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[pt] Uma extensa campanha de ensaios de cisalhamento direto foi realizada na Areia da Praia de Ipanema, inspirado em Simões (2015). Os ensaios foram realizados em corpos de prova na condição seca, moldados em seis diferentes domínios de compacidade relativa (CR), desde muito fofo até muito compacto. Para cada domínio de CR, foram realizados ensaios sob dez diferentes valores de tensão normal nominal, variando de 25 a 1250 kPa. Em todos os ensaios, foi utilizado um dispositivo desenvolvido para impedir a rotação do top cap. A grande quantidade e variedade de ensaios permitiu uma análise detalhada de como as características das curvas tensão cisalhante sobre tensão normal versus deslocamento horizontal relativo e deslocamento vertical do top cap versus deslocamento horizontal relativo variaram com as variações de CR e de tensão normal, especialmente o ângulo de atrito de pico e o deslocamento vertical do top cap na ruptura, mostrando contração ou dilatação na ruptura. O ângulo de atrito a volume constante da Areia da Praia de Ipanema parece estar situado entre 30 e 32 graus. Uma curva que relaciona índice de vazios crítico e tensão normal nominal crítica foi obtida a partir dos ensaios de cisalhamento direto na Areia da Praia de Ipanema, sendo análoga à linha de estado crítico proposta por Lee e Seed (1967). Ademais, a alta frequência de aquisição de dados tornou explícito o fenômeno conhecido como stick-slip nas curvas obtidas, mostrando que a amplitude do fenômeno é tanto maior quanto menor a tensão normal nominal. / [en] A comprehensive research program of direct shear tests was carried out on Ipanema Beach Sand, inspired by Simões (2015). The tests were carried out on specimens in dry condition, prepared in six different domains of relative density (Dr), from very loose to very dense. For each Dr domain, tests were performed under ten different values of nominal normal stress, ranging from 25 to 1250 kPa. In all tests, a device developed to prevent the rotation of the top cap was used. The large number and variety of tests allowed a detailed analysis of how the characteristics of the Shear stress over normal stress versus relative horizontal displacement curves and top cap vertical displacement versus relative horizontal displacement curves varied with CR and normal stress variations, especially the peak friction angle and the vertical displacement of the top cap at failure, showing contraction or dilation at failure. The angle of friction at constant volume of the Ipanema Beach Sand seems to be situated between 30 and 32 degrees. A curve relating critical void ratio and critical nominal normal stress was obtained from the direct shear tests run on Ipanema Beach Sand, being analogous to the critical state line proposed by Lee and Seed (1967). Moreover, the high frequency of data acquisition made explicit the phenomenon known as stickslip in the obtained curves, showing that the amplitude of the phenomenon is greater the smaller the nominal normal stress.

The aim of this study is to determine if the mini block sampling technique couldoffer a complement to the Swedish standard StII piston sampler for achieving higherquality samples. The principle is that having a greater diameter the sample is meticulouslytrimmed to the usual geometry, so that the periphery of the sample is not disturbedby the sampling procedure and the same testing equipment can be employed.Hence, the test would provide higher and more accurate values of deformation andshear strength properties.The testing campaign executed for this study includes routine analysis with fallcone tests, CRS oedometer tests, DSS tests, CAUC triaxial tests and sedimentationtests. All of them have been performed on East-Sweden varved clay from Barkarby,Stockholm. Afterwards, the results and the sampling procedure were analysed toevaluate the performance of the mini block sampler.The mini block sampler provided more pronounced preconsolidation pressureson CRS tests as well as higher values of the quality index Mi=ML. DSS tests presenthigher values of undrained shear strength but no difference in shear strain at failure.In addition, the values of shear modulus show stiffer behaviour for block samplesas a prove of better clay structure preservation. Regarding triaxial results, theundrained shear strength values are higher for block samples with higher stresspeaks and lower strain to failure in the stress-strain graphs. Finally, several qualityindex were analysed obtaining better results for block sampling in most of them.It can be concluded that mini block sampler generally presents better qualitysamples than piston sampler for East-Swedish clay. Additionally, it is highlyfavourable for commercial projects due to each block provides up to 8 standard 50mm samples

