Young Soo Jeong

Evaluation of Structural Responses on Artificial Fatigue Crack for Bulb Rib Orthotropic Deck

An orthotropic steel deck is quite susceptible to fatigue cracking at its welded joints depending on the structural stiffness, occurrence of high-magnitude cyclic load stress, and complicated geometric details of the welded joints. This study experimentally and numerically investigated the structural behavior of an orthotropic steel deck with bulb ribs. The behavior of the deck was examined, particularly the warped deformations of the developed fatigue cracks and the uniform stress distributions against moving loads attributed to the decks asymmetric bulb ribs. An artificial fatigue crack serving as an authentic model of a fatigue crack was developed in the longitudinal bulb rib of an orthotropic steel deck in actual service. The loading tests were conducted on an orthotropic steel deck with artificial fatigue cracks. The test results were evaluated based on the artificial fatigue crack length on the longitudinal bulb ribs and compared with a nonlinear full finite-element analysis model considering the nonlinear contact behavior of artificial fatigue cracks.

Influence of size and proximity of paint coating defects on corrosion behavior of carbon steel plates

To ensure the safety of painted steel structures, it is important to evaluate the influence of the size and proximity of coating defects on corrosion behavior. In this research, accelerated exposure tests were carried out using combined corrosion cycles, which consisted of exposure to atomizing salt water, wetting, and drying with hot and warm wind. The test specimens were paint-coated steel plates with individual circular machined coating defects 1, 3, 10, and 15 mm in diameter. Multi-circular defects 1 mm in diameter were also created in the specimens. The test results indicate that the mean and maximum corrosion depths increased with increasing diameter of the single defect of the coated steel plate. When actual coated steel members are exposed to corrosive chloride environments such as those represented by the corrosion cycle testing conducted in this research, the corrosion depth for multi-circular defects 1 mm in diameter appears to be 1.5 to 2.5 times greater than that for a single-circular defect.

Practical method for estimating time-dependent corrosion depth of uncoated carbon steel plates under various atmospheric environmental conditions using fe/ag galvanic couple corrosion sensor

In this research, an evaluation method for the time-dependent corrosion depth of uncoated structural steel plates using an Fe/Ag galvanic couple atmospheric corrosion monitoring (ACM)-type sensor was proposed. This method was focused on environments with and without effects of rainfall and airborne sea salt. Atmospheric exposure tests were carried out on the uncoated carbon steel plates in four sites in which the environments varied widely as a function of rainfall and airborne sea salt. In addition to this, the corrosive environments of the skyward-and groundward-facing surfaces of the plates were monitored using the ACM sensors.

Assessment of the Corrosion Characteristics of the Carbon Steel under Different Atmospheric Environments

Various maintenance problem has been reported according to the increase in service period of steel structures. It is difficult to examine and evaluate the corrosion problem and phenomena because of its uncertainty based on the environmental condition. Thus, the corrosion characteristics of the carbon steel were investigated to analyze the corrosion effect of carbon steel on the different atmospheric environments. The atmospheric exposure tests on uncoated carbon steel plates were conducted, to examine the corrosion phenomena and to obtain a fundamental corroded surface under different corrosion atmospheric environments. The corrosion characteristics of the carbon steel were compared depending on their different atmospheric environment and their exposure periods.

Assessment of shear behaviors of a web panel with free lower boundary

Shear behaviors of a web panel are changed by web boundary conditions and web panel with free web boundary has been reported by severe corrosion damage. In this study, post shear buckling behaviors of web panel with free-lower web boundary was examined to evaluate its shear failures and strengths depending on its web boundary changed by corrosion. Thus, nonlinear finite element analyses were carried out to identify their post buckling behaviors. Their shear behaviors and shear failure mode were compared as well as comparisons of their behaviors depending on aspect ratio and boundary conditions.

Spatial Statistical Analyses for Time-Dependent Corroded Surfaces of Uncoated Weathering Steel Plates in Various Corrosive Environments

To ensure the safety of steel structures, it is important to evaluate the time-dependent corrosion behavior. The purpose of this research is to develop a method of predicting time-dependence of the corrosion surfaces of uncoated weathering steel plates in various corrosive environments. Atmospheric exposure tests were carried out on the uncoated steel plates for 0.5, 1, 2 and 4-years in Okinawa Island, Japan. Spatial statistical analyses were carried out on the corrosion surfaces of the tested specimens. In addition to this, the time-dependence of the corrosion surfaces were simulated by the spatial statistical technique.