Yao Cui

Hysteretic Behavior and Strength Capacity of Shallowly Embedded Steel Column Bases

A series of shallowly embedded steel column base consisting of an exposed column base and a covering reinforced concrete floor slab were tested under horizontal cyclic loading to very large deformation. By adjustments to the floor slab thickness, shape, and reinforcing bars in the slab, the initial stiffness, maximum strength, and dissipated energy of the shallowly embedded column base increase significantly with respect to those of the exposed column base. It is found to be practical to strengthen the shallowly embedded column base so that it would behave like a fully embedded column base. Punching shear failure in the floor slab around the column due to the uplift of the base plate occurs when the shallowly embedded column base fails. Based on the plastic theory, a mechanical model that considers the contributions of the anchor bolts and the bearing and punching shear of the floor slab is proposed to evaluate the maximum strength. The evaluated results have good agreement with the test results, with errors not greater than 20%.

Using Steel Fiber Reinforced Cementitious Composite (SFRCC) in Shallow Embedded Column Base

Exposed column bases in Japan are commonly covered with lightly reinforced concrete (RC) slab, whose effect is neglected in seismic design so far. However, many experimental investigations showed that the strength, stiffness and energy dissipation are increased by the contribution of the RC slab. In this study, steel fiber reinforced cementitious composites (SFRCC) is employed for the covered slab to further improve the behavior of exposed column base. Here, 0.4 mm×12.0 mm and 6% volume fraction straight steel fibers were adopted for SFRCC. Eight specimens, one exposed, three concrete and four SFRCC specimens, are tested. The test parameters included slab material and reinforcement ratio (size and strength of steel bars).