2.2　Symbols

2.2.1　Actions（loads and resistances）:

N——Design value of axial force；

N1，N2——Factored axial forces on the two tubes in a dumbbell-shaped arch rib；

M——Design value of sectional moment；

M1，M2——Factored sectional moments on the two tubes in a dumbbell-shaped arch rib；

Ns——Design value of axial compressive force combination；

S——Design value of combination of actions；

R——Design value of resistance of a component；

R（·）——Load resistance function of a component；

V1——Design value of axial force of web truss.

2.2.2　Material properties:

（EA）sc——Design compressive stiffness of composite section of CFST arch rib；

（EI）sc——Design flexural stiffness of composite section of CFST arch rib；

（EA）sc1——Design compressive stiffness of gross section of CFST arch rib；

（EI）sc1——Design flexural stiffness of gross section of CFST arch rib；

（EA）sc2——Gross composite compressive stiffness of single tube CFST member；

（EI）sc2——Gross composite flexural stiffness of single tube CFST member；

Ec——Elastic modulus of concrete；

Es——Elastic modulus of steel；

fcd——Design compressive strength value of concrete；

fck——Characteristic compressive strength value of concrete；

fd——Design strength value of materials；

fvd——Design shear strength value of steel；

fs——Design tensile，compressive and bending strength values of steel；

ftd——Design tensile strength value of concrete；

ftk——Characteristic tensile strength value of concrete；

fy——Characteristic strength value of steel；

Gc——Shear modulus of concrete；

Gs——Shear modulus of steel；

N0——Design axial compressive strength of single tube CFST section；

N0′——Design axial compressive strength of single tube CFST section considering debonding；

Ni0——Design axial compressive strength of each CFST section in the arch rib；

N0i——Design axial compressive strength of the ith truss member in truss arch rib；

N01——Design compressive strength of eccentrically loaded single tube CFST member；

N02——Design stability resistance of eccentrically loaded single tube CFST member；

ND——Design compressive strength of dumbbell-shaped or laced CFST member；

ND1——Design compressive strength of eccentrically-loaded dumbbell-shaped or laced CFST member；

ND2——Design stability resistance of eccentrically-loaded dumbbell-shaped or laced CFST member；

Nif——Design compressive strength of connecting steel web plates that share loads with main CFST chords；

ftpk——Characteristic tensile strength of suspenders or ties；

α——Longitudinal thermal expansion coefficient of CFST arch rib subject to uniform temperature distribution on its section；

αs——Thermal expansion coefficient of steel；

αc——Thermal expansion coefficient of concrete；

ρs——Density of steel；

μc——Poissons ratio of concrete；

μs——Poissons ratio of steel；

σ——Stress in suspenders or ties；

σ0——Preloading stress of steel tube.

2.2.3　Geometric parameters:

ad——Design geometric parameter；

A——Converted area of CFST chord section；

Ab——Total sectional area of horizontal web trusses between adjacent joints；

Ac——Cross-sectional area of concrete core；

Ad——Total sectional area of diagonal web trusses between adjacent joints；

Afs——Cross-sectional area of connecting steel plate；

As——Cross-sectional area of steel tube；

Asc——Sectional area of CFST composite member；

As1——Cross-sectional area of steel tube in CFST arch rib；

Ac1——Cross-sectional area of concrete core in CFST arch rib；

ai——Distance from the center of individual CFST member to the virtual axis y-y in laced CFST column；

bi——Distance from the center of individual CFST member to the virtual axis x-x in laced CFST column；

D——Outer diameter of steel tube；

d——Diameter of suspenders or ties；

e0——Load eccentricity；

f——Rise of arch；

f1——Rise of arch above deck system；

h1——Central distance of two chords in bending plane of dumbbell-shaped or laced CFST column；

h2——Depth of web plate of dumbbell-shaped CFST section；

H——Depth of the cross section of arch rib；

r——Calculated radius of cross section；

i——Cross-sectional radius of gyration；

Ic——Second moment of area of concrete core section；

Is——Second moment of area of steel tube section；

Isc——Second moment of area of composite section of CFST；

Is1——Second moment of area of steel section；

Ic1——Second moment of area of concrete section；

l——Length of component；

L——Calculated span of arch bridge；

l0——Calculated length of component；

l01——Clear span of arch rib；

L0——Equivalent calculated length of arch rib；

Ld——Length of suspender；

Lz——Straight length of arch rib segment；

l0x——Calculated length of a component relative to axis X；

l0y——Calculated length of a component relative to axis Y；

l1——Distance between adjacent joints of laced CFST column；

l2——Longitudinal distance between stiffeners along the web plates of dumbbell-shaped arch rib；

rc——Radius of cross section of concrete core；

Sg——Length of arch axis；

t——Thickness of steel tube or initial setting time of concrete；

T——Calculated closure temperature；

T0——Additional temperature increase；

T28——Average air temperature during 28 days after filling of concrete；

εb——Bound eccentricity ratio；

θ——Angle between two adjacent arch rib segments；

Δ——Gap between branch tubes in a joint.

2.2.4　Coefficients in calculation and others:

β——Preloading ratio of steel tube；

ξ0，ξ——Design and characteristic confinement coefficients of CFST member，respectively；

ρ——Load eccentricity ratio；

ρc——Steel ratio of CFST section；

χ——Calculation coefficient；

μ——Slenderness coefficient；

μ0——Impact coefficient of vehicular load for CFST arch rib；

γ0——Importance coefficient of bridge structure；

η1——Sectional flexural stiffness ratio of individual CFST chord to the whole CFST member；

φ——Stability factor；

φe——Reduction factor of eccentricity ratio；

λ——Nominal slenderness ratio of CFST member；

λn——Relative slenderness ratio；

λ*——Converted slenderness ratio of laced CFST column；

λ1——Nominal slenderness ratio of individual chord of laced CFST column；

λx，λy——Nominal slenderness ratio of laced CFST column relative to X-axis and Y-axis，respectively；

a——Coefficient considering the effects of slenderness ratio when calculating the resistance of preloaded CFST members at ultimate limit state；

f0——Frequency of the first vertical mode of vibration of a CFST arch bridge；

kc——Reduction factor for creep of the load capacity of CFST member；

Kp——Influence factor for preloading ratio；

k1——Load factor；

k2——Traffic lane coefficient；

k3——Conversion coefficient of design axial compressive strength；

Kt——Reduction factor for load capacity of CFST with debonding；

K——Coefficient for converted slenderness ratio；

K′——Correction factor for converted slenderness ratio；

m——Coefficient considering the influence of eccentricity in calculating the resistance of preloaded CSFT member at ultimate limit state；

n——Number of chords in CFST truss arch rib；

V——Rated speed of transmission pump；

Q——Volume of filling concrete in tube.