טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAvishur Meiri
SubjectSeismic Behavior of Passively Controlled Structures under
Uncertaintes
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Oren Lavan
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Over the past two decades, there has been a significant shift in the approach to seismic design.  Many new technologies associated with passive energy dissipation and control have been introduced and have reached a considerable level of maturity (e.g. Soong and Dargush, 1997; Christopoulos and Filiatrault, 2006). Furthermore, the overall concept of performance-based design has gained prominence. While all of this represents a major step forward, as a consequence, the design process itself has become increasingly complex. Consequently, the design and optimal design of seismic retrofitting has been studied extensively in the last couple of decades and new methodologies of passive control optimal design have been proposed. In some cases it has even matured to the level of supplying simple design tools for practicing engineers (Levy and Lavan, 2006; Lopez-Garcia, 2001). Those methodologies matured to consider uncertainty in the earthquake hazard, to some extent, by adopting either an ensemble of records that was chosen or scaled using statistical tools or a stochastic process. However, the effect of uncertainty in the structural properties on the performance of retrofitted structures has not been considered. That is, the design procedures given in the literature make use of the nominal values for the properties of the structure to be retrofitted. It should be noted that, in the case of retrofitting, this uncertainty is expected to be more pronounced and is strongly dependent on the documentation available.

This research examines the sensitivity of optimal designs of seismic retrofitting by means viscous dampers attained using the nominal properties of the structure to uncertainty in structural properties. Viscous dampers are first optimally designed for the nominal properties of the retrofitted structures and given ensembles of records. The behavior of the retrofitted structures considering uncertainty in their properties is then tested using Monte Carlo simulation. Five frames are examined in this research: two yielding shear frames and three yielding flexural frames. The two shear frames model the behavior of frames where columns are likely to yield before beams while the flexural frames model the behavior of frames where beams are likely to yield before columns.

It is shown that the uncertainty leads to larger mean drifts than expected and that some designs are more sensitive than others. The physical reason for that is discussed and some rules as to what designs are expected to be more sensitive are given.