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A aplicação estrutural de betões de elevado desempenho (HPC e UHPC)

Fernandes, Diogo Amaro Freitas
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2011 Português
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Dissertação para obtenção do Grau de Mestre em Engenharia Civil; A evolução dos betões, na procura de estruturas com um maior tempo de vida útil, menores custos de reparação e maiores resistências tem sido alvo de pesquisa por investigadores de todo o mundo. No presente trabalho é apresentado o estado da arte dos betões de elevado desempenho (HPCHigh Performance Concrete e UHPC-Ultra High Performance Concrete), betões garantes de maior durabilidade e resistência, com o objectivo de conhecer as inovações trazidas por estes, na aplicação estrutural actual. A durabilidade e resistência incrementadas por estes betões às estruturas é um dos temas abordados, referindo-se quais os seus constituintes que maximizam as suas características. O benefício da sua aplicação em elementos estruturais de edifícios e pontes é abordado, exemplificando-se obras diversificadas onde este material teve um papel preponderante. Algumas constituições patenteadas pelos maiores produtores mundiais de UHPC são descritas. Para um maior desenvolvimento dos HPC e UHPC, o estabelecimento de recomendações internacionais é fundamental, apesar de existirem na actualidade algumas recomendações internacionais, nacionais e associativas.

Prediction of early-age cracking of UHPC materials and structures : a thremo-chemo-mechanics approach

Shim, JongMin, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 159, [13] p.; 7805482 bytes; 7826831 bytes; application/pdf; application/pdf
Português
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Ultra-High Performance Concrete [UHPC] has remarkable performance in mechanical properties, ductility, economical benefit, etc., but early-age cracking of UHPC can become an issue during the manufacturing process due to the high cement content and the highly exothermic hydration reaction. Because of the risk of early-age UHPC cracking, there is a need to develop a material model that captures the behavior of UHPC at early-ages. The objective of this research is to develop a new material model for early-age UHPC through a thermodynamics approach. The new model is a two-phase thermo-chemo-mechanical model, which is based on two pillars: the first is a hardened two-phase UHPC material model, and the second is a hydration kinetics model for ordinary concrete. The coupling of these two models is achieved by considering the evolution of the strength and stiffness properties in the two-phase UHPC material model in function of the hydration degree. The efficiency of the model and finite element implementation is validated with experimental data obtained during the casting of a DuctalTM optimized bridge girder. Based on some decoupling hypothesis, the application of the early-age UHPC model can be carried out in a two-step manner: the thermo-chemical problem is solved first...

Recommendations for the design of ultra-high performance concrete structures; Recommendations for the design of UHPC structures

Davila, Ricardo S
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 125 leaves
Português
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New materials frequently require modifications or rewrites of existing construction codes. They may also need new methods for their manufacture and installation. DUCTAL, a new ultra-high performance concrete (UHPC) with enhanced tensile, compressive, and deflective behavior offered by LaFarge, is one such material, and current guidelines for concrete do not sufficiently account for these improved properties. Research by other universities and professional institutions has produced sequential recommendations, beginning with the experiment-based set from the Association Francaise de Genie Civil (AFGC) through the analytically-based set from MIT. In this thesis, the MIT approach is further developed into a coherent method for hardened UHPC design. The first two sections familiarize the reader with the analytical model for UHPC and the evolution in design codes and their philosophical bases. Essential concepts, such as the two-phase matrix-fiber behavior of the material and the use of a maximum crack width criterion to govern design, are explained. Next, the most current design guidelines are presented in full, with attention paid to bending and shear resistance. Comparisons with previous codes demonstrate the ability of these guidelines to produce more structurally efficient sections which consume less material.; (cont.) Analysis of the recommendations themselves will demonstrate the existence of a size effect and the cross-sectional parameters that affect structural efficiency most. Optimization based on the one-dimensional analytical model closes with an analysis of different cross-sections for their structural efficiency...

Model-based design of an ultra high performance concrete support structure for a wind turbine

Wang, Zheng, M. Eng. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 48 leaves
Português
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A support tower is the main structure which would support rotor, power transmission and control systems, and elevates the rotating blades above the earth boundary layer. A successful design should ensure safe, efficient and economic design for the whole wind turbine system. It should provide easy construction and easy access for maintenance of the rotor components and sub-components. UHPC materials have been used in various structural applications, such as highway bridge girders. There is no much research about its application in support structures of wind turbines. After meeting the requirements for loads, minimizing cost is the next most important design driver. Here at MIT, Chuang and Professor Ulm developed a new constitutive model for fiber reinforced cementitious composite materials, which is particularly suitable for high performance cementitious composites including UHPC. On the basis of UHPC material model and the load requirements for wind turbines, the objective of this work is to carry out a tentative design of the UHPC support tower for a prototype wind turbine.; (cont.) Two tube-type cross sections are examined. The 3-d analysis reveals a sufficient flexural performance of the UHPC support tower when subjected to the extreme wind loads. Since this work only focuses on the extreme wind load case...

