This paper describes an investigation into the sway of portal frames under a combination of pointloads normal to the ground and with proportionally increasing side loads. A mirror arrangement of two portalframes lying horizontally was tested.During each test three cycles of loading and unloading were performed before the frame was taken to itsultimate load. Initially the bending moments on both beam-to-column joints had the same sign. The percentageof side load applied to the structure was chosen so that due to the non-linear P ?fl effects reversal of bendingmoments occurred in one of the joints during the test. The beam and column components of the framewere numerically modeled using stability functions. The beam-column connections were semi-rigid and theexperimental moment-rotation curves were incorporated into the connection behavior.The agreement between theory and experiment, for all load cases, including the unloading parts of theexperimental cycles was excellent.
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