Engineering Design Practice: Fire Resistance Testing - Assignment Example

PART A – Answer all 5 questions – total marks for this section is 50%.Include appropriate references. 1. What is fire resistance testing? (10 marks) Fire resistance testing is the type of testing that are done are done on structural materials and assemblies so as to establish fire rating with customary units being adopted as the primary units of measurement. In countries like USA these tests are done in conformation to ASTME 119 (ASTM, 2000). The year 1917 was when ASTME was first published as a tentative standard ASTM C 19 with its first adoption as ASTME 1933 being in 1933 (AISC, 2001). From the time the test method was introduced, it has undergone modification and updates but with no change has been done on its essential character. In the test methods for ASTME 119 there is a prescription of a standard fire exposure where the test results of building construction assemblies are compared (ASTM, 2000). With regards to testing floors and roofs it involves structurally loading a test assembly followed by the application of the standard fire exposure at the underside of the specimen. Then there is evaluation of the assembly on its ability of containing of the fire putting a limit to the level of flame spread and the heating of the unexposed surface with the applied load being applied. A rating is then given to the assembly, which is given in hours on the basis of the conditions of acceptance. In USA conducting standard fire test involving floor assemblies under restrained conditions is customary. 2. What is reaction to fire testing? (10 marks) Reaction to fire involves measuring of the contribution a material or an assembly of materials in the development and spreading of fire especially at the early stages of the fire when the process of evacuation is considered crucial. Some of the terms associated with reaction to fire include flammability, SFI, SBI, ignitability, surface spread of flame and classification. What a product contributes to a developing fire with regards to ease of ignition, energy production, the level of energy production and the spread of flame has an impact on the level of challenge that will be met by t\people escaping from the area under fire. In some circumstances reaction to fire testing is one of the requirements for complying with Building Regulations. Foe England and Wales it is addressed in Approved Document B , in Scotland we have this being addressed in Technical Handbooks Domestic and Non-Domestic; Technical Booklet E is used in Northern Ireland while for Republic of Ireland what is used is Technical Guidance Document B. Products which are to be used in railway applications whose production conform to DD CEN TS 45545 standard will require reaction to fire testing. Even in where the building regulations find fire testing not necessary , it may be the request of an insurer or other authority of a building to have an enhanced reaction to fire performance where testing may be necessary. Some companies involved in manufacturing products undertake reaction to fire testing as a way of having more information about the manufactured products or to place them in a position of being able to demonstrate how superior their products are in comparison to competing products. 3. Discuss the term “flammability limits”. Discuss the effects of temperature on flammability limits. Include diagrams. Flammability limits also referred to as explosive limits gives the lower and upper fuel concentration where the mixture consisting of dispersed combustible materials will burn where the limits are determined experimentally. Combustion may exhibit a varied violence level ranging from deflagration, detonation to explosion. The lower and upper limits are affected by the temperature and pressure, and usually will be expressed as percentage volume at 25 °C and the atmospheric pressure( Yaws et la, 2001).. These limits are useful in the production and optimization of explosion or combustion like in the internal combustion engines or it may be in the case of prevention of occurrence of combustion like in the case of uncontrolled explosions of combustible gas or dust build-ups. With regards to internal combustion engines it is important to the best combustible or explosive mixture of air and fuel and this mixture is referred to as stoichiometric proportion. Lower explosive limit (LEL) is the lowest concentration of gas in air that is able to produce a flash of fire if there is an ignition source. Sometimes LEL is used interchangeably by Lower flammable limit (LFL). Upper explosive limit (UEL) is the highest concentration of gas in the air that will allow production of a flash of fire if an ignition source is present and where the concentration is beyond the UEL the mixture will be too rich to burn. Temperature and pressure and the level of oxygen (oxidizer) present have influence on the flammability limits. High temperature, high pressure and higher oxygen supply of oxygen lowers the LFL while making the UFL to be higher thus making it easy for the mixture to explode (NFPA 101, 2009). At pressure level below 10 millibar pressure is found to have a negligible effect and its prediction is very unpredictable. (10 marks) 4. Discuss heat release rate in relation to fire hazards. (10 marks) The general development of fires as can be seen from figure 1 where the predicted temperature and CO2 levels occurring in the upper layer of the room has been given. Even though there was a possibility of choosing other gas species to serve as indicators of level of toxicity, CO2 is seen to be the best the best representative of the curves exhibited by the other gases. With change in heat release rate, there is a much far reaching effect in comparison to the effect brought about by changing ignition time. When the results from the four scenarios are compared, it becomes apparent that from predicted time to death is that through change of HRR has the greatest effect of the space