This thesis evaluates the commonly used geotechnical probing method CPTu, on how different probe configurations impact the resulting evaluated undrained shear strength in soft clay deposits, in comparison to each other and laboratory methods. This is done by performing field investigations on Lindefältet, Södermanlands län, Sweden. Comparison is done on the two Swedish manufacturers of CPTu probes, by different calibration limits, filter types and whether overloading the probe over the calibration limit affects the evaluated undrained shear strength registered. The main conclusions are that one of the manufacturers’ probes registers deviating results in one configuration, that calibration limit has a noticable impact on the results, and that overloading on the probe and filter choice has negliable impact on the results. / I detta examensarbete utvärderas den vanligt förekommande geotekniska sonderingsmetoden CPTu, på hur olika konfigurationer av sonder påverkar den resulterande utvärderade odränerade skjuvhållfastheten i lösa leravlagringar, 9i jämförelse med varandra och med laboratoriemetoder. Detta är genomfört genom fältundersökningar på Lindefältet, Södermanlands län. Jämförelsen gjordes på de två svenska CPTu-tillverkarnas sonder. Detta är gjort med hänsyn till olika kalibreringar av konspetstryck, filtertyper, och huruvida sonden har varit överlastad påverkar den utvärderade skjuvhållfastheten som registreras. De huvudsakliga slutsatserna är att en av tillverkarnas sonder registerar udda värden i en konfiguration, att kalibreringar av konspetstryck har en märkbar påverkan på de resulterande värdena på utvärderade odränerade skjuvhållfastheten, samt att överlastning av sonder och val av filtertyp har liten till omärkbar påverkan på resultatet.

<p>The masonry construction industry represents a historically significant and substantial portion of both existing and new residential, commercial and institutional low- to medium-rise structures across Canada. Although commonly chosen for its aesthetic qualities by architects, structural masonry walls constructed with concrete block units are also an effective lateral force (wind or seismic) resisting system. The purpose of this dissertation is to address what are perceived to be overly conservative and outdated practices within masonry construction and design by adopting analysis and design practices which have had success with similar reinforced concrete wall systems. The results from a test program reporting on the behavior of nine fully-grouted reinforced masonry (RM) structural walls containing confined boundary elements are analyzed and presented according to force-, displacement- and performance-based seismic design considerations. The boundary element containing four vertical bars with lateral confinement stirrups selected represents a readily codified and practically achievable means of achieving seismic performance enhancement. The design and detailing of the specimens represented a range of parameters that would be anticipated to vary within low- to medium-rise RM buildings. In addition, an analytical study is carried out to derive, from first principles of stress equilibrium and strain compatibility, the necessary constitutive material and mechanics-based equations needed to solve for the state of shear stress and strain in an idealized cracked masonry macro-element. The algorithm proposed is validated by comparing the proposed model to existing test data and is further developed towards predicting the design shear strength of RM structural walls. The results from these experimental and analytical research programs are subsequently used to provide a set of proposed code clauses at the end of the thesis. Prescriptive design requirements are proposed for a new category of <em>Special Ductile Masonry Shear Wall</em> containing boundary elements including integration of a new shear strength expression. These clauses have been written with the intention of adoption within the CSA S304.1 and the MSJC North American masonry designs standards.</p> / Doctor of Philosophy (PhD)

