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1
GUPTA, ARUN KUMAR. "DETERMINATION OF SEISMIC PARAMETER OF RCC TALL BUILDING USING SHEAR CORE , SHEAR WALL AND SHEAR CORE WITH OUTRIGGER." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18840.
Повний текст джерелаАнотація:
This report covers the detailed explanation about the determination of seismic parameter of
RCC tall building using shear core, shear wall and shear core with outrigger. Building are
subjected to various loads such as dead load, live load ,wind load and seismic load. Seismic
load has extreme adverse effect on building so it is necessary to perform seismic analysis This
paper describe about the response of building when it is subjected to seismic load , this
response can be shown by story drift and base shear. Seismic analysis has been performed on
(G+30) building which is located in zone 4 using ETABS software. Analysis has been
performed according to IS 1893 PART 1 (2016). This paper gives total rule to manual as wells
programming examination of seismic coefficient technique.
2
Peterson, James B. "Comparison of Analysis and Optimization Methods for Core-Megacolumn-Outrigger Skyscrapers." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2834.
Повний текст джерелаАнотація:
The goal of this research is to compare performance of three analysis methods and three optimization methods for core-megacolumn-outrigger, or CMO skyscrapers. The three analysis methods include a 1D stick analysis, 2D frame analysis, and 3D finite element analysis. The three optimization methods include a trial and error optimization, optimality criteria optimization, and genetic algorithm. Each of these methods was compared by applying an example CMO skyscraper. The 1D stick analysis proved to be the most accurate when compared with the 3D finite element results. The genetic algorithm was recommended as the best optimization method in this research. The 1D stick method in this thesis introduces a new analysis involving an outrigger modification factor. The comparison of these optimization methods for skyscrapers has not been reported in the literature.
3
Alanazi, Abdulaziz Manqal. "The Use of Core and Outrigger Systems for High-Rise Steel Structures." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1576180826759645.
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4
Zhang, Hong Dong. "Shear lag in tube-in-tube structures coupled with outrigger and belt trusses." Thesis, University of Macau, 2003. http://umaclib3.umac.mo/record=b1636335.
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DEASON, JEREMY THOMAS. "SEISMIC DESIGN OF CONNECTIONS BETWEEN STEEL OUTRIGGER BEAMS AND REINFORCED CONCRETE WALLS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1021661255.
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6
Roberts, Ryan (Ryan M. ). "Shear lag in truss core sandwich beams." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32935.
Повний текст джерелаАнотація:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaf 30).
An experimental study was conducted to investigate the possible influence of shear lag in the discrepancy between the theoretical and measured stiffness of truss core sandwich beams. In previous studies, the measured values of stiffness in loading have proven to be 50% of the theoretical stiffness during three point bending tests. To test the effect of shear lag on this phenomenon, the beams' dimensions were altered to decrease the presence of shear lag in a gradual manner so a trend could be observed. The experimental trails were carried out on three types of beams each with different diameters of truss material. Results show that this study has improved the accuracy of the measured results from previous studies with the two smallest truss diameter beams. Because the discrepancy between the theoretical and measured values is the greatest for the largest beams, (when the shear deflection has the least influence), it is concluded that shear lag is not responsible for the discrepancy between measured and theoretical stiffness.
by Ryan Roberts.
S.B.
7
Noury, Philippe. "Shear crack initiation and propagation in foam core sandwich structures." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326642.
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8
Paulino, Madison Radhames. "Preliminary Design of Tall Buildings." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/239.
Повний текст джерелаАнотація:
Techniques for preliminary analysis of various tall building systems subjected to lateral loads have been studied herein. Three computer programs written in Matlab® graphical user interface language for use on any personal computer are presented. Two of these programs incorporate interactive graphics. A program called Wall_Frame_2D is introduced for two-dimensional analysis of shear wall-frame interactive structures, using the shear-flexural cantilever analogy. The rigid outrigger approach was utilized to develop a program called Outrigger Program to analyze multi-outrigger braced tall buildings. In addition, a program called Frame Tube was developed which allows analysis of single and quad-bundled framed tube structures. The tube grids are replaced with an equivalent orthotropic plate, and the governing differential equations are solved in closed form. Results for lateral deflections, rotations, and moment, shear, and torque distributions within the various resisting elements are compared against other preliminary and "exact" matrix analysis methods for several examples. SAP2000 was used to obtain "exact" results. The approximate analyses are found to give reasonable results and a fairly good indication of the behavior of the actual structure. These programs are proposed for inclusion in a knowledge-based approach to preliminary tall building design. The tall building design process is outlined and criteria are given for the incorporation of these "Resource Level Knowledge Modules" into an integrated tall building design system.
9
TUNC, GOKHAN. "RC/COMPOSITE WALL-STEEL FRAME HYBRID BUILDINGS WITH CONNECTIONS AND SYSTEM BEHAVIOR." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1020441384.
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10
鄺君尚 and Jun-shang Kuang. "Elastic and elasto-plastic analysis of shear wall and core wall structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B3123155X.
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11
梁少江 and Siu-kong Leung. "Analysis of shear/core wall structures using a linear moment beam-typeelement." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213352.
Повний текст джерела
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Kuang, Jun-shang. "Elastic and elasto-plastic analysis of shear wall and core wall structures /." [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12428565.
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13
Yun, Samuel. "Mechanical Analysis of a Detachment Shear Zone, Picacho Mountains Metamorphic Core Complex (AZ)." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10814249.
Повний текст джерелаАнотація:
On I-10 between Tuscon, AZ, and Phoenix, AZ, is the Picacho Mountains Metamorphic Core Complex (MCC). The Picacho Mountains MCC represents the northwest of the Greater Catalina MCC which includes Tortolita, Santa Catalina, and Rincon Mountains. To the immediate south of I-10 is Picacho Peak, an early Miocene andesitic volcanic center, and opposite of Picacho Peak are the granitic Picacho Mountains. The detachment shear zone (DSZ) is well exposed at Hill 2437. The mylonitic DSZ is separated into an upper, middle, and lower plate by two detachment faults. The DSZ is estimated to have undergone deformation at ~500?C based on recrystallized quartz microstructures and a previous thermochronologic study by previous graduate student Maxwell Schaper. We obtained an average flow stress of 43 ? 9 MPa using a quartz paleopiezometer by Stipp and Tullis (2003). Using a flow law by Hirth et al. (2001), we found strain rate values between 10-13 and 10-12 s-1. Grain size analysis indicates that quartz recrystallized grains have relatively moderate aspect ratio (1.55 < Rf < 1.87) which correlates to small amount of finite strain (1.13 < Rs < 1.33). Results from vorticity analysis based on the recrystallized quartz grain shape foliation method reveals that quartz was deformed under ~60% pure shear and ~40% simple shear (0.48 < Wm < 0.70, assuming plane strain), and the DSZ experienced ~18% of shortening perpendicular to mylonitic foliation, and up to ~22% of stretching parallel to the flow plane up. We found that despite high strain rate values and evidence of high strain rate (e.g. undulose extinction in quartz, chessboard structures, cataclasites, and possible pseudotachylytes), this is not reflected in the amount of finite strain recorded by the mylonitic DSZ.
14
Leung, Siu-kong. "Analysis of shear/core wall structures using a linear moment beam-type element /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18155376.
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15
Lindwall, Caroline, and Jonas Wester. "Modelling Lateral Stability of Prefabricated Concrete Structures." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188586.
