UNIVERSITY OF KENT DARWIN FIELDS DEVELOPMENT ACADEMIC BUILDING FIRE STRATEGY STAGE D. HOARE LEA Consulting Engineers

Transcription

1 UNIVERSITY OF KENT DARWIN FIELDS DEVELOPMENT ACADEMIC BUILDING FIRE STRATEGY STAGE D HOARE LEA Consulting Engineers Glen House Tottenham Court Road London W1T 7PL Tel: Fax:

2 AUDIT SHEET REVISION DESCRIPTION DATE ISSUED BY REVIEWED BY 00 Preliminary draft for comment 01 Revised to incorporate comments LY/KL KL LY KL 02 Further amendments LY KL 03 Updated with Design Team comment LY KL 04 Further amendments LY MH 05 Revised with Design Team comments LY MH 06 Updated drawing LY CH This report is provided for the stated purposes and for the sole use of the named Client. It will be confidential to the Client and the client s professional advisers. Hoare Lea accepts responsibility to the Client alone that the report has been prepared with the skill, care and diligence of a competent engineer, but accepts no responsibility whatsoever to any parties other than the Client. Any such parties rely upon the report at their own risk. Neither the whole nor any part of the report nor reference to it may be included in any published document, circular or statement nor published in any way without Hoare Lea s written approval of the form and content in which it may appear. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 2

3 CONTENTS 1.0 INTRODUCTION 2.0 MEANS OF ESCAPE 3.0 INTERNAL SPREAD OF FIRE 4.0 EXTERNAL SPREAD OF FIRE 5.0 FIRE SERVICE ACCESS 6.0 CONCLUSIONS X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 3

4 1.0 INTRODUCTION The University of Kent Darwin Fields development consists of five Student Hall buildings, Enhanced Student accommodation and a new Academic Building on site. The University will have ownership of the Academic Building which will incorporate a Lecture Theatre, reception and exhibition areas and seminar rooms. This document will outline the fire safety requirements for the Academic Building only. Reference should be made to the full Fire Strategy report for the accommodation blocks which includes the analysis for the overall Darwin Fields development and Student Halls of residence; titled Fire strategy report for typical student residencies- Stage D. 1.1 Regulatory guidance As part of the University of Kent development the Academic building is required to comply with B1-B5 of Approved Document B: 2006 (AD-B) to the Building Regulations, or achieve the performance-based requirements through fire engineering solutions. Further reference is made to BS 5588 Part 6 for Places of Assembly. 1.2 Site description The Academic building sits on a sloped site, from South to North. The lecture theatre has escape at each storey i.e. Upper ground and First floor level. The Upper ground level will be the fire service access level as described in AD-B Section B5 and detailed more in section 5 of this report. A section through the lecture theatre from the latest GA plans dated (work in progress) is shown below: Figure 1 Section of lecture theatre Enhanced Accommodation on the North side of the building First floor Upper Ground At the North end of the building, there is a link to student accommodation (Enhanced Student Accommodation block) on both the Upper Ground and First Floor levels. Based on the two different purpose groups, a separate fire philosophy will be proposed for each use. A fire safety assessment of the academia areas for the current design layouts has been undertaken and is detailed in this report. The fire strategy for the Enhanced student accommodation is detailed in a separate report as mentioned above. The current overall site layout of the buildings has been indicatively shown in Figure 2. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 4

5 Figure 2 Darwin Fields Development Pavilion building Student Hall 6-8 Enhanced apartments Student Hall 1-2 Student Hall 3 Student Hall 4 Student Hall 5 Academic Building 2.0 MEANS OF WARNING AND ESCAPE The Academic building will be classified under the Assembly and recreation Purpose Group, following Table D1 of Approved Document B (AD-B). In the event of a fire in the Academic building occupants will follow a simultaneous evacuation procedure. It is proposed to maintain independent escape routes from the Academic building and the Enhanced Accommodation in the event of a fire in either area. 2.1 Fire Detection and Alarm System Under Approved Document B, there is no requirement to provide an automatic fire alarm system throughout the Academic building, however as the building will be linked to a residential building that is equipped with an L1 fire alarm system it is recommended that an L1 system be provided throughout the Academic building also, in accordance with BS 5839 Part 1. This system will be interlinked with the alarm system in the Enhanced Student accommodation. The fire alarm system with sounders should be located to provide an early warning of fire in the lecture theatre, seminar/breakout spaces, reception and any public spaces within the academic building. A back up power supply will be incorporated into the system. The fire detection and alarm apparatus should be tested on a weekly basis. It is the responsibility of the University Management to maintain the reliability and function of the integrated fire alarm and detection system. In order to accommodate for disabled occupants with impaired hearing, an alternative fire alarm warning system, or detailed management procedures shall be incorporated into the management policy as discussed with Building Control. In the event of a fire in the Academic building occupants would follow a simultaneous evacuation procedure immediately and a delay period should be programmed into the fire alarm system X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 5

