EVACUATION & LIFE SAFETY STRATEGIES FOR SUPER HIGH RISE BUILDINGS By Sam Aloi, Grad. Dip. (Fire Safety & Risk Eng.)VUT Melb, BE (Building) VUT Melb. & Jason Rogers, Grad. Dip. (Fire Safety & Risk Eng.)VUT Melb, Ass. Dip. (App. Sci.) SU. Norman Disney & Young Level 6, 5 Queens Road, Melbourne, Victoria, 3004, Australia EMAIL s.aloi@ndy.com, FACSIMILE +61 3 9862 6900, TELEPHONE +61 3 9862 6850 ABSTRACT The paper will discuss strategies implemented for ensuring safety of occupants in tall buildings under fire conditions. The life safety strategy must integrate key fire safety systems with building features. The possible use of vertical transportation for phased evacuation requires a combination of safe havens, innovative smoke management and sophisticated communication systems to ensure occupants under threat from fire are moved to safe locations within the building. Application of smoke analysis to confirm the effectiveness of designs will be considered. Theoretical design will be supported by practical examples currently being implemented on the 88 level Eureka Tower in Melbourne, Australia. The Eureka Tower project is being developed by a joint venture made up of the Grocon Group, the architect Nation Fender Katsalidis and Tab Fried. The Builder is Grocon Constructors Pty Ltd.
INTRODUCTION The height of very tall buildings places great demand on time for occupant evacuation, fire fighting, search and rescue and preservation of the building. In considering fire protection measures for tall buildings, it has become evident that the safety of occupants and fire fighting personnel depends on the design of the building as a whole. A fire engineered approach was used in the design of Eureka Tower in Melbourne, Australia for compliance with the performance requirements of the Building Codes. Eureka Tower is primarily a residential building comprising 88 storeys at a total height of approximately 300 metres. The development is to be the world s tallest residential skyscraper. Eureka Tower sits above a 10 storey podium which incorporates car parking, health centre and gymnasium, shopping, retail outlets, restaurants and cafes. In addition to this, the top four storeys include professional and recreational facilities as well as designated areas that will be freely accessible by the public, namely the observation deck. Fig. 1 The focus of the life safety strategy was to protect people in place. High rise building occupants near the fire would evacuate using the vertical transportation system; whilst occupants remote from the fire would remain protected within the structure. To facilitate this strategy, the fire must be kept small and the persons in the area of fire origin must be permitted to move safely within the structure. The key to the strategy was the design of an integrated fire safety system, with consideration to unique building features that influence fire and smoke spread throughout the building. Blindly following the prescriptive requirements of the Building Codes would not address these issues. A fire engineered approach assesses the level of fire safety and establishes innovative fire safety solutions to suit the specific risk.
FIRE DEVELOPMENT & SMOKE SPREAD The fire scenarios used within the quantitative fire and smoke analysis for the building were determined via a hazard analysis. Various fire scenarios were considered within the residential, office and public areas of the building to determine the fire risk based on ignition potential, frequency and consequence. The combustible fuel load throughout the building is expected to vary in content and location. Therefore representative design fires we developed utilising a combination of the anticipated fuel loads, fire test data and statistical information. The considered design fires can be categorized into three main groups being smouldering fires, flaming fires and flashover fires. Smouldering fires are generally a poorly ventilated fire producing very little heat and thus not expected to spread beyond the object of fire origin. The HAZARD I zone computational model, as developed by the United States Department of Commerce- building & Fire Research Laboratory, was used for the quantitative analysis of fire spread from typical apartments to egress paths. Time to untenable conditions were then compared with egress and people movement. EGRESS & PEOPLE MOVEMENT As buildings reach for the heavens, we can not expect building occupants to evacuate using traditional means of egress via hundreds of flights of stairs. Egress down multiple flights of stairs is expected to slow down occupant evacuation, create queuing and bottle necks and cause injury. Studies suggest that it is often the journey to the outside that leads to injury or fatality, with the risk of injury increasing with the number of floors traveled.
To minimise occupant travel distance within the stairways, the Eureka Tower was separated into Evacuation Zones according to the proposed lifting arrangement of the building. (three vertical transportation system zones) Fig. 2 The evacuation process and fire safety systems can be best explained as follows: 1. The occupants in the EVACUATION ZONE FLOOR OF FIRE ORIGIN ONLY via the fire isolated stairs which discharge to Transfer Levels. 2. At the Transfer Level, occupants are transferred to express lifts (located in separate shafts to avoid smoke/water damage and provide unimpeded Brigade access to the fire floors via goods lifts) and shuttled to ground floor for direct egress. To permit orderly evacuation, it is proposed to evacuate only the Floor of Fire Origin (FFO) in the first instance. Occupants in Evacuation Zones and Floors of Non-Fire Origin remain in place. Alert and evacuation information in the form of pre-recorded messages is communicated to these floors as required. Occupants are also provided with the option for building evacuation via the fire isolated stairways if required. Table 1 provides a summary of the number of occupants evacuated and evacuation times for the respective evacuation zones. Evacuation Zone Levels Served No. Lifts Serving Evacuation Area No. Occupants Transfer Floor Area Total Zone Evacuation Time Evacuation of Four Floors 2 L24 to L51 2 x 17 passenger 970 persons Lobby 1 hr 6 mins 16.5 mins Area 3 L52 to L88 3 x 17 passenger 1303 persons 455 1 hr 10 mins 33 mins Table 1. Egress & People Movement Elevators are being considered to be the primary mode of evacuation from high rise buildings in Australia, with some buildings proposing to evacuate the FLOOR OF FIRE ORIGIN using the lift which awaits them, called by the smoke detection system and protected by lobby and air pressurised system.
