Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography: p. 482-499. / by Jacques-Noel Levadoux. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 174-178. / by Chee-Kuen Yip. / M.S.

Thesis. 1978. Sc.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Vita. / Bibliography: leaves 342-349. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 163-166. / by Theodore von Rosenvinge IV. / M.S.

No description available.

Carbon nanotubes (CNTs) were dispersed into polyvinyl acetate (PVAc ) adhesive cured by radio frequency (RF) to investigate their loading effects on PVAc adhesive curing time and lap shear bond strength performance. Main factors are CNT loading (0.08, 0.25 and 0.41%), RF curing time (15, 30, 45, 60 seconds), and clamping pressure (100, 160, and 240 psi). Experimental results indicated that CNT loading had significant effects on PVAc curing time and lap shear bond strength. Specifically, single lap shear joints bonded with 0.41% CNT loading adhesive had significantly higher lap shear bond strengths than one with PVAc only (0% CNT loading). The curing time of PVAc dispersed with a 41% CNT loading (15 seconds) was 30 seconds shorter than the one with a 0% CNT loading (45 seconds).

To provide fundamental information for the second generation of cross laminated timber manufacturing, wood sections that glued by different orientations were constructed and tested. To reveal adhesive differences, phenol resorcinol formaldehyde (PRF) and polyurethane (PU) adhesive were used and the gluelines were evaluated in accordance with different conditions for shear strength, wood failure, dimensional stability and delamination. A non-destructive testing method was applied to measure the dynamic modulus of elasticity (dMOE) change. The results showed that the radical wood section of lumber produced with the starsawn process had much less deformation and was more suitable for glueline. PRF had better performance than PU in terms of shear strength, dimensional stability, and delamination. Confocal microscopic pictures revealed that the tangential to tangential (TT) glueline showed the tendency of collapse, indicating a poor bond strength and therefore a poor glueline durability of TT glueline, especially when it was subject to wet conditions.

Fiber sizings are used to improve the performance of fiber-reinforced polymer composites made from low-cost fiber and matrix materials. Evaluation of three sizings, poly(vinylpyrrolidone) (PVP), a carboxyl modified polyhydroxyether (PHE), and a standard industrial sizing (G'), have revealed tremendous improvements in static mechanical and enviro-mechanical properties. The focus of this work is to determine if these improvements in performance can be ascertained from a micromechanical test for interfacial shear strength (IFSS) on as-processed materials. The accomplishment of this goal would create more information with fewer experiments and a need for less experimental materials. In this study, a nanoindenter uniquely outfitted with a blunt tip is effectively used to obtain microindentation results where the debond load is extracted directly from the experimental load-deflection curve. Shear lag and finite element analyses are used to evaluate the mechanics of the system, but both methods show limitations with regard to determining interfacial stresses in an experimental system. In the results obtained, the PHE and Gâ materials outperform the PVP in IFSS, but the bulk properties for PVP and PHE outperform the Gâ material, suggesting the presence of another dominant mechanism. Despite better retention of bulk properties after hygrothermal exposure, PHE experiences degradation in IFSS that PVP does not. The PHE loses 10% of its original IFSS after 576 hours of 65ºC moisture exposure, while PVP improves by 25%. The tensile strengths for PHE and PVP decrease 7% and 10% respectively at 576 hours exposure. Finite element modeling shows that matrix swelling due to moisture absorption increases interfacial shear stresses, a finding supported by a comparison of wet and dry specimens subjected to equivalent aging times. Matrix swelling is not, however, responsible for the increase in IFSS of the PVP material. The relationship between tensile strength and IFSS proves to be small as predicted by a tensile strength model, but processing defects and other failure processes that are not included in the tensile strength model appear to have strong influences over the experimental results. IFSS is important in composite materials, but in the case of the G', PHE and PVP materials, other factors dominate fiber direction tensile performance. Therefore, this one simple micromechanical test provides significant insight into the composite material behavior, but it does not provide the same magnitude of information as from bulk composite experiments. / Master of Science