6 which would initiate the fire alarm in the adjoining building, and vice versa in the event of a fire in the Enhanced Student Accommodation. The alarm for the academic building should be interlinked with the University management centre. 2.2 Means of escape Lecture theatre There are two exit doors to the outside at upper ground level as indicated in Figure 3 based on the GA drawings. These are the primary means of escape routes from the Lecture theatre. The Lecture theatre has a capacity of 500-persons based on advice from the Client. The first floor design has two alternative access routes out of the Lecture theatre; one of which leads occupants onto an external escape stair and a second escape route will be via the escape stair shared with the adjoining residential block (see Figure 4). Based on the GA drawings and the given exit widths at upper ground level it is proposed that the occupants from the both levels of the Lecture theatre shall escape via the upper ground floor only. The means of escape from the Lecture theatre and the other academia areas i.e. seminar breakout rooms have been analysed separately due to the independent escape routes proposed in each area. Figure 3 Means of escape from Upper ground of Lecture theatre Escape route 1 Exit width 2374 mm Escape route 2 Exit width 2374 mm X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 6

7 Figure 4 Alternative access routes from First floor of Lecture theatre 900 mm doors Escape route 3 - External stair Escape route 4 - Alternative access route using shared accommodation escape stair Doors to the stairs must be sized to allow the maximum occupant capacity of each level in the academic building. Calculations for escape widths will be based on achieving compliance with Table 4 of AD-B. Doors at the base of shared accommodation stair leading directly to the outside should have a clear width of no less than the width of the stairs. Table 1 summarises the minimum escape widths required for the Lecture theatre with two final exits provided which does not include the seminar /breakout space, common rooms or reception spaces. Table 1 Minimum escape widths required for the Lecture theatre only Lecture theatre Total number of exits Maximum population Exit width available (discount largest exit) Minimum escape widths required x 2374 mm 2 x 2500 mm The required exit widths based on 5 mm per person are two exits at least 2500 mm width following the guidance of AD-B. The risk of providing 126 mm less than that required is mitigated by the enhanced detection provided in the Lecture theatre which provides early warning of fire, hence reduces pre-movement time, limited occupancy, and escapes via the First floor are available. Although the First floor exits are not primarily used for emergency escape (therefore not included in the calculations in Table 1) these are available for use at all times and may be used by occupants in the Lecture theatre in the event of a fire given their familiarity with the building. Further analysis was undertaken to justify the means of escape via the Upper ground floor only and other escape scenarios from the Lecture theatre. This should be discussed and agreed with Building Control. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 7

8 2.2.1 Simulation of Transient Evacuation and Pedestrian movements (STEPS) The computer evacuation model, Simulation of Transient Evacuation and Pedestrian movements (STEPS) has been undertaken to show that the escape routes within the Lecture theatre provide sufficient escape widths for the maximum occupant capacity in an acceptable evacuation time of 2.5 minutes. Based on the results of the STEPS model and the escape routes provided, the current layouts appear adequate for means of escape from the Lecture theatre and are considered acceptable. The full STEPS analysis results is provided in a separate report titled University of Kent STEPS analysis, Revision 1 and issue date The internal accommodation stair linking the Upper Ground and First Floors has not been considered in the means of escape analysis. It is a requirement to protect the external stair in accordance with Approved Document B. Under this document, it is not permitted to have an external escape stair that would be used by the public. As the stair will only serve one level, it is considered reasonable that an external escape route will be acceptable as an alternative escape route. As the external escape stair will only serve one level, it is not required to be served by fire doors, however the wall construction within 1.8 m in all directions of the stair are required to be fire rated to achieve at least 30 minutes. Use of this stair will need to be discussed and agreed with Building Control Travel distances The maximum travel distance permitted in an Assembly and recreation building is 18m in a single direction of escape only and up to 45m where there is more than one escape route available. In the lecture theatre where there will be rows of seating; the maximum permitted travel distances are 15m in a single direction or 32m where there is more than one escape route available, based on the guidance of AD-B. There are generally two means of escape from most areas of the building. Areas which may be limited to a single escape route are the seminar/breakout rooms and office. The actual travel distances in the Academic Building are approximately 10 m dead end distance from the seminar rooms, and total distance within 30 m. Within the theatre, the distances are up to 25 m where there are two directions of escape. Within plant rooms, AD-B recommends distances within 9 m, which can sometimes be increased to 18 m for low risk with only single direction of escape available. The maximum permitted overall travel distance where more than one escape route is available is up to 45 m. The spacing between the seating will need to comply with the recommendations of BS 5588 Part 6. The current seating plan indicates up to twenty-four seats where there are two escape routes, and up to thirteen seats where there is one escape route. BS 5588 Part 6 recommends that the seatway width (clear space between the back of the seat to the front of the chair behind) should be at least 425 mm where there are twenty-four seats with two means of escape, however also recommends that no more than twelve seats be provided where there is a single escape route. The current layouts are not in compliance with the Building Regulations therefore changes may be required for approval. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 8

