Mau (1990) performed a parametric study to establish

Mau (1990) developed Finite Element Model to study inelastic
buckling and load-carrying capacity of reinforcing steels in concrete columns. They
stated that critical spacing is dependent on the stress-strain curve of steel
reinforcement. In addition, Mau (1990) performed a parametric study to
establish the critical spacing range for typical high-strength steel.

Analytical Studies

Lin and Niu (2015) analyzed the influence laws of buckling
loads and buckling models of corroded steel bars caused by different
slenderness ratios, corrosion pit diameters, corrosion pit locations and
relative depth of corrosion pits. They concluded that slenderness ratios and
corrosion pit diameters are the main factors influencing the corroded steel bar
buckling loads.

Urmson and Mander (2012) proposed a simple model for the compression
behavior of longitudinal reinforcing steel in engineering stress-strain
coordinates. They stated that since they are computationally intensive,
existing models are not practical for designing. Moreover, other models are
either built based on simplified assumptions about plastic behavior of steel or
have a high degree of built-in empiricism.

Bae et al. (2005)
performed an analytical study to develop a constitutive model to investigate
the behavior of steel reinforcing bars under compression. The model accounts
for material properties as well geometry of the cross-section. They concluded
that for reinforcing bars with L/d=4,
regardless of the e/d ratio, the
load-carrying capacity was maintained while specimens experienced large
inelastic deformations. They also suggested when reinforcement bars are
expected to undergo large inelastic deformations, L/d ratios greater than 6 should be avoided.

et al. (1994) suggested that the reduction
in the cross-section’s effective depth due to the concrete spalling on the
compression side will increase depth of the neutral axis to maintain
equilibrium. In addition, they suggested that buckling load of the compression
bars could be calculated using the Euler buckling equation. The application of
this equation requires the end fixities to be known. They suggested that when
concrete cover spalls and the stirrups corrode, the corroded compression
reinforcement can be considered as a pin-ended strut (Webster 2010).