Tetsuhiko Aoki

Local buckling strength of closed polygon folded section columns

Abstract The local buckling behavior of regular polygonal, short length steel columns, fabricated by welding two half sections made of folded steel plates, is described. The polygonal sections are composed of five different section profiles with four to eight sides and each profile having component plates with one to four varied width-to-thickness ratios. A total of 15 specimens are used in the compression test, sustaining uniform compression stress in the fixed end condition. Accurate measurements of welding and cold-forming residual stresses and geometric imperfections were taken prior to testing and are presented in this paper. The test strengths are compared with the current plate buckling code in Japan and with the ECCS recommendations for unstiffened circular cylinders. The empirical design formula based on the test data is also presented to predict the local buckling strength of the polygonal section columns.

Innovative Use of Profiled Steel Plates for Seismic Structural Performance

This paper presents the innovative use of hot-rolled thickness-tapered mill products, longitudinally profiled (LP) plates, for the seismic performance of bridge bents of single and portal framed piers. The study involves the inelastic cyclic testing and numerical analysis of tested beam-columns and portal frames in order to evaluate the effects of tapering ratios of LP plates, penetration of yielding, and number of locally buckled panels on their structural ductility. A structural design method is proposed for the portal frames having LP panels under cyclic loadings.

Curve-Approximated Hysteresis Model for Steel Bridge Columns

AbstractA curve-approximated hysteresis model of the lateral load-displacement behavior of steel bridge columns is proposed for nonlinear seismic response assessment of single-column-type bridges using single-degree-of-freedom (SDOF) analysis. Instead of multiple straight lines, a series of curves are adopted to precisely describe complicated force-displacement hysteresis behavior of the column. The P-δ effect, hardening effect in unloading-reloading hysteresis loops, deterioration of strength, and stiffness are taken into account. Parameters of proposed hysteresis model for three types of steel column specimens used in this study are calibrated by six quasi-static cyclic tests. To verify the accuracy of the proposed model, eleven pseudodynamic tests are conducted. By comparing the simulation and the test results, the differences between the predicted nonlinear seismic response using the proposed model and pseudodynamic tests are found to be, on average, 5% in maximum response displacement, 22% in residua...

Multiple-Spring Model for Square-Section Steel Bridge Columns under Bidirectional Seismic Load

AbstractIn this study, the multiple-spring (MS) model with the curve-approximated hysteresis rule is proposed for the nonlinear seismic response simulation of bidirectionally loaded hollow square-s...

Seismic performance upgrading of steel arch bridges using brace dampers against longitudinal directional earthquake motions

Publisher Summary The chapter discusses the seismic performance upgrading of steel–arch bridges using brace dampers against longitudinal-directional earthquake motions. Seismic performance upgrading and retrofit approaches are of great significance for aseismic consideration for steel–arch bridges against major earthquakes. The chapter presents a seismic performance upgrading approach for steel–arch bridges using buckling-restrained braces as dampers against longitudinal-directional earthquake motions. Inelastic behavior of a representative steel–arch bridge with buckling-restrained braces is investigated by three-dimensional modeling time-history analyses and compared with the result from the original structure. It is found that the replacement of diagonals of some parts by buckling-restrained braces can greatly improve seismic performances of the steel–arch bridge.