Papers by Author: Sang Ho Lee

Abstract: The fatigue vulnerability estimation method including the effects induced by the corrosion rate and the traffic variation with time has been proposed to evaluate the reduction of fatigue strength in steel bridge members. A fatigue limit state function considering corrosion and traffic variation is established to determine whether the steel bridge members have been damaged by both corrosion and fatigue or not. Monte-Carlo simulation is used for reliability analysis which provides the data used to obtain fatigue vulnerability curves. The results show that the damage accumulation induced by fatigue in steel bridges could be assessed by fatigue vulnerability curve considering influences of corrosion and traffic variation.

Abstract: New laminate design for improved toughness in hexacelsian-alumina composite is introduced. The composite is based on crack deflection in a weak interphase in the alumina matrix and hexacelsian interphase. The strength and toughness of the laminated composite were studied both qualitatively by electronic microscopy and measuring flexure strength. The metastable hexacelsian interphases had partially microcracks to provide crack deflection in the composite, and the crack deflection noticeably proceeded along the meta-stable hexacelsian interphase. Load-deflection curve for the laminate showed improved work of fracture of 2.23 kJ/m2.

Abstract: An efficient and accurate numerical program with enhanced point collocation meshfree method is developed to simulate crack propagation under dynamic loading conditions. The enhanced meshfree method with point collocation formulation and derivative approximation in solids is presented. This study also presents the crack propagation criterion and computation of propagating direction, and the total structure of the numerical program named PCMDYC(Point Collocation Meshfree method for DYnamic Crack propagation). Several examples of crack propagation under dynamic loads are analyzed to simulate the arbitrary crack propagation under dynamic loads. The results show that PCMDYC predicts the propagating path of crack under dynamic loading conditions accurately and robustly.