Yes / Test results of steel-ultra high performance concrete (UHPC) composite beams with welded steel shear keys (SSKs) under four-point bending are presented in this paper. The objective of the investigation is to reduce the self-weight and manufacturing cost of large-span structures. The study investigates the effects of strength of concrete slab, type, spacing and size of SSK, and concrete slab height and width on flexural behavior of composite beams. The experimental results demonstrate that enhancing concrete strength, reducing SSK spacing, increasing concrete slab size, and using large-size SSK can all significantly enhance the flexural performance. The composite beams with welded SSK exhibit a maximum relative slip of less than 4 mm, while the counterpart with welded bolts has a maximum relative slip greater than 4 mm. The study shows that the welded SSK is more effective than welded bolts in improving the interface shear performance of composite beams and improving the stiffness and load capacity. Additionally, the study defines four failure modes of steel-UHPC composite beams, and the formulae for flexural capacity is developed based on the reasonable basic assumptions. The calculated results fit well with the tested results. The research findings can be provided as a technical support for the design and application of steel-UHPC composite beams. / High-End Foreign Experts Project of Ministry of Science and Technology, China (G2022014054L), the Natural Science Foundation of Jiangsu Province, China (BK20201436), the Science and Technology Cooperation Fund Project of Yangzhou City and Yangzhou University (YZ2022194), the Science and Technology Project of Jiangsu Construction System (2023ZD104, 2023ZD105), the Science and Technology Project of Yangzhou Construction System (202309, 202312) / The full-text of this article will be released for public view at the end of the publisher embargo on 29 May 2025.

Yes / To investigate the bending behavior of Steel-FRP Composite Bars (SFCBs) reinforced Reactive Powder Concrete (RPC) frame beams, both experimental and theoretical study were conducted on five concrete frame beams with different reinforcement ratio, types of concrete and reinforcement. The results indicate that the bending behavior of SFCBs-RPC frame beams progresses through three distinct stages: from loading to the cracking of tensile RPC, from cracking to the yielding of tensile SFCBs, and from yielding to failure. Compared with steel-reinforced RPC frames, the load of SFCBs-RPC frame beam continues to increase with the increase of deformation after the yielding of SFCBs, demonstrating good bearing capacity and ductility. Furthermore, the deformation and crack width of RPC frame beams are obviously lower than those of ordinary concrete frame beams, indicating the excellent deformation control and crack resistance ability of RPC beams. In addition, formulae for flexural stiffness at each stage were derived using the effective moment of inertia method. Taking the design code of reinforced concrete structure for reference and the tensile contribution of steel fibers and the mechanical performance of SFCBs into consideration, and the formulae for crack width of SFCBs-RPC flexural beam were developed. Formulae for the bearing capacity of SFCBs-RPC frame beams were also proposed on the base of simplified materials constitutive models and reasonable basic assumptions. The values predicted by these proposed formulae aligned well with the results tested. The research provides a theoretical support for the design and application of SFCBs-RPC frame beams.

