High Rise Cantilever System - Everything you need to know - explained with video - The Builder (2023)

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The stabilizers are internal.structural systemsSupplied to improve the rigidity and tilt resistance of skyscrapers. It is a lateral load resistance system located inside the building. The entire system consists of a central frame connected to the exterior columns of the building by structural members called stabilizers. Outriggers can be in the form of horizontal beams, trusses, or walls.

Watch the video of the stabilizer structural system here >>

Outriggers are classified as internal structural systems capable of efficiently operating up to 150 stories. It is one of the successful and stable configurations used in the construction of skyscrapers. The Outrigger structural system has been popular in construction since the 1980s due to its unique combination of architectural flexibility and structural efficiency.

This article examines the principle of operation and important properties of structural stabilizer systems.

Cantilever Structural Systems

In a high-rise building, a stabilizing structure works, connecting two systems to each other (see Figure 2), i.e.

1. Central System
2. perimeter system

As shown in Figure 1, the core structure is the most critical unit of a tall building. It is a combination of units like elevators, stairs, channels, etc. The perimeter system is a combination of mega pillars. The central system and peripheral megapillars are connected by stabilizers. Figure 2 shows a truss type stabilizer connected to the perimeter column. In addition to the anti-roll bars, the frame is accompanied by belts around the perimeter for added lateral strength.

Both the central and the perimeter system, together with the stabilizer, control the behavior of the entire building. This is achieved through positive interaction between the core and perimeter systems via stabilizers.

Principle of cantilever structural systems

Skyscrapers are subject to large lateral deformations from wind or seismic loads. The core structure of a tall building undergoes cantilever deformation as shown in Figure 3, while portal structures around the core undergo portal-like deformation. This causes large drift and overturning effects in the structure.

The installation of roll bars effectively controls excessive drift due to side loads. This can prevent structural and non-structural damage to the structure. As shown below, stabilizer bars reduce top-down central moment under side load.

The static effect of stabilizer systems in tall buildings is based on the tension-compression couple induced in the exterior columns, as shown in Figure 5. A structure without a lateral support system may overturn under lateral loads.

Figures 5 and 6 show a skyscraper structure with a stabilizer structure system. Here the stabilizers act as a rigid arm connected to the perimeter column. Wraps around the outer columns and central core for safe load transfer. When a structure with a stabilizer bar system is laterally loaded, the lateral force is transferred from the main structure through the stabilizer bars to the perimeter supports and then to the ground. In this way, the total overturning moment is reduced.

The performance of the structure stabilization system depends on:

1. building height
2. Depth of stabilizer elements
3. Primary structural material of the structure.
4. The number of levels of stabilizers deployed

Types of stabilizer systems.

Based on the location and arrangement of the stabilizers in tall buildings, the stabilizer system can be divided into the following types:

1. Conventional stabilizer system

In a conventional cantilever support system, the cantilevers are attached directly to the central structure and the columns located on the periphery of the structure.

The 492m-high, 101-story Shanghai World Financial Center, designed by Leslie E. Roberston Associates in 2008, is one of the famous structures that integrates the traditional stabilization system in eight different building levels.

2. Staggered cantilever structure system

In this system, the stabilizers are located in places other than the planes of the core walls. This arrangement retains all the benefits of the stabilizers and reduces the lateral deviation of tall buildings compared to the traditional stabilizer system.

For an efficient stabilizer bar system, the stabilizer arm and bottom plate must be rigid enough to transmit shear in the horizontal plane on the plates between the stabilizer bar and the core. When a building with a bent stabilizer system is loaded laterally, the forces of the slab cause the stabilizer to break. To counteract this, perimeter supports create a couple of constraints. This restraining pair of perimeter buttresses extends through the plates to the central structure.

The offset column system was used in the construction of the Dubai Tower, Doha, which is 438 m high and has 90 floors. It is a combination of conventional structural system and plywood stabilizer.

3. Virtual cantilever system

In a virtual stabilizer bar system, the tipping moment is transferred from the core structure to the supports without a direct connection between the core and the peripheral supports. This is achieved by lower discs, which transfer the overturning moment from the core to the outside through a horizontal couple.

Another type of virtual sway bar system are belt mounts. Tape backs are constructed by joining the peripheral columns as shown in Figure 1 and Figure 10.

Characteristics of the structural system of stabilizers

The stabilizers connect the central and perimeter structural system, creating a unique design that provides solutions to the problems in skyscraper construction. Some of the properties of structural stabilizer systems are:

1. The stabilizer system is used for buildings subject to large overturning moments compared to lateral and shear deflections.
2. Stabilizers on structures reduce overall drift and main wind moments.
3. The stabilizer system reduces the general acceleration of the building due to high winds and improves the comfort of the occupants.

Benefits of the stabilizer structural system

Some of the benefits of structural stabilization systems are:

1. A tall building with a stabilizing structural system can reduce the overturning moment by 40%.
2. Reduces overall building drift during side loading. The lowering depends on the relative stiffness of the core and the stabilizer bar.
3. The stabilizer bar system wraps around the perimeter frame pillars to efficiently reduce rollover moment.
4. The stabilizer structural system helps distribute overturning loads effectively to the foundation. Therefore, this reduces the resistance in the foundation of the core.

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