NEW RC PLATE SLAB - TO - CFT COLUMN CONNECTION, AND TOP-DOWN METHOD FOR CONSTRUCTING UNDERGROUND FLOORS OF BUILDING

摘要

A joint structure of a CFT(concrete filled steel tube) column and a reinforced concrete flat plate and a top-down construction method of a basement floor of a building using the joint structure of a CFT(concrete filled steel tube) column and a reinforced concrete flat plate are provided to reduce story height and to construct a basement floor of a building economically and quickly by maximizing the advantage of a CFT column and the advantage of a reinforced concrete flat plate. A joint structure of a CFT(concrete filled steel tube) column and a reinforced concrete flat plate is formed by attaching a shear bearing strap(11), transferring shear load from a reinforced concrete flat plate to a CFT column, to the outside of a CFT column(10) on a joint between a CFT column and a reinforced concrete flat plate(30), installing a shear connector(20) composed of a steel plate and many shear studs closely to the upper part of the shear bearing strap attached with the shear bearing strap to cover the outside of the CFT column before placing concrete for a reinforced concrete flat plate, and placing concrete for a reinforced concrete flat plate to make the shear studs of the shear connector buried under the concrete. A top-down construction method of a basement floor of a building using a joint structure of a CFT column and a reinforced concrete flat plate comprises the steps of: installing a pre-foundation column composed of a CFT column under the ground by perforating the ground and installing a casing, inserting a CFT column attached with a pier reinforcement cage and a shear bearing strap into the perforated hole, placing concrete around the pier reinforcement cage, placing soils around the CFT column in the hole and pulling out the casing inserted to the hole; excavating the ground using a top-down method; and joining a reinforced concrete flat plate forming a floor slab of each basement floor with the CFT column.