Lessons Learned from Evaluating the Responses of Instrumented Buildings in the United States: The Effects of Supporting Building Characteristics on Floor Response Spectra

2019 ◽  
Vol 35 (1) ◽  
pp. 159-191 ◽  
Author(s):  
Hamidreza Anajafi ◽  
Ricardo A. Medina
Keyword(s):  
Response Spectra ◽  
Lateral Force ◽  
The United States ◽  
Lessons Learned ◽  
Seismic Demands ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Building Models ◽  
American Society ◽  
Instrumented Buildings

Floor spectra of many instrumented buildings are evaluated to identify and quantify influential parameters on the horizontal seismic responses of acceleration-sensitive nonstructural components (NSCs). It is shown that many of these parameters are not explicitly incorporated into the American Society of Civil Engineers ASCE 7-16 design equations and are challenging to capture through numerical building models. Significant torsional responses are identified, even for nominally regular buildings, which can increase seismic demands on NSCs located at a floor periphery. For many instrumented buildings, especially single-story ones, floor diaphragms behave as flexible in their plane. This behavior, while mitigating torsional responses, can increase demands on NSCs located away from elements of the lateral-force resisting systems. An evaluation of floor acceleration responses of instrumented buildings with basements reveals that in many cases, even with the presence of perimeter concrete basement walls, accelerations at grade level could be significantly larger than those at lower basement levels. Consideration should be given to establishing the seismic base at the lowermost basement elevation.

Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

2020 ◽  
Vol 36 (2_suppl) ◽  
pp. 213-237
Author(s):  
Miguel A Jaimes ◽  
Adrián D García-Soto
Keyword(s):  
Mexico City ◽  
Seismic Design ◽  
Soft Soil ◽  
Response Spectra ◽  
Elastic Model ◽  
Ground Acceleration ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Instrumented Buildings ◽  
Floor Acceleration

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

scholarly journals A practice-oriented method for estimating elastic floor response spectra

2020 ◽  
Vol 53 (3) ◽  
pp. 116-136 ◽  
Author(s):  
Kieran Haymes ◽  
Timothy Sullivan ◽  
Reagan Chandramohan
Keyword(s):  
Response Spectra ◽  
Superposition Method ◽  
Acceleration Response ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Acceleration Response Spectra ◽  
Modal Superposition Method ◽  
Displacement Response Spectra ◽  
Instrumented Buildings ◽  
Floor Acceleration

A practice-oriented modal superposition method for setting elastic floor acceleration response spectra is proposed in this paper. The approach builds on previous contributions in the literature, making specific recommendations to explicitly consider floor displacement response spectra and accounts for uncertainty in modal characteristics. The method aims to provide reliable predictions which improve on existing code methods but maintain simplicity to enable adoption in practical design. This work is motivated by recent seismic events which have illustrated the significant costs that can be incurred following damage to secondary and nonstructural components within buildings, even where the structural system has performed well. This has prompted increased attention to the seismic performance of nonstructural components with questions being raised about the accuracy of design floor acceleration response spectra used in practice. By comparing floor acceleration response spectra predicted by the proposed method with those recorded from instrumented buildings in New Zealand, it is shown that the proposed approach performs well, particularly if a good estimate of the building’s fundamental period of vibration is available.

Floor Spectra Estimates for an Industrial Special Concentrically Braced Frame Structure

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Roberto Javier Merino Vela ◽  
Emanuele Brunesi ◽  
Roberto Nascimbene
Keyword(s):  
Time History ◽  
Response Spectra ◽  
Frame Structure ◽  
Eurocode 8 ◽  
Industrial Complex ◽  
Braced Frame ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

Nonstructural components play an important role in the correct functioning of industrial facilities, which may suffer greatly from earthquake-induced actions, as demonstrated by past seismic events. Therefore, the correct evaluation of seismic demands acting upon them is of utmost importance when assessing or designing an industrial complex exposed to seismic hazard. Among others, nonlinear time history analyses (NLTHA) of structural systems including nonstructural elements and floor response spectra are well-known methods for computing these actions, the former being more accurate and the latter being less onerous. This work focuses on deriving floor spectra for a steel special concentrically braced frame (SCBF), which is a common type of lateral-load resisting system for industrial frames. The results are used to compute the seismic actions on a small liquid storage tank mounted on the case study frame. Additionally, the results are compared to those obtained by modeling the structure and the tank together, that is, by modeling the tank explicitly and incorporating it within the model of the support structure. To this end, a simple model, consisting of two uncoupled single degree-of-freedom systems, is used for the tank. The floor spectra resulting from both approaches are compared to establish differences in the behavior of the structure and nonstructural element/component. Finally, the seismic demand on the tank—obtained by direct and indirect analyses—is compared to that obtained by applying ASCE 7-10 and Eurocode 8 prescriptions.

