A violent earthquake of magnitude 7.8 on the Richter scale hit last April Ecuador’s coast, only 19km deep. The epicenter was located in the natural reserve of Mache-Chindul, a few kilometers from the coastal towns of Monpiche and Bolivar and about 170 km from the capital Quito.
The earthquake was felt throughout the country and also in Brazil, Peru, Colombia and Panama. But the most intense shaking was registered in the epicenter area where it produced catastrophic results: according to the official tally the number of victims should be equal to 570.
Seismicity indicates the frequency and the force with which the earthquake occurs, and it is a physical characteristic of the territory. The consequences of an earthquake also depend on the resistance features of the buildings to the actions of a seismic shock. The predisposition of a building to be damaged is defined vulnerability. The more a building is vulnerable (by type, inadequate design, poor quality of materials and methods of construction, poor maintenance, type of soil on which the building is located), the greater will be the consequences.
To reduce the effects of the earthquake and the loss of lives it is necessary to build safe buildings and make the existing ones less vulnerable. Today the rules or construction in seismic zones require that the buildings are not damaged by low-intensity earthquakes, are not subjected to structural damages by medium intensity earthquakes and do not collapse during strong earthquakes, although they can suffer serious damages.
The type of recorded damage may depend on a number of circumstances including: structural system of the building, age, characteristics of the materials, seismicity of the area, proximity to other buildings as well as other non-structural elements. When an earthquake occurs, the ground moves horizontally and/or vertically, by subjecting the buildings above to cycles of inertial forces. The buildings begin to swing according to frequencies which depend on the type of construction. If the structure is ductile and therefore capable of undergoing deformation, it will have a greater chance not to collapse even if it can suffer serious damages which, as mentioned, depend on the duration and the magnitude of the earthquake.
With the Emmedue Building System the role of transferring the seismic actions is played by the shear walls.
The greatest advantage of the insertion of walls is the significant increase of lateral stiffness of the building, which allows:
Furthermore, the greater stiffness of the structural system:
• minimizes the negative influence that the infill walls panels can have on the global behavior of the building;
• protects the secondary elements from damage, which implies a considerable economic advantage in terms of repair costs;
• minimizes the psychological effects on people
A further advantage is that the behavior of buildings with walls is usually more reliable than the buildings made of only frames; this thanks to the fact that the pinned supports are formed in the beams and not in the walls, in particular if these have been designed according to the capacity design rules.
The walls designed according to modern rules present a remarkably ductile behavior towards monotonous loads. The flexural strength is not much affected by the amount of reinforcement; whereas a higher density of reinforcement entails a greater ductility.