In order to repair and retrofit the aged metal bridge, it is important to undestand the mechanical behavior of aged steel and replacement of rivet to H.T.B. In this study, firstly, tensile loading tests, chemical tests of aged steel are conducted to understand the basic property of aged steel. Secondly, tensile loading tests for multi-bolted joint are conducted to clarify replacement of rivet to H.T.B. In this study, three specimens are fabricated and tested; all riveted joint, partially H.T.B replaced, and, fully H.T.B replaced. Based on the test results, it is found that load carrying capacity and deformability of partially and fully replaced to H.T.B can be improved due to adding frictional resistance comparing with riveted joints only.
Focuses of this study are bending behavior of hybrid steel girders in particular plastic responses. The hybrid steel girders consist of bridge high performance steel, SBHS700, flanges and lower strength, SM490 or SM400, steel webs, and their behavior is compared with SBHS homogeneous girder. The maximum bending capacities of the hybrid girders are 6% less than that of the homogeneous one. Significant differences are unshown between SM490 web hybrid and SM400 web hybrid in the plastic behavior; therefore, the bending capacity is mainly subjected to flange materials.
This study concerns with welded connections of high strength steel H-SA700. Since the strength of specified welding material for H-SA700 steel is less than the strength of base metal, the method of joining the high strength steel by undermatched welding is studied. In order to verify the strength of fillet weld joints for built-up members made by undermatched welds, loading tests of fillet welded joints and beam-to-column subassemblages were conducted and the validity of proposed methods to evaluate strengths of welded connections are examined.
In this paper, to clarify the effect of fatigue strength improvement by peening away from weld toe, plate bending fatigue tests under stress ratios R = 0, -1 and -infinity were carried out with out-of-plane gusset specimens. In the fatigue tests, the peening locations of 5 to 25 mm away from weld toe were considered. Furthermore, the effect of improvement of fatigue strength by peening on the back surface of the weld toe was also investigated. The fatigue test results showed the fatigue strength was significantly improved under the stress range of 80N/mm2 and stress ratio R = -infinity by peening 20mm away from weld toe or back surface of the weld toe.
We confirmed the mechanical behavior of steel concrete columns of symmetric and non-symmetric cross section through the structural tests under the axial load and the cyclic horizontal load. The experimental parameters were as follows, axial load level and shapes of cross section. The structural tests make it clear that the shape of the loops for steel concrete columns is spindle, and ductility decreases under the high axial compression. Moreover, we showed that ultimate flexural strength can be evaluated to superposed strength method, in which the ultimate strength of the section of steel flange, steel web and concrete, and proposed evaluation method of restoring force characteristics matches the test result well.
In this study, the use of high performance vises are proposed as two easy and temporal repair methods of repairing fatigue cracks in steel bridge members. These repair methods could temporarily decrease crack growth rate until executing permanent repair works. In this paper, to investigate the repairing effect of crack growth by the proposed methods, fatigue crack growth tests and FE analysis for MT and steel girder specimens were carried out. These results showed the proposed method could control the crack growth rate.
Initiating mechanism for fatigue cracks which initiated from the root of welded joints between deck plates and U-ribs and propagated toward the surface of the weld bead (bead-through cracks) has not been clarified yet. In previous study, bead-through cracks have been initiated by wheel load running test using large-scale specimen. In this study, the parts which had bead-through cracks initiated from the weld root and appeared to the surface of the weld bead have been cut away. Then, the bead-though crack origin was observed by macroscopic test. In addition, 3D FEA have been performed paying attention to weld root of specimens. As a result, when depth of weld penetration is small, bead-through cracks are easy to occur.
Recently, a number of fatigue cracks have been detected in orthotropic steel decks. Among them, fatigue cracking in the welded joint between steel deck and ribs or stiffeners is possible to propagate to deck plate and it has a risk to do harm to the traffic pass by on the deck plate. So, development of effective retrofit method is strongly needed. In this study, fatigue tests, and damage investigation were conducted to evaluate the fatigue cracking behavior in the welded joint and to verify the effect of proposed retrofitting method.
