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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 measu...

Japanese highway bridge design codes have been modified a lot since the Hyogoken-Nanbu Earthquake in 1995, but only used for designing new bridges. The aged steel piers constructed with old design code should be strengthened appropriately to adopt with current design code. With the purpose of improving the seismic performance of existing steel piers, a preventive seismic retrofit method by using GFRP plate, rapid hardening concrete, rubber-latex mortar, and reinforcement is proposed in this paper. The static loading tests on the steel piers before and after strengthening were performed to confirm the effects of the present strengthening method. Moreover, three- dimensional FE models were built to make a comparison study between the strengthened and the original steel piers. Load versus deflection relationship and sectional strain distribution on the piers were measured and compared between original piers and strengthened piers. Both experimental and numerical results indicate that the present strengthening method can greatly enhance the stiffness and reduce the stress levels of steel pier, resulting in the extension service life and improvement of the seismic performance of aged steel piers.

Structural repairing or maintenance technique has been a hot issue in recent years due to the increasing aging problems of old railway bridges. A strengthening method for welded joints in old steel railway bridges by integrating the rapid hardening concrete, rubber-latex mortar, and reinforcing bars is introduced in this paper. The purpose of the present study is to investigate the mechanical performance of the strengthened connection joints in old steel railway bridges. Depending on the locations of the concrete and possible loading conditions, the joint needs to sustain both negative and positive bending moment, therefore, two experimental plans were employed. The static loading tests on the steel joints before and after strengthening were performed to confirm the effects of the present strengthening method. Moreover, three-dimensional FE models were built to make a comparison study between the strengthened and original steel joints. Load versus deflection relationship and strain development process on the web of the joints were measured and compared between the original joints and the strengthened joints. Both experimental and numerical results indicate that the present strengthening method can greatly enhance the stiffness and reduce the stress levels of steel joints, resulting in the extension service life of aged steel railway bridges.

All-ceramic ball bearings with silicone nitride balls and silicone nitride rings were tested and the vibration characteristics were compared with those of hybrid ceramic ball bearings and conventional steel ball bearings. The vibration measurement results showed that the overall vibratory velocity levels of the all-ceramic ball bearings are influenced by rotational velocities, and do not change with axial loads. Under a given axial load and rotational velocity, the overall vibratory velocity level of the all-ceramic ball bearing is the lowest, and the hybrid ball bearing the highest. The frequencies of main peaks in the measured vibration spectra of the all-ceramic ball bearing are higher than the frequencies of the corresponding main peaks for the hybrid ceramic ball bearing and the steel ball bearing. To explain the main peaks, modal analysis was done and the relationship between peak and natural vibration was analyzed. The results of the analyses showed that the main peaks are caused by: (1) the mass-type natural vibration of the outer ring in the vertical direction, (2) the bending natural vibration of the outer ring in the radial direction, (3) the moment of inertia-type natural vibration of the outer ring in the angular direction, (4) the mass-type natural vibration of the outer ring in the axial direction, and (5) the bending natural vibration of the outer ring in the axial direction. We also discuss the generating mechanism of the vibration and present the calculation method of the vibration spectra. As a result, it is clear that the vibration spectra of the all-ceramic ball bearing are determined by the amplitude of the waviness of the raceways and ball surface, the mobility, and the non-linear spring constant associated with the contact between the raceways and balls.

This research offers a new composite revamping method for railway bridges by assuming composite remodelling process of existing steel bridges having no specific fissure damages or serious corrosions and effectively making use of relatively new materials to it. Effects of noise reduction and improved stiffness were further confirmed through hammer impact tests (vibration measurement tests) and loading tests in order to prove the efficacy of the composite remodelling.