9 2.3 Means of escape Academia areas The general means of escape for the Academic building has been analysed with the maximum occupant capacity at each level. The escape routes available and the proposed uses of the Academic rooms are highlighted in Figures 5 and 6. Based on the current plans, there are three exits to the outside at the Upper ground level and two exits provided on the First floor, not including the open accommodation stair. The occupant capacity of the individual rooms shall be determined by the use of floor space factors given in AD-B. The kitchen has been provided with an independent escape route therefore not included in the means of escape calculations. It is assumed that the Lecture theatre shall escape independently from the other areas in the Academic building. The University is responsible for maintaining the building and there should be strict management control of the academic areas at all times. It is not strictly permitted under Approved Document B to share stairs between academic and residential use however this is considered acceptable given the following: Each block has one independent stair. The stairs will be sized so that each stair can cater for the full occupant load. Therefore should a fire occur that compromises the shared stair, both the residential and assembly buildings will still have sufficient alternative means of escape. The two different uses will be separated with fire rated construction achieving the compartmentation rating of 60 minutes. Each building will be provided with an L1 fire alarm system which will raise early warning to the occupants in the building of fire origin, also alerting management who can evacuate the adjoining block if required. The principle of the means of escape from the Academic building has been accepted by Building Control. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 9

10 Figure 5 Escape from Upper Ground level Compartment wall separating occupancies Accommodation stair is enclosed at Upper ground only (not fire resisting) Figure 6 Escape from First Floor X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 10

11 The minimum number of exits required for the maximum population at each level has been calculated and summarised in Tables 2 and 3, based on calculations in accordance with Approved Document B. The approximate floor areas are based on architect drawings. Table 2 - Occupant capacity Level Upper ground Total floor area Floor space factors based on AD-B Maximum occupant capacity Office & Reception 6 m 2 /person 9 people 15 m 2 & 43 m 2 Common Room 67 m 2 1 m 2 /person 67 people Exhibition/ Foyer 1.5 m 2 /person 114 people 172 m 2 First Floor Seminar/ breakout 1.0 m 2 /person (conference 312 m 2 and common rooms etc) 312 people A floor space factor of 1.0 m 2 /person has been used for the Seminar/breakout rooms. The exit widths for the desired occupant capacity will need to be finalised when advised of the Client s requirements. Table 3 Minimum escape widths required Level Total number of exits per level Maximum population Upper ground persons First Floor Minimum stair width required Direct escape to outside persons 1560 mm Minimum exit widths required 3 x 850 mm 2 x 1560 mm, or 3 x 1050 mm For means of escape purposes it is assumed that the largest exit is discounted due to a fire blocking an exit and the table above outlines the minimum width of escape routes required. On the upper ground level the current plans shows that the numbers of exits provided satisfy the maximum population of 190-people, however some changes may be required in order to accommodate a higher occupant capacity on the First floor level. On the first floor occupants can escape through the shared enhanced residential stair or via the lecture theatre. As one exit is required to be considered untenable for escape, each stair should have the capacity to cater for the maximum population of the first floor. This requires an exit width of 1560 mm for each exit based on 5 mm per person from AD-B. The current layout does not have sufficient exit capacity, however the design occupant load used for the seminar rooms may be an onerous assumption. Given the proposed exit widths the maximum population for the first floor is 220-persons based on at least two x 1050 m doors provided. As part of the management strategy it is understood that the University will operate on a maximum capacity of 220-people permitted on the first floor which is in compliance with AD-B. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 11

