Дисертації з теми "High strength Testing"
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1
Mitchell, Andrew Douglass. "Shear friction behavior of high-strength concrete." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19274.
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Roenker, Andrew T. "Testing of Torque-and-Angle High Strength Fasteners." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490701582262578.
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Yosefani, Anas. "Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade Concrete." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4402.
Повний текст джерелаАнотація:
Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes.
The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement.
The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking.
The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.
4
Dabbagh, Hooshang Civil & Environmental Engineering Faculty of Engineering UNSW. "Strength and ductility of high-strength concrete shear walls under reversed cyclic loading." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/27467.
Повний текст джерелаАнотація:
This study concerns the strength and behaviour of low-rise shear walls made from high-strength concrete under reversed cyclic loading. The response of such walls is often strongly governed by the shear effects leading to the shear induced or brittle failure. The brittle nature of high-strength concrete poses further difficulties in obtaining ductile response from shear walls. An experimental program consisting of six high-strength concrete shear walls was carried out. Specimens were tested under inplane axial load and reversed cyclic displacements with the test parameters investigated being longitudinal reinforcement ratio, transverse reinforcement ratio and axial load. Lateral loads, lateral displacements and the strains of reinforcement in edge elements and web wall were measured. The test results showed the presence of axial load has a significant effect on the strength and ductility of the shear walls. The axially loaded wall specimens exhibited a brittle behaviour regardless of reinforcement ratio whereas the specimen with no axial load had a lower strength but higher ductility. It was also found that an increase in the longitudinal reinforcement ratio gave an increase in the failure load while an increase in the transverse reinforcement ratio had no significant effect on the strength but influenced the failure mode. A non-linear finite element program based on the crack membrane model and using smeared-fixed crack approach was developed with a new aggregate interlock model incorporated into the finite element procedure. The finite element model was corroborated by experimental results of shear panels and walls. The finite element analysis of shear wall specimens indicated that while strengths can be predicted reasonably, the stiffness of edge elements has a significant effect on the deformational results for two-dimensional analyses. Therefore, to capture the deformation of walls accurately, three-dimensional finite element analyses are required. The shear wall design provisions given in the current Australian Standard and the Building Code of American Concrete Institute were compared with the experimental results. The comparison showed that the calculated strengths based on the codes are considerably conservative, specially when there exists the axial load.
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Zaina, Mazen Said Civil & Environmental Engineering Faculty of Engineering UNSW. "Strength and ductility of fibre reinforced high strength concrete columns." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/22054.
Повний текст джерелаАнотація:
The main structural objectives in column design are strength and ductility. For higher strength concretes these design objectives are offset by generally poor concrete ductility and early spalling of the concrete cover. When fibres are added to the concrete the post peak characteristics are enhanced, both in tension and in compression. Most of the available experimental data, on fibre reinforced concrete and fibre reinforced high strength concrete columns, suggest that an improvement in both ductility and load carrying capacity due to the inclusion of the fibres. In this thesis the ductility and strength of fibre reinforced high strength concrete are investigated to evaluate the effect of the different parameters on the performance of columns. The investigation includes both experimental and the numerical approaches with 56 high strength fibre reinforced concrete columns being tested. The concrete strength ranged between 80 and 100 MPa and the columns were reinforced with 1, 2 or 2.6 percent, by weight, of end hooked steel fibres. The effect of corrugated Polypropylene fibres on the column performance was also examined. No early spalling of the cover was observed in any of the steel fibre reinforced column tested in this study. A numerical model was developed for analysis of fibre and non-fibre reinforced eccentrically loaded columns. The column is modelled as finite layers of reinforced concrete. Two types of layers are used, one to represent the hinged zone and the second the unloading portion of the column. As the concrete in the hinged layers goes beyond the peak for the stress verus strain in the concrete the section will continue to deform leading to a localised region within a column. The numerical model is compared with the test data and generally shows good correlation. Using the developed model, the parameters that affect ductility in fibre-reinforced high strength concrete columns are investigated and evaluated. A design model relating column ductility with confining pressure is proposed that includes the effects of the longitudinal reinforcement ratio, the loading eccentricity and the fibre properties and content and design recommendations are given.
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Tantbirojn, Natee. "Fatigue testing of weldable high strength steels under simulated service conditions." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399077.
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Meyer, Karl F. "Transfer and development length of 06-inch diameter prestressing strand in high strength lightweight concrete." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20727.
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Chen, Ju, and 陳駒. "Behaviour of high strength steel columns at elevated temperatures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B37936554.
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Islam, Md Shahidul. "Shear capacity and flexural ductility of reinforced high- and normal-strength concrete beams." Thesis, Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1766536X.
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Malpally, Deepthi Rao. "Uncertainty Analysis of Mechanical Properties from Miniature Tensile Testing of High Strength Steels." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/4029.
