Chapter 2: Literature Review

The Literature Review chapter of this research primarily investigates the characteristics and effects of fire including the nature of fire (Ignition, Combustion, and Pyrolysis). Sources of fire hazards in high-rise buildings including the hazards presented by different materials such as textiles, plastics, wood and wood-based products and designs, gases and liquids will be discussed in detail in this section. Sources of oxidants, sources of heat energy i.e. mechanical heat energy, chemical heat energy, electrical heat energy, as well as the causes of fire in high-rise buildings will be identified and discussed in detail by the researcher. The effects of fire and fire products and human behaviour in fire emergencies will also be established by reviewing the available literature. Furthermore, different aspects of fire safety management systems in high-rise buildings such as preventive management, signage, pest control programs and housekeeping practices, inspection, precaution, and renovation, fire and evacuation, and emergency response management will also be studied. A brief description of the literature that will be studied in the dissertation is given below.

The issues of fire or other safety concerns for the residents of high-rise buildings is being discussed for over 100 years. However, this issue was addressed even more after the incident at the World Trade Center. Questions have been raised regarding the safety of occupants and their relation to building design as well as fire management strategies. Questions such as “how safe the residents of high-rise apartments are from the fire?” and “What are the fire safety measures/strategies in these buildings?” have become major concerns for building design professionals (Hall, 2001). The invention of secure emergency elevators and better developmental structures have made these high stories buildings possible. Usually, a building having six or more stories is considered in the category (Lougheed, 1997).

Fire Risk and High Rise Buildings

Risk is usually defined as the probability of an incident in a given fixed situation or consequence. Here the risk can be stated as:

Risk= Consequences x Probability

Therefore, one can calculate the risk to life from fire by examining all the consequences of a fire happening events in all probable locations and buildings (Hall, 2001).In addition, the incidents of fire in high-rise buildings and their stats can also be directed from national fire protection reports of different countries available online. Some of the stats from the National Fire Protection Association (NFPA) are given below: (John R. Hall, 2013)

Table 1 Source: NFPA Report

The table above shows the figures for fire incidents in the past years with respective damages and casualties. The last column shows the percentage of high-rise buildings in which these fire incidents happens. This chart shows that risks and deaths through fire incidents are related to the height of the building where almost 10 % of the buildings in which these accidents happened were High-rise (Hall, 2013).

What Is Unique About Fire Safety for High-Rise Buildings?

From the above-mentioned figures, it is evident that fire incidents are responsible for hazardous effects both to the occupants as well as for the building itself. But the question arises that why the risk is perceived to be higher in high-rise buildings. This question can be answered through the following descriptions.

• Egress Systems: Whenever there is fire there is always a rush and crowd. In high–rise buildings there are more stories and consequently more people. So everyone rushes to the stairs in case of emergence resulting in crowding and slow movement. The stairs of course are quite long so the time is taken by the occupant to descend these stairs also increases the time of exposure to smoke. The lack of proper ventilation in the egress system is responsible for increasing life threats in these high-rise buildings. Therefore, it is necessary to provide a proper evacuation system in buildings (Soja & Wade, 2000)
• Fire Department Access: Even the modern firefighting techniques are quite improved but still most of the fire departments have equipment that can only reach the 6th or 7h floor of the building. Because of the height, the ladders cannot reach the top stories and the firefighters have to vertically enter the building and also have to face the evacuating crowd. This can result in delay and even more crowding before they reach the fire point. Also, they have to bring water hoses with them which is also a challenge in these high apartments. Therefore the proper design of the building is necessary for effective safety management in case of an emergency (Soja & Wade, 2000).
• The Forces of Nature: The impact of nature also affects increasing the danger of fire in high-rise buildings. In tall buildings, the stack is affected and the wind pressure increase. Both these factors are responsible for greater smoke movement and high flammability (MiaZmud, 2007). Therefore nature also contributes to increasing the fire danger in high buildings.
• Increased Density of Occupant and Fuel Load: As the number of stories increases in a building the density of materials and the population of residents also increase. Even if the fire barriers are placed horizontally the fire will move in an upward direction. This will in return result in adding more fuel and affecting a large number of occupants in the building
• Complex Vertical Utility Services: Usually the utility services in a building are arranged vertically and in the case of tall buildings there are long pipes of water and gas supplies running from one floor to another. These arrangements could cause problems as in the case of fire the damage in the lower part could affect all the above stories because they are interrelated (Clampet, 1997)
• Integrated Fire Problems: Now a day these high-rise buildings are not just only residential buildings. They are either situated in a shopping mall or other commercial residences. These occupancies will have their fire protection system or problems which may differ from the residential apartments. These could cause serious problems in case of fire. Therefore special engineering solutions will be required to solve this issue in these high-rise buildings (Anon., 2001)