Most codes of practice, such as EC2 and ACI 318-05, recommend the use of strut-and-tie models for the design of reinforced concrete deep beams. However, studies on the validity of the strut-and-tie models for continuous deep beams are rare. This paper evaluates the strut-and-tie model specified by ACI 318-05 and mechanism analysis of the plasticity theory in predicting the load capacity of 75 reinforced concrete continuous deep beams tested in the literature. The influence of such main parameters as compressive strength of concrete, shear span-to-overall depth ratio, main longitudinal bottom reinforcement, and shear reinforcement on the load capacity is also investigated using both methods and experimental results. Experimental results were closer to the predictions obtained from the mechanism analysis than the strut-and-tie model. The strut-and-tie model highly overestimated the load capacity of continuous deep beams without shear reinforcement.

yes / A simplified strut-and-tie model including size effect based on the crack band theory is proposed to evaluate the shear capacity of deep beams. Concrete struts are idealized as uniformly tapered prismatic members with a stress relief strip whereas horizontal and vertical shear reinforcements are assumed to be an internally statically indeterminate system. The shear transfer mechanism of concrete and shear reinforcement is then driven by using the energy equilibrium in the stress relief strip and crack band zone of concrete struts. The shear capacity predictions of deep beams obtained from the present models are in better agreement with 637 test results than those determined from strut-and-tie models proposed by ACI 318-08, EC-2, and Tan and Cheng. In addition, the trend of the shear capacity of deep beams against different parameters as predicted by the present models has a consistent agreement with that observed from experimental results. In particular, the present model shows that the normalized shear capacity of deep beams is proportional to (h)−0.25, where h = section overall depth.

The primary objective of this research was to investigate the shear strength of concrete bridge decks with GFRP top-mat reinforcement. Several models currently exist to predict the shear strength during the design process; however, previous research at Virginia Tech indicates that the existing equations are overly conservative. For this research, a series of concrete decks with varying lengths were tested in a laboratory environment in a two-span continuous configuration, during which data was collected on deflections, rebar strain, crack widths, and ultimate load. It was concluded that the existing equations, particularly the guidelines of ACI 440, are grossly over-conservative for GFRP-reinforced concrete bridge decks continuous over multiple supports. It was suggested that this is due to multiple factors, including additional support provided by the typically-neglected steel reinforcement in the bottom mat and a higher shear strength of the uncracked portion of concrete due to higher compressive stresses in the section as a result of the continuous deck configuration. The second objective of this research was to investigate the effects of environmental exposure on the composite deck and the individual GFRP rebar. Three deck specimens were subjected to differing environmental conditions, including one that was placed into service at an interstate weigh station. All three decks were tested in the same manner as those in the shear investigation. Additionally, live load tests were conducted on the weigh station deck during the time it was in place and tensile tests were conducted on rebar that were extracted from the concrete decks. In the live load testing, the GFRP strains increased by more than 200% over the period of service, which was likely due to a combination of a reduction in GFRP stiffness and a greater amount of cracking. During the laboratory tests on the decks, no clear correlation between conditioning and deflections or cracking was found. The ultimate strength actually increased with conditioning, with the weigh station specimen exhibiting the highest shear strength. Finally, the results of the rebar tensile tests suggested a decrease in both modulus of elasticity and ultimate tensile strength of the GFRP with environmental exposure when compared to unconditioned bars. / Master of Science

