A Generalized Conditional Mean Spectrum and Its Application for Intensity-Based Assessments of Seismic Demands

2017 ◽  
Vol 33 (1) ◽  
pp. 123-143 ◽  
Author(s):  
N. Simon Kwong ◽  
Anil K. Chopra
Keyword(s):  
Computational Effort ◽  
Seismic Demands ◽  
Earthquake Scenario ◽  
Conditional Mean ◽  
Conditional Mean Spectrum ◽  
Accuracy And Precision ◽  
Target Spectrum ◽  
Hazard Level ◽  
Vector Valued

When the response of a structure is influenced significantly by multiple vibration modes, the seismic demands determined by response history analyses with ground motions selected to match a single conditional mean spectrum (CMS) may be unconservative for several response quantities. An existing solution to this problem is to determine the demand as the maximum of mean demands from several CMSs. To reduce the computational effort while maintaining accuracy and precision, we introduce an alternative engineering solution that is based on a simplified version of the generalized CMS, where two specified conditioning spectral accelerations share a common hazard level. vector-valued disaggregation is developed herein to provide a single earthquake scenario for the target spectrum. The results from a realistic case study suggest that the proposed spectrum provides seismic demands that are as accurate and precise as those obtained from analyzing the structure with multiple CMSs while simultaneously reducing the computational effort by a factor of 2 or more.

Selecting, scaling, and orienting three components of ground motions for intensity-based assessments at far-field sites

2020 ◽  
Vol 36 (3) ◽  
pp. 1013-1037 ◽  
Author(s):  
N. Simon Kwong ◽  
Anil K. Chopra
Keyword(s):  
Three Dimensional ◽  
Vertical Component ◽  
Uniform Hazard Spectrum ◽  
Conditional Mean ◽  
Conditional Mean Spectrum ◽  
Scale Factors ◽  
Target Spectrum ◽  
Wide Range ◽  
Orthogonal Components ◽  
Three Components

This article develops a methodology for selecting, scaling, and orienting three orthogonal components of ground motion (GM) when conducting intensity-based assessments of structures. Target spectra for selecting multicomponent GMs are critically examined and strategies for selecting hazard-consistent GMs are investigated. The Conditional Mean Spectrum–Uniform Hazard Spectrum (CMS-UHS) Composite Spectrum is proposed as an alternative to several Conditional Mean Spectra for selecting multicomponent GMs when conducting intensity-based assessments of complex three-dimensional (3D) structures. To ensure hazard consistency, multicomponent GMs should be selected using (a) the target spectrum for the vertical component of GM, (b) a wide range of vibration periods, and (c) scale factors that are constrained. With constrained scale factors, all three components of a GM can be reasonably scaled either by the same scale factor or by different scale factors.

A multi-attribute approach to select the best method for repairing river bridge columns

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mitra Salmaninezhad ◽  
S. Mahmood Jazayeri Moghaddas
Keyword(s):  
Evaluation Criteria ◽  
Bridge Columns ◽  
Pier Scour ◽  
Content Type ◽  
Accuracy And Precision ◽  
Proposed Model ◽  
Research Findings ◽  
Multi Attribute Decision Making ◽  
Weighing Method

PurposePier scour is one of the main causes of damage to the columns of the river bridges. It is essential to select the best method among various repair methods based on different evaluation indices. However, there is no procedure for ranking these repair methods based on their attributes. The present study seeks to set an approach for this ranking.Design/methodology/approachIn this paper, a multi-attribute decision-making (MADM) model is presented for ranking the repair techniques, in which alternatives are examined using the most important evaluation criteria. In addition, a combination of entropy and eigenvector methods has been proposed for weighting these attributes. A case study is then used to demonstrate the applicability and the validity of the method.FindingsThe execution of the model using two multi-criteria methods yielded similar results, which confirms its accuracy and precision. Moreover, the research findings showed the consistency of the objective and subjective weighting methods and the conformity of the weights obtained for the attributes from the combination of these methods to the nature of the problem.Originality/valueThe selection of the proper method for repairing the bridge columns plays an essential role in success of the bridge restoration. The proposed model introduces an approach for ranking repair methods and selecting the best one that has not been presented so far. Also, the weighing method for attributes is an innovative method for ranking restoration methods that has been proven in a case study.

