Seismic Risk Assessment Earthquake Resistant Construction

Abstract

At present, earthquake-resistant design of buildings is based on force-based analysis and on representing the effect of an earthquake by static equivalent forces, which are calculated using elastic response spectra that relate the law of ground motion to the absolute acceleration of a model in the form of a nonlinear oscillator.

Such an approach does not directly take into account either the influence of the duration of strong motions or the plastic behavior of the structure. The frequency content and duration of ground vibrations directly affect the energy entering the structure and causing damage to its elements. Unlike force-based or kinematic analysis, the seismic action on a structure can be interpreted without considering forces or displacements separately; it may be represented as the product of both quantities, that is, as work or input energy (the maximum energy that a structure can acquire as a result of an earthquake). In an energy-based approach to seismic design, it is necessary to estimate the seismic input energy entering the structure and its distribution among the various structural components.

The article provides a justification for the energy-based approach in the design of earthquake-resistant buildings and structures as an alternative to the currently used method, which is based on force analysis and on the representation of earthquake effects by static equivalent forces calculated using response spectra. It is noted that interest in the use of energy concepts in earthquake-resistant design began with the works of Housner, who represented seismic forces in the form of seismic input energy using the velocity spectrum and proposed that damage in an elastoplastic system, as in an elastic system, is caused by the same seismic input energy. The paper presents indices for determining the input energy of an earthquake. It is shown that modern approaches to ensuring the seismic resistance of structures, based on representing the earthquake effect as a static equivalent force, do not describe the behavior of the system during an earthquake adequately enough.

The article proposes a new approach to seismic risk assessment that makes it possible to formalize the decision-making process concerning anti-seismic measures. The developed document represents a step forward with respect to the optimal design of earthquake-resistant structures.