Abstract
The sufficient estimation of the natural period of vibration constitutes an essential step in earthquake design and assessment and its role in the development of seismic damage is investigated in the current research. The fundamental period is estimated for typical reinforced concrete building types, representative of the building stock of Southern Europe, according to existing relationships. The building typologies also represent groups of 180,945 existing damaged buildings of an observational database created after the Athens (7-9-1999) near field earthquake. The estimated fundamental periods are correlated to several degrees of the recorded damage. Important conclusions are drawn on the parameters (height, structural type, etc.) that influence the seismic response and the development of damage based on the wide database. After conducting a correlation analysis, noticeable is the difference between the seismic demand of the elastic spectrum of the first (1959), the contemporary (2003) Greek Seismic Code and the values of peak ground accelerations of several Athens earthquake records. Moreover, PGAs in most records are often between the lower and the upper bound of the estimated fundamental periods for RC buildings with regular infills (n-normal) and with ground levels without infill panels (p-pilotis) regardless the height. A disparity is noticed when the estimated fundamental period is based on EC8 provisions for the considered as “high” buildings in S. Europe regarding the referring earthquake. The majority of buildings that developed several degree, type and extent of damage are considered of “low” height with estimated fundamental periods close to the PGA values of Athens earthquake ground motions. However, the developed damage was the result of the combination of parameters based on geological, tectonic and morphological characteristics of the affected area. In addition, a damage scale for the measurable recording, beyond the qualitative characterization of seismic damage in Greek post-earthquake surveys, is presented wherein the performance levels are defined according to the physical description of the seismic damage and, as well, in terms of structural and economic damage index.
Highlights
The reliable evaluation of a basic dynamic characteristic as the fundamental period is an essential step in estimating the seismic response both in seismic design and assessment
Important conclusions are drawn on the parameters that influence the seismic response and the development of damage based on the wide database
A damage scale for the measurable recording, beyond the qualitative characterization of seismic damage in Greek post-earthquake surveys, is presented wherein the performance levels are defined according to the physical description of the seismic damage and, as well, in terms of structural and economic damage index
Summary
The reliable evaluation of a basic dynamic characteristic as the fundamental period is an essential step in estimating the seismic response both in seismic design and assessment. The period of vibration is dependent mostly on mass, stiffness and strength and on all the factors which affect the pre-mentioned characteristics such as building material and type, dimensions (in height and plan), morphology and irregularities, section properties, stiffness, cracking, etc. Many simple relationships have been proposed in an effort to determine the fundamental period of structures These empirical formulas have been produced by fitting curves through regression analysis on the buildings periods of vibration measured from their seismic movements during several earthquakes. The typical building typologies are representative of the materials, the seismic codes and the construction techniques of Southern Europe They represent groups of existing damaged buildings in several degree, type and extent of a dataset derived from post-earthquake surveys which took place in an extended region of Attica in Greece. A correlation is fulfilled between the estimated fundamental periods of RC buildings with the different damage states of the proposed scale, FEMA performance levels and the analysis results of the database
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