Pollino 2012
This paper uses the latest publications on controlled rocking steel braced frames to describe and illustrate the transfer of forces through the systems. The demands placed on the non-structural components within each building floor were investigated using a computational model by calculating critical response quantities. Such quantities included inter-story drift, peak floor accelerations and floor spectra. Results were compared with conventional fixed-base ductile brace frame structures.
System Concept
The controlled rocking brace frame seismic lateral force resisting system consisted of an elastic braced frame within the building. This enabled uplift from the supports prior the yielding and buckling of braces. Along with the tributary vertical weight, the system can be PT for self-centering. The system implemented displacement-based steel yielding devices and velocity dependent viscous dampers are the uplifting location to control the response.
Experimental Study, Results, and Discussion
Using the ANSYS program, the seismic response of the building was calculated by preforming a nonlinear transient seismic analysis. A set of 10 ground motions from Los Angeles DBE were used in the analysis. Frame drift was slightly less than the ASCE 7-10 simplified analysis procedure target drift of 1.5%. A significant floor spectral acceleration was observed at the 2nd mode frequency. Addition cases were run with an increase in element cross-sectional area, which showed significant decreases in floor spectra.
It was concluded that controlled rocking braced frame seismic later force resisting systems can potentially provide increased seismic performance for structural and non-structural components compared to ductile systems and can increase the resiliency and sustainability of a structure subjected to seismic events.
Reference
Pollino, M. (2012). “Structural and Non-structural Seismic Demands on Controlled Rocking Steel Braced Frame Buildings,” Proceedings of the Structures Congress 2012, Chicago, IL, March 29-31.