ORCID Profile
0000-0003-4127-5337
Current Organisation
Universidade de São Paulo
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: FapUNIFESP (SciELO)
Date: 06-2019
DOI: 10.1590/S1983-41952019000300007
Abstract: Abstract The conventional design of concrete gravity dams still follows the deterministic method, which does not directly quantify the effect of uncertainties on the safety of the structure. The theory of structural reliability allows the quantification of safety of these structures, from the quantification of the inherent uncertainties in resistance and loading parameters. This article illustrates application of structural reliability theory to the case study analysis of a built concrete gravity dam. Results show that reliability of the built structure is greater than that of the designed structure. The study compares reliability for design conditions, with the corresponding safety coefficients, illustrating a lack of linearity between safety coefficients and reliability. Furthermore, the study shows which are the failure modes and the design parameters with greater influence on dam safety.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Informa UK Limited
Date: 03-11-2017
Publisher: Elsevier BV
Date: 10-2004
Publisher: Informa UK Limited
Date: 03-08-2018
Publisher: Springer Science and Business Media LLC
Date: 21-06-2021
Publisher: Elsevier BV
Date: 10-2019
Publisher: Society of Petroleum Engineers (SPE)
Date: 22-05-2020
DOI: 10.2118/201200-PA
Abstract: The development of exploratory wells is based on the interpretation of seismic readings by geotechnical field experts. Correlation wells, when they exist, are located very far, leading to large uncertainties and to different interpretations by different experts. Exploratory wells are expensive and risky endeavors, in particular deep wells with high-temperature and high-pressure conditions. Reaching reservoirs at record depths often requires challenging usual safety margins, which should be based on reliability analyses. In this paper, we present an empirical random kick model to combine the opinions of different specialists and the reliability analysis of casing subject to kick loads. The empirical kick model has a random kick volume and intensity, gas gravity, and influx depth. Three tubular strength models are considered: Barlow formula, von Mises stress, and Klever-Stewart model (Klever and Stewart 1998 Stewart and Klever 1998), with random yield stress and tube thickness. A typical 19,000 ft well is considered as a case study ex le, and the First-Order Reliability Method (FORM) is used as a probabilistic solver. Results show the differences between safety factors and reliability indices obtained for the three strength models. Sensitivity factors show that yield stress and model error are the most relevant random variable at shallow depths. Kick volume and influx depth are found to be the most relevant random variables of the kick model, especially at greater depths. The proposed empirical kick model is shown to have a significant impact on casing reliability, in comparison with a kick in which uncertain kick variables are assumed with uniform distribution.
Publisher: CRC Press
Date: 19-07-2011
DOI: 10.1201/B11332-337
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 05-2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2018
Publisher: FapUNIFESP (SciELO)
Date: 08-2018
DOI: 10.1590/S1983-41952018000400002
Abstract: Abstract This paper presents a study of the conformity of structural concrete blocks manufactured and used in masonry construction in Brazil. It is based on compressive strength tests, on dimensional analysis and absorption tests of over six thousand s les from three classes (A, B and C) and two modular sizes (M-15 and M-20). National results show that blocks tend to have an estimated compressive strength higher than specified, except blocks from class A. Regional results show that blocks manufactured in the northeast (NE) are consistently non-conforming, for all block classes. The study also shows that dimensional variations and absorption tests results are within code tolerances.
Publisher: Springer Science and Business Media LLC
Date: 26-10-2018
Publisher: FapUNIFESP (SciELO)
Date: 2021
DOI: 10.1590/S1983-41952021000400002
Abstract: abstract: The study of progressive collapse of structures using numerical models requires accurate modeling of geometrical nonlinearity and material failure behavior. Numerical models must demonstrate stability, such that localized member failures do not trigger numerical instabilities. Also, algorithms should be efficient, to limit the computational burden of analyzing multiple responses when considering the effects of uncertain loads, geometric and material variables. In this scientific domain, a comprehensive non-linear ductile-damage truss-element model has been recently presented by the authors. The model accounts for the geometrical and material nonlinearities observed during progressive collapse of structural systems. In this paper, the Felipe-Leonel-Haach-Beck (FLHB) model is calibrated to describe the response of Ultra-High-Performance Fiber Reinforced Concrete (UHPFRC). Based on a limited number of UHPFRC experimental curves, statistics of FLHB model parameters are obtained. These are employed in the probabilistic analysis of failure paths of truss structures under progressive collapse. Monte Carlo Simulation and the First Order Reliability Method are employed in the probabilistic failure path analyses. Six application ex les demonstrate the accuracy, robustness, and efficiency of the FLHB model in evaluation of failure paths of realistic structural systems.
