دانلود رایگان مقاله انگلیسی بهینه سازی طراحی عملکرد مبتنی بر قابلیت اطمینان برای مقاوم سازی لرزه ای سازه های بتنی - Sage 2017

Abstract

Fiber-reinforced polymer composites can be externally bonded to reinforced concrete members which provide an effective seismic retrofit strategy for reinforced concrete structures. For seismic retrofit of a complex building structure, due to the large number of structural members, an optimum design which ensures the use of the minimum amount of fiber-reinforced polymer to achieve a given level of seismic performance is highly desirable for economic reasons. In addition, such an optimum design approach is best built on a probabilistic basis so that various sources of uncertainties in the design process can be appropriately accounted for. This work therefore studies an efficient reliability-based optimization approach for the seismic retrofit design of reinforced concrete structures using fiber-reinforced polymer composites. The structural performance is assessed at the system level using nonlinear pushover analyses. In the proposed approach, the inelastic interstory drift ratios are modeled as indeterministic variables to consider the uncertainties of earthquake loading. By contrast, the thickness of the fiber-reinforced polymer jacket is considered as a deterministic design variable. The reliability-based design approach is formulated by minimizing fiber-reinforced polymer cost subject to prescribed structural reliability constraints. Using the results of nonlinear static pushover analyses and reliability analyses, the reliability index constraints are explicitly formulated with respect to the deterministic design variables based on the virtual work principle as well as Taylor series expansion. A numerical optimality criteria method is derived and programmed to solve this reliability-based nonlinear retrofit design optimization problem. A design example is included to illustrate the application of the new optimization approach.

Conclusion

The reliability-based optimization problem for FRPretrofitted buildings has been formulated such that not only it can minimize the FRP cost but also satisfy the required reliability constraints due to the uncertainties of seismic loadings. The proposed reliability-based optimization technique integrates inelastic structural analysis using the pushover analysis method, reliability analysis using the FOSM method, and an optimization technique using the OC method. Although these are three independent procedures, reliability-based optimization requires repeated applications of these three procedures until the solution convergence is achieved. The proposed algorithm converges smoothly and steadily, and is weakly dependent on the initial sizes selected to commence the design iterations; it is able to optimize a reliability-based FRP-retrofitted RC buildings and to distribute its lateral stiffness to satisfy interstory drift reliability index constraints with a minimum FRP cost. In addition, the reliability-based design is able to ensure optimal reliability designs of building structures through the consideration of design constraints that fulfill a target value of the required reliability index for each story, which cannot be achieved in a deterministic optimal design. The proposed design optimization method provides a foundation for future development; other types of uncertainties such as structural modeling uncertainties can be further considered and incorporated.