Fire Engineering Solution Review - Assignment Example

FIRE ENGINEERING SOLUTION AND CALCULATIONS Name Course Professor Date PART A Requirements of Part B4 One of the principal duties of any government is to guarantee the security and safety of occupants within buildings in the event of a fire outbreak. The British has done so by establishing an array of standardized regulations building regulations that must be adhered to by all architects and engineers. Some of these are covered in the Approved Document (ADB) B 2013. One of the most important things that the document covers is the prevention of fire spreading from one building to another. The building standards associated with it are mentioned in Part 4 of the ADB. This section focuses on the requirements that those who come up with building plans should follow to provide sufficient protection against external fire spread. Fig 1: Requirements of B4 On most occasions, there exists some distance separating one building from the neighboring ones. This means that fire from one can spread over this open space and reach the next one, fueled by draft. It is therefore necessary for the designers to account for this space and prevent such an unfortunate thing from taking place. This is therefore covered in the regulations under the provisions for space separation between buildings. It is upon the designer to estimate how far the external walls of their buildings should be set from the relevant boundary. According to the regulations, this is dependent on the size of the building, the types of roofing materials used, and the what it will be used for such as an office block, residential apartment, or industrial complex. Fire can easily move from one building to the next through the roofs. That is why one of the very first things that the regulations provide for is the kind of materials that should be used. These majorly depend on how high the building will rise as the higher as the risk of fire spreads decreases with height. The appropriate types of roof coverings are also dependent on the roof area as well as the distance from the relevant boundary. They are selected in accordance with BS EN 13501-5:2005 which specify the performance and effectiveness of different materials in prevention of fire spreads over any given type of building. Another thing that significantly affects the effectiveness of buildings in preventing external fire spread is the fire duration of its external walls. This is the amount of time the walls can be exposed to fire before the flames can pass through them (HM Government, 2008). The walls have to be constructed with regard to different regulations including that on the allowable percentage of combustible materials within them, barriers for cavities, insulating materials. Both European and British rating classes are provided in the document and hence the engineers have the option of selecting the most suitable ones with respect to BS 8414-2:2005 or BS 8414-1:2002. Fig 2: Provision on construction of external walls Due to financial or design restrictions, not all parts of a building may be constructed using materials that offer the highest level of protection against external fire spreads. The regulations define the allowable unprotected area (UPA) between one building and the rest based on BS 5588-5:2004, among other standards. This is the maximum area from the building that can be safely left unprotected without the risk of exte5rnal fire spread. The UPA can be arithmetically determined using a number of techniques. It is governed by several parameters including the size of compartments within the building, the external wall materials, and the distance from the relevant boundary. The presence and extent of a fire suppression system such as sprinklers also determines the allowable UPAs for different buildings. Review of Standard Guidance for England and Wales Standardization is an essential thing in building sciences. The fire safety regulations have been harmonized for England and Wales to enhance their applicability and ease of use in both territories. This document consists of 10 interrelated parts that should be followed for a building to be deemed safe against fire spreads. This is intentionally so since some of the things that are mentioned within it are where the space considerations have to be made; the details on site boundaries, and among others, the methods used in determining the space separation and UPA (Read, 1991). In order to gather more insight into these regulations, this section focuses on breaking them down. Space Separation Considerations As mentioned earlier, the space separating buildings has a huge bearing on how secure they against external fire spread. This is the reason why considerations on how to go about it are prominently included in BR 187. One of the considerations that have to be made is how susceptible the building is to fire eruption. Laboratory buildings contain flammable substances and are therefore riskier than, say, office blocks (HM Government, 2010). Hence, the usage of the building must be factored in. Fig 3: Provisions on space separation The estimated number of occupants that will be within the building at any one time is also another major consideration. It is necessary for the designers to allocate enough space in addition to the internal escape routes that will allow for their safe escape from a burning building. The other factor that must never be ignored when establishing the space of separation is the provision of enough amenities for fire and rescue officers. Based on BS 9999, they need to have sufficient and easy access to all crucial areas of the building not only to save lives but also to salvage property and contain the fire. Boundaries The boundaries between buildings are more than just markers of how far the property might reach. According to BR 187 and the ADB, it is an essential factor when designing for fire safety(HM Government, 2013). Boundaries are those physical barriers like fences, hedges, and walls which separate one building from another. For buildings within the same site, no physical boundary might be built between them. ^The distance of external walls from a boundary