Seismic isolation and energy dissipation systems

It has already been noted in Chapter 4 that seismic-resistant R/C frames as well as R/C walls and dual systems constitute the three basic seismic-resistant systems in use for earthquakeresistant buildings. Frame systems are usually 3-D structures consisting of plane frames arranged in two orthogonal directions, usually in the form of pseudo 3-D structure. It is obvious that each of these frames is affected biaxially, at least at its columns, due to the simultaneous seismic actions in both main directions. However, for a better understanding, the plane frame will be examined first and then reference will be made to biaxial loading.