Publisher: Wiley
Date: 14-08-2017
DOI: 10.1002/NME.5607
Publisher: CRC Press
Date: 27-05-2014
DOI: 10.1201/B17063-320
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 06-2014
Publisher: FapUNIFESP (SciELO)
Date: 08-2015
Publisher: FapUNIFESP (SciELO)
Date: 2023
DOI: 10.1590/S1983-41952023000200004
Abstract: abstract: Nowadays, structural “limit state” design is made using characteristic or nominal values of actions, partial safety factors and load combination factors. The actual loading that a structure will be subjected to throughout its life is not known at the design phase. Yet, probabilistic models of such loadings are useful for the rational determination of partial safety factors and load combination factors. The probabilistic model leading to nominal live loads of NBR 6120:2019 (Design Loads for Structures) has never been openly discussed. Herein a simple probabilistic model describing spatial and temporal variabilities of live loads in buildings is presented and discussed. The model is built as a sum of two stochastic processes representing the sustained and intermittent parts of the live load. Model parameters are the ones recommended by the Joint Committee on Structural Safety (JCSS), based on extensive surveys done in several countries. By way of Monte Carlo simulations, s le values of live load actions are obtained for buildings of different occupancy types. These values are compared with those recommended by international standards, and those recommended in NBR 6120:2019 and NBR 8681:2003 (Actions and Safety of Structures). The corresponding statistics for the fifty-year extreme and arbitrary point-in-time distributions of live loads are presented these statistics are very relevant for reliability analyses and for reliability-based code calibration. The stochastic live load model is also employed in a reliability-based calibration to obtain partial safety factors and load combination factors to be used in Brazilian design codes, for ultimate and serviceability limit state verifications.
Publisher: Springer Science and Business Media LLC
Date: 12-2012
Publisher: Elsevier BV
Date: 12-2021
Publisher: FapUNIFESP (SciELO)
Date: 12-2008
DOI: 10.1590/S1983-41952008000400001
Abstract: Com a teoria da confiabilidade avaliam-se as duas formulações apresentadas pela norma de projeto de estruturas de concreto NBR 6118:2003 para a estimativa da abertura de fissuras em tubos de concreto armado. Os métodos de confiabilidade FOSM (método de primeira ordem e segundo momento) e o método de simulação de Monte Carlo com amostragem por importância são utilizados. Uma primeira análise de confiabilidade revela as variáveis de projeto com maior contribuição nas probabilidades de falha. Uma análise paramétrica é realizada nestas variáveis, de maneira a identificar a influência destas na confiabilidade dos tubos. O estudo mostra que as formulações da NBR 6118:2003 levam a valores não uniformes para o índice de confiabilidade, para um mesmo fator de segurança. Isto significa que o coeficiente de segurança unitário especificado em norma para o estado limite de fissuração não reflete a incerteza nos parâmetros de resistência do tubo.
Publisher: Wiley
Date: 21-03-1970
DOI: 10.1002/NME.6781
Abstract: Stress‐constrained topology optimization requires techniques for handling thousands to millions of stress constraints. This work presents a comprehensive numerical study comparing local and global stress constraint strategies in topology optimization. Four local and four global solution strategies are presented and investigated. The local strategies are based on either the augmented Lagrangian or the pure exterior penalty method, whereas the global strategies are based on the P ‐mean aggregation function. Extensive parametric studies are carried out on the L‐shaped design problem to identify the most promising parameters for each solution strategy. It is found that (1) the local strategies are less sensitive to the continuation procedure employed in standard density‐based topology optimization, allowing achievement of better quality results using less iterations when compared with the global strategies (2) the global strategies become competitive when P values larger than 100 are employed, but for this to be possible a very slow continuation procedure should be used (3) the local strategies based on the augmented Lagrangian method provide the best compromise between computational cost and performance, being able to achieve optimized topologies at the level of a pure P ‐continuation global strategy with , but using less iterations.
