Major and Minor Axis Stiffness Reduction of Steel Beam-Columns Under Axial Compression and Tension Conditions

For compact W-Shapes with an ECCS residual stress distribution pattern, the stiffness reduction that results from yielding of the cross-section due to uniaxial bending and axial loading are studied in detail. Major and minor axis bending under axial compression and tension conditions are investigated. Three-dimensional m-p- surface plots of a W8x31 are used to discuss the stress states around the perimeter of the surfaces and the reduced stiffness for each of the loading conditions. Figures are provided for the stiffness reduction from initial yield up to the fully plastic conditions for the axial compression and axial tension conditions. The m-p- surface plots are used to develop an idealized material model for direct implementation in MASTAN2. The El-Zanaty and Kanchanalai benchmark frames are modeled using the new material model. The results compare very closely with published results of the same frames under similar loading conditions. Discussion is provided regarding the proposed material model for practical use.

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