Structural Fuse Seismic Retrofitting for Confined Spaces
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Solution Overview
Problem
Seismic retrofitting of 'soft, weak, or open front' buildings in urban areas like San Francisco is challenging due to limited space and obstructions, making it difficult to install cantilevered columns or moment-resisting frames, which increases construction costs and may deter owners from retrofitting their buildings voluntarily.
Innovation Solution
A seismic retrofitting system featuring a column with a structural fuse that yields in response to horizontal loads, providing a seismic response factor of at least 6.5, and includes a retention plate to prevent buckling, allowing for predictable bending and increased ductility, thus enabling effective seismic resistance in confined spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cantilevered columns or moment-resisting frames are installed for seismic retrofitting, then seismic resistance is improved, but construction cost increases and installation difficulty increases due to limited space and obstructions
Solution Approach 1:
The structural fuse is divided into multiple segments (first structural fuse and second structural fuse) that can be independently installed on either side of the column. This segmentation allows the system to be installed in confined spaces where utilities and obstructions are present, as each segment can be positioned independently without requiring large clearances for traditional moment-resisting frames.
Solution Approach 2:
The invention extracts the energy-dissipating function from the main column and places it in separate structural fuses. The column remains primarily in the elastic range while the fuses yield inelastically, separating the protective function (seismic energy dissipation) from the load-bearing function (column integrity). This allows installation in tight spaces where the column itself cannot be modified extensively.
2Reliability
If traditional seismic retrofitting methods are used, then seismic resistance is improved, but construction cost increases due to extensive structural modifications
Solution Approach 1:
The structural fuses are designed as sacrificial elements that yield inelastically during seismic events and can be replaced after damage. This approach is more economical than strengthening the entire column or building structure, as the fuses are relatively simple, replaceable components that provide seismic protection without requiring extensive permanent modifications to the building.
Solution Approach 2:
The invention applies seismic protection locally at specific points where structural fuses are attached to the column, rather than requiring global strengthening of the entire structure. The fuses are positioned at locations that optimize their ability to dissipate seismic energy while minimizing interference with existing building utilities and obstructions, thereby reducing overall construction costs.
3Adaptability or versatility
If the column is designed to yield inelastically, then ductility is improved, but the column's load-bearing capacity is reduced and structural integrity is compromised
Solution Approach 1:
The inelastic deformation capacity is extracted from the column and transferred to the structural fuses. The column is designed to remain primarily in the elastic range, maintaining its full load-bearing capacity and structural integrity. The fuses are specifically designed to yield inelastically, providing the necessary ductility and energy dissipation without compromising the column's strength.
Solution Approach 2:
The structural fuses act as intermediary elements between the seismic loads and the column. They mediate the energy transfer by yielding inelastically and dissipating seismic energy through controlled deformation, thereby protecting the column from inelastic damage while still allowing the structure to respond ductilely to seismic events.
4Loss of energy
If structural fuses are installed to yield simultaneously, then energy dissipation is improved, but the complexity of ensuring simultaneous yielding increases
Solution Approach 1:
The structural fuses are positioned asymmetrically on either side of the column at different heights (first structural fuse at a first height, second structural fuse at a second height). This asymmetric arrangement, combined with specific geometric properties of the fuses, enables them to yield simultaneously under bidirectional seismic loading without requiring complex control mechanisms. The asymmetry in positioning compensates for the different loading paths and ensures balanced energy dissipation.
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 system effectively enhances the seismic resistance of buildings by allowing the structural fuse to yield simultaneously, reducing the need for extensive structural modifications and maintaining the column in the elastic range, thereby reducing construction costs and increasing the building's ability to withstand seismic forces.
Implementation Method 1
The structural fuse is configured to yield in response to a load in a horizontal direction perpendicular to the vertical direction and applied at the first attachment point that is insufficient to cause yielding of the column
Implementation Method 2
The structural fuse includes a retention plate to prevent buckling
Data Source
AI summary
A retrofitting structure includes a column fixed in the ground. A structural fuse is pivotally mounted to the retrofitting structure at two vertically offset locations. The structural fuse is further pivotally mounted at a third location above the column to a superstructure of a building. The structural fuse is designed to yield for loads for which the column only deforms elastically. The structural fuse may be a planar member captured between the column and a retention plate to prevent buckling of the structural fuse. The retention plate may include a channel beam in order to provide sufficient stiffness to prevent buckling. Desired yield properties are obtained by increasing width of the structural fuse with distance from the bottom of the column. The width is augmented with distance from the bottom of the column to account for friction with the column and retention plate.