Advantages and Limitations of Seismic Isolation

1991 ◽  
Vol 7 (2) ◽  
pp. 301-324 ◽  
Author(s):  
John Stanton ◽  
Charles Roeder
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Large Displacements ◽  
Conventional Analysis ◽  
Equivalent Linear ◽  
Methods Of Analysis ◽  
Dynamic Forces ◽  
The Impact

Under many circumstances, seismic isolation is an effective way of reducing the impact of earthquakes on structures. Dynamic forces in the structure itself are reduced at the expense of relatively large displacements in the isolators. These displacements can generally be predicted adequately by simple methods and accommodated without difficulty. However, some circumstances appear to exist where the isolator displacements might be significantly larger than conventional analysis would suggest, or where simplified methods of analysis may prove inadequate and fail to predict the response properly. The paper explores the limits of the applicability of equivalent linear analyses and the response to ground motions which might lead to large displacements isolation that can be achieved.

scholarly journals Earthquake-Induced Pounding of Medium-to-High-Rise Base-Isolated Buildings

2019 ◽  
Vol 9 (21) ◽  
pp. 4681
Author(s):  
Hosein Naderpour ◽  
Payam Danaeifard ◽  
Daniel Burkacki ◽  
Robert Jankowski
Keyword(s):  
Seismic Isolation ◽  
General Trend ◽  
Ground Motions ◽  
Seismic Damage ◽  
Large Displacements ◽  
Gap Size ◽  
Structural Pounding ◽  
High Rise ◽  
Adjacent Structures ◽  
Fixed Base

During earthquakes, out-of-phase vibrations in adjacent buildings with limited distance may cause pounding between them. In recent years, the use of seismic isolation has expanded considerably as an effective approach to reduce seismic damage. However, the isolated building experiences large displacements during earthquakes, and there is a possibility of collisions with adjacent structures. The research on earthquake-induced pounding of base-isolated buildings has been mainly focused on interactions between low structures. In this paper, the influence of structural pounding on the response of medium-to-high-rise base-isolated buildings is investigated under different ground motions. The analysis has been focused on collisions between two insufficiently separated five-story and eight-story base-isolated and fixed base buildings aligned in three different configurations. The results of the study indicate that structural pounding may significantly increase the response of medium-to-high-rise base-isolated buildings during earthquakes. Moreover, substantial dependence of the structural behavior on the gap size between structures has been observed. The general trend shows the reduction in the pounding-involved response with the increase in the gap size value. The results indicate that the increase in the response of the base-isolated building is larger when the height of the structure is bigger. They also show that larger amplifications of peak accelerations of the upper stories can be expected due to collisions. On the other hand, the amplifications of the story shears have not shown any specific trend for different stories of the analyzed base-isolated building.

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

2021 ◽  
pp. 2250001
Author(s):  
Shiang-Jung Wang ◽  
Yin-Nan Huang ◽  
Hsueh-Wen Lee ◽  
Yu-Wen Chang
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Linear Analysis ◽  
Analysis Procedure ◽  
Numerical Comparison ◽  
Near Fault ◽  
Equivalent Linear ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Equivalent Linear Analysis

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.

scholarly journals Vertical to Horizontal UHS Ratios for Low to Medium Seismicity Regions with Deep Soil atop Deep Geological Sediments—An Example of the City of Osijek, Croatia

2021 ◽  
Vol 11 (15) ◽  
pp. 6782
Author(s):  
Borko Đ. Bulajić ◽  
Marijana Hadzima-Nyarko ◽  
Gordana Pavić
Keyword(s):  
Ground Motions ◽  
Spectral Amplitude ◽  
Eurocode 8 ◽  
Uniform Hazard Spectra ◽  
Study Region ◽  
Spectral Estimates ◽  
Local Soil ◽  
The Impact ◽  
Deep Soils ◽  
The City

The severity of vertical seismic ground motions is often factored into design regulations as a component of their horizontal counterparts. Furthermore, most design codes, including Eurocode 8, ignore the impact of local soil on vertical spectra. This paper investigates vertical pseudo-absolute acceleration spectral estimates, as well as the ratios of spectral estimates for strong motion in vertical and horizontal directions, for low to medium seismicity regions with deep local soil and deep geological sediments beneath the local soil. The case study region encompasses the city of Osijek in Croatia. New regional frequency-dependent empirical scaling equations are derived for the vertical spectra. According to these equations, for a 0.3 s spectral amplitude at deep soils atop deep geological sediments compared to the rock sites, the maximum amplification is 1.48 times. The spectra of vertical components of various real strong motions recorded in the surrounding region are compared to the empirical vertical response spectra. The new empirical equations are used to construct a Uniform Hazard Spectra for Osijek. The ratios of vertical to horizontal Uniform Hazard Spectra are generated, examined, and compared to Eurocode 8 recommendations. All the results show that local soil and deep geology conditions have a significant impact on vertical ground motions. The results also show that for deep soils atop deep geological strata, Eurocode 8 can underestimate the vertical to horizontal spectral ratios by a factor of three for Type 2 spectra while overestimating them by a factor of two for Type 1 spectra.

