Resilient Slip Friction Joint for Seismic Self-Centring
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Solution Overview
Problem
Existing slip friction joints in buildings lack self-centring capability, requiring additional systems to restore structures to their original position after seismic events, which is costly and results in undesirable residual displacement, such as jammed lifts and non-functional doors, due to the lack of energy dissipation and positional biasing.
Innovation Solution
A resilient slip friction joint with oblique ramped surfaces and resilient fixers that allow relative movement and resist friction, enabling partial or complete return to the equilibrium position, using a connector system with ramped surfaces and biasing members like Belleville washers or springs to overcome static friction and restore the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If simple flat steel plates sliding over each other are used for slip friction joints, then energy dissipation is achieved, but residual displacement occurs and self-centring capability is lost
Solution Approach 1:
The patent replaces flat sliding surfaces with curved ramped surfaces that guide the sliding motion. The curved geometry of the ramps ensures that after seismic displacement, the components follow a return path toward the original position, enabling self-centring while maintaining energy dissipation through friction.
Solution Approach 2:
The ramped surfaces are designed with asymmetric profiles where the sliding path during seismic event differs from the return path. This asymmetry allows the joint to dissipate energy in one direction while providing a geometric bias that promotes return to the original position, resolving the contradiction between energy dissipation and residual displacement.
2Loss of energy
If friction between plates is increased to resist movement, then energy dissipation improves, but self-centring capability deteriorates
Solution Approach 1:
The curved ramped surfaces create a geometric mechanism where the normal force direction changes during sliding. This curvature ensures that even with high friction, the component geometry guides the plates back toward the original position, maintaining self-centring capability while allowing sufficient friction for energy dissipation.
Solution Approach 2:
The ramped surfaces are pre-configured with specific angles and curvatures that anticipate the seismic displacement direction. This preliminary geometric arrangement ensures that after frictional sliding occurs, the geometry itself provides the restoring mechanism, allowing high friction without sacrificing self-centring.
3Strength
If rigid connections are used between floor plates and shear walls, then structural integrity is maintained, but bending moment and torsional loading increase during seismic events
Solution Approach 1:
The patent transforms the rigid static connection into a dynamic slip-friction connection with curved ramps. During seismic events, the connection allows controlled sliding along the ramped surfaces, converting part of the seismic energy into frictional heat while reducing the transmission of bending moments and torsional loads to the connected members.
Solution Approach 2:
The connection parameters are changed from rigid fixed boundaries to flexible slip surfaces with specific friction coefficients and ramp angles. This parameter change allows the joint to adapt during seismic loading, maintaining structural integrity through friction while reducing peak forces through controlled displacement.
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
The solution effectively dissipates seismic energy, reduces residual displacement, and self-centres the structure, minimizing damage and maintenance costs by allowing the structure to return to its original position after an earthquake, ensuring safety and functionality.
Implementation Method 1
at least one resilient fixer to hold the components with mutually slidable ramped surfaces together such that relative movement of the ramped surfaces may be frictionally resisted
Implementation Method 2
relative movement of the ramped surfaces may be frictionally resisted
Implementation Method 3
the ramped surfaces are oblique to the line or lines of action of the at least one resilient fixer such that the connector causes an at least partial return of relative sliding movement of the ramped surfaces of the first and second components
Data Source
Figure 1a~2a
Figure 2b~3b
Figure 3c~3d
AI summary
A slip connector to connect first and second members of a structure to allow relative but resisted movement, and to at least in part return any movement. The connector includes a first component and second component, each with mutually slidable ramped surfaces contiguous. The first and second components are connectable to the respective first and second members of the structure, and there is at least one resilient fixer to hold the two components contiguous so that the line(s) of action of the fixer(s) is/are oblique to the slidable surfaces held contiguous.