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This Miniature mechanical testing study is concerned with the use of miniature specimens to identify the mechanical properties of stainless steel Type 304, sensitized Type 304 and SA516 Grade 70 carbon steel as a viable replacement for the standard sized mechanical testing. The study aims at obtaining suitable specimen geometry and tensile testing proce- dure for miniature mechanical testing whose mechanical properties are comparable to that of conventional specimens of ASTM A370-10 of the same steel. All specimens are at and the gauge length cross section will be varied to obtain suitable geometry. The miniature tensile testing results are further validated by using Monte Carlo Method (MCM) for uncertainty estimation in order to know the probability distribution of mechanical properties. Miniature specimens with a cross section of 3 mm2 and 12 mm gauge length are found to produce equiva- lent mechanical properties as tested from standard-sized specimens. If a reasonable agreement is received, it will provide us with a very useful tool to evaluate mechanical properties of de- graded materials, which cannot be removed from service for standard testing, for repair and service life evaluation.
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Reutlinger, Christopher George. "Direct pull-out capacity and transfer length of 06-inch diameter prestressing strand in high-performance concrete." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19026.
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Jiao, Hui 1963. "The behaviour of very high strength (VHS) members and welded connections." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9417.
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Shams, Mohamed Khalil. "Time-dependent behavior of high-performance concrete." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20682.
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Wong, Kong-yeung, and 黃剛揚. "Development of high strength concrete for Hong Kong and investigation of their mechanical properties." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213765.
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Chau, Siu-lee, and 周小梨. "Effects of confinement and small axial load on flexural ductility of high-strength reinforced concrete beams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31997661.
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Wong, Hin-cheong Henry, and 黃憲昌. "Effects of water content, packing density and solid surface area on cement paste rheology." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39326032.
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Karlsson, Daniel. "Life and fracture in very high cycle fatigue of a high strength steel." Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-86135.
Повний текст джерелаАнотація:
Classical fatigue models teach that there is an intrinsic fatigue limit for steels, representing a level of stress that is too low for regular crack growth where every cyclic load propagates a fatigue crack through the material. Modern application with extreme lifetimes has shown that fatigue will still take place in steels with stress levels well below the expected fatigue limit. This relatively new area of study has been named Very High Cycle Fatigue, or VHCF, and describes fatigue failures with a number of load cycles exceeding 107. Fractography of steels that has suffered VHCF tends to reveal an especially rough crack surface adjacent to where the fatigue crack originates, which is typically some form of defect in the bulk of the steel. This area is believed to be critical for VHCF and has been referred to in a number of ways by different studies, but will herein be called Fine Granular Area, or FGA. The aim of this study is to try and get a better understanding of VHCF. This was done by fractography analysis of test specimens of high strength tool steel that suffered fatigue failure at lifetimes ranging from about 106 cycles to 1,9x109 cycles. The lower lifetimes were achieved using hydraulic testing equipment, while the specimens in the VHCF range suffered fatigue failure in ultrasonic testing equipment allowing the application of a cyclic stress at a rate of 20 000 Hz. The resulting fracture surfaces were then investigated using a scanning electron microscope, or SEM, taking special note of the fatigue initiating defects and, in the case of VHCF, the rough area found adjacent to it. In combination with the SEM an elemental analysis of the fatigue initiating defects as well as the bulk of the material was done using energy-dispersive X-ray spectroscopy, or EDS. This was done to find out what the defects consisted of; confirming that they were slags and checking that the composition of the material of the bulk of the specimen matches what was expected. Using light optical microscopy in combination with acid etching of the surface of samples cut out of the test specimens the structure of the steel was investigated. Calculating the local stresses at the location of the fatigue initiating defect was done using FEM in combination with displacement amplitude gathered from the ultrasonic testing equipment. The data gathered was then measured and compared to that of previous studies, using models of prediction and seeing how they match the experimental results. The results suggest that the stress intensity factor at the internal slags is critical for VHCF and that with lower stress intensity factors one can expect longer lifetimes. Another observation is a relatively consistent stress intensity factor at the edge of the FGA combined with the original defect, likely signifying the transition from the creation of FGA to traditional crack propagation. There also seems to be a connection between the size of the FGA and the number of cycles to failure, with larger FGA with increasing lifetimes. The most glaring shortcoming of this study is the amount satisfactory tests conducted, and thus amount of data points, is very low due to the majority of specimens suffered failure at the threading used