Internal Fire Spread - Report Example

FV3201 Group Project Name Lecturer Course Date Table of Contents Introduction 3 Internal Fire Spread (Structure) 3 External Fire Spread 9 List of tables Table 1: Specific provisions of test for fire resistance of elements of structure 5 Table 2: Notional boundaries for Student Hub 10 Table 3: space between the two separate UPA’s 11 Table 4: Minimum designation of roof coverings for student hub 11 List of figures Figure 1: Compartment walls and compartment floors 6 Figure 2: Full provisions for cavity barriers 7 Figure 3: fire resistance period 8 Figure 4: height of floor 9 Figure 5: Separation spaces between buildings 10 Introduction There are standards that have been established to regulate various issues regarding fire safety. This includes Internal and external Fire Spread systems that are crucial in defining fire threat, reduce vulnerabilities and control risk. This requires a design of buildings to have provisions for means of escape, to have easy access to the building, evacuation strategy, consider risk profile of occupants, the escape or evacuation of occupants of different status. In Student Hub Building, gas leakage, an electric fault or even the static current can induce fire, which can result into deadly explosions. Internal Fire Spread (Structure) The interior structures of a building should have the capacity to withstand fire and hot gases for a reasonable period of time to enable occupants have time to escape as well as reduce the risk of fire fighting personnel inability to access the building. The ability of the building to maintain stability for a reasonable time provides an opportunity for individuals in and out of the building escaping. This is done by the use of materials that are fire resistance that is materials that have the ability to tolerate fire and hot gasses by not collapsing, allowing fire penetration or not allowing the transfer of excessive heat to other services. This work can only be done during the design period. Approved Document B, provides guidelines on how the spread of fire can be restricted that is by subdividing the building into fire resisting compartments. This is important as it ensures there is no massive spread of fire within a short period in a building. The sub- division of the building will depend on a number of factors which include; the height of the floor, availability of fire fighting equipments and fire load used. The recommendation provided in ADB states that when subdivision of the building into fire resisting compartments, the following is taken into consideration. Reduction of unprotected areas in the building. Provision of horizontal evacuation within the building. Provision of the space between buildings The compartment size limit should be limited. In compartisation of the building continuity should be maintained in terms of materials that are fire resisting. Any sections that have openings or closings should also be made of materials that resist fire. This will ensure that fire does not spread quickly from one compartment to another. During design period, adequate routes should be provided for which include; lifts, stairs, corridors, and the space between compartment. The table below provides load bearing capacity, integrity and insulation as provided by British Standard 476 in minutes. In fire safety strategy areas such as stairwells, lift, and lobbies are considered strategic locations where air pressure should be maintained at a level in excess of that of surrounding accommodation zones. Part of the building Maximum provision when tested to the relevant part of BS 476 in minutes Loadbearing capacity Integrity Insulation 1) Structural frame , beam and column 60 N/A N/A 2) Loadbearing wall 60 N/A N/A 3) Floors 60 60 60 4) Roofs *Escape routes parts. 30 30 30 *Roof perform the function of the floor 60 60 60 5) External walls *For any part less than 1000 mm from any point in the relevant boundary. 60 60 60 6) *For any point equal or more than 1000 mm. 60 60 15 7) Compartment walls 60 60 60 8) Protected shaft *Glazed fire fighter shaft. N/A 30 N/A *Any part between the shaft and any protected lobby/corridor. 30 30 30 *Any part not mention in the previous sections. 60 60 60 9) Enclosure *Protected stairways, lift shaft, lobby and corridor. 30 30 30 10) Fire-fighter shafts 120 120 120 *For separating fire-fighter shaft . 60 60 60 *For separating fire-fighter stair, lift shaft and lobby. 60 60 60 11) Sub-division of corridor 30 30 30 12) Fire resisting construction *Spaces of special hazards. 30 30 30 *Between store room. 30 30 30 13) Fire doors 14) Cavity barriers N/A 30 15 15) Duct N/A 30 N/A 16) Flu walls N/A 30 N/A Table 1: Specific provisions of test for fire resistance of elements of structure From the table above it can be noted that the recommendation for Student Hub Building is as follows: 60 minutes of fire resistance structure in lecture halls and in all protected stair ways which include stair 2, 3, 4 and 5. The structure in the kitchen should have the ability to resist fire for 30 minutes after its outbreak. All escape routes should have the ability to withstand 30 minutes of loading capacity integrity and insulation. The first stair which is more than 100mm should withstand 60minutes of loading capacity and integrity, 15minutes of insulation. In order for walls and floors to have insulation, ADB recommends that during design fire resisting materials should be included to get a barrier between compartments. The compartments needs to be divided into long and thin corridors in order to provide for fresh air into the windows of each as well as create natural air conditioning that does not require too much electrical dependence. The corridors would also mean more entry and exit points for occupants to make it convenient to walk to and fro as well as provide the practical advantage of providing access to the students in the event of fire and the like. It recommends that walls should be constructed in a manner that it runs through the floor of another storey. This ensures that there is insulation among the floors. If there is a suspended ceiling, there should be a fire resisting material which will ensure that the suspended ceiling is not connected with the upper floors. All openings including stairways and lifts within the building should have the capacity to withstand fire for a period of 60minutes. However, it should be noted that stairways and lifts should e made with materials that are incombustible so that fire does not affect them like any other wall. During the construction the material used and spaces provided should satisfy fire resistance criteria and ventilation procedure. The diagrams below shows protected shafts and compartment floors. Figure 1: Compartment walls and compartment floors Student Hub Building will have different compartmentation because of many services that it will provide. To begin with the kitchen will have