Скачать презентацию Eurocode 1 Actions on structures Part 1

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Eurocode 1: Actions on structures – Part 1– 2: General actions – Actions on structures exposed to fire Annex E (informative) → Fire load densities Part of the One Stop Shop program

Introduction • Fire load density evaluation • FLD used is a “design value” based on – Measurements or – Values given in national regulations • Determined by – Classification of occupancies and/or – Individual project analysis

Design value • The design value of the fire load: Characteristic fire load density per unit floor area Combustion factor Fire activation risk factors for Compartment size and Type of occupancy Fire-fighting measures risk factor

Determination of fire load densities • Fire load density needs to be determined taking into account – Type of building / occupancy – Protected fire loads – Calorific value of fuel • This process is used to determine the value of for previous equation

from occupancies • For a large number of buildings, e. g. offices, residencies, hotels, and the paper industry, In which case, Table E. 4 may be used to determine the value of • Separate fire load densities within the building should be added to the tabular value if necessary

from basic principles • To obtain Compartment area we must obtain a value for Characteristic fire load Net calorific value Amount of combustible material Optional factor for protected loads

Combustion factor • Having determined a value for we next need a value for - the combustion factor • The value of 0. 8 is taken for cases mainly consisting of cellulosic fuels • In other cases the combustion behaviour should be looked at as a function of occupancy and type of fire load

Fire activation risk factors 1. Due to size of compartment: 2. Due to type of occupancy: The factors vary from just under 1. 0 to just over 2. 0 – the particular value used is taken from Table E. 1 included in the Annex

Fire-fighting measures risk factors • This factor is a function of active firefighting measures • Takes into account – Fire suppression systems – Automatic fire detection and alarm systems – Manual fire suppression systems • The values for the individual factors are given in Table E. 2

Worked example • Work out the design fire load for a 6, 500 m 2 office space, with no additional fuels present in the space. – The office is sprinkler protected – Heat detectors are the only source of A&D system within the space – No other special provisions are present apart from the normal fire-fighting measures

Worked example - workings • From Table E. 4, we can see the value of can be taken as 420 MJ/m 2 • This value may be taken because the value of is 1. 0 (Table E. 1) • The value of can be taken as 0. 8 • The value of is 2. 0, as it is between the 5, 000 and 10, 000 m 2 brackets (Table E. 1)

Worked example - workings • The value of is therefore averaged from 0. 61, 0. 87, and 1. 0 which results in having a value of 0. 83

Worked example - answer • Putting these values back into the original equation gives us a design value of the fire load for our test case scenario highlighted in the worked example as: MJ/m 2