Bi-Metallic Connector for Mass Timber Shear Walls
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Solution Overview
Problem
Current connectors used in mass timber panel-based buildings are not capable of handling reversed cyclic load deformations associated with seismic events and high wind loads, lacking the necessary ductility and energy dissipation capacity to ensure acceptable performance in high seismic regions.
Innovation Solution
A connector designed to connect mass timber shear wall panels, featuring high initial stiffness for low and moderate seismic events, transitioning to low stiffness at a defined load for increased displacement capacity, with a hysteretic load-deflection curve to maximize energy dissipation and prevent metal fatigue or buckling, and featuring interlocking shear keys and tapered steel plates for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard hardware bolt, nail, or screw-type connectors are used in mass timber panels, then the construction process is simple and fast, but the connectors cannot handle reversed cyclic load deformations associated with earthquakes and high wind loads
Solution Approach 1:
The connector employs a bi-metallic strip mechanism that dynamically changes its mechanical properties based on applied load. Under normal service loads, the connector maintains high stiffness for structural integrity. Under reversed cyclic loads exceeding a threshold, the bi-metallic strip undergoes phase change or deformation that transitions the connector to a more flexible state, allowing it to accommodate cyclic deformations without failure. This dynamic adaptation resolves the contradiction by enabling the simple connector design to achieve reliable seismic performance through material-level intelligence rather than complex structural arrangements.
Solution Approach 2:
The connector utilizes temperature-dependent or stress-dependent material properties of bi-metallic strips to change its mechanical parameters. The bi-metallic construction causes differential expansion or deformation under thermal or mechanical stress, which triggers a transition in the connector's stiffness characteristics. This parameter change allows the same simple connector structure to provide both rigid connection under service conditions and flexible deformation capacity under seismic loading, resolving the contradiction between structural rigidity and seismic ductility.
2Productivity
If mass timber panels are used to accelerate construction timeline, then construction speed increases, but the lack of qualified inter-panel connectors for high seismic regions limits performance
Solution Approach 1:
The bi-metallic strip connector is designed to automatically adjust its mechanical behavior in response to loading conditions without external intervention. Under seismic loading, the connector self-transitions from a rigid to a flexible state through inherent material properties, providing the necessary ductility and energy dissipation. This self-service capability allows the connector to qualify for high seismic regions while maintaining the simplicity and speed of mass timber construction, resolving the contradiction between rapid construction and seismic reliability.
3Reliability
If connectors with high ductility and energy dissipation capacity are designed, then seismic performance improves, but installation complexity and time increase
Solution Approach 1:
The connector employs bi-metallic strip construction, combining two different metal materials with complementary properties. One metal provides strength and rigidity, while the other provides ductility and energy dissipation capacity. This composite material approach achieves high energy dissipation capacity through the inherent material characteristics rather than complex geometries or multiple components, maintaining installation simplicity while improving seismic performance.
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 connector effectively minimizes wall racking displacement during seismic events, allows for easy installation and replacement, and provides stable energy dissipation, ensuring the building's structural integrity and ease of repair in high seismic regions.
Implementation Method 1
the connector has high initial stiffness to minimize wall racking displacement under low and moderate intensity earthquakes
Implementation Method 2
the connector achieves a low stiffness plastic state which allows each individual wall panel to rotate (rock) about a respective base point
Implementation Method 3
When subjected to actions from design (Building Code Level), Risk-Targeted Maximum Considered Earthquake (MCER) events, or ultimate wind events, the connector achieves a low stiffness plastic state which allows each individual wall panel to rotate (rock) about a respective base point
Data Source
AI summary
An apparatus to connect two mass timber (CLT, LVL, or other configurations) shear wall panels, comprising a high load deformation capacity steel connector, wherein the connector comprises a high stiffness that shifts to a low stiffness during a high intensity earthquake or significant wind loading event.