In this paper, the effects of repair with carbon fiber reinforced polymer (CFRP) for steel pipes having partially cut-out are investigated through axial loading tests. Firstly, the axial compression and tensile tests of steel pipes are carried out. Secondly, the effects on axial stiffness, strength, yield stress and stress concentration are made clear. Finally, it is confirmed that axial stiffness and yield stress significantly increase using CFRP even if it is adhesively bonded to steel pipes on the outside surface. It would be suggested that the present reinforcing method provides the reasonable and useful procedure for corroded steel pipe members.
Effect of high frequency peening treatment with a small radius tip pin, which is less than 3mm radius tip pin, still remains unclear, although the effect of ultrasonic impact treatment on fatigue strength has been investigated. The objective of this study is to investigate the effect of ultrasonic needle peening with a 1.5mm radius tip pin on fatigue strength of out-of-plane gusset by using bending fatigue tests. The results show that the treatment can improve fatigue strength, when mean stress is not changed after the treatment is carried out. It also shows that the effect of the treatment become less with increasing mean stress after the treatment is carried out, and when the treatment is not sufficient at weld toe.
This paper is concerned with base-isolation and vibration control system with passive friction dampers settled at the steel column bases of a building. The cost of the new base-isolation system is lower than that of the past one because of omitting the base-isolated layers. However, the new base-isolation system has some problems that the slip load changes in conjunction with the varying axial force of the columns and the residual displacement is not negligible. Numerical study of vibration control by base-isolation system with sliding in steel column bases is conducted. Finally, the paper concludes that the new system is effective in the base-isolation design of steel structures.
It is a burden to go through the inside of box girders, especially to pass the small opening in diaphragms, during the inspection or maintenance work. This report represents a consideration for the larger size of opening in diaphragms compared with conventional one under the conditions that it satisfies the required distortional resistance of box girder. Finite element analysis is carried out to confirm the principal factors to control distortional strength of box girder, changing the shape, size and location of opening in diaphragms. On the basis of the results of FE analysis, the rational and inspector-friendly structure of diaphragms is proposed.
In out-of-plane gusset welded joints, fatigue cracks usually initiate from the boxing weld toes at which high stress concentration exists. The fatigue strength can be enhanced by making shape of boxing weld toe smooth with grinding process. In this case, fatigue crack initiation points sometimes move to weld roots from weld toes. This research is aiming at proposing the method to prevent root fatigue failure of out-of-plane gusset welded joints with ground toes through fatigue tests on model specimens and parametric FE analyses for obtaining effective notch stresses at weld roots and weld toes.
The authors proposed one technique for reduction of stress concentration at stop hole edges which is closing the crack surface between stop holes by using ICR treatment. To evaluate the effectiveness of proposed method, bending fatigue tests of stop hole with ICR treatment were carried out. As the results of bending fatigue tests, fatigue strength of stop hole with ICR treatment was 3 times higher than that without ICR treatment. Additionally, to estimate fatigue strength of stop hole with ICR treatment, estimated equation of stress range of stop hole with ICR treatment was proposed. Fatigue life can be accurately estimated by using the proposed equation.
For developing high-strength bolted friction joints with much higher friction coefficients than conventional ones, basic slip tests are conducted by changing the values of contact pressure for friction joints with aluminum-sprayed splice plates. The results show that friction coefficients of aluminum-sprayed friction surface in the area of higher contact pressure are lower rather than conventional friction coefficients. These results are in accordance with a previously-proposed friction theory.
A huge number of steel bridges were constructed in Japan during the period of high economic growth from the 1950s to the 1970s. As these bridges age, deterioration and damage resulting from heavy traffic and the effects of the natural environment are also increasing rapidly. Improved techniques related to inspection, diagnosis, repair, reinforcement and appropriate maintenance of such bridges are urgently needed. In the case of steel truss bridges, serious corrosion damage has been reported recently, especially on diagonal members and at gusset plate connections. In this study, detailed corrosion profiles of four gusset plate connections removed from a dismantled steel truss bridge are obtained using laser measurement equipment. The corrosion state of the connections is evaluated on the basis of the corrosion depth distribution over their surfaces．