Xuchuan Lin

Investigation of Concrete-Filled Double-Skin Steel Tubular Columns with Ultrahigh-Strength Steel

Concrete-filled steel tubular (CFT) columns have been used increasingly in building structures because of their construction efficiency and provision of high stiffness and strength. A relatively new configuration design with inserted inner steel tubes, so-called concrete-filled double-skin steel tubes (CFDSTs), has been developed in the field. To promote the seismic capability of the CFT/CFDST columns further, the authors present results from an experimental investigation of CFT and CFDST columns using ultrahigh-strength steel. Eight scaled column specimens were examined by subjecting them to combined axial and flexural cyclic loadings. The performance of the CFT and CFDST design configurations using high-strength steel was comparable and both provide large moment capacities and elastic deformation capacities. The ultimate member moment capacity could be predicted accurately using a proposed simple formulation based on the concept of the superposed strength method. Various performance parameters are evaluated and discussed, and the influence of compressive strength of the concrete core, applied axial loads, and inserted inner steel tubes on the seismic behavior of the column members is clarified by the experimental results.

Bolted Built-Up Columns Constructed of High-Strength Steel under Combined Flexure and Compression

AbstractNew high-strength structural steel, named H-SA700, is utilized to achieve a structural system that enables continuous use after very large earthquakes. Columns are built up of H-SA700 plates using bolts only, and bolted connections are adopted extensively for easier replacement or reuse of structural components. An analytical study is performed to predict three distinctive local buckling modes of the column and estimate its elastic flexural stiffness, yield strength, and maximum strength subjected to combined flexure and compression. Cyclic loading behavior of the column is examined through five half-scale specimens, which vary with axial force, bolt pitch, and loading direction (about major or minor axis). The columns achieve a very large elastic rotation, approximately 0.02 rad at the axial force ratio of 0.2, and a maximum bending strength surpassing the plastic moment of the reduced section accounting for bolt holes without fracture. The proposed equations predict the local buckling modes well...