel down 2 flights of stairs to ground level c. 67s from stairway to final exit d. 154s total travel time 8. The doors to the stairways are 950mm wide with a capacity of 50people/min. Assuming 30 occupants egress through each door the maximum queuing (flow) time would be 36s. 9. Therefore the egress is governed by the travel time and not the flow time. Thus the final egress times are: RSET for fire on ground level of document archives RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 30 Travel time 67 Total RSET 252 RSET for 4m cat-walk level of document archives when fire is in archive storage RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 30 Travel time 144 Total RSET 329 RSET for 8m cat-walk level of document archives when fire is in archive storage RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 30 Travel time 154 Total RSET 339 RSET for ground level of car parts storage when fire is in archive storage RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 60 Time man-up operator to descend 30 Travel time 67 Total RSET 312

19 RSET for ground level of production space when fire is in archive storage RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 60 Travel time 67 Total RSET 282 RSET for office space when fire is in archive storage when fire is in archive storage RSET Component Time (s) Detection time 125 Notification time 30 Pre-travel activity time 60 Travel time 46 Total RSET 261 RSET for east office space when fire is in the east office space RSET Component Time (s) Detection time 175 Notification time 30 Pre-travel activity time 30 Travel time 67 Total RSET 302 RSET for 8m cat-walk level of document archives when fire is in east office space (Longest RSET for the building) RSET Component Time (s) Detection time 175 Notification time 30 Pre-travel activity time 60 Travel time 154 Total RSET 419 The maximum RSET (>339s fire in the document archive and 419s fire in the east office) are much less than ASET (>900s) therefore the design complies with Design scenario CF: Challenging fire. Design scenario RC - Robustness check Design Scenario RC applies where failure of a key fire safety system could potentially expose to untenable conditions: a) more than 150preople or b) more than 50 people in sleeping occupancy firecell or c) people detained or undergoing treatment of care.

20 The building is fully sprinklered in accordance with NZS4541 which has strict design, certification, and maintenance requirements therefore consideration of failure of the sprinkler system is not required. The building has no smoke management systems or any other features or life safety systems in the building that rely on a mechanical or electronic component to be activated during the fire. The only system in this building that requires assessment when considering design scenario RC are the fire doors on the fire rated stairs. However, in the analysis for all of the challenging fires, the FED(CO) never exceed 0.3, therefore, it is reasonable to assume that the FED(CO) in the stairway would not exceed 0.3 thus further analysis of this scenario is not necessary. The design complies with Design scenario RC Robustness check. PROTECTION OF OWNERS PROPERTY Maintenance Under the 2004 Building Act 4 the owner has an obligation to ensure that any specified system in their building will continue to perform to the original performance standard. A specified system is any system in the building that is required for maintaining health or life safety of the building occupants. Specified systems include fire alarms, sprinkler systems, smoke managements systems, fire doors, etc. Any specified system in a building must be documented in the compliance schedule for the building. Upon completion of consented building work, the local authority will provide a compliance schedule that includes: 1. Detailed description of each specified system 2. Performance standards for each specified system 3. Inspection and maintenance procedures required for each specified system On an annual basis, the owner is required to issue a Building Warrant of Fitness (BWOF) that states that all of the inspections, maintenance and reporting procedures for all of the specified systems have been conducted. The inspection and maintenance on any specified system must be carried out by an independent qualified person (IQP) who is required to provide documentation to the owner that the system have been inspected and maintained. A copy of the BWOF and IQP reports must be submitted to the local authority annually. If the owner does not comply with the above procedures, the Building Act includes a range of penalties up to $20,000. The stringent BWOF scheme helps to ensure that a buildings fire safety features will be able to perform as designed when needed. PROPERTY PROTECTION GOALS Under the objectives for this project, two of the four goals are considered to be primarily for the protection of the owner s property. Under the New Zealand building legislation, protection of property is the owner s responsibility, therefore, there are no explicit provisions for property protection with in the Building Code and there are no scenarios within C/VM2 for property p[protection. Therefore, the level protection of property incorporated in a fire design is dependent on the owner s objective, budget, and risk tolerance. Based on the owner s objectives, the following strategies would be considered to reduce property damage in this building:

21 1. Enhancement to the sprinkler system under the current design a ceiling mounted sprinkler system is used. Such a system, would result in the longest time to activation and the largest fire. It is likely that the sprinkler performance could be improved through the use of in-rack sprinklers or special application heads depending on the details of the storage array and materials involved in the fire. 2. Improved compartmentation under the current code complying design, the walls are not required to be fire or smoke separations. However, these could be upgraded to reduce the spread of smoke and fire. a. Smoke separations reduce the spread of smoke within the building but would provide little protection from fire spread in the unlikely event that the sprinklers control the fire. b. Fire separations could be installed to withstand burnout in the unlikely event that the do not sprinklers control the fire. 3. Smoke detection there is no requirement for smoke detection within the current design. Smoke detection has the advantage of alerting the occupants to a fire more quickly than sprinklers and possibly in time for trained occupants to extinguish the fire before the sprinklers activate. There are a number options that could be used ranging from analog addressable spot detectors to aspirated smoke detector that can detect smoldering fires. Such systems are not required for life safety in this building and to be most effective would require trained personnel to be available to extinguish the fire. 4. Smoke exhaust there currently is no requirement for smoke exhaust. Smoke exhaust has the advantage of reducing (but not eliminating) the spread of smoke through active means. In a building this large, a smoke management system would require on the order of 100 s m 3 /s depending on the tolerable smoke layer height, the higher the smoke layer the more exhaust is required. Figure 9 shows a sprinkler controlled fire with 200m 3 /s exhaust from the document archive space showing the level of smoke in the building even with smoke exhaust. Other enhancements may be possible, such draught curtains to confine the smoke to a smaller portion of the space. However, such systems can be quite expensive and may not be cost effective. 5. Other special fire suppression systems such as gas flooding or oxygen reduction systems are available but are normally not cost effective except in applications this large. Such systems are considered to be beyond the scope for this case study. Although there are a number of option available to reduce the property damage in this facility, the authors believe that there is a diminishing return on the owner s investment when a fully compliant sprinkler system is installed and properly maintained in the building. Figure 9 - Smokeview image showing the smoke layer height in the document archive space with 200m 3 /s exhaust for a sprinkler controlled fire.

22 SUMMARY This paper presents a performance-based fire safety design for a large logistical building that includes high rack storage areas, production space, and offices. The building includes a number of fire engineering challenges due to large footprint, high ceilings, and occupants at a high level in the space. The primary fire safety strategy relies on a fully complaint sprinkler system throughout the entire building. The methodology for this design relies on the New Zealand framework for performance design contained within the Verification Method, C/VM2 2. The 10 fire scenarios, acceptance criteria, and fire modeling rules included within C/VM2 were analyzed to demonstrate that the building design complied with the objectives of the NZBC. The NZBC does not account for the protection of the owner s property and thus provisions for property protection are at the owners discretion. A number of strategies to improve property protection were discussed but not implemented due to the limited detail provided in the design brief. RFERENCE 1 New Zealand Building Code, Ministry of Business, Innovation & Employment, New Zealand, C/VM2 Verification Method: Framework for Fire Safety Design - For New Zealand Building Code Clauses C1-C6 Protection from Fire, Ministry of Business, Innovation & Employment, New Zealand, Building Act, Ministry of Business, Innovation & Employment, New Zealand, Building Act, Ministry of Business, Innovation & Employment, New Zealand, Commentary for Building Code Clauses C1-C6 and Verification Method C/VM2, Ministry of Business, Innovation & Employment, New Zealand, December C1-C6 Protection from Fire, Ministry of Business, Innovation & Employment, New Zealand, July NZS 4541:2013-Automatic fire sprinkler systems, Standards New Zealand Drysdale, D., An Introduction to Fire Dynamics, 2nd Edition, Table 2.1, Wiley, Ingason, H., Heat Release Rate of Rack Storage Fires, Proceeding of INTERFLAM 2001, Interscience Communication Limited, London, UK, McGrattan, K, Hostikka, S, McDermott, R, Floyd, J, Weinschenk, C, and Overholt, K, Fire Dynamics Simulator Technical Reference Guide Volume 3: Validation, NIST Special Publication , 6 th edition, D1/AS1 - Compliance Document for New Zealand Building Code Clause D1 Access Routes Second Edition, Department of Building and Hosing, Ministry of Business, Innovation & Employment, New Zealand, 2011.