Integrity and Fidelity Evaluation of Digital Evidence in Live Forensics

2014 ◽  
Vol 571-572 ◽  
pp. 90-99
Author(s):  
Lian Hai Wang ◽  
Qiu Liang Xu
Keyword(s):  
Experimental Error ◽  
Good Accuracy ◽  
Digital Evidence ◽  
System Error ◽  
Accuracy And Precision ◽  
Novel Method ◽  
Memory Acquisition ◽  
Measure Error ◽  
Live Forensics

The integrity and fidelity of digital evidence are very important in live forensics. Previous research has studied the uncertainty of live forensics based on different memory snapshots. However, this kind of method is not effective in practice. In fact, memory images are usually acquired by using forensics tools instead of using snapshots. Therefore, the integrity and fidelity of live evidence should be evaluated during the acquisition process. In this paper, we give a new viewpoint that memory acquisition can be regarded as a measurement of memory data. From this viewpoint, we evaluate the integrity and fidelity of live evidence in the process of physical memory acquisition. Firstly, several definitions about memory acquisition measure error are introduced to describe the trusty. Then, we analyze the experimental error and propose some suggestions on how to reduce it. A novel method is also developed to calculate the system error in detail. The results of a case study on Windows 7 and VMware virtual machine show that the experimental error has good accuracy and precision, which demonstrate the efficacy of the proposed reducing methods. The system error is also evaluated, that is, it accounts for the whole error from 30% to 50%. Last, a method is proposed to calculate changes or error of system process.

scholarly journals Evaluation of a Modified MPA Procedure Assuming Higher Modes as Elastic to Estimate Seismic Demands

2004 ◽  
Vol 20 (3) ◽  
pp. 757-778 ◽  
Author(s):  
Anil K. Chopra ◽  
Rakesh K. Goel ◽  
Chatpan Chintanapakdee
Keyword(s):  
Structural Engineering ◽  
Pushover Analysis ◽  
Computational Effort ◽  
Attractive Alternative ◽  
Engineering Practice ◽  
Seismic Demands ◽  
History Analysis ◽  
Modes Of Vibration ◽  
Response History Analysis ◽  
Damped Systems

The modal pushover analysis (MPA) procedure, which includes the contributions of all significant modes of vibration, estimates seismic demands much more accurately than current pushover procedures used in structural engineering practice. Outlined in this paper is a modified MPA (MMPA) procedure wherein the response contributions of higher vibration modes are computed by assuming the building to be linearly elastic, thus reducing the computational effort. After outlining such a modified procedure, its accuracy is evaluated for a variety of frame buildings and ground motion ensembles. Although it is not necessarily more accurate than the MPA procedure, the MMPA procedure is an attractive alternative for practical application because it leads to a larger estimate of seismic demands, improving the accuracy of the MPA results in some cases (relative to nonlinear response history analysis) and increasing their conservatism in others. However, such conservatism is unacceptably large for lightly damped systems, with damping significantly less than 5%. Thus the MMPA procedure is not recommended for such systems.

scholarly journals AVALIAÇÕES DE RISCO EM BARRAGENS: ESTUDO DE CASO DA BARRAGEM MALCOZINHADO NO NORDESTE BRASILEIRO

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
Mariana Campos Fontenelle ◽  
Alexandre de Sousa Fontenelle ◽  
Yago Machado Pereira de Matos ◽  
Fernando Feitosa Monteiro
Keyword(s):  
Risk Assessment ◽  
Water Resources ◽  
Water Resources Management ◽  
The State ◽  
Management Company ◽  
Resources Management ◽  
Hazard And Risk ◽  
Hazard Level ◽  
Brazilian Northeast

RESUMO: O presente trabalho tem a proposta de avaliar a eficácia de duas metodologias de avaliação de risco de uma barragem no Nordeste Brasileiro no intervalo de 10 anos, baseando-se na inspeção e no nível de ameaça. Utiliza-se a metodologia Nível de Perigo da Barragem (NPB) para cálculo do nível de ameaça (Fontenelle, 2007) e para o cálculo do risco as metodologias da Companhia de Gestão dos Recursos Hídricos do Ceará (COGERH) e do Conselho Nacional de Recursos Hídricos (CNRH). Observa-se que o crescente número de barragens soma-se a preocupação com a segurança destas. Face a isto, utiliza-se a avaliação de risco como forma de priorizar ações de manutenção e recuperação. O estudo de caso ocorreu na Barragem Malcozinhado, localizada no município de Cascavel, no estado do Ceará. Com base na inspeção, calcula-se o nível de ameaça e o risco, compara-se estes com os resultados de 2006. Assim, observou-se o aumento no nível de ameaça, no entanto, o risco permaneceu, em geral, baixo, semelhante aos resultados de 2006. Este resultado se deve ao fato de que o número de anomalias aumentou, porém trata-se de uma barragem jovem, de pequeno porte e inspecionada regularmente.ABSTRACT: The present study has the proposal of evaluating the effectiveness of two methodologies of risk Assessment of a Brazilian Northeast dam in a range of 10 years, based on the inspection and the level of hazard. The methodology used for calculating the hazard level is the Dam Hazard Level (NPB). In addiction, in order to evaluate the risk is used the methodology of the Water Resources Management Company of Ceará (COGERH) and the methodology of National Resources Council Water (CNRH). The number of dams is increasing with to the concern for their safety. In view of this, risk assessment is used as a tool to prioritizing maintenance and recovery actions. The case study occurred in the Malcozinhado Dam, located in the municipality of Cascavel, in the state of Ceará. Based on the inspection, the level of hazard and risk is calculated, compared to the results for 2006. Thus, the increase in the level of hazard was observed, but the risk remained generally low, similar to 2006 result. This result is due to the fact that the number of anomalies has increased, but it is a young, small and regularly inspected dam.

