Assessment of the seismic performance of a RC building designed following two alternative approaches: NCh433+DS61 versus ACHISINA PBEE requirements.

Abstract

Chile is one of the world's most seismically active countries, with two earthquakes on the list of the ten largest earthquakes ever recorded (Mw 9.5 Valdivia, 1960; Mw 8.8 Maule, 2010). The seismic design of buildings in Chile follows the NCh433 standard, based on a traditional approach that uses reduced earthquake forces applied over linear elastic models. Following the 2010 Chile earthquake, two supreme decrees were published (DS60 and DS61), which modified some NCh433 requirements concerning the design of reinforced concrete (RC) buildings. In 2017, the Chilean Association of Seismology and Earthquake Engineering (ACHISINA) introduced an alternative performance-based (PBEE) procedure to design RC buildings. This document is based on the proposals of the Los Angeles Tall Building Structural Design Council (LATBSDC). The ACHISINA document clearly defined several earthquake levels, performance objectives, and limit states to understand better the behavior of buildings subjected to these ground motions, opening a window to obtain alternative designs which hopefully can reduce involved costs. In this study, a 20-story tall RC shear wall building, considered a typical Chilean residential building, was designed following the NCh433+DS61 requirements. Later, nonlinear analyses were conducted to verify if this building satisfied the requirements of the ACHISINA PBEE document and explore if it is possible to reduce the project costs by introducing design changes. Three different modeling techniques for the whole building were evaluated. Analyses showed that the building did not satisfy the story drift limits established in the ACHISINA PBEE document; therefore, design changes are impossible. Later, this thesis compares the requirements of the ACHISINA PBEE document and the LATBSDC PBEE document, discussing the changes introduced in the Chilean document and the impact on actual designs.