The authors investigated an influence of load range on fatigue crack initiation and propagation behavior from weld root into deck plate in orthotropic steel deck using model specimens for the connection between deck plate, transverse rib and trough rib. The results suggested that the difference in the behaviors due to load range were not recognized. It was considered that the results could be explained by that tensile residual stress occurred at the weld root from which fatigue crack initiated. In this study, effect of the stress relief annealing on the crack initiation and propagation behavior has been examined experimentally.
In this paper, focusing on a fatigue crack occurring in a main girder of a continuous steel girder bridge, assessed is the remaining structural safety of the steel bridge with such a fatigue crack. In this study, an elastic-plastic finite displacement analysis was carried out for the steel three span continuous non-composite girder bridge with four main girders with an observed long fatigue crack of about 1.1m in the web plate of the main girder during a inspection. From the analytical result, it was found that the load re-distribution function of the multi main girders system was very effective and the remaining load carrying capacity of the target bridge was enough not to cause a sudden collapse of the entire bridge.
This paper presents the shear stress distribution of the web and the ultimate shear strength for the plate girder with cross-sectional defects caused by local corrosion. Loading tests and nonlinear FEM analyses are conducted on the locally corroded plate girder cut from the railway bridge, which has been used for about 100 years. From results, it is concluded that the shear stress distribution can be obtained based on the beam theory, and that the ultimate shear strength can be evaluated from the buckling strength formula of shear plate without corrosion by substituting the representative web thickness into the formula, in which the representative plate thickness can be decided by the average thickness and the standard deviation in local corrosion area.
The high tension bolted joints of steel bridges can be often as weak points in respect of anti-corrosion maintenance. The authors have developed “Smart ZIC (SZ)” method which is coating system spraying metal powder toward the high tension bolted joints for their undercoating by cold spray technology. Metal powder in SZ is collides against base metal surface under its melting temperature point at supersonic speed. Zinc is regarded as undercoating material for the moment. Because metal powder does not reach to its melting point, material qualities of base metal don't change and high density or high adhesive strength of coating layer can be obtained. This paper reports about the outline of SZ and result of basically tests such as salt spray tests, mechanical tests and trial tests at field structures.
Energy dissipation devices, such as high-performance buckling-restrained braces (BRBs) are expected to withstand major earthquakes three times without being replaced. For implementing the devices to bridges and other steel structures, it is important to verify the effect of reducing structural response under a ground motion. In past studies, deformation capacity of BRBs was considered by axial loading test. This paper presents test results of the deformation capacity of BRB with inter-story drift in steel portal frame. Deformation of the BRBs installed at the frame, the bending moment acts on both ends of the BRB by the inter-story drift. By the present test, it was confirmed that the BRBs had good deformation capacities in the inter-story drift angle 0.02 under cyclic loading and additional bending.
A concept of composition of designable spaces that were already introduced by the authors is proposed and is demonstrated with a developed structural design system by means of a couple of the steel frame systems. This paper describes the secondary structural design system that deals with braced steel frames and non-braced steel frames. The sizes of structural members in the braced frames are smaller than those of the non-braced frames. The system was examined for some comparisons of the solutions with respect to situation of existence of steel brace. The paper concludes that the system is a useful tool for the novices in the structural design field because the composition of designable spaces provides them important information on the structural design.
Crevice corrosion between gusset plate connections and the flanges of diagonal members remains an unknown phenomenon. In this work, gusset plate connection, flanges of diagonal members and additional reinforcement plates were removed from a dismantled bridge for crevice corrosion measurements. The contact surfaces of two gusset plate connections, one standard upper connection and one lower connection with reinforcement, were measured in detail using laser equipment. From the results, the actual crevice corrosion state of these members were evaluated and graphs of corrosion depth distribution produced.