illustrates a very important point: In general, the earthquake resistance of any building is highly dependent upon the connections joining the building's larger structural members, such as walls, beams, columns and floor-slabs. Shear walls, in particular, must be strong in themselves and also strongly connected to each other and to the horizontal diaphragms. In a simple building with shear walls at each end, ground motion enters the building and creates inertial forces that move the floor diaphragms. The shear walls resist this movement and the forces are transmitted back down to the foundation. Braced Frames Braced frames act in the same manner as shear walls, but they may offer lower resistance depending on their details of their design and construction. Bracing generally takes the form of steel rolled sections, circular bar sections, or tubes. Vibration may cause the bracing to elongate or compress, in which case it will lose its effectiveness and permit large deformations or collapse of the vertical structure. Ducti1ity therefore must be designed into the bracing to create a safe assembly. Moment Resistant Frames Figure 3: Beam-Column Joint, MR Frame When moment resistant frames provide seismic resistance, lateral forces are resisted primarily by the joints between columns and beams. These joints become highly stressed and the details of their construction are very important. Moment frames use, as a last-resort resistance strategy, the energy absorption obtained by permanent deformation of the structure prior to ultimate failure. For this reason, moment resistant frames generally are steel structures with bolts or welded joints in which the natural ductility of the material is of advantage. However, properly reinforced concrete frames that contain a large amount of steel reinforcing are also effective as ductile frames. They will distort and retain resistance capacity prior to failure and will not fail in a brittle manner. Archite...
