Valente et al. 2011
This paper presented a new alternative dissipative bracing system for earthquake-resistant steel buildings, named braced ductile shear panel (BDSP) system. In past, moment resisting and concentrically braced frames were using for earthquake resistant steel buildings. However, moment resisting frames had limited stiffness and concentrically braced frames had limited ductility. This paper included the results of numerical investigations in order to show insufficiencies of moment resisting and concentrically braced frames. In the first phase of the study analytical models and finite element models merged together. Dimensions, geometry and other parameters were defined in order to make the behavior of the BDSP system as close as possible to the initial concept. In the second phase, the favorable effects of the well-designed BDSP system on steel were evaluated.
System Concept
The system was composed of four concentric X braces. These I-shaped braces were placed in series with a yielding rectangular ductile shear panel, and transfer the lateral displacements arising from the lateral load on the frame to the shear panel. The ductile shear panel was composed of non-slender in-plane plate elements and boundary flanges. The limiting seismic strength demand on the bracing system was defined by the strength of the ductile shear panel in the series configuration.
Energy dissipation was concentrated only in the shear panel, since only it was designed for plastic strains. Moreover, it could be replaceable by means of bolted connections. Therefore, this system can be used both in new buildings and also as a retrofit.
Analysis, Results, and Discussion
ABAQUS was used in the formation of detailed finite element model in order to predict the behavior of the bracing system taking into account geometric and material nonlinearities. In the numerical models, shell elements were used to represent the braces, the ductile shear panel and the connection elements. Different yield stresses were used for the shear panel and other parts of bracing system. Then, force displacement curves were obtained from fully reversed displacement cycles applied to the top nodes. So, the response of the bracing system under cyclic lateral loading was obtained. From all finite element analysis, it was concluded that plastic strains were localized completely inside the BDSP web.
In the second part of analysis, the force-displacement relationship obtained from the first phase was used to define the properties of nonlinear links used in order to model the bracing system for global analyses.
From the results of the numerical investigations, the proposed bracing system can protect the structural elements of the frame by preventing them from damage under severe seismic action, and energy dissipation mostly concentrated in the device.
Reference
Valente, M., Giannuzzi, D., Ballarini, R., and Hucklebridge, A. (2011). “A New Dissipative Bracing System for Steel Structures,” Proceedings of the Eurosteel 2011, August 31-September 2, Budapest, Hungary.