How vulnerable are masonry buildings to earthquakes? How can they be designed to resist earthquakes? HOW MASONRY BUILDINGS RESPOND Because masonry buildings usually have many structural wall elements, they tend to be stiff laterally. Because masonry buildings are stiff laterally, even moderate earthquakes can subject them to large shear loads at their base. For a typical masonry building, these shear loads can be calculated in the following way: Base shear load= (building mass) x (earthquake ground acceleration) x (dynamic amplification factor). MASONRY SEISMIC DESIGN Though even moderate ground accelerations can subject masonry buildings to large shear loads, masonry buildings can still be designed to resist these loads. In general, the designer must estimate the lateral inertial forces acting on each element and provide for the transfer of these forces down to the foundation. INELASTIC RESPONSE OF MASONRY BUILDINGS A masonry building's earthquake resistance has been described here as a function of wall layout, wall area, and wall strength. These characteristics are often sufficient. Enough wall area can often be provided so that even during a strong earthquake the building's walls remain basically elastic, without any yielding of reinforcement. However, architectural constraints may limit the wall area that can be provided. In that case, the building's walls will respond inelastically in a strong earthquake. To provide the necessary safety, a building's walls should be laid out so that seismic shear forces can be transmitted down to the foundation even if individual walls fail. Structural connections should be designed to resist the forces associated with this inelastic response. Broadly stated, these additional requirements must give the masonry building ductility- the ability to withstand inelastic deformations without much decrease in capacity.