Exploring Different Configurations of Wire Ropes Supporting Slender Equipment to Minimize

Sunday, February 14, 2016
Aniurka Duverge Carreno, Howard University, Washington, DC
Earthquakes can damage not only buildings, but also their sensitive components. These sensitive components include hospital equipment, data servers, and communication equipment among others. Electronic equipment can be damaged by the accelerations and rocking caused by an earthquake. When an earthquake happens, this type of equipment could malfunction and the habilitation process may require time, which is lacking in an emergency. Therefore, it is important to define seismic protective measures of equipment and building contents. Seismic isolating platforms can prevent failure and damage on equipment by mitigating the effects of earthquake on the equipment. Implementing seismic isolation platforms for the protection of slender equipment brings the challenge of rocking control, which can also be damaging to the equipment. The experimental and theoretical studies on this project explore different configurations of wire ropes for rocking control of slender equipment. Rocking is cause in part by the eccentricity between the center of mass of the equipment and the center of stiffness of the isolation platforms. In this study, different configurations of wire ropes intend to reduce/minimize that eccentricity to control rocking. Evidence from earthquake simulation studies in this project using an isolating platform built with wire ropes installed in shear/roll and at an angle of 45o and sandwiched between steel plates proved that rocking can be controlled by minimizing the distance between the center of mass of the equipment and the center of stiffness/line of action of the wire rope of the platforms. The experimental results evidenced rocking through positive rotational stiffness for the shear/roll platform, while the 45 degree compression/shear/roll platform evidenced negative rocking through negative rotational stiffness. This difference on the rotational stiffness of these two systems indicates that rocking can be neutralized by defining a wire rope configuration that eliminates/minimizes the distance between the plate’s center of mass and the center of stiffness of the platform. Preliminary data from numerical studies using numerical models via SAP2000 also evidenced that rocking can be controlled by placing the wire ropes at an angle to both increase the line of action of the wire ropes and reduce the eccentricity.  The experimental and numerical responses of the simulation in this study provided positive performance of the wire ropes to control seismic rocking on slender equipment. Wire ropes can be configured to control seismic rocking and can be used to protect equipment from malfunction in the event of an earthquake. Loss of data and equipment malfunction can be prevented utilizing this approach. Favorable results inspire future research opportunities which will enhance the current state of knowledge of the seismic isolating technology.