The authors focused on a highstrength bolt friction joint with a countersunk head that can smooth the joint surface and prevent functional deterioration due to corrosion. In this study, the slip behavior and maximum resistance of a joint with a long bolt were investigated. It was concluded from the experimental result that the slip coefficient did not change because only a small amount of yielding around the slip coefficient does not change because only a small yielding occurs around the bolt holes when the bolt is long. Although the bolts failed in only one shear plane, there was no significant reduction in maximum bearing capacity compared to the design value of two-plane shear failure.

The purpose of this study is to clarify the structural performance of concrete-filled box section column to beam connection panel made of ultra-high strength steel (H-SA700B) assembled by undermatched welds. We conducted monotonic loading tests and experiments in which a constant axial force and repeated shear forces were applied to the beam-to-column connection of a cruciform subassemblage. Experimental parameters include strength of the weld metal at corner joint, width-to-thickness ratio, panel aspect ratio and others. Based on the results, it is revealed that a CFT panel assembled by undermatched welds has the sufficient performance for practical use. Furthermore, the shear strength equations, which can evaluate the effect of the weld metal strength at corner joints of panel, were proposed.

In this study, the specimens made by tightening stainless steel high-strength bolt 10TSUS on carbon steel SM490Y plate were used. Also, epoxy resin plate and alumina spraying were adopted as the insulation method to prevent the corrosion of dissimilar metal contact, which is a concern at the contact part of different materials. Then, a combined cycle test was conducted using eight types of specimen conditions under which these conditions were changed, and the corrosion properties were investigated in detail. As a result, it was clarified that no clear phenomenon of the corrosion depth of the base carbon steel plate near the washer and the insulating material was observed in any of the insulation methods.

Tsunami countermeasures of bridges have not been established yet, especially for the lift caused by water flow. This study proposed a new method to reduce lift by installing steel pipes on the upstream side of the girder with fairings. The effect of this measure was verified through the hydraulic tests using a scale model. The results showed that the fairing reduced the drag, and the attached pipe reduced the lift efficiently. However, the bearing capacity for the generally designed bridge was still insufficient for the estimated lift. The insufficient strength for the lift was found to be covered by connecting the pipe to the girder with cables.

Applicability of paint-coating removal by using a heating device on bolted joints was investigated. The heating of 200 degrees Celsius by the arranged device as wrapping each bolt was effective for removing the paint coating on the bolted joints. There was little change of bolt tightening force due to heating. An effective paint coating removal procedure was proposed for the joints with 9 x 6 bolts. A group of 6 bolts in the joint specimen were heated up to 200 degrees Celsius. After that, the paint coating of these bolts was removed. During this removal work, the next group of 6 bolts were heated. By repeating this procedure, the waiting time of heating could be used effectively.

It is well known that residual stresses and the geometric imperfection have an effect on the ultimate strength of steel structures. This study analyzed the change of residual stress and deformation under partial cross-section loss process at an end stiffener of rolled Hbeam using finite element method. As a result, release of compression residual stress in the partial loss area was observed under the process. Released residual stress was re-distributed to a web and stiffeners around the area. Under the process, the partial loss area caused out-of-plane bending deformation as if it was squashed. Therefore, it was revealed that this behavior might reduce the ultimate strength of the H-rolled beam end.

In the maintenance of cable structures such as cable-stayed bridges, it is necessary to estimate the cable tension. In current practice, the cable tension is estimated from natural frequencies using the higher-order vibration method. However, this method cannot be applied to a cable with a damper. Therefore, the authors proposed a tension estimation method for a cable with a damper in a previous study. However, it was found that the method does not work for some cases even though they are rare. This study revealed the reason why the previously proposed method does not work for some cases and proposed a method to solve this difficulty.

Lateral-torsional buckling of a composite beam is observed after fracture of the headed studs and/or cone failure of the concrete slab around the studs occurs. This paper proposes a method to calculate acting forces of the headed studs from the out-of-plane deformation of the beam as a feasibility study to predict the occurrence of such failure of the studs. Equations for calculating the forces of the studs are derived based on the equilibrium of sectional forces in a free body ofH-shaped steel beam taken from a composite beam. The validity of the proposed equations is confirmed by comparing FEA that can reproduce the previous loading test of a composite beam.

This paper shows fatigue strength of lean duplex stainless steel base metal. Lean duplex stainless steel is inexpensive by reducing the rare element Ni and has higher tensile strength than that of SUS304. In this study, fatigue tests were carried out using smooth base metal test specimens made from steel plates of SUS323L, SUS821L1 and SUS304. As a result, fatigue strength of lean duplex stainless steel is higher than that of SUS304 as static strength increases when the stress ratio is zero. In addition, fatigue strength at two million cycles in case of the stress ratio with 0.3 is smaller by at least 80 MPa than that with the stress ratio of zero. Then, from obtained test data, a fatigue design curve applicable to lean duplex stainless-steel base metal is proposed.

Steel structures constructed during the period of high economic growth have been aging for more than 50 years since construction, and corrosion has been found at the boundary of concrete in steel piers. Previous studies have confirmed by seismic response analysis of steel bridge piers with a rectangular cross section that the corrosive damage at the corners reduces the seismic performance of steel bridge piers. Therefore, in this study, the effect of corrosion damage at the edge of concrete of steel bridge piers with a rectangular crosssection was investigated in detail on the buckling behavior and seismic performance of structure.