12 2.3.1 Travel distance The maximum travel distance permitted in an Assembly and recreation building is 18m in a single direction of escape only and up to 45m where there is more than one escape route available. Where the internal layout is unknown two thirds of the permitted travel distance should be used for means of escape design. Given that there are two means of escape from each level, the proposed design falls within the recommended travel distances based on the current plans. 2.4 Means of escape Licensed areas As part of the University of Kent development it may be proposed to have a licensed bar located in the Academic building. This will be subject to licensing regulations and higher occupant figures. A general overview of the proposed bar design and the effects based on the current layout has been provided in this section. The means of escape from the licensed area is based on the event of a fire at either level. It is assumed that the Lecture Theatre and the bar area will not be occupied at the same time therefore simultaneous evacuation of both uses will not occur. The bar area will only be located within a small part of the Upper Ground level as highlighted in Figure 7. Based on the current plans for the licensed area, there are three exits at the Upper Ground level. The occupant capacity of the licensed areas will be determined by the available exits widths and number of escape routes available. Figure 7 Escape from Licensed area at Upper Ground only The minimum number of exits required for the maximum population in the licensed area has been analyzed and summarised in Table 4, based on calculations in accordance with AD-B. The approximate floor areas are based on architect drawings. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 12

13 Table 4 Required exit from licensed areas Upper Ground Licensed area Floor area Floor space factor Maximum population Standing area 37.5 m m2 per person 38 people Bar 29.5 m m 2 per person 98 people Minimum exit width required 2 x 1050 mm doors The maximum population capacity of the licensed area is calculated using floor space factors from AD-B. A floor space factor for bar/function rooms is 0.3 m 2 per person within two metres of the bar serving area and 1.0 m 2 per person for the remainder of the room. This should be updated when the bar layout is finalised and will need to correspond with the licensing agreement. The total number of people including the reception, office and foyer/exhibition space within the licensed area is 259-people. This would require a minimum of 2 x 1050 mm doors and 1 x 850 mm door. The current plan shows that the proposed number of exits and exit width for the Upper Ground level is adequate with a licensed bar area Travel distance The maximum travel distance permitted in a bar is 18m in a single direction of escape only and up to 45m where there is more than one escape route available. Where the internal layout is unknown two thirds of the permitted travel distance should be used for means of escape design. Given that there are two means of escape from each level, the proposed design falls within the recommended travel distances based on the current plans. 2.5 Open spatial planning The accommodation stair which links the Upper ground and First floor is enclosed (not fireresisting) at the lowest floor level. Under the Approved Document B: 2006 Diagram 14, escape routes should not be prejudiced by openings between floors. As the stair is enclosed at Upper ground level with proposed self-closing fire doors to access the stair, smoke from a fire at the lower level should not spread up to the First level therefore it is not considered an open stair. 2.6 Disabled Means of Escape Disabled egress is to comply with BS 5588 Part 8. Refuge spaces must be provided within the shared stair core and adjacent to the external stair, with minimum width of 1400 mm x 900 mm that is located out of the flow of evacuating occupants. Two-way communication should be provided from all refuge areas to a management suite to facilitate evacuation for these occupants. 2.7 Emergency Lighting Emergency lighting should be installed throughout all common escape routes in accordance with BS 5266 Part 1. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 13

14 3.0 INTERNAL SPREAD OF FIRE 3.1 Compartmentation The height of the Academic building is 3.4 m to the highest floor level. Under Approved Document B: 2006, this would require a compartment rating of 60-minutes. This rating is required to be applied for the construction of the party wall between different uses i.e. separating Enhanced residential accommodation to the Academic building. Based on the guidance of AD-B no compartment floors are required for an Assembly and Recreational building type and given that the Academic building is considered a separate compartment to the residential use and less than 30 m height. A 60-minute rating is required for the adjoining Enhanced Accommodation block therefore increased ratings are not required between the two uses. Table 5 Schedule of Fire doors Location of door Door to means of escape stairs Door from protected lobby to stairway Sub-dividing corridors doors Any doors in a compartment wall Fire door required FD30S FD30S FD20S FD30S The open accommodation stair serving the First level of the Academic building is not passing through a compartment floor therefore it is does not need to be enclosed in fire resisting construction. The kitchen is separated from the public spaces in the academic building and provided with an independent escape route to the outside. The kitchen may be classified as a higher risk room however is not required to be enclosed in fire resisting construction under the Building Regulations. However, for property protection it may be prudent to enclose this room with 30 minutes fire resistance. 3.2 Elements of Structure The Academic Building will be a concrete and steel structure. The elements of structure for the development should be constructed in accordance with Table A2 of AD-B. Based on the current height of less than 18 m, the elements of structure for the entire building require a structural rating of 60-minutes. The means of escape stair shared between the two occupancy uses is required to be protected with 60 minutes fire resisting construction. 3.3 Sprinklers Based on the height of the buildings, there is no requirement to provide sprinkler protection throughout either the Academic Building or the adjoining residential block. Therefore sprinklers will not be provided within the design. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 14