Publisher: Springer Science and Business Media LLC
Date: 12-2010
Publisher: FapUNIFESP (SciELO)
Date: 2021
DOI: 10.1590/S1983-41952021000400015
Abstract: Abstract It is well known that highway bridges are subjected to fatigue as they work under live loads with different frequencies and litude. The safety level for fatigue required by Brazilian codes is still unknown, especially for prestressed concrete girders. Also, current studies on fatigue reliability of bridges only evaluate bending. This work assesses the fatigue safety level provided by Brazilian design standards for a concrete highway bridge, using weigh-in-motion (WIM) data of an important federal Brazilian highway, BR-381 (Fernão Dias Highway). The Palmgren-Miner rule is considered to evaluate the service life and reliability indexes, from the fatigue point of view, of prestressed girders designed according to Brazilian codes. Using limited and complete prestressing levels, different traffic volumes are considered. It is found that the fatigue safety levels of longitudinal and transverse reinforcements are larger than the ones recommended by the international literature.
Publisher: Elsevier BV
Date: 04-2008
Publisher: Springer Science and Business Media LLC
Date: 28-11-2017
Publisher: Wiley
Date: 09-10-2020
DOI: 10.1002/NME.6548
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 09-2013
Publisher: Elsevier BV
Date: 04-2016
Publisher: American Society of Civil Engineers (ASCE)
Date: 2022
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 12-2020
Publisher: FapUNIFESP (SciELO)
Date: 2024
DOI: 10.1590/S1983-41952024000200009
Abstract: Abstract Design loads for parking garages should be reviewed every few years due to changes in fleet characteristics and the impact of design loads on carbon emissions by the built environment. Specifically for Brazil, the authors are unaware of existing studies to justify the design values and corresponding exceedance probabilities stated in NBR 6120:2019 - Design Loads for Structures. In this paper, a simplified probabilistic model for live loads in parking garages is presented. A set of updated statistics characterizing the gross curb weight of the fleet in circulation was obtained based on technical specifications and sales reports between 2003 and 2022. These statistics and the probabilistic load model are employed to derive the equivalent uniform design load corresponding to a 30% probability of being exceeded in 50 years, according to the definition stated in NBR 6120:2019 and NBR 8681:2003. The results provide support for a significant reduction of the current design load for light-duty vehicle parking garages, from the current 3.0 kN/m2 to at least 2.5 kN/m2. Such a reduction has a significant impact on new building construction costs and carbon emissions and would not compromise the structural safety of parking garages built in Brazil.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 2012
Publisher: FapUNIFESP (SciELO)
Date: 10-2011
DOI: 10.1590/S1983-41952011000400009
Abstract: Este artigo apresenta um estudo da (não-)conformidade dos concretos estruturais produzidos no Brasil, bem como do impacto da não-conformidade na redução da confiabilidade de pilares curtos submetidos a compressão simples. Esta investigação tem como base ensaios de resistência de mais de cinco mil corpos-de-prova de diferentes localidades do Brasil. Estes ensaios mostram que parte significativa dos concretos atualmente produzidos no Brasil não atingem a resistência característica (fck) especificada em projeto. Como resultado, estes concretos deveriam ser considerados não-conformes, e medidas de mitigação deveriam ser aplicadas. O trabalho investiga ainda o impacto da não-conformidade dos concretos produzidos no Brasil na confiabilidade de pilares curtos de concreto armado submetidos a compressão simples, quando medidas de reforço e recuperação não são adotadas. Em concreto armado, pilares curtos são os elementos estruturais cuja resistência mais diretamente depende da resistência à compressão do concreto. Uma consequência da não-conformidade dos concretos é que a equação teórica de norma, que relaciona a resistência média com o valor característico especificado em projeto, não pode ser utilizada na análise de confiabilidade. Utilizando equação equivalente, determinada a partir dos resultados experimentais, verifica-se uma redução significativa da confiabilidade dos pilares curtos em função da não-conformidade dos concretos. Estes resultados reforçam a necessidade de um controle rigoroso no recebimento do concreto, bem como na fiscalização das medidas de mitigação no caso dos concretos não-conformes.
Publisher: FapUNIFESP (SciELO)
Date: 12-2019
DOI: 10.1590/S1983-41952019000600004
Abstract: Abstract This paper presents a reliability-based calibration of partial safety factors for Brazilian codes used in the design of concrete structures. The work is based on reliability theory, which allows an explicit representation of the uncertainties involved in terms of resistances and loads. Regarding the resistances, this study considers beams with concrete of five classes (C20, C30, C40, C50 and C60), three ratios between base and effective depth (0.25, 0.50 and 0.75), three longitudinal reinforcement ratios (ρmin, 0.5% and ρmax) and three transverse reinforcement ratios ( A s s m i n, 5 . A s s m i n and A s s m a x). In terms of loads, this work considers seven ratios between live loads and permanent loads (qn/gn), and seven ratios between wind loads and permanent loads (wn/gn). The study also adopts a single value for the target reliability index (βtarget = 3.0). Results show that the optimized set of partial safety factors leads to more uniform reliability for different design situations and load combinations.