Over the past 50 years, several advancements have been made in the research area of the mechanics of unsaturated soils. These advancements can be categorized into two groups; (i) development (or improvement) of testing techniques (or apparatus) to determine the mechanical properties of unsaturated soils and (ii) development of (numerical, empirical or semi-empirical) models to estimate the variation of mechanical properties of unsaturated soils with respect to suction based on the experimental results. Implementation of the mechanics of unsaturated soils in conventional geotechnical engineering practice, however, has been rather limited. The key reasons for the limited practical applications may be attributed to the lack of simple and reliable methods for (i) measuring soil suction in the field quickly and reliably and (ii) estimating the variation of mechanical properties of unsaturated soils with respect to suction. The main objective of this thesis research is to develop simple and reliable techniques, models or approaches that can be used in geotechnical engineering practice to estimate sol suction and the mechanical properties of unsaturated soils. This research can be categorized into three parts. In the First Part, simple techniques are proposed to estimate the suction values of as-compacted unsaturated fine-grained soils using a pocket penetrometer and a conventional tensiometer. The suction values less than 300 kPa can be estimated using a strong relationship between the compressive strength measured using a pocket penetrometer and matric suction value. The high suction values in the range of 1,200 kPa to 60,000 kPa can be estimated using the unique relationship between the initial tangent of conventional tensiometer response versus time behavior and suction value. In the Second Part, approaches or semi-empirical models are proposed to estimate the variation of mechanical properties of unsaturated soils with respect to suction, which include: - Bearing capacity of unsaturated fine-grained soils - Variation of bearing capacity of unsaturated fine-grained soils with respect to matric suction - Variation of initial tangent elastic modulus of unsaturated soils below shallow foundations with respect to matric suction - Variation of maximum shear modulus with respect to matric suction for unsaturated non-plastic sandy soils (i.e. plasticity index, Ip = 0 %) In the Third Part, approaches (or methodologies) are suggested to simulate the vertically applied stress versus surface settlement behavior of shallow foundations in unsaturated coarse-grained soils assuming elastic-perfectly plastic behavior. These methodologies are extended to simulate the stress versus settlement behavior of both model footings and in-situ plates in unsaturated coarse-grained soils. The results show that there is a reasonably good comparison between the measured values (i.e. soil suction, bearing capacity, elastic and shear modulus) and those estimated using the techniques or models proposed in this thesis research. The models (or methodologies) proposed in this thesis research are promising and encouraging for modeling studies and practicing engineers to estimate the variation of mechanical behavior of unsaturated soils with respect to matric suction.

The objective of this thesis was to advance understanding in the field of biolubrication, finding inspiration from the human synovial joints. This was addressed by investigating the association of key biolubricants and the resulting lubrication performance. Techniques employed during the course of this work were Atomic force microscopy (AFM), Quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray reflectivity (XRR). Key synovial fluid and cartilage components like dipalmitoylphosphatidylcholine (DPPC), hyaluronan (HA), lubricin, and cartilage oligomeric matrix protein (COMP) have been used in the investigations. Focus was towards two lubrication couples; DPPC-hyaluronan and COMP-lubricin. DPPC-hyaluronan mixtures were probed on hydrophilic silica surfaces and COMP-lubricin association structures were explored on weakly hydrophobic poly (methyl methacrylate) (PMMA) surfaces. Investigations of the COMP-lubricin pair revealed that individually these components are unable to reach desired lubrication. However in combination, COMP facilitates firm attachment of lubricin to the PMMA surface in a favourable confirmation that imparts low friction coefficient. DPPC and hyaluronan combined impart lubrication advantage over lone DPPC bilayers. Hyaluronan provides a reservoir of DPPC on the surface and consequently self-healing ability. Other factors like temperature, presence of calcium ions, molecular weight of hyaluronan, and pressure were also explored. DPPC bilayers at higher temperature had higher load bearing capacity. Association between DPPC Langmuir layers and hyaluronan was enhanced in the presence of calcium ions, and lower molecular weight hyaluronan had a stronger tendency to bind to DPPC. At high pressures, DPPC-hyaluronan layers were more stable compared to lone DPPC bilayers. / <p>QC 20170210</p>