For an architect or designer, all the above-mentioned features should be well understood and addressed so that the building they will make will be fire-safe. Today there exist codes that provide guides for building designers to solve these problems. The engineers need to understand these issues before designing a high-rise building and come up with sustainable and unique solutions for them. These are all the requirements needed for fire safety engineering (Demkin, 2003)

Developing and Revising Fire Safety Strategies in High-Rise Buildings

• Fire Safety in High-Rise Buildings

The increased incidents of fire in high-rise buildings forced the concrete and masonry industry to recognize and address this issue so that fire safety can be increased and property loss can be decreased (Anon., 2015). Keeping in mind the need for such a policy the Fire Safety Committee and Masonry Industry recommends some basic principles and guidelines for architects and designers. These principles guide in choosing an appropriate design and construction material for the building so that the individuals, as well as property, are safe from fire (Meacham, B.J., 2004). These principles are discussed below:

1. Building must remain intact throughout the fire and allows occupants to evacuate from the building.

The most important thing to consider while designing and developing a high-rise building is that in case of fire there must be no structural failure and the building should not be collapsed during the fire. This is because if the building collapsed it will not only endanger the lives of occupants and the fire rescuers but also can bring hazards to the people and buildings around (Tan, C. W, 2004). The floors and structural material should be tested according to the fire rating codes to determine their performance in fire. Their performance is tested in laboratories so there is always a doubt that how they will perform in an actual devastating situation. Usually, structural materials which have two hours or more fire rating are considered useful in varied fire situations. These codes help to develop criteria for performance and design for maximum safety of high-rise buildings (Soja & Wade, 2000).

2. Code regulations for high-rise buildings should be strictly directed towards fire safety and should be implemented properly.

Modern studies have claimed that the hazardous incidents in modern high buildings are a result of inappropriate use of construction material and building design that does not feature characteristics of stability in fire situations. These include the use of low-quality and combustible materials and unsafe building design such as inconvenient access to an exit, poor elevator controls and poor exhausting system in corridors or stairs. These factors can contribute to stack effects and can cause difficulties to both occupants and as well as for firefighters. These problems can only be controlled by strict implementation of building codes that are based on safety measures and considerations. it is also important that these codes should not be meant for reducing some risks and creating new ones.

3. There should be compartmentation, early fire detection and smoke control facilities on every story of a high-rise building.

Each story of the building should consist of compartmentation that encloses the floor, stairwell and elevator. It is suggested that each story should have two compartmentations so that the evacuation or rescue procedures can be done efficiently in case of fire. These compartments are made safe through fire-restricted barriers which are also responsible for smoke control. The openings should be equipped with self-closing doors and dampers etc. Smoke control devices should be installed in corridors and stairs to avoid suffocation. All these precautions are necessary to warn the occupants and ensure their safety from fire hazards.

4. Implementing restrictions on using combustible constructing elements and controlled use of insulation and finishes

The old constructed high buildings which were built according to old codes were safer than the modern building. The primary reason behind this is that modern construction involves the massive use of combustible material which results in greater flame and smoke as the result of accidental fire (Walke, 2008). However, this danger can be minimized by applying strict legal control over material use for construction including secondary building materials such as insulations and finishes. Practical criteria should be adopted in controlling the damage that occurs through fire and life threats from smoke and combustion. Government should take steps on a national level to ensure occupants' safety in these high-rise buildings (Tylor. Wood, 2011)

5. Fire suppressing systems (sprinkles) are necessary for hazardous areas or areas with high combustible material.

Modern building codes made these automatic fire suppressing systems compulsory for high-rise buildings. These fire safety equipment are in addition to other necessary fire safety measures and should be included in basic building design. These systems should be included to provide instant safety from any fire incident. However, these sprinklers cannot rely totally on fire extinguishers because they may not work in a heavy fire situation. These sprinkle systems can also help alert people ahead before the fire raises to a hazardous level (Lougheed, 1997).

