Principles of Disaster Mitigation in Health Facilities - DISASTER info ...

Chapter 2 — Structural Vulnerability
Figure 2.8.
Eccentricity between centers of mass and stiffness increase effects of torsion.
Seismic-resistant design
Seismic-resistant design of structures is more complex than the design for static gravity loads, due
to some of the following factors:
a) The random nature of the characteristics of an earthquake;
b) The uncertainty of the response of the structure, due to the heterogeneous quality of materials,
interactions with nonstructural elements, variation in service loads, variations in construction,
etc.;
c) The failure and energy dissipation mechanisms that entail the least risk for human life and
p r o p e r t y;
d) The social cost entailed in the failure of buildings, especially those essential for responding to
disasters, as in the case of hospitals.
Seismic-resistant design should attempt to take into account all of these aspects. 6 Normally, design
codes address some of these problems by means of simple quantitative formulas for overall or localized
safety considerations. Often, mindless adherence to these quantitative formulas in the design of structures
causes the basic principles behind such simplifications to be forgotten or disregarded. However, in the
design of any building, and especially essential facilities such as hospitals, the implications of each
important decision must be assessed in the light of the principles and advances of seismic engineering.
Below is a summary of these implications of seismic design of hospitals.
6 Asociación Colombiana de Ingeniería Sísmica, Normas colombianas de diseño y construcción sismo resistente NSR-98
(Law 400 of 1997, Decree Law 33 of 1998), Bogotá, 1998.
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