Structural Analysis of Single Diagonal Damped Brace
The damped brace is modeled as a link element in most software. In other words, it is modeled as a fictitious yielding brace. Because the friction damper can be treated as an ideal elastoplastic element, this allows the application of Wen's model. While a simplification of the damper's behavior, the Wen model simplifies the analysis.
A yielding brace would yield and begin to deform allowing the building to absorb and dissipate the earthquake's energy. However, the brace would need to be replaced after the earthquake.
In contrast, the friction damper slips instead of yielding and by means of the elasticity of the primary structural elements, returns to its original position.
The damper's hysteretic curve allows the damper to be modeled as a link in static, dynamic and non-linear analysis. The only information needed is the properties of the link which in this case is a fictitious yielding brace with its own linear and non-linear properties. This can be modeled in popular software such as ETABS or SAP2000 using the following parameters.
Click Here for ETABS Parameters Example
*Slip Load should be equal to 75% of the actual brace's yield strength and 130% of the service loads (e.g. wind shear). The mass of the damper will vary depending on the slip load and travel required
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Some software allows for the direct input of the hysteretic loop. In the case that the engineer would like to perform the analysis using these features, the quasi-rectangular hysteretic loop can be used
Since the damper stiffness is equal to the brace stiffness up until it slips, the effective and brace stiffness are equal.
The damper slips at approximately constant load and therefore the post-yield stiffness ratio can be estimated at near zero, 0.0001.
Can be installed in
- Steel Frames
- Reinforced Concrete frames
- Concrete or Steel Shear wall
- Timber frames
Can be used in any lateral force resisting system as a damping system or as a reusable safety "fuse" to protect structures from inelastic deformation or failure.
While there are many possible methods of installing the friction damper the single diagonal tension compression configuration is commonly used
Friction Dampers can be customized to fit almost any building and the link below has commonly used slip loads and strokes.
Friction Damper Catalog
The Catalog will provide you with some examples of standard dampers, their dimensions, and masses.
When you complete your analysis provide us with the required slip load and stroke and Quaketek will custom design the damper you require.