tenability where the time to death is reduced from being over 600s to almost equal to the time to incapacitation of all the rest of the scenarios (NIST, 2005). Figure 1 5. Discuss the factors which will influence the fire development and the rate of fire growth within a compartment. (10 marks) Factors affecting Fire Growth and Development With fire being seen as a very complex phenomenon it makes it very difficult to make assessment of the main factors affecting the growth of fire and the interaction of the factors in a real fire scenario. There has been a lot of research that has been undertaken world over attempting to assess the effect that a variety of factors have on pre-flashover and post-flashover fire with the aim of determining rates of fire growth and severity of the fire in the long run. Fuel supply: controlling the supply level of fuel has been used in reduction of fire growth and the ability of the fire to spread. And it has received recognition in building regulations and code practice and other building regulations. When it comes to assessment of the fire growth rates and subsequent destructive potential, the physical and thermal characteristics of the fuel load play a major role. The heat release rate (HRR), the thermal capacity the combustibles and non-combustibles inside the fire enclosure, the radioactive, convective and conductive coefficients are important in determination of whether growth of fire would proceed to flashover. The Ventilation Factor and Burning Regime: Apart from adequate fuel supply being important in fire growth, the growth of fire can only advance if there is enough supply of oxygen. There is consumption of the air in the compartment with the growth of fire, and if more oxygen is not let into the compartment then the fire will be extinguished. Most compartments have been found to have sufficient level of oxygen entry through windows and doors that is able to ensured smouldering combustion is sustained. Fire Location and Room Geometry:Fire equations clearly have indicated that the growth of fire will be affected by the room size and shape as well as the openings. The fire will grow up to a point it will reach the ceiling level at which point it will spread under the ceiling. The flame’s horizontal length under the ceiling would be up to five times higher than the height of the flame where ceiling confinement is absent. This brings about increased temperature in the smoke layer, and this rapidly results to having increased level in downward radiation and subsequent level of fire spread. The original location of the fire inside the compartment is also important, this being attributable to effects cooling through entrainment of air into the fire plume. Fire located in the centre of a room will have the level of entrainment being double that of fire located near the wall and will be four times when compared to fire located at the room corner. PART B – Answer ALL questions – total marks for this section is 50%. Use Approved Document B to answer the following questions. Include appropriate references. 1) What are the 5 functional requirements of Approved Document B? (5 marks) a) To provide warning and means of escape b) To address internal fire spread by provision of appropriate lining materials c) To give detailed information on structural requirements to address internal fire spread d) Addressing external fire spread e) Address the issue of accessibility and the facilities required by the fire service 2) Give a definition for the terms means of escape from fire. Outline the main requirements of a safe means of escape from a building. (4 marks) This is the provision of emergence egress from areas of fire to areas which are safe. It is required that the stairs be in a construction of 30 minutes fire resistance. Also the structural frames, columns, load-bearing walls columns and floors are expected to have a fire resistance of 60 minutes. There is need to provide fire resisting structure so as to minimize the risk posed to the occupants some of whom like the disabled may have to remain in the building for longer as the evacuation process continues. This will also be away of reducing danger to those people who are in the neighbourhood of the building and may suffer from the falling debris or as a consequence of the collapsing structure on the neighbouring building. The fire fighters will also be in a reduced danger while in their rescue or search The headroom in the escape routes are expected to be not less than 2m with no projection being below this height with the exception of the door frames. The floors of all the escape routes are supposed to be chosen in a way that will ensure that there is minimization of slipperiness in wet conditions. According to Approved Document B the dimensions and location of the final exit should be in such a way that there is quick evacuation of people from the building. 3) What is the maximum recommended compartment size for each of the following cases: a) A single storey shop with sprinkler protection No limit b) A single storey industrial unit (1 mark) No limit 4) What is the maximum size of an opening (unprotected area) that can be discounted when considering space separation between buildings? 