to connect them to the ultrasonic testing equipment at lifetimes far too low to be relevant.Klassiska utmattningsmodeller lär ut att det finns en utmattningsgräns för stål, vilket representerar en spänningsnivå som är för låg för regelbunden sprickväxt där varje cyklisk belastning sprider en utmattningsspricka genom materialet. Moderna applikation med extrema livstider har visat att utmattning fortfarande äger rum i stål med spänningsnivåer långt under den förväntade utmattningsgränsen. Detta relativt nya studieområde har fått namnet Very High Cycle Fatigue, eller VHCF, och beskriver utmattningsfall med ett antal belastningscykler som överstiger 107. Fraktografi av stål som har drabbats av VHCF tenderar att ha en särskilt gropig sprickyta som ligger intill där utmattningssprickan har sitt ursprung, vilket typiskt är någon form av defekt i stålets bulk. Detta område tros vara kritiskt för VHCF och har hänvisats till på ett antal sätt av olika studier, men kommer här att kallas Fine Granular Area eller FGA. Syftet med denna studie är att försöka få en bättre förståelse för VHCF. Detta gjordes genom fraktografianalys av testprover av verktygsstål med hög hållfasthet som drabbades av utmattningsbrott vid livstider från cirka 106 cykler till 1,9x109 cykler. De lägre livslängderna uppnåddes med hjälp av hydraulisk testutrustning, medan proverna i VHCF-området drabbades av utmattningsbrott i ultraljudstestutrustning som klarar att applicera en cyklisk stress med en frekvens på 20 kHz. De resulterande sprickytorna undersöktes sedan med hjälp av ett svepelektronmikroskop, eller SEM, med särskild fokus på utmattningsinitierande defekter och, i fallet med VHCF, det grova området som hittades intill det, FGA. I kombination med SEM utfördes en elementanalys av utmattningsinitierande defekter liksom huvuddelen av materialet med energidispersiv röntgenspektroskopi, eller EDS. Detta gjordes för att ta reda på vad inneslutningarna bestod av för att bekräfta att de var slagg samt kontrollera att sammansättningen av materialet i huvuddelen av provet matchar det som förväntades. Med användning av optisk ljusmikroskopi i kombination med syraetsning av ytan på prover som skars ut ur testproverna undersöktes stålets struktur. Beräkning av de lokala spänningarna på platsen för den utmattningsinitierande defekten gjordes med hjälp av FEM i kombination med förskjutningsamplituden som samlats från ultraljudsutrustningen. De insamlade uppgifterna mättes sedan och jämfördes med tidigare studier genom att använda diverse modeller och se hur de matchar de experimentella resultaten. Resultaten antyder att stressintensitetsfaktorn vid inneslutningarna är kritisk för VHCF och att man med lägre stressintensitetsfaktorer kan förvänta sig längre livstid. En annan observation är en relativt konsekvent stressintensitetsfaktor vid kanten av FGA, vilket sannolikt markerar övergången från skapandet eller utbredning av FGA till traditionell sprickutbredning. Det verkar också finnas en koppling mellan storleken på FGA och antalet cykler till fel, med större FGA med ökande livslängd. Den mest uppenbara bristen i denna studie är mängden tillfredsställande tester som genomförts. Därmed är mängden datapunkter mycket låg, detta på grund av att majoriteten av proverna misslyckades vid gängningen som användes för att ansluta dem till ultraljudstestutrustningen vid livstider alltför låga för att vara relevanta.
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Young, Kieran. "The development and evaluation of a testing protocol to assess upper body pressing strength qualities in high performance athletes." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/554.
Повний текст джерелаАнотація:
PURPOSE: The purpose of this study was to evaluate the reliability of an isometric force assessment (isometric bench press) across 4 standardised angles and an isoinertial force and velocity assessment (ballistic bench throw) utilising a relative load based on a percentage of one repetition maximum (1RM) in the bench press; and to evaluate whether the use of the dynamic strength deficit (DSD) ratio can guide training and detect changes induced by training over a 5 week period.
METHODS: Twenty four elite male athletes (age = 19.9 ± 2.7yrs; mass = 79.1 ± 13.0kg) performed the isometric bench press and a 45% 1RM ballistic bench throw on 2 separate days with 48 hours between testing occasions. Peak force, peak power, peak velocity, peak displacement and peak rate of force development were assessed using a force plate and linear position transducer. Reliability was assessed by Intra- Class Correlation (ICC), Percent Coefficient of Variation (%CV) and Typical Error (TE). The athletes’ DSD ratios were then calculated using the peak force values obtained during the BBT and IBP (DSD = IBP peak force/BBT peak force). Athletes were then placed in to 2 groups as matched-pairs based on their DSD ratio and their strength in the 1RM bench press. The Bench Press (BP) Group performed high intensity bench press while the Ballistic Bench Throw Group performed moderate intensity ballistic bench throws. Both groups trained twice a week for 5 weeks.
RESULTS: All performance measures except for peak rate of force development were considered reliable (ICC = 0.85-0.97, %CV = 1.2-3.3). The DSD ratio was sensitive to the disparate training methods between groups, with the BP Group increasing their IBP peak force (p = 0.035), the BBT Group increasing their bench throw performance (p ≤ 0.001), and as a result, yielding a significant change (p ≤ 0.001) in the DSD for both groups.
CONCLUSIONS: Performance measures such as peak force in the isometric bench press and ballistic bench throw are reliable when assessing upper body pressing strength qualities in elite male athletes. Further, the DSD can be used to detect qualities of relative deficiency and guide specific training interventions based on test results.
19
Peer, Andrea J. "Performance Testing and Modeling of Ultra-High Strength Steel and Complex Stack-Up Resistance Spot Welds." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1493403670252986.
