Implication of the Act 117 in the seismic demand and global response in buildings of Antofagasta

Abstract

In this paper the results of the study about the effect of the changes in the seismic code included in the Act 117 approved by the Ministry of Housing and Urbanism in February 2011 are summarised. The discussion is focused on the demand and response of high-rise buildings (ten or more floors) located in Antofagasta. First, a geotechnical description of the soil conditions and information of buildings are presented. Even though the three main soil types described in the Act can be found as foundation soils in the city, and each one has a defined design spectrum, most of the high-rise buildings are founded on rock. From the registered information, nine tall buildings were selected for modal spectral analysis under both the NCh433 Of. 96 Mod. 2009 and the Act 117. Results obtained using both regulations are compared in terms ofshearforce and overturning moment at the base level and shear force at differentfloor levels. Finally, on one hand it is concluded that the seismic response of buildings founded on rock (type I) is very similar considering both regulations. On the other hand, for soil type II, significant differences were found in the overturning moments and upper displacements and maximum relative displacement between floors.