Seismic Isolation of the Nunoa Capital Building, the Tallest Base Isolated Building in the Americas


Abstract eng:
This paper describes the selection process for a seismic protection system for the Nunoa Capital Building towers, the tallest isolated residential building in the Americas. A comparison of the seismic performance of these 33-story (42,600 m2) towers when protected with viscous walls and a lead rubber bearing base isolation system is presented. The challenges for the designing engineering team and the main design criteria that resulted in the use of 24 large diameter seismic isolators are presented. It is shown that the use of base isolation in this building caused the base overturning moment to increase in comparison to an equal base shear building designed without isolation. Moreover, the requirement of the Chilean isolation code that requires considering a minimum design base shear equal to 5% of the seismic weight, led in this case to design forces almost two times greater than the elastic seismic demand. This code requirement imposed the structural design team two enormous additional challenges: to limit the superstructure interstory drift below 0.25% (code requirement), and to avoid tension and excessive compression forces in the isolation devices, for the design and maximum considered earthquakes, respectively. The interstory drift limit was achieved by using an outrigger system in a non-optimal location due to architectural constraints. Tension forces on the isolators were avoided by interconnecting the slabs of the two towers at the underground levels and by the use of a stiff slab above the isolators. The magnitude of vertical loads on the isolators (up to 40,000 kN) and the need for a long period (nearly 5 seconds) presented some challenges for the design and testing of the isolators. Three types of isolators, with diameters of 115 cm, 135 cm and 155 cm, were used to provide the desired isolated period and damping (20%), while maintaining a vertical frequency in excess of 10 Hz. Isolators were extensively tested at DIS test facility in McCarran, Nevada, USA and at the EU center in Pavia, Italy. Test results validated the properties used in the design and demonstrated the stability of isolators under extreme conditions.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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 Record created 2017-01-18, last modified 2017-01-18


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