Seismic Isolation Support Pads With Load-Adaptive Friction Control
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Solution Overview
Problem
Existing seismic isolation devices for structures, such as warehouses, exhibit varying behavior under different load conditions due to changes in friction coefficients between plastic pads and steel surfaces, leading to risks of toppling during earthquakes, especially in tall structures with significant vertical extensions.
Innovation Solution
The seismic isolation device features support legs with polymeric pads that adjust their contact area based on load variations, maintaining a constant average contact pressure and reducing friction coefficient changes, using convex or concave pads made of low-friction materials like UHMWPE, PTFE, or PVDF, and incorporating elastic elements like Belleville spring washers to stabilize the structure across load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If plastic pads with fixed contact area are used, then the device is simple in structure, but the friction coefficient varies significantly with load changes, causing inconsistent seismic isolation behavior
Solution Approach 1:
The support legs incorporate elastic elements (Belleville spring washers) that allow the contact area between the polymeric pad and sliding surface to dynamically adjust based on load variations. This dynamic adaptation maintains consistent average contact pressure and friction coefficient across different load conditions, resolving the contradiction between structural simplicity and seismic isolation consistency.
2Reliability
If the contact area is increased to reduce friction coefficient variability, then the seismic isolation consistency improves, but the device complexity increases
Solution Approach 1:
Rather than increasing contact area statically, the invention uses elastic elements to enable dynamic contact area adjustment. The Belleville spring washers allow the polymeric pad to deform and adapt its contact footprint with the sliding surface according to applied load, maintaining consistent friction characteristics without adding complex mechanical adjustment mechanisms.
Solution Approach 2:
The invention changes the physical state of the support leg by incorporating elastic deformation capability. The polymeric pad deforms elastically under varying loads, changing its contact area and pressure distribution dynamically. This parameter change approach maintains friction coefficient consistency while keeping the structural design relatively simple.
3Stability of the object's composition
If high friction coefficient is used to prevent lateral movements, then the structure stability improves, but the risk of toppling during earthquakes increases
Solution Approach 1:
The invention dynamically adjusts the friction coefficient parameter through elastic deformation of the polymeric pad. By maintaining consistent average contact pressure across varying loads, the friction force adapts appropriately to prevent both excessive lateral movement and toppling, resolving the contradiction between stability and toppling risk.
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 solution effectively minimizes differences in seismic isolation behavior across varying load conditions, reducing the risk of lateral movements and toppling by maintaining a consistent friction force, thus enhancing structural stability during transverse accelerations.
Implementation Method 1
Each support leg (2) is fastened to the lower part of the structure (1) and comprises at least a support element or pad which is adapted to rest on a sliding surface (3) with a deformation
Implementation Method 2
incorporating elastic elements like Belleville spring washers to stabilize the structure across load conditions
Implementation Method 3
The friction coefficient between the plastic materials and steel is affected by the suspended mass and depends considerably on the average contact pressure between the pad and the sliding surface
Data Source
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AI summary
A seismic isolation device for structures of the type in which the structure to be isolated is provided with at least one support leg (2) is constrained to the same structure, includes at least a support element or pad adapted to rest on a sliding surface (3) with a deformation, and includes a contact area in contact with said sliding surface (3) whose extension is variable and depends on the load resting on the support. The sliding surface (3) is rigid and the contact area in contact therewith has a variable extension and depends on the load resting on the support.