Model-based design of a ultra high performance concrete prototype highway bridge girder; Model based design of a UHPC prototype bridge

Soh, Melvin, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 64 leaves
Português
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by Melvin Soh.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.; Includes bibliographical references (leaf 64).

Model-based optimization of ultra high performance concrete highway bridge girders; Model-based optimization of UHPC highway bridge girders

Park, Hesson, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 139 p.
Português
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by Hesson Park.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.; Includes bibliographical references (p. 135-138).

Alternatives to steel grid bridge decks

Saleem, Muhammad Azhar
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
Português
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Most of the moveable bridges use open grid steel decks, because these are factory assembled, light-weight, and easy to install. Open grid steel decks, however, are not as skid resistant as solid decks. Costly maintenance, high noise levels, poor riding comfort and susceptibility to vibrations are among the other disadvantages of these decks. The major objective of this research was to develop alternative deck systems which weigh no more than 25 lb/ft2, have solid riding surface, are no more than 4–5 in. thick and are able to withstand prescribed loading. Three deck systems were considered in this study: ultra-high performance concrete (UHPC) deck, aluminum deck and UHPC-fiber reinforced polymer (FRP) tube deck. ^ UHPC deck was the first alternative system developed as a part of this project. Due to its ultra high strength, this type of concrete results in thinner sections, which helps satisfy the strict self-weight limit. A comprehensive experimental and analytical evaluation of the system was carried out to establish its suitability. Both single and multi-unit specimens with one or two spans were tested for static and dynamic loading. Finite element models were developed to predict the deck behavior. The study led to the conclusion that the UHPC bridge deck is a feasible alternative to open grid steel deck. ^ Aluminum deck was the second alternative system studied in this project. A detailed experimental and analytical evaluation of the system was carried out. The experimental work included static and dynamic loading on the deck panels and connections. Analytical work included detailed finite element modeling. Based on the in-depth experimental and analytical evaluations...

Alternatives to Steel Grid Bridge Decks

Saleem, Muhammad A
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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Most of the moveable bridges use open grid steel decks, because these are factory assembled, light-weight, and easy to install. Open grid steel decks, however, are not as skid resistant as solid decks. Costly maintenance, high noise levels, poor riding comfort and susceptibility to vibrations are among the other disadvantages of these decks. The major objective of this research was to develop alternative deck systems which weigh no more than 25 lb/ft2, have solid riding surface, are no more than 4-5 in. thick and are able to withstand prescribed loading. Three deck systems were considered in this study: ultra-high performance concrete (UHPC) deck, aluminum deck and UHPC-fiber reinforced polymer (FRP) tube deck. UHPC deck was the first alternative system developed as a part of this project. Due to its ultra high strength, this type of concrete results in thinner sections, which helps satisfy the strict self-weight limit. A comprehensive experimental and analytical evaluation of the system was carried out to establish its suitability. Both single and multi-unit specimens with one or two spans were tested for static and dynamic loading. Finite element models were developed to predict the deck behavior. The study led to the conclusion that the UHPC bridge deck is a feasible alternative to open grid steel deck. Aluminum deck was the second alternative system studied in this project. A detailed experimental and analytical evaluation of the system was carried out. The experimental work included static and dynamic loading on the deck panels and connections. Analytical work included detailed finite element modeling. Based on the in-depth experimental and analytical evaluations...

Novel Hybrid Columns Made of Ultra-High Performance Concrete and Fiber Reinforced Polymers

Zohrevand, Pedram
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore...

Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

Zohrevand, Pedram
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
102.47568%
The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. ^ The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore...

Assessment of Direct Shear Behavior in Normal and Ultra-High-Performance Concretes

French, Robin E
Fonte: University of Florida; University of Florida ( [Gainesville, Fla.] ) Publicador: University of Florida; University of Florida ( [Gainesville, Fla.] )
Tipo: Artigo de Revista Científica Formato: 1 online resource (10 p.)
Publicado em //2014 Português
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In the series University of Florida Digital Collections.; Includes vita.; (Bibliography) Includes bibliographical references.; (Source of Description) Description based on online resource; title from PDF title page.; (Source of Description) This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.; (Statement of Responsibility) by Robin E French.; (Thesis) Thesis (M.S.)--University of Florida, 2014.; (Local) Adviser: KRAUTHAMMER,THEODOR.; (Local) Co-adviser: ASTARLIOGLU,SERDAR.

