טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLavan Oren
SubjectSeismic Behavior and Control of Irregular Structures:
Energy Approach
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Robert Levy


Abstract

This research addresses the optimization problem of minimizing the added damping of prelocated viscous dampers subject to constraints on local performance indices (such as envelope of maximal drifts, envelope of hysteretic energy etc.) in addition to the dynamic equations of motion for structures excited by ensembles of realistic ground motion records.

The solution of the optimization problem is attained by first deriving the expressions for the gradients in an innovative manner using optimal control theory of the constraints and then utilizing an appropriate first order optimization scheme. This gradient based optimization scheme is coded and used for the design of added damping in linear 2D and 3D structures, as well as in nonlinear plane frames.

The optimal designs attained by the gradient based optimization approach show an important characteristic of the optimal solution: dampers are assigned only where the local performance index has reached its allowable value. Based on this observation, a procedure analogues to the Fully Stressed Design, used for the design of trusses under static loadings, is developed and applied to the same examples with practically identical results . This simple, analysis oriented, approach is very attractive for practical use in design offices.

It is shown in the examples that constraining the local performance indices of the peripheral frames, in the 3D case, make the methodology applicable to irregular 3D structures. Moreover, constraining the local performance indices, and considering a plastic behavior of the damped structure, make the methodology applicable to structures with strength irregularity as well.