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Active control system: ground motion sensor, processor, and controlled mass

FIGURE 19.3 (a)-(c) Traditional earthquake force resisting systems. (d)-(f) Emerging technologies for earthquake force reducing systems.

are also capable of resisting lateral loads. In this type of construction, the connections between the beams and the columns are designed to resist the rotation of the column relative to the beam. Thus, the beam and the column work together and resist lateral movement by bending. This is contrary to the braced frame, where loads are resisted through tension and compression forces in the braces. Steel buildings are sometimes constructed with moment resistant frames in one direction and braced frames in the other, or with integral concrete or masonry shear walls.

In concrete and masonry structures, moment-resisting frames (MRFs) or shear walls1 are used to provide lateral resistance. Ideally, these shear walls are continuous walls extending from the foundation to the roof of the building and can be exterior or interior walls. They are interconnected with the rest of the concrete frame and thus resist the motion of one floor relative to another. Shear walls can be constructed of cast-in-place reinforced concrete, precast concrete, reinforced brick, or reinforced hollow concrete block. Steel shear walls have been employed, but are not common.

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