---

E_fi,d,t design effect of actions, including indirect fire actions and loads in the fire situation, at time t;

(EI)_fi,c,z flexural stiffness in the fire situation (related to the central axis Z of the composite cross-section);

(EI)_fi,eff effective flexural stiffness in the fire situation;

(EI)_fi,f,z flexural stiffness of the two flanges of the steel profile in the fire situation (related to the central axis Z of the composite cross-section);

(EI)_fi,s,z flexural stiffness of the reinforcing bars in the fire situation (related to the central axis Z of the composite cross-section);

(EI)_fi,eff,z effective flexural stiffness (for bending around axis z) in the fire situation;

(EI)_fi,w,z flexural stiffness of the web of the steel profile in the fire situation (related to the central axis Z of the composite cross-section);

E_k characteristic value of the modulus of elasticity;

E_s modulus of elasticity of the reinforcing bars;

E_s,θ characteristic value for the slope of the linear elastic range of the stress-strain relationship of reinforcing steel at elevated temperatures;

E_s,θ,σ tangent modulus of the stress-strain relationship of the reinforcing steel at elevated temperature θ and for stress σ_i,θ;

F_a compressive force in the steel profile;

F⁺, F^- total compressive force in the composite section in case of sagging or hogging bending moments;

F_c compression force in the slab;

G_k characteristic value of a permanent action;

HC hydrocarbon fire exposure curve;

I thermal insulation criterion;

I_i,θsecond moment of area, of the partially reduced part i of the cross-section for bending around the weak or strong axis in the fire situation;

I 30 or I 60,... a member complying with the thermal insulation criterion for 30, or 60... minutes in standard fire exposure;

L system length of a column in the relevant storey;

L_eibuckling length of a column in an internal storey;

L_et buckling length of a column in the top storey;

M bending moment;

M_fi,Rd⁺; design value of the sagging or

M_fi,Rd^- hogging moment resistance in the fire situation;

M_fi,t,Rddesign moment resistance in the fire situation at time t;

N number of shear connectors in one critical length or axial load;

N_equequivalent axial load;

N_fi,cr elastic critical load (≡ Euler buckling load) in the fire situation;

N_fi,cr,z elastic critical load (≡ Euler buckling load) around the axis Z in the fire situation;

N_fi,pl,Rddesign value of the plastic resistance to axial compression of the total cross-section in the fire situation;

N_fi,Rddesign value of the resistance of a member in axial compression (≡ design axial buckling load) and in the fire situation;

N_fi,Rd,z design value of the resistance of a member in axial compression, for bending around the axis Z, in the fire situation;

N_fi,Sd design value of the axial load in the fire situation;

N_Rd axial buckling load at normal temperature;

N_snormal force in the hogging reinforcement (A_s f_sy);

P_Rd design shear resistance of a headed stud automatically welded

P_fi,Rd design shear resistance in the fire situation of a shear connector

Q_k,1 characteristic value of the leading variable action 1

R load bearing criterion

R 30 or R 60, R90, R120, R180, R240... a member complying with the load bearing criterion for 30, 60, 90, 120, 180 or 240 minutes in standard fire exposure

R_d design resistance for normal temperature design

R_fi,d,t design resistance in the fire situation, at time t

R_fi,y,Rd design crushing resistance in the fire situation

T tensile force

V volume of the member per unit length

V_fi,pl,Rd design value of the shear plastic resistance in the fire situation

V_fi,Sd design value of the shear force in the fire situation

V_i volume of the part i of the steel cross section per unit length [m³/m]

X Х (horizontal) axis

X_fi,d design values of mechanical (strength and deformation) material properties in the fire situation

X_k characteristic or nominal value of a strength or deformation property for normal temperature design

X_k,θ value of a material property in the fire situation, generally dependant on the material temperature

Y Y (vertical) axis

Z Z (column) central axis of the composite cross-section

Latin lower case letters

a_w throat thickness of weld (connection between steel web and stirrups)

b width of the steel section

b₁ width of the bottom flange of the steel section

b₂ width of the upper flange of the steel section

b_c depth of the composite column made of a totally encased section,

or width of concrete partially encased steel beams

b_c,fi width reduction of the encased concrete between the flanges in the fire situation

b_c,fi,min minimum value of the width reduction of the encased concrete between the flanges in the fire situation

b_eff effective width of the concrete slab

b_fi width reduction of upper flange in the fire situation

c specific heat,

or buckling curve,

or concrete cover from edge of concrete to border of structural steel

c_a specific heat of steel

c_c specific heat of normal weight concrete

c_p specific heat of the fire protection material

d diameter of the composite column made of concrete filled hollow section, or diameter of the studs welded to the web of the steel profile

d_p thickness of the fire protection material

e thickness of profile or hollow section

e₁ thickness of the bottom flange of the steel profile

e₂ thickness of the upper flange of the steel profile

e_f thickness of the flange of the steel profile

e_w thickness of the web of the steel profile

ef external fire exposure curve