Publisher: Elsevier BV
Date: 10-2009
Publisher: Informa UK Limited
Date: 11-12-2017
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 04-2020
Publisher: Elsevier BV
Date: 04-2011
Publisher: Elsevier BV
Date: 04-2015
Publisher: FapUNIFESP (SciELO)
Date: 2023
DOI: 10.1590/S1983-41952023000300006
Abstract: Abstract Size effects are known to be relevant in the shear transfer mechanisms of quasi-brittle materials like concrete. Bažant proposed an asymptotic approximation between plasticity theory and Linear Elastic Fracture Mechanics (LEFM), showing a proportionality of concrete nominal resistance with d - 1 / 2, where d is beam depth. Recently, the long-standing shear transfer mechanism expressions of ACI 318:2014 have been updated (ACI 318:2019), with introduction of a size effect factor. In Brazil, recent publications identified non-conservative trends in predictions of ABNT NBR 6118:2014 for larger beam depths yet, the Brazilian code never considered size effects because they are suppressed by transverse reinforcement. Considering this background, in this manuscript we make a comprehensive analysis of NBR 6118:2014 shear strength predictions using as a reference the papers of ACI-ASCE DatStb 445-D database. The results exhibit strong tendencies in the model error regarding longitudinal reinforcement and effective depth for beams without transversal reinforcement. A two-step analysis is made herein to describe model errors: first, a nonlinear regression for longitudinal reinforcement is made second, a linear regression is made for size effect. The reliability analysis corroborates that model error may be reduced by introducing size effect and longitudinal reinforcement factors. Next, for beams with transversal reinforcement, smoother tendencies regarding beam depth are noted, indicating a size effect suppression for the beams depths available in the database. However, as the analysis shows that the higher beam depths concentrate most of the results with unconservative model errors, further studies are necessary to accurately describe how transversal reinforcement suppress the size effect.
Publisher: Springer Science and Business Media LLC
Date: 2012
Publisher: FapUNIFESP (SciELO)
Date: 09-2008
DOI: 10.1590/S1983-41952008000300001
Abstract: Este artigo apresenta uma investigação da segurança de pilares mistos preenchidos de seção circular, dimensionados segundo a norma brasileira NBR 8800:2008. Esta investigação é feita com base na comparação de previsões normativas com a resistência obtida em 32 ensaios experimentais, bem como na comparação com as normas americana e européia correspondentes. O erro de modelo das equações teóricas de resistência destas normas é determinado. Uma análise de covariância é realizada para verificar tendências das equações de resistência. O estudo mostra que o modelo de resistência utilizado na norma brasileira é compatível com as normas estrangeiras, em termos de tendenciosidade e variância. O estudo revela uma margem de segurança adicional da ordem de 10% na NBR8800, quando removidos os coeficientes parciais de segurança. Uma análise de confiabilidade é realizada para 3888 configurações de pilar, resultando em índices de confiabilidade que refletem a segurança do universo de pilares cobertos pelas normas. O estudo mostra que a norma brasileira apresenta índices de confiabilidade compatíveis com as normas estrangeiras.
Publisher: Springer Science and Business Media LLC
Date: 30-11-2014
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2021
Publisher: Elsevier BV
Date: 04-2012
Publisher: Springer Science and Business Media LLC
Date: 02-05-2015
Publisher: Thomas Telford Ltd.
Date: 08-2018
Abstract: Structural design optimization usually aims to extract more function from less material. This can result in more failure modes designed against their limits, thus reducing safety. The compromise between cost reduction and safety is particularly relevant for geotechnical structures, as they are subject to significant scatter and uncertainties in their properties. In this context, this paper presents an application of Reliability-Based Design Optimization (RBDO) for the problem of geosynthetic-reinforced soil retaining walls. Design variables include the mean strength of the geosynthetic, spacing between reinforcements, and the length of the geosynthetic. Random variables include soil angle of friction, soil unit weight, the strength of the geosynthetic and the friction angle between the reinforcement and soil mass. The solution procedure proposed herein combines the ant colony optimization (ACO) algorithm with the First Order Reliability Method (FORM) algorithm, which results in nested optimization loops. Results show that significant savings can be achieved in structural design without hindering structural safety.
