A multistory building higher than 21 mtr or 21 to 29 floor buildings with unknown height described as high-rise structure. Various structural systems are available to be used in the construction of high rise building. In this article, different types of high rise structural systems are presented.
Types of High-Rise Buildings Structural Systems
Braced frame structural system
- Braced frames are cantilevered vertical trusses resisting laterals loads primarily diagonal members that together with the girders, form the “web” of the vertical truss, with the columns acting as the “chords’’.
- Bracing members eliminate bending in beams and columns.
- It is used in steel construction.
- This system is suitable for multistory building in the low to mid height range.
- efficient and economical for enhancing the lateral stiffness and resistance of rigid frame system.
- This system permits the use of slender members in a building.
- An outstanding advantage of braced frame is that, it can be repetitive up the height of the building with obvious economy in design and fabrication.
- However, it might obstruct internal planning and the location of doors and windows. That is why it shall be incorporated internally along with lines of walls and partitions.
Rigid frame structural system
- In rigid frame structure, beams and columns are constructed monolithically to withstand moments imposed due to loads.
- The lateral stiffness of a rigid frame depends on the bending stiffness of the columns, girders and connections in-plane
- It is suitable for reinforced concrete buildings.
- It may be used in steel construction as well, but the connections will be costly.
- One of the advantages of rigid frames is the likelihood of planning and fitting of windows due to open rectangular arrangement.
- Members of rigid frame system withstand bending moment, shear force, and axial loads.
Wall-frame system (dual system)
- It consists of wall and frame that interact horizontally to provide stronger and stiffer system.
- The walls are usually solid (not perforated by openings) and they can be found around the stairwells, elevator shafts, and/or at the perimeter of the building.
- The walls may have a positive effect on the performance of the frames such as by preventing a soft storey collapse.
- Wall-frame system suitable for buildings with storey number ranges from 40-60 storey which is greater than that of shear or rigid frame separately.
- braced frames and steel rigid frames provide similar advantages of horizontal interaction.
Shear wall system
- It is a continuous vertical wall constructed from reinforced concrete or masonry wall.
- Shear walls withstand both gravity and lateral loads, and it acts as narrow deep cantilever beam.
- Commonly, constructed as a core of buildings
- It is highly suitable for bracing tall buildings either reinforced concrete or steel structure. This because shear walls have substantial in plane stiffness and strength.
- Shear wall system is appropriate for hotel and residential buildings where the floor-by floor repetitive planning allows the walls to be vertically continuous.
- It may serve as excellent acoustic and fire insulators between rooms and apartments.
- shear wall structural system can be economical up to 35 stories building structure.
Core and outrigger structural system
- Outrigger are rigid horizontal structures designed to improve building overturning stiffness and strength by connecting the core or spine to closely spaced outer columns
- The central core contains shear walls or braced frames.
- Outrigger systems functions by tying together two structural systems (core system and a perimeter system), and render the building to behave nearly as composite cantilever.
- The outriggers are in form of walls in reinforced concrete building and trusses in steel structures.
- Multilevel outrigger systems can provide up to five times the moment resistance of a single outrigger system.
- Practically, Outrigger systems used for buildings up to 70 stories. Nonetheless, it can be used for higher buildings.
Infilled frame structural system
- Infilled frame structure system consists of beam and column framework that some of the bays infilled with masonry, reinforced concrete, or block walls.
- Infill walls can be part-height or completely fill the frame.
- The walls may or may not be connected to the formwork.
- Great in plan stiffness and strength of the walls prevent bending of beams and columns under horizontal loads. As a result, frame structural performance will be improved.
- During an earthquake, diagonal compression struts form in the infills so the structure behaves more like a Braced Frame rather than a Moment Frame.
- It can build up to 30 storey buildings.