6. In addition to compartmentation every story should have an automatic active fire-suppressing / protection systems

It was recommended that in stories where non-compartment areas exist automatic fire suppressing systems should be implanted. However, they should not be considered a permanent substitution for structural fire resistance or compartmentation. Compartmentation is necessary for the reliable security of occupants in these high-rise buildings (Bunker & R, 2002).

Primary Parameters and Codes of Practices

Different types of rules and regulations have been developed and regulated for protecting buildings from fire and smoke. These rules and approved codes of practices/regulations define procedures that help/facilitate the architects and building designers to build structures such as high-rise buildings in a much more protected way so that they could be safe from any disaster situation or even can avoid them from happening. The common codes or regulations practised in the world are:

• Approved Document-B: Fire Safety (B-1); Building Regulations (England and Wales)
• Fire safety/precautions in the design, structure and use of buildings: BS 5588
• The British Standard BS 5588 series of practices and codes
• Life Safety codes NFPA 101 (US)

Initially, the NFPA codes were used by architects all over the world but today they have a choice of using either NFPA codes or Local codes (B1). In designing high-rise buildings the following fire factors and behaviours are considered to successfully implement the fire protection system. These involve:

1. The Risk:  the risk of the fire can be estimated by taking into account the amount and kinds of combustible materials used in the construction of the building and furnishing it. It also involves the occupant’s characteristics such as body heat and energy. The energy and mass loss are also involved in these risk estimation calculations (ASCE, 1999). The energy release rate relations can be given as

2. The Growth Rate of Fire: The fire growth rate is determined by the maximum time it takes the occupants to reach a safe exit. After this, the time required for reaching the defined safe zone must be greater than the time which is estimated for the fire to reach the evacuation zone.

Time of Activation: this estimation involves the time required for the pre-activation process which is the time of detecting fire by the security system and the time involved in the starting of these emergency procedures.

3. Layout Design: The building design or layout ensures that all the above-mentioned factors are covered while designing the high-rise building. What kind of protection and evacuation system will be used in a building will be cleared at this stage.

4. Modelling of Fire Protection System: Fire resistance which is the ability of a building to withstand fire can play a major role in enhancing fire protection in high-rise buildings. These buildings are given different fire ratings or codes depending upon their resistance. These codes and ratings are given on the base of the building design and the covered area.  These buildings are also physically tested however the actual resistance to fire situation is always unpredictable. The severity of resistance can be determined by a man other factors which are not defined in building codes. The commonly used evacuation procedures in high-rise structures include the single-stage evacuation on fire alarm and/or the two-staged evacuation processes involving quick investigation in which a warning code is sent to employees and after confirmation, the fire alarm and sprinkles are activated.

The analysis necessary for numeric modelling: The following fire resistance analysis should be conducted:

• The fire development model helps to illustrate the fire or heat exposure.
• The thermal response model that demonstrates temperature rise in structural members.
• Structural response model that will illustrate the capacity of the exposed structure in carrying the load.

The escape designs hold significant importance and their objectives are categorized by keeping in view the building requirements and other concerned rules and regulations. Moreover, it is ascertained that the building must be designed and constructed by keeping appropriate provisions for the warning signs of fire. Apart from all this, a safe path must be constructed that routes toward an outside building and provides an escape path in case of fire from the building. The employees must be trained properly for following all these procedures without any outside assistance even in the case of an emergency or disaster.

Summary:

For the cases of high-rise bundling, much emphasis is also given to the means of evacuation in terms of the capacity of stairways (designed from equations/modelling), the implication of the phased evacuation approach (such as for wo floors evacuation to avoid panic, e.g. as per LDSA Fire Safety guide), exit widths, exit flows, travel distances and times, along with the consideration of the type of occupants residing the multistory high rise buildings. Details of the parameters and calculation models have not been included in this interim report (due to limitations of time/length), however, one complete case study of how to design active protection and safety system for a high-rise building will be included in the final submission of this paper.