View source for Car parks in fire

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For the purposes of determining [[Structural_fire_resistance_requirements|fire resistance requirements]], certain types of [[Car_parks|car parks]] may be classed as 'open sided'. [[Car_parks_in_fire#Open_car_parks|Open sided car parks]] are above ground and have large openings in the facade for natural ventilation. They have relatively low [[Structural_fire_resistance_requirements|fire resistance requirements]] whereas those for other [[Car_parks|car parks]] are typically consistent with those for commercial buildings of the same height.
<gallery wrap=true style="float:right;" widths=200px heights=135px> 
Image:M1_Fig16.jpg|Southmead<br>''(Image courtesy of Bourne Construction Engineering Ltd.)''
Image:M1_Fig42.JPG|St Mellons, Cardiff<Br>''(Image courtesy of Bourne Construction Engineering Ltd.)''
Image:M1_Fig19.jpg|[[Steel_construction_products#Cellular_beams|Cellular beams]] with pre-cast concrete units<Br>''(Image courtesy of Kloeckner Metals UK Westok)''
</gallery>

==Open car parks==
The definition of an open [[Car_parks|car park]] is set out in [[Structural_fire_resistance_requirements#Approved_Document_B|Approved Document B]] <ref name="No1">[https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/937932/ADB_Vol2_Buildings_other_than_dwellings_2019_edition_inc_2020_amendments.pdf Approved Document B (Fire safety, Volume 2 – Buildings other than Dwellings), 2019 edition incorporating 2020 amendments – for use in England . Ministry of Housing, Communities & Local Government]</ref>, Section 11.2 as being a [[Car_parks|car park]] which is above ground and in which ''Each storey is naturally ventilated by permanent openings at each car parking level. The aggregate vent area is a minimum of 1/20 of that level’s floor area, at least half of which is provided equally by two opposite walls''. The Regulations include other requirements for materials and car parks in mixed-use buildings. Similar definitions operate in Scotland, Wales and Northern Ireland. 
 
In most instances, open [[Car_parks|car parks]] can be constructed without [[Fire_protecting_structural_steelwork|fire protecting]] the structural steel. In a small number of situations, it may be necessary to [[Fire_protecting_structural_steelwork|fire protect]] the steel or to increase the size/[[Steel_material_properties#Yield_strength|grade]] if it is to be unprotected.

==Unprotected steel==
{{#image_template:image=File:Unprotected_steel_in_car_park_1.png|caption=Unprotected steel in an open car park|align=right|wrap=true|width=250}}
Across the United Kingdom, those responsible for preparing documents such as [[Structural_fire_resistance_requirements#Approved_Document_B|Approved Document B]] <ref name="No1"></ref> recognise that there is a low risk of fire spread and ample opportunity for smoke and hot gases to be dissipated in [[Car_parks_in_fire#Open_car_parks|open car parks]] when the [[Car_parks_in_fire#Open_car_parks|minimum ventilation criteria]] are met. Consequently, the structural frame is required to have only 15 minutes [[Structural_fire_resistance_requirements|fire resistance ]] when the [[Car_parks|car park]] is open and less than 30 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]] (18 metres in Scotland). Also across the UK, it is accepted within the Building Regulations that [[Steel_construction_products#Standard_open_sections|hot rolled structural sections]] and [[Steel_construction_products#Structural_hollow_sections|tubes]] under full [[Design_using_structural_fire_standards#Effect_of_load|design load in fire]] conforming to the following criteria are deemed to have 15 minutes inherent [[Structural_fire_resistance_requirements|fire resistance]]: 

*[[Steel_construction_products#Standard_open_sections|beams]] supporting concrete floors, each [[Steel_construction_products#Standard_open_sections|beam]] having a maximum [[Calculating_section_factors|section factor]] (A<sub>m</sub>/V) of 230 m<sup>-1</sup>; and 
*free standing [[Steel_construction_products#Standard_open_sections|columns]], each having a maximum [[Calculating_section_factors|section factor]] (A<sub>m</sub>/V) of 180 m<sup>-1</sup>; and
*wind bracing and struts, each having a maximum [[Calculating_section_factors|section factor]] (A<sub>m</sub>/V) of 210 m<sup>-1</sup>
<br>
In practice, the great majority of [[Steel_construction_products#Standard_open_sections|hot rolled structural sections]]  meet these criteria. The small number of [[Steel_construction_products#Standard_open_sections|sections]] which have higher [[Calculating_section_factors|section factors]] may do so if they are less than fully loaded (see below).

