Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
RELIABILITY-BASED STRUCTURAL OPTIMIZATION USINTG RESPONSE
SURFACE APPROXIMATIONS AND PROBABLISTIC SUFFICIENCY FACTOR
By
Xueyong Qu
August 2004
Chair: Raphael T. Haftka
Major Department: Mechanical and Aerospace Engineering
Uncertainties exist practically everywhere from structural design to manufacturing,
product life-time service, and maintenance. Uncertainties can be introduced by errors in
modeling and simulation; by manufacturing imperfections (such as variability in material
properties and structural geometric dimensions); and by variability in loading. Structural
design by safety factors using nominal values without considering uncertainties may lead
to designs that are either unsafe, or too conservative and thus not efficient.
The focus of this dissertation is reliability-based design optimization (RBDO) of
composite structures. Uncertainties are modeled by the probabilistic distributions of
random variables. Structural reliability is evaluated in term of the probability of failure.
RBDO minimizes cost such as structural weight subj ect to reliability constraints.
Since engineering structures usually have multiple failure modes, Monte Carlo
simulation (MCS) was used to calculate the system probability of failure. Response
surface (RS) approximation techniques were used to solve the difficulties associated with