Strength and Behavior of an Inelastic Hybrid Frame

A test of a single-story, single-bay frame was performed as part of a program to investigate the behavior of multistory frames. The frame consisted of two ASTM-A441 columns rigidly connected to an ASTM-A36 beam and was subjected to combined vertical and horizontal loads. The frame was so designed that the effect of secondary moments produced by axial forces acting through sway displacements could be observed experimentally. The test also furnished important information concerning the behavior of the high-strength steel columns. The experimental results are compared with predicted values obtained from an elastic-plastic analysis, which accounts for the secondary moments in the frame, the axial loads in the columns, and the increased strength provided by the beam-to-column connections. In addition, in predicting the post-mechanism behavior, the influence of strain hardening is included in a rational, yet simple manner. The theory developed closely predicts the response of the test frame.