It should be noted that Section 2.1.1 in [[Structural_fire_resistance_requirements#Technical_Handbook_2022|Scottish Technical Handbook 2022]]<ref name="No2">[https://www.gov.scot/publications/building-standards-2022-technical-handbook-non-domestic/ Building standards technical handbook: 2022 – Non-domestic, Section 2 – Fire, The Scottish Government]</ref> states in Table 2.2 that [[Car_parks_in_fire#Open_car_parks|open car parks]] up to 18 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]] require 30 minutes [[Structural_fire_resistance_requirements|fire resistance]] (a period defined in that document as ‘short’). However, this is effectively overriden in Section 2.D.3, which states that [[Steel_construction_products#Standard_open_sections|sections]] conforming to the above limitations on [[Calculating_section_factors|section factor]] will be deemed to meet the required fire resistance criteria.
<gallery caption="Unprotected steel in open car parks" perrow=3 widths=200px heights=135px> 
Image:M1_Fig1.jpg|''(Images courtesy of Kloeckner Metals UK Westok)''
Image:M1_Fig39.jpg
Image:Unprotected_steel_in_car_park_2R1.png 
</gallery>
<br>

==Structural steel not achieving 15 minutes inherent fire resistance==
The data on limiting [[Calculating_section_factors|section factors]] to achieve 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] can also be expressed as a function of [[Design_using_structural_fire_standards#Effect_of_load|load ratio]] as defined in [[Design_using_structural_fire_standards#BS 5950_Part_8|BS 5950 Part 8]]<ref name="No3">BS 5950-8: 2003, Structural use of steelwork in buildings. Code of practice for fire resistant design. BSI</ref> or [[Design_using_structural_fire_standards#Effect_of_load|utilization factor]] as defined in the [[Design_using_structural_fire_standards#Fire_Eurocodes|fire Eurocodes]]. In the British Standard, a fully loaded beam or column is normally assumed to have a [[Design_using_structural_fire_standards#Effect_of_load|load ratio]] of 0.6. Assuming that the [[Design_using_structural_fire_standards#Effect_of_load|load ratio]] is 0.6, most hot rolled [[Steel_construction_products#Standard_open_sections|beams and columns]] will achieve 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] without [[Fire_protecting_structural_steelwork|fire protection]]. The exceptions, and the maximum [[Design_using_structural_fire_standards#Effect_of_load|load ratios]] which will allow these sections to achieve 15 minutes inherent  [[Structural_fire_resistance_requirements|fire resistance]], are provided.

{|class="wikitable" width=650 style="text-align: center"
|+'''UB sections not achieving 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] when fully loaded: British Standard design'''
|-
!style="width: 25%" rowspan="2"|'''UB section size'''
!style="width: 15%" rowspan="2"|'''Section factor<br>(A<sub>m</sub>/V)'''
!colspan="2"|'''Maximum load ratio to achieve 15 minutes fire resistance'''
|-
!style="width: 30%"|'''Non-composite'''!!style="width: 30%"|'''100% shear connection (Dovetail deck or filled voids)'''
|-
|127x76UB13||280 m<sup>‐1</sup> ||0.53 ||0.41
|-
|152x89UB16|| 270 m<sup>‐1</sup> ||0.53 ||0.41
|-
|178x102UB19|| 260 m<sup>‐1</sup> ||0.55 ||0.43
|-
|203x102UB23|| 235 m<sup>‐1</sup> ||0.64 ||0.5
|-
|203x133UB25|| 245 m<sup>‐1</sup> ||0.54 ||0.42
|-
|254x102UB22|| 280 m<sup>‐1</sup> ||0.47 ||0.37
|-
|254x102UB25|| 250 m<sup>‐1</sup> ||0.58 ||0.45
|-
|305x102UB25|| 280 m<sup>‐1</sup> ||0.49 ||0.38
|-
|305x102UB28|| 250 m<sup>‐1</sup> ||0.59 ||0.47
|-
|356x127UB33|| 250 m<sup>‐1</sup> ||0.59 ||0.46
|-
|406x140UB39|| 240 m<sup>‐1</sup> ||0.59 ||0.46
|}