Повний текст джерелаАнотація:
Stability calculations of prefabricated concrete structures with help of FEM-tools demand knowledge about how the elements are related to each other. This thesis concerns how joints between building elements affect the results when modelling prefabricated concrete structures, with demarcation to joints between hollow core (HC) slabs and between solid wall elements. The thesis also covers how the properties of the floor can be adjusted to account for the effects of the joints without modelling every single element. The work started by measuring the deflection of 10 HC-slabs jointed together and loaded in-plane acting as a deep beam, in a FE-model made with Robot™, from Autodesk®. The joints between the HC-elements were modelled either rigid or elastic, and the cross-section and the length of the HC-elements were varied. The linear elastic stiffness between the HC-elements was obtained from the literature as 0.05 (GN/m)/m. The results showed that a changed cross-section geometry gave greater differences in deformation than a changed length. The in-plane shear modulus was then adjusted for the HC-elements in the rigid cases until the same deflection was achieved as for the elastic cases. The result showed that the shear modulus in average for the different cross-section geometries and lengths had to be reduced with a factor of 0.1 to account for the joints. Based on the geometry of a castellated joint between prefabricated solid concrete walls, a calculation model was developed for its linear elastic stiffness. The result was a stiffness of 1.86 (GN/m)/m. To verify the calculated stiffness, a FE-model was developed consisting of a 30m high wall, loaded horizontally in-plane and with one or two vertical joints where the stiffness was applied. The deflection and the reaction forces were noted and the result from the calculated stiffness was compared to other stiffnesses and assessed reasonable. The reaction forces were shown to depend on the stiffness of the joint. The reduced in-plane shear modulus of the HC-elements and the calculated stiffness of the wall joints were then used in a FE-model of a 10-storey building stabilised by two units. The vertical reaction forces were analysed and the results showed 0.02 % difference in the reaction forces in the stabilising units when consideration of the joints between the HC-elements were taken into account and 0.09 % when the vertical joints in the shear wall were taken into account. The results for the wall joint differed from the results when only the wall was modelled. This was thought to be a result of that the floors counteract the shear deformations in the wall joints. The influence of the floor joints was not significant for the building considered in this thesis, but for buildings with non-continuous configuration of the stiffness in the shear walls the outcome may be another, in these cases the reduction factor may be useful.Vid stabilitetsberäkningar av prefabricerade betongstommar med hjälp av FEM-verktyg ställs krav på kunskap om hur elementen förhåller sig till varandra. Detta arbete berör hur fogar mellan byggnadselement påverkar modellering av prefabricerade betongstommar med avgränsning till fogar mellan håldäckselement och mellan solida väggelement. Arbetet berör även en studie i hur ett bjälklags egenskaper kan justeras så att fogarnas effekt kan tillvaratas utan att modellera varje enskilt håldäckselement. Arbetet inleddes med att utböjningen analyserades hos 10 st ihopskarvade håldäckselement, lastade i dess plan likt en hög balk, i en FE-modell skapad i programmet Robot™, från Autodesk®. Fogarna mellan håldäcken modellerades som antingen rigida eller elastiska och håldäckens tvärsnittsgeometri och längd varierades under testet. Den linjära styvheten mellan håldäcken togs från litteraturen som 0.05 (GN/m)/m. Resultatet visade att ändrad tvärsnittsgeometri gav större skillnader för deformationen än varierad längd på håldäcken. Håldäckens skjuvmodul justerades sedan i dess plan för de rigida testen tills dess att de uppnådde samma utböjning som de elastiska. Resultatet visade att skjuvmodulen behövdes reduceras med en faktor 0.1, i medeltal för de olika tvärsnittsgeometrierna och håldäckslängderna. Utefter geometrin på en fog med förtagningar mellan prefabricerade väggar togs en beräkningsmodell fram för den linjärelastiska styvheten i väggfogarna. Resultatet blev en styvhet på 1.86 (GN/m)/m. För att verifiera den beräknade styvheten togs en FE-modell fram bestående av en 30m hög vägg lastad horisontellt i dess plan med en eller två vertikala fogar där en linjär styvhet applicerades. Utböjningen samt reaktionskrafterna noterades, resultatet för den uträknade linjära styvheten jämfördes med andra styvheter och bedömdes utifrån detta vara rimlig. Reaktionskrafterna visade sig vara beroende av styvheten på fogen. Den sänkta skjuvmodulen för håldäcken och den beräknade linjära elasticiteten för väggarna användes sedan i en FE-modell av en 10-våningsbyggnad med två stabiliserande enheter där de vertikala reaktionskrafterna analyserades. Resultatet visade att endast 0.02 procentenheter skiljer reaktionskrafterna i de stabiliserande enheterna då hänsyn tas till fogarna mellan håldäcken och 0.09 procentenheter då hänsyn tas till fogarna mellan väggarna. Resultatet skiljer sig från när endast väggen modellerades, vilket tros bero på att bjälklaget hjälper till att motverka deformationer i väggfogarna. Fogen mellan bjälklagselementen tros kunna ha större inverkan på en byggnad med stabiliserande enheter som drastiskt ändrar styvhet från ett plan till ett annat, i dessa fall kan den framtagna reduktionsfaktorn vara av nytta.
16
Fiszman, Nicolas. "Study of the average shear velocity of the inner-core of the earth using isolation filters." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/52999.
Повний текст джерела
17
Vailhé, Christophe N. P. "Deformation mechanisms in B2 aluminides: shear faults and dislocation core structures in FeAl, NiAl, CoAl and FeNiAl." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/38075.
Повний текст джерела
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Vailhé, Christophe N. P. "Deformation mechanisms in B2 aluminides : shear faults and dislocation core structures in FeAl, NiAl, CoAl and FeNiAl /." This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-154448/.
Повний текст джерела
19
Asia, Winifred. "An in-vitro study of the physical properties of core build-up materials." University of the Western Cape, 2017. http://hdl.handle.net/11394/6307.
Повний текст джерелаАнотація:
Magister Chirurgiae Dentium - MChD (Prosthodontics)The aim of this study was to evaluate and compare the physical properties of two core build-up materials (ParaCore and CoreXflow) and compare this to conventional composite material (Filtek Supreme Plus and SDR Flow) used as core build-up material.
20
Cuenca, Asensio Estefanía. "ON SHEAR BEHAVIOR OF STRUCTURAL ELEMENTS MADE OF STEEL FIBER REINFORCED CONCRETE." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/18326.
Повний текст джерелаАнотація:
Cuenca Asensio, E. (2012). ON SHEAR BEHAVIOR OF STRUCTURAL ELEMENTS MADE OF STEEL FIBER REINFORCED CONCRETE [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18326Palancia
21
Mirza, Adeel R. "Evaluation of AISC Steel Coupling Beam Embedment Length in Composite Ordinary Shear Walls." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543577095290297.
Повний текст джерела
22
Torres, Ivan Francisco Ruiz. "Efeito da deformação por cortante no cálculo de edifícios de andares múltiplos com núcleos estruturais." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-13122017-154253/.
