Nozomu Taniguchi

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.

Rehabilitation and Restoration of Old Steel Railway Bridges: Laboratory Experiment and Field Test

Preventive maintenance on aged steel railway structures is all important due to their long service time after completion. This paper introduced a strengthening method for old steel railway bridges by using rubber-latex mortar, glass fiber reinforced polymer (GFRP) plates, lightweight rapid hardening concrete, and reinforcing bars. Both laboratory tests and field tests were performed to confirm the effects of the present strengthening method. In total, two old railway bridges were employed in this study. One of them has been in service for around 100 years. The static loading test was performed in the laboratory. Experimental results, including load-deflection response, strain distribution on the structural steel, GFRP plates as well as concrete, were given and compared between the original steel railway bridge and the strengthened bridge. Theoretical results were also provided to make a comparison with the experimental results. Both the experimental and theoretical results indicated that the present renovation method could greatly enhance the rigidity and reduce the stress levels of old steel members, resulting in the extension of the residual service life of the old steel railway bridge. In addition, field tests were performed on the other old railway bridge, which has been used for 86 years, and stress variation on the railway bridge under the running train was measured and the effects of the present strengthening method in the real service condition were also confirmed.

Effects of Bridge Accessories in Steel–Concrete Composite Railway Bridges in Service Condition

Abstract Bridge accessories, such as parapets, service ducts, and track slabs, are commonly used in railway bridges, but their real effects on the structural behavior of the bridges are still unknown because very few studies have been reported on this significant aspect. In engineering practice, lack of information on the contribution of bridge accessories may cause problems for bridge design, bridge health evaluation and monitoring, bridge management and operation, and bridge maintenance. Given this background, field tests were performed on a railway bridge with typical bridge accessories to confirm their contribution to bridge rigidity (or stiffness), as well as their effects on the sectional normal strain distribution. Both displacements in the midspan and strain results on key sections were measured in the field test and reported in this paper. Based on the field test observations, a numerical model capable of simulating the present railway bridge was built and was used to investigate the effects of t...

Renovation of existing steel railway bridges: Field test and numerical simulation

Renovation of the aged steel railway structures is of vital importance due to their long service life after completion. A strengthening method for aged steel railway bridges by using rubber-latex mortar, glass fiber–reinforced polymer plates, lightweight rapid hardening concrete, and reinforcing bars was introduced in this article. To confirm the real effect of the present strengthening method, field tests were performed on two aged steel railway bridges that have been in service for 87 and 61 years, respectively. Stress variations on the mid-span section of the railway bridge due to the running trains were measured in the field test, and the stress reduction effects as well as the load redistribution effects of the present strengthening method were also confirmed. Three-dimensional finite-element models were built, and the numerical results were in good agreement with the field test results. Besides, structural vibration and noise levels of both strengthened and un-strengthened railway bridges were measured, and the noise reduction effect of the present method was confirmed in the field tests. In addition, further nonlinear analyses were performed, and the applied load–displacement relationships as well as the load–normal longitudinal strain curves of the aged structural steel, the glass fiber–reinforced polymer plates and the rapid hardening concrete, were given. Both experimental and numerical results indicate that the present renovation method can greatly enhance the stiffness and reduce the stress levels of steel members, resulting in the extension of the residual service life of the aged steel railway bridges.