Seismic Performance of Fully Modular High-Rise Buildings with Superelastic Tendon Restrained Rocking

Abstract

Designing a fully modular building, which is without the support of any separate lateral resisting elements, has the advantage of rapid site assembly, but runs the risk of a brittle style of connection failures in a rare earthquake event. Thus, this form of construction is currently limited to low-rise buildings. Isolating the building from its base and allowing the rocking motion to occur has been proven to be effective in dissipating energy and prolonging the natural periods by the lifting of the structure, thereby alleviating high strength demand on the building itself. To avert overturning, the amount of the rotation of the building needs to be controlled, and the use of superelastic tendons as a restraint is a promising solution. Previous studies into the seismic performance with this novel form of construction have been limited to experimenting with a rigid block or a single lumped mass system. In this study, this approach of seismic isolation is extended to a high-rise modular building with distributed mass and stiffness. A scaled-down model of a 19-story fully modular building, which was partially restrained by superelastic tendons, was tested on a shaking table. The key objective was to study the deflection profile and distribution of internal forces up the height of the superelastic tendon–restrained building and examine the contributions by the higher modes. The internal forces predicted by the analytical model developed in the study are shown to be in good agreement with experimental measurements. Modular construction shortens construction time and reduces environmental impacts. Currently, fully modular buildings, which have a high degree of prefabrication, are limited to low-rise constructions because of concerns over the overturning risk in major earthquake events. A new seismic safe design employing a superelastic tendon is introduced in this article to extend fully modular construction to high-rise buildings. The building is designed to rotate about its base when subjected to high intensity ground shaking. The amount of rotation is controlled by the superelastic tendon in order to avoid overturning from occurring. Meanwhile, internal forces taken up by the structural elements within the building were kept much lower than a conventional fixed base building. The dynamic testing of the miniature model of a 19-story building on the shaking table was featured in the study, which laid down principles that are essential for the formulation of effective guidelines for the structural design of this type of building.