Outrigger And Belt Truss Systems

The structural arrangement for an outrigger system consists of a main core connected to the exterior columns by relatively stiff horizontal members commonly referred to as outriggers. The main core may consist of a steel braced frame or reinforced concrete shear walls, and may be centrally located with outriggers extending on both sides (Fig. 3.17a). Alternatively, it may be located on one side of the building with outriggers extending to the building columns on one side (Fig. 3.17b).

The basic structural response of the system is quite simple. When subjected to lateral loads, the column-restrained outriggers resist the rotation of the core, causing the lateral deflections and moments in the core to be smaller than if the freestanding core alone

Figure 3.17. (a) Outrigger system with a central core: (b) outrigger system with offset core; (c) diagonals acting as outriggers; (d) floor girders acting as outriggers.

resisted the loading. The external moment is now resisted not by bending of the core alone, but also by the axial tension and compression of the exterior columns connected to the outriggers. As a result, the effective depth of the structure is increased when it flexes as a vertical cantilever, by the development of tension in the windward columns, and by compression in the leeward columns.

In addition to those columns located at the ends of the outriggers, it is usual to also mobilize other peripheral columns to assist in restraining the outriggers. This is achieved by including a deep spandrel girder, or a truss commonly referred to as a "belt truss," around the structure at the levels of the outriggers.

To make the outriggers and belt truss adequately stiff in flexure and shear, they are made at least one—and often two—stories deep. It is also possible to use diagonals extending through several floors to act as outriggers, as shown in Fig. 3.17c. Yet another option is to moment-connect the girders at each floor to the core (Fig. 3.17d). It should be noted that whereas the outrigger system is effective in increasing the structure's flexural stiffness, it does not increase its resistance to shear, which must be carried mainly by the core.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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