Damage Identification of Multimember Structure using Improved Neural Networks

2013 ◽  
Vol 3 (3) ◽  
pp. 57-75
Author(s):  
M. Rajendra ◽  
K. Shankar
Keyword(s):  
Damage Identification ◽  
Latin Hypercube Sampling ◽  
Search Space ◽  
Computational Effort ◽  
Frequency Change ◽  
The Novel ◽  
Damage Prediction ◽  
Rbf Network ◽  
Accuracy And Precision ◽  
Two Stages

A novel two stage Improved Radial Basis Function (IRBF) neural network for the damage identification of a multimember structure in the frequency domain is presented. The improvement of the proposed IRBF network is carried out in two stages. Conventional RBF network is used in the first stage for preliminary damage prediction and in the second stage reduced search space moving technique is used to minimize the prediction error. The network is trained with fractional frequency change ratios (FFCs) and damage signature indices (DSIs) as effective input patterns and the corresponding damage severity values as output patterns. The patterns are searched at different damage levels by Latin hypercube sampling (LHS) technique. The performance of the novel IRBF method is compared with the conventional RBF and Genetic algorithm (GA) methods and it is found to be a good multiple member damage identification strategy in terms of accuracy and precision with less computational effort.

scholarly journals Optimization Dubins Path of Multiple UAVs for Post-Earthquake Rapid-Assessment

2020 ◽  
Vol 10 (4) ◽  
pp. 1388 ◽  
Author(s):  
Moning Zhu ◽  
Xuehua Zhang ◽  
He Luo ◽  
Guoqiang Wang ◽  
Binbin Zhang
Keyword(s):  
Rapid Assessment ◽  
Real Data ◽  
Jiuzhaigou Earthquake ◽  
Routing Problem ◽  
Earthquake Scenario ◽  
Curvature Constraint ◽  
Team Orienteering ◽  
Relief Operations ◽  
Source Of Information

In the last decade, with the wide application of UAVs in post-earthquake relief operations, the images and videos of affected areas obtained by UAVs immediately after a seismic event have become an important source of information for post-earthquake rapid assessment, which is crucial for initiating effective emergency response operations. In this study, we first consider the kinematic constraints of UAV and the Dubins curve is introduced to fit the shortest flyable path for each UAV that meets the maximum curvature constraint. Second, based on the actual requirements of post-earthquake rapid assessment, heterogeneous UAVs, multi-depot launching, and targets allowed access to multiple times, the paper proposes a multi-UAV rapid-assessment routing problem (MURARP). The MURARP is modeled as the multi-depot revisit-allowed Dubins TOP with variable profit (MD-RDTOP-VP) which is a variant of the team orienteering problem (TOP). Third, a hybrid genetic simulated annealing (HGSA) algorithm is developed to solve the problem. The result of numerical experiments shows that the HGSA algorithm can quickly plan flyable paths for heterogeneous UAVs to maximize the expected profit. Finally, a case study based on real data of the 2017 Jiuzhaigou earthquake in China shows how the method can be applied in a post-earthquake scenario.

Incorporation of Preferences in an Evolutionary Algorithm Using an Outranking Relation

2011 ◽  
Vol 2 (1) ◽  
pp. 63-85 ◽  
Author(s):  
Eunice Oliveira ◽  
Carlos Henggeler Antunes ◽  
Álvaro Gomes
Keyword(s):  
Evolutionary Algorithm ◽  
Evolutionary Process ◽  
Computational Effort ◽  
Cognitive Effort ◽  
Point Of View ◽  
Electrical Networks ◽  
Technical Parameters ◽  
Outranking Relation ◽  
Electre Tri

The incorporation of preferences into Evolutionary Algorithms (EA) presents some relevant advantages, namely to deal with complex real-world problems. It enables focus on the search thus avoiding the computation of irrelevant solutions from the point of view of the practical exploitation of results (thus minimizing the computational effort), and it facilitates the integration of the DM’s expertise into the solution search process (thus minimizing the cognitive effort). These issues are particularly important whenever the number of conflicting objective functions and/or the number of non-dominated solutions in the population is large. In EvABOR (Evolutionary Algorithm Based on an Outranking Relation) approaches preferences are elicited from a decision maker (DM) with the aim of guiding the evolutionary process to the regions of the space more in accordance with the DM’s preferences. The preferences are captured and made operational by using the technical parameters of the ELECTRE TRI method. This approach is presented and analyzed using some illustrative results of a case study of electrical networks.

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