Seismic Brace Yielding Links With Displacement Restraint Load Transfer
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Solution Overview
Problem
Fracture of steel yielding elements in lateral force-resisting systems during seismic events leads to structural instability and collapse due to localized strain increases, which occur well below the material's expected tensile fracture elongation.
Innovation Solution
Incorporation of displacement control elements within seismic braces that move within a displacement zone, contacting a restraint to transfer loads to different portions of the yielding element, thereby limiting overall and localized elongation and distributing deformation evenly along the element's length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If steel yielding elements are designed to yield axially in tension and compression, then energy absorption capacity is improved, but localized strain increases lead to premature fracture
Solution Approach 1:
The yielding element is divided into multiple segments by introducing displacement control elements at intermediate positions along its length. These elements create distinct deformation zones that segment the overall yielding process, preventing localized strain concentration in a single region and thereby reducing premature fracture risk while maintaining energy absorption capacity
Solution Approach 2:
The displacement control elements are designed to move dynamically within displacement zones during yielding, contacting restraints at specific displacement thresholds. This dynamic behavior allows the system to adaptively control deformation distribution, transferring load to different portions of the yielding element as deformation progresses and preventing static localized strain accumulation
2Reliability
If displacement control elements are added to distribute deformation, then fracture resistance is improved, but device complexity increases
Solution Approach 1:
The displacement control elements are nested within the yielding element structure, with each element positioned inside a displacement zone formed by the yielding element's geometry. This nested configuration allows the control mechanism to be integrated into the existing structure rather than adding external components, minimizing overall complexity while achieving deformation distribution
Solution Approach 2:
The displacement control elements utilize the yielding element's own deformation to activate the load transfer mechanism. As the yielding element deforms, the displacement control elements automatically move and contact restraints, transferring load to different portions without requiring external control systems or additional actuation mechanisms
Data Source
AI summary
A yielding seismic element includes one or more displacement control elements connected to a yielding element. The yielding element is designed to deform under seismic forces. When the yielding element experiences an instance of local deformation, the displacement control elements interact with a displacement restraint fixed relative to the yielding element. The displacement restraint prevents further deformation at the instance of local deformation.