Повний текст джерелаАнотація:
O principal objetivo deste trabalho é realizar a análise estrutural de edifícios de andares múltiplos que apresentam núcleos resistentes, considerando a deformação pelo esforço cortante nos mesmos, bem como nos pilares. Para atingir esse objetivo, será preciso que o comportamento à flexão dos elementos verticais de contraventamento passe a ser regido pela teoria de barras de Timoshenko e não mais pela de Euler-Bernoulli. Foram então desenvolvidos algoritmos que, utilizando o Método dos Elementos Finitos (MEF), permitem calcular os fatores de forma de quaisquer seções transversais abertas de paredes delgadas pertencentes a núcleos estruturais, bem como a distribuição da tensão de cisalhamento na seção transversa em função do esforço cortante atuante. As alterações acima descritas foram feitas em um programa de análise de edifícios denominado CEASO 01, de autoria de MATIAS JR (1997). Embora esse programa realize análise não-linear geométrica, a consideração da deformação por cortante só foi implementada na análise linear. Apresentam-se, ao final, exemplos numéricos que permitem avaliar a influência da deformação pelo esforço cortante sobre os deslocamentos e esforços de núcleos resistentes e pilares.The main aim of this work is to perform structural analysis of multistory buildings with resistant cores, taking into account shear deformation in those elements, as well as in columns. To achieve this objective, the flexural behaviour of vertical elements must be governed by Timoshenko beam theory, rather than the Euler-Bernoulli theory. Procedures using the finite element method (FEM) were developped, which enable to evaluate shear correction factors of generic thin-walled open sections and shear stress distribution as a function of the shear resultant. Changes described above were made in a structural analysis program named CEASO 01, whose author is MATIAS JR (1997). Even though this program is able to perform nonlinear analysis, only in linear analysis the effect of shear deformation is taken into account. Numerical examples are provided, which enable to evaluate the influence of taking into account shear deformation on displacements and stress resultants of resistant cores and columns.
23
Kunwar, Sushil. "Comprehensive Evaluation of Composite Core Walls for Low-Seismic Force and Wind Load Applications." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613750905724949.
Повний текст джерела
24
Woods, Lisa Joy. "The significance of negative bending moments in the seismic performance of hollow-core flooring." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2008. http://hdl.handle.net/10092/2042.
Повний текст джерелаАнотація:
Hollow-core flooring units are designed as simply supported members. However, frequently in construction, continuity is established between the units and supporting structure by the addition of insitu topping concrete and steel reinforcement. This change in structural form can result in negative bending moments and axial forces being induced in the floor by seismic and other structural actions. Significant negative moments are induced by load combinations that include the effects of seismic forces due to vertical ground motion. The focus of this research was two failure mechanisms possible under these loading conditions, a flexural failure and a shear failure. Both failure mechanisms were investigated analytically and experimentally.
A brittle flexural failure was observed experimentally in a sub assembly test that contained starter bars and mesh reinforcement in the insitu topping concrete. The failure occurred at loads lower than those predicted using standard flexural theory. It appears that, due to the prestressing and low reinforcement ratio of the topping concrete, the assumption that plane sections remain plane is not appropriate for this situation. It is proposed that a strain concentration factor be introduced to account for the effects of tension stiffening. This factor improves the correlation between observed and predicted flexural strength.
The second failure mode investigated was a flexure shear failure in a negative moment zone. Flexural cracks reduce the shear strength of a reinforced concrete member. Analytical predictions suggest that some hollow-core floor details could be prone to this type of brittle failure. A flexure shear failure was not observed experimentally; however, this does not eliminate the possibility of this failure mode.
A summary of other failure mechanisms possible in hollow-core flooring is also presented. All failure modes should to be considered as part of establishing a hierarchy of failure in the design or retrofit of hollow-core floors.
25
Quezada, Eder, Yaneth Serrano, and Guillermo Huaco. "Dynamic Amplification Factor Proposal for Seismic Resistant Design of Tall Buildings with Rigid Core Structural System." Smart Innovation, Systems and Technologies, 2021. http://hdl.handle.net/10757/653773.
Повний текст джерелаАнотація:
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Currently, there is an increase in the demand for tall buildings in the city of Lima. This research proposes to reduce the dynamic amplification factor through the seismic design of tall buildings based on the requirements of Peruvian code considering that they are regular in plan and height. Minimum base shear values according to the comparison of static seismic shear and dynamic shear from the spectral modal analysis were reviewed for cases of buildings larger than 120 m. The study of 28 reinforced concrete buildings was proposed, with different heights - varying from 24 to 36 floors, with different floor configurations, as well as the arrangement of the walls considering as a rigid core structural system. Additionally, the characteristics of the materials, the loads and combinations were defined. The responses of these buildings were determined by the response spectrum analysis (RSA) and then compared with those obtained by the lineal response history analysis (LRHA), for the last analysis, five Peruvian seismic records were used and scaled to 0.45 g. The seismic responses of the LRHA procedure were taken as a benchmark. The result of this study is the analysis and proposal of the C/R factor for high-rise buildings, as well as obtaining the base shear and drift verification. Minimum base shear values can be reduced for high or long-term buildings, being regular in plan and height.
Revisión por pares
26
Al, Ateah Ali H. "NUMERICAL STUDY OF MULTIPLE ROCKING SELF-CENTERINGROCKING CORE SYSTEMS WITH BUCKLING-RESTRAINED COLUMNSFOR MID-RISE BUILDINGS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1511816354436547.
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27
Naji, Behnam. "Flexural Analysis and Composite Behavior of Precast Concrete Sandwich Panel." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355331734.
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28
Junior, Edgard Sousa. "Análise da interação entre núcleos estruturais e lajes em edifícios altos." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-04042016-162358/.
Повний текст джерелаАнотація:
É apresentado um estudo sobre a análise de edifícios altos enrijecidos com núcleos estruturais utilizando-se processos discretos. A ligação do núcleo estrutural com as lajes do pavimento do edifício é o ponto principal deste estudo. As vigas, pilares e lajes são analisados utilizando-se o Método dos Elementos Finitos. Os núcleos estruturais, que no presente estudo podem ser de seção aberta ou semifechada, são analisados pela teoria de flexo-torção é levado em consideração o empanamento do elemento do núcleo, dessa forma aparece o esforço denominado bimomento. O empenamento do núcleo estrutural é transferido para as lajes, ocorrendo alteração em sua distribuição de esforços. Para o cálculo da estrutura do edifício como um todo é utilizada a técnica de subestruturação em que o edifício é dividido em subestruturas formadas por um determinado número de andares. Os resultados da forma de cálculo pesquisada são comparados com modelos já desenvolvidos por outros autores.This is a study about the analysis of tall buildings with shear/core walls using discrete processes. The joining of shear/core with slabs in tall buildings is the main subject of this work. The beams, columns and slabs are analyzed using the Finite Element Method. The building analysis is in 1st order. The shear/core walls, in this study, can present open or semi-closed cross section; they are analyzed by the theory of warping of beams of solid sections. In this theory we consider the warping of the core element, accounting for the bimoment. The warping of the core is transferred to the slabs, and the efforts in the slabs are altered. In order to calculate the building structure we are using the sub-structure technique, the building is divided in substructures created by a certain number of floors. The results of this research are compared with models developed by other authors.
29
Quezada, Ramos Eder Nel, Arone Yaneth Serrano, and Guillermo Huaco. "A comparative study of the seismic base shear force and story drift ratios using Time History and Modal Spectrum Analysis according to Peru Code E.030 and ASCE 7.16 on high-rise buildings." Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656418.
Повний текст джерелаАнотація:
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Since the last decade there is an important increase of high-rise buildings in Peru, especially in urban areas. Therefore, it is necessary to assess if the Peruvian Seismic Code is applicable for this type of buildings which have long natural periods as their main characteristic. The main objective of this article is to compare the results of the base shear and story drift ratios of Peruvian seismic design code E.030 with those of the ASCE 7-16 standard to the case of high-rise buildings, this due to the fact that there is limited information for tall buildings in Peru or comparison between national or international code for this type of structures. These high rise buildings have square and rectangular plan floors. Half of them have moment frames and reinforce concrete slab around the rigid core and the others have post-tensioned slab as their vertical load resisting system and central core walls with peripheral columns as the lateral force resisting system. Hence, the response spectrum analysis (RSA) is carried out for every case of the four tall buildings with different configurations using both seismic codes. Then results are compared with the linear response history analysis (LRHA) considering five Peruvian ground motions records, which were scaled to 0.45g PGA. It was verified that generally both the base shear and the interstory drifts calculated using ASCE7-16 are less than that obtained with the seismic code E.030.
30
Pinheiro, Gregory Lee. "Estudo da influência do preenchimento de alvéolos em lajes alveolares submetidas à força cortante." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/4696.
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Previous issue date: 2014-04-28Financiadora de Estudos e Projetos
The use of precast elements has become crescent in Brazil, due to the need of haste during production as well as while assembling the structures. Bearing in mind a quick assembly and the competitive price for this kind of frame, precast elements have been growing and spreading in this field throughout the country. There is something special about demanding hollow core slabs, in virtue of their own low weight, in face of the empty spaces generated by the hollows and a better use of materials because of pretension technique, making it economically feasible. The National Technical Code ABNT NBR 9062, which deals with precast concrete structures, shows no more specific criteria as far as hollow core slabs are concerned, but on the other hand the 2011 review in force to ABNT NBR 14861 which covers precast hollow core slabs brings about relevant aspects such as the method used to check the capacity of shear strength on precast hollow core slabs, both with and without concrete structural cover, and furthermore with and without hollow fillings. Considering the reduced amount of national research on this topic, this study aims to develop and perform techniques in different ways of filling the hollows and the slabs and how they behave when exposed to shear strength tests. As a consequence to the manufacturing process of such type of slab and the hollow- filling method, failure in the idealized filling, in virtue of each material own behavior and inappropriate technique are commonly found.
O emprego de elementos pré-fabricados tem se tornado crescente no Brasil, dado a necessidade de velocidade de produção e montagem de estruturas. Tendo em vista a rápida montagem e o preço competitivo deste tipo de estrutura, elementos prémoldados tem ganhado campo no mercado nacional. Há um destaque pela procura de lajes alveolares, devido ao seu baixo peso próprio, decorrente de vazios proporcionados pelos alvéolos e maior otimização dos materiais em virtude da aplicação da técnica de pré-tração, tornando-a economicamente viável. A Norma Técnica Nacional ABNT NBR 9062 que trata de estruturas pré-moldadas de concreto não apresenta critérios mais específicos para lajes alveolares, por outro lado a revisão em vigor de 2011 da ABNT NBR 14861 que aborda lajes alveolares préfabricadas traz aspectos relevantes tais como o método de verificação da resistência à força cortante de lajes alveolares com ou sem capeamento estrutural e com ou sem preenchimento de alvéolos. Tendo em vista o reduzido volume de pesquisas nacionais sobre o tema, esta pesquisa tem como objetivo fazer um estudo teórico-experimental das diferentes técnicas de preenchimento de alvéolos de lajes alveolares e o seu comportamento quando submetidas a ensaios de força cortante. Como consequência do processo de fabricação deste tipo de laje e do método de preenchimento dos alvéolos, falhas no preenchimento idealizado devido ao comportamento distinto dos materiais e técnicas inadequadas são comumente constatadas.
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Marquesi, Matheus Lorena Gonçalves. "Contribuição ao estudo dos mecanismos resistentes à força cortante em lajes alveolares protendidas." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/4697.
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Previous issue date: 2014-02-25In this work flexure shear and tension shear are studied. It is presented a literature review with emphasis on the major normative recommendations about the shear strength in elements without shear reinforcement. Concerning flexure shear capacity considerations are made about the tensile strength of high strength concrete by analysis of 39 experiments. This samples were collected in the literature and are presented herein. Furthermore, it is proposed to consider the variable influence of prestressing on the shear strength. With respect to tension shear, it is proposed the coefficient b, which seeks to improve the traditional models considering indirectly the influence of shear stresses in transmission length. 49 international experiments are analyzed to validate this coefficient and it is concluded that the modified models show significant improvements. Yet developed an experimental program were tested 15 hollow core slabs varying the distance between the edge of the slab and its nearest support. All failures were by tension shear. The transmission length established by NBR14861 was considered adequate for the tested slabs by correlation with tension shear test results.
Os mecanismos condicionantes à ruptura por força cortante em lajes alveolares são estudados: flexo-cortante e tração diagonal. Apresenta-se a revisão bibliográfica com ênfase nas recomendações dos principais códigos normativos acerca da resistência à força cortante em elementos sem armadura transversal. Quanto à flexo-cortante, considerações são feitas sobre a resistência à tração de concretos de alta resistência pela análise de 39 experimentos coletados na literatura e apresentados neste trabalho. Além disso, propõe-se a consideração da influência variável da protensão na resistência a força cortante. No tocante a tração diagonal, propõe-se o coeficiente b, que busca melhorar os modelos de cálculo tradicionais considerando de forma indireta a influência dos esforços cisalhantes devido à introdução da protensão na laje alveolar. São analisados 49 experimentos internacionais para a validação deste coeficiente e conclui-se que os modelos de cálculo modificados por este coeficiente apresentam melhoras significativas. Desenvolveu-se ainda um programa experimental em que foram ensaiadas 15 lajes alveolares variando a distância entre a extremidade da laje e seu apoio mais próximo. Todas as rupturas foram pelo mecanismo de tração diagonal. O comprimento de transferência de protensão estabelecido pela NBR14861 foi considerado adequado para as lajes ensaiadas pela correlação com os resultados dos ensaios de ruptura por força cortante.
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Bower, Owen J. "Analytical Investigation into the Effect of Axial Restraint on the Stiffness and Ductility of Diagonally Reinforced Concrete Coupling Beams." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1211065883.
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Periotto, Bruna Catoia. "Lajes alveolares protendidas: cisalhamento em região fissurada por flexão." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-20092011-111138/.
Повний текст джерелаАнотація:
Esta pesquisa teve como principal objetivo analisar o comportamento de lajes alveolares protendidas de uso corrente no Brasil (pequenas espessuras e alta protensão) quanto ao cisalhamento em região fissurada por ação do momento fletor, para diferentes situações: sem e com capa e com preenchimento parcial de alvéolos. Foi desenvolvido um estudo teórico com o emprego de equacionamentos analíticos disponíveis na literatura técnica, envolvendo as recomendações da norma brasileira NBR 6118:2003 (Projeto de Estruturas de Concreto), do ACI-318:2008 (Building code requirements for structural concrete) e da EN 1992-1-1 (2004) (Eurocode 2- Projeto de estruturas de betão Parte 1-1: Regras gerais e regras para edifícios). Foram feitas comparações com resultados experimentais obtidos a partir de inúmeros ensaios de lajes alveolares protendidas. As unidades ensaiadas nesta pesquisa foram disponibilizadas por quatro empresas brasileiras de intensa atividade no mercado, sendo analisadas as capacidades resistentes de diferentes tipos. Assim, foram realizados 96 ensaios, 31 para a determinação da capacidade resistente à flexão e 65, ao cisalhamento, sendo selecionados modelos de lajes com grande emprego no mercado brasileiro. A partir desses ensaios, foi possível entender melhor o comportamento das lajes alveolares protendidas produzidas no Brasil. Com as diversas análises, considerando os ensaios experimentais e um vasto estudo teórico quanto ao dimensionamento dessas lajes, verificou-se a adequabilidade de equações de diferentes normas. Assim, foi possível identificar o equacionamento que melhor representa o comportamento das peças produzidas no Brasil, considerando inclusive peculiaridades de comportamento, que apresentam diferenças constratantes com relação a unidades produzidas em outros países. A partir desses estudos, produziu-se um amplo memorial de cálculo, considerando as diversas tipologias de lajes estudadas, com o objetivo de contribuir de modo didático com os engenheiros de estrururas. Logo, com esta pesquisa, foi possível não somente melhorar o entendimento do comportamento de tais lajes alveolares, como também fornecer subsídios para a avaliação desses elementos, considerando as características específicas das lajes produzidas no Brasil e, assim, contribuir para a padronização do dimensionamento junto à norma brasileira NBR 14861 (Laje pré-fabricada - Painel alveolar de concreto protendido).This work had as major objective to analyze the behavior of Brazilian prestressed hollow core slabs - small thickness and high level of prestressing - considering shear in a cracked region due to bending moment, for different design situations: without concrete topping, with concrete topping and with filling the voids. A theoretical study was developed with the use of analytical equations available in the technical literature, involving the recommendations of the Brazilian code NBR 6118:2003 (Design of concrete structures), ACI-318: 2008 (Building code requirements for structural concrete) and EN 1992-1-1 (2004) (Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings), comparing experimental results from many prestressed hollow core slabs tests. The slabs tested in this study were provided by four different Brazilian companies with intense activity in the market, and the resistant capacity of different typologies was analyzed. Thus 96 tests were made, 31 to determine the bending capacity and 64 for the determination of shear strength, and were selected slab models from the Brazilian market that are highly employed. From these tests, it was possible a better understanding of the prestressed hollow core slabs behavior produced in Brazil. With several analysis considering the experimental tests and an ample theoretical study about the design of these slabs, the adequacy of different codes equations were verified. Thus, it was possible to identify the equations that best represent the behavior of elements produced in Brazil, also considering the behaviour peculiarities of these slabs that have contrasting differences, if compared with units produced in other countries. From these studies it was produced a large design manual, considering the various types of studied slabs, aiming to contribute in a didactic way to the structural engineers. So, with this research, it was possible not only to improve comprehension of the behavior of such prestressed hollow core slabs, as well as provide information for evaluation of these elements, considering the specific characteristics of the slabs fabricated in Brazil and thus to contribute with the standardization of the design in the Brazilian code NBR 14861 (Prefabricated slab - Prestressed concrete hollow core panel).
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FORTNEY, PATRICK JOSEPH. "THE NEXT GENERATION OF COUPLING BEAMS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115837131.
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Pedrosa, Filho Celso de Freitas. "Influencia do reembasamento com resina composta na resistencia a extrusão de retentores intra-radiculares de fibra de vidro." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289716.
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Orientador: Luis Roberto Marcondes MartinsTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Neste estudo avaliou-se a resistência ao cisalhamento por extrusão de pinos de fibra de vidro, reembasados ou não com compósito, cimentados com cimento resinoso em dentina intra-radicular, avaliando os segmentos cervical, médio e apical. Selecionaram-se 20 incisivos bovinos com dimensões semelhantes, removendo a porção coronária, padronizando o comprimento das raízes em 16 mm. Após, incluiu-se as raízes em resina acrílica, realizando tratamento endodôntico e, então o preparo dos espaços para os pinos, dividindoas, em seguida, aleatoriamente em dois grupos com dez amostras cada. Os elementos do grupo 1 receberam pinos de fibra de vidro somente cimentados, e do grupo 2 pinos de fibra de vidro reembasados com compósito e posteriormente cimentados. Ao término dos procedimentos de cimentação, realizou-se a secção dos segmentos radiculares, submetendo, então, os corpos-de-prova ao teste push-out em máquina de ensaios universal, através de ponta ativa cilíndrica com 1 mm de diâmetro, à velocidade de 0,5 mm/min, até extrusão do retentor. Obteve-se os seguintes valores médios de resistência de união, em MPa: grupo 1, terços cervical = 6,24 ± 2,68(b), médio = 4,27 ± 2,00(b) e apical = 4,46 ± 2,82(b); grupo 2, terços cervical = 11,83 ± 1,69(a), médio = 11,81 ± 3,86(a) e apical = 10,39 ± 2,44(a). Submeteram-se os valores à análise de variância e ao teste de Tukey com nível de significância de 5%, indicadas acima através de letras diferentes. Os pinos de fibra de vidro reembasados com compósito apresentaram valores estatisticamente superiores de união em todos os segmentos radiculares quando comparados com pinos somente cimentados. Observou-se também a ausência de diferença significativa entre os terços radiculares avaliados para cada grupo distintamente. Os resultados demonstraram que a técnica de reembasamento mostrou-se efetiva em melhorar a retenção do pino de fibra de vidro estudado
Abstract: This study evaluated the bond strength of fiber posts, relined or not with composite resin, luted with resinous cement to radicular dentin, evaluating cervical, median and apical root segments. Twenty bovine incisors, with similar dimensions, were selected and cut 16 mm from the apical limit. The roots were embedded in acrylic resin and the radicular canals were root treated and post space prepared with a depth of 9 mm. Samples were randomly assigned to two groups of ten roots each. Group 1 received glass fiber posts (Fibrekor) luted with dual-cure resin cement (RelyX ARC) in association with a bonding system (Adper Single Bond). In Group 2 the same type of posts were relined with composite (P-60) for further cementation with the same materials used in Group 1. After cementation procedures roots were sectioned transversally and three sections, from cervical, medium and apical thirds were obtained. Push-out test was performed in a universal testing machine with a 1 mm diameter steel rod at cross-head speed of 0,5 mm/min until post extrusion. Collected data was statistically analyzed by twoway ANOVA and Tukey HSD test (p<0,05). The measured retention strengths for cervical, medium and apical thirds were: Group 1, 6.24 ± 2.68(b), 4.27 ± 2.00(b) and 4.46 ± 2.82(b) ; Group 2, 11.83 ± 1.69(a), 11.81 ± 3.86(a) and 10.39 ± 2.44(a). Glass fiber composite relined posts presented statistically higher retention values in cervical, medium and apical thirds when compared to non-relined posts. Within each group, no differences were found among radicular thirds. The results indicate that the tested technique showed effective improvement of glass fiber post retention strength
Doutorado
Dentística
Doutor em Clínica Odontológica
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Gibson, Jason. "Nano-Particles in Multi-Scale Composites and Ballistic Applications." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5745.