different compartmentation safety level. Pipes transporting combustibles will installed away from the stairways, lifts, corridors or escape routes. Such pipes should comply with Pipelines Regulation1996 (CLG,2006) that is having maximum diameter of 160 mm and a melting point more than 800 ◦C thus non-combustible material. As shown in figure 2 below, there should be cavity barriers to prevent the spread of fire and smoke through cavities. There will be no cavities barriers between external walls. However the cavity barriers will be required in: At the edge of cavities to close them off. At the junction between external cavity walls. On protected escape routes in the position above and below fire-resisting construction. Above fire doors. Within raised floor spaces. Figure 2: Full provisions for cavity barriers According to ADB section 10 and BS 5588: part 9, fire doors, fire seals and fire stopping should be provided in all penetration through protected separating fire resisting elements. Aside from creating an environment that would lessen the chance of fire outbreak, additional features are needed in the Student Hub Building. The fire doors should be made of materials that can resist fire for 60 minutes as walls of compartments. This will be in line with fireproof construction requirements in BS which provides that the structural elements should be of incombustible materials with fire resistance ratings sufficient to withstand the fire severity resulting from the complete combustion of the contents and finish involved in the intended occupancy. . The materials that will be used in the construction should have the ability to resist fire for more than 120minutes because of the height of the building. This is shown in the table below; Figure 3: fire resistance period The building should be installed with sprinklers because of its size. External Fire Spread The external walls of Student Hub Building should have less than 60 minute’s loadbearing capacity, 60 minutes integrity and 15 minutes insulation of fire resistance. According to BS746-6 there are exceptions are allowed where the section forms part of an unprotected area. The stairs for both a building with multiple stairs should be protected with a vent of 1m2 at the dead end of the stairs. Its surfaces should be constructed to meet National Class Index l (BS746-6) to a height of 10m. Typical materials would be treated combustible materials or any totally inorganic material such as concrete or steel. The materials used for construction should be environmentally friendly emitting minimum carbon and dust into the air. Dust from construction sites and construction materials can be reduced by the use of spray water with a principle aim of reducing air and water pollution in the construction area. The walls should be painted with paints that reduce chances of catching fire. The ceiling should be suspended to reduce the chances of catching fire this can contribute to the overall fire resistance of a floor and ceiling assembly. No provisions National Class Index I or European Class C-s3, d2 Figure 4: height of floor The boundaries on the North, South and West Side provide little concern; the economics building on the East side of the building presents the largest risk. The architect has informed that 100% UPA is desired on the East elevation. The worst case scenario is on the ground floor where there is a solid glazed surface over this space, whereas the outer parts are recessed on the upper storeys. The desired glazed area will be approximately 13.5 from the economics building and 10.2m from the notional boundary. Based on the desired 100% UPA an enclosing rectangle of 21m (w) by 12m (height) is assumed in accordance with BRE report 187. The notional boundaries from the new building are shown in Table 4; please note that a sprinkler installation will allow double UPA areas or the notional boundary to be halved as shown below. Figure 5: Separation spaces between buildings Width Height No Sprinklers Sprinklers UPA (%) Boundary (m) UPA (%) Boundary (m) 21 12 100 10.5 100 5.25 21 12 90 10 100 5 21 12 80 9 80 4.5 21 12 70 8.5 70 4.25 21 12 60 7.5 60 3.75 21 12 50 6.5 50 3.25 Table 2: Notional boundaries for Student Hub From the table above it can be noted that a boundary of 10.5m should be provided allow 100% UPA which is greater than the available space of 10.2m. It is shown that without a sprinkler installation only 90% UPA would be permitted or the desired 100% would be allowed if sprinklers were installed within the building. An alternative method of meeting the relevant requirements that may be more suitable to the occupier is by protecting part of the glazed surface. There should be space between the two separate UPA’s for protection as the external lift poses highest risk in case of fire. Thus each area would have an enclosing rectangle of 9m (w) by 12m (h) and a separation space of 7m would be required for a UPA of 100%. Width Height No Sprinklers Sprinklers UPA (%) Boundary (m) UPA (%) Boundary (m) 9 12 100 7 100 3.5 Table 3: space between the two separate UPA’s We will also consider openings in the East elevation to reduce external fire spread. According to architectural plans there should be a separating space of ≈7.7m with a notional boundary of 3.3m from the economics building. This will create a boundary of 4.4m from economics building and the student hub. Based on two separate areas of 16m by 11.5m in height a maximum UPA of 34% is presented on each side of the void. In this regard, there would be provisions for roof coverings based on the distance to the (notional) boundary of 4.4m separating buildings and 10.2m from the intended glazing panels around the atrium space. Furthermore, the system would be built in such a way that it could be accessed without using pathways. The minimum designations for roof coverings are shown in Table 4. Resilient fire stopping must be provided to the underside of all roof coverings where compartment walls are provided. Boundary 4.4m – 6m (over plane face) AA, AB or AC Boundary 12m – 20m (recessed part) AD, BD or CD Table 4: Minimum designation of roof coverings for student hub The plastic rooflights of not exceed 5m² will be used to maximise daylight in the building. This will be installed at a minimum separation distance of 3m is required in any direction. Furthermore, the aesthetic appeal of hexagonal designs cannot be sidelined. If optimally designed, hexagonal shaped building ensures that the front width of all houses is determined by the length of the courtyard. Such a system would ensure uniformity and an appealing housing system thereby enhancing the creation of appealing forms of art. However, this issue can be addressed by enacting a hexagonal grid facing one direction. In this case, if the hexagonal grid is facing the south direction, all buildings would have a north exposure therefore ensuring adequate day time lighting for all buildings Read More