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In this work, seismic performance of conventional X-braced frames is enhanced by using Drawer Bracing Systems (DBS). DBS is an innovative structure, which increases ductility and energy absorption capacity of the X-braces through elimination of the harmful effects of local and global buckling and by converting the induced axial forces inside diagonal arms to flexural moments. Two half-scale specimens are tested under cyclic loading and the seismic performance of an X-shaped DBS is compared to that of an X-braced frame. Both braced frames are designed for equal nominal base shears and have similar frame sizes and dimensions. Test results confirm that converting the axial force to flexural moments in rational dissipative elements inside braces helps prevent the global and local buckling of braces in X-shaped DBS. Consequently, ductility and energy absorption capacity of the Concentrically Braced Frames (CBFs) is increased remarkably. [ABSTRACT FROM AUTHOR]

When reinforced-concrete columns are subjected to lateral cyclic loading, columns usually suffer failures at plastic hinges. If the buckling of longitudinal reinforcements at plastic hinges can be prevented or delayed, columns are expected to carry gravity loads at a higher ductility level. In this study, the rebar-restraining collar (RRC) was developed to improve the post-buckling behavior of longitudinal reinforcements. The behavior was investigated under monotonic loading tests of reinforcing bars with the RRCs and the cyclic loading tests of two reinforced-concrete bridge columns with and without RRCs. From the monotonic loading test, it was found that the RRCs significantly improved the post-yielding behavior of longitudinal reinforcing bars. The ductility and energy dissipation of longitudinal reinforcing bars with RRCs was significantly higher than that of the bare bar. Then, cyclic loading tests of two reinforced-concrete bridge columns were conducted. The cross section of columns was 0.4 m × 0.4 m, and the effective height was 2.15 m. The ratio of longitudinal reinforcing bars was 0.0123, and the volumetric ratio of transverse reinforcement was 0.00424. The column with RRCs did not have buckling of longitudinal reinforcements and had the ductility enhancement of about 17%, comparing to the column without RRCs. One evident benefit of using the RRCs is to control damage at plastic hinges of columns. Hence, the repair cost of columns after an earthquake can be reduced. [ABSTRACT FROM AUTHOR]