The Earthquake Engineering Online Archive

Cyclic plastic analysis of structural steel joints

Pinkney, R. Bruce

UCB/EERC-73/15, Earthquake Engineering Research Center, University of California, Berkeley, 1973-08, 155 pages (530/P483/1973)

Severe lateral loading of an unbraced building frame due to high winds or earthquake can induce cyclic inelastic stress reversal in its component parts, particularly the joints between beams and columns. Accurate frame analysis thus requires a knowledge of joint behavior beyond the elastic range. The purpose of this study was to investigate a method of analytically predicting the cyclic inelastic response of a structural steel joint. A three-dimensional solid finite element formulation was used to model the joint. The global equilibrium equations were assembled and solved using a substructuring approach, which permitted easy modification of the model. The incremental theory of plasticity was used, incorporating the von Mises yield criterion; the kinematic hardening rule of Prager was included to account for the Bauschinger effect present in steel. Two different mesh refinements were tried, as well as various load step sizes. Both stiffened and unstiffened joints were analyzed. The prediction of response during initial yielding appears to be reasonably accurate. Prediction of response following reversal of load suggests that a more refined estimate of cyclic inelastic material behavior should be incorporated into the theory. Although the scope of the investigation did not include prediction of fatigue life, the results indicate that such prediction may be possible on the basis of the type of analysis reported.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-73-15.pdf (9 MB)