Page 563 - Marine Structural Design

Chapter 30 Risk Assessment Applied fo offshore Structures 539

rupture of hydrocarbon containing equipment. Under certain conditions, structural failure or
collision impact may also lead to fires. Their final consequences are largely dependent on the
escalating sequences.
30.4.2 Fire Load and Consequence Assessment
A brief overview of some important aspects in the fire consequence analysis is made below.
Fire Types and Characteristics
Despite the fact that a fire originates from combustion reactions, the process of a fire may
largely depend on the factors that are not directly involved in combustion. Fires are therefore
usually separated into the following types:
Ventilation controlled fires in enclosed units (closed or partly closed)
Fuel controlled fire in enclosures
Pool fires in open areas or in modulus
Jet fires
Fires in running liquids
Fire balls
Gas fires (premixed, diffuse)
Other types of fire may occur in electrical equipment or in the accommodations or on sea.
These ‘non-hydrocarbon’ fires are not included here.
Burgan and Hamdan (2002) gave a list of research publications on fire and explosion load
characteristics, structural response analysis and performance requirements. The fire load may
be converted into thermal loads (time-temperature curves) acting on the structural members.
Some of the time-temperature curves are available in the literature in a form suitable for use in
design. The temperature-time history for a given structural member is affected by the applied
heat load, the shape of the member (for heat transfer) and the use of any passive fire protection
material.
Table 30.2 summarizes the main characteristics that need to be determined for these fire types.

Table 30.2 Fire Load Characteristics

Duration of leak

Fire Response Analysis Procedures
The assessment of fire response of structures has the following calculations: