We devised three types of postearthquake modifications for exposed steel column bases which resisted bending moment and shear force, and investigated the effects of the modifications experimentally. For column bases damaged by shear force, the following two modifications were planned; 1) a modification using shear-resisting plates welded under a steel base plate, and 2) a modification of cladding a column base with a reinforced concrete stub. For a column base damaged by bending moment, a modification of cladding the column base with a concrete stub and fixing steel plates to the outside of the concrete stub was adopted. The effects of these modifications on the strength, deformation capacity and stiffness of the column bases were discussed using the results of premodification and postmodification tests.
Hanshin Expressway Public Corporation provides toll roads extending 200 km in the Osaka Kobe (Hanshin) area that are traveled by an average of over 900, 000 vehicles daily. Some of the toll roads were constructed almost thirty years ago and have started to suffer minor damage hem and there. To locate such damage, all the structures of Hanshin Expressway have been inspected every five to seven years, regardless of their time in service. The occurrence of damage varies widely depending on the design standards current when the structures were designed. This has prompted Hanshin Expressway to divide the routes into three groups mccording to the design standards appliod; and to inspect the groups every 4, 6 or 8 years. The intention is to maximize the structure inspection efficiency by differentiating the inspection periods according to the historical occurrence of damage, thus spreading the inspection effort and making best use of the inspection budget
Hanshin Expressway Public Corporation provides toll roads extending 200 km in the Osaka-Kobe (Hanshin) area that are traveled by an average of over 900, 000 vehicles daily. Ninety-two percent of the total road length in service is elevated and 79% of it makes use of steel structures. Some of the toll roads were constructed almost thirty years ago and have started to suffer minor damage due to deterioration and poor road alignment peculiar to urban highways with much heavy-duty traffic. This paper reports on the current situation of damage to the steel structures of Hanshin Expressway based on recent inspection results. Emphasis is placed on cracks and corrosion among different types of damage ;trends and the degree of damage are classified.
In this paper, enhancement of Yubm-bashi bridge, 191.5 meter in bridge length and 2 main Gerber girders out of 7 spans, is reported. The enhancement work for a main girder is indispensable for the span elongation due to building a new pier in order to replace an existing pier. It is also discussed that the reason why high strength steel bar is employed for the enhancement. Furthermore, the monitoring control system of the work is described. Finally, applicability of the high strength steel bar for the enhancement work is considered by comparing FEM analysis results and observed one.
The elastic-plastic large deformation behavior and the collapse load of a tubular trussed tower which has legs of unequal length and mechanically severe shape is studied by a numerical analysis. An original method for three dimensional steel structures and members with closed thin walled section is used to investigate the behavior. It is shown that the tower designed by a conventional method has a sufficient strength for the design loads.
The buckling and post-buckling analyses of a compression member with a lateral bracing with eccentricity were performed, considering the elasto-plastic behavior of the compression member with a elastic lateral suport. The results obtained are as follows: 1) If the bracing stiffness is larger than 2.0 Kco(basic stiffness), bracing force is smaller than 2% of the maximum strength of the compression member, expect for the long compression members having large eccentric bracing, at the buckling stage. 2) At the post-buckling stage, the lateral bracing force increases with the increase of the buckling deformation. The necessary stiffness and strength of the bracing increase, as the eccentricity of the bracing increases.
In designing cylindrical structure such as chimney-stacks, as well as storage tanks, it is very important to accurately predict the buckling strength and collapse strength of axially compressed cylindrical shells, especially with initial imperfections. This paper investigates the effects of large initial imperfections on the buckling and collapse strength of axially compressed cylindrical shells, utilizing the finite element analysis. Main conclusions obtained from this study are as follows; (1) The effects of large initial imperfections, such as several times of shell thickness, are clarified. (2) The larger the ratio of radius to thickness of shells (R/t) are, the more sensitive to the initial imperfections the buckling strength of cylindrical shells are. (3) The circumferential buckling mode number gets large according as R/t ilarge or magnitude of imperfection gets large. (4) In the case of small imperfection, the axial length of imperfection when the cylindrical shell has the smallest buckling strength is 4√Rt. But in the case of large magnitude imperfection, it becomes larger than 4√Rt.
This paper presents the design method of shear-connectors in composite 2-I steel girder bridges. First, a three-span continuous composite bridge model is analyzed by 3-dimensional FEM and the characteristics of the behavior of shear-connectors is shown. Authors presents the simple method to obtain the stress resultants produced in the shear-connectors such as the longitudinal shear forces, the transverse shear forces and transverse bending moment. Finally, the present paper propose the design procedure for the shear-connectors.
Automation has recently extensively developed in bridge fabrication. No less than 70 % of welding work for assembly of girders of I-section is performed by automatic welding at present. In the case of girders of box-section, only the panels composing them are fabricated in assembly lines with robots. The automatic welding has, however, not been fully utilized for formation of box section, because it is difficult to manipulate the welding machines inside, their interior structures are complicated, and the feasibility of use of the automatic welding has been regarded to be too low. Instead, manual welding has generally been used for this purpose, but welders are obliged to work under very adverse circumstances in this case. In this paper the authors propose a method using robots for welding in the interior of box-girders, for which simulation by 3-D/CAD is conducted and also various suggestions related to the assembly lines equipped with robots are presented.
This paper shows the behavior of composite steel structures filled up with concrete under unit impulse. Combining Finite Strip Method and Finite Element Method, we can analyze dynamic response of composite shell structures having arbitrary shapes. Impulsive stress propagates as group waves. The group waves influenced by the direction and position of the unit impulse can be explained clearly by strain energy generated in the structures. The characteristics of wave propagation and group wave are discussed by using strain energy.