Reliability Assessment of Reinforced

    Concrete Column under Axial-Flexural


    Ji Hyeon Kim



Bridge design concepts have been changed from Allowable Stress Design (ASD) method based on empirical design to Load and Resistance Factor Design (LRFD) method based on the probabilistic and statistical design. LRFD design method sug-gests a target reliability level based on reliability assessment which applies proba-bilistic and statistical information of the design variables.

   For RC column reliability, it is impossible to assess the reliability index. Because the RC column have been designed by Ultimate Strength Design method. So, we can only figure out that whether the structure is safe or fail.

   There are many researches to assess the reliability index of RC column.

   The Column is the member which sustains the axial loading. But it could be under the flexural loading which caused by the construction error and eccentricity. Therefore, the reliability analysis which can consider the failure modes by both axial and flexural loading must be needed.

   Many of research suggest the reliability analysis method using P-M Interaction diagram to consider two failure modes. There is a characteristic that a structure could be safe under the external load which is inside the diagram. If the outside load of diagram is loaded, the structure could be destroyed. Form a reliability as-sessment point of view, P-M interaction diagram means limit state of the structure. Using this concept, many researchers have studied the reliability analysis of column members. But those studies restrict a range of Most Probable Failure Point or define the only probable failure point.

   In this study, a new reliability analysis method of RC column is proposed which considers all points of the interaction diagram as a probable failure point. To verify the method, this study compares the results with that of MCS. And it is shown that the failure mode occurs differently because of the various load random variables.

   Reliability results obtained by the proposed method could be a basis of a proper reliability level for LRFD method.


Key Word

PM Interaction Diagram, Reliability Analysis, FORM, Cubic Spline Interpolation, Limit state function


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