Optimal design of seismic isolators for museum artifacts

Abstract eng:
In earthquake prone areas, museum artifacts of medium weight may be seismically isolated using lightweight isolators, specially developed for this purpose. These isolators consist of three plates, one on the top of the other. The bottom plate is anchored to the floor and the two others slide on frictionless rails mounted at the bottom plate, in two mutually orthogonal directions. Every upper plate is connected with its lower one with a system of elastic springs and viscous dampers. The artifact is anchored at the top plate and the dynamic behavior of the entire system is determined as two uncoupled single degree of freedom systems along the two mutually orthogonal directions. Within this category of isolators a new type of lightweight isolator is proposed that provides a cubic order restoring force and quadratic damping. In the proposed isolator, the springs are placed perpendicular to the direction of motion with the one tip moving along a parabola. This results into a system of two uncoupled oscillators, the non-linear behaviour of which is determined by a Duffing - Van der Pol type of equation. For a specific artifact of certain weight, the optimal parameters of the parabola, as well as the stiffness and damping characteristics, can be determined by first deciding the maximum allowable displacement of the system and then seeking for the minimization of the acceleration transmitted to the artifact. This is accomplished by minimizing the kinetic energy of the system for a given set of earthquake excitations that correspond to the seismic hazard analysis of the particular site. Sequential quadratic programming (SQP) methods are used to guide the optimization process. Numerical examples are presented for specific artifacts that demonstrate the effectiveness of the proposed isolator.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket