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Letteratura scientifica selezionata sul tema "Columns, Concrete Testing Mathematical models"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 30 gennaio 2023

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Articoli di riviste sul tema "Columns, Concrete Testing Mathematical models"

Khan, Kaffayatullah, Mudassir Iqbal, Muhammad Raheel, Muhammad Nasir Amin, Anas Abdulalim Alabdullah, Abdullah M. Abu-Arab e Fazal E. Jalal. "Prediction of Axial Capacity of Concrete Filled Steel Tubes Using Gene Expression Programming". Materials 15, n. 19 (7 ottobre 2022): 6969. http://dx.doi.org/10.3390/ma15196969.

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The safety and economy of an infrastructure project depends on the material and design equations used to simulate the performance of a particular member. A variety of materials can be used in conjunction to achieve a composite action, such as a hollow steel section filled with concrete, which can be successfully utilized in the form of an axially loaded member. This study aims to model the ultimate compressive strength (Pu) of concrete-filled hollow steel sections (CFSS) by formulating a mathematical expression using gene expression programming (GEP). A total of 149 datapoints were obtained from the literature, considering ten input parameters, including the outer diameter of steel tube (D), wall thickness of steel tube, compressive strength of concrete (fc’), elastic modulus of concrete (Ec), yield strength of steel (fv), elastic modulus of steel (Es), length of the column (L), confinement factor (ζ), ratio of D to thickness of column, and the ratio of length to D of column. The performance of the developed models was assessed using coefficient of regression R2, root mean squared error RMSE, mean absolute error MAE and comparison of regression slopes. It was found that the optimal GEP Model T3, having number of chromosomes Nc = 100, head size Hs = 8 and number of genes Ng = 3, outperformed all the other models. For this particular model, R2overall equaled 0.99, RMSE values were 133.4 and 162.2, and MAE = 92.4 and 108.7, for training (TR) and testing (TS) phases, respectively. Similarly, the comparison of regression slopes analysis revealed that the Model T3 exhibited the highest R2 of 0.99 with m = 1, in both the TR and TS stages, respectively. Finally, parametric analysis showed that the Pu of composite steel columns increased linearly with the value of D, t and fy.

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Rezvani Sharif, Mostafa, e Seyed Mohammad Reza Sadri Tabaei Zavareh. "Numerical analysis of the shear strength of circular reinforced concrete columns subjected to cyclic lateral loads using linear genetic programming". Engineering Computations 37, n. 7 (18 marzo 2020): 2517–37. http://dx.doi.org/10.1108/ec-10-2018-0453.

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Purpose The shear strength of reinforced concrete (RC) columns under cyclic lateral loading is a crucial concern, particularly, in the seismic design of RC structures. Considering the costly procedure of testing methods for measuring the real value of the shear strength factor and the existence of several parameters impacting the system behavior, numerical modeling techniques have been very much appreciated by engineers and researchers. This study aims to propose a new model for estimation of the shear strength of cyclically loaded circular RC columns through a robust computational intelligence approach, namely, linear genetic programming (LGP). Design/methodology/approach LGP is a data-driven self-adaptive algorithm recently used for classification, pattern recognition and numerical modeling of engineering problems. A reliable database consisting of 64 experimental data is collected for the development of shear strength LGP models here. The obtained models are evaluated from both engineering and accuracy perspectives by means of several indicators and supplementary studies and the optimal model is presented for further purposes. Additionally, the capability of LGP is examined to be used as an alternative approach for the numerical analysis of engineering problems. Findings A new predictive model is proposed for the estimation of the shear strength of cyclically loaded circular RC columns using the LGP approach. To demonstrate the capability of the proposed model, the analysis results are compared to those obtained by some well-known models recommended in the existing literature. The results confirm the potential of the LGP approach for numerical analysis of engineering problems in addition to the fact that the obtained LGP model outperforms existing models in estimation and predictability. Originality/value This paper mainly represents the capability of the LGP approach as a robust alternative approach among existing analytical and numerical methods for modeling and analysis of relevant engineering approximation and estimation problems. The authors are confident that the shear strength model proposed can be used for design and pre-design aims. The authors also declare that they have no conflict of interest.

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Rashedi, Ahmad, Riadh Marzouki, Ali Raza, Khawar Ali, Niyi Gideon Olaiya e Mayandi Kalimuthu. "Glass FRP-Reinforced Geopolymer Based Columns Comprising Hybrid Fibres: Testing and FEA Modelling". Polymers 14, n. 2 (13 gennaio 2022): 324. http://dx.doi.org/10.3390/polym14020324.

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This study seeks to evaluate the effectiveness of glass-FRP-reinforced geopolymer concrete columns integrating hybrid fibres (GFGC columns) and steel bar-reinforced geopolymer concrete columns incorporating hybrid fibres (SFGC columns) under eccentric and concentric loadings. Steel fibre (SF) and polypropylene fibres (PF) are two types of fibres that are mixed into hybrid fibre-reinforced geopolymer concrete (HFRGC). Eighteen circular concrete columns with a cross-section of 300 mm × 1200 mm were cast and examined under axial loading up to failure. Nine columns were cast with glass-FRP rebars, whereas the other nine were cast with steel rebars. Using ABAQUS, a nonlinear finite element model was established for the GFGC and SFGC columns. The HFRGC material was modelled using a simplified concrete damage plasticity model, whereas the glass-FRP material was simulated as a linear elastic material. It was observed that GFGC columns had up to 20% lower axial strength (AST) and up to 24% higher ductility indices than SFGC columns. The failure modes of both GFGC and SFGC columns were analogous. Both GFGC and SFGC columns revealed the same effect of eccentricity in the form of a decline in AST. A novel statistical model was suggested for predicting the AST of GFGC columns. The outcomes of the experiments, finite element simulations, and theoretical results show that the models can accurately determine the AST of GFGC columns.

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Campione, Giuseppe. "The effects of fibers on the confinement models for concrete columns". Canadian Journal of Civil Engineering 29, n. 5 (1 ottobre 2002): 742–50. http://dx.doi.org/10.1139/l02-066.

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A mathematical model is developed to express the stressstrain relationships in compression of fiber-reinforced concrete (FRC) columns for both normal- and high-strength concrete, with and without conventional steel reinforcement. This model allows one to determine the maximum strength and strain capacity by determining the effective concrete core of the confining devices at rupture. Analytical expressions are also given for the ultimate load corresponding to the complete formation of the concrete failure plane. The proposed model incorporates the most relevant parameters of confinement, i.e., type of confinement, volumetric ratio, spacing, yielding strength, shape of the member cross section, type of fiber (length, diameter, shape), and fiber volume. The model has been verified against data obtained from concentric compressive tests on concrete specimens reinforced with transverse steel and fibers.Key words: high-strength concrete, fiber-reinforced concrete, lateral reinforcement, stressstrain curves.

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Lie, T. T., e D. C. Stringer. "Calculation of the fire resistance of steel hollow structural section columns filled with plain concrete". Canadian Journal of Civil Engineering 21, n. 3 (1 giugno 1994): 382–85. http://dx.doi.org/10.1139/l94-041.

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Experimental studies were conducted to determine the fire resistance of circular and square hollow structural section columns filled with plain concrete. Mathematical models were developed and used to investigate the influence of important parameters that determine the fire resistance of these columns. The experimental and parametric studies provide information for the development of formulas for the calculation of the fire resistance of circular and square concentrically loaded columns filled with plain carbonate or siliceous aggregate concrete. Such formulas are suitable for incorporation into building codes. Key words: calculation, fire resistance, columns, concrete-filled, steel, hollow structural sections.

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Isleem, Haytham F., Muhammad Abid, Wesam Salah Alaloul, Muhammad Kamal Shah, Shayan Zeb, Muhammad Ali Musarat, Muhammad Faisal Javed, Fahid Aslam e Hisham Alabduljabbar. "Axial Compressive Strength Models of Eccentrically-Loaded Rectangular Reinforced Concrete Columns Confined with FRP". Materials 14, n. 13 (23 giugno 2021): 3498. http://dx.doi.org/10.3390/ma14133498.

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The majority of experimental and analytical studies on fiber-reinforced polymer (FRP) confined concrete has largely concentrated on plain (unreinforced) small-scale concrete columns, on which the efficiency of strengthening is much higher compared with large-scale columns. Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric compression) are the most common structural elements used in practice, research on eccentrically-loaded FRP-confined rectangular RC columns has been much more limited. More specifically, the limited research has generally been concerned with small-scale RC columns, and hence, the proposed eccentric-loading stress-strain models were mainly based on the existing concentric-loading models of FRP-confined concrete columns of small scale. In the light of such demand to date, this paper is aimed at developing a mathematical model to better predict the strength of FRP-confined rectangular RC columns. The strain distribution of FRP around the circumference of the rectangular sections was investigated to propose equations for the actual rupture strain of FRP wrapped in the horizontal and vertical directions. The model was accomplished using 230 results of 155 tested specimens compiled from 19 studies available in the technical literature. The test database covers an unconfined concrete strength ranging between 9.9 and 73.1 MPa, and section’s dimension ranging from 100–300 mm and 125–435 mm for the short and long sides, respectively. Other test parameters, such as aspect ratio, corner radius, internal hoop steel reinforcement, FRP wrapping layout, and number of FRP wraps were all considered in the model. The performance of the model shows a very good correlation with the test results.

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Abdallah, Wafaa, Jacqueline Saliba, Ziubir-Mehdi Sbartaï, Marwan Sadek, Fadi Hage Chehade e S. Mohammed ElAchachi. "Reliability analysis of non-destructive testing models within a probabilistic approach". MATEC Web of Conferences 281 (2019): 04003. http://dx.doi.org/10.1051/matecconf/201928104003.

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The diagnosis of reinforced concrete is essential to detect the degradation and thus maintain the structural performance of civil engineering structures. This paper aims to establish a mathematical relationship between the ultrasonic pulse velocity UPV (considered as an observable variable) and two concrete properties indicators (compressive strength fc and water content W) within a probabilistic framework. Synthetic simulations are proposed to derive a conversion model between the statistical properties of the output and the input parameters for a reinforced concrete structure by taking into account spatial variability of concrete.

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Štefan, Radek, e Jaroslav Procházka. "Modelling of Hygro-Thermal Processes in Steel-Concrete Composite Columns Exposed to High Temperatures". Solid State Phenomena 249 (aprile 2016): 246–52. http://dx.doi.org/10.4028/www.scientific.net/ssp.249.246.

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In the paper, transport processes in heated steel-concrete composite columns are analyzed. Mathematical models of heat transfer and coupled heat and mass transfer are described with respect to the specific parameters of composite structures. Numerical formulations of the models are implemented into MATLAB environment and the applicability of the models is depicted on an illustrative example. It is shown that not only the thermal distribution, but also the moisture migration as well as the pore pressure built-up are of particular interest.

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Anand, Praveen, e Ajay Kumar Sinha. "Effect of Reinforced Concrete Jacketing on Axial Load Capacity of Reinforced Concrete Column". Civil Engineering Journal 6, n. 7 (1 luglio 2020): 1266–72. http://dx.doi.org/10.28991/cej-2020-03091546.

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Whenever a member of a structure becomes structurally deficient, it becomes vulnerable to the existing load and for the additional loads that it may be subjected to in the coming future. Since columns are the most important structural element, the structural retrofit of columns, relative to other structural elements is of prime importance. This study intends to investigate the performance and behaviour of an RC column jacketed with Reinforced Concrete columns under axial loads. The objective of this paper is to find out the efficiency of RC jacket in enhancing the strength of an existing RC column. A mathematical design based upon Indian Standards codes has been designed to identify the behaviour of jacketed RC columns. This has been followed by a finite element based numerical simulation using the same material properties as used in the process of designing. The simulation has been done in ABAQUS software with appropriate contact modelling. The analytical model considers that there is no bond slippage between the existing and new concrete surface i.e. the bond between the existing and new concrete is assumed to be perfect. This perfect bond between the surfaces has been modelled by using appropriate constraints in ABAQUS software. The finite element models show fair agreement with the designed values in terms of ultimate capacity and failure mode. The load bearing capacity enhancement of the RC jacketed column has been found to increase substantially. The enhancement capacity results obtained from the finite element software differs about 16-25% from the design values.

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Xing, Guo Hua, Yuan Pan, Guo Fu e Jian Ling Hou. "Cumulative Seismic Damage of Reinforced Concrete Columns: Variable Amplitude Tests". Applied Mechanics and Materials 52-54 (marzo 2011): 740–44. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.740.

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The findings from an experimental study to investigate cumulative seismic damage in reinforced concrete columns are presented. Fourteen identical half-scale concrete columns were fabricated and tested to failure. Results from Phase I testing, which included constant amplitude tests to determine the low-cycle fatigue characteristics of the rectangular concrete column, were presented in a companion paper. This paper summarizes results of variable amplitude tests. The imposed displacement histories were obtained from analytical simulations of the model column subjected to a series of earthquakes. Test observations indicate that failure is generally initiated by confinement inadequacy and the rupture of the transverse hoop reinforcement. The tests also demonstrated the potential for low-cycle fatigue fracture of the main longitudinal steel when the specimen was subjected to relatively larger displacement amplitudes. A fatigue-based damage model, derived from the constant-amplitude tests completed in Phase I testing, was applied to the observed response of the three specimens tested in this phase. Findings from the study indicate that the energy capacity of members is ductility-dependent and that fatigue-based damage models offer a reliable means of assessing seismic structural performance.

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Più fonti

Tesi sul tema "Columns, Concrete Testing Mathematical models"

Lanzas, Lourdes Eneida 1962. "A parametric study on the behavior of slender reinforced concrete frames". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276945.

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By using a nonlinear computer analysis, a parametric study is developed in order to examine the accuracy of the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The variables used in the parametric study are: axial load intensity, P/Po; column reinforcement ratio, rho; slenderness ratio, klu; shape of column cross section, flexural stiffness ratio, and distribution of axial loads. In the parametric study, 216 cases of single bay fixed-base portal frames are examined. The higher moment for each one of these frames at failure are then compared with the design moment predicted by the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The Moment Magnifier Method proved to be very conservative when the columns are subjected to high level of axial loads and when the slenderness ratio is increased.

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Ng, Ah Book. "Physical models in fire study of concrete structures". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64055.

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Lam, Wai-yin, e 林慧賢. "Plate-reinforced composite coupling beams: experimental and numerical studies". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37311797.

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Chan, Ka-ho Enoch, e 陳家灝. "Experimental and numerical studies of concrete beams prestressed with unbonded tendons". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40988004.

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Lokuge, W. P. (Weena Priyanganie) 1967. "Stress-strain behaviour of confined high strength concrete under monotonically increasing and cyclic loadings". Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9425.

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Thölken, Denise. "Efeito da rigidez de pilar parede no comportamento sísmico de edifício de concreto armado". Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/962.

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Este trabalho tem como objeto o estudo do efeito da rigidez de pilar parede no comportamento estrutural de edifícios de concreto armado submetidos a sismos. Foram consideradas as premissas da norma brasileira ABNT NBR15421:2006, que apresenta os critérios para projeto de estruturas resistentes a sismo. A análise linear com emprego dos métodos da norma - método das forças horizontais equivalentes, método espectral e histórico de aceleração no tempo - foi aplicada em edifícios com dois tipos de sistemas estruturais, sendo eles pórtico de concreto e sistema dual pórtico de concreto e pilar parede. Os resultados foram analisados nos pórticos de extremidade das estruturas nos sentidos longitudinal (x) e transversal (y), comparando-se os deslocamentos de cada pavimento e esforços cortantes, momento fletor e normal nas bases dos pilares. A comparação foi realizada entre os três métodos aplicados e os sistemas estruturais analisados.
The aim of this work is to study the stiffness effect of wall columns on structural behavior of reinforced concrete buildings subjected to seismic action. The premises of the Brazilian standard ABNT NBR14521:2006 were considered, which presents criteria for earthquake resistant design of structures. The linear analysis employed the methods of the Brazilian standard - equivalent static load method, response spectrum analysis and time history method - were applied to buildings with two types of structural systems, namely concrete frame and dual system concrete frame and wall columns. The results were analyzed in edge frames structures in the longitudinal and transverse directions, comparing the displacement of each floor and shear, bending moment and axial forces on the bases of the columns. A comparison was made between the three methods applied and the structural systems analyzed.

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Pessôa, José Renato de Castro. "Análise numérico-experimental de estruturas de concreto com utilização da energia de fraturamento". Universidade do Estado do Rio de Janeiro, 2007. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=780.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A evolução dos concretos utilizados nas últimas décadas deu origem ao Concreto de Alto Desempenho (CAD), que tem, entre suas características, alta resistência à compressão e baixa permeabilidade. Com o desenvolvimento dos produtos químicos utilizados na construção civil, em especial os superplastificantes e superfluidificantes, a utilização desse tipo de concreto tornou-se cada vez mais freqüente pela possibilidade de se obter uma mistura suficientemente trabalhável utilizando-se fatores água/cimento menores do que 0,35. Devido à sua microestrutura mais homogênea, esse tipo de concreto apresenta um comportamento mais frágil do que os concretos convencionais, exigindo uma melhor caracterização do material. A partir do final da década de 70 começou-se a aplicar os conceitos da Mecânica da Fratura para análise do comportamento de estruturas construídas com esse tipo de concreto. Como em algumas situações a resistência nominal de peças de concreto diminui com o aumento de suas dimensões, houve a necessidade de se considerar o efeito de escala das estruturas a fim de se obter níveis de segurança mais adequados no seu dimensionamento, o que justificou a utilização da Mecânica da Fratura. Neste trabalho a energia de fraturamento foi obtida experimentalmente pelo método do trabalho de fraturamento e pelo método do efeito de escala, por meio de ensaios estáveis de flexão de três pontos em amostras de concreto de alto desempenho com entalhe. Foi também desenvolvida a simulação numérica de uma viga com entalhe, analisada pelo método dos elementos finitos e empregando-se na modelagem constitutiva os conceitos da Mecânica da Fratura aplicada ao concreto. As vigas foram moldadas e ensaiadas no Instituto Politécnico do Rio de Janeiro (IPRJ) da Universidade do Estado do Rio de Janeiro (UERJ) na cidade de Nova Friburgo. Os ensaios foram realizados com controle de deslocamento da célula de carga. Foram ensaiadas três séries de 12 vigas, com quatro dimensões diferentes, geometricamente proporcionais, e três amostras para cada dimensão, totalizando 36 vigas. As alturas utilizadas para as vigas foram 38, 76, 152 e 304 mm, e sua espessura foi mantida constante igual a 38 mm. Os corpos de prova cilíndricos, para caracterização da resistência à compressão do concreto, foram moldados no IPRJ e rompidos no laboratório de engenharia civil da UERJ, na cidade do Rio de Janeiro. Os concretos utilizados apresentaram resistência à compressão média de 70 MPa.
The evolution of the concrete mixes used during the last decades gave birth to the High Performance Concrete (HPC), which, among its main characteristics, presents high strength and low permeability. With the development of chemical products used in civil engineering constructions, mainly the superplasticizers, the use of this kind of concrete has become more and more frequent due to the possibility of obtaining a workable mixture with a water/cement ratio lower than 0.35. Due to its more homogeneous microstructure, the HPC presents a more fragile behavior than the conventional concrete, demanding a better characterization of the material. At the end of the 1970s, concepts of the Fracture Mechanics started to be used for the analysis of the structural behavior of concrete structures. As the nominal stress of the material decreases as the size of the structure increases, it became necessary to consider this size effect in the analysis in order to obtain more suitable levels of security. This fact justifies the use of the Fracture Mechanics in the structural analysis of concrete structures. In this work, the fracture energy was experimentally obtained using the work-offracture method and the size effect method by performing three-point bend tests in HPC notched beams. It was also developed a numerical simulation of the tests, performing the analysis through the Finite Element Method and applying the concepts of the Fracture Mechanics of Concrete into the constitutive model. The notched beams were molded and tested at the Polytechnic Institute of the State University of Rio de Janeiro (IPRJ/UERJ), located in the city of Nova Friburgo. The tests were controlled by the vertical displacement of the load cell. Three series of twelve beams with four geometrically similar sizes were tested. Three samples for each size were cast, making an amount of 36 beams. The beams were 38, 76, 152 and 304 millimeters high and the width was kept constant equal to 38 millimeters. To characterize the concrete compression strength, 100x200 millimeters cylinders were molded at the IPRJ and tested at the UERJ civil engineering laboratory in the city of Rio de Janeiro. The tested concretes presented a medium compressive strength of 70 MPa.

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Wu, Y. F. (Yu-Fei). "Seismic retrofitting of rectangular reinforced concrete columns with partial interaction plating". 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phw9591.pdf.

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Wu, Y. F. (Yu-Fei). "Seismic retrofitting of rectangular reinforced concrete columns with partial interaction plating / by Yu-Fei Wu". Thesis, 2002. http://hdl.handle.net/2440/21836.

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"June 2002"
Includes bibliographical references (leaves 349-374)
xxxix, 416 leaves : ill., plates ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2002

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Kitterman, David L. "A generalized three-parameter biaxial strength criterion for concrete". 1985. http://hdl.handle.net/2097/27525.

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Più fonti

Libri sul tema "Columns, Concrete Testing Mathematical models"

Bažant, Z. P. Concrete at high temperatures: Material properties and mathematical models. Harlow: Longman, 1996.

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Xie, Jueren. Numerical investigation of eccentrically loaded tied high strength concrete columns. Edmonton, Alta., Canada: Dept. of Civil Engineering, University of Alberta, 1994.

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Kerr, Arnold D. The assessment of concrete pavement blowups: A user manual. McLean, Va: U.S. Dept. of Transportation, Federal Highway Administration, 1993.

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Tejchman, Jacek. Steel-fibrous concrete: Experiments and a numerical discrete model. Gdańsk: Wydwan. Politechniki Gdańskiej, 2000.

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(undifferentiated), Walter Kaufmann. Strength and deformations of structural concrete subjected to in-plane shear and normal forces. Basel: Birkhäuser Verlag, 1998.

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Gauvreau, Paul. Ultimate limit state of concrete girders prestressed with unbonded tendons. Basel: Birkhauser Verlag, 1993.

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Chernenko, Diana E. An analysis of the performance of welded wide flange columns. Edmonton, Alta: Dept. of Civil Engineering, University of Alberta, 1988.

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Halicka, Anna. Studium stanu naprężeń i odkształceń w płaszczyźnie styku i strefie przypodporowej elementów zespolonych z udziałem betonów skurczowych i ekspansywnych: A study of the stress-strain state in the interface and support zones of composite structures with shrinking and expansive concretes. Lublin: Wydawnictwo Politechniki Lubelskiej, 2007.

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Stephens, Jerry E. Performance of steel pipe pile-to-concrete bent cap connections subject to seismic or high transverse loading, phase II: Final report. Helena]: Montana Dept. of Transportation, 2005.

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Stephens, Jerry E. Performance of steel pipe pile-to-concrete bent cap connections subject to seismic or high transverse loading, phase II: Project summary report. Helena, Mont: Montana Dept. of Transportation, 2005.

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Capitoli di libri sul tema "Columns, Concrete Testing Mathematical models"

Broy, Manfred, Wolfgang Böhm e Bernhard Rumpe. "Advanced Systems Engineering". In Model-Based Engineering of Collaborative Embedded Systems, 353–64. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-62136-0_19.

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AbstractAdvanced systems engineering (ASE) is a new paradigm for agile, efficient, evolutionary, and quality-aware development of complex cyber-physical systems using modern digital technologies and tools. ASE is essentially enabled by smart digital modeling tools for specifying, modeling, testing, simulating, and analyzing the system under development embedded in a coherent and consistent methodology.The German Federal Ministry of Education and Research (BMBF) projects SPES2020, SPES_XT, and CrESt offer such a methodology and framework for model-based systems engineering (MBSE). The framework provides a comprehensive methodology for MBSE that is independent of tools and modeling languages. The framework also offers a comprehensive set of concrete modeling techniques and activities that build on a formal, mathematical foundation. The SPES framework is based on four principles that are of paramount importance: (1) Functional as well as non-functional requirements fully modeled and understood at system level. (2) Consistent consideration of interfaces at each system level. (3) Decomposition of systems into subsystems and their interfaces. (4) Models for a variety of cross-sectional topics (e.g., variability, safety, dynamics).

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"Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems". In Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems. American Fisheries Society, 2003. http://dx.doi.org/10.47886/9781888569469.ch10.

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Abstract.—We examine decision-support models designed to help recover salmon Oncorhynchus spp. in the Columbia River Basin as a case study for the use of models to help resolve scientific uncertainty and select management options. The models all have somewhat different objectives, use different data, and deal with a variety of salmon-related issues. Divergence of model outputs has, in the past, been used to justify different policy positions, leading some to conclude that science has failed to provide clarity to salmon recovery planning. Three distinct approaches are represented in the models: decision analysis, statistical, and expert system. Of the three approaches, decision analysis provides the clearest management advice and the most formal method for treating uncertainty. Its success depends on the engagement of decision makers in framing questions, identifying management options under consideration, and assigning values to possible outcomes. However, decision analysis could be very difficult to perform. As an alternative, the statistical model is the traditional scientific approach and it can operate with a large degree of detachment from policy. Statistical models proceed by testing hypotheses and estimating life-cycle parameters with available data. They have the advantage of scientific clarity, rigor, and empirical objectivity. The limitation of a statistical model is that the scope of the questions and their answers are restricted by availability of data, and in a domain that is data-poor, many pressing questions go unanswered. Expert system approaches fill gaps in data with expert opinion. In the context of salmon recovery, expert opinion allows consideration of the most concrete menu of specific options for salmon management. Expert opinion is a weaker basis for scientific prediction than is a mathematical relationship validated with empirical data. However, at the level of spatial resolution and environmental detail required to make salmon management decisions affecting the entire Columbia River Basin, there are no validated mathematical formulae for predicting the effects of management actions on salmon, and no adequate data archive exists for deriving such relationships. Communication between scientists and managers is improved when there is a formal institutional mechanism for summarizing scientific results and clarifying the interpretation of models for policy makers. If a modeling effort is driven by a desire to contribute to a particular decision, it is helpful to initially invest in enough communication to ensure that the model really is addressing the right question. Scientists can help managers craft decision rules that are formalized before analyses are undertaken. Decision rules define what measurements will be made, what statistical operations will be performed, and what threshold magnitudes of estimated quantities at specified levels of certainty will serve as criteria for the decision. Such specifications ensure that model results are properly used in the decision process. Committing to these specifications in advance helps dispel suspicions that analyses may be manipulated to achieve a particular outcome.

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Atti di convegni sul tema "Columns, Concrete Testing Mathematical models"

Marginean, Ioan, Florea Dinu, Dan Dubina, Ahmed Amir Khalil e Emiliano De Iuliis. "Factors affecting the response of steel columns to close-in detonations". In 12th international conference on ‘Advances in Steel-Concrete Composite Structures’ - ASCCS 2018. Valencia: Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/asccs2018.2018.7186.

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Explosions produced in urban areas by the detonation of explosives are low-probability but high-impact events. When they occur in the immediate vicinity of buildings, the explosions can pose a high risk to the structural integrity (local/global failures) and to the occupants (risk of injury, death). Therefore, the design and the construction of the buildings should contain preventive measures to increase the robustness of the structures. The paper presents the results of recent research carried out on the safety of building structures under extreme actions. Blast tests performed on two identical 3D specimen extracted from a typical moment resisting steel frame structure, allow to calibrate the numerical models of a full scale building structural frame system and evaluate the consequences of close-in detonations on the structural elements. The data of the experimental testing, combined with the numerical modelling, allow to investigate different factors, such as dynamic factors that affect the local failure mechanism and the residual capacity of steel columns under different blast scenarios.

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Chrzanowski, Maciej, Christoph Odenbreit, Renata Obiala, Teodora Bogdan, Matthias Braun e Herve Degee. "Development of an innovative type of shear connector dedicated to fully embedded steel-concrete composite columns – experimental and numerical investigations." In 12th international conference on ‘Advances in Steel-Concrete Composite Structures’ - ASCCS 2018. Valencia: Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/asccs2018.2018.6970.

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A shear connection in steel-concrete composite columns is established in the normal case with headed shear studs. However, this type of connector was developed for composite beams and in terms of composite columns, a wide range for an optimisation still can be identified due to the different geometries of steel profiles, concrete and reinforcement. The presented paper shows investigations on a new type of shear connector with a direct application to composite columns and with a potential for a fully automatic fabrication process. The proposed new type of shear connection is made out of reinforcement bars welded to the external surfaces of the steel profile’s flanges. The experimental campaign consisted of 12 composite push-out tests with a column section geometry. The analysed specimens included centrally embedded HEB120 steel profiles into 340x1000x450mm concrete blocks. All the tests have been categorized into 4 groups. One group per connector was defined (including group without mechanical connector). Each group had 3 identical specimens. Surface treatment conditions, reinforcement arrangement, used materials and test layout were the same in all executed tests. The acquired results showed a good performance of the proposed solutions and allowed to identify the different load-bearing behaviour. After the test execution, the specimens were opened and the failure pattern have been investigated. The testing campaign was supported by numerical simulations performed with the finite element software code Abaqus®. In the developed models, a new approach to simulate the steel-concrete bond was implemented.

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Haynes, Mark D., Chih-Hang John Wu, Matthew Arnold, Naga Narendra B. Bodapati, B. Terry Beck e Robert J. Peterman. "Bond Index Numbers of Prestressed Concrete Reinforcement Wires and Their Relationships to Transfer Lengths and Pull-Out Forces". In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5787.

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The purpose of this research is to establish mathematical models that predicts the bond strength of a reinforcement wire in prestressed concrete members, given the known geometrical features of the wire. A total of nineteen geometrical features of the reinforcement wire were measured and extracted by a precision non-contact profilometer. With these mathematical models, prestressing reinforcement wires can now be analyzed for their bond strength without destructive testing. These mathematical models, based upon a large collection of empirical data via prestressing reinforcement wires from various wire manufacturers in US and Europe, have the potential to serve as quality assessment tools in reinforcement wire and prestressed concrete member production. Most of these models are very simple and easy to implement in practice, which could provide insight into which reinforcement wires provide the greatest bond strength and which combinations of geometrical features of the reinforcement wire are responsible for providing the bond strength. Our various empirical models have shown that the indent side-wall angle, which is suggested by the ASTM-A881/A881M, may not be the only significant geometrical feature correlated to the transfer length and bond strengths. On the contrary, features such as the indent surface area, indent width, indent edge surface area, indent volume, and release strengths do have significant correlations with the ultimate transfer lengths of the prestressed concrete members. Extensive experiments and testing performed at the Structures Laboratory in Kansas State University, as well as field tests at Transportation Technology Center, Inc. (TTCI) and one Prestressed Concrete Railroad Tie manufacturing facility, have been used to confirm the model predictions. In addition, our experimental results suggest that the maximum pull out force in the un-tensioned pullout testing has significant correlation with the ultimate transfer length. This finding could provide reinforcement wire manufactures with a quality assurance tool for testing their wires prior to the production. The resultant mathematical model relating the wire geometrical features to transfer length is referred to as the Bond Index Number (BIN). The BIN is shown to provide a numerical measure of the bond strength of prestressing steel reinforcement wire, without the need for performing destructive tests with the reinforcement wire. We believe that with the BIN and the maximal pull-out forces from the un-tensioned pull-out tests, one can have better insight into the optimal reinforcement wire design by testing the performance of wires before they are put into production lines.

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Yu, Hailing, e David Jeong. "Finite Element Bond Modeling for Indented Wires in Pretensioned Concrete Crossties". In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5782.

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Indented wires have been increasingly employed by concrete crosstie manufacturers to improve the bond between prestressing steel reinforcements and concrete, as bond can affect several critical performance measures, including transfer length, splitting propensity and flexural moment capacity of concrete ties. While extensive experimental testing has been conducted at Kansas State University (KSU) to obtain bond characteristics of about a dozen commonly used prestressing wires, this paper develops macro-scale or phenomenological finite element bond models for three typical wires with spiral or chevron indent patterns. The steel wire-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. The cohesive elements are assigned traction-displacement constitutive or bond relations that are defined in terms of normal and shear stresses versus interfacial dilatation and slip within the elasto-plastic framework. A yield function expressed in quadratic form of shear stress and linear form of normal stress is adopted. The yield function takes into account the adhesive mechanism and hardens in the post-adhesive stage. The plastic flow rule is defined such that the plastic dilatation evolves with the plastic slip. The mathematical forms of the yield and plastic flow functions are the same for all three wire types, but the bond parameters are specific for each wire. The adhesive, hardening and dilatational bond parameters are determined for each wire type based on untensioned pullout tests and pretensioned prism tests conducted at KSU. Simulation results using these bond models are further verified with surface strain data measured on actual concrete crossties made with the three respective prestressing wires at a tie manufacturing plant.

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Haynes, Mark, Chih-Hang John Wu, B. Terry Beck, Naga Narendra B. Bodapati e Robert J. Peterman. "Prestressing Steel Reinforcement Wire Bond Index Number". In 2013 Joint Rail Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/jrc2013-2422.

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The purpose of this research project is to develop a mathematical model that predicts the bond strength of a prestressing steel reinforcement wire given the known geometrical features of the wire. The geometrical features of the reinforcement wire were measured by a precision non-contact profilometer. With this mathematical model, prestressing reinforcement wires can now be analyzed for their bond strength without destructive testing. This mathematical model has the potential to serve as a quality control assessment in reinforcement wire production. In addition this mathematical model will provide insight into which reinforcement wires provide the greatest bond strength and which combinations of geometrical features of the reinforcement wire are responsible for providing the bond strength. A precision non-contact profilometer has been developed to measure the important geometrical features of the reinforcement wire. The profilometer is capable of sub-micron resolution measurements to provide an extremely high quality three-dimensional rendering of the reinforcement wire surface profile. From this detailed profile data it is then possible to extract all of the relevant geometrical features of the reinforcement wire. A mathematical model has been created by testing a variety of different reinforcement wires available in the market. By correlating the transfer length of concrete prisms made with the reinforcement wires to various geometrical features, several different levels of mathematical correlation complexity have been investigated. The current empirical correlation models under development are first order and combine three to four unique geometrical features of the reinforcement wire which then act as predictors of the concrete prism transfer length. The resulting mathematical model relating the wire geometrical features to transfer length is referred to as the Bond Index Number (BIN). The BIN is shown to provide a numerical measure of the bond strength of prestressing steel reinforcement wire, without the need for performing destructive tests with the reinforcement wire.