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Walton, Frank Stewart, and University of Lethbridge Faculty of Arts and Science. "Adiabaticity of high strain rate compression testing using the Split Hopkinson Pressure Bar Apparatus." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1997, 1997. http://hdl.handle.net/10133/74.
Повний текст джерелаАнотація:
In the development of explosively formed projectiles (EFPs), researchers are faced with the problem of testing prospective metals at high strain rates. So far it has been assumed that, relative to the cooling time, the deformation time is practically instantaneous indicating that the test is adiabatc: none of the heat generated
within the metal is lost to conduction. In this paper we construct a model that subtracts out the effects of kinetic energy and uses specific heat as a function of temperature. In this way we can focus on the energy change in the specimen that can be attributed to temperature and determine just how adiabatic the high strain rate test is.vi, 74 leaves : ill. ; 28 cm.
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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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Owens, Anthony Taylor Tippur Hareesh V. "Development of a split Hopkinson tension bar for testing stress-strain response of particulate composites under high rates of loading." Auburn, Ala., 2007. http://repo.lib.auburn.edu/Send%2002-04-08/OWENS_ANTHONY_54.pdf.
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Srinivaas, Sujith. "Testing and Analysis of Innovative High-Speed Automotive Fastening System for Multi Materials." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587397193415362.
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Schwicht, Daniel Ethan. "Large-Scale Strength Testing of High-Speed Railway Bridge Embankments: Effects of Cement Treatment and Skew Under Passive Loading." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7346.
Повний текст джерелаАнотація:
To investigate the passive force-displacement relationships provided by a transitional zoned backfill consisting of cement treated aggregate (CTA) and compacted gravel, a series of full-scale lateral abutment load tests were performed. The transitional zoned backfill was designed to minimize differential settlement adjacent to bridge abutments for the California High Speed Rail project. Tests were performed with a 2-D or plane strain backfill geometry to simulate a wide abutment. To investigate the effect of skew angle on the passive force, lateral abutment load tests were also performed with a simulated abutment with skew angles of 30º and 45º. The peak passive force developed was about 2.5 times higher than that predicted with the California HSR design method for granular backfill material with a comparable backwall height and width. The displacement required to develop the peak passive force decreased with skew angle and was somewhat less than for conventional granular backfills. Peak passive force developed with displacements of 3 to 1.8% of the wall height, H in comparison to 3 to 5% of H for conventional granular backfills.The skew angle had less effect on the peak passive force for the transitional backfill than for conventional granular backfills. For example, the passive force reduction factor, Rskew, was only 0.83 and 0.51 for the 30º and 45º skew abutments in comparison to 0.51 and 0.37 for conventional granular backfills. Field measurements suggest that the CTA backfill largely moves with the abutment and does not experience significant heave while shear failure and heaving largely occurs in the granular backfill behind the CTA backfill zone.
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Arakelian, Andrea Katherine. "Strength analysis of bolted shear connections under fire conditions using the finite element approach." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-122208-145717/.
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Ghasemi, Sahar. "Innovative Modular High Performance Lightweight Decks for Accelerated Bridge Construction." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2248.
Повний текст джерелаАнотація:
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, the deck weight was limited to below 21 psf and its overall depth to only 4 inch, while still meeting the strength and ductility demands for 4 ft. typical stringer spacing. It was further envisioned that the ultra-high strength of UHPC is best matched with the high strength of HSS or CFRP reinforcement for an efficient system and the ductile behavior of UHPC can help mask the linear elastic response of CFRP reinforcement and result in an overall ductile system. The issues of consideration from the design and constructability perspectives have included strength and stiffness, bond and development length for the reinforcement, punching shear and panel action. A series of experiments were conducted to help address these issues. Additionally full-size panels were made for testing under heavy vehicle simulator (HVS) at the accelerated pavement testing (APT) facility in Gainesville. Detailed finite element analyses were also carried out to help guide the design of this new generation of bridge decks. The research has confirmed the superior performance of the new deck system and its feasibility.
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Moravčík, Igor. "Metal Matrix Composites Prepared by Powder Metallurgy Route." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-367507.
