Abstract
This paper proposes an optimal plan for seismically retrofitting reinforced concrete (RC) frame structures. In this method, the columns are wrapped by fiber-reinforced polymer (FRP) layers along their plastic hinges. This technique enhances their ductility and increases the resiliency of the structure. Two meta-heuristic algorithms (i.e., genetic algorithm and particle swarm optimization) are adopted for this purpose. The number of FRP layers is assumed to be the design variable. The objective of the optimization procedure was to provide a uniform usage of plastic hinge rotation capacity for all the columns, while minimizing the consumption of the FRP materials. Toward this aim, a single objective function containing penalty terms is introduced. The seismic performance of the case study RC frame was assessed by means of nonlinear pushover analyses, and the capacity of the plastic hinge rotation for FRP-confined columns was evaluated at the life safety performance level. The proposed framework was then applied to a non-ductile low-rise RC frame structure. The optimal retrofit scheme for the frame was determined, and the capacity curve, inter-story drift ratios, and fragility functions were computed and compared with alternative retrofit schemes. The proposed algorithm offers a unique technique for the design of more resilient structures.
Highlights
Fiber-reinforced polymer (FRP) is a type of composite material made of a polymer matrix reinforced with fibers [1]
The genetic algorithm (GA) reached the optimal solution after 832 iterations, in comparison to particle swarm optimization (PSO), which converged after 1000 iterations
The GA algorithm included some fluctuations even at higher iterations. This is because the PSO algorithm uses a highly efficient exploration method, as it was capable of converging to the optimum answer without deviating in higher iterations
Summary
Fiber-reinforced polymer (FRP) is a type of composite material made of a polymer matrix reinforced with fibers [1]. Retrofitting reinforced concrete (RC) structural elements with FRP composites has been widely studied with the aim of enhancing the structural performance under various load combinations. The majority of studies on retrofitting by FRP have been conducted on isolated components/elements (e.g., columns, beams, and joints) [6,7,8,9], rather than considering them as a part of a frame structure. In practice, it is the response of the frame as a whole that is of greatest concern for engineers. Thereby, the behavior assessment of the whole frame before and after retrofitting with FRP is a demanding field of research
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