What Is a Core Barrel?

The core tube is in the central part of the building. The central core tube is formed by the elevator shaft, stairs, ventilation shafts, cable wells, public toilets, and some equipment enclosures. It forms an outer frame inner tube structure with the outer frame and is poured with reinforced concrete. This kind of structure is very conducive to structural stress and has excellent earthquake resistance. It is the mainstream structural form widely adopted by international super high-rise buildings. At the same time, the advantage of this structure is that it can strive for as wide a use space as possible, so that various auxiliary service spaces can be concentrated to the center of the plane, so that the main function space occupies the best daylighting position, and achieves good visibility and convenient internal transportation effect.

The core tube has a beam tube hollow-tube type and a reinforced concrete shear wall-type solid tube core tube composed of reinforced concrete dense columns.

1. Safe evacuation exit: closed stairs or smoke-proof stairs and front room;

2. Elevator, elevator hall and fire elevator front room;

3. Public walkways;

4. Equipment facilities and equipment tube wells.

In the United States, this type of structural system is considered unsuitable for high-rise buildings in earthquake areas, because there have been instances of engineering collapses in earthquakes; the entire country of Japan is in a high-intensity area, and this type of structural system is greatly restricted. If the construction of a reinforced concrete core tube-steel frame structure of more than 45 meters is required, strict examination and approval will be required for targeted research and careful implementation. From the attitudes of the two countries, it is necessary to think twice about adopting this form in the high-intensity earthquake zone.

Aside from the effects of earthquakes, if the horizontal action of the building is mainly wind loads, the structural system can effectively control the maximum acceleration in the downwind and crosswind directions under the wind load due to the existence of the concrete shear wall, which is more pure steel frame structure It is easy to meet the requirements of layer-to-layer displacement limitation, and good economic benefits can also be obtained in the structure cost ^[2]

1. The core tube should penetrate the full height of the building. The width of the core tube should not be less than 1/12 of the total height of the tube body. When the tube structure is provided with a corner tube, a shear wall or a member that enhances the overall stiffness of the structure, the width of the core tube can be appropriately reduced.

2. The core tube should have good integrity and meet the following requirements:

(1) Wall limbs should be arranged evenly and symmetrically;

(2) It is not suitable to open a hole near the corner of the cylinder. When it is unavoidable, the distance from the inner wall of the cylinder to the opening should not be less than 500mm and the cross-section thickness of the wall of the hole;

(3) The cross-section thickness of the outer wall of the core tube should not be less than 1/20 and 200mm of the layer height, and the bottom reinforced part of the primary and secondary seismic design should not be less than 1/16 and 200mm of the layer height. Appendix D of this code calculates the stability of the wall. If necessary, it is possible to add buttresses or buttress walls. When the bearing capacity requirements and axial pressure ratio limits are met (only for seismic design), the inner wall of the core can be appropriately thinned, but Should not be less than 160mm;

(4) The horizontal and vertical reinforcement of the cylinder wall should not be less than two rows;

(5) During seismic design, the coupling beam of the core tube should be equipped with cross concealed braces, horizontal joints, or reduced aspect ratio of the beam section to improve the ductility of the coupling beam.

3. In the seismic design, the seismic shear force of each layer of frame columns shall be adjusted in accordance with the provisions of Article 8.1.4 of this code.

4. Frame beams must be set between the surrounding columns of the frame / core tube structure.

5. The shear section of the core tube coupling beam shall comply with the requirements of Article 9.3.6 of this code, and its structural design shall comply with the requirements of Articles 9.3.7 to 9.3.8 of this code ^[3] .