15 4.0 EXTERNAL SPREAD OF FIRE The Academic building is bounded by public roads on two sides, Student Hall 5 and recreational space from the west elevation. An analysis of the current layout of the Academic building has been undertaken based on the BRE 187 guidance document External fire spread: building separation and boundary distances. This has been calculated using the method of enclosing rectangles based on the minimum boundary distances required for Assembly & Recreation building type. Table 6 Academic building Elevation of Academic building facing the notional boundary line Enclosing rectangle in metres (m) Distance to notional boundary line Percentage of unprotected area permitted in enclosing rectangle North N/A - - South 6.0 x m 70% East 6.0 x m 80% West 6.0 x m 100% In summary, all elevations appear to have sufficient distance for the amount of unprotected areas required based on the current plans and elevations for each block. The west elevation is made up of glazing mainly on the Academic elevation and a door located on the Lecture theatre façade. A notional boundary distance of 13m allows sufficient distance for the glazing percentages required on the elevations. All areas that are not permitted to be unprotected are required to achieve the building compartment rating. 5.0 FIRE SERVICE ACCESS 5.1 Fire Service access to the building The Darwin Fields development sits on a naturally sloping site. The height to the top floor level for the Academic building is measured from the Fire Service access level which is approximately 3.4 m. The plan floor area of the building is approximately 1,100 m 2. As the theatre effectively has a single level, the total floor area of the building is 1,600 m 2. Based on the height of the building, fire mains are not required in the Academic building. There should be either 15% of the buildings perimeter is available for Fire Service access for a pump appliance in accordance with AD-B, or all areas of the projected plan area of the building should be within 45m of Fire Service vehicular access. The current site plan for the Academic building shows that more than 15% of the building s perimeter is accessible for a pump appliance therefore dry rising mains are not required based on the guidance of AD-B Section B Hydrant provision In accordance with AD-B, hydrants are required for a building which has a compartment of 280m 2 or greater in area, and the building is being erected more than 100 m from an existing fire hydrant. A survey on the existing site has been carried out to determine the location of existing hydrant points. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 15

16 Currently the compartment sizes in some of the buildings exceed 280m 2. The existing hydrants coverage in the architect s drawings (refer to drawing 406-SK FireHydrants) shows that the buildings are within 100 m of a hydrant therefore additional private hydrants need not be provided for the development. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 16

17 6.0 CONCLUSION Table 7 Fire Precautions to be taken Means of Escape L1 Fire alarm system is to be provided throughout the building in accordance with BS 5839 Part 1. Simultaneous evacuation procedure with investigation period to be provided. Independent evacuation procedures between the Enhanced accommodation block and Academic block. The shared escape route between the Enhanced accommodation block and the Academic block has been agreed with Building Control. The Lecture theatre will evacuate only via Upper ground floor exits. Refer to STEPS Analysis report. Sufficient escape width is available from the Upper ground floor academic areas however this will be confirmed when occupant loads are finalised. Adequate escape widths should be provided to serve the First floor by having a maximum occupant capacity of 220-people. Licensed area needs to be confirmed for means of escape purposes. It is assumed the licensed bar would never be used at the same time as the lecture theatre. External escape stair to be protected from external walls for 1.8 m in all directions if to be used as an alternative means of escape route. Emergency lighting should be installed throughout common areas of the building in accordance with BS 5266 Part 1. Disabled access is required to comply with BS 5588 Part 8. Refuge spaces are required within each stair core, and two-way communication must be provided at each refuge space. Internal Fire Spread Elements of structure are to achieve 60 minutes throughout building. Compartment walls will achieve 60 minutes fire resistance. The building is designed under purpose group Assembly and Recreational. No compartment floors are required for the Academic building based on its height. The Enhanced accommodation and Academic use will be separated by 60 minutes fire resistant compartment wall. Sprinkler protection will not be provided. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 17

18 External Fire Spread External spread of fire is likely to be acceptable given sufficient distance is available to the notional boundary line and the percentage of unprotected openings required in the elevations. Fire Service Access Fire Service access can access 15% of the building s perimeter therefore dry rising mains are not provided. Access for a pump appliance to the Academic Building is available. Additional private fire hydrants are not required for the site based on coverage from existing site hydrants. X:/FireEng/Projects/ /11/ACADEMIC_REP_ _11_LY_231007_7 Page 18