Hideyuki Kasano

Mechanical Performance of Steel-Concrete Composite Beams Subjected to a Hogging Moment

Limited experimental results have been reported in the literature on the fatigue and ultimate static loading behavior of composite beams subjected to negative bending moment. This paper examines experimentally the behavior of composite steel-concrete beams. Eight composite specimens were tested to study the various aspects of composite beams under a negative bending moment, including the effects of repeated loading, shear connectors (studs and PBLs), rubber-latex mortar coating, and steel fiber-reinforced concrete (SFRC) on their structural performance. Load versus midspan deflection, crack formation and its developing process, slip distribution on the steel-slab interface, and the flexural strain results of shear connectors were measured and studied. The test results show that the initial cracking-level repeated load did not show obvious effects, while the stabilized cracking-level repeated load can reduce the rigidity and loading capacity of composite beams. The experimental results indicate that the plastic bending moment criteria in the current AASHTO load and resistance factor design specifications are typically conservative for composite beams under a negative bending moment. In addition, the effects of SFRC on crack width control and adhesion bonding effects of rubber latex on the steel-slab interface were confirmed in the testing.

After-fracture redundancy analysis of an aged truss bridge in Japan

Abstract In the next 20 years, more than half of the bridges in Japan would be in service for more than 50 years. These include truss bridges those are generally considered to be non-redundant and fracture critical. With ageing, these bridges are facing an increasing risk of bridge collapse under extreme conditions. Therefore, it is essential to evaluate alternate load paths on existing bridge structures to avoid bridge collapse or replacement. In this paper, after-fracture redundancy of truss bridges is investigated through a case study for a five-span continuous truss bridge. Field tests were performed, and the displacements on key sections were measured in the test. According to the experimental observations and test results, a numerical model capable of simulating the present truss bridge was built and was used to investigate the after-fracture redundancy of the target bridge. Fracture of truss members in typical locations was considered in the numerical analyses, and the ‘R’ values of both intact and damaged trusses were compared. On the basis of the numerical results, a critical member in this bridge was also determined.

Consideration of heating source for application of active thermography to concrete structure

Two active thermographic inspection techniques, one using halogen lamp with light focusing setup and the other, CO2 laser heating, were compared for defect detectability in concrete structures located at a distance. Experimental results showed that inspection capabilities of both methods were similar when their heat input was similar. It was also found that the CO2 laser heating method was less susceptible to discoloration on the concrete surface in comparison with halogen lamp heating. This is considered an advantage of using the CO2 laser heating. In addition, use of phase images obtained by Fourier transformation of thermal data from both methods.

Reduced inspection time in active thermographic non-destructive testing of low-thermal-conductivity materials

Inspecting low-thermal-conductivity materials via active thermographic non-destructive testing requires a long inspection time because of the slow heat transfer in such materials. This study focuses on reducing the inspection time by using thermal waves with a high-frequency component. Fourier transform was applied to extract the high-frequency component from the observed thermal data. Consequently, it was observed from analytical studies and experiments of a carbon-fiber-reinforced plastic and a concrete specimen that using phase data in the high-frequency range obtained from the transformed data is effective for the detection of internal defects within a short inspection time.

Measurement of Corroded Gusset Plate Connection of Steel Truss Bridge and Evaluation for Its Corrosion State

Notable accidents that the diagonal members of the steel truss bridges have broken due to the corrosion damage have occurred recently. Therefore it is expected to establish the rational and efficient maintenance management technique depending on the bridge types and structure characteristics. In this study, for the corroded gusset plate connection of the steel truss bridge which was cut out from the steel truss bridge, we measured the corrosion shape in detail using the laser measurement equipment, and evaluated the actual state of the surface corrosion outside and inside of the gusset plate connection.