Symbol	Description	Symbol	Description
ASO	Outer steel tube area (mm2)	fck	Characteristic of concrete strength (MPa)
ASI	Inner steel tube area (mm2)	fy	Yielding strength of steel tube (MPa)
AHPC	Area of high-performance concrete (mm2)	fu	Ultimate strength of steel (MPa)
BS	Width of outer steel tube (mm)	HPCFDST	High-performance fiber-reinforced cementitious filled-double skin steel tube
DS	Depth of outer steel tube (mm)	CFRP	Carbon fiber-reinforced polymer
bS	Width of inner steel tube (mm)	F	Full wrapping sheet
dS	Depth of inner steel tube (mm)	P	Partial wrapping sheet
BC	Width of outer concrete (mm)	ISI	Moment inertia of inner steel tube (mm4)
DC	Depth of outer concrete (mm)	ISO	Moment inertia of outer steel tube (mm4)
bc	Width of inner concrete (mm)	IS	Moment inertia of steel cross-section (inner and outer) (mm4)
dC	Depth of inner concrete (mm)	IC	Moment inertia of core HP concrete of cross-section (mm4)
EA	Energy adsorption (kN·mm)	L	CFRP layers attached on CFDST
EC	Modulus elasticity of concrete (GPa)	t	The thickness of the steel tube (mm)
ESI	Modulus elasticity of inner steel tube (GPa)	Le	Effective length (support to support) (mm)
ESO	Modulus elasticity of outer steel tube (GPa)	tCFRP, Scheme	Thickness of CFRP scheme (mm)
EST	Total modulus elasticity of steel tube (GPa)	Kp	Flexural stiffness of HPCFDST Beam (kN·m2)
ECFRP, Scheme	CFRP scheme modulus of elasticity (GPa)	KCFRP	The flexural stiffness of CFRP sheet (kN·m2)
Eadm	Modulus elasticity of adhesive martial (GPa)	Kt	Total flexural stiffness of specimen (concrete, steel, and CFRP) (kN·m2)
fcu	Compressive strength of HP concrete cube	LIR	Load improvement ratio
M	Bending moment (kN·m)	Kie	Initial flexural stiffness of composite member (kN·m2)
Mue	Ultimate moment bending capacity	Kse	Serviceability-level flexural stiffness of composite member (kN·m2)
B	Beam	φ COV	Curvature (1/m) Coefficient of variation
C	Control	Sd MV	Standard deviation Mean value or average