Fundações profundas, quando solicitadas ao carregamento lateral, são regidas por três critérios de projeto: resistência última do solo, carga última do elemento estrutural e deflexão máxima. Esses critérios atuam em conjunto e é necessário que sejam analisados dessa forma, visto que a falha de um deles é capaz de acarretar o colapso de todo sistema. No que tange à resistência do solo, metodologias de capacidade de carga existentes traduzem o comportamento de solos granulares e coesivos. Dada a particularidade da atuação de solos residuais na mecânica dos solos, não há uma metodologia abrangente para estacas sujeitas a solicitação de carregamento lateral nesse tipo de solo, o qual apresenta comportamento intermediário e estrutura levemente cimentada. Em vista disso, o presente trabalho propõe um método de estimativa de capacidade de carga para estacas carregadas horizontalmente, quando inseridas em solo residual e em casos em que as mesmas apresentam topo locado em superfície de solo tratado. Dessa forma, dados de provas de carga lateral pré-existentes e ensaios de laboratório executados ao longo da pesquisa serviram como base para a proposição do método, fundamentado no comportamento do material quando solicitado ao carregamento lateral Ensaios de resistência à compressão simples, compressão oedométrica, compressão isotrópica e ensaios triaxiais com medidas de módulo cisalhante demonstram que há um ponto em que se dá a quebra da estrutura cimentada do solo, passando o mesmo a se apresentar num arranjo desestruturado, refletido em maiores deformações. Uma relação linear é capaz de equacionar a capacidade de carga, tanto para estacas inseridas em solo residual quanto para estacas executadas em solo com camada superficial melhorada. Essa relação é estabelecida entre a carga de ruptura das estacas ensaiadas e a área de solo adjacente à mesma, mobilizada pelo carregamento. Os resultados demonstram que a capacidade de carga das estacas estudadas é regida pela tensão de plastificação do material. O equacionamento proposto possibilita a obtenção da carga de ruptura com base em ensaios simples e de fácil execução, tal como o ensaio de resistência à compressão simples que estabelece relação direta com a tensão de plastificação do solo estudado. / Deep foundations, when requested to lateral loading, are governed by three design criteria: ultimate soil strength, piles’ ultimate load, and maximum deflection. These criteria act together and must be analyzed in this way, since the failure of one of them is capable of causing the collapse of the entire system. Regarding soil resistance, the current bearing capacity methodologies describe the behavior of granular and cohesive soils. Given the particular behavior of the residual soils in the soil mechanics, there is no comprehensive methodology for piles subject to lateral loads and inserted in this soil type, which presents an intermediate behavior and a lightly cemented structure. Thus, the present work proposes an estimated bearing capacity for crosswise loaded piles, when inserted in residual soil and in soil with the top layer cemented. So, data from preexisting lateral loading tests and laboratory tests, performed during the research, served as a basis for the proposition of the method, based on the behavior of the material when requested to lateral loading Unconfined compression tests, oedometer consolidation tests, isotropic compression, and triaxial tests with measures of shear modulus demonstrate that there is a point where the soil's cemented structure breaks down, presenting itself in a destructured arrangement, reflected by larger strains. A linear relationship is capable of equating the bearing capacity for both, piles inserted in residual soil and piles carried out in soil with improved surface layer. This relationship is established between the rupture load of the piles tested and the area of soil adjacent to it mobilized by the loading. The results shows that the piles' bearing capacity is governed by the yield stress of the material. The proposed equation makes it possible to obtain the rupture load based on simple and easy tests, such as the unconfined compression test that establishes a direct relationship with the yield stress of the studied soil.

