Toshiyuki Kitada

Ultimate strength and ductility of state-of-the-art concrete-filled steel bridge piers in Japan

Briefly in this paper are described the difference in local buckling modes between cross-sections of steel and composite (concrete-filled steel) columns, the difference in cross-sections between composite columns in bridge piers and buildings, structural details of standard steel and composite columns for bridge piers, construction of composite bridge piers (bridge piers with composite columns), and the characteristics of stiffness, ultimate strength and ductility of composite piers in Japan. Reconstruction and repair using composite columns for reinforced concrete (RC) and steel piers, which collapsed or were damaged due to the Hyogoken-Nanbu earthquake which occurred on 17 January 1995, are introduced. Future research needs are also summarized for developing more rational seismic design methods for composite piers.

Experimental study on ultimate strength and ductility of concrete filled steel columns under strong earthquake

Abstract After the shock of the Hyogo-Ken Nambu Earthquake, a newly revised Japanese Seismic Design Method for Bridge Structures requires that steel bridge piers should not suffer serious damage due to such strong earthquakes. As one of the suitable methods to meet this requirement, a method of inserting an additional steel tube into the inside of a steel bridge pier can be considered. In this method, the ductility of the bridge pier is significantly enhanced, if the cross section is designed in such a manner that the axial compressive load, caused by the dead load of the superstructure, is mainly carried by the inner steel tube and the local buckling of the outer steel pier as well as the column buckling of the inner steel tube are prevented by the encased concrete between them. To investigate the ultimate strength and ductility of these concrete-filled steel box columns under strong earthquakes, an experimental study is executed.

New technologies of steel bridges in Japan

Abstract Introduced in this paper are (1) some computer programs for static/dynamic elasto–plastic finite displacement analyses used in designing steel bridge structures, (2) the ultimate strength and design methods of steel plates, stiffened plates and columns made of high strength steel subjected to compression, (3) seismic design and retrofitting methods of new and existing steel bridge piers after the Hyogo-ken Nambu Earthquake, and (4) friction type joints and tension type joints with high strength bolts and development of high performance high strength bolts in Japan. These are some topics which the authors are concerned with among new technologies of steel bridges under development in Japan, such as development of high performance steel, new fiber materials, new types of bridges, performance based design methods, seismic design method against earthquakes of level 2 like the Hyogo-ken Nambu Earthquake, and bridge management system.

Seismic retrofitting techniques using an energy absorption segment for steel bridge piers

Importance has been attached to seismic design methods considering the ductility of steel structures after the Hyogo-ken Nambu Earthquake and one of the design methods is adopted into the design method of steel bridge piers in Japan. On the other hand, it is necessary to retrofit the existing steel bridge piers not satisfying the design standard and having inadequate ductility. This paper deals with seismic retrofitting techniques for the existing steel bridge piers to be retrofitted in cases where concrete filling technique is untenable. Instead of the concrete filling technique, proposed are two seismic retrofitting techniques installing a small part or a short segment, to which major plastic deformation is limited, in a column member of the steel bridge piers for enhancing the ductility capacity of the column member. The validity of the proposed techniques is investigated through a cyclic loading test and a pseudo-dynamic test. Various applications and variations of the techniques are also discussed.

Elasto-plastic analysis of orthogonally stiffened plates with initial imperfections under uniaxial compression

In general, the stiffened plates consisting of steel plate elements are unavoidably accompanied by initial imperfections such as residual stress and initial deflections, which have considerable effects on their ultimate strength. Therefore, it is needed for designing them to develop more rational method taking the ultimate strength influenced by initial imperfections into account rather than the conventional design method being on the basis of the linear elastic buckling theory. From this point of view, this study aims to evaluate rigorously the ultimate strength of orthogonally stiffened plate with initial imperfections under uniaxial in-plane compression. The elasto-plastic finite element method is applied to attain this purpose. By a happy combination of modal analytical technique and conventional finite element method, much reduction of the degree of freedom can be expected to be realized herewith. Some numerical calculations are performed by means of this rigorous method to examine the exactness of the analysis. Moreover, the numerical results are compared with the experimental ones.(a) (TRRL)

Experimental study on ultimate strength of stiffened plates subjected to longitudinal tension and transverse compression

Abstract The ultimate strength of steel plates with longitudinal stiffeners of open or closed cross-section subjected to both longitudinal tension and transverse compression is experimentally investigated in this study. Four stiffened plate specimens on the scale of one-third, corresponding to that of the steel deck plate in an actual Nielsen Lohse bridge, were tested by using an experimental apparatus newly developed for this study. The test results verify a practical design method, which the authors developed for predicting the ultimate strength of stiffened plates subjected to biaxial in-plane forces.

Ultimate strength of box stub columns under combined actions of compression, bending and torsion

Abstract This paper presents the experimental studies on the ultimate strength of thin-walled box stub columns subjected to the combinations of compressive, bending and torsional forces. For these purposes, an experimental apparatus is developed and the features are detailed together with the test specimens. Through the test results of box stub columns under various loading conditions, the properties of their ultimate strength are summarized.

Ultimate Strength Interaction Curves of wide Steel Decks Subjected to Biaxial In-Plane Compressive Forces and two kinds of Live Load

ABSTRACT : The effect of transverse inplane compressive stress on the buckling strength of wide steel decks in bridges has to be considered in their design as the width of the steel deck becomes larger. Moreover, not only biaxial in-plane stresses but also wheel live loading should be considered in their design against the buckling strength of wide steel decks. However, there are no specifications for their design. This paper deals with the ultimate strength and its interaction curves of stiffened plates subjected to the biaxial in-plane compressive stresses and wheel loading for the purpose of providing reference data for developing an appropriate design method against the buckling of these wide steel decks.

Analytical Study on Mechanical Behavior of Semi-Rigid Column Anchor Connections with High Strength and High Ductility Long Bolts

and High Ductility Long Bolts Shugang SONG, Takashi YAMAGUCHI, Toshiyuki KITADA and Kunitaro HASHIMOTO (Shinko Wire Company) Steel Construction Engineering, Vol. 12, No. 46, pp.59-68 (2005) (in Japanese). In this research, high strength and high ductility long bolts with waisted shank are applied to semi-rigid column anchor connections as a type of long bolted tensile connections. The mechanical behavior of the semi-rigid column anchor connections with the waisted shank long bolts is investigated by a FEM analysis considering the contact/non-contact behavior between the bottom base plate and the footing concrete. Discussed in the paper is the effect of the long high strength bolts with waisted shank on the ultimate strength and the behavior up to the ultimate state of the anchor connection of the column specimens subjected to bending. The performance of the column anchor connection with high strength bolts with waisted shank is compared with that of the connection with normal high strength bolts. The connection with high strength bolts with waisted shank can increase the ultimate horizontal displacement of the top of the column specimens with this type of anchor connection and improve energy absorption capacity due to the high deformability compared with the column specimens with the anchor connection by normal high strength bolts.

EFFECT OF TENSILE FORCE AND SHEAR FORCE ON BENDING STRENGTH AND STIFFNESS OF HIGH STRENGTH BOLTED TENSILE JOINTS

高力ボルト引張継手では, 予め, 高力ボルトに高い軸力が導入され, 継手面には材間圧縮力が発生する. したがって, 引張力あるいは圧縮力などのボルト軸方向の外荷重のみではなく, せん断力に対しても摩擦接合として抵抗するため, 高力ボルト引張継手は, これら以外の断面力も伝達できる多面的な継手形式と言える. しかし, この種の継手に関する既往の研究の多くは引張力のみを対象としており, 組合せ荷重下での検討は十分になされていない. したがって, 本研究では, 本継手を実構造物の接合法として適用するために, 実際に近い荷重状態下での力学的挙動を, 断面力として, 引張, 曲げ, およびせん断力を想定し, これらを作用させた載荷実験により明らかにし, 実橋部材の継手構造に適用可能であることを確認した.