Повний текст джерелаАнотація:
Ve všeobecnosti, poznatky o design slitin, jejich výrobě a výběru legujúcich prvků sú omezené na slitiny s jedním základním prvkem. Tento fakt ale výrazně limituje možnosti a volnost výběru prvků pro dosáhnuti speciálních vlastností a mikrostruktur. V poslední dekádě se ukázalo, že materiálová věda a inženýrství nejsou ještě zdaleka prozkoumané v důsledku objevu nové třídy materiálů nazvané vysoko entropické slitiny (HEA high entropy alloys). Jejich objev upoutal pozornost vědecké komunity. Základní koncept pro jejich design je, že namísto jednoho, nebo dvou základních prvků obsahují minimálně 5 prvků v podobných atomových koncentracích. V posledních letech se objevila skupina materiálů odvozená od HEA, nazvaná slitiny so střednou entropii (MEA medium entropy alloys). Na rozdíl od HEA ale obsahují 3, nebo 4 prvky. Táto práce je věnovaná studiu přípravy a charakterizaci HEA, MEA a jejich kompozitů s pomocí metod práškové metalurgie. V této práci byli dohromady zkoumány tři kompozice: AlCoCrFeNiTi0.5, Co1.5Ni1.5CrFeTi0.5 a CoCrNi, kompozity s kovovou matricí (MMC metal matrix composites) vyztužené částicemi B4C s CoCrNi jako matricí. Hloubková mikrostrukturní a mechanická analýza těchto materiálů byla provedena pomoví metod rastrovací a transmisní elektronové mikroskopie spojené s tahovými a ohybovými zkouškami. V průběhu celé studie se objevovaly problémy s kontaminací kyslíkem, co se projevilo vznikem značného množství oxidů v připravených materiálech. U Slitiny AlCoCrFeNiTi0.5 byla naměřena tvrdost přesahující 800 HV. Její houževnatost ale byla velice omezena. V její mikrostruktuře byly identifikovány částice in-situ TiC v důsledku přítomnosti organického, anti-aglomeračního činidla (metanolu) v mlecí misce. Tato reakce může být použita v budoucnu k přípravě MMC se záměrnou disperzí TiC. Na druhé straně, slitina CoCrNi ukázala vysoké hodnoty tažnosti (26%) a meze pevnosti přes 1000 MPa. Mikrostruktura obsahovala majoritní FCC fázi s BCC precipitáty. Tahle slitina byla z důvodu vysoké tažnosti zvolena pro přípravu kompozitu s výztuží B4C. V průběhu slinování ale došlo k reakci mezi přítomným Cr a B4C, které výsledkem byl Cr5B3 borid. Tento kompozit mel pevnost v tahu 1400 MP a extrémne jemnozrnnou strukturu. Celková tažnost ale klesla na 1.9 %. Slitina AlCoCrFeNiTi0.5, která mela strukturu složenou jen z FCC tuhého roztoku dosáhla nejlepší kombinaci mechanických vlastností s pevností přesahující 1300 MPa a dostatečnou tažností 4%. Prášková metalurgie se ukázala jako vhodná metoda pro přípravu HEA a MEA slitin a jejich kompozitů, s dobrou kombinací pevnosti a tažnosti. Tato metoda dovoluje měnit mikrostrukturní parametry připravených materiálů jednoduchou úpravou parametrů procesu.
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Silva, Marina Stella Bello. "Análise morfológica e da resistência adesiva dos tecidos dentais duros irradiados com lasers de pulsos ultracurtos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-21092011-162853/.
Повний текст джерелаАнотація:
O desenvolvimento da Odontologia Restauradora culminou com a era das restaurações estéticas adesivas e da intervenção minimamente invasiva, para as quais técnicas inovadoras e materiais de última geração vêm sendo constantemente introduzidos. As técnicas conservadoras visam não somente a remoção do substrato dental cariado, mas também o preparo das paredes da cavidade para a realização da restauração adesiva. Este estudo visou avaliar a possibilidade de introdução dos lasers de pulsos ultracurtos na Odontologia Restauradora, com o intuito de suprir os requisitos básicos para a realização de uma restauração conservadora adequada. A intenção foi de manter os benefícios já conhecidos relacionados à remoção seletiva de cárie com os lasers de alta potência, bem como superar as desvantagens relacionadas às fontes lasers atualmente disponíveis para este fim, como aumento excessivo de temperatura e adesão prejudicada da superfície irradiada à resina composta. Para a melhor avaliação da interação entre os lasers de pulsos ultracurtos e o substrato dental, os experimentos foram realizados em três fases. A Fase 1 visou avaliar o efeito de diferentes comprimentos de onda (355 nm, 532 nm, 1045 nm e 1064 nm), durações de pulso (pico e femtossegundos) e protocolos de irradiação (velocidade de escaneamento da superfície, espessura do espécime, método de refrigeração e taxa de repetição de pulso) em esmalte e dentina. Para a Fase 2, os parâmetros de irradiação que apresentaram resultados mais favoráveis na Fase 1 foram analisados para relacionar o aumento de temperatura com a taxa de ablação e a eficiência de ablação para cada parâmetro. A Fase 3 teve como objetivo analisar a interface adesiva e os valores de microtração da dentina irradiada com os parâmetros selecionados e estudados na Fase 2, utilizando sistemas adesivos do tipo condicione e lave e autocondicionante com diferentes protocolos de adesão (Clearfil SE Bond com e sem Primer, Adper Single Bond com e sem condicionamento ácido). Os resultados obtidos na Fase 1 indicam que a dentina e o esmalte irradiados com lasers de femtossegundos de 1045 nm e picossegundos de 1064 nm apresentam superfície rugosa livre de carbonização. Os protocolos de irradiação selecionados mostram que a irradiação deve ser conduzida com maior velocidade de escaneamento da superfície, e não há necessidade de refrigeração durante a irradiação. Todos os parâmetros utilizados promoveram ablação seletiva do substrato dental, e apresentaram maior taxa de ablação para dentina que para esmalte. A Fase 2 permitiu observar que todos os parâmetros de irradiação selecionados não provocaram aumento de temperatura maior que 6,1 ºC para esmalte e 4,6 ºC para dentina, quando o aumento de temperatura foi aferido no lado oposto ao irradiado, em espécimes de 1 mm de espessura e sem refrigeração. Exceção foi observada para a maior potência do laser de picossegundos, para a qual a temperatura aumentou até 12 ºC em esmalte e 15 ºC em dentina. Os valores obtidos no ensaio de microtração variaram de acordo com os parâmetros de irradiação e o sistema adesivo. A adesão à dentina irradiada com lasers de pulsos ultracurtos apresentou valores de resistência adesiva semelhantes ou significantemente maiores que os obtidos nos grupos controle, para todos os parâmetros de irradiação selecionados. Os resultados obtidos neste estudo indicam que os lasers de pulsos ultracurtos apresentaram resultados favoráveis para o preparo cavitário em esmalte e dentina em relação à morfologia produzida na superfície e ao aumento de temperatura provocado durante a irradiação. A resistência adesiva à dentina irradiada foi semelhante, ou mesmo significantemente maior que a obtida nos grupos controle. Portanto, os lasers de pulsos ultracurtos são considerados uma técnica promissora para a realização de intervenção minimamente invasiva com lasers de alta potência.The development of restorative dentistry has reached the era of esthetic adhesive restorations and minimally invasive approach, for which innovative techniques and advanced materials are constantly introduced. Conservative techniques aim not only to remove carious dental substrate, but also to prepare cavity surfaces for adhesive restoration. The main objective of this study was to evaluate the possibility of introducing ultra-short pulsed lasers in Restorative Dentistry, in attempt to fulfill the basic requirements of adequate conservative restoration, by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages related to current laser sources available for this purpose, such as temperature increase and damaged adhesion to resin composite. In order to better evaluate the interaction between ultra-short pulsed lasers and dental substrates, experimental procedures were divided in three phases. Phase 1 aimed to evaluate the effect of different wavelengths (355 nm, 532 nm, 1,045 nm, and 1,064 nm), pulse durations (pico and femtoseconds) and irradiation protocols (surface scanning speed, sample thickness, cooling method, pulse repetition rate) on enamel and dentin. For Phase 2, laser parameters with most favorable results in Phase 1 were evaluated to relate temperature increase to ablation rate or ablation efficiency. Phase 3 aimed to analyze adhesive interface and microtensile bond strength to dentin irradiated with the selected parameters by using etch-and-rinse and self-etch adhesive systems with different bonding protocols (Clearfil SE Bond with and without Primer, Adper Single Bond with and without acid etching). The results of Phase 1 indicate that dentin and enamel irradiated with 1,045-nm fs-laser and 1,064-nm ps-laser present a rough surface without carbonization. Irradiation should be conducted with higher scanning speed, and no additional cooling during irradiation was necessary. All parameters provided selective tissue ablation, with higher ablations rate for dentin than enamel. Phase 2 indicated that all parameters tested provoked temperature increase of up to 6.1 ºC for enamel and 4.6 ºC for dentin, when temperature increase was measured at the back side of 1-mm thick samples without cooling during irradiation, except for higher power for ps-laser, for which temperature increased up to 12 ºC for enamel and 15 ºC for dentin. Microtensile bond strength values varied according to laser parameters and adhesive systems used. Adhesion to dentin irradiated with ultra-short pulsed lasers resulted in similar or significantly higher bond strength values than control groups, for all laser parameters analyzed. Based on the results of this study, ultra-short pulsed lasers presented favorable results for cavity preparation in dentin and enamel regarding surface morphology and temperature increase. Adhesion to irradiated dentin was either similar or superior to traditional techniques. Thus, ultra-short pulsed lasers are considered a promising technique for the promotion of laser-supported minimally invasive approach.
29
Procházka, David. "Vytvoření předpokladů pro hodnocení vlastností vysokopevnostních betonů s využitím nedestruktivních metod zkoušení." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-233795.
Повний текст джерелаАнотація:
High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
30
Bourlet, Clément. "Développement de la fabrication additive par procédé arc-fil pour les aciers : caractérisation microstructurale et mécanique des dépôts en nuances ER100 et 316L pour la validation des propriétés d'emploi de pièces industrielles." Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0058.