In order to design more efficient and reliable structures, axial load tests are performed on foundation piles. Traditionally, static tests with an average duration of approximately twenty-four hours have been performed on test piles to obtain their axial capacity. These static tests require multiple piles used as anchors in addition to the test pile. Static tests are both expensive and time consuming. An alternative to static testing is dynamic testing which requires sophisticated interpretation, can damage the pile and may not produce accurate results. There is a relatively new testing method called the Statnamic Testing Method which tests foundation piles at a very fast rate, but still slower than with dynamic tests. As the rate at which load is applied to a test pile increases, the axial capacity also increases, particularly in clay. Research suggests that shear strength of soil typically increases 10% per log cycle increase in strain rate. Strain rate effects can vary widely and may be influenced by many factors including plasticity index, structure, ageing, overconsolidation ratio, temperature, etc. Statnamic testing was performed for this work. Nine static tests were performed on six different piles identical to the Statnamic test pile and driven through the same soil profile. The static tests had times to failure ranging from ten seconds to eighteen hours. Failure load increased by 13.7% per log cycle increase in velocity. Statnamic tests need more careful analysis when performed in clay to avoid over predicting pile capacity. A factor of 0.55 should be applied to Statnamic capacity to predict static capacity.

Site characterization and the subsequent determination of soil strengthparameters constitute a significant part of slope stability assessment.Geotechnical engineering is always governed by great uncertainties sincethe soil properties are challenging to estimate for a large soil volume. Nostandardized method exists for evaluation of soil parameters, since eachcountry uses its own methods for evaluation and interpretation of soils.Uncertainties are common in geotechnical engineering and thereforequalitative and quantitative risk management is required for most projects.The evaluation of the shear strength is essential in slope stability, since ithas a great influence on the stability. This report investigates threedifferent methods regarding the estimation of the characteristic value ofthe undrained shear strength in clay for heterogeneous soils. The followingmethods are used: de 7 with the 5 % fractile, the Swedish applicationdocuments with 𝜂-factor regarding uncertainties and the subjectiveassessment of geotechnical engineers by a questionnaire. In the case studyfor this thesis work, three quayside slopes at Slussen in central Stockholmcontaining highly heterogeneous organic clay located beneath gravel filland esker material were analysed to estimate the stability of the slopes. Theresults show that the 𝜂-factor returned the lowest values, the questionnaireresulted in the second highest and 5 % fractile basted on the samplingdistribution on the mean gave the highest values. No correlation could befound connecting the subjective estimation of the shear strength and otherinfluencing parameter. A method with low subjective judgement, that takethe spatial variability and some degree of interpretation uncertainties witha factor would be to prefer. / Utvärdering av jordar med bedömning av dess egenskaper ochklassificering är en viktig del i släntstabilitetsutredningar. Utmaningenligger i att geoteknik styrs av stora osäkerheter eftersom markensegenskaper är omständliga att uppskatta för en hel jordvolym. Problemetär att det inte existerar någon standardiserad metod för bedömningen avjordparametrar då varje land har sina egna metoder för utvärderingen.Stora osäkerheter ett vanligt problem inom geoteknik och därför krävsbåda kvalitativa och kvantitativa riskhanteringar inom de flesta projekt.Utvärderingen av skjuvhållfasthet är en viktig del i släntstabilitetsutredningareftersom denna parameter har stort inflytande på stabiliteten,därmed även säkerheten. I denna rapport har tre olika metoder undersöktsmed avseende på bedömningen av det karakteristiska värdet förskjuvhållfasthet i lera för heterogena jordar. Dessa är: Eurokod 7 med 5 %fraktil, den svenska metoden med 𝜂-faktor för att beakta osäkerheter ochslutligen subjektiva bedömningen från geotekniker med hjälp av ettfrågeformulär. I denna fallstudie har tre slänter belägna vid kajer i Slusseni Stockholm analyserats. Jordprofilen innehåller heterogen organisk lerasom täcks av en grusig fyllning och överlagrar av årsmaterial. Resultat visaratt metoden med hänsyn till både osäkerheter med 𝜂-faktor samtsubjektiva bedömning gav lägst skjuvhållfasthet, frågeformuläretresulterade i det näst hösta värdena och metoden som gav högts resultatvar 5 % fraktilen baserad på medelvärden. Ingen korrelation kunde hittasangående den subjektiva bedömningen av odränerad skjuvhållfasthet ochinfluensen från andra faktorer. En metod med subjektiv bedömning, somtar rumslig variation samt inkluderar osäkerheter i en faktor skulle vara attföredra eftersom detta skulle medföra ett mer tillförlitligt resultat