Publisher: Elsevier BV
Date: 11-2023
Publisher: American Society of Civil Engineers
Date: 27-06-2014
Publisher: FapUNIFESP (SciELO)
Date: 10-2015
Publisher: Elsevier BV
Date: 09-2020
Publisher: Begell House
Date: 2012
Publisher: American Society of Civil Engineers
Date: 27-06-2014
Publisher: Elsevier BV
Date: 07-2011
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 2004
Publisher: ASME International
Date: 20-04-2015
DOI: 10.1115/1.4029741
Abstract: The Neumann series is a well-known technique to aid the solution of uncertainty propagation problems. However, convergence of the Neumann series can be very slow, often making its use highly inefficient. In this article, a fast convergence parameter (λ) convergence parameter is introduced, which yields accurate and efficient Monte Carlo–Neumann (MC-N) solutions of linear stochastic systems using first-order Neumann expansions. The λ convergence parameter is found as a solution to the distance minimization problem, for an approximation of the inverse of the system matrix using the Neumann series. The method presented herein is called Monte Carlo–Neumann with λ convergence, or simply the MC-N λ method. The accuracy and efficiency of the MC-N λ method are demonstrated in application to stochastic beam-bending problems.
Publisher: FapUNIFESP (SciELO)
Date: 2020
Publisher: Elsevier BV
Date: 10-2013
Publisher: Elsevier BV
Date: 12-2017
Publisher: FapUNIFESP (SciELO)
Date: 04-2020
DOI: 10.1590/S1983-41952020000200010
Abstract: Abstract Nowadays it is known that it is important to study the safety of structures to avoid tragic accidents or economic losses. The most widely used method in the world to evaluate the safety of structures is structural reliability. The reliability index of prestressed precast beams of bridges designed using Brazilian standards (NBR6118 and NBR7188) is not known. This work evaluates the annual reliability indexes of a prestressed precast beam bridge at the serviceability limit state (SLS) projected using the Brazilian standard and compares it with results from the literature. The studied bridge has 33.5 meters of span, is simply supported, constituted by five precast concrete beams with U section. The reliability analysis was carried out using two methods for the four limit state equations: First Order Mean Value (FOMV) and First Order Reliability Method (FORM). Sensitivity analyzes were performed to consider both the relative contribution of these variables and the effect of their distributions on the annual reliability indexes for SLS. It was verified that the effect of load trains and the allowable stress significantly reduce the reliability index obtained for Brazilian standard. The service limit state equations are particularly sensitive to load trains, allowable stress and prestress losses, as well as their respective distributions.
Publisher: IOP Publishing
Date: 06-2010
Publisher: Wiley
Date: 28-03-2019
DOI: 10.1002/NME.6061
Publisher: Springer Science and Business Media LLC
Date: 12-03-2019
Publisher: Springer Science and Business Media LLC
Date: 17-05-2019
Publisher: Springer Science and Business Media LLC
Date: 08-02-2022
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 11-2023
Publisher: Informa UK Limited
Date: 24-05-2021
Publisher: Springer International Publishing
Date: 30-09-2017
Publisher: Elsevier BV
Date: 02-2019
Publisher: Springer International Publishing
Date: 2013
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2016
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 2020
Publisher: Elsevier BV
Date: 07-2022
Publisher: Elsevier BV
Date: 04-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2013
Publisher: FapUNIFESP (SciELO)
Date: 2020
Publisher: FapUNIFESP (SciELO)
Date: 2023
DOI: 10.1590/S1983-41952023000500003
Abstract: Abstract Most papers in the literature address reliability analysis of isolated elements, like beams and columns. However, symmetry and regularity are often exploited in the construction of regular RC frames, resulting in the same or similar designs for all columns of a floor or all beams of a building. This leads to significant differences in member reliability, due to different axial load to bending moment ratios, in different parts of the structure. Moreover, load effects increase, and symmetry is lost under in idual support settlements. In this scenario, reliability analyses are performed, for an intact 4-floors and 3-spans RC frame and considering different settlement conditions. Monte Carlo simulation is performed, considering uncertainties in dead and live loading, and steel and concrete strengths. The results show that a settlement of 10 mm, corresponding to an angular distortion of 1/500, reduced the average reliability of the frame by only 14%, just the same, it reduced the reliability index of several cross-sections of the beams to up to 2.40, value lower than that recommended in the Model Code 2010. It is concluded that the methodology used in this work presents an important tool for the analysis of events not foreseen in the design, supporting the decision making about the need for intervention in the structures.
