Structural Behavior and Low Cycle Fatigue Characteristics of Suspension Support Member for Building Equipment

The installation method for earthquake-resistant support of suspension equipment such as air-conditioners is generally to connect braces to the hanging bolts via mounting hardware. However, it has been reported that hanging bolt, which is one of the members supporting suspension equipment (suspension support members), has been cyclically deformed during earthquakes, resulting in fractures at the suspension source. The fall of the equipment due to the fracture of suspension support members is a serious damage that directly leads to the loss of building functions. In this study, Cyclic loading tests were conducted to investigate the structural behavior and low cycle fatigue (LCF) characteristics of suspension support members. The test specimens consist of four hanging bolts, each side of which is reinforced by X-shaped braces. The main test parameters are the suspension length and the angle of the brace. Cyclic loading applying the forced deformation to the suspension side of the hanging bolts was conducted until either the hanging bolt fracture or significant damage in other parts of the specimens. In evaluating the initial stiffness and the yield strength of the suspension support members, considering the effect of the mounting hardware, both were evaluated well under the current recommended specifications for seismic support. And then, the test result showed that the LCF characteristics of suspension support members can be evaluated by using the deformation angle at the protrusion, regardless of the presence or absence of bracing.