Shigenobu Kainuma

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.

Study on environmental durability of rubber bearing for bridges

IABSE Symposium, Towards a Better Built Environment-Innovation, Sustainability, Information Technology, Melbourne, Australia, September 11-13, 2002（CD-ROM). 2002, p.268-269

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.

Corrosivity Evaluation of Steel Members near the Air-Liquid Interface Using a Ground Corrosion Sensor

In a previous study, the authors have developed a ground corrosion sensor to evaluate the corrosivity of steel members near the ground. This research aimed at the fundamental investigation of the output properties and practicality of a ground corrosion sensor. The output characteristics were verified by two electrochemical tests. The corrosion rates were evaluated using sensor measurements and indoor exposure tests by simulating NaCl aqueous solution environments, which contain air-liquid interfaces. Besides, the actual corrosion depths obtained from the exposure tests were compared with those estimated by the sensor. Moreover, an evaluation method for time-dependent corrosion depth prediction of steel members using the corrosion sensor was proposed.

Deterioration behaviors of overlapping layers between Al-5Mg alloy thermal spray coating and heavy-duty paint coating

The objective of this study is to clarify the deterioration behaviors of overlapping layers between Al-5Mg alloy thermal spray coating and heavy-duty paint coating. Combined cyclic corrosion tests were carried out on common carbon steel plates with overlapping layers. To evaluate the effective area of the sacrificial anode reaction caused by the thermal spray coating, machined straight-line defects with widths of 0.2, 6 and 12 mm were introduced in the overlapping layer. The experimental results indicated that the layers began to deteriorate from the lower part of the thermal spray coating along the defects. The deterioration of the thermal spray coating was accelerated by the sealing treatment. The blister area and height at the overlapping layer were significantly different depending on the sealing treatment.

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.

Relationships between Imperfections and Shear Buckling Resistance in Web Plate with Sectional Damage Caused by Corrosion

This study deals with the relationship between imperfections and shear buckling resistance of web plates with sectional damage caused by corrosion. To examine the imperfection effect on the shear buckling resistance of a web plate with sectional damage, a series of nonlinear finite element (FE) analyses were carried out for a web plate with sectional damage, which was assumed as local corrosion damage. For considering imperfections of the web plate in the girder, initial out-of-plane deformation was introduced in the FE analysis model. Using the FE analysis results, the changes in the shear buckling resistance of the web plate with sectional damage were quantitatively examined and summarized according to the aspect ratio, boundary conditions, and height of the damaged section of the web plate. The effects of web imperfections on the shear buckling resistance were evaluated to be little compared to that of the web plate without sectional damage. The shear buckling resistance was shown to significantly change in the high-aspect-ratio web plate. A simple evaluation equation for the shear buckling resistance of a web plate with sectional damage was modified for use in the practical maintenance of a web plate in corrosive environments.

Corrosion Pattern for Critical Shear Buckling Load of a Web Panel with Local Corrosion Damage

Shear buckling strength of a web panel with local corrosion damage can be changed by web corrosion pattern. In this study, To find critical corrosion pattern for shear buckling of a web panel with local corrosion. Critical shear bucking loads of the corroded web panels were quantitatively evaluated. Thus, FE analsyis models were creasted cosidering corrosion pattern in the plate girder bridge which was reported from the corroded bridge inpection. As corrosion pattern of the web panel in the plate girder bridge, three corrosion patterns were selected as main corrosion cases such as longitudinal, vertical, and triangular cases. Their critical shear buckling loads were compared according to their corroded web codition.

Fatigue behavior of out-of-plane gusset joints with one side fillet weld

In previous studies, many fatigue tests have been performed to investigate the fatigue behaviour of out-of-plane gusset welded joints. However, fatigue behaviour of out-of-plane gusset joints with a one-side fillet weld has not yet been clarified sufficiently. In this research, in order to quantitatively clarify the behaviour, welding residual stress at the weld toes of the joint was measured by a cutting method. In addition to this, fatigue tests were carried out on the joints with a one-side weld and turn-around weld. The plate thickness is 9 mm and the weld size is 10 mm. Moreover, finite element stress analyses were conducted on the test specimen models and parametric models with different main plate and gusset plate thickness. Their results show that fatigue cracks for out-of-plane gusset joints with a one-side fillet weld initiate from both weld toes at the start and end points of weld beads and non-penetration weld of the gusset side. Also, the crack initiation points are different depending on the weld arrangement; however, their fatigue strengths are almost same.

Practical method for estimating corrosion depth of uncoated carbon steel using thickness of the corrosion-product layer

The corrosion environments of individual parts of members in a steel structure vary significantly. Therefore, efficient maintenance requires accurately evaluating these environments and predicting corrosion damage over time. This research focused on comprehensively evaluating the corrosive environment of each part of members in the structures based on the mean corrosion depth of uncoated steel plates mounted on the members. Atmospheric exposure tests were conducted in four exposure fields in which the environments varied widely as a function of rainfall and airborne sea salt. Based on the test results, a practical method of estimating the mean corrosion depth using the thickness of the corrosion-product layer on the mounted plates that does not require removal of the corrosion product is proposed. Furthermore, a method for estimating the time-dependence of corrosion depth for parts of the members after deterioration of the paint coating is proposed.