A simplified iterative approach for testing the pulse derailment of light rail vehicles across a viaduct to near-fault earthquake scenarios

2021 ◽  
pp. 095440972098741
Author(s):  
Ling-Kun Chen ◽  
Peng Liu ◽  
Li-Ming Zhu ◽  
Jing-Bo Ding ◽  
Yu-Lin Feng ◽  
...  
Keyword(s):  
Ground Motions ◽  
Simulation Software ◽  
Light Rail ◽  
Rail Transit ◽  
Light Rail Transit ◽  
Seismic Responses ◽  
Near Fault ◽  
Rail Vehicle ◽  
Pulse Type ◽  
The Impact

Near-fault (NF) earthquakes cause severe bridge damage, particularly urban bridges subjected to light rail transit (LRT), which could affect the safety of the light rail transit vehicle (“light rail vehicle” or “LRV” for short). Now when a variety of studies on the fault fracture effect on the working protection of LRVs are available for the study of cars subjected to far-reaching soil motion (FFGMs), further examination is appropriate. For the first time, this paper introduced the LRV derailment mechanism caused by pulse-type near-fault ground motions (NFGMs), suggesting the concept of pulse derailment. The effects of near-fault ground motions (NFGMs) are included in an available numerical process developed for the LRV analysis of the VBI system. A simplified iterative algorithm is proposed to assess the stability and nonlinear seismic response of an LRV-reinforced concrete (RC) viaduct (LRVBRCV) system to a long-period NFGMs using the dynamic substructure method (DSM). Furthermore, a computer simulation software was developed to compute the nonlinear seismic responses of the VBI system to pulse-type NFGMs, non-pulse-type NFGMs, and FFGMs named Dynamic Interaction Analysis for Light-Rail-Vehicle Bridge System (DIALRVBS). The nonlinear bridge seismic reaction determines the impact of pulses on lateral peak earth acceleration (Ap) and lateral peak land (Vp) ratios. The analysis results quantify the effects of pulse-type NFGMs seismic responses on the LRV operations' safety. In contrast with the pulse-type non-pulse NFGMs and FFGMs, this article's research shows that pulse-type NFGM derail trains primarily via the transverse velocity pulse effect. Hence, this study's results and the proposed method can improve the LRT bridges' seismic designs.

Spreadsheet Tool for Quick-Turn 3D Numerical Modeling of Package Thermal Performance With Non-Uniform Die Heating

2001 ◽  
Author(s):  
Abhay A. Watwe ◽  
Ravi S. Prasher
Keyword(s):  
Finite Element ◽  
Numerical Modeling ◽  
Finite Volume ◽  
Thermal Performance ◽  
Three Dimensional ◽  
3D Numerical Modeling ◽  
Conventional Analysis ◽  
Time Required ◽  
The Impact ◽  
Fourier Equation

Abstract Traditional methods of estimating package thermal performance employ numerical modeling using commercially available finite-volume or finite-element tools. Use of these tools requires training and experience in thermal modeling. This methodology restricts the ability of die designers to quickly evaluate the thermal impact of their die architecture due to the added throughput time required to enlist the services of a thermal analyst. This paper describes the development of an easy to use spreadsheet tool, which performs quick-turn numerical evaluations of the impact of non-uniform die heating. The tool employs well-established finite-volume numerical techniques to solve the steady-state, three-dimensional Fourier equation of conduction in the package geometry. Minimal input data is required and the inputs are customized using visual basic pull-down menus to assist die designers who may not be thermal experts. Data showing comparison of the estimates from the spreadsheet tool with that obtained from a conventional analysis using the commercially available finite element code ANSYS™ is also presented.