Publisher: FapUNIFESP (SciELO)
Date: 04-2017
DOI: 10.1590/S1983-41952017000200003
Abstract: Abstract The Brazilian design code for composite buildings (NBR8800) has never been subject to a reliability-based calibration of the partial factors used in design. As a consequence, the level of structural safety achieved by using these factors is, in general, unknown. This paper presents a study of the reliability of partially encased steel-concrete composite columns, subject to compression and bending. Literature statistics are used to quantify uncertainty in strength of structural materials and in loads. Reliability indexes are evaluated, via FORM, for two ratios between dead and live loads, and for some values of load eccentricity. It was found that larger load eccentricity leads to a reduction in reliability indexes. These values are larger than minimum values recommended in international design codes hence one concludes that design of such columns using NBR8800 leads to acceptable safety levels.
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2016
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 2016
Publisher: FapUNIFESP (SciELO)
Date: 2021
DOI: 10.1590/S1983-41952021000100012
Abstract: Abstract This article presents an analysis of NBR6118:2014 models used to determine the one-way shear strength in reinforced concrete members without transversal reinforcement. The study compares model predictions with 751 experimental results, taken from the 2015 ACI-DAfStb database and from Quach. Model errors are quantified. Mean values observed are around unity, indicating models with no bias, but coefficients of variation are large. Model error trends are identified with respect to cross-section depth and longitudinal reinforcement rate. In elements with low rate of longitudinal reinforcement and/or large cross-section depths, the normative models provide results with low safety. This shows the need for revision of the normative models. By means of non-linear regression analysis, two correction terms are proposed to consider the longitudinal reinforcement rate and the size effect (decrease in shear strength with increase in section depth). With the proposed corrections, the observed trends are eliminated, and the design equation becomes more accurate with respect to cross-section shear.
Publisher: Elsevier BV
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 06-2010
Publisher: Elsevier BV
Date: 10-2012
Publisher: Begell House
Date: 2013
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 2018
Publisher: FapUNIFESP (SciELO)
Date: 2023
DOI: 10.1590/S1983-41952023000400001
Abstract: abstract: Updating the basic wind speed map of NBR 6123 –-Wind loading on buildings – is one of the duties of the committee responsible for the revision of this code. Traditionally such maps are elaborated by means of extreme value wind speed data collected at meteorological stations, use of statistical methods for data characterization, and application of mathematical regression to elaborate the territorial maps. However, the spatial distribution of the atmospheric phenomena responsible for strong winds cannot be disregarded. This work presents a proposal for a new wind speed map for NBR 6123 combining a climatological approach and wind speed data recently compiled from hundreds of meteorological stations. A climatological wind map was first produced considering the phenomena which cause strong winds, and used as a basis to draw the isopleths of the basic wind speed map, considering the measured wind speed data. The resulting map shows basic wind speeds ranging from 30 to 48m/s.
Publisher: FapUNIFESP (SciELO)
Date: 08-2017
DOI: 10.1590/S1983-41952017000400008
Abstract: ABSTRACT This paper presents a new evaluation of the strength compliance of concretes produced in Brazil. It is based on experimental results of over twenty-seven thousand concrete s les from different parts of the country. Results show that a significant part of Brazilian concrete do not reach the characteristic strength (fck) specified in design, and the percentage of nonconforming s les tend to be higher than 5%. This study also reveals the concrete produced in the South and Midwest regions have less variability than the ones produced in the other regions of the country. These results emphasize the importance of a rigorous control in manufacturing and reception of concretes in order to reduce the nonconforming cases.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 06-0001
Publisher: FapUNIFESP (SciELO)
Date: 2022
DOI: 10.1590/S1983-41952022000500001
Abstract: abstract: Performance and safety of geotechnical structures are affected by uncertainties. Yet, the design of dams is nowadays still made using deterministic methods and design codes. Dam optimization in a deterministic setting may lead to compromised safety margins. In this setting, Reliability-Based Design Optimization (RBDO) appears as an alternative, allowing one to optimize dam performance, but respecting specified reliability constraints. In this paper, we employ an efficient and accurate Single-Loop Approach (SLA) in the RBDO of a concrete dam. Considering dam equilibrium reliability constraints, we find the optimal dam base and optimal placement of drainage galleries, for different dam heights and different target reliability index ( β T). We show how the governing failure mode changes for each optimal solution: for large β T, sliding limit state is the active constraint for smaller β T values, the eccentricity limit state function is found to be the active constraint for the optimum dam. We also investigate how the importance of random parameters change for each optimum solution: for large β T and failure controlled by sliding, the cohesion and friction angle along dam base interface with foundation rock are the most relevant uncertain parameters for dam equilibrium. For smaller β T with failure controlled by eccentricity, the more relevant uncertain geotechnical parameters are the base length of the dam, the specific weight of concrete, and the coefficient of drainage gallery inefficiency.