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Bajaj, Mayank, e Biswajit Bhattacharjee. "Residual service life estimation of bridges". In IABSE Congress, Christchurch 2021: Resilient technologies for sustainable infrastructure. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2021. http://dx.doi.org/10.2749/christchurch.2021.0984.

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While concrete structures perform well in many situations, lack of durability has emerged as a significant issue for asset owners. A review of past bridge failures was done to identify the most probable causes of bridge failures. This study has tended to focus on current models used for estimating the time to deterioration of concrete bridges instigated by Chloride ingress and Fatigue. Subsequently, mathematical modelling of the best-suited deterioration model is done to arrive at the residual life of two existing bridges. This work has highlighted high variability in the parameters used to describe the durability related properties of in-situ aged concrete. A realistic residual life assessment can be achieved by correct evaluation of these parameters by periodic testing of bridge samples

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Tortoriello, Miguel A., Luis J. Lima, Ana C. Cobas e Renso A. Cichero. "Timber bodies strength of materials: Fundamental principles, test specimens proposal". In IABSE Congress, Christchurch 2021: Resilient technologies for sustainable infrastructure. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2021. http://dx.doi.org/10.2749/christchurch.2021.1112.

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To reduce the economic cost of a Timber Structure, the first condition is to have a “rational” Structural Code, that is, a Code supported by research and a specific theory. To establish a rational Structural Timber Code, a specific theoretical support is needed. The objective of this paper is to cooperate in the construction of this theoretical support. To design timber structures, it is necessary to have mathematical models able to reproduce the resistance of timber bodies under different solicitations. In this paper, a “road map” to arrive to a specific Strength of Materials of Timber Bodies is proposed. This theory will be the tool needed to develop the mathematical models whose quantification will be obtained by testing “basic test specimens” obtained from timber of any particular timber building (like in concrete or soil mechanics). Finally, a “basic test specimen” for practical application of the theory is proposed. In this case, the experimental support is referred to “willow” wood.

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Xue, Ruo-Jun, e Ji-Lin Sun. "Modeling and Simulation of Deaerator in Nuclear Power Plant". In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30452.

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Different deaerators have different structures, and the intensities of deaerating are different. But the deaerator models without considering the structure couldn’t show these aspects. In order to ensure the accuracy of simulation results, concrete structure of the deaerator should be taken into consideration. This paper carried out a mathematical model of horizontal type deaerator with constant nozzles and trays in nuclear power plants. It was built based on the structure of the segmentation deaerators and the process of heat transferring. This paper calculated the vapors condensation rate, it was based on heat transfer coefficient of direct contact condensation, and the heat transfer area of water film when working conditions were corresponding to the empirical formulas. While the working conditions were beyond the limits of empirical formulas, this paper would build models by conservation of energy, so the model could work under any working conditions. These models were installed in the simulation system of Qinshan Phase II., and were tested under variable power and accidental conditions. The testing results show that the models could fit for different steady working conditions. Compared with the outputs and the actual operating data, the error was small. Under the conditions of variable power and turbine tripping, changing of the parameters have the same trend curve with the actual operating data. Because of taking the concrete structure into consideration, these models can be performed better of the specific characteristics of the horizontal type deaerators with constant nozzles and trays in nuclear power plants, therefore the results are more accurate than the models without considering the structure.

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Pitts, Katie Lieg, e Timothy Shedd. "Viscosity Studies of Aqueous Solutions of Hafnium Oxide Particles and Polystyrene Nanospheres". In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30826.

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Nanoparticle colloidal system rheology has long been researched, without many concrete conclusions. Literature has been devoted to the viscosity and shear properties of these systems since Einstein’s PhD thesis. However, most models are based on molecular dynamics which are not necessarily applicable to real systems, and most real systems are modeled by empiricism. This report looks to unify these approaches through rheological testing and mathematical analysis in order to achieve several goals using a system composed of hafnium oxide particles suspended in water. The first goal is to have a viscosity model that fits not only empirical data, but also the relevant theory and first principles. By employing the modern techniques of a rhoemeter-on-a-chip to nano-scale particles, the limitations of traditional rheometry are bypassed. The molecular dynamics approaches are converted to zero-shear and infinite-shear viscosities which can be applied to traditional models. A modern model was then derived, applied to new data, and agreement was found to a satisfactory degree. No significant change in viscosity with shear rate was found experimentally or analytically. Traditional research is done with spherical particles, such as polystyrene nanopsheres, as which we are approximating hafnium oxide (HfOx) to be. Polystyrene nanospheres are nominally spherical and commercially available at relatively inexpensive costs. Actual spherical data was required for appropriate comparison, and the findings show that the spherical particles have distinct properties.

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