23 research outputs found
Fail-safe optimization of viscous dampers for seismic retrofitting
This paper presents a new optimization approach for designing minimum-cost
fail-safe distributions of fluid viscous dampers for seismic retrofitting.
Failure is modeled as either complete damage of the dampers or partial
degradation of the dampers' properties. In general, this leads to optimization
problems with large number of constraints. Thus, the use of a working-set
optimization algorithm is proposed. The main idea is to solve a sequence of
relaxed optimization sub-problems with a small sub-set of all constraints. The
algorithm terminates once a solution of a sub-problem is found that satisfies
all the constraints of the problem. The retrofitting cost is minimized with
constraints on the inter-story drifts at the peripheries of frame structures.
The structures considered are subjected to a realistic ensemble of ground
motions, and their response is evaluated with time-history analyses. The
transient optimization problem is efficiently solved with a gradient-based
sequential linear programming algorithm. The gradients of the response
functions are calculated with a consistent adjoint sensitivity analysis
procedure. Promising results attained for 3-D irregular frames are presented
and discussed. The numerical results highlight the fact that the optimized
layout and size of the dampers can change significantly even for moderate
levels of damage
Evaluation of deflection amplification factor for steel buckling restrained braced frames
Localized Damage Detection Algorithm and Implementation on a Large-Scale Steel Beam-to-Column Moment Connection
Estimating Fundamental Dynamic Properties of Structures with Supplemental Dampers by Means of Generalized Single Degree of Freedom Systems
Evaluation of Seismic Response Factors for Eccentrically Braced Frames Using FEMA P695 Methodology
This paper reports details of a numerical study undertaken to evaluate seismic response factors for steel eccentrically braced frames (EBFs) using the FEMA P695 methodology. Six archetypes were designed by making use of the current U.S. specifications, and their behavior was assessed by making use of nonsimulated collapse models. Results indicate that the current values of response factors result in designs with higher collapse probabilities than expected. Two modifications were developed to bring the collapse probability of these archetypes to acceptable levels. The first modification is on the deflection amplification factor while the second one is on the response modification coefficient. Six archetypes were redesigned using the proposed modifications and reevaluated using the FEMA P695 methodology. The results indicate that the proposed modifications are adequate to satisfy the target collapse probability. Maximum and cumulative link rotation angles were observed to be less than the predefined limits