Повний текст джерелаАнотація:
Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through two mechanisms. The first being the elongation of the fiber reinforcement contained in the resin matrix, and the second is the propagation of the crack in between the discreet fabric plies. This research aims to fundamentally study the energy absorption characteristics of various nano-particles as reinforcements in thermoset resin for high velocity impact applications. Multiple morphologies will be evaluated through use of platelet, tubular and spherical shaped nano-particles. Evaluations of the effect on stress transfer through the matrix due to the combination of nano sized and micro scale particles of milled fiber is conducted. Three different nano-particles are utilized, specifically, multi-walled carbon nanotubes, graphene, and core shell rubber particles. The difference in surface area, aspect ratio and molecular structure between the tube, platelet and spherical nano-particles causes energy absorption through different failure mechanisms. This changes the impact performance of composite panels enhanced with the nano-particle fillers. Composite panels made through the use of dispersing the various nano-particles in a non-contact planetary mixer, are evaluated through various dynamic and static testing, including unnotched cantilever beam impact, mixed mode fracture toughness, split-Hopkinson bar, and ballistic V50 testing. The unnotched cantilever beam testing showed that the addition of milled fiber degraded the impact resistance of the samples. Addition of graphene nano platelets unilaterally degraded impact resistance through the unnotched cantilever beam testing. 1.5% loading of MWCNT showed the greatest increase in impact resistance, with a 43% increase over baseline. Determining the critical load for mixed mode interlaminar shear testing can be difficult for composite panels that bend without breaking. An iterative technique of optimizing the coefficient of determination, R2, in linear regression is developed for objectively determining the point of non-linearity for critical load. This allows for a mathematical method of determination; thereby eliminating any subjective decision of choosing where the data becomes non-linear. The core shell rubber nano particles showed the greatest strain energy release rate with an exponential improvement over the baseline results. Synergistic effects between nano and micro sized particles in the resin matrix during transfer of the stress wave were created and evaluated. Loadings of 1% milled carbon fiber enhanced the V50 ballistic performance of both carbon nanotube and core shell rubber particles in the resin matrix. However, the addition of milled carbon fiber degrades the impact resistance of all nano-particle enhanced resin matrices. Therefore, benefits gained from the addition of micro-sized particles in combination with nano-sized particles, are only seen in high energy impact scenarios with micro second durations. Loadings of 1% core shell rubber particles and 1% milled carbon fiber have an improvement of 8% in V50 ballistic performance over the baseline epoxy sample for 44 mag single wad cutter gas check projectiles. Loadings of 1% multi-walled carbon nanotubes with 1% milled carbon fiber have an improvement of 7.3% in V50 ballistic performance over the baseline epoxy sample. The failure mechanism of the various nano-particle enhanced resin matrices during the ballistic event is discussed through the use of scanning electron microscope images and Raman spectroscopy of the panels after failure. The Raman spectroscopy data shows a Raman shift for the fibers that had an enhancement in the V50 performance through the use of nano-particles. The Raman band for Kevlar centered at 1,649 cm-1 stemming from the stretching of the C==O bond of the fiber shows to be more sensitive to the residual axial strain, while the Raman band centered at 1,611 cm-1 stemming from the C-C phenyl ring is minimally affected for the CSR enhanced panels due to the failure mechanism of the CSR particles during crack propagation.Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
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Celal, Mahmut Sami. "Shear Behaviour of Precast/Prestressed Hollow-Core Slabs." 2012. http://hdl.handle.net/1993/5077.
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Shear strength of precast/prestressed hollow-core (PHC) slabs subjected to concentrated or line loads, especially near supports, may be critical and usually is the governing criteria in the design. This study presents the second phase of a research program, undergoing at the University of Manitoba, to calibrate the shear equations in the Canadian code for predicting the shear capacity of PHC slabs. This phase includes both experimental and numerical investigations using a finite element analysis (FEA) software package. The length of bearing, void shape and size, level of prestressing and shear span-to-depth ratio were investigated. The experimental results were compared to the predictions of the Canadian, American and European codes. It was concluded that the Canadian code is unduly conservative. However, the special European code for PHC slabs resulted in better and more consistent predictions. The FEA suggested that the adequate prestressing reinforcement ratio to obtain highest shear capacity ranges between 0.7% and 1.1%.
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Truderung, Karl. "Shear capacity of dry-cast extruded precast/prestressed hollow-core slabs." 2011. http://hdl.handle.net/1993/4832.
Повний текст джерелаАнотація:
Based on previous testing and analysis, it is believed that North American concrete design codes yield conservative shear designs for precast/prestressed hollow-core slabs in the 203 to 305 mm depth range. The objective of this research program is to calibrate the Canadian code shear equations to precast/prestressed hollow-core slabs, through testing a series of full-scale slabs to failure in shear. A total of twelve hollow-core slabs from one slab producer, using two types of extruders were tested in shear. Test variables include the bearing length and the prestressing level. Results are presented in terms of experimental to predicted capacity using the Canadian and American concrete design codes, the failure mode, crack profiles, and the critical section location for shear. It was concluded that the Canadian code shear equations are inappropriate for use with hollow-core slabs with low prestressing levels in the 203 to 305 mm depth range.
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Shen, Ching, and 沈情. "Synthesis of Core-Shell Nanoparticles and Its Application as Shear Thickening Fluid." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/fz42aa.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
化學工程研究所
102
Shear thickening fluid, a type of non-Newtonian fluid, changes viscosity based on shear rate. It has low viscosity at low shear rates, and high viscosity at high shear rates. Thus, this fluid stays mobile under normal conditions, but swiftly hardens upon high-speed impact, resulting in a material useful in liquid armor. So far, most studies have focused on silica-based material as the primary particles in shear thickening fluids, but they often show limited resistance to puncturing. Herein, an approach to synthesize core-shell (alumina/silica) nanoparticles, which can be used as the dispersed phase in the liquid armor materials. Notably, the combination of alumina and silica materials shows significant advantage for enhancing the protective properties of the liquid armor. The core-shell nanoparticles in this study were synthesized using a sol-gel process wherein the silica shell was grown on alumina nanoparticles via a condensation reaction with TEOS. Subsequently, characterization was performed through dynamic light scattering, TEM, and zeta potential measurements. Rheometer measurements were also made using the as-synthesized nanoparticles (treated via sonication) dispersed in a polyethylene glycol medium with varying volume fractions. Thus, the rheological properties of the core-shell system could be investigated and the shear thickening phenomenon observed at high shear rates. Finally, the application of alumina/silica core-shell nanoparticles in liquid armor and the optimization of their comprehensive feasibility and rheological properties are discussed.
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Morrish, John Stanley. "Geophysical investigation of shear flow at the top of the earth's outer core." 1994. http://hdl.handle.net/1993/18189.
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Lin, Tzu-Wei, and 林字衛. "The study of shear layer and vortex core for the annular swirling jet." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/79449242178742068075.
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Chien, Shih-Shun, and 簡士勛. "Synthesis of Alumina and Core-Shell Nanoparticles and Their Application as Shear Thickening Fluid." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/08424170518396013973.
Повний текст джерелаАнотація:
碩士國立臺灣大學
化學工程學研究所
101
Abstract Shear thickening fluid, so called STF, which has a special rheological behavior of the fluid. When suddenly exposed to external shocks, it rapidly presented like a solid which has hardness of properties in a short time (about a few milliseconds). Army Research Laboratory (ARL) first developed shear thickening fluid for military. They researched based on the Kevlar fibers, which was immersed the shear thickening fluid which consists silica nanoparticles and polyethylene glycol mixing, and they called it liquid armor. This shear thickening fluid can greatly enhance the application of Kevlar fiber strength and impact resistance. So far, study of shear thickening fluid based on nano silica particles is now quite mature, the tests on STF-Kevlar fiber containing the liquid armor by spikes, razor, needle, and low-speed bullet attack presented in much effective impact on defense capabilities in general Kevlar fiber. This result makes shear thickening fluid earn greatly in the military''s attention. There are many capable STF research direction currently, so our major research is core-shell (polystyrene / silica) and alumina, which can replace silica nanoparticles as a new dispersed phase and then disperse in polyethylene glycol alcohol. Finally, we use rheometer to test their rheological behavior, exploring the future of this shear thickening fluid.
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Nip, T. F., and Dennis Lam. "Effects of end condition of hollow core slabs on longitudinal shear capacity of composite beams." 2001. http://hdl.handle.net/10454/5541.
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Lam, Dennis, and E. El-Lobody. "Finite element modelling of headed stud shear connectors in composite steel beam with precast hollow core slabs." 2001. http://hdl.handle.net/10454/5540.
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Mones, Ryan M. "Interfacial Strength Between Prestressed Hollow Core Slabs and Cast-in-Place Concrete Toppings." 2012. https://scholarworks.umass.edu/theses/747.