is one of the most important factors that should be considered as stated in Section B4 of ADB 2013. This should be set such that there is no risk of fire spreading across neighboring buildings. Any building under consideration might border several others and hence several boundaries might be used in the space calculations. The ones used and those not used are referred to as the relevant and notional boundaries, respectively. Methods of Assessing Space Separation and UPA BS 9999 offers different techniques that designers can utilize in coming up with the most appropriate space separation distances and allowable UPA. The one that is chosen sorely depends on their effectiveness for a given situation and the preferences of the one doing the assessment. These techniques are mentioned in this section. (a) The Simple Geometry Method It is by far the easiest method to use if the building under consideration meets the conditions set in the regulations for its use. They should either be used as class 2 factories, residential buildings or office blocks. Furthermore, they must not exceed 9 m in height and the maximum distance from one end to the boundary needs to be 24 m. The UPA is obtained by multiplying the length of the building by six. Its simplicity and straight-forwardness makes it an ideal choice whenever possible. (b) The Protractor Method/ Method of aggregate notional areas The total effective unprotected area is determined by viewing them from specific points along the boundary line with the zones closer to the line considered as being more effective. By use of a protractor, the multiplication factor for each zone and its product with the actual area obtained. This is done in two steps by first locating the sides of the building where the UPA is to be located. The relevant UPAs are then identified and summed. (c) The Enclosed Rectangle/ Geometric Method It involves the use of geometric principles to do the analysis and is mainly used in situations where the external walls of the building under analysis are at least 1000 mm from the boundary If this distance is not provided, then it can be assumed. The analysis is done in the following manner: 1. The most appropriate plane of reference is identified. Ideally, it should be parallel to the boundary and not pass through within the building apart from projections such as balconies 2. Perpendicular lines are extended from the plane towards the proposed UPAs without their alignment exceeding 80 degrees. The projected areas are then enclosed by constructing a rectangle around them 3. The regulations come with tables listing the standard rectangle sizes f. An appropriate rectangle whose height and width are either equal or greater to those of the constructed one is then selected 4. The areas of the enclosing triangle alongside those of the protected and unprotected zones are calculated. The percentage UPA is obtained by expressing its area as a fraction of that of the rectangle 5. If the boundary distance is given, the allowable percentage UPA is obtained from the standard tables. This process is repeated for all sides of the building 6. For assumed distances, the obtained percentage UPA can be used to read the minimum allowable distance from tables. This gives the exact location of the boundary. A buffer zone can be established if the plan is superimposed with the minimum distances. PART B Construction of the JB Firth building cannot commence until its blueprints meet the requirements spelt out in the fire regulation documents. The engineers, architects and other professionals involved in the formulation of the plan have to ensure that it as up to par with these regulations. One of the main things that therefore need to be done is determination of the maximum allowable unprotected areas. This is essential primarily due to the fact that it has a huge bearing on the spread of fire from this building to the neighboring ones. A complete analysis is done by considering four different scenarios with regard to the degree of compartmentation. The relevant calculations are therefore done using the enclosed rectangle method as follows. Scenario 1 From the plans, it has been shown that at this point the entire building and adjoining areas are not protected against external fire spread and hence the risk of fire is great. It therefore makes sense that the distance from the boundary has to be significant, and can be determined in the following manner: Design Width, Wd = 29 m Design Height, Hd = 14.6 m From tables for this type of office building, the closest rectangle to this one has the following dimensions: Tabular Width, Wt = 30 m Tabular Height, Ht = 15 m Therefore, area of enclosing rectangle, Ar= 30*15 = 450 m2 Using the dimensions of the different compartments, the total unprotected area, Au can be calculated as follows: Au = {(3.2*1.7) + (1.8*1.7*10) + (3.4*2*3) + (2*2.2*30)} = 188.4 m2 Expressing the total unprotected area as a percentage of the unprotected area yields: Au / Ar*100, % UPA = (188.4/450)*100 = 42 % This can be rounded up to 40%. Therefore, the minimum distance from the relevant boundary can be read from the tables on the corresponding column thereby giving rise to: Allowable UPA distance = 7.5 m The values used are those enclosed within brackets since the building will be partially used as an office block. Scenario 2 In this scenario, only the side of the JP Firth building that faces the Maudland consists of unprotected areas. The distance is therefore expected to be shorter than that one obtained in the first one given that the risk of fire spread has been lowered. Design Width, Wd = {3.4 + (2.2*10) + (0.22*10)} = 27.6 m Design Height, Hd = 2 m From tables for this type of office building, the closest rectangle to this one has the following dimensions: Tabular Width, Wt = 30 m Tabular Height, Ht = 3 m Therefore, area of enclosing rectangle, Ar= 30*3 = 90 m2 Using the dimensions of the different compartments, the total unprotected area, Au can be calculated as follows: Au = {(3.4*2 + (2.2*2*10)} = 50.8 m2 Expressing the total unprotected area as a percentage of the unprotected area yields: Au / Ar*100, % UPA = (50.8/90)*100 = 56.4 % This can be rounded up