The University of Osaka · Engineering
Professor Mikihito Hirohata's research lab specializes in structural integrity and durability of steel structures, with a focus on corrosion behavior, residual stress control, and fatigue performance enhancement in steel bridges and civil engineering infrastructures. The lab conducts experimental and numerical studies on accelerated corrosion testing, induction heating for residual stress reduction, and advanced joining techniques such as bonding-assisted welding. Their work aims to improve the safety, service life, and maintenance efficiency of existing steel structures through innovative field-applicable thermal treatments and corrosion monitoring methods.
Figures are computed from collected data and may differ slightly.
The corrosion of bridging structures affects their stiffness and load-carrying capacity. Hence, predicting the degree of corrosion is critical for their reliability and safety. This study examined the applicability of the newly developed accelerated corrosion test authorised by ISO 16539 Method B for evaluating the corrosion characteristics of the weathering structural steel. The non-coated weathering steel was subjected to 28, 84, and 168 days of accelerated cyclic corrosion test. The same stee
This paper presents experimental and numerical investigations on the characteristics of residual stresses generated by induction heating (IH) on 12 mm thick steel plates. IH at 250 °C and 350 °C provided high tensile residual stresses in the heating field but high compressive stresses away from the heating field. The double heating case generated higher compressive residual stresses—around 200 MPa—than the single heating case because of the superposition of the compressive residual stresses. It
In order to investigate and evaluate the corrosion characteristics of steel members more effectively under seawater conditions, the authors have developed an accelerated exposure experimental system to simulate under seawater environments. The acceleration coefficients of this experimental system were based on a study of the depths of corrosion actually found in structural steel members exposed to seawater environments for over 19 years. The accelerated coefficient for the splash zone was around
A series of fatigue experiments and elastic analysis were carried out for investigating fatigue characteristics of patch plate joints assembled by fillet welding assisted with bonding. In the case that fatigue cracks occurred at the weld toe by the four-point bending fatigue experiment, the fatigue life of joints assembled by welding and bonding (WB) specimens were almost the same as those by only welding (W) specimens. The elastic analysis simulating the four-point bending loaded situation on W
To improve the fatigue life of welded joints in steel bridges, a series of experimental and analytical investigations was conducted on a method of welding residual stress reduction by local heating with an induction heating (IH) device. The IH coil of 110 mm x 40 mm was installed around the fillet weld and heated to 350 °C. The tensile residual stress of about 340 MPa was reduced to under 30 MPa. The local heating experiment was simulated by the thermal elasto-plastic analysis to examine the mec
One thousand two hundred cycles of accelerated exposure experiment with combined salt water spray simulating atmospheric corrosion was performed for investigating the effect of weld line direction and paint orientation on the corrosion and paint deterioration characteristics of welded part of the steel. The corrosion depth of the weld toe of transverse weld line became 1.35 times as large as that of the base metal part because of the remained salt water on the weld toe. The coating thickness at
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