Low moisture veneer and regions of sapwood within hickory engineered wood flooring bonded with soy-flour adhesive are thought to be factors leading to potential performance deficiencies. The goal of this research was to gain a broader understanding of bonding low moisture hickory veneer with soy-based adhesive. Soyad® is of particular interest due to its novel cross-linking chemistry. Impacts of moisture content and wood region (heartwood versus sapwood) were analyzed with dry and wet shear bond strength tests, measurement of percent wood failure, lathe check characterization, and adhesive bondline thickness and penetration depth measurement. Impact of wood region and type (hickory versus red oak) was assessed by comparing wood buffering capacity and delamination following three-cycle water soaking. Dry and wet shear strength values met expectations for engineered wood flooring yet percentage wood failure results were uniformly very low for all combinations of moisture levels and wood regions. In contrast, delamination following wet and dry cycling was minor and within minimum requirements for all specimens tested. The influence of moisture level, wood region and type were inconsistent; statistically significant relationships were not evident within the moisture range studied. However, different wood regions and types exhibited differing veneer buffering capacities that had potential to interfere with pH requirements of Soyad®. Additional study of buffering capacity and resin cure is recommended to determine the significance of the buffering capacity results found in this study. / Master of Science / Performance issues including debonding and delamination have been reported for hickory engineered wood flooring products constructed using a soy-flour based adhesive. Sapwood regions within the composite and extremely low moisture veneer were provided by industry as possible factors that resulted in performance deficiencies. The goal of this research project was to gain a broader understanding of bonding low moisture hickory veneer with Soyad® adhesive. Soy-flour adhesive systems offer many environmental, health, and durability advantages. Soyad® is of particular interest due to its use of natural, renewable soy flour, a novel cross-linking resin, and no added formaldehyde. Test specimens were prepared using heartwood of hickory and red oak and sapwood of hickory. Analytical tests included determination of certain chemical properties of the adhesive and wood veneer, measurement of strength properties of the adhesive bond, and assessment of delamination tendencies of bonded panels following water soaking. Results indicate that moisture levels and the different growth regions and wood type had an inconsistent impact on the bond strengths yet percent wood failure was uniformly low and considered unacceptable by industry. Although this research established a foundation of basic knowledge, more information about adhesive bonding of wood with the recently developed soy based adhesives is needed to optimize the systems and provide technological advancements that lead to more efficient and safe utilization of woody materials from the forest.

As the first level interconnection in electronic packages, chip attachment plays a key role in the total packaging process. Sintered nanosilver paste may be used as a lead-free alternative to solder for die-attachment at sintering temperature below 300 °C without applying any pressure. Typically, the substrate, such as direct bond copper (DBC) substrates, has surface metallization such as silver or gold to protect the copper surface from oxidation during the sintering process. This study focused on developing techniques for die-attachment on pure copper surface by low-temperature sintering of nanosilver paste. One of the difficulties lies in the need for oxygen to burn off the organics in the paste during sintering. However, the copper surface would oxidize, preventing the formation of a strong bond between sintered silver and copper substrate. Two approaches were investigated to develop a feasible technique for attachment. The first approach was to reduce air pressure as a means of varying the oxygen partial pressure and the second approach was to introduce inert gas to control the sintering atmosphere. For the first method, die-shear tests showed that increasing the oxygen partial pressure (PO₂ from 0.04 atm to 0.14 atm caused the bonding strength to increase but eventually decline at higher partial pressure. Scanning electron microscopy (SEM) imaging and energy dispersive spectroscopy (EDS) analysis showed that there was insufficient oxygen for complete organics burnout at low PO₂ condition, while the copper surface was heavily oxidized at high PO₂ levels, thus preventing strong bonding. A maximum bonding strength of about average 8 MPa was attained at about PO₂ = 0.08 atm. With the second method, the die-shear strength showed a significant increase to about 24 MPa by adjusting the oxygen exposure temperature and time during sintering. The processing conditions necessary for bonding large-area chips (6 mm à 6 mm) directly on pure copper surface by sintering nanosilver paste was also investigated. A double-print process with an applied sintering pressure of less than 5 MPa was developed. Die-shear test of the attached chips showed an average bonding strength of over 40 MPa at applied pressure of 3 MPa and over 77 MPa under 12 MPa sintering pressure. SEM imaging of the failure surface showed a much denser microstructure of sintered silver layer when pressure was applied. X-ray imaging showed a bond layer almost free of voids. Because the samples were sintered in air, the DBC surface showed some oxidation. Wirebondability test of the oxidized surface was performed with 250 μm-diameter aluminum wires wedge-bonded at different locations on the oxidized surface. Pull test results of the bonded wires showed a minimum pull-strength of 400 gram-force, exceeding the minimum of 100-gf required by the IPC-TM-650 test standard. / Master of Science