{|class="wikitable" width=650 style="text-align: center"
|+'''UC sections not achieving 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] when fully loaded: British Standard design'''
|-
!style="width: 25%"|'''UC section size'''
!style="width: 15%"|'''Section factor<br>(A<sub>m</sub>/V)'''
!style="width: 20%"|'''Slenderness ratio<sup>a</sup>'''
!style="width: 40%"|'''Maximum load ratio to achieve 15 minutes fire resistance'''
|-
|152UC23||305 m<sup>‐1</sup>||81|| N/A, Choose next in the section range
|-
|152UC30||235 m<sup>‐1</sup>||78|| 0.36
|-
|152UC37||195 m<sup>‐1</sup>||77|| 0.45
|-
|203UC46||200 m<sup>‐1</sup>||58|| 0.51
|}

<sup>a</sup> Assumes an effective length of 3 metres. The failure temperature is a function of the slenderness ratio

The limiting utilization factors for Eurocode design are given below for non-composite beams and columns. These have been calculated using programmes which are available [[#Resources|here]]. These are generally lower than those calculated using British Standards. That is because [[Design_using_structural_fire_standards#Fire_Eurocodes|BS EN 1991-1-2]]<ref name="No4"> BS EN 1991-1-2: 2002,  Eurocode 1. Actions on Structures. General actions. Actions on structures exposed to fire. BSI</ref> includes a methodology for calculation of temperature rise in fire which is much more severe than that on which the data in [[Design_using_structural_fire_standards#BS_5950_Part_8|BS 5950 Part 8]]<ref name="No3"></ref>  is based. This means that the sections are assumed to get hotter more quickly.   

{|class="wikitable" width=650 style="text-align: center"
|+'''UB sections not achieving 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] when fully loaded: Eurocode design'''
|-
!style="width: 25%"|'''UB section size'''
!style="width: 15%"|'''Section factor<br>(A<sub>m</sub>/V)'''
!Style="width: 40%"|'''Maximum utilization factor to achieve 15 minutes fire resistance (non-composite)'''
|-
|127x76UB13||280 m<sup>‐1</sup> ||0.29 
|-
|152x89UB16|| 270 m<sup>‐1</sup> ||0.29 
|-
|178x102UB19|| 260 m<sup>‐1</sup> ||0.3 
|-
|203x102UB23|| 235 m<sup>‐1</sup> ||0.33 
|-
|203x133UB25|| 245 m<sup>‐1</sup> ||0.34 
|-
|254x102UB22|| 280 m<sup>‐1</sup> ||0.27 
|-
|254x102UB25|| 250 m<sup>‐1</sup> ||0.3 
|-
|305x102UB25|| 280 m<sup>‐1</sup> ||0.26 
|-
|305x102UB28|| 250 m<sup>‐1</sup> ||0.29 
|-
|356x127UB33|| 250 m<sup>‐1</sup> ||0.29
|-
|406x140UB39|| 240 m<sup>‐1</sup> ||0.3
|}

{|class="wikitable" width=650 style="text-align: center"
|+'''UC sections not achieving 15 minutes [[Structural_fire_resistance_requirements|fire resistance]] when fully loaded: Eurocode design<sup>b</sup>'''
|-
!style="width: 25%"|'''UC section size'''
!style="width: 15%"|'''Section factor<br>(A<sub>m</sub>/V)'''
!style="width: 40%"|'''Maximum utilization factor to achieve 15 minutes fire resistance'''
|-
|152UC23||305 m<sup>‐1</sup>||0.28
|-
|152UC30||235 m<sup>‐1</sup>||0.37
|-
|152UC37||195 m<sup>‐1</sup>||0.47
|-
|203UC46||200 m<sup>‐1</sup>||0.5
|}

<sup>b</sup> Assumes a length of 3 metres and an effective length factor of 0.5.

