A new type of cable-supported bridge, the cable-stayed arch bridge, is proposed. This new bridge is a combination of a cable-stayed bridge and an arch bridge, and the girder is supported by both stay cables and arch ribs. Its static behaviors, sectional forces and deflections, under the design load are compared with that of conventional cable-stayed bridges and arch bridges. Non-linear analysis is then conducted to obtain the ultimate strength. The cable-stayed arch bridge has smaller sectional forces and deformation under the design load and has sufficient ultimate strength. The cable-stayed arch bridge is modified by inclining the arch planes 15 degrees from the vertical axis, which increases ultimate strength.
This study focuses on effects of product tolerance of high strength bolted friction type joint that contains extremely thick plates to its slip strength. The statistical values of tolerance are summarized by investigation of the result of past researches on slip tests of the joints. The sensitivity analysis is conducted based on the value. Some effects of tolerance to the strength, such as the tolerance of Young’s modules of steel plate, slip coefficient and axial forces of bolts, are large. And, it is also shown that the effects of tolerance are different according to structural dimensions of the joint.
From around 2000, fatigue cracks originating from weld roots between trough ribs and deck plates have been detected in the vicinity of the intersection to lateral ribs of steel plate decks. The authors made clear the fatigue crack initiation and propagation behavior from the weld root into deck plate and suggested that thickening the deck plate and installing scallop made fatigue durability high. In the study, load range of 50kN which was larger than actual wheel load was used for fatigue tests on model specimens. In this study, fatigue tests on the specimens same as the previous one have been performed under load range of 35kN, and an influence of load range on fatigue crack initiation and propagation behavior has been discussed.
A design detail of beam-to-column connections is developed for previously proposed built-up column member comprising high-strength H-SA700 steel connecting to conventional-steel beams. In the design concept, the beams are allowed to develop plasticity during the large earthquakes, while the built-up column remains elastic. A bolted connection detail, consisting of steel end plates and high tension bolts, is adapted to connect the beams to the joints. Experiments were conducted to examine the seismic performance of the beam-to-column connections with the built-up column. Test results show that additional T-shape stiffeners were needed at the beam-to-column connections to provide appropriate rigidity of the joint to ensure the yielding of the beams.
Current defect assessment procedures based on fracture mechanics usually assume flaws to be infinitely sharp. While this assumption may be appropriate for fatigue cracks, it can be an over-conservative assumption and give a large safety factor for non-sharp flaws such as porosity or weld undercut because of the loss of plastic constraint. Fracture toughness tests are performed for four types of single edge notched bend steel specimens with different degrees of plastic constraint caused by a machined-notch and a shallow notch. This paper shows the ability of the Weibull stress approach to predict brittle fracture under both high and low plastic constraint conditions. The Weibull stress approach predicts the effects accurately.
A system that controls the rocking behavior of multistory shear walls is proposed as an innovative damage-control system for cold-formed steel structures. In this system, we have developed a new hold-down equipped with a fuse function (HDF) that controls the rocking behavior, and is placed on the foundation of multistory shear walls. The HDF contributes to reducing damage to both structural and nonstructural members in cold-formed steel framed buildings, dissipating seismic input energy in the event of a large earthquake. The present paper describes the static tests performed using HDF specimens and folded-steel sheet walls specimens with the HDFs. It has been confirmed, from the test reuslts, that the shear walls systems using the HDFs have high energy-dissipating performance in comparison with the exiting shear wall systems.
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. This paper presents results of the earthquake response analysis of single-story steel portal frame with BRBs. The BRBs are designed in consideration of the similarity rule, and paid attention to the difference in the inner setup of the frame. Two kinds of setups, obliquely setup and inverted V-shaped setup were considered. By the present testing method, it was confirmed that the designed BRB had good energy dissipation performance and showed difference of seismic control capacity.
Vertical stiffeners are usually welded to deck plates to prevent out-plane-buckling of webs in an orthotropic steel deck bridge. When wheel loads locate on close to the stiffener, high stress concentrations occur in connections between deck plates and vertical stiffeners because the stiffener restricts the bending deformation of deck plate. In this study, fatigue tests and stress analyses on model specimens of the connection have been performed in order to reproduce the cracks observed in the actual decks and clarify the propagating behavior of the fatigue cracks. In addition, the effect of finishing the weld toe has been also examined, and fatigue crack originating point is discussed using effective notch stress conception.
In order to maintain the soundness of the steel bridges in Japan rationally on the limited budget, the method which can do the effective preventive maintenance based on the degradation characteristic of the steel bridges and extension of life-span needs to be performed. This research analyzes periodic inspection results of the steel bridges on national roads of almost all of Japan from a viewpoint of an elucidation of the degradation characteristic. The transition probability of soundness which presumed time-homogenious as a premise differs greatly for every kind and environmental condition of damage. Moreover, the factor which has influence dominant in degradation by a multivariate analysis was not able to be specified.