1.0.1 This code is prepared with a view to preventing and minimizing fire hazard of steel structure in building, protecting personal and property safety, performing fire resistance design and taking fire protection measures in economic and rational way.
1.0.2 This code is applicable to the fire resistance design and fire protection of steel structure and composite structure in constructed, renovated and extended buildings.
1.0.3 This code is formulated on the basis of the limit state for fire resistance of steel structure at high temperature in case of fire and in line with the principle of probability limit state design method.
1.0.4 The fire resistance design and fire protection for steel structure in building shall comply with not only this code but also the current relevant national standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Fire load density
The heat of combustion from the combustibles per unit floor space (MJ/m2)
2.1.2 Standard fire temperature-time curve
The curve of the relationship between the average temperature in furnace and time in standard fire test for building component, as given in ISO 834
2.1.3 Equivalent time of fire exposure
Where, under non-standard fire temperature-time curve condition, the fire effect on component or structure for t time equals to the fire effect on the same component or structure for te time under standard fire temperature-time curve condition (same in external load), te is termed as the equivalent time of fire exposure of the former.
2.1.4 Limit state for fire resistance
The state at which the bearing resistance of component or structure equals to the synergic effect of applied actions (i.e. load and temperature), under fire condition.
2.1.5 Critical temperature
Supposing fire effects are distributed uniformly along the length and section of component, the temperature of the component section when the component reaches the limit state for fire resistance.
2.1.6 Load level /load ratio
The ratio of the bearing resistance of component in fire to that at normal temperature.
2.1.7 Concrete-filled steel tube
The component which is composed of circular or rectangular steel tube filled with concrete and in which the steel tube and concrete jointly bear load throughout the whole loaded process.
2.1.8 Composite component
The component of which the section is composed of two types of materials-profile steel and concrete, e.g. concrete filled steel tubular column, steel-concrete composite slab and steel-concrete composite beam.
2.1.9 Load bearing roof component
The main structural component for bearing roof load, e.g. components composing roof lattice rack, lattice shell and truss, roof beams and supports. Roof purlins generally are not deemed as load bearing roof component, unless they serve the supporting function of roof structure system.
2.1.10 Complete sprinkler system
The protection that sprinkler system is set in the building everywhere except toilet smaller than 5m2 in area.
2.2 Symbols
A C the gross sectional area of component;
Af C the sectional area of one flange;
Aw C the sectional area of beam web;
B C the comprehensive heat transfer coefficient per unit length of component;
Bn C the constant related to the restriction state at beam end;
cs C the specific heat capacity of steel;
ci C the specific heat capacity of protective layer;
di C the thickness of protective layer;
E C the elasticity modulus of steel at normal temperature;
ET C the elastic modulus of steel at high temperature;
f C the design strength of steel at normal temperature;
fy C the yield strength of steel at normal temperature;
fyT C the yield strength of steel at high temperature;
fc C the compressive strength of concrete at normal temperature;
fcT C the compressive strength of concrete at high temperature;
F C the surface area exposed to fire per unit length of component;
Fi C the inner surface area of protective layer per unit length of component;
h C the sectional height of component, also the thickness of floor slab;
hw C the height of beam web;
hd C the sectional height of profiled steel sheet;
I C the sectional inertia moment of component;
kr C the influence coefficient for the bearing resistance of concrete filled steel tubular column in fire;
l C the length/span of component;
l0 C the calculated length of component;
Mfi C the bending moment at rod end of fire exposed component, obtained from analysis using equivalent acting force;
Mp C the plastic moment;
MTi C the bending moment of temperature at rod end of fire exposed component;
Mx, My C the design value of maximum bending moment of component;
N C the design value of axial force of component;
N′ExT, N′EyT C the parameter of bearing resistance at high temperature;
Nf C the axial force of fire exposed component, obtained from analysis using equivalent acting force;
