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1
Eizadjou, Mehdi. "Design of Advanced High Strength Steels". Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17315.
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A new advanced high strength steels (AHSS) is designed based on Fe-C-Mn-Al composition. Martensitic steel is processed in intercritical region to achieve an ultrafine-grained duplex γ–(α + α') microstructure. The focus was on tuning the degree of austenite plasticity via controlling its stability, called austenite engineering. Interest in austenite engineering stems from transformation-induced plasticity (TRIP) effect, which is known to enhance ductility. The thermodynamic and kinetic analyses were used to optimize the annealing condition. The evolution of microstructure and mechanical properties was studied using different techniques. Due to high heating rate, the austenite reversion occurred before recrystallization of the ferrite. The final microstructure was duplex steel with globular-shaped grains. High volume fraction of the austenite phase was obtained (f_γ>40%) in very short time annealing. By increasing annealing temperature and time, austenite fraction and grain size increased. However, due to dilution of the austenite from stabilizers elements, the stability of the austenite dropped and transformed into martensite during quenching. This led in variety of austenite stabilities that resulted in different combination of mechanical properties. The critical factors influencing the onset of TRIP effect is studied and it was found that both early and delayed onset of the TRIP effect will lead to worse ductility. Hence, to achieve ultrahigh strength and excellent ductility, austenite stability shall be controlled to precisely trigger out TRIP. This study find out that discontinuous yielding or Lüders bands phenomenon can be used in ultrafine duplex steels to improve ductility. The results showed that superb combination of strength (σ_YS>1.0GPa and σ_UTS>1.4GPa) and ductility (ε_t≥20%) could be achieved in short time annealing of less than 10 minutes. This work evidence that tuning the austenite to a marginal stability enables us to design strong and ