CCEER-99-14: Cyclic Behavior of Steel Moment Frame Connections for the Moscone Center Expansion

Abstract

This report presents the resnlts of an experimental investigation to evaluate the cyclic behavior of moment frame connections for the Moscone Expansion Center. Because of the large story height, Structural Design Engineers, Inc. utilized the concept of Coupled Girder Moment Resisting Framing System. During lateral loads this framing system subjects its girders to axial forces in addition to their end moments. The moment connections used Reduced Beam Section (RBS) to move the inelasticity away from the beam-column joint.

The objectives of the experimental investigation were:

1. Determine the cyclic response of the moment frame connections under axial load and lateral displacement.

2. Evaluate the ultimate strength, rotational ductility and the failure mode of the moment connections.

Four fuil-scale moment connections were subjected to variable axial load (up to 700 kips) and an increasing lateral displacement. The test results showed that the four specimens responded in a ductile way since the plastic rotation exceeded 3% radians without any significant drop in the loading capacity. In addition, these tests showed that the longitudinal stiffener that was added in the middle of the beam web delayed web local buckling and thus increased the plastic rotation.