Seismic Isolation and Response Control

<p>The seismic resilience of new and existing structures is a key priority for the protection of human lives and the reduction of economic losses in earthquake prone areas. The modern seismic codes have focused on the upgrade of the structural performance of the new and existing structures. However, in many cases it is preferrable to mitigate the effects of the earthquakes by reducing the induced loads in the structures using seismic isolation and response control devices. The limited expertise in the selection and design of the appropriate system for new and existing structures is the main challenge for an extensive use of seismic isolation and response control systems in practice.</p> <p>This document aims to provide a practical guide by presenting a collection of the most commonly used seismic isolation and response control systems and a critical evaluation of the main characteristics of these systems. Comparisons of the key parameters of the design processes for new buildings with seismic isolation are presented, while the application of seismic isolation systems and response control systems for the retrofitting of existing structures is also examined, followed by various case studies from Greece, Japan, Mexico, New Zealand, and Turkey.</p>

Seismic loss assessment of seismically isolated buildings designed by the procedures of ASCE/SEI 7-16

This paper investigates the seismic loss assessment of seismically isolated and non-isolated buildings with steel moment or braced frames, designed by the seismic design standard of ASCE/SEI 7-16. The seismic loss is calculated from the damage to structural and non-structural components, as well as the demolition and the collapse of buildings. This study demonstrates that the expected annual losses for seismically isolated buildings are half or less than half of those calculated for non-isolated buildings. These losses depend on the types of seismic isolation systems and seismic force resisting systems used. Among the cases of isolated buildings studied in this paper, the most cost-effective systems are found to be the buildings designed by minimum strength requirement in ASCE/SEI 7-16 and with isolators which have displacement capacity 1.5 times larger than the minimum required in ASCE/SEI 7-16, in terms of expected annual losses. This study also compares the results obtained from different approaches of selection and scaling of ground motions. The following research finds that when Incremental Dynamic Analysis approach with far-field ground motion set in FEMA P695 is used, the computed expected total annual losses become doubled from the Conditional Spectra approach.

Consideration of Three Seismic Isolation Performances as Design Objectives for Equivalent Linear Analysis of Bilinear Hysteretic Isolation Systems

The design displacement, its corresponding acceleration performance, and the re-centering performance of bilinear hysteretic isolation systems are adopted as previously determined design objectives for equivalent linear analysis. To demonstrate the applicability and generalization of the analysis procedure, two sets of values for damping modification factors are employed in the analysis: those provided by ASCE/SEI 7-16, and those estimated for different ranges of the ratios of effective periods of seismic isolation systems to pulse periods of ground motions. To investigate a broad range of seismic responses of base-isolated structures, 15 pulse-like near-fault ground motions are used for numerical demonstration. The analysis procedure is numerically verified to be practically feasible. A numerical comparison also shows that the three design objectives previously determined in the analysis procedure are sufficiently conservative compared with analysis results from nonlinear dynamic response history, even when subjected to pulse-like near-fault ground motions. Regarding the approximation to maximum inelastic acceleration and displacement responses, it is particularly more conservative for the former when the design displacement is greater and when adopting values of the damping modification factors provided in ASCE/SEI 7-16. For the approximation to dynamic residual displacement responses, the influences of pulse-like near-fault ground motions and different design objectives on the re-centering performance of bilinear hysteretic isolation systems still need further study.

Evaluating the Accuracy of an Equivalent Linear Model in Predicting Peak Displacement of Seismic Isolation Systems using Single Friction Pendulum Bearings

This study evaluates the accuracy of an equivalent linear model in predicting peak nonlinear time-history displacement of seismic isolation systems with single friction pendulum bearings. To perform this evaluation, dynamic response of numerical models of 120 isolation systems subjected to 390 strong earthquake ground motions, including motions with pulse and motions without pulse, was analyzed and statistically processed. The results show that the equivalent linear model can partly predict the peak displacement of its counterpart nonlinear model. However, the equivalent model can also underestimate or overestimate the peak displacement. On average sense, the equivalent linear model underestimates small peak displacement and overestimates large peak displacement. It is also observed that the relationship between linear and nonlinear peak displacements depends on ground motion types. Based on the analysis data, equations representing relationship between linear and nonlinear peak displacements at different reliable levels for different ground motion types were proposed. These equations can be used in practice.

Seismic Performance of Piping Systems of Isolated Nuclear Power Plants Determined by Numerical Considerations

The interest in the seismic performance of nuclear power plants has increased worldwide since the Fukushima Daiichi Nuclear Power Plant incident. In Korea, interest in the seismic safety of nuclear power plants has increased since the earthquake events in Gyeongju (2016) and Pohang (2017). In Korea, studies have been conducted to apply seismic isolation systems to ensure seismic safety while minimizing the design changes to nuclear power plants. Nuclear power plants with seismic isolation systems may have a higher seismic risk due to the failure of the piping system in the structure after a relatively large displacement. Therefore, it is essential to secure the seismic safety of pipes for the safe operation of nuclear power plants. The seismic safety of pipes is determined by seismic fragility analysis. Seismic fragility analysis requires many seismic response analyses because it is a statistical approach to various random variables. Typical numerical conditions affecting the seismic response analysis of pipes are the convergence conditions and mesh size in numerical analysis. This study examined the change in the seismic safety of piping according to the numerical conditions. The difference in the seismic response analysis results of the piping according to the mesh size was analyzed comparatively. In addition, the change in the seismic fragility curve of the piping according to the convergence conditions was investigated.

Increasing the seismic resistance of operated buildings using special seismic protection methods

The change in the level of seismicity of buildings and structures occurs as a result of updating the maps of general seismic zoning. Ensuring the seismic resistance of buildings and structures is a factor that must be taken into account, especially during construction in seismically active regions. Nowadays, one of the main approaches to increasing seismic resistance is the use of various seismic isolation systems. It is not always profitable and rational to increase the seismic resistance of building structures or foundations for equipment by simply increasing the strength. A classification of seismic reinforcement systems is given, among which the most sparing are special methods of seismic protection in the form of seismic isolation. Practical examples of the use of seismic isolation systems to improve the seismic resistance of existing buildings are given. A computational study was carried out, the result of which showed the effectiveness of using rubber-metal supports for hanging the seismic resistance of buildings.

Some problems vibration and protection of buiding and structures using blocks

The basic concept of vibration and seismic insulation of buildings and structures based on the use of rubber seismic blocks (RSB) is considered. The concept of seismic isolation of structures is very relevant. In Japan, New Zealand, France, Greece, England, the United States and a number of other countries, it has been successfully used to protect such important structures as nuclear power plants, schools, bridges, museums, administrative and residential buildings from earthquakes. In Ukraine, the concept developed in two ways: the development of seismic isolation blocks for earthquake protection of residential buildings; development of vibration isolation blocks for vibration protection of heavy equipment (weight up to 300 tons, used in Russia, Ukraine) and residential buildings. For the practical application of building seismic isolation systems by the N. S. Geotechnical Mechanics Institute. Experimental studies were carried out to substantiate the RSB parameters, their designs were patented, design documentation was developed and experimental samples of three types of rubber-metal seismic protection blocks with a diameter of 400 mm and 500 mm and a total height of the rubber layer: 2 120 120 mm, 2х70 mm and 2х50 mm were made. The results of the calculation of a rubber-metal seismic support used as an element of vibration-seismic protection of multi-storey residential buildings are presented. The calculation results obtained by approximate analytical methods are compared with experimental data for samples of seismic supports. The design of a pile with vibration-insulating rubber supports is considered. The developed and tested RSB structures were used for vibration protection against metro trains and vehicles of residential buildings in Kiev: a 10-section 10-storey residential building on Kikvidze Street, three 27-storey buildings on Obolonsky Avenue and a residential complex of three houses in Lviv. Vibration and seismic isolation with the help of RSB provides the natural vibration frequency of the building in the horizontal plane of less than 1 Hz, which meets the requirements of the DBN and Eurocode 8 for the design of the building seismic isolation systems.

DEVELOPMENT OF CONSTRUCTIONS AND TECHNOLOGIES OF HIGH-PRECISION INSTALLATION OF PIPE CONCRETE COLUMNS OF KINEMATIC SYSTEMS OF SEISMIC PROTECTION OF CIVIL BUILDINGS FRAMES

Summary. Seismic isolation systems of kinematic type, selected as promising ones, first proposed in the former Soviet Union by Professor Yu.D. Cherepinsky, are considered. This technology was further developed in the works of Professor A.M. Kurzanov, who introduced his developments at the facilities of the Krasnodar Territory of the Russian Federation. However, the analyzed innovative domestic technology is not without its drawbacks. Subject of research: the design and technology of seismic isolation of overground floors of civil buildings using kinematic systems made of pipe-concrete columns. Materials and methods: analysis of the state of the art with a description of the positive and negative aspects of the existing technology, substantiation of the ways of possible progressive development of structures and technology of seismic isolation systems of the kinematic type, increasing the reliability of their operation under seismic load. Creation of graphic models of the nodes of support of concrete columns, implementing the intended directions in specific design solutions and technology for their implementation. Results. Patented designs of joints for pivotal support of pipe-concrete columns of kinematic systems for seismic isolation of frames of civil objects and a technological scheme for their alignment and high-precision installation. Conclusions: New design solutions have been proposed for the joints of the hinged support of pipe-concrete columns of kinematic systems of seismic isolation, as well as an improved technology for their installation, implying an increase in the reliability of their long-term operation in areas of high seismic activity.