AFRP	Aramid fiber-reinforced polymer
CC	Chaos control
CCC	Chaotic conjugate control
CFORM	Conjugate first-order reliability method
CFRP	Carbon fiber-reinforced polymer
CHL-RF	Conjugate Hasofer-Lind and Rackwitz-Fiessler method
COV	Coefficients of variation
DSTM	Directional stability transformation method
FORM	First-order reliability method
FR	Fletcher and Reeves
FRP	Fiber-reinforced polymer
FSL	Finite-step length method
GFRP	Glass fiber-reinforced polymer
HL-RF	Hasofer-Lind and Rackwitz-Fiessler method
HSC	High strength concrete
IHL-RF	Improved Hasofer-Lind and Rackwitz-Fiessler method
LFR	Limited Fletcher and Reeves
MCS	Monte Carlo simulation
MPP	Most probable point
NSC	Normal strength concrete
PDF	Probability distribution function
SORM	Second-order reliability method
STM	Stability transformation method
a	Chaos scalar factor
g	Distributed load
l	Length of truss
C	Involutory matrix
D	Diameter of concrete specimen
E	Young’s modulus
H	Height of concrete specimen
P	Concentric load
$U$	Normal standard random variables vector
X	Original random variable vector
As	Cross sectional areas of steel bars
c 1	Adjusted factor
dk	Conjugate search direction vector
d($U$k)	Point-based conjugate search direction
Ec	Elastic modulus of reinforced concrete
Ef	Elastic modulus of fibers used in FRP jacket
Es	Elastic modulus of steel bars
$f_{lo}$	Threshold confining pressure
flu,a	Actual confining pressure
fX	Joint probability density function
g(X)	Limit state function
g(X) ≤ 0	Failure region
$K_l$	Confinement stiffness of the FRP shell
Pf	Failure probability
tf	Total thickness of fibers used in FRP jacket
f′cc	Concrete ultimate compressive strength
f′co	Unconfined concrete strength
U*	Most probable point (MPP) in U-space
$\alpha$ k+1	Unit normal vector
${\alpha }_{k+1}^C$	Conjugate unit normal vector at design point $U$k
β	Reliability index
λ	Finite-step length
δ	Limited conjugate factor
σ	Standard deviation
μ	Mean
εco	Axial strain corresponding to the f′co
εcu	Ultimate axial strain
εf	Ultimate tensile strength of fibers used in FRP jacket
εh,rup	Hoop rupture strain of the FRP
κf	Model error for ultimate strength
${\kappa }_{\epsilon }$	Model error for ultimate strain
Φ	Standard normal cumulative distribution function
${\Delta }_{}^z$	Maximum displacement at z-direction
$\nabla g\left(U\right)$	Gradient vector of the limit state function at point $U$