A Spectrum-to-Spectrum Method for Calculating Uniform Hazard Floor Response Spectra

2017 ◽  
Author(s):  
Andrea Lucchini ◽  
Paolo Franchin ◽  
Fabrizio Mollaioli
Keyword(s):  
Ground Motion ◽  
Response Spectra ◽  
Seismic Demand ◽  
Spectral Acceleration ◽  
Demand Model ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Annual Frequency ◽  
The Mean ◽  
Mean Annual Frequency

In codes’ provisions and design procedures for acceleration-sensitive nonstructural components, seismic demand is commonly defined by means of floor response spectra expressed in terms of pseudo-acceleration. Depending on the considered analysis method, floor response spectra may be derived from floors’ acceleration histories, based on structural response-history analysis, or calculated using a predictive equation from a given input ground motion spectrum. Methods for estimating floor response spectra that are based on the second alternative are commonly called spectrum-to-spectrum methods. The objective of this paper is to briefly review these methods, and to discuss the main assumptions they are based on. Both predictive equations from selected seismic codes and proposals from the literature are included in the review. A new probability-based method, recently developed by the Authors for generating uniform hazard floor response spectra, namely, floor response spectra whose ordinates are characterized by a given target value of the mean annual frequency of being exceeded, is also described. By using this method floor spectra are determined through closed-form equations, given the mean annual frequency of interest, the damping ratio of the spectra, the modal properties of the structure, and three uniform hazard ground spectra. The method is built on a proposal for a probabilistic seismic demand model that relates the ground spectral acceleration with the floor spectral acceleration, and is able to explicitly account for the ground motion variability of the nonstructural response. Results for a case study consisting of a service frame of a visbreaking unit in an oil refinery are presented to show the good predictive accuracy of the method with respect to exact uniform hazard floor response spectra obtained through a standard probabilistic analysis.

Floor response spectra for seismic design of operational and functional components of concrete buildings in Canada

2010 ◽  
Vol 37 (12) ◽  
pp. 1590-1599 ◽  
Author(s):  
M. Shooshtari ◽  
M. Saatcioglu ◽  
N. Naumoski ◽  
S. Foo
Keyword(s):  
Structural Damage ◽  
Response Spectra ◽  
Electrical Equipment ◽  
Lateral Force ◽  
Rational Approach ◽  
Concrete Buildings ◽  
Design Spectra ◽  
Floor Response Spectra ◽  
Canadian City ◽  
Functional Components

It has been observed during previous earthquakes that the damage to operational and functional components of buildings often result in more injuries, fatalities and property damage than those inflicted by structural damage. Operational and functional components of a building include architectural components, mechanical and electrical equipment, as well as building contents. A rational approach to designing these elements against seismic excitations involves the use of floor design spectra. The development of such design spectra for buildings in Canada constitutes the objective of the paper. This objective was achieved by conducting comprehensive analyses of selected reinforced concrete buildings, with different lateral force resisting systems and building heights, under code compatible earthquake records for an eastern and a western Canadian city. It was observed that the floor response was significantly amplified, especially for buildings with short periods. Generally, the higher floors showed higher amplifications with differences in spectra between the floors being more pronounced in low-rise buildings and shear wall buildings with short fundamental periods. The results provided a large volume of data to generate floor response spectra for the design of operational and functional components of buildings in Canada. The details of the approach and the design spectra are presented in the paper.

Lessons Learned from Recent Earthquakes and Research and Implications for Earthquake-Resistant Design of Building Structures in the United States

1986 ◽  
Vol 2 (4) ◽  
pp. 825-858 ◽  
Author(s):  
Vitelmo V. Bertero
Keyword(s):  
Lateral Force ◽  
The United States ◽  
Lessons Learned ◽  
Structural Quality ◽  
Building Structures ◽  
Response Modification Factor ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Modification Factor ◽  
Recent Earthquakes