Повний текст джерелаАнотація:
The horizontal shear strength of the interface between prestressed concrete hollow core slabs and cast-in-place concrete topping slabs was evaluated through a set of 24 push-off experiments. The push-off test specimens featured segments of dry-mix and wet-mix hollow core slabs with a variety of surface treatments including machine finished, sandblasted, broom roughened, rake roughened and grouted. A cast-in-place slab was poured on top of the hollow core specimens to form a 15 inch by 15 inch interface between the two materials. Results indicate the average horizontal shear strength of the push-off specimens was 227 psi. Higher shear strength and slip capacity was observed in specimens that were broom roughened in the direction transverse to the applied shear force and in grouted dry-mix specimens. Specimens with machine finished surfaces had lower average horizontal shear strength than those with intentionally roughened surfaces, but still exceeded the shear strength of 80 psi specified in the ACI 318-08 code. A method to comparatively quantify the surface roughness of the hollow core slabs with different surface treatments was adapted from an existing ASTM standard for pavements. This standard specifies the procedure to determine mean texture depth that can be correlated to horizontal shear strength of the push-off specimens. Analytical studies were also performed to estimate the maximum horizontal shear stresses that can be expected in composite hollow core slabs under normal construction conditions. A finite element model was developed to observe the behavior of the horizontal shear failure mode for composite hollow core slabs.
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Pollard, Brittney Maryah. "Reactivation of fractures as discrete shear zones from fluid enhanced reaction softening, Harquahala metamorphic core complex, west-central Arizona." Thesis, 2014. http://hdl.handle.net/2152/25744.
Повний текст джерелаАнотація:
Discrete (mm- to m-scale) mylonitic shear zones in the northeastern Harquahala metamorphic core complex, Arizona, show evidence of fluid-mineral interactions catalyzing deformation and metamorphism. Many contain a deformed central epidote vein with adjacent bleached haloes and flanking paired shear zones that indicate significant fluid-rock interaction during deformation. An integration of structural and geochemical methods was employed to understand timing, metamorphic conditions, and physiochemical processes responsible for producing the discrete shear zones. Field and microstructural evidence suggest the zones initiated on antecedent fractures. Electron backscatter diffraction (EBSD) analyses show a significant coaxial contribution to the shear, and quartz deformation predominately by prism slip, along with some rhomb slip, suggesting amphibolite-facies conditions during shearing. Fourier Transform Infrared spectroscopy analyses of quartz reveal higher water contents within shear zones than within country rocks, indicating fluid infiltration synchronous with shearing. Stable isotope analyses of quartz and feldspar from mylonites are consistent with an igneous or metamorphic fluid origin. Microstructural observations suggest that the zone morphology with epidote veins, bleached haloes, and flanking discrete paired shear zones was developed predominantly from reaction softening mechanisms. The increase in deformation from bleached rock to flanking shear zones is marked by progressive modal increases in biotite and myrmekite, and modal decreases in K-feldspar, and locally epidote and titanite. Myrmekitic textures recrystallized readily and resulted in progressively greater grain size reduction of feldspar, which aided in the progressive alignment and linkage of the biotite grains, which together concentrated the deformation in bands. Volume reduction resulting from some of the metamorphic reactions may have led to a positive feedback cycle among fluid infiltration, metamorphism and deformation. U-Pb isotope analyses of syn-metamorphic titanite yield an age of ~70 Ma, suggesting the shear zones formed during cooling of the Late Cretaceous (75.5±1.3 Ma) Brown’s Canyon pluton, consistent with their top-to-the-southwest sense of shear, rather than during top-to-the-northeast directed Miocene metamorphic core complex exhumation. Petrography, EBSD analyses, and U-Pb dating of titanite from other (non-discrete) mylonites in the area imply most formed synchronously with the discrete shear zone mylonites. Only rare, scattered mylonites show features consistent with metamorphic core complex exhumation.text
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Lam, Dennis, K. S. Elliott, and D. A. Nethercot. "Push-off Tests on Shear Studs with Hollow-cored Floor Slabs." 1998. http://hdl.handle.net/10454/5626.
Повний текст джерелаАнотація:
The shear capacity of headed studs in precast concrete hollow-core slab construction has been determined experimentally in 12 full-scale push-off tests. The tests were used to study the effects of the size of the gap between the ends of the precast slabs, and the amount of tie steel placed transversely across the joint, and the strength of concrete infill. Under certain situations the capacity of the stud is reduced compared with that in a solid reinforced concrete slab. Maximum resistances are compared with the predictions of BS 5950 and EC4, and a reduction formula for the precast effect is derived.
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Ortiz, Navas Francisco Roberto. "Effectiveness of polypropylene fibres as shear reinforcement in structural elements." Doctoral thesis, 2020. http://hdl.handle.net/10251/153147.
Повний текст джерелаАнотація:
[EN] Several efforts have been made in experimental and theoretical research about shear to understand all the variables that influence the phenomenon. Nowadays, however, due to its complexity, the shear performance of structural concrete elements, especially those without any traditional transversal reinforcement, continue with no clear explanation of the problem. Uncertainty about the problem grows when new variables like fibres are incorporated into the shear study. Research works have demonstrated the effectiveness of steel fibre in improving the mechanical properties of concrete elements. Experimental results reveal that steel fibres have proven effective in improving shear resistance, and they confer some concrete elements more ductility. In adequate amounts, steel fibres can completely or partially substitute traditional shear reinforcements. This is why international codes have included some requirements to take into account the action of fibres on the shear response of concrete elements. However, most recommendations and requirements for steel fibre-reinforced concrete (SFRC) were originally created. New fibres with different materials properties and shapes, such as macrosynthetic fibres, are now available on the market. These fibres, some of which are made of polypropylene, are an alternative in the construction industry given their properties and final cost. Initially, polypropylene fibres were used to control shrinkage cracking. Nevertheless, in the last decade the chemical industry has created larger fibres with better surface shapes, which allows polypropylene fibres to meet the requirements of international codes so they can be used in structural elements. Within this framework, the present PhD thesis aims to contribute to knowledge about fibre reinforced concrete (FRC), especially to study the effectiveness of polypropylene fibres when used as shear reinforcement. For this purpose, a literature review of the material, polypropylene fibre-reinforced concrete (PFRC) and its structural applications is first carried out. This study also discusses the parameters that affect the shear behaviour of traditional concrete and FRC. In order to evaluate the effectiveness of polypropylene fibres in shear, three experimental campaigns are presented. Each campaign represents a different level of study. The first corresponds to the material level, where the shear behaviour of PFRC is evaluated by push-off specimens. The second level involves studying shear in real scale elements. For this purpose, shear critical slender beams were manufactured and tested. The last level corresponds to real application of polypropylene fibres to act as shear reinforcement. In this campaign, deep hollow core slabs, with real sections and supports conditions, were tested. At each level, the shear behaviour of PFRC was evaluated against control reinforced concrete specimens, which were also tested during each campaign.[ES] Varias investigaciones experimentales y teóricas han sido realizadas para entender el comportamiento a cortante de elementos de hormigón y sus variables. Sin embargo, hoy en día debido a la complejidad del tema, el comportamiento a cortante de elementos de hormigón armado y en especial aquellos que no tienen refuerzo transversal, continúan sin tener una explicación clara. Por otro lado, esta complejidad del cortante aumenta cuando nuevas variables, como las fibras, se incorporan al estudio. Investigaciones han demostrado la efectividad de las fibras de acero para mejorar las propiedades mecánicas de hormigón. Según resultados experimentales, la fibra de acero mejora la resistencia cortante y ductilidad de ciertos elementos. Y en cantidades adecuadas, la fibra puede sustituir total o parcialmente los refuerzos tradicionales de cortante. Es así que varios códigos internacionales han incluido requisitos para tener a las fibras en la respuesta estructural de elementos de hormigón. Sin embargo, estos requerimientos se han creado originalmente para el hormigón reforzado con fibra de acero (Steel fibre-reinforced concrete -SFRC). Nuevas fibras con diferentes materiales y formas, como las fibras macro-sintéticas, han sido introducidas en el mercado. Estas fibras, también llamadas fibras de polipropileno o poliolefina, son una alternativa en la construcción debido a su propiedades y costo final. Inicialmente, las fibras de polipropileno eran usadas únicamente en el hormigón para controlar la fisuración por retracción. Sin embargo, en la última década la industria química ha desarrollado fibras más grandes y con mejores prestaciones de adherencia, que permiten a estas fibras cumplir con requisitos para ser utilizadas estructuralmente. En este contexto, la presente tesis pretende ser una contribución al conocimiento sobre el hormigón reforzado con fibras (Fibre-reinforced concrete - FRC), especialmente en la efectividad de las fibras de polipropileno como refuerzo a cortante. Para esto, primero se realiza un estudio bibliográfico del hormigón reforzado con fibra de polipropileno (PFRC) como material y sus aplicaciones estructurales. Este estudio también tratará sobre los parámetros que afectan el comportamiento a cortante del hormigón tradicional y hormigón reforzado con fibras. Para evaluar la efectividad de las fibras de polipropileno en el cortante, se realizarán tres campañas experimentales. Cada campaña representa un nivel de estudio diferente. El primero es a nivel material en donde se evalúa el comportamiento a cortante a través de especímenes tipo Push-off. El segundo nivel, corresponde al estudio del cortante en elementos a escala real. Para esto se fabrican y ensayan vigas esbeltas críticas a cortante. El último nivel corresponde a una aplicación real de fibras de polipropileno actuando como refuerzo cortante. En esta campaña, se fabrican y ensayan placas alveolares de gran canto con secciones y condiciones de apoyos reales.
