Inertial interaction effects analysis on the estimating of dynamic amplification factor for reinforced concrete structures

Abstract

This work shows the importance of the need for revision of the Algerian seismic regulations RPA 2003 in terms of the dynamic amplification factor for R/C Rigid buildings with period 0.3 < T < 0.35 in stiff site. In most national building codes, formulas for estimating the seismic base shear include many factors such as the dynamic amplification factor D presented in the Algerian and Moroccan seismic codes RPA2003 and RPS2000 respectively, the response coefficient of the building B for the Iranian code ICS1999, and the spectral acceleration amplification factor B0 for the Eurocode 8. To determine this factor, it is necessary to estimate the value of the vibration period of building based on empirical formulas that do not consider the inertial effects. Diagrams representing the variations of this factor show that the latter remains constant over a range from 0 to 0.7 s for the Algerian code corresponding to structures with 1 to 7 levels; 0 to 1 s for the Moroccan, Iranian and Eurocode 8 corresponding to structures with 1 to 10 levels. No difference was noted in the dynamic factor as a result of degradation of the soil bearing capacity in this ranges. The purpose of this paper revolves around two main themes: the effects of Soil Foundation Structures Interaction (SFSI) on the estimation of dynamic amplification factor on the equivalent static analysis, and the elaboration of a new factor DSAF* called “dynamic site amplification factor” which takes into consideration the SFSI effects, the classifications of the seismic zones and the importance of the structures with application of the Algerian seismic code RPA2003. These values are presented in their simple and easy way to the different users. The results show the importance of these safety coefficients, recommended in the seismic regulations under the effect of SFSI, when the RPA2003 placed in the non-conservative side for the structures belongs to the ranges 0 to 0.7 s.