Charactericrics of the seismic movement of the day surface. Their use in earthquake engineering

Abstract

Relevance. The paper analyzes requirements for the design seismic input. First of all, it is ensuring the structure safety margin when considering its limiting states. From this point of view, the concept of similarity between real and design actions is rather indefinite. At least, no external similarity between the real and the design actions is required. At the same time, the design action should have a number of characteristics close to real ones. Aim. The paper analyzes three groups of such characteristics: kinematic, energy and spectral ones. Out of the kinematic characteristics, the peak accelerations and the harmonic coefficient are analyzed in detail. The relationship of these characteristics with the input predominant period on the accelerogram has been established. A new modification of the harmonic coefficient is proposed, taking into account the residual displacements after the earthquake. Methods. To assess peak accelerations, the authors proposed a method based on a scale of earthquake intensity, which does not require the use of other regulatory documents and seismic zoning maps. Results. It is noted that the kinematic characteristics are the main ones for carrying out force calculations of structures under the action of a design earthquake. The Arias intensity, absolute cumulative velocity, seismic energy density, root-mean-square acceleration and Park-Young indicator are considered as energy characteristics. It is shown that the energy characteristics in the frame of the same seismic intensity are constant and do not depend on the action spectral composition. Confidence limits for the Arias intensity and absolute cumulative velocity estimates were obtained. It is noted that the energy characteristics are important for calculations of structures out of elasticity area under maximum design earthquake. When considering the spectra, besides the response spectra, the spectrum of the work of plastic deformation forces and the spectrum of structure damageability are considered. The former spectrum is important for calculating elastoplastic systems, and the latter one is important for calculating adaptive systems. When modeling the action spectral composition, it is necessary to use resonant design input for the calculated structure. A contravention of this requirement must have a strong rationale for seismologists, who must bear financial and legal responsibility for this solution.