THE STRUCTURAL SYSTEMS OF TALL BUILDINGS

    Structural systems in the early twentieth century buildings were basically designed to resist vertical loads. Today, thanks to developments in this field and to high-strength materials, with the increase in the height of buildings and the decrease in their weight, wind and earthquake-induced lateral loads have become the primary loads, especially in tall buildings, and have begun to pose more of a threat than before. As a result, for structural engineers, providing the strength to resist lateral loads in tall buildings, whether wind or earthquake-induced, has become an essential input in the design of new structural systems. 

    Buildings can be classified on the basis of the materials used in their structural systems (structural materials of the columns, beams, shear trusses (braces), shear walls and outriggers) as: 

1. Steel 
2. Reinforced concrete 
3. Composite

    Taking as a basis the columns, beams, shear trusses (braces), shear walls, and outriggers that are the elements of the main vertical and horizontal structural systems, buildings can be categorised as being reinforced concrete buildings where these elements are made of reinforced concrete, or as steel buildings where these elements are made of steel. 

    Tall building structural systems:

1.  Rigid frame systems
2. Flat plate/ Slab systems
3. Core systems
4. Shear wall system
5. Shear frame system
6. Shear trussed frame (Braced frame) system
7. Shear walled frame system
8. Mega column (mega frame, space truss) systems
9. Mega core systems
10. Outrigger frame systems 
11. Tube systems 
12. Framed-tube systems 
13. Trussed-tube systems 
14. Bundled-tube systems

I. Rigid frame systems

    Rigid frame systems, also called moment frame systems, are used in steel and reinforced concrete buildings. This system consists of beams and columns. A rigid frame is an unbraced frame that is capable of resisting both vertical and lateral loads by the bending of beams and columns. Stiffness of the rigid the frame is provided mainly by the bending rigidity of beams and columns that have rigid connections. Rigid framing is based on the principle that beam-column connections have adequate rigidity to hold the original angles between intersecting members unchanged under the effect of both vertical and lateral loads. Thus, reinforced concrete is an ideal material for this system by virtue of its naturally monolithic behaviour, resulting in inherent rigidity at connections. For steel buildings, rigid framing is achieved by reinforcing beam-column connections.

II. Flat plate/slab systems

    Flat plate/slab systems are used in reinforced concrete buildings. This system consists of beamless floor slabs of constant thickness and columns. Shear walls also can be placed in addition to or instead of the columns.

III. Core systems

    Core systems are used in reinforced concrete buildings. This system consists of a reinforced concrete core shear wall resisting all the vertical and lateral loads.

IV. Shear wall systems

    Shear wall systems are used in reinforced concrete buildings. This system consists of reinforced concrete shear walls, which can be perforated (with openings) or solid. Shear wall systems can be thought of as a vertical cantilever rigidly fixed at the base, and can resist all vertical and lateral loads on a building without columns.

V.  Shear-frame systems

    Rigid frame systems economically do not have sufficient resistance against lateral loads in buildings over 25 storeys because of bending on columns that cause large deformations. In this case, the total stiffness and so the economical height of the building can be increased by adding vertical shear trusses (braces) and/or shear walls to the rigid frame to carry the external shear-induced by lateral loads.

 

    The shear trussed frame (braced frame) system consists of rigid frames and diagonal braces in the form of vertical trusses, while the sheer-walled frame system consists of rigid frames and reinforced concrete shear walls that are perforated or solid.

For more learn, please visit the links below: