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This paper provides new and useful insights into the performance and efficiency of geotechnical seismic isolation (GSI) systems with gravel-rubber mixtures containing 10%, 25% and 40% volumetric rubber content (VRC). Finite element numerical models were developed in OpenSees and subjected to sinusoidal ground motions with varying input base acceleration and frequency. The best seismic performance was attained for VRC = 40% at a frequency of 8 Hz. Using a newly developed GSI efficiency index, the energy dissipation efficiency of VRC = 40% was found to vary between good to excellent, while that of VRC = 10% and 25% is poor. [ABSTRACT FROM AUTHOR]

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. Practical Applications: 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. [ABSTRACT FROM AUTHOR]

The absolute maximum response (AMR) of structures might occur posterior to the end of earthquake excitations, hence, extending the dynamic analysis to the post-shaking phase is required. This phenomenon was found to be more common for long-period and low-damping structures, which are prevailing in regions of low-to-moderate seismicity like Australia. In this article, the mechanism of the occurrence of AMR in the post-shaking phase is first explained using single-degree-of-freedom (SDOF) systems subjected to a simple sine wave. Further investigation on real earthquake ground motions reveals that whether an extended analysis is required depends greatly on the characteristics of the post-significant duration phase. Finally, suitable metrics for describing ground motions that require extended analysis (EAGMs) are identified based on the Kolmogorov–Smirnov test. Regression analyses are then conducted to predict the probability of EAGMs. [ABSTRACT FROM AUTHOR]

Base isolation is a low-damage seismic design strategy that can be used for constructing resilient structures. Geotechnical seismic isolation (GSI) is a new category of emerging base isolation techniques that has attracted global interest in the past decade. Research on GSI based on rubber-soil mixtures (RSM) has focused on structural performance under earthquake actions, whilst there are concerns over the serviceability limit states (SLS) requirements in relation to (i) human comfort under strong winds and (ii) ground settlement under gravity, which may induce cracking and durability issues in structures. This article presents the first study on the serviceability performance of buildings constructed with the GSI-RSM system. The finite element model of a coupled soil-foundation-structure system has been validated by data recorded from geotechnical centrifuge testing. The numerical estimates of ground settlement have also been compared with analytical predictions. It is concluded that the GSI-RSM system can satisfactorily fulfill the SLS requirements. [ABSTRACT FROM AUTHOR]

This paper is aimed at serving the needs of structural engineering designers of an important structure (or a group of structures located on the same site) who is seeking guidance on how to obtain accelerograms and/or derive response spectra that accurately represent the site subsoil conditions as informed by the borelogs. The presented site-specific seismic action model may be used to replace the default seismic action model stipulated for the designated site class. Presented in this article is a procedure for generating soil surface motions in an earthquake, and their associated site-specific response spectra, taking into account details of the soil layers. Dynamic site response analyses are involved. The conditional mean spectrum methodology is employed for selecting and scaling accelerograms for obtaining input motion on bedrock. The selection depends on the natural period of both the site and the structure. Multiple borelogs taken from within the same site are analysed to identify the critical soil column models without having to conduct site response analysis on every borelog. The technique for simplifying the soil layers utilising the shear strain profile is introduced to further cut down on the time of analyses. The procedures described in this article have been written into a web-based program that is freely accessible to engineering practitioners. [ABSTRACT FROM AUTHOR]

Geotechnical Seismic Isolation (GSI) can be defined as a new category of seismic isolation techniques that involve the dynamic interaction between the structural system and geo-materials. Whilst the mechanism of various GSI systems and their performance have already been demonstrated through different research methods, there is a missing link between fundamental research and engineering practice. This paper aims to initiate the development in this direction. A new suite of equivalent-linear foundation stiffness and damping models under the same framework is proposed for four GSI configurations, one of which is a novel combination of two existing ones. The exact solutions for the equivalent dynamic properties of flexible-base systems have also been derived that explicitly include the foundation inertia and the strain-dependent equivalent damping of foundation materials, which are both significant for GSI systems. The application of the proposed analytical design models has been illustrated through response history analyses and a detailed hand-calculation design procedure has also been outlined and demonstrated. [ABSTRACT FROM AUTHOR]