Seismic Isolation Bearing with Shear Spring and Sliding Core
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Solution Overview
Problem
Existing isolation bearings face challenges in accommodating large seismic displacements, leading to increased size, cost, and limitations in damping and restoring force capabilities, particularly in high-seismicity regions, where they become overly large and costly, and suffer from issues like high creep and elevation changes affecting structural integrity and rideability.
Innovation Solution
The design incorporates a central sliding bearing core between concave recesses and a circumferential shear spring, with alternating layers of elastomeric and substrate materials, allowing for efficient deformation and providing both damping and restoring forces, while minimizing the footprint and environmental exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If compression springs are used to provide restoring force in sliding bearings, then the bearing can accommodate seismic displacement, but the plan dimension and height of the bearing grow excessively large
Solution Approach 1:
The patent transitions from horizontal spring arrangement to vertical spring arrangement, utilizing the vertical dimension to accommodate spring length while maintaining compact horizontal footprint. The springs are positioned vertically between the base plate and superstructure, allowing large displacement capacity without increasing plan dimension.
Solution Approach 2:
The patent nests the compression springs within the vertical space between the base plate and superstructure, integrating them into the existing bearing assembly rather than adding external horizontal components. This nesting approach allows the springs to be accommodated within the bearing's vertical envelope.
2Length of moving object
If compression springs are used to provide restoring force, then the bearing can accommodate seismic displacement, but the bearing becomes overly costly
Solution Approach 1:
The base plate serves multiple functions: it acts as the mounting surface for the superstructure, provides attachment points for the compression springs, and serves as the reaction surface for friction damping. This multi-functionality eliminates the need for separate components, reducing manufacturing complexity and cost.
Solution Approach 2:
The patent combines the restoring force function and damping function into a single integrated bearing assembly. The friction surface is incorporated directly into the base plate, and the springs are mounted directly to the base plate, merging multiple functions into one compact unit rather than requiring separate assemblies.
3Length of moving object
If long compression springs are used to accommodate large seismic displacement, then the displacement capacity increases, but the spring diameter must be large to maintain adequate spring rate
Solution Approach 1:
The patent reorients the springs from horizontal to vertical arrangement, allowing the spring length to extend in the vertical dimension rather than requiring increased diameter in the horizontal plane. This dimensional reorientation decouples spring length from spring diameter requirements.
4Loss of energy
If sliding bearings with friction elements are used, then damping is provided, but additional means are required to provide restoring spring force
Solution Approach 1:
The base plate is designed to perform multiple functions simultaneously: it provides the friction surface for damping, serves as the mounting structure for springs, and acts as the reaction surface for both friction and spring forces. This eliminates the need for separate restoring force mechanisms.
Solution Approach 2:
The patent merges the damping function and restoring force function into a single integrated system where the base plate serves as both the friction surface and the spring mounting structure, reducing overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces seismic forces and accelerations transferred to structures, enhances damping, and reduces structural elevation changes, providing design flexibility and cost savings by allowing for larger displacements without excessive size or creep issues.
Implementation Method 1
Sliding bearings provide damping to a structure through frictional energy dissipation
Implementation Method 2
Elastomeric bearings provide restoring forces
Implementation Method 3
The shear spring includes alternating layers of an elastomeric material and a substrate material, where the shear spring is configured to deform in shear along the layers of elastomeric material
Data Source
AI summary
The disclosed seismic isolation bearing includes an upper base plate, a lower base plate, a disc bearing core, and a shear spring surrounding the disc bearing core. Concave recesses are formed in a lower surface of the upper base plate and an upper surface of the lower base plate. The disc bearing core is centrally positioned with respect to the planes of the upper and lower base plates and can slide along the recesses of the upper and lower base plates, where the recesses exert a lateral return force on the disc bearing core when displaced from a central position. The shear spring surrounds the disc bearing core, deforms in shear upon lateral movement of the upper base plate relative to the lower base plate, and exerts a lateral return force on the upper base plate when the upper base plate is laterally displaced.