Повний текст джерелаАнотація:
L'arc-fil est un nouveau procédé de fabrication additive utilisant une cellule desoudage robotisée pour la fabrication, couche par couche, de pièces de grandes dimensions. Ilpermet de réaliser des ébauches de pièces unitaires ou de petites séries avec des coûts et desdélais de fabrication réduits. Les premiers développements se sont principalement orientés sur laréalisation de pièces à forte valeur ajoutée en alliage de titane et d’aluminium pour le secteuraéronautique et aérospatial, et intéressent maintenant d’autres secteurs tels que les industriesnavales, pétrolières, ferroviaires et mécaniques utilisant des aciers. Ce travail propose uneméthodologie de sélection des paramètres et des stratégies de dépôts, avec le contrôle final despièces fabriquées. Il porte sur deux matériaux : un acier C-Mn à haute limite d’élasticité(ER100) et un acier inoxydable austénitique (316LSi). Le résultat des caractérisations permetd’établir le lien entre les conditions de fabrication, les dimensions géométriques et les propriétésmicrostructurales et mécaniques des pièces obtenues, ce qui conduit au final à une démarchepermettant de faire évoluer le procédé vers l’industrialisationWire-arc additive manufacturing is a new process using a common weldingrobotic cell to build large parts layer by layer. It allows building rough single pieces orsmall series parts with a low cost and a short delay. First developments were done ontitanium and aluminum parts for aeronautic and space applications, but more industriessuch as maritime, oil and gas, railway…are now interested into it. In this work, amethodology is proposed to define suitable process parameters and deposit’s strategies,with the final control of the elaborated parts. Developments are done on both highstrength steel ER100 and austenitic stainless steel 316LSi. The results of theexperimental characterisation enable to show the relations between the manufacturingconditions, the dimensions, the microstructure and the mechanicals properties of theparts, and finally lead to guidelines to evolve the wire-arc additive manufacturingtowards industrialisation
31
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.
Повний текст джерелаАнотація:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorA 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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HUANG, PO-CHIA, and 黃柏嘉. "Seismic Testing of High-Strength Reinforced Concrete Exterior Beam-Column-slab connections." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/49818516948465088936.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
營建工程系
104
To study the degradation of joint shear strength, this paper designed four New RC exterior beam-column connections with slabs and transverse beams covers 2/3 or 3/4 width of the joint face using current codes. Four beam-column connections were made with 70 MPa concrete, SD685 longitudinal reinforcement and SD785 transverse reinforcement. Test results showed that the current ACI 318 code is conservative. The transverse beams which covered 2/3 width of the joint face still had some confining effect to enhance the joint shear strength. Typical pushover analysis use beam-column centerline models with rigid joints, which may get unconservative results. This paper also presents nonlinear modeling of the joint with two equivalent compression struts using a commercial structural analysis tool. Following the recommendations of ASCE 41 and ACI 369, the joint keep elastic if the shear demand is less than the nominal shear strength. This paper propose to model the joint shear failure after beam yielding. Using empirical formula obtained by prior database investigation, the joint nonlinear springs are adjusted according to the prediction of failure mode. The proposed skills can improve the results of pushover analysis and well predict the envelopes for the cyclic loading test results. Further calibration and verification of the modeling parameters are recommended to widely use in practice.
33
Liu, Wen-hao, and 柳文皓. "Seismic Testing of High-Strength Reinforced Concrete Interior Beam-Colunm-slab connections." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/z9fj97.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
營建工程系
104
For high-rise buildings, columns made of normal-strength reinforced concrete have large cross-sectional dimensions which cannot be accepted by end users. Using high-strength reinforcement and concrete have many advantages, including smaller member sizes, lighter structure elements, lesser steel reinforcement, longer span capability, and more space available for end users. This paper presents experiments of the sub-project “behavior, design, and modeling of new RC frame joints subjected to seismic loading” in the Taiwan New RC Project. Four new RC interior beam-column connections with transverse beams and slabs were tested according to the acceptance criteria for moment frames, evaluating the effect of transverse beams covers 1/2 or 3/4 width of the joint face. The degradation of the joint shear strength is also investigated. Four beam-column connection specimens were made with 100-MPa concrete, SD685 longitudinal reinforcement, and SD785 transverse reinforcement. Two connection specimens have precast concrete units with cast-in-place concrete joint and slabs, while the other two specimens are monolithic beam-column-slab connections. Test results show that the precast beams and columns with cast-in-place concrete joint perform as well as expected for seismic design of moment frames. Test results shows that the 1/2-column-width-wide transverse beams still have partial confinement effect. It is recommended that the nominal joint strength between calculated by linear interpolation between 1.25√(f_c^' ) MPa(15√(f_c^' ) psi) and 1.67√(f_c^' ) MPa(20√(f_c^' ) psi) for transverse beams cover 1/2 and 3/4 width of the column, respectively.
34
Kgomari, Lerato Criscelda. "Microstructural characterization of laser formed high-strength-low-alloy (HSLA) steel." Thesis, 2010. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000591.
Повний текст джерелаАнотація:
Thesis (MTech. : Engineering Metallurgy.)--Tshwane University of Technology, 2010.Establish a qualitative and quantitative comparison between the parameters of the laser used in manufacturing a 120 mm curvature in HSLA steel parts and the micro-structural changes in the steel part. Subsequently, the final microstructure will be used to determine the reason for the poor fatigue performance of the HSLA steel after laser forming.