Pesquisas recentes têm mostrado que a utilização de camada de reforço em solo-cimento é uma alternativa para o aumento da capacidade de carga e redução dos recalques de fundações superficiais em solos de baixa resistência. Os métodos para previsão da capacidade de carga em sistemas de dupla camada encontrados na literatura trazem implícita a premissa de que a camada superior é contínua ou suficientemente maior que a largura da fundação. O objetivo desta pesquisa foi desenvolver um novo método para o cálculo de capacidade de carga de fundações superficiais assentes sobre uma camada de reforço em solo-cimento, considerando sua extensão lateral. Para tanto, foram realizados ensaios em modelos reduzidos de fundações contínuas assentes sobre um solo arenoso fofo, bem como, análises numéricas através do método dos elementos finitos. Observaram-se dois tipos distintos de ruptura. No primeiro, a camada de reforço é puncionada para dentro do solo natural, sem apresentar fissuras, até o deslocamento correspondente à capacidade de carga do solo natural No segundo, após um recalque inicial, a camada de reforço rompe com o aparecimento de uma fissura, que pode localizar-se junto à borda ou no eixo da fundação, e se propaga de baixo para cima, à medida que aumentam os recalques. Verificou-se que a máxima tensão de tração na camada de reforço é função da reação do solo na base do reforço e da relação Tr/Hr, onde Tr é a distância horizontal entre a borda da fundação e a borda do reforço e Hr é a espessura do reforço. A partir destas observações, foi desenvolvido um novo método de cálculo com a premissa de que a ruptura ocorra no solo e não na camada de reforço. Assim, é possível calcular a capacidade de carga considerando que fundação e reforço atuam como um elemento único, apoiado na mesma profundidade de assentamento do reforço. Ao mesmo tempo, é apresentada uma equação para previsão da máxima tensão de tração que atuará no reforço, a partir da qual, se pode dimensioná-lo com segurança. / Recent researches have shown that the use of soil-cement reinforcement layer is an alternative to increase bearing capacity and reduce settlements of shallow foundations in low resistance soils. The existing methods for predicting bearing capacity of double layer systems implicitly assume that the top layer is continuous or sufficiently greater than the foundation width. This study aims to develop a new method for bearing capacity calculation of shallow foundations supported by a soil-cement reinforcing layer, considering its lateral extension. Therefore, small scale tests of continuous foundations on a loose sandy soil, as well as, numerical analysis by the finite element method were carried out. It was observed two distinct types of failure. In the first, the reinforcement layer is punched through the sandy soil, without showing any cracking, up to a settlement which corresponds to the sand bearing capacity. In the second, after an initial settlement, the reinforcement layer breaks up, showing a fissure, which may be located near the edge or the axis of foundation, and propagates upward as the settlements continues. It was found that the maximum tensile stress in the reinforcement layer is a function of soil reaction on the reinforcement and the ratio Tr/Hr, where Tr is the horizontal distance between the edge of the foundation and the edge soil-cement layer and Hr is the thickness of the soil-cement layer. From these observations, it was developed a new calculation method, with the assumption that the failure occurs in the soil and not in the reinforcement layer. Thus, it is possible to calculate the bearing capacity considering that foundation and reinforcement act as a single element, supported at the same depth of the reinforcement base. In order to design the soil-cement layer, an equation for the maximum tensile stress prediction is provided.

Se retirará este documento a solicitud del Sandra Rodriguez Dionisio, Coordinador de carrera de Ingeniería Civil. Fecha de solicitud mediante correo electrónuico 19-09-2019 / La investigación consiste en la evaluación técnico-económica de tres alternativas de cimentación, las cuales son platea de cimentación, sistema de zapatas y micropilotes, estudiadas en tres proyectos situados en un suelo de baja capacidad portante igual a 1.01kg/cm2. Esto con el objetivo de determinar la alternativa de solución más óptima en función a los criterios técnico y económico, teniendo en cuenta que la opción de platea de cimentación es comúnmente la más empleada. En cuanto a los proyectos, estos corresponden a edificios multifamiliares de 4, 6 y 8 pisos, de material de concreto armado, de sistema estructural a base de muros y sin sótanos. Estos ese encuentran situados en un suelo arenoso (SP-SM), sin presencia del nivel freático ni fallas geológicas, perteneciente al distrito de Ica, provincia de Ica, departamento de Ica, Perú. Respecto al diseño de las alternativas de cimentación, estas se rigen bajo las exigencias de las normas de diseño vigentes en el Perú, correspondientes al Reglamento Nacional de Edificaciones (RNE). Asimismo, se utilizaron programas de software como ETABS y SAP2000, para complementar