Self-Centering Brace with Elongated Tension Elements
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Solution Overview
Problem
Self-centering systems in earthquake-resistant building designs face challenges in configuring geometry to prevent elastic restoring force elements from exceeding yield strain, particularly with materials like steel, and in managing energy dissipation and structural integrity during seismic events.
Innovation Solution
The implementation of an elongated tension-only brace with elastic restoring force elements that have effective lengths greater than the minimum required, utilizing pulley systems to increase the stretch length without yielding, and incorporating metallic yielding devices for energy dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the restoring force elements are made with sufficient strength to provide adequate restoring force, then the building can return to its original position, but the elements may exceed yield strain under seismic loading
Solution Approach 1:
The restoring force system is segmented into multiple parallel elastic elements (tension members) rather than relying on a single element. This segmentation allows the system to distribute seismic loads across multiple components, reducing the strain on individual elements while maintaining sufficient restoring force capacity. The parallel arrangement ensures that no single element exceeds yield strain even under severe seismic events.
Solution Approach 2:
The patent changes the geometric parameters of the elastic elements, specifically increasing the length of tension members and adjusting the configuration of compression members. By modifying these dimensional parameters, the system achieves adequate restoring force while keeping strain levels within elastic limits. The extended tension members and optimized compression member geometry allow the system to provide necessary restoring force without exceeding material yield strains.
2Force
If the geometry of the self-centering system is configured to provide adequate restoring force, then the building can return to its original position, but the strain on elastic elements increases
Solution Approach 1:
The patent employs a dynamic geometric configuration where the brace members can rotate and extend during seismic events. The compression members are designed to rotate about their ends, and the tension members can extend beyond their original length, allowing the system to adapt its geometry in real-time. This dynamic behavior enables the structure to maintain adequate restoring force while reducing peak strains on elastic elements through geometric transformation.
Solution Approach 2:
The patent introduces additional degrees of freedom by allowing rotation in multiple dimensions. The compression members rotate about their ends in a planar motion, while the tension members can extend and retract along the brace axis. This multi-dimensional movement capability allows the system to achieve the necessary restoring force through geometric transformation rather than solely through elastic deformation, thereby reducing strain on individual elements.
3Loss of energy
If metallic yielding devices are added for energy dissipation, then seismic energy can be dissipated, but the device complexity increases
Solution Approach 1:
The patent merges the energy dissipation function with the existing self-centering brace members. The compression members and tension members are designed to perform both structural support and energy dissipation functions. During seismic events, the compression members rotate and the tension members extend, dissipating energy through controlled deformation while maintaining the self-centering capability. This integration eliminates the need for separate energy dissipation devices, reducing overall system complexity.
Solution Approach 2:
The brace members are designed with multi-functionality, serving both as structural support elements and as energy dissipation mechanisms. The compression members provide both lateral support and energy dissipation through rotation, while the tension members provide both restoring force and energy dissipation through extension. This universal design allows the same components to fulfill multiple functions, avoiding the need for additional specialized energy dissipation devices and thereby reducing system 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 solution allows the building frame to return to its original centered position without yielding the restoring force elements, effectively managing seismic loads and energy dissipation, thereby enhancing the structural integrity and resilience of the building.
Implementation Method 1
The elastic restoring force elements must remain elastic throughout any design elongation or stretch so that they can return to their original geometry and bring the building back to its original position
Implementation Method 2
some form of additional energy dissipation is usually (although not always) also included into proposed designs for a self-centering earthquake resistant structure, quite often in the form of a metallic yielding device of some kind
Data Source
AI summary
An elongated tension-only or centering brace for a structural frame is provided where the brace is anchored at a first attachment point and to a second attachment point that is removed from the first attachment point. The elongated tension-only brace has one or more elastic restoring force elements that have effective lengths greater than the length of the tension only brace between the attachment points.