Earthquake Simulation Tests of a Nine Story Steel Frame with Columns Allowed to Uplift,

摘要

The computed lateral loading imposed on a structure during a major earthquake will often produce an overturning moment in excess of the dead-weight overturning resistance of the system. Assuming that no supplementary anchorage capacity is provided,this condition implies a transient uplift of the structure from its foundation. Linear structural dynamic analysis techniques are not capable of treating this type of highly nonlinear response. This thesis presents experimental and analytical response data for a model nine-story building frame under seismic excitation,both with and without supplementary anchorage of the columns provided. The experimental work was carried out on the shaking table of the U.C. Berkeley Earthquake Simulator Laboratory. Appreciable amounts of column uplift were observed in the tests for which column uplift was permitted,with significant reductions in the lateral loading,when compared to the fixed base response. An analytical technique employing bilinear foundation support elements with zero tensile capacity and stiffness in the upward direction is shown to predict the uplifting response with excellent accuracy. Analytical predictions of the nonlinear fixed base response,employing concentrated bilinear plastic hinges are also shown to be very accurate for the levels of nonlinearity encountered.