Vol. 5, No. 3, pp. 303-324 (2009)
PLASTIC DESIGN AND SEISMIC RESPONSE OF KNEE BRACED FRAMES
Maria Antonietta Conti 1, Luigi Mastrandrea 2 and Vincenzo Piluso 3,*
1 Department of Civil Engineering, University of Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy
2 Department of Civil Engineering, University of Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy
3 Full Professor, Department of Civil Engineering, University of Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy
*(Corresponding author: E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.)
Received: 15 July 2008; Accepted: 20 July 2008
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ABSTRACT
In this paper a design methodology aiming at the development of a collapse mechanism of global type for seismic resistant knee braced frames is presented. The proposed methodology is based on the assumption that the beam, brace and knee sections are known, while the column sections constitute the unknowns of the design problem. The design requirements are derived by means of the kinematic theorem of plastic collapse. In particular, column sections are obtained by imposing that the mechanism equilibrium curve corresponding to the global mechanism has to lie below those corresponding to all the undesired mechanisms within a displacement range compatible with the local ductility supply of knee elements. The proposed design procedure has been implemented in a computer program and applied to design some knee braced frames. Successively, static and dynamic non-linear analyses have been carried out aiming at the evaluation of the performance of the designed braced frames in terms of collapse mechanism developed under seismic forces, energy dissipation capacity and global and local ductility demands.
KEYWORDS:
Knee braced frames; collapse mechanism; capacity design; limit design; non-linear analyses; equivalent moment; global ductility; local ductility
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