LOAD-BEARING CAPACITY AND DAMAGE BEHAVIOR OF RECTANGULAR STEEL-TUBE STRENGHTHENED RC COLUMNS UNDER LATERAL IMPACT AND STATIC PUSHOVER

In order to investigate the influence of steel tube position and other parameters on the dynamic and static mechanical properties of square steel tube reinforced concrete columns, fabricated were three types of specimens, namely, in-situ steel tube reinforced RC columns (ISRC columns), external steel tube reinforced RC columns (ESRC columns), and double tube reinforced RC columns (DSRC columns), with a total of six specimens; among them, four specimens were subjected to lateral static push-over tests and the other two specimens were subjected to pendulum impact tests. The impact tests were carried out on four specimens and two specimens. Obtained were the damage patterns, load-displacement curves, reinforcement and tube strains as well as mean curvature and shear strains of the specimens under different parameters. The test results show that: under static and dynamic tests, the specimens with a shear span ratio of 1.4 experienced different degrees of shear damage; the damage patterns of the specimens changed with the increase of the shear span ratio; and the load carrying capacities of the specimens were in descending order from ISRC columns, ESRC columns, and DSRC columns. The dynamic tests show that: the ESRC columns have the best ductility, the built-in reinforcement cage improves the ductility of the specimens, and the average curvature and average shear strain of the ISRC columns are the largest; and under the same impact energy, the displacement peak of the in-built steel column is the largest.