Following an overview of the special problems inherent in the design and construction of earthquake-resistant buildings in regions of high seismic risk, the techniques that will be required to solve these problems in the U.S. are discussed. Some lessons learned from recent earthquakes, particularly those in Chile and Mexico in 1985, are discussed as are some results of integrated analytical and experimental research at the University of California, Berkeley. The implications of the ground motions recorded during the 1985 Mexican and Chilean earthquakes, the performance of buildings during the Mexican earthquake, and the research results previously discussed are then assessed with respect to seismic-resistant design regulations presently in force (UBC) as well as those formulated by ATC 3-06 and the Tentative Lateral Force Requirements recently developed by the Seismology Committee of SEAOC. The rationale for and reliability of the values suggested by the ATC for the “Response Modification Factor R” and by the SEAOC Seismology Committee for the “Structural Quality Factor Rw” are reviewed in detail. In the conclusion to the paper, two solutions for improving the earthquake-resistant design of building structures are proposed: an ideal (rational) method to be implemented in the future, and a compromise solution that can be implemented immediately.

The 1970s

2011 ◽  
Author(s):  
Thomas Borstelmann
Keyword(s):  
Civil Rights ◽  
Free Market ◽  
The United States ◽  
Global Perspective ◽  
Retirement Plans ◽  
Free Agency ◽  
The World ◽  
The Disabled ◽  
Oil Crisis ◽  
American Society

This book looks at an iconic decade when the cultural left and economic right came to the fore in American society and the world at large. While many have seen the 1970s as simply a period of failures epitomized by Watergate, inflation, the oil crisis, global unrest, and disillusionment with military efforts in Vietnam, this book creates a new framework for understanding the period and its legacy. It demonstrates how the 1970s increased social inclusiveness and, at the same time, encouraged commitments to the free market and wariness of government. As a result, American culture and much of the rest of the world became more—and less—equal. This book explores how the 1970s forged the contours of contemporary America. Military, political, and economic crises undercut citizens' confidence in government. Free market enthusiasm led to lower taxes, a volunteer army, individual 401(k) retirement plans, free agency in sports, deregulated airlines, and expansions in gambling and pornography. At the same time, the movement for civil rights grew, promoting changes for women, gays, immigrants, and the disabled. And developments were not limited to the United States. Many countries gave up colonial and racial hierarchies to develop a new formal commitment to human rights, while economic deregulation spread to other parts of the world, from Chile and the United Kingdom to China. Placing a tempestuous political culture within a global perspective, this book shows that the decade wrought irrevocable transformations upon American society and the broader world that continue to resonate today.

Characteristics of Physician Relocation Following Hurricane Katrina

2009 ◽  
Vol 95 (1) ◽  
pp. 6-12
Author(s):  
Kusuma Madamala ◽  
Claudia R. Campbell ◽  
Edbert B. Hsu ◽  
Yu-Hsiang Hsieh ◽  
James James
Keyword(s):  
Hurricane Katrina ◽  
Gulf Coast ◽  
General Medicine ◽  
The United States ◽  
Lessons Learned ◽  
Bivariate Analysis ◽  
Fisher Exact Test ◽  
Exact Test ◽  
Factors Associated ◽  
The Impact

ABSTRACT Introduction: On Aug. 29, 2005, Hurricane Katrina made landfall along the Gulf Coast of the United States, resulting in the evacuation of more than 1.5 million people, including nearly 6000 physicians. This article examines the relocation patterns of physicians following the storm, determines the impact that the disaster had on their lives and practices, and identifies lessons learned. Methods: An Internet-based survey was conducted among licensed physicians reporting addresses within Federal Emergency Management Agency-designated disaster zones in Louisiana and Mississippi. Descriptive data analysis was used to describe respondent characteristics. Multivariate logistic regression was performed to identify the factors associated with physician nonreturn to original practice. For those remaining relocated out of state, bivariate analysis with x2 or Fisher exact test was used to determine factors associated with plans to return to original practice. Results: A total of 312 eligible responses were collected. Among disaster zone respondents, 85.6 percent lived in Louisiana and 14.4 percent resided in Mississippi before the hurricane struck. By spring 2006, 75.6 percent (n = 236) of the respondents had returned to their original homes, whereas 24.4 percent (n = 76) remained displaced. Factors associated with nonreturn to original employment included family or general medicine practice (OR 0.42, 95 percent CI 0.17–1.04; P = .059) and severe or complete damage to the workplace (OR 0.24, 95 percent CI 0.13–0.42; P < .001). Conclusions: A sizeable proportion of physicians remain displaced after Hurricane Katrina, along with a lasting decrease in the number of physicians serving in the areas affected by the disaster. Programs designed to address identified physician needs in the aftermath of the storm may give confidence to displaced physicians to return.

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