[CA] Diverses investigacions experimentals i teòriques han estat realitzades per entendre el comportament a tallant d'elements de formigó i les seues variables. No obstant això, hui en dia a causa de la complexitat del tema, el comportament a tallant d'elements de formigó armat i especialment aquells que no tenen reforç transversal, continuen sense tindre una explicació clara. D'altra banda, aquesta complexitat del tallant augmenta quan noves variables, com les fibres, s'incorporen a l'estudi. Investigacions han demostrat l'efectivitat de les fibres d'acer per a millorar les propietats mecàniques del formigó. Segons resultats experimentals, les fibres d'acer milloren la resistència a tallant i la ductilitat de certs elements. A més, en quantitats adequades, les fibres poden substituir total o parcialment els reforços tradicionals de tallant. És així que diversos codis internacionals han inclòs requisits per a tindre amb compte la resposta estructural de les fibres en els elements de formigó. No obstant això, aquests requeriments s'han creat originalment per al formigó reforçat amb fibres d'acer (Steel fibre-reinforced concrete -SFRC). Noves fibres amb diferents materials i formes, com les fibres macro-sintètiques, han estat introduïdes al mercat. Aquestes fibres, també anomenades fibres de polipropilè o poliolefina, són una alternativa a la construcció a causa de les seues propietats i cost final. Inicialment, les fibres de polipropilè eren usades únicament en el formigó per controlar la fissuració per retracció. No obstant això, en l'última dècada, la industria química ha desenvolupat fibres més grans i amb millors prestacions d'adherència, que permeten a aquestes fibres complir amb requisits per a ser utilitzades estructuralment. En aquest context, la present tesi pretén ser una contribució al coneixement sobre el formigó reforçat amb fibres (Fibre-reinforced concrete - FRC), especialment en l'efectivitat de les fibres de polipropilè com a reforç a tallant. Per això, primer es realitza un estudi bibliogràfic del formigó reforçat amb fibres de polipropilè (PFRC) com a material i les seues plicacions estructurals. Aquest estudi també tractarà sobre els paràmetres que afecten el comportament a tallant del formigó tradicional i del formigó reforçat amb fibres. Per avaluar l'efectivitat de les fibres de polipropilè en el tallant, es realitzaran tres campanyes experimentals. Cada campanya representa un nivell d'estudi diferent. El primer és a nivell material on s'avalua el comportament a tallant a través d'espècimens tipus Push-off. El segon nivell, correspon a l'estudi del tallant en elements a escala real. Per això es fabriquen i assagen bigues esveltes crítiques a tallant. L'últim nivell correspon a una aplicació real de fibres de polipropilè actuant com a reforç a tallant. En aquesta campanya, es fabriquen i assagen plaques alveolars de gran cantell amb seccions i condicions de suports reals.
Ortiz Navas, FR. (2020). Effectiveness of polypropylene fibres as shear reinforcement in structural elements [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153147
TESIS
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"High-Resolution Imaging of Structure and Dynamics of the Lowermost Mantle." Doctoral diss., 2012. http://hdl.handle.net/2286/R.I.14510.
Повний текст джерелаАнотація:
abstract: This research investigates Earth structure in the core-mantle boundary (CMB) region, where the solid rocky mantle meets the molten iron alloy core. At long wavelengths, the lower mantle is characterized by two nearly antipodal large low shear velocity provinces (LLSVPs), one beneath the Pacific Ocean the other beneath Africa and the southern Atlantic Ocean. However, fine-scale LLSVP structure as well as its relationship with plate tectonics, mantle convection, hotspot volcanism, and Earth's outer core remains poorly understood. The recent dramatic increase in seismic data coverage due to the EarthScope experiment presents an unprecedented opportunity to utilize large concentrated datasets of seismic data to improve resolution of lowermost mantle structures. I developed an algorithm that identifies anomalously broadened seismic waveforms to locate sharp contrasts in shear velocity properties across the margins of the LLSVP beneath the Pacific. The result suggests that a nearly vertical mantle plume underlies Hawaii that originates from a peak of a chemically distinct reservoir at the base of the mantle, some 600-900 km above the CMB. Additionally, acute horizontal Vs variations across and within the northern margin of the LLSVP beneath the central Pacific Ocean are inferred from forward modeling of differential travel times between S (and Sdiff) and SKS, and also between ScS and S. I developed a new approach to expand the geographic detection of ultra-low velocity zones (ULVZs) with a new ScS stacking approach that simultaneously utilizes the pre- and post-cursor wavefield.. Strong lateral variations in ULVZ thicknesses and properties are found across the LLSVP margins, where ULVZs are thicker and stronger within the LLSVP than outside of it, consistent with convection model predictions. Differential travel times, amplitude ratios, and waveshapes of core waves SKKS and SKS are used to investigate CMB topography and outermost core velocity structure. 1D and 2D wavefield simulations suggest that the complicated geographic distribution of observed SKKS waveform anomalies might be a result of CMB topography and a higher velocity outermost core. These combined analyses depict a lowermost mantle that is rich in fine-scale structural complexity, which advances our understanding of its integral role in mantle circulation, mixing, and evolution.Dissertation/Thesis
Ph.D. Geological Sciences 2012
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El-Lobody, E., and Dennis Lam. "Modelling of headed stud in steel ¿ precast composite beams." 2002. http://hdl.handle.net/10454/5639.
Повний текст джерелаАнотація:
Use of composite steel construction with precast hollow core slabs is now popular in the UK,but the present knowledge in shear capacity of the headed shear studs for this type of composite construction is very limited. Currently, all the information is based on the results obtained from experimental push-off tests. A finite element model to simulate the behaviour of headed stud shear connection in composite beam with precast hollow core slabs is described. The model is based on finite element method and takes into account the linear and non-linear behaviour of all the materials. The model has been validated against the test results, for which the accuracy of the model used is demonstrated. Parametric studies showing the effect of the change in transverse gap size, transverse reinforcement diameter and in-situ concrete strength on the shear connection capacity are presented.