2000mm (1 mark) 5) In each of the following cases state whether a fire fighting shaft is recommended and if so whether or not a fire fighting lift is also required: a) An office building with a top occupied floor of 250m2 located at 19m above fire service vehicle access level Fire fighting shaft and fire fighting lift both required b) A four storey assembly building with a top storey of 1400m2 located 10m above fire service vehicle access level. (1 mark) Fire fighting shaft required but fire fighting lift may not be necessary 6) What is the minimum recommended fire resistance periods for the following structures: a) A 35m high sprinkler protected residential building 60minutes b) A four storey shop with sprinkler protection (1 mark) 60 minutes 7) What purpose groups would be appropriate for the following premises? a) A students union building (e.g. 53°)-Assembly and Recreational b) A department store -Store c) A factory-Factory d) A swimming pool building-Recreational (2 marks) 8) According to Table 2 of ADB, what are the recommended travel distance limitations (single direction & more than one direction) for the following: Table 1 Use Alternative on the route of travel One alternative More than one alternative A normal hazard storage facility 25 45 A place of special fire hazard 9 18 The bedroom of an apartment 9 18 A lecture theatre with fixed seating in rows 15 32 Shop floor 18 45 Plant room that exits through the accommodation within a building 12 25 (3 marks) 9) According to Table 3 of ADB, what is the recommended minimum number of escape routes from a storey with: Number of people Escape routes a) 10 1 b) 200 2 c) 450 2 d) 650 3 (2 marks) 10) According to Table 4 of ADB, what is the minimum exit width required to accommodate: a) 219 people -1050mm b) 61 people -850mm c) 10 people - 750mm d) 500 people -2500mm (2 marks) 11) A building with four above ground floors is served by two escape stairs without lobby protection. Using Table 7 of ADB, what is the minimum width of the escape stairs if each floor accommodates: a) 75 persons Number of persons likely to be in escape stairs=75x4=300 From table the width of stairs = 1100mm b) 130 persons Number of persons to be in escape stairs = 130x4=520 From table the width of stairs = 1700mm (2 marks) 12) A building with five above ground floors is served by three escape stairs with lobby protection. Using Table 7 of ADB, what is the minimum width of the escape stairs if each floor accommodates: With protected lobby there is no discounting of stairs meaning that all three will be assumed to be available a) 155 persons Total number of people to simultaneously use the three stairs=155x5=775 Number of people for each of the three stairs =259 Therefore from table width of stairs required =1000mm b) 230 persons Total number of people to simultaneously use the three stairs=230x5=1150 Number of people for each of the three stairs =1150/3=384 Therefore from table width of stairs required =1200mm (2 marks) 13) Assuming 100 occupants from the ground floor accommodation also exit through the ground floor of the stair enclosures for Questions 11 and 12, how wide do the final exits need to be? (i.e. a merging flow – diagram 15 and associated equation). (4 marks) Using W= ((N/2.5)+(60S))/80 Where N is the number of exit users, S is width of stairs in m Previous Adjusted number S in (m) Exit width 300 400 1.1 1.33m 520 620 1.7 4.33m 775 875 1.0 5.13m 1550 1650 1.2 9.15m 14 According to Table C1, what floor space factors would be appropriate in the following areas? a) An office- 6.0 b) A bar-0.3 c) A shop-2.0 d) A students union (e.g. 53Degrees)-1.0 (2 marks) 15 For a square room, 40m by 40m, calculate the number of occupants using the floor space factors obtained in Question 14. In each case what is the minimum number of exits required and how wide should each exit be as a minimum. (4 marks) Area of room =40mx40m=1600m2 Type Space factor Number of occupants Exits Width of exit Office 6.0 1600/6=267 2 1335mm Bar 0.3 1600/0.3=5333 3 26665mm Shop 2.0 1600/2=800 3 4000mm Student un. 1.0 1600x1=1600 3 2000mm 16 What is meant by the following terms: a. Life safety This include all construction, protection and occupancy features that necessary in minimizing danger to life that may be as a result of effects of fire that may include toxic gases, smoke and heat. b. Property protection This are constructions, protection and occupancy features that are incorporated in the building to make sure there is no destruction of property. c. Fire resistance Is the ability of a material to prevent fire to spread to other compartments d. Cavity barrier This is a barrier is in a concealed space and happen to coincide with the compartment wall or wall and has a function of providing same level of fire performance as the wall floor (4 marks) 17 Figure 1 and Figure 1a below represents a two storey office building, from the dimensions give an estimate for internal room sizes. With reference to Figures 1 and 1a determine: a. Travel distances from each room and each floor Travel distance for each of the floor =Length of building/2=25/2=12.5 The biggest room has a length of approximately 10m with the width being 5m and the door is at centre of the length. The travel distance is given by Travel distance =  The medium room is 4mx5m with door placed centrally at the 4m width along the corridor Travel distance =  The smallest room is 3mx5m the door placed centrally in the 3m side along the corridor Travel distance =  b. Occupancy load Area per floor=10x25=250m2 Total area =250x2=500m2 Occupancy load=500/6=83 c. Purpose group Office space d. Exit and final exit widths Exit width=750mm Final exit width w W= ((N/2.5)+(60S))/80 = ((42/2.5)+(60S))/5=0.77m e. Stair widths and Stairs width=1000mm f. Classification of wall and ceiling linings Wall material and ceiling to be used is class 3 (D-s3,d2) (10 marks) References American Institute of Steel Construction (AISC) (2001). Manual of Steel Construction: Load and Resistance Factor Design, 3rd Edition,Chicago, Il. ASTM (2000). “Standard Test Methods for Fire Tests of Building Construction and Materials,” ASTM E 119-00, ASTM International, Conshohocken, Pa. Beitel, J, and Iwankiw, N. (2002). “Analysis of Needs and Existing Capabilities for Full-Scale Fire Resistance Testing,” NIST GCR 02-843, National Institute of Standards and Technology, Gaithersburg, Md. Yaws, et la(2001). William; Matheson Gas Data Book Published by McGraw-Hill Professional, NIST (2005). Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report on the Collapse of the World Trade Center Towers. NIST NCSTAR NFPA 101 (2009)Life, National Fire Protection Association, Safety Code 2009 edition Lathrop, James K (1991). Life Safety Code Handbook, National Fire Protection Association,. Ed. NFPA Read More