35
Hsu, Shu-Pu, and 許舒普. "Investigation on the slenderness ratio(s/db) of high strength rebar by means of low cycle fatigue testing." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/22992523473797765289.
Повний текст джерелаАнотація:
碩士國立中央大學
土木工程學系
105
The purpose of the study is to discuss the moderate anti-buckle spacing of SD790/690 rebar. This is because the present standard only specifies the spacing of transverse reinforcement for SD420 bars. Thus, the experiment used the universal testing machine with different bar slenderness ratio to simulate the column components subjected to earthquake loading. Test specimens adopted 16mm and13mm diameter (common strength SD420 & high strength SD790). That is, SD690 bars normally used for larger diameter like D25 are not available to the testing machine at present. Therefore, SD790-D13 and SD420-D13 bars with different slenderness(s/db =5.5、6) and different amplitudes(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%), and SD790-D16 and SD420-D16 bars with different spacing(s/db =4.5、5、6) and different amplitudes(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%), are provided for the testing. By means of a series of test program, some parameters such as the number of life cycles, behavior of bar fracture and suitable bar slenderness ratio under the cyclic loading will be found. Test results show the load difference between the first cycle and the final cycle for SD790 bars is smaller than that for SD420 bars. However, the SD790 bars are fractured without warning, and the breaking surface is smooth. This article also analyzes the rebars anti-buckling spacing by measuring the effective length coefficient(k) and non-linear steel modulus(Et) of the testing bars. Thus the slenderness ratio(s/db) of anti-buckling spacing for the rebars can be calculated. It repeals the SD420 bars of s/db shall be smaller than 6 as recent ACI318 suggested. The SD790 bars of slender ratio shall be less than 4.Therefore, the SD690 bars normally used for New RC main bars shall be less than 5.
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Clark, W. S. "Axial load capacity of circular steel tube columns filled with high strength concrete." Thesis, 1994. https://vuir.vu.edu.au/18153/.
Повний текст джерелаАнотація:
This study examines the axial load capacity of circular Concrete Filled Steel Tube
columns using High Strength Concrete (CFST-HSC). Emphasis is drawn to the
enhanced axial capacity of short columns attributed to the lateral confinement of the
concrete infill provided by the steel encasement. The degree of confinement has been
found to be dependent on several geometric and mechanical parameters. At present,
significant discrepancies exist with respect to quantifying the effective strength confined concrete. Existing design models and codes are predominantly derived from
the characteristics of normal strength concrete and therefore may be inappropriate concrete filled steel columns utilising High Strength Concrete (HSC).
An extensive experimental program was initiated to examine the axial capacity of
CFST-HSC columns. The results of 62 concentrically loaded scale model columns filled
with High Strength Concrete (46-100 MPa) are presented. The principal experimental
parameters were concrete and steel strengths, tube diameter to wall thickness ratio, column slenderness ratio. The columns tested were classified as short thin walled
sections and were tested as isolated column elements under short term loading. The
results are compared with the predictions of several existing design procedures and
recommendations are proposed.
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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.
Повний текст джерела
38
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.
Повний текст джерелаАнотація:
"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
39
Chen, Guan-Wei, and 陳冠維. "Cyclic Testing and Backbone Curve Development of High-Strength Steel Built-up Box Columns under Lateral Drifts and Axial Loads." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/nstn3t.
Повний текст джерелаАнотація:
碩士國立臺灣大學
土木工程學研究所
107
The seismic behavior of the high strength steel hollow box column (high strength HBC) under the high axial load was experimentally investigated. The parameters in this study included the width-to-thickness (b/t) ratio, axial load level and loading types. Full-size tests were carried out on six welded box-section columns fabricated from SM570MC (nominal yield strength 420 MPa~ 540 MPa). The HBC specimens were 290 to 400 mm in width and 4000 mm in height, with nominal b/t ratios varied from 11 to 21. The HBC specimens were tested under a constant axial load and the increasing cyclic loading (or near-fault loading). Experimental results indicate that smaller b/t ratio in HBC can delay the local buckling effectively, resulting in better ductility. Moreover, the width-thickness limit for HBC in Taiwanese specification, which is 21, can not apply to the cases under a high axial load. This means the smaller b/t requirement of highly ductile member (λhd=12.9) in AISC 341 (2016) should be used in the seismic design. Also, loading sequence for beam-to-column moment connections based on AISC 341 (2016) is stricter than the near-fault loading that we used in this work. All the design codes include AISC-LRFD(2016), AIJ(2010) and Taiwanese Code(2010) are conservative in predicting the flexural strength of high strength HBC. In this work, the backbone curve for hollow section steel column was proposed and compared with those proposed by ASCE 41 (2013) and NIST (2017). It shows that the backbone curves proposed by ASCE 41 (2013) and NIST (2017) will underestimate the flexural strength and the plastic rotation under a high axial load (40%Py). The backbone curve proposed by this work can give good accuracy in predicting the flexural strength and the plastic rotation of high strength HBC.