to 60%. Therefore, the minimum distance from the relevant boundary can be read from the tables on the corresponding column, hence giving rise to: Allowable UPA distance = 3 m Scenario 3 For the third scenario, it is quite clear that the entire building has not been secured against external fire spreads. This means that the distance from the boundary will be greater than that in the second scenario. The calculations are done as follows: Design Width, Wd = (3.4 + 22 + 2.2) = 27.6 m Design Height, Hd = {(2*4) + (1.5*3)} = 12.5 m From tables for this type of office building, the closest rectangle to this one has the following dimensions: Tabular Width, Wt = 30 m Tabular Height, Ht = 15 m Therefore, area of enclosing rectangle, Ar= 30*15 = 450 m2 Using the dimensions of the different compartments, the total unprotected area, Au can be calculated as follows: Au = {(3.2*1.7) + (1.8*1.7*10) + (3.4*2*3) + (2.2*2*30)} = 224.5 m2 Expressing the total unprotected area as a percentage of the unprotected area yields: Au / Ar*100, % UPA = (224.5/450)*100 = 49.9% This can be rounded down to 50%. Therefore, the minimum distance from the relevant boundary can be read from the tables on the corresponding column, hence giving rise to: Allowable UPA distance = 8.5 m Scenario 4 The engineers in charge of constructing this building are at liberty to choose how the various compartment are protected as long as they satisfy the regulations. In this scenario, they have decided to protect the compartments on two of the external walls but left the rest and most of the interior compartments unprotected. The distance from the boundary can therefore be determined in the following manner: Design Width, Wd = ( 22 + 2.2) = 24.2 m Design Height, Hd = {(2*3) + (1.5*2)} = 9 m From tables for this type of office building, the closest rectangle to this one has the following dimensions: Tabular Width, Wt = 27 m Tabular Height, Ht = 9 m Therefore, area of enclosing rectangle, Ar= 27*9 = 243 m2 Using the dimensions of the different compartments, the total unprotected area, Au can be calculated as follows: Au = (2.2*2*30)} = 132 m2 Expressing the total unprotected area as a percentage of the unprotected area yields: Au / Ar*100, % UPA = (132/243)*100 = 54 % This can be rounded down to 50%. Therefore, the minimum distance from the relevant boundary can be read from the tables on the corresponding column, hence giving rise to: Allowable UPA distance = 6 m This distance is reasonable given that from the calculations just over fifty percent of the building is to be unprotected. The relatively high protected area therefore offers a buffer zone which would offer significant protection against external fire spreads to or from the other neighboring buildings. Methods of Increasing the Allowable UPA On most occasions, it would make more economic sense to have the largest UPA possible. This is because when designing a structure such as the JB Firth Building, it is necessary to work within tight budgetary constraints and hence having a larger UPA is a cheaper alternative to constructing using expensive fireproof materials. However, this has to be done with regard to the regulations such that the UPA established does not compromise the safety of the building and its occupants. The designers and engineers therefore have to strike the right balance to minimize costs while guaranteeing adequate safety against external fire spread. This can be done in one or more of the methods mentioned in the forthcoming paragraphs. One major way of doing this is by increasing the number of compartments within the building. This is because the higher the number of compartments, the harder it would take for fire to spread across them either from or to the building. The designers can therefore identify which compartments can be split into smaller spaces without interfering with their effectiveness for the use they are designed for. The compartment walls can provide additional protection thereby allowing the creation of more unprotected areas. The engineers can even take more advantage of this method by letting the compartmentation walls run in one vertical plane. Doing so offers superior protection against fire spreads and hence the external UPA can be increased. The other technique that the designers can consider using is putting in place advanced fire detection and suppression systems within the building. The primary objective of doing so is provide an avenue through which occupants and authorities can be alerted of a fire outbreak. More important, however, is their effectiveness in preventing fire from escalating to unmanageable levels. If things such as powerful sprinklers are installed all over the building, then UPA in and around the building can be increased accordingly. These systems can be able to suppress fire and prevent it from spreading to the neighboring buildings and hence a bigger UPA would not be problematic. Finally, the engineers can create more UPA by constructing the roofs and external walls using materials with a higher fire duration rating. Whenever wall and roofing materials that can withstand fire for a longer period are accessible, they should be used. The walls would therefore offer better protection against fire moving through them into or out of the building. Likewise, the roof will withhold the fire within its confines when it erupts and will not allow flames to pass through it into the building. With these at hand, the engineers can have more freedom in terms of the UPA they set and would therefore increase it up to the permissible limits. This and the other techniques can be used in combination with one another to allow for variation in the pattern of the UPA. In doing so, the designer can meet the safety requirements without using too many resources. References HM Government (2008). BSI Standards Publication: Code of Practice for Fire Safety in the design, management and use of Buildings. HM Government (2010). The Building Regulations: Building and buildings, England and Wales HM Government (2013). The Building Regulations: Volume 2 of Approved Document B 2013 Read, RH (1991). Fire research Station: Building Research Establishment Report Read More