Testing facility for frame subassemblages

Abstract

The structural-steel rigid frame is the most widely used type of construction for high-rise buildings in the seismically active zones of the United States. During a strong ground motion, such frames are subjected to repeated and reversed lateral loading of considerable intensity, resulting in not fully understood inelastic response. A typical element for this type of construction may be idealized by a statically indeterminate assemblage of one or two horizontal beams rigidly connected to a vertical column which extends to its points of inflection above and below the joint. A facility for testing such an assemblage has been developed in which a large axial load can be applied to the column simultaneously with additional loads on the beams. A provision is also made for simulating quasi-statically the effect of the horizontal inertia forces induced by an earthquake. This is done by moving the base of the loaded column back and forth. In order to perform meaningful experiments with this facility, specialized instrumentation had to be designed and built. This consisted of a number of transducers including a unique shear transducer, and special gages for measuring displacements and rotations. In this paper, after a brief general description of the testing facility, emphasis is placed on describing the special features of the designed instrumentation, as well as the high precision photogrammetric and geodetic techniques that are used to measure deformations.