I am preparing moment curvature relationship for Columns and beams for nonlinear static analysis (Pushover). And for columns the yield moment is larger than the ultimate moment. So I am confused if it is correct or not. Is it possible to have Ultimate moment which is less than the yield moment? or Is is possible to idealize the curve by taking yield moment and ultimate moment to be equal?
For your information, I have also checked the curves I prepared using Sap 2000 section designer and response 2000. And the result is the same. Yield moment is greater than ultimate moment.
Ultimate moment is always bigger than Yield moment but for simple beam (SB) they might be equal.
In sap2000 this could be due to the way the stress strain curve of steel is defined
this article can help you
Moment–curvature–thrust relationships (M–κ–N) are a useful resource for the solution of a variety of inelastic
and geometrically non-linear structural problems involving elements under combined axial load and bending. A
numerical discretised cross-section method is used in this research to generate such relationships for I-sections,
rectangular box-sections and circular or elliptical hollow sections. The method is strain driven, with the
maximum strain limited by an a priori defined local buckling strain, which can occur above or below the yield
strain depending on the local slenderness of the cross-section. The relationship between the limiting strain and
the local slenderness has been given for aluminium, mild steel and stainless steel cross-sections through the base
curve of the Continuous Strength Method. Moment-curvature-thrust curves are derived from axial force and
bending moment interaction curves by pairing the curvatures and moments for a given axial load level. These
moment–curvature–thrust curves can be transformed into various formats to solve a variety of structural
problems. The gradient of the curves is used to find the materially and geometrically non-linear solution of an
example beam-column, by solving numerically the moment–curvature ordinary differential equations. The
results capture the importance of the second order effects, particularly with regard to the plastic hinge formation
at mid-height and the post-peak unloading response.
Respected researchers
I have developed moment curvature plot for bridge columns retrofitted with carbon composites and steel jacket.
My question is how to idealize moment curvature plot to get yield curvature and yield moment.
Thanks
Sai
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