Optimization‐based minimum‐cost seismic retrofitting of hysteretic frames with nonlinear fluid viscous dampers

Abstract

Summary In this paper, we discuss an optimization‐based approach for minimum‐cost seismic retrofitting of hysteretic frames with nonlinear fluid viscous dampers. The proposed approach accounts also for moment‐axial interaction in the structural elements, to consider a more realistic coupling between added dampers and retrofitted structure. The design variables of the problem are the damping coefficients of the dampers. Indirectly, the design involves also the stiffness coefficients of the supporting braces. In the optimization analysis, we minimize a realistic retrofitting cost function with constraints on inter‐story drifts under a suite of ground motion records. The cost function includes costs related to the topological and mechanical properties of the dampers' designs. The structure is modeled with a mixed finite element approach, where the hysteretic behavior is defined at the beams' and columns' cross sections level. We consider damper‐brace elements with a visco‐elastic behavior characterized by the Maxwell model. The dampers' viscous behavior is defined by a fractional power law. Promising results obtained for a two‐story, a nine‐story, and a 20‐story 2‐D frames are presented and discussed.

Fail‐safe optimization of viscous dampers for seismic retrofitting

“…Recently, an attempt was made to develop methodologies that combine the good aspects of the two set of approaches mentioned above: practical (i.e., near discrete) distributions of dampers with a reasonable computational cost. [37][38][39][40] This is achieved using a gradient-based continuous optimization approach for the placement and sizing of linear viscous dampers coupled with material interpolation techniques, typically applied in topology optimization. 41 In recent work, material interpolation functions have been used also for the optimization-based seismic design of steel moment-resisting frames.…”

Optimization‐based seismic design of steel moment‐resisting frames with nonlinear viscous dampers

“…67 Moreover, the DMO functions are successfully utilized for a similar application in several works. 9,[15][16][17][18] Both the cross-sections and the damping coefficients are reformulated in a similar fashion by the DMO functions, and the formulation are as follows:…”

“…50,51 In these cases, using a linear frame model may lead to an underestimated estimate of the structural response and, in turn, lead to an optimized design that violates the constraints. 18 The objective of the optimization is to minimize the total cost of the MRF, FVDs, and supporting braces. Several code requirements and rational engineering rules are set as constraints, in addition to a performance constraint.…”

“…The effectiveness of the DMO functions to attain a practical design that relies on a few types of FVDs for the optimal retrofitting problem has been proved. [15][16][17][18] Recently, the DMO functions are also successfully utilized for the optimal design of MRFs without any supplemental dampers, 9 in which the crosssection properties were optimized out of standard steel tables. In this paper, the DMO functions are utilized to achieve a desired practical oriented design for both the cross-sections and the FVDs.…”

Full‐scale hybrid test for realistic verification of a seismic upgrading technique of RC frames by BRBs

“…3,4 The upgrading technique consists in inserting BRBs within the RC frame, thus providing additional stiffness and energy dissipation to control drift demand. This technique can be a good alternative or complement to other techniques [5][6][7][8][9][10][11][12] devoted to the improvement of seismic performance of existing RC framed structures: for instance, adding RC walls, enlarging cross sections of beams and columns, inserting steel braces, adding energy dissipaters, and realising base isolation. The field of application of the investigated technique is remarkable.…”