Buckling-Restrained Brace Discrete Spring Gap Control
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Solution Overview
Problem
Current buckling restrained braces (BRBs) face challenges in controlling the gap between the core plate and the concrete casing, leading to inefficient energy absorption and increased structural costs due to friction and premature failure from buckling waves, which affects their performance in withstanding seismic and lateral forces.
Innovation Solution
The use of a discrete spring layer made of materials like corrugated paper or corrugated metal, which creates a controlled space between the core plate and the concrete, allowing for lateral expansion and reducing friction, thereby enhancing the BRB's ability to absorb forces without compromising the grout or casing tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the concrete is placed in intimate contact with the core plate, then the structural integrity is improved, but the core plate cannot expand laterally under compression, causing it to press against the concrete and transfer load to the casing, leading to buckling
Solution Approach 1:
A gap material is introduced as an intermediary between the core plate and the concrete casing. This gap material allows the core plate to expand laterally under compression without transferring load to the concrete and casing, while still maintaining structural integrity. The gap material acts as a mediator that enables the core plate's natural expansion behavior while preventing harmful contact with the concrete.
2Reliability
If a gap is created between the core plate and concrete, then the core plate can expand freely under compression, but the gap control becomes difficult, leading to premature failure from buckling waves and increased friction
Solution Approach 1:
The gap is defined by a flexible formwork system consisting of thin films or shells that can accommodate the core plate's lateral expansion. This flexible formwork maintains a consistent gap spacing while allowing the core plate to expand freely during compression. The flexible nature of the formwork prevents the development of buckling waves and reduces friction compared to rigid gap control methods.
3Use of energy by moving object
If the core plate is allowed to buckle freely, then the energy absorption capacity is improved, but the buckling waves cause premature failure and increase structural costs
Solution Approach 1:
The gap material provides preliminary protection against harmful buckling waves by allowing controlled lateral expansion before significant buckling can occur. This preliminary anti-action prevents the development of large-amplitude buckling waves that would cause premature failure, while still enabling sufficient energy absorption through controlled deformation. The gap material effectively counteracts the tendency toward harmful buckling before it can develop.
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 enables the BRB to sustain multiple seismic events with reduced deformation in the structure, minimizing damage and maintenance costs by optimizing the gap between the core plate and concrete, thus improving the structural system's resilience and durability.
Implementation Method 1
As the core plate expands it would press against the concrete, thus engaging the concrete and subsequently the pipe casing. This is the same reaction as a typical foam ear plug. If it is compressed from the two ends it gets fatter (thicker and shorter). The material has to move somewhere.
Implementation Method 2
The layer of discrete springs provide a space so that when pressure is applied to the ends of the first end and the second end of the core plate, the material of the core plate may be compressed and expand laterally without contacting the grout matrix. In this way, the core plate is allowed to absorb the force of lateral loads without compromising the grout layer or the casing tube.
Data Source
AI summary
Disclosed is a buckling restrained brace which is a core plate inside a tube, with the plate prevented from buckling by being surrounded by the tube. The core plate is provided with a layer of discrete springs adjacent the core plate, with the interior of the tube otherwise filled with cement. The layer of discrete springs may be cardboard of other material. The layer of discrete springs defines a space between the core plate and the concrete, to allow for expansion of the core plate under compression from the ends.