Nonlinear Finite Element Modeling of Unbonded Steel Reinforced Concrete Beams

In this paper, a nonlinear Finite Element Analysis
(FEA) was carried out using ANSYS software to build a model able
of predicting the behavior of Reinforced Concrete (RC) beams with
unbonded reinforcement. The FEA model was compared to existing
experimental data by other researchers. The existing experimental
data consisted of 16 beams that varied from structurally sound beams
to beams with unbonded reinforcement with different unbonded
lengths and reinforcement ratios. The model was able to predict the
ultimate flexural strength, load-deflection curve, and crack pattern of
concrete beams with unbonded reinforcement. It was concluded that
when the when the unbonded length is less than 45% of the span,
there will be no decrease in the ultimate flexural strength due to the
loss of bond between the steel reinforcement and the surrounding
concrete regardless of the reinforcement ratio. Moreover, when the
reinforcement ratio is relatively low, there will be no decrease in
ultimate flexural strength regardless of the length of unbond.

• Fares Jnaid
• Riyad Aboutaha

• FEA
• ANSYS
• Unbond
• Strain.

[1] Eyre, J. R., and Nokhasteh, M. A. (1992). “Strength Assessment of
Corrosion Damaged Reinforced Concrete Slabs and Beams.”
Proceedings of the Institution of Civil Engineers, Structures and
Buildings, 94(2), 197-203.
[2] Minkarah, I., and Ringo, B. C. (1981). “Behavior and repair of
deteriorated reinforced concrete beams.” University of Cincinnati, Ohio,
Transportation Research Record, 73-79.
[3] Smith, D. N., and Wood, L. A. (1989). “The structural performance of
damaged elements,” Proceedings of the International Seminar on The
Life of Structures, The Role of Physical Testing, Brighton.
[4] Cairns, J., and Zhao, Z. (1993). “Behavior of concrete beams with
exposed reinforcement.” Proceedings of the Institution of Civil
Engineers: structures and Buildings, 99(2), 141-154.
[5] Raoof, M., and Lin, Z. (1997). “Structural characteristics of RC beams
with exposed main steel.” Proceedings of the Institution of Civil
Engineers: structures and Buildings, 122(1), 35-51.
[6] Sharaf, H., and Soudki, K. (2002). “Strength Assessment of Reinforced
Concrete Beams with Unbonded Reinforcement and Confinement with
CFRP Wraps.” 4th Structural Specialty Conference of the Canadian
Society for Civil Engineering, Montreal, Quebec, Canada, 1-10.
[7] Nokhasteh, M. A., Eyre, J. R., and Mcleish, A. (1992). “The effect of
reinforcement corrosion on the strength of reinforced concrete
members.” Structural Integrity Assessment, P. Stanley, ed., Elsevier
Applied Science, London, England, 314–325.
[8] Lundgren, K. (2005). “Bond between ribbed bars and concrete. Part 1:
Modified model.” Magazine of Concrete Research, 57(7), 371-382.
[9] Lundgren, K. (2005). “Bond between ribbed bars and concrete. Part 2:
The effect of corrosion.” Magazine of Concrete Research, 57(7), 383-
396.
[10] Lundgren, K. (2007). “Effect of corrosion on the bond between steel and
concrete: an overview.” Magazine of Concrete Research, 59(6), 447-
461.
[11] Xiaoming, Y., and Hongqian, Z. (2012). “Finite Element Investigation
on Load Carrying Capacity of Corroded RC Beam Based on Bond-Slip.”
Jordan Journal of Civil Engineering, 6(1), 134-146.
[12] ANSYS 13.0, “Help Manual.” ANSYS, Inc., Canonsburg, Pennsylvania.
[13] Willam, K.J., and Warnke, E.P. (1974). “Constitutive Model for Triaxial
Behavior of Concrete.” Seminar on Concrete Structures Subjected to
Triaxial Stresses, International Association of Bridge and Structural
Engineering Conference, Bergamo, Italy.
[14] Kachlakev, D.I., Miller, T., Yim, S., Chansawat, K., and Potisuk, T.
(2001). “Finite Element Modeling of Reinforced Concrete Structures
Strengthened With FRP Laminates.” California Polytechnic State
University, San Luis Obispo, CA and Oregon State University,
Corvallis, OR for Oregon Department of Transportation.
[15] Wolanski, A.J. (2004). “Flexural behaviour of reinforced and prestressed
concrete beams using finite element analysis.” M.S. thesis, Marquette
University, Milwaukee, WI.
[16] Dahmani, L., Khennane, A., and Kaci, S. (2010). “Crack Identification
in Reinforced Concrete Beams using Ansys Software.” Strength of
Materials, 42(2), 232-240.
[17] Jnaid, F., and Aboutaha, R. S. (2014). "Residual Flexural Strength of RC
Beams with Unbonded Reinforcement," ACI Structural Journal, 111(6),
1419-1430.
[18] ACI 318-11 (2011). “Building Code Requirements for Structural
Concrete (ACI 318-11) and Commentary.” ACI 318R-11, American
Concrete Institute, MI, USA.