Publisher: ASME International
Date: 17-06-2013
DOI: 10.1115/1.4023938
Abstract: In this paper, the Galerkin method is used to obtain numerical solutions to two-dimensional steady-state reaction-diffusion problems. Uncertainties in reaction and diffusion coefficients are modeled using parameterized stochastic processes. A stochastic version of the Lax–Milgram lemma is used in order to guarantee existence and uniqueness of the theoretical solutions. The space of approximate solutions is constructed by tensor product between finite dimensional deterministic functional spaces and spaces generated by chaos polynomials, derived from the Askey–Wiener scheme. Performance of the developed Galerkin scheme is evaluated by comparing first and second order moments and probability histograms obtained from approximate solutions with the corresponding estimates obtained via Monte Carlo simulation. Results for three ex le problems show very fast convergence of the approximate Galerkin solutions. Results also show that complete probability densities (histograms) of the responses are correctly approximated by the developed Galerkin basis.
Publisher: ASME International
Date: 07-01-2019
DOI: 10.1115/1.4042015
Abstract: Manufacturing tolerances and other uncertainties may play an important role in the performance of parallel manipulators since they can affect the distance to a singular configuration. Motion planning strategies for parallel manipulators under uncertainty require decision making approaches for classifying reliable regions within the workspace. In this paper, we address fail free and reliable motion planning for parallel manipulators. Failure is related to parallel kinematic singularities in the motion equations or to ill-conditioning of the Jacobian matrices. Monte Carlo algorithm is employed to compute failure probabilities for a dense grid of manipulator workspace configurations. The inverse condition number of the Jacobian matrix is used to compute the distance between each configuration and a singularity. For supporting motion planning strategies, not only failure maps are constructed but also reliable and failure-free workspaces are obtained. On the one hand, the reliable workspace is obtained by minimizing the failure probabilities subject to a minimal workspace area. Differently, a failure-free workspace is found by maximizing the workspace area subject to a probability of failure equal to zero. A 3RRR manipulator is used as a case study. For this case study, the usage of the reliable strategy can be useful for robustifying motion planning algorithm without a significant reduction of the reliable regions within the workspace.
Publisher: Informa UK Limited
Date: 23-02-2016
Publisher: FapUNIFESP (SciELO)
Date: 07-2013
Publisher: Springer Science and Business Media LLC
Date: 06-2008
Publisher: Springer Science and Business Media LLC
Date: 06-05-2021
Publisher: Elsevier BV
Date: 2005
Publisher: Elsevier BV
Date: 03-2018
Publisher: Begell House
Date: 2013
Publisher: FapUNIFESP (SciELO)
Date: 10-2014
DOI: 10.1590/S1983-41952014000500002
Abstract: This paper presents an investigation on the safety of structural elements submitted to pure bending, produced in reinforced concrete, in steel and steel-concrete composites, and designed according to Brazilian codes NBR8681:2003, NBR6118:2007 and NBR8800:2008. The study allows a comparison of the relative safety of beams produced with these materials and designed using these codes. Comparative studies between the performances of different materials are difficult to find in the published literature. The present study shows that reliability indexes for reinforced concrete beams are satisfactory however, results for steel beams are below limit values established in international design standards. Reliability indexes found herein for steel-concrete composite beams are intermediate to concrete and steel beams.