Research development on protection of structures against blast loading at University of Adelaide

Wu, C.
Fonte: Institution of Engineers Australia Publicador: Institution of Engineers Australia
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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This paper presents a review of research into the protection of structural members against blast loading at The University of Adelaide, including experimental, analytical and numerical studies on characteristics of blast loading, blast resistance of structural members and mitigation of blasts effects on structural members using retrofitting techniques. Explosive blasts are investigated experimentally and numerically to study the distributions of peak overpressure and impulse generated from spherical charges and cylindrical charges with different orientations in unconfined and confined environments. A series of blast tests on reinforced concrete (RC) slabs, ultra-high performance concrete (UHPC) slabs, and aluminium foam protected RC slabs was conducted to investigate the performance of those slabs under blast loads. With the blast testing data numerical models including single degree of freedom model, finite difference model and final element model, have been developed and validated and those numerical models are then used to analyse the blast effects of RC, UHPC and foam protected RC slabs. Investigation of mitigation of blast effects on masonry structures is also addressed.; C Wu

Derivation of normalized pressure impulse curves for flexural ultra high performance concrete slabs

Dragos, J.; Wu, C.; Haskett, M.; Oehlers, D.
Fonte: ASCE-Amer Soc Civil Engineers Publicador: ASCE-Amer Soc Civil Engineers
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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In previous studies, a finite-difference procedure was developed to analyze the dynamic response of simply supported normal reinforced concrete (NRC) slabs under blast loads. Ultra high performance concrete (UHPC) is a relatively new material with high strength and high deformation capacity in comparison with conventional normal strength concrete. Therefore, the finite-difference procedure for analysis of conventional reinforced concrete members against blast loads needs to be significantly adapted and extended to accommodate UHPC. In this paper, an advanced moment-rotation analysis model, employed to simulate the behavior of the plastic hinge of an UHPC member, is incorporated into the finite-difference procedure for the dynamic response analysis of reinforced UHPC slabs under blast loads. The accuracy of the finite-difference analysis model that utilized the moment-rotation analysis technique was validated using results from blast tests conducted on UHPC slabs. The validated finite-difference model was then used to generate pressure impulse (PI) curves. Parametric studies were then conducted to investigate the effects of various sectional and member properties on PI curves. Based on the simulated results, two equations were derived that can be used to normalize a PI curve. Further numerical testing of the normalization equations for UHPC members was then undertaken. The generated normalized PI curve...

An experimental and numerical study of reinforced ultra-high performance concrete slabs under blast loads

Li, J.; Wu, C.; Hao, H.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
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Abstract not available; Jun Li, Chengqing Wu, Hong Hao

Innovative Modular High Performance Lightweight Decks for Accelerated Bridge Construction

Ghasemi, Sahar -
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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At an average age of 42 years, 10% of the nation’s over 607,000 bridges are posted for load restrictions, with an additional 15% considered structurally deficient or functionally obsolete. While there are major concerns with decks in 75% of structurally deficient bridges, often weight and geometry of the deck further limit the load rating and functionality of the bridge. Traditional deck systems and construction methods usually lead to prolonged periods of traffic delays, limiting options for transportation agencies to replace or widen a bridge, especially in urban areas. The purpose of this study was to develop a new generation of ultra-lightweight super shallow solid deck systems to replace open grid steel decks on movable bridges and as well serve as a viable alternative in bridge deck replacements across the country. The study has led to a lightweight low-profile asymmetric waffle deck made with advanced materials. The asymmetry comes from the arrangement of primary and secondary ribs, respectively perpendicular and parallel to the direction of traffic. The waffle deck is made with ultrahigh performance concrete (UHPC) reinforced with either high-strength steel (HSS) or carbon fiber reinforced polymer (CFRP) reinforcement. With this combination...

Experimental and computational analysis of the behavior of ultra high performance concrete at early age

Wan, Lin; Wendner, Roman; Liang, Benliang; Cusatis, Gianluca
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/09/2015 Português
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Ultra high performance concretes (UHPCs) are cementitious composite materials with high level of performance characterized by high compressive strength, high tensile strength and superior durability, reached by low water-to-binder ratio, optimized aggregate size distribution, thermal activation, and fiber reinforcement. In the past couple of decades, more and more UHPCs have been developed and found their way into practice. Thus, also the demand for computational models capable of describing and predicting relevant aging phenomena to assist design and planning is increasing. This paper presents the early age experimental characterization as well as the results of subsequent simulations of a typical UHPC matrix. Performed and simulated tests include unconfined compression, splitting (Brazilian), and three-point-bending tests. The computational framework is formulated by coupling a hygro-thermo-chemical (HTC) theory with a comprehensive mesoscale discrete model. The HTC component allows taking into account various types of curing conditions with varying temperature and relative humidity and predicting the level of concrete aging, while the mechanical component, based on a recently formulated discrete model, the Lattice Discrete Particle Model (LDPM)...