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Mid-America Transportation Center

KDOT Column Expert: Ultimate Shear Capacity of Circular Columns using the Modified Compression Field Theory


Researchers

  • Principal Investigator: Hayder Rasheed
  • Project Status
    In Progress
    About this Project
    Brief Project Description & Background
    For confined sections subjected to combined axial force and uniaxial bending moment, the actual ultimate flexural capacity is found using the earlier versions of KDOT Column Expert. Accordingly, it is necessary to develop a computer program that evaluates the section capacity in shear by generating accurate shear-moment interaction diagrams for each level of axial force and compares them to the available experimental results. This analysis can prove useful to estimate the existing capacity of damaged bridge piers when subjected to truck impacts. It is also desirable to have a reliable analysis tool that can be used to assess the actual shear capacity of the pier when developing a repair action. Experimental evidences have shown that the modified compression field theory can capture the actual shear capacity of the section very accurately. In addition, the dowel action of the longitudinal bars acting in tension can contribute to increasing the shear capacity, a factor often neglected by design codes of practice.
    Research Objective
    The objective of the proposed research is to develop a detailed analysis procedure that can be used by KDOT as an effective analysis and design tool to determine the actual ultimate shear capacity of reinforced concrete circular columns subjected to axial force and uniaxial bending moment simultaneously.
    Potential Benefits
    The study will yield software that will be used by KDOT and is expected to be used by FHWA and other State DOT’s for extreme load event analysis of concrete bridge piers. It will also help to provide a reliable tool to analyze for actual shear capacity of circular columns with and without the combined axial force and bending moment. The newly developed theory for circular cross sections and methodology for the incremental computations of combined loading will be publishable in the open literature.
    Abstract
    The extreme event requirement as a limit state set by AASHTO LRFD makes it necessary to develop the actual capacity of concrete sections to accurately design them to withstand extreme load events. For confined sections subjected to combined axial force and uniaxial bending moment, the actual ultimate flexural capacity is found using the earlier versions of KDOT Column Expert. Accordingly, it is necessary to develop a computer program that evaluates the section capacity in shear by generating accurate shear-moment interaction diagrams for each level of axial force and compares them to the available experimental results. This analysis can prove useful to estimate the existing capacity of damaged bridge piers when subjected to truck impacts. It is also desirable to have a reliable analysis tool that can be used to assess the actual shear capacity of the pier when developing a repair action. Experimental evidences have shown that the modified compression field theory can capture the actual shear capacity of the section very accurately. In addition, the dowel action of the longitudinal bars acting in tension can contribute to increasing the shear capacity, a factor often neglected by design codes of practice. The nonlinear axial load-strain and uniaxial moment-curvature response of reinforced concrete circular section combined with shear forces is very involved. It is important to note that accurate results are guaranteed when the axial load and bending moments are proportional since loading path dependence is avoided. Rasheed and Abd El Fattah have developed a framework for columns that imposes proportional axial force and uniaxial bending moment on circular sections and iterates to obtain the corresponding deformation parameters. However, this procedure needs to be extended to the general case of shear-moment-axial force interaction.
    Project Amount
    $ $59,720