The SMRI-NIRS technology: development, validation and benefit

2021 ◽  
pp. 354-359
Author(s):  
Stephen N. Walford
Keyword(s):  
South African ◽  
Near Infrared ◽  
Technology Development ◽  
Correlation Coefficients ◽  
Test Methods ◽  
Analysis Method ◽  
Prediction Equations ◽  
Conventional Analysis ◽  
Methods Of Analysis ◽  
Conventional Methods

The Sugar Milling Research Institute NPC (SMRI) has developed a simple to use near-infrared spectroscopy (NIRS) transmission-based analysis method as an alternative to conventional methods for analysis of sugarcane factory stream samples. The technology provides rapid, simultaneous analysis of refractometric dry substance (rds), polarimetric sugar, sucrose, glucose, fructose, conductivity ash contents as well as colour and pH for all streams and additionally, dry solids for final molasses and eliminates the need for sample clarification chemicals. The analyte prediction equations were developed using conventional results of samples from 14 South African factories, analysed at SMRI using SANAS/ISO17025 accredited test methods, and NIRS scans of the same samples using up to 16 different NIRS instruments. The NIRS analyte prediction equations were validated against more than 1,500 independent factory samples that had been analysed by conventional methods of analysis, including samples from factories outside South Africa. The reproducibility of the NIRS results were equivalent to existing conventional analysis reproducibility values (juice and final molasses) and previously undocumented values determined for this study for conventional raw house analysis methods. Correlation coefficients of greater than 0.97 were recorded for all major analytes and greater than 0.9 for minor analytes when predicted results were compared against conventional results. A maintenance protocol was also developed to ensure that the prediction equations remain robust and can account for sample matrix variations that can occur from season to season. The SMRI-NIRS technology was installed at all 14 South African factories and found to be robust and give equivalent results to conventional methods of analysis.

scholarly journals Forensic Engineering Analysis of Dynamic Forces Created by Pedestrians Impacting Plate Glass at Different Speeds

2015 ◽  
Vol 32 (1) ◽  
Author(s):  
Michael Kravitz
Keyword(s):  
Impact Load ◽  
Building Code ◽  
Engineering Analysis ◽  
Glass Panel ◽  
Impact Speed ◽  
Dynamic Forces ◽  
Exit Door ◽  
Forensic Engineering ◽  
Pedestrian Impact ◽  
The Impact

This paper examines the effect of a pedestrian inadvertently impacting a glass panel adjacent to a glass exit door. The glass panel was full length and unmarked, violating the local building code and building commissioner directives. The defense argued that the old building code, to which the college building was constructed, was “grandfathered” and there was no violation. Initial witness and plaintiff statements indicated that the plaintiff was running when he struck the panel, which shattered and caused the plaintiff to incur injuries. The plaintiff testified later, in deposition, that he was walking when he struck the glass. The court needed to establish liability percentage, which is common in civil cases, and it was necessary to determine at what pedestrian impact speed the glass panel would break. The analysis used Timoshenko’s theory of vibration plates, Roark’s stress strain formulas, ergonomics, and human factors to estimate the impact load and stresses on the glass panel that caused failure.

scholarly journals Impact of Gust and Tectonic Drags on Irregular High Rise Structures

2020 ◽  
Vol 9 (9) ◽  
pp. 427-439
Keyword(s):  
Urban Infrastructure ◽  
High Rise ◽  
Aspect Ratios ◽  
Irregular Structures ◽  
Dynamic Forces ◽  
Gust Loads ◽  
Irregular Buildings ◽  
Structural Failures ◽  
The Impact ◽  
Base Width

As the population is growing and land becomes limited and new materials and construction technologies are built together, structural structures of this nature are growing larger and smaller, which are prone to two types of dynamic forces, tectonic drags and wind powers. In developing countries like India the exponential growth of the urban population has prompted a reassessment of the value of high – rise irregular buildings. For the construction of high - rise irregular buildings, the impact of gust loads is to be remembered. In India, gust caused numerous structural failures. IS 875:2015 Part-3 considers the gust loads on various kinds of irregular structures and IS 1893 (Part-1):2016 recognizes tectonic drags. The study focuses on peculiar constructions of different aspect ratios i.e. the impact of tears and tectonic drags. H / B ratio, with H being the overall construction system height; and B being the base width of the structure frame using STADD , Structure mass irregularities using E-TABS; from this paper we are examining the impact of wind (gusts), seismic (tectonical) load on building height by changing the number of floors with a the aspect rate. H / B ratio Many researchers design a system that is immune to tectonic drags, but the tectonic drag framework can not be built without causing damage. A large proportion of existing urban infrastructure is composed of vertical irregular structures.

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