Publisher: ASME International
Date: 23-04-2021
DOI: 10.1115/1.4050159
Abstract: This contribution proposes a strategy for performing fuzzy analysis of linear static systems applying α-level optimization. In order to decrease numerical costs, full system analyses are replaced by a reduced order model that projects the equilibrium equations to a small-dimensional space. The basis associated with the reduced order model is constructed by means of a single analysis of the system plus a sensitivity analysis. This reduced basis is enriched as the α-level optimization strategy progresses in order to protect the quality of the approximations provided by the reduced order model. A numerical ex le shows that with the proposed strategy, it is possible to produce an accurate estimate of the membership function of the response of the system with a limited number of full system analyses.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Springer Science and Business Media LLC
Date: 10-03-2022
DOI: 10.1007/S42452-022-04980-7
Abstract: In this study, we present a numerical investigation of the direct coupling between the deterministic GeoStudio package (Seepage/W and Slope/W software) and the StRAnD reliability package for normal operating conditions of an existing old earth dam over time. Direct coupling avoids errors associated to point estimate methods and to using response surface surrogates. One relevant feature of the study is the use of realistic pore water pressures for each equilibrium analysis, accomplished by considering a long-term steady-state analysis as an initial condition, followed by four years of equilibrium analysis, before each transient seepage analysis. All reliability analysis were performed using the first-order reliability method. The most important random parameters found in sensitivity analyses are four dam body parameters (saturated hydraulic conductivity, k s specific weight, γ effective cohesion, c ′ and friction angle, ϕ ′) and two filter parameters ( k s and ϕ ′). A range of values of the relationship between the reliability index ( β ) and the factor of safety ( FS ) was found for all probabilistic and deterministic results. Finally, a large difference in terms of critical deterministic and probabilistic slip surfaces is identified for the same time of analysis. Realistic pore water pressures used in dam equilibrium analysis, by considering random seepage analysis in previous 5 to 30 days. Direct coupling of deterministic and reliability softwares avoids errors associated to point estimate and response surface surrogate methods. Existing old earth dam studied in Normal Operating Condition. For same analysis time, large differences are observed between critical deterministic and probabilistic slip surfaces.
Publisher: Elsevier BV
Date: 10-2022
Publisher: Informa UK Limited
Date: 13-09-2022
Publisher: FapUNIFESP (SciELO)
Date: 2022
DOI: 10.1590/S1983-41952022000200007
Abstract: abstract: The design of reinforced concrete (RC) frames is made on a member-by-member basis. Similarly, in the literature, the reliability of RC beams and columns is often studied in isolation from the rest of the structure. Yet, in the construction of regular frames, symmetry and regularity are often exploited, resulting in the same design for each element type. This is despite of different load effects on different parts of the structure, which leads to significant variations in the failure probability of the elements. Hence, in this paper, we investigate the reliability of members and the distribution of load effects in regular RC frame buildings, considering intact and column loss cases, where symmetry is lost. Results show that the ratios of normal-to-bending loads change significantly along building height, and this has a significant impact on reliability of in idual columns.
Publisher: Elsevier BV
Date: 07-2023
Publisher: Elsevier BV
Date: 06-2019
Publisher: Springer International Publishing
Date: 19-07-2018
Publisher: FapUNIFESP (SciELO)
Date: 2019
Publisher: FapUNIFESP (SciELO)
Date: 02-2012
DOI: 10.1590/S1983-41952012000100007
Abstract: Brazilian design code ABNT NBR6118:2003 - Design of Concrete Structures - Procedures - [1] proposes the use of simplified models for the consideration of non-linear material behavior in the evaluation of horizontal displacements in buildings. These models penalize stiffness of columns and beams, representing the effects of concrete cracking and avoiding costly physical non-linear analyses. The objectives of the present paper are to investigate the accuracy and uncertainty of these simplified models, as well as to evaluate the reliabilities of structures designed following ABNT NBR6118:2003[1& ] in the service limit state for horizontal displacements. Model error statistics are obtained from 42 representative plane frames. The reliabilities of three typical (4, 8 and 12 floor) buildings are evaluated, using the simplified models and a rigorous, physical and geometrical non-linear analysis. Results show that the 70/70 (column/beam stiffness reduction) model is more accurate and less conservative than the 80/40 model. Results also show that ABNT NBR6118:2003 [1] design criteria for horizontal displacement limit states (masonry damage according to ACI 435.3R-68(1984) [10]) are conservative, and result in reliability indexes which are larger than those recommended in EUROCODE [2] for irreversible service limit states.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 07-2017
Publisher: Elsevier BV
Date: 10-2013
Publisher: American Society of Civil Engineers (ASCE)
Date: 02-2018
Publisher: Elsevier
Date: 2003
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 09-2013
No related grants have been discovered for André Beck.