el análisis estructural de los edificios y diseño de las alternativas de cimentación. Posterior al diseño, se realizó la evaluación técnico-económica, proponiendo un plan de ejecución (cronograma) acorde con las características y contexto del proyecto, como también un presupuesto económico para cada caso. Finalmente, mediante un análisis comparativo que contrasta ambos criterios, se concluye la alternativa de cimentación más óptima para cada caso de estudio. / The investigation consists in technical and economic evaluation of foundation alternatives, which are foundation plate, shoe system and micropiles, for three projects located in a low bearing capacity soil of to 1.01kg/cm2. The study objective is determine the best foundation alternative according to technical and economic criteria, taking into account that foundation plate is commonly the most used. Corresponding to the projects, these are multifamily buildings of 4, 6 and 8 floors, of reinforced concrete material, structural system based on walls and without basements. In the same way, these projects are located in a sandy soil (SP-SM), without freatic level presence neither geological fails, located in Ica district, Ica province, Ica department, Peru. On the other hand, according to the foundation alternatives design, these are supported by the requirements of the peruvian design rules “Reglamento Nacional de Edificicaciones” (RNE). In the same way, software programs such as ETABS and SAP2000 were used to complement the study of buildings structural performance and foundation alternatives. After design, the technical-economic evaluation was carried out, proposing an execution plan (schedule) according to the characteristics and context of the projects, and an economic budget for each case. Finally, through a comparative analysis that contrats both criteria, the best foundation alternative por each case is concluded. / Tesis

Over the past 50 years, several advancements have been made in the research area of the mechanics of unsaturated soils. These advancements can be categorized into two groups; (i) development (or improvement) of testing techniques (or apparatus) to determine the mechanical properties of unsaturated soils and (ii) development of (numerical, empirical or semi-empirical) models to estimate the variation of mechanical properties of unsaturated soils with respect to suction based on the experimental results. Implementation of the mechanics of unsaturated soils in conventional geotechnical engineering practice, however, has been rather limited. The key reasons for the limited practical applications may be attributed to the lack of simple and reliable methods for (i) measuring soil suction in the field quickly and reliably and (ii) estimating the variation of mechanical properties of unsaturated soils with respect to suction. The main objective of this thesis research is to develop simple and reliable techniques, models or approaches that can be used in geotechnical engineering practice to estimate sol suction and the mechanical properties of unsaturated soils. This research can be categorized into three parts. In the First Part, simple techniques are proposed to estimate the suction values of as-compacted unsaturated fine-grained soils using a pocket penetrometer and a conventional tensiometer. The suction values less than 300 kPa can be estimated using a strong relationship between the compressive strength measured using a pocket penetrometer and matric suction value. The high suction values in the range of 1,200 kPa to 60,000 kPa can be estimated using the unique relationship between the initial tangent of conventional tensiometer response versus time behavior and suction value. In the Second Part, approaches or semi-empirical models are proposed to estimate the variation of mechanical properties of unsaturated soils with respect to suction, which include: - Bearing capacity of unsaturated fine-grained soils - Variation of bearing capacity of unsaturated fine-grained soils with respect to matric suction - Variation of initial tangent elastic modulus of unsaturated soils below shallow foundations with respect to matric suction - Variation of maximum shear modulus with respect to matric suction for unsaturated non-plastic sandy soils (i.e. plasticity index, Ip = 0 %) In the Third Part, approaches (or methodologies) are suggested to simulate the vertically applied stress versus surface settlement behavior of shallow foundations in unsaturated coarse-grained soils assuming elastic-perfectly plastic behavior. These methodologies are extended to simulate the stress versus settlement behavior of both model footings and in-situ plates in unsaturated coarse-grained soils. The results show that there is a reasonably good comparison between the measured values (i.e. soil suction, bearing capacity, elastic and shear modulus) and those estimated using the techniques or models proposed in this thesis research. The models (or methodologies) proposed in this thesis research are promising and encouraging for modeling studies and practicing engineers to estimate the variation of mechanical behavior of unsaturated soils with respect to matric suction.