==Exceptional circumstances==
Certain situations exist where the deemed to satisfy criteria for structural steelwork in an [[Car_parks_in_fire#Open_car_parks|open car park]] may not apply: 
*Where one element of structure gives supports or carries or gives stability to another, the [[Structural_fire_resistance_requirements|fire resistance]] of the supporting element should be no less than the minimum period of [[Structural_fire_resistance_requirements|fire resistance]] of the other element (irrespective of whether that other element is loadbearing). An example of this is where a [[Steel_construction_products#Standard_open_sections|column]] gives stability to the [[Car_parks_in_fire#Open_car_parks|open car park]] and also to a compartment wall surrounding an escape stairway. In that case, the supporting column should have the same [[Structural_fire_resistance_requirements|fire resistance]] as the compartment wall. 
*If the building is also used for any other purpose, the part forming the [[Car_parks|car park]] is a separated part and the [[Structural_fire_resistance_requirements|fire resistance]] of any element of structure that supports or carries or gives stability to another element in another part of the building should be no less than the minimum period of [[Structural_fire_resistance_requirements|fire resistance]] of the elements that it supports. An example of this is where a column gives stability to an [[Car_parks_in_fire#Open_car_parks|open car park]] but also to an adjoining wall in another, separated building, the column must have the same [[Structural_fire_resistance_requirements|fire resistance]] as the steelwork in the other building.
<br>

==Other car parks==
{{#image_template:image=File:basement_car_park.png|caption=Basement car park|align=right|wrap=true}}
[[Structural_fire_resistance_requirements#Approved_Document_B|Approved Document B]]<ref name="No1"></ref> requires 60 minutes [[Structural_fire_resistance_requirements|fire resistance]] in [[Car_parks|car parks]] over 30 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]]. Where a [[Car_parks|car park]] is above ground but not defined as an [[Car_parks_in_fire#Open_car_parks|open car park]], 30 minutes [[Structural_fire_resistance_requirements|fire resistance]] is required for buildings up to 5 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]]; 60 minutes [[Structural_fire_resistance_requirements|fire resistance]] is required for buildings between 5 and 18 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]] and 90 minutes [[Structural_fire_resistance_requirements|fire resistance]]  is required for buildings between 18 and 30 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]]. For basement [[Car_parks|car parks]], the requirement is for 60 minutes [[Structural_fire_resistance_requirements|fire resistance]] if the depth is less than 10 metres and 90 minutes where the depth is greater than 10 metres. 

In Scotland, [[Structural_fire_resistance_requirements#Technical_Handbook_2|Scottish Technical Handbook 2]]<ref name="No2"></ref> requires basement [[Car_parks|car parks]] and [[Car_parks_in_fire#Open_car_parks|open car parks]] over 18 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]] to have 60 minutes [[Structural_fire_resistance_requirements|fire resistance]]. 
In Northern Ireland, [[Structural_fire_resistance_requirements#Technical_Booklet_E|Technical Booklet E]]<ref name="No5">[https://www.finance-ni.gov.uk/sites/default/files/publications/dfp/Technical-booklet-E-Fire-Safety-October-2012_0.pdf Technical Booklet E, Fire safety, Building Regulations (Northern Ireland) 2012, Department of Finance and Personnel of the Northern Ireland Government, 2012]</ref> generally follows the requirements of [[Structural_fire_resistance_requirements#Approved_Document_B|Approved Document B]]<ref name="No1"></ref> with the exception that [[Car_parks_in_fire#Open_car_parks|open car parks]] over 30 metres in [[Structural_fire_resistance_requirements#Approved_Document_B|height]] are not allowed and all [[Car_parks|car parks]] over that [[Structural_fire_resistance_requirements#Approved_Document_B|height]] have 120 minutes [[Structural_fire_resistance_requirements|fire resistance]] .

==References==
<references/>

==Resources==
*[[Media:Steel_construction_-_Fire_Protection.pdf|Steel construction - Fire Protection supplement, 2013]]
<br>
Member fire design tools:<br>
*[[Design software and tools#Resistance of beams at elevated temperature|Resistance of beams at elevated temperature]]
*[[Design software and tools#Resistance of columns at elevated temperature|Resistance of columns at elevated temperature]]

==Further reading==
*Fire safety in open car parks. No. 75. [https://www.steelconstruct.com/ European Convention for Constructional Steelwork]

==See also==
*[[Calculating_section_factors|Calculating section factors]]
*[[Design_using_structural_fire_standards|Design using structural fire standards]]
*[[Structural_fire_resistance_requirements|Structural fire resistance requirements]]

== CPD ==
*[[Continuing Professional Development#Design for fire|Design for fire]]
*[[Continuing_Professional_Development#Fire_Engineering_Seminars_2013|Fire engineering seminars 2013]]

[[Category:Fire and steel construction]]
[[Category:Index of main articles]]