Tremblay, Lacerte, and Christopoulos 2008
In an analytical study, the authors compare the response of 2, 4, 8, 12, and 16-story buildings to seismic excitation with BRBs and SCED bracing members. Incremental static analyses and nonlinear dynamic analyses were performed. The same floor plan was used in each model. Several studies have shown that structures with BRBs can often experience residual lateral deformation or the concentration of damage at some stories. Having another resisting element is key to prevent these from occurring. The purpose of the study was to validate the use of SCEDs as effective energy dissipaters to supplement the use of BRBs on structures.
System Concept
A friction energy-dissipating element connects the braces in this SCED system. Pretension fiber tendons are also included to act as a self-centering mechanism. When the brace is forced into tension or compression, the tendons are elongated. The tendons exhibit a flag-shaped hysteretic response and thus full re-centering is possible.
Analytical Study, Results and Discussion
2, 4, 8, 12, and 16-story buildings were evaluated with both BRBs and SCEDs. A 2D model was used with a rigid diaphragm between the braces and columns. The SCED to brace connection was modeled as two springs in series. The models were excited with ground motion at 50, 10, and 2% of the fifty year hazard level in Los Angeles.
It was shown that the peak story drifts was reduced using the SCED, resulting in better resistance to collapse. The activation and response of the SCED as an energy-dissipating mechanism is more sudden, however, thus floor acceleration pulsing occurs that could damage stiff structural and nonstructural components of the building. Of note is that the results are more pronounced with an increase of stories. On lower stories, both systems experience greater deformations than is predicted by design code, thus it is recommended by the authors that the response modification factor be reduced to 5 for low level structures.
Reference
Tremblay, R., Lacerte M., and Christopoulos, C. (2008). "Seismic Response of Multistory Buildings with Self-Centering Energy Dissipative Steel Braces." Journal of Structural Engineering 134.1, pp. 108-120.