With the developments in computer technology, the numerical methods are used widely in geotechnical engineering. Finite element and finite difference are the most common methods used to simulate the behavior of soil and rock. Although the reliability of these methods are proven in several fields of application over the years, they are not equally satisfactory in every case and require sophisticated constitutive relations to model the discontinuous behavior of geomaterials since they assume the material is continuum or the location of discontinuum is predictable. The Discrete Element Method (DEM) has an intensive advantage to simulate discontinuity. This method is relatively new and still under development, yet it is estimated that it will replace of the continuum methods largely in geomechanics in the near feature. In this thesis, the theory and background of discrete element method are introduced, and its applicability in bearing capacity calculation of shallow foundations is investigated. The results obtained from discrete element simulation of bearing capacity are compared with finite element analysis and analytical methods. It is concluded that the DEM is a promising numerical analysis method but still have some shortcomings in geomechanical applications.

Naudojamų hidrotechnikos statinių konstrukcijos veikiamos įvairių apkrovų ir neigiamo aplinkos poveikio nudėvimos, susiformuoja pažeidos. Ypač pavojingos pažeidos, mažinančios pagrindinių konstrukcijų laikančiąją galią. Netekus laikomosios galios kyla grėsmė statinio patikimumui ir ilgaamžiškumui. Remiantis užšalimų – atšilimų ciklų įtakos hidrotechnikos statinių konstrukcijų betonui tyrėjų darbais nustatėme, kad mokslinėje literatūroje lig šiol nepakankamai aptarta atraminių sienučių ilgaamžiškumo nustatymo metodika, pagrįsta pagrindinių betono fizikinių – mechaninių savybių kitimo veikiant užšalimų – atšilimų ciklams, vertinimu. Darbo tikslas – įvertinti hidrotechnikos statinių gelžbetoninių atraminių sienučių betono stiprio kitimo įtaką laikomąjai galiai. 2006–2007 metais tyrinėtos 6 naudojamų žemių užtvankų, esančių Marijampolės rajone, atraminės sienutės. Atliekant tyrimus nustatytos labiausiai pažeistos atraminių sienučių vietos, pažeidų tipas, plotas ir gylis bei nustatyta pagrindinė tiriamoji charakteristika – gniuždomojo betono stipris. Skaičiavimais įvertintas Antanavo hidromazgo atraminių sienučių laikomosios galios rezervas, sudaryta jo priklausomybė nuo gniuždomojo betono stiprio. Remiantis gniuždomojo betono stiprio fc ir vandens įgėrio Wm tyrimų rezultatais, žinant leidžiamą ar prognozuojamą betono stiprio sumažėjimą Δ fc dėl šalčio poveikio, apskaičiuotas betono atsparumo šalčiui rodiklis F50 % bei pagal jį nustatytas ilgaamžiškumo rodiklis – galutinio... [toliau žr. visą tekstą] / Hydraulic structures are under the impacts of various loads and aggressive environment during exploitation, they deteriorate and forms pittings. Pittings decreasing bearing capacity of main constructions are very dangerous. After loosing bearing capacity the danger arises for the reliability and durability of the hydraulic structure in general. Analysis of various researchers’ works about frost cycles influence to the concrete of HS showed, that so far in the scientific literature is not sufficiently discussed the method for retaining walls durability determination based on evaluation of change of main physical– mechanical properties of the concrete under the influence of frost cycles. The aim of the work is to evaluate the bearing capacity of reinforced concrete retaining walls under the influence of changing compression strength. The reinforced concrete retaining walls of hydraulic structures in Marijampole district were investigated in 2006–2007. The following characteristics of these retaining walls were determined when carrying out the investigations: main deteriorations and defects, average depth and area of pittings, the actual quantities of main physical-mechanical properties of concrete – compression strength. Remainder of bearing capacity was evaluated by determination of Antanavas retaining walls compression strength. Using the research results of concrete compression strength fc and water absorbability Wm and knowing allowed or forecasted loss of the concrete... [to full text]