Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (2023)

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Outriggers are interior lateral structural systems provided to improve the overturning stiffness and strength of high-rise buildings. It is a lateral load resisting system that is located within the building. The whole system consists of a core structure connected to the perimeter columns of the building by means of structural members called outriggers. The outriggers can be in the form of horizontal beams, truss, or walls.

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Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (1)

Outriggers are categorized as interior structural systems that can work efficiently for up to 150 floors. It is one of the successful and stable configurations used in high-rise construction. Outrigger structural system is popular in construction since the 1980s due to its unique combination of architectural flexibility and structural efficiency.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (2)

This article explores the working principle and important features of outrigger structural systems.

Contents:

  • Outrigger Structural Systems
  • Principle of Outrigger Structural Systems
  • Types of Outrigger System
    • 1. Conventional Outrigger System
    • 2. Offset Outrigger Structural System
    • 3. Virtual Outrigger System
  • Features of Outrigger Structural System
  • Benefits of Outrigger Structural System
  • FAQs
(Video) Outrigger Structural System for High-Rise Buildings

Outrigger Structural Systems

An outrigger structure functions in a high-rise building by tying together two systems (see Figure-2), namely,

  1. Core system
  2. Perimeter system

As shown in Figure-1, the core structure is the most critical unit of a high-rise building. It is a combination of units like lifts, staircases, ducts, etc. Whereas the perimeter system is a combination of mega columns. The core system and mega columns located in the perimeter are connected using outriggers. Figure-2 shows a truss type outrigger connected to the perimeter column. Other than outriggers, the structure is accompanied by belt trusses around the perimeter to provide extra lateral resistance.

Both the core and perimeter systems together with the outrigger control the behavior of the whole building. This is performed by the positive interaction between the core and the perimeter system through outriggers.

Principle of Outrigger Structural Systems

High-rise buildings are subjected to large lateral deformation either due to wind or seismic loads. The core structure of a high-rise building is subjected to cantilever deformation, as shown in Figure-3, while the frame structures surrounding the core are subjected to portal type deformation. This causes high drift and overturning effects on the structure.

The incorporation of outriggers efficiently controls the excessive drift due to lateral loads. This, hence, allows to prevent structural and non-structural damage in the structure. As shown below, outriggers reduce the core moment from top to down under the lateral load.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (3)

The structural action of outrigger systems in high-rise buildings is based on the tension-compression couple induced in the outer columns, as shown in Figure-5. Under the action of lateral loads, a structure without any lateral support system is subjected to overturning.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (4)
Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (5)
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Figure-5 and 6 show a high-rise structure with an outrigger structural system. Here, the outriggers act as a stiff arm that connects with the perimeter column. It engages the outer columns and the central core for safe load transfer. When a structure with an outrigger system is subjected to lateral load, the core structure's lateral force is transferred to the perimeter columns via outriggers and then to the ground. This way, the overall overturning moment is reduced.

The performance of outrigger structural system is dependent on the:

  1. Height of the building
  2. Depth of outrigger members
  3. Primary structural material of the structure
  4. The number of levels of outriggers provided

Types of Outrigger System

Based on the location and arrangement of outriggers in tall buildings, the outrigger system can be classified into the following types:

1. Conventional Outrigger System

In a conventional outrigger structural system, the outriggers are directly connected to the core structure, and the columns located at the periphery of the structure.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (6)

The 492 m-high, 101-story Shanghai World Financial Centre, designed by Leslie E Roberston Associates in 2008, is one of the famous structures that has incorporated the conventional outrigger system at eight different building levels.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (7)

2. Offset Outrigger Structural System

In this system, the outriggers are situated in locations other than the planes of the core walls. This arrangement retains all the advantages of outriggers and is observed to reduce the lateral deflection of tall buildings than conventional outrigger system.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (8)

For an efficient offset outrigger system, the outrigger arm and the floor slab must be rigid enough to transfer the horizontal plane shear in the slabs between the outrigger and the core. When a building with an offset outrigger system is subjected to lateral loads, the slab forces cause a couple in the outrigger. To counteract this, a restraining couple is created by the perimeter columns. This restraining couple from the perimeter columns goes back through the slabs to the core structure.

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Offset outrigger system has been used in the construction of Dubai Tower, Doha, which is 438 m-high with 90 floors. It is a combination of conventional and offset outrigger structural system.

3. Virtual Outrigger System

In a virtual outrigger system, the overturning moment is transferred from the core structure to the columns without a direct connection between the core and the peripheral columns. This is achieved using floor diaphragms, which transfer the overturning moment from the core to the outboard using a horizontal couple.

Another type of virtual outrigger system is belt trusses. Belt trusses are constructed by tying the peripheral columns as shown in Figure-1 and Figure-10.

Outrigger Structural System for High-Rise Building: All You Need to Know: Explained With Video - The Constructor (9)

Features of Outrigger Structural System

The outriggers tie together the core and the perimeter structural system creating a unique design providing solutions to high-rise construction problems. Some of the features of the outrigger structural systems are:

  1. Outrigger system is adopted for buildings that are subjected to large overturning moments compared to shear and lateral deflections.
  2. Outrigger in structures reduces the overall drift and core wind moments.
  3. The outrigger system reduces the overall building acceleration due to high winds and improves occupant comfort.

Benefits of Outrigger Structural System

Some of the benefits of outrigger structural systems are:

  1. A tall building that employs an outrigger structural system can reduce overturning moment by 40%.
  2. It reduces the overall drift of the building during lateral load action. The reduction is dependent on the relative rigidity of the core and the outrigger.
  3. The outrigger system engages the perimeter columns of the structure to reduce the overturning moment efficiently.
  4. Outrigger structural system helps to distribute the overturning loads to the foundation effectively. This hence reduces the force at core foundations.

FAQs

What is an outrigger structural system?

Outrigger structural system is an interior lateral load resisting system that is located within the interior of the building. It consists of a core structure connected to the perimeter columns of the building by means of structural members called outriggers. The outriggers can be in the form of horizontal beams, walls, or truss.

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What is an outrigger and belt truss?

Outriggers and belt truss are two lateral load resisting systems used in high-rise buildings. Both serve the purpose of improving the turning stiffness and strength of the building. Outriggers connect the core structure of the building to the perimeter columns, while belt truss tie up the perimeter columns around the core structure.

What are the types of outrigger structural systems?

The main types of outrigger structural systems are:
1. Conventional outrigger system
2. Offset outrigger system
3. Virtual outrigger system

What are the advantages of using outriggers in high-rise building construction?

Outrigger structural system provides the following benefits to the building structure:
1. Reduction in overturning moment
2. Reduction in lateral drift
3. Safe reduction and transfer of core structure forces to the foundation

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FAQs

How do outriggers work on a building? ›

Outriggers increase the stiffness of buildings by means of converting the lateral forces into push (compression) and pull (tension) forces in the perimeter structures. Hence, outriggers are required to resist reverse and cyclic load- ing.

What is the outrigger system? ›

The outrigger systems are lateral loads resisting systems that can effectively minimize the lateral loads and strengthen tall buildings. In this system, the external and the internal structure couple as a whole to resist lateral loads.

What is the structure system in high-rise building? ›

The structural system of a high-rise building is designed to cope with vertical gravity loads as well as lateral loads caused by wind or seismic activity. The structural system consists only of the members designed to carry the loads, and all other members are referred to as non-structural.

What is outrigger beam? ›

An outrigger is a stiff beam that connects the shear walls to exterior columns. When the structure is subjected to lateral forces, the outrigger and the columns resist the rotation of the core and thus significantly reduce the lateral deflection and base moment, which would have arisen in a free core.

What angle should outriggers be set at? ›

It also helps to match the angle of one outrigger to the other. The recommended angle is 35 degrees off the vertical. If you angle the outrigger too far back, it will decrease the amount of height and spread you will have in the fishing position. Rake-back angles greater than 45 degrees are not recommended.

How do you stabilize outrigger beams? ›

The inboard ends of the suspended scaffold outrigger beam shall be stabilized by bolts or other direct connections to the floor or roof deck, or they shall have their inboard ends stabilized by counterweights.

What are the parts of an outrigger? ›

Anatomy of an Outrigger Canoe
  • ama (float/outrigger)
  • hoe (a paddle; to paddle)
  • 'iako (spars, boom)
  • manu kupe (curved end pieces covering the fore and aft parts of the hull; to steer a canoe)
  • mo'o (gunwale)
  • muku (ends of 'iako that extend beyond the hull)
  • wae (spreaders)
  • wa'a (canoe, also va'a, waka)

How many lines can you put on an outrigger? ›

Each outrigger can accommodate one or two lines from your rods and reels. The line is used with a release clip that extends to the end of your outrigger. When a fish strikes your bait, the release clip will allow your fishing line to come free of the outrigger so you can reel in the fish.

What are the 4 types of structural systems? ›

There are five basic structure or framing types and an assortment of alternative structural systems: (1) wall-bearing, (2) reinforced concrete, (3) structural steel, (4) a combination of these types, and (5) tensile structures.

What are the 4 main types of structures? ›

There are four types of structures;
  • Frame: made of separate members (usually thin pieces) put together.
  • Shell: encloses or contains its contents.
  • Solid (mass): made almost entirely of matter.
  • liquid (fluid): braking fluid making the brakes.

What are the 4 types of building system? ›

be divided into four categories as follows: foundation systems, floor systems, wall – column systems, and roof systems. systems such as partition walls, insulation, doors, cladding, electrical & HVAC systems.

What line do you use for outriggers? ›

Generally, there are two materials used as halyard lines when rigging outriggers: Braided nylon rope and monofilament. There are advantages to both, and it becomes a personal preference as opposed to “what is better.”

How do you calculate outrigger pressure? ›

Maximum outrigger down pressure* ÷ outrigger pad/fl oat square inches = amount of pressure per square inch on the blocking material.

What is maximum outrigger load? ›

As a guide the QLD Crane Code of Practice states that the maximum outrigger force is the crane weight (including rigging gear weight) plus load weight, multiplied by 0.65. Calculate the Force.

How long should your outriggers be? ›

The length of the rigger pole to use depends largely on the size of the boat and number of halyards you plan to fish. Typically, boats from 26 to 30 feet use riggers from 18 to 30 feet in length. Outrigger clips come in two basic styles: roller (left) and wire-bail (right).

Should you grease outriggers? ›

Although there aren't a ton of moving parts associated with outriggers, make sure that parts that rotate and move are kept well lubricated with a high-quality marine lubricant. Everything should move smoothly without sticking or squeaking.

What is outrigger framing? ›

Right - Lookout or outrigger framing for a gable overhang provides two points at each outrigger to add metal connectors to strengthen the overhang against wind uplift.

Where should outriggers be placed? ›

If you've decided you need outriggers, you probably have all kinds of questions, one of them being, “How long should a kayak outrigger be?” Generally outriggers are between 30 to 36 inches long. They're usually placed about three-quarters of the way toward the stern, just behind the seat.

Should outriggers be used without pads? ›

Because of the pressure of the outrigger, the ground underneath may shift, be displaced or collapse if an outrigger pad is not used. If any of those things happen, there is the potential for the equipment to shift or tip the load, which could lead to the equipment toppling over.

At what angle must outrigger beams be placed relative to their bearing support? ›

In addition, paragraph (d)(3)(viii) requires that outrigger beams be placed perpendicular to their bearing support, with the exception described more fully below.

What is used to prevent accidental displacement of outrigger beams? ›

(iv) Counterweights shall be secured by mechanical means to the outrigger beams to prevent accidental displacement. (v) Counterweights shall not be removed from an outrigger beam until the scaffold is disassembled.

What is outrigger scaffold? ›

outrigger scaffold means a supported scaffold that consists of a platform resting on outrigger beams (thrustouts) projecting beyond the wall or face of the building or structure, with inboard ends secured inside the building or structure; Sample 1Sample 2.

Why is outrigger only on one side? ›

Outrigger to the left for the respect of the traditions.

What does a basic outrigger rigging kit consist of? ›

Snubbers, release clips, pulleys, outrigger line, and hardware to secure the pulleys to the gunnels are included in the six complete rigging kits.

What is the most common injury in outrigger? ›

Outrigger canoe paddlers report a high prevalence of musculoskeletal injuries and illnesses related to their sport. The shoulder and back were the most common sites of injury.

What is the standard size of outrigger pad? ›

Crane Outrigger Pad Size Chart
Set of 4 PadsLength (m)Width (m)
PAD-0392.371.63
PAD-0502.472.03
PAD-0612.982.04
PAD-0823.402.40
5 more rows

What is a V1 outrigger? ›

What is a V1? V1 stands for one-person va'a. The Tahitian term va'a is used to differentiate it from an OC-1 (one-person outrigger canoe). V1s are traditionally defined by an open cockpit and no rudder.

Can you stack outrigger pads? ›

Never stack a larger outrigger pad on top of smaller outrigger pads, cribbing, dunnage or other supporting materials. Always use materials of a known strength that are designed as support for heavy equipment.

What are the 7 structural devices? ›

Terms in this set (7)
  • Post and Lintel. most ancient of construction device. ...
  • Cantilever. a horizontal extension of a beam or a slab into space beyond its supporting post.
  • Truss System. ...
  • Arch. ...
  • Dome. ...
  • Shell Structures. ...
  • Solar Panels.

What are the 5 structural components? ›

Structural Elements means the roof, exterior structural walls, structural columns, structural support beams and the foundation of the Building and the Garage.

What are the 6 basic structural elements? ›

The following six elements are essential to the success of of all structures:
  • Stability. Every successful structure must be conceived in a stable configuration that includes sufficient bracing. ...
  • Strength. ...
  • Stiffness. ...
  • Serviceability. ...
  • $ustainability. ...
  • Schedule. ...
  • Satisfaction.

What are the 6 types of structures? ›

In this article, we describe six main types of building structures, the materials contractors use for each and jobs that involve these structures.
...
Main types of building structures
  • Wood frame. ...
  • Light gauge steel. ...
  • Load-bearing or joisted masonry. ...
  • Steel frame. ...
  • Concrete frame. ...
  • Pre-engineered construction.
Jun 1, 2021

What are 5 examples of structures? ›

Buildings, aircraft, skeletons, anthills, beaver dams, bridges and salt domes are all examples of load-bearing structures. The results of construction are divided into buildings and non-building structures, and make up the infrastructure of a human society.

What are the 3 main types of structures? ›

There are three basic types of structures: shell structures, frame structures and solid structures.

What are the 5 stages of building construction? ›

The five phases of the construction project lifecycle are:
  • Project Initiation and Conception. Like with all things, the first step to the construction life cycle is merely to begin. ...
  • Project Planning and Definition. ...
  • Project Execution and Launch. ...
  • Project Performance. ...
  • Project Close.

What are the 3 types of non structural systems? ›

ATC-69 (2008), FEMA-356 (2000) has grouped non-structural elements into three categories: architectural, mechanical and electrical, and other contents ( Table 1). Recent earthquakes in US shows the major cost of damage in buildings are due to the vulnerability of non-structural systems ( Filiatrault et al. 2011). ...

What is outrigger load? ›

The outrigger load is specific to the amount of force applied to any one of the outriggers during set-up, operations and tear down of the equipment. To ensure safety, DICA believes the rated capacity of the pads should always exceed the maximum outrigger reaction force of the equipment.

What is an outrigger Jack? ›

Outrigger Jack: The hydraulic cylinder on the outrigger beam which extends vertically to raise and lower the crane. ( Source: A Glossary of Common Crane and Rigging Terms.

How do outrigger pads work? ›

An outrigger pad is a sturdy, heavy duty mat or pad that helps distribute the weight of heavy machinery more evenly across a surface by creating a larger surface area for the machine's outriggers/stablizers to rest upon.

What is an outrigger in architecture? ›

Outriggers are typically horizontal structures (usually trusses or reinforced concrete walls) inserted into buildings at various levels to tie the concrete core to the outer (or perimeter) structural framework.

What are the benefits of outriggers? ›

Benefits of outriggers
  • Reduce overturning moments and building drift.
  • By decreasing building overturning moment, provide more economic use of materials required to construct the core.
  • Reduce forces in the core's foundations to provide further economy.
Jan 18, 2021

What is the purpose of crane outriggers? ›

Outriggers keep your truck stable during any kind of lift by extending outward and making contact with the ground several feet away from the truck. This provides a solid, stable base by distributing the crane's load over a larger area.

Are outriggers necessary? ›

Please note that outriggers are required at each end of a continuous roof guardrail system, as well as at each end of any interruption of a continuous guardrail system. It's also essential to position the outrigger base plate so that the long direction of the base plate is parallel to the outrigger railing.

How big should my outriggers be? ›

Outrigger poles range in length from 15' to more than 35'. For outboard-powered fishing boats up to 45 feet or so, 15' to 25' poles are most common. Poles longer than about 25' require spreaders for support and added stiffness and are typically found on sportfishers.

Do outriggers need to be at full extension when crane is in use? ›

Manufacturers do not recommend extending only one or two of the outriggers. If outriggers are to be used, fully extend all of them and get the tires off the ground. Accidents commonly occur because the operator is lifting from only one side of the rig, with only two outriggers extended.

What type of hazard does using outriggers prevent? ›

Outrigger pads were created to stabilize equipment so that the ground below doesn't shift and equipment doesn't topple over.

How far can a purlin overhang? ›

c states, “Rake overhangs shall not exceed the lesser of one-half the purlin length or 2 feet” and makes an exception for “Rake overhangs using lookout blocks[, which] shall not exceed 1 foot.”

How is outrigger load calculated? ›

Maximum outrigger down pressure* ÷ outrigger pad/fl oat square inches = amount of pressure per square inch on the blocking material.

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