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f_ay,θ maximum stress level or effective yield strength of structural steel in the fire situation

f_ay,θcr strength of steel at critical temperature θ_cr

f_ap,θ; proportional limit of structural or

f_sp,θ reinforcing steel in the fire situation

f_au,θ ultimate tensile strength of structural steel or steel for stud connectors in the fire situation, allowing for strain-hardening

f_ay characteristic or nominal value for the yield strength of structural steel at 20°C

f_c characteristic value of the compressive cylinder strength of concrete at 28 days and at 20°C

f_c,j characteristic strength of concrete part j at 20°C

f_c,θ characteristic value for the compressive cylinder strength of concrete in the fire situation at temperature θ°C

f_c,θn residual compressive strength of concrete heated to a maximum temperature (with n layers)

f_c,θy residual compressive strength of concrete heated to a maximum temperature

f_fi,d design strength property in the fire situation

f_k characteristic value of the material strength

f_ry, f_sy characteristic or nominal value for the yield strength of a reinforcing bar at 20°C

f_sy,θ maximum stress level or effective yield strength of reinforcing steel in the fire situation

f_y,i nominal yield strength f_y for the elemental area A_i taken as positive on the compression side of the plastic neutral axis and negative on the tension side

h depth or height of the steel section

h₁ height of the concrete part of a composite slab above the decking

h₂ height of the concrete part of a composite slab within the decking

h₃ thickness of the screed situated on top of the concrete

h_c depth of the composite column made of a totally encased section, or thickness of the concrete slab

h_eff effective thickness of a composite slab

h_fi height reduction of the encased concrete between the flanges in the fire situation

design value of the net heat flux per unit area

design value of the net heat flux per unit area by convection

design value of the net heat flux per unit area by radiation

h_u thickness of the compressive zone

h_u,n thickness of the compressive zone (with n layers)

h_v height of the stud welded on the web of the steel profile

h_w height of the web of the steel profile

k_c,θ reduction factor for the compressive strength of concrete giving the strength at elevated temperature f_c,θ

k_E,θ reduction factor for the elastic modulus of structural steel giving the slope of the linear elastic range at elevated temperature E_a,θ

k_y,θ reduction factor for the yield strength of structural steel giving the maximum stress level at elevated temperature f_ay,θ

k_p,θ reduction factor for the yield strength of structural steel or reinforcing bars giving the proportional limit at elevated temperature f_ap,θ or f_sp,θ

k_u,θ reduction factor for the yield strength of structural steel giving the strain hardening stress level at elevated temperature f_au,θ

k_θ reduction factor for a strength or deformation property dependent on the material temperature in the fire situation

l length or buckling length

l₁, l₂,l₃ specific dimensions of the re-entrant steel sheet profile or the trapezoidal steel profile

l_w length (connection between steel profile and the encased concrete)

l_θ buckling length of the column in the fire situation

s_s length of the rigid support (calculation of the crushing resistance of stiffeners)

t duration of fire exposure

t_fi,d design value of standard fire resistance of a member in the fire situation

t_fi,requ required standard fire resistance in the fire situation

t_i the fire resistance with respect to thermal insulation

u geometrical average of the axis distances u₁ and u₂ (composite section with partially encased steel profile)

u₁; u₂ shortest distance from the centre of the reinforcement bar to the inner steel flange or to the nearest edge of concrete

z_i; z_j distance from the plastic neutral axis to the centroid of the elemental area A_i or A_j

Greek letters upper case letters

Δl temperature induced elongation of a member

Δl/l related thermal elongation

Δt time interval

Δθ_a,t increase of temperature of a steel beam during the time interval Δ

Δθ_t increase in the gas temperature [°C] during the time interval Δt

Φ configuration or view factor

Greek letters lower case letters

α angle of the web

α_c convective heat transfer coefficient

α_slab coefficient taking into account the assumption of the rectangular stress block when designing slabs

γ_G partial factor for permanent action G_k

γ_M,fi partial factor for a material property in the fire situation

γ_M,fi,a partial factor for the strength of structural steel in the fire situation

γ_M,fi,c partial factor for the strength of concrete in the fire situation

γ_M,fi,s partial factor for the strength of reinforcing bars in the fire situation

γ_M,fi,v partial factor for the shear resistance of stud connectors in the fire situation

γ_Q partial factor for variable action Q_k

γ_v partial factor for the shear resistance of stud connectors at normal temperature

δ eccentricity

ε strain

ε_a axial strain of the steel profile of the column

ε_a,θ strain in the fire situation

ε_ae,θ ultimate strain in the fire situation

ε_ay,θ yield strain in the fire situation

ε_ap,θ strain at the proportional limit in the fire situation

ε_au,θ limiting strain for yield strength in the fire situation

ε_c axial strain of the concrete of the column

ε_c,θ concrete strain in the fire situation