EMERGENCY EGRESS USING VERTICAL TRANSPORTATION SYSTEMS Emergency egress using vertical transportation has been acknowledged as a priority in Australia. Currently Australian regulations and standards do not permit the use of vertical transportation for egress in case of fire. British Standard BS5588 allows fire fighting personnel or people with disabilities to use the lifts in the event of fire, provided the evacuation is managed and elevator system is suitably designed and protected by the building. European Normalised Standards EN 81-72: Fire Fighting Lifts and EN 81-6: Evacuation Lifts have adopted the British approach for emergency egress in multistory buildings. Given this international experience, it was considered reasonable to use the vertical transportation system for evacuation of building occupants in the event of fire, provided the building architecture, lifts, mechanical services, fire safety and electrical systems were correctly designed, installed, commissioned, maintained and managed. The zoned evacuation strategy, utilising the vertical transportation system at Eureka Place Tower, required the development of an alternative solution to the prescriptive (deemed to satisfy) provisions for approval by the Australian Authorities having jurisdiction. The adopted strategy required liaison between the design team and local Authority for identification of risks that could lead to the failure of the lifts. Once identified, systems were put in place to mitigate the risk to satisfy the life safety of the regulations. The following hazards associated with the vertical transportation system were identified: The lift shafts which connect all levels presented a major path for fire and smoke spread The piston effect generated by the movement of the lifts may increase smoke spread Lifts may be called to the floor of fire origin due to adverse effects on controls due to fire
Lift doors may not close if opened on the fire floor, due to smoke interfering with closure mechanisms; door distortion due to the heat of the fire; or pressure differentials at lift doors The potential effects of water from issuing fire hose steams or sprinkler discharge on electrical lift equipment Loss of power to the lifts Lift over loading in panic situations VERTICAL TRANSPORTATION & EGRESS SAFETY General The strategy implemented for ensuring safety of occupants combined the use of safe havens, innovative smoke control systems and sophisticated fire detection, alarm and communication systems. Smoke spread and heat damage must be limited to the fire floor by fast response sprinklers and compartmentation. The population must be able to leave the fire affected area to a place of safety and fire fighting personnel must be able to operate safely and efficiently. The vertical transportation system at Eureka Place Tower was protected against smoke and water, as follows: Lift and stairway shafts were air pressurised Lift lobbies were enclosed in smoke resistant construction and pressurised via lift shaft and stair pressurisation leakage Lobbies were protected by intelligent smoke detectors and floor sprinkler flow switches interfaced with lift control for recall in the event of smoke or water flow Lifts used for staged occupant evacuation were located in separate shafts from those located in the Evacuation Zone of fire origin and as such not subject to water damage Sump pumps were located in lift over run pits to drain water at the bottom of lift shafts
Lifts were capable of being operated from an emergency power generator Smoke Resistant Lift Lobbies The provision of smoke resistant lift lobbies mitigate smoke spread via lift shafts which connect multiple compartments. Reducing the fire and smoke hazard allows occupants on floors remote from the fire to stay in place. The lobby also provides a safe haven for occupants and fire fighting personnel using lifts during the evacuation of the fire floor. The lobby needs to be of sufficient size to accommodate all people who may use the lifts in a fire emergency with the doors closed to prevent smoke. According to Australian Building Codes, horizontal exits for commercial buildings must have a clear area of not less than 0.5 m 2 per person to accommodate the total number of persons from both parts of the storey. Hence 0.5 m 2 per person was used at Eureka Tower in the calculation for the lobby & transfer area. The lobby also needs to resist the spread of smoke and fire from the floor or lift shaft to maintain tenable conditions for the time required for evacuation or fire fighting search and rescue. Given Eureka Place Tower is fully sprinkler protected, the lobbies were designed to withstand a temperature of 200 C, which was considered appropriate for a smoldering or shielded sprinkler fire. The smoke lobbies at Eureka Tower generally comprised the bounding wall construction of apartments complete with self closing 38mm solid core doors fitted with medium temperature smoke seals. Air Pressurization Systems The effectiveness of a smoke lobby to provide a tenable environment can be enhanced by the use of air pressurisation systems. It is important that smoke does not spread into the lift shafts via the lobby because the piston effect of elevators can distribute smoke throughout the
building. Spurious alarms caused by smoke spread may also cause the building pressurisation systems to operate in other adverse modes. Each fire isolated stairway, lift shaft and Transfer Level at Eureka Tower were provided with an air pressurisation system, with lobbies pressurised via leakage. All systems activated simultaneously upon receipt of any general fire alarm in the building for simplicity. The system minimised smoke intrusion by pressurisation with outside air. The system was carefully designed to ensure that positive pressures are maintained and that stack effect, piston effect wind and excessive pressure did not interfere with the door operation. Suitably sized pressure relief was provided in the lift lobbies on all levels to address these issues. Detailed fluid dynamic calculations and modeling were carried out determine pressure and flow throughout out the building for air balancing. Intelligent Smoke Detection & Alarm Systems Information is critical during a fire emergency. Data from equipment such as detectors, remote field devices and television or security cameras in lobbies would be a valuable additional source of information to be used in a fire emergency. Analogue addressable smoke detection technology was used in Eureka Tower to quickly locate the fire and transmit coded signals to various building automation system for phased evacuation. High sensitivity smoke detectors were located below ceiling in all public spaces and lift lobbies. Computer programs set priorities and determine which floors should evacuate using the lifts and which floors remain in place. Lift control panels send elevators to the appropriate floor and recall to home in the event smoke is detected in a lift lobby. Occupant evacuation within the Evacuation Zone is intended to be cascading subject to the severity of the fire incident.
Upon fire alarm, it is proposed to evacuate the Floor of Fire Origin (FFO) in the first instance, with the subsequent evacuation of occupants on the floors above and below depending on smoke detection or Fire Brigade intervention. Informative voice alert and evacuation information to building occupants is communicated automatically by the building Emergency Warning And Intercommunication System. The strategy at Eureka Tower is proposed to be managed by responsible fire wardens on each floor; or an Emergency Response Team consisting of security staff, office and retail staff; thus the importance of implementing and maintaining detailed emergency procedures. A fire control room is provided for the exclusive purpose of directing emergency operations. Hard wired emergency phones or Fire Brigade Intercom points are proposed in lift lobbies, elevator cars and transfer levels to communicate between those using the elevator evacuation system and the fire control room. Commissioning, Testing & Maintenance The use of lifts in a fire requires a large number of systems and components to work together. Such systems are inherently unreliable and require periodic routine inspection, testing and maintenance. It is strongly recommended that an overall fire safety system approach is adopted for testing rather than individual components. The performance based design approach relies on the integration between various sub systems; therefore each interface and effect should be tested and maintained for correct operation. TRANSFER LEVELS General Open space public areas such as sky lobbies, observation lounges and panorama decks may be used as transfer levels where people assemble until an emergency is over or be evacuated via the lifts servicing the level.
The following levels were nominated as Transfer Levels at Eureka Tower for the evacuation of building occupants : Level 52 (minimum Occupant Area of 455m 2 ) Level 24 (minimum Occupant Area - lobby/corridor) The transfer levels were fire separated from the remainder of the building and serviced with essential services equipment. The construction materials and contents within the transfer levels were selected with consideration to smoke developed and flame spread indices; and consistent with those nominated within regulations for public corridors leading to a fire rated exit. The minimum Occupant Area was determined with consideration to a maximum four levels evacuating at any point in time. This philosophy is consistent with a cascading Emergency Warning System as detailed within Australian Standard AS 2220, which provides warning to the fire level, two levels above and one level below. Transfer Level Area The required Transfer Level area at Eureka Tower was calculated using an inflow and outflow methodology. Project specific first principle evacuation spreadsheets were developed for the calculation of the occupant inflow. These were based on studies by Proulx, Nelson, MacLennan and Pauls. Occupant outflow from the Transfer levels was calculated from data obtained from the ELVAC computational model by Klote et al.
NON - FIRE EMERGENCY EVACUATION The evacuation strategy adopted for the Eureka Tower also caters for non-fire related emergencies. The fact that the evacuation zones may be evacuated independently without relying on common equipment, is one of the primary design initiatives adopted which adds to the versatility of the evacuation system. Other design initiatives which were adopted removed the critical single points of failure, which included: Distributed exit stairways which traverse the entire building and discharge at ground level. Distributed lift banks with independent lift motor rooms. Generator or battery back-up power located on a separate floor to the building sub-station for essential fire & life safety services including lifts. Distributed fire detection and alarm system with return path of communication loop cabling located with separate services rated shafts. Networked Fire Indicator and Master Evacuation Control panels located in separate zones where each panel can maintain status and control of its own dedicated circuits and control activity at other locations should a panel fail. Ringed gravity fed fire services water supply, complete with fire brigade booster facilities. The evacuation of the building during non-fire related emergencies requires the building structure to remain in place for the time required to safely evacuate the building. CONCLUSION Tall buildings represent man s very nature to continue to reach for the heavens, creating lasting monuments to their own ingenuity and courage. Performance-Based Codes and Fire Safety Design Methods provide the vehicle in delivering these monuments that we can all be proud of.
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