Study on Seismic Characteristics of Partially Concrete-Filled Steel Bridge Piers with Thin-Walled Stiffened Cross Section

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(1)The concrete-filled steel column specimen consisting of stiffened plates with the width-thickness parameter R=0.7 had about 1.2 times the ultimate strength, 1.9 times the ductility, and 2.7 times the hysteresis energy of the corresponding steel column specimen with the same steel cross section and without encased concrete.(2)The deterioration of the strength of a bridge pier under cyclic loading becomes significant at the loading levels where a component stiffened plate in the pier buckles, and then a crack occurs in welding part at the corners of the cross section or the column base.(3)The height of the encased concrete in the concrete-filled steel bridge piers should be determined according to the distributions of the applied and resistance bending moments.(4)Longitudinally stiffened plates can effectively be used in the concrete filled steel bridge piers, because the local buckling of the longitudinal stiffeners are prevented by the encased concrete.(5)The steel bridge piers with … More stiffened plates of R=0.7 may be seriously damaged by such strong inland type earthquakes such as the Hyogo-Ken Nambu Earthquake.(6)Local buckling occurred in stiffened plate with R=0.7 in the upper steel part of the steel column specimen filled partially with concrete in the lower quarter of the column height by using studs, when it was subjected to large horizontal displacement in one direction. The effect as a composite column can not be expected in the case of this failure mode in the steel part.(7)The maximum response acceleration of the bridge piers under consideration is about 1.3 times the maximum seismic acceleration at their pier bases.(8)The ultimate strength of the steel column specimen with stiffened plates having R=0.7 decreased substantially at a few number of loading cycles because of a longitudinal crack at a corner of the cross section occurred, while a transverse crack occurred at welding part on the column base in the case of the steel column specimen consisting of the stiffened plates of R=0.35. Welding of thess parts should, therefore, be designed and fabricate against not only strength but also adequate ductility.(9)The ultimate strength and ductility of steel bridge piers consisting of the stiffened plates of R=0.35 does not decrease substantially, even after the action of such strong earthquakes such as the Hyogo-Ken Mambu Earthquale.(10)The seismic design method in the Japanese Specification for Highway Bridges is apt to conservative one against the inland type earthquakes of level 2 and type II. Less