Development and application of negative stiffness devices for seismic response control of highway bridge structures.

摘要

A new control device has been developed and implemented for seismic response control of highway bridges. The device produces negative stiffness in a completely passive manner via a mechanical mechanism. Numerical simulations and experimental shaking table tests have demonstrated the effectiveness of the device in limiting the seismic demands on bridge structures. The main feature of the negative stiffness device is a pre-compressed spring, which can push the structure away from its center position and thus induce negative stiffness. When implemented in parallel with a structure having positive stiffness, the combined system appears to have substantially reduced stiffness while remaining stable. Thus, there is an "apparent weakening" of the structure that results in a "virtual yielding point," reduced forces and increased displacements. The increase in displacement response can be limited by incorporating a damping device in parallel with the negative stiffness device or by adding friction to the device assembly.;In this dissertation, the negative stiffness devices are described along with their hysteretic behavior as obtained from a series of cyclic tests which were utilized to calibrate the parameters of a numerical model. In addition, results from numerical simulations and seismic testing of a quarter-scale bridge model are presented wherein the bridge was configured with various isolation system components (isolation bearings, negative stiffness devices, and viscous dampers). In addition, the bridge was designed to mimic either a single-span bridge supported on abutments or an interior span of a multi-span bridge. The results of the investigation clearly demonstrate the effectiveness of the negative stiffness devices in limiting the seismic response of the bridge for multiple bridge configurations. Furthermore, motivated by the need for a more compact device, the development phase of the project led to a new concept for creating negative stiffness wherein translational motion of the bridge is transformed to rotational motion. The conceptual development of the device is presented along with analytical models and numerical simulation results that demonstrate its ability to provide superior seismic protection.