Partial Confinement Utilization for Rectangular Concrete Columns Subjected to Biaxial Bending and Axial Compression

Ahmed M. Abd El Fattah, Hayder A. Rasheed*, Ahmed H. Al-Rahmani

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value fcc (at zero eccentricity) to the unconfined value fc′ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of P–ε and M–φ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.

Original languageEnglish
Pages (from-to)135-149
Number of pages15
JournalInternational Journal of Concrete Structures and Materials
Issue number1
StatePublished - 1 Mar 2017

Bibliographical note

Publisher Copyright:
© 2017, The Author(s).


  • combined loading
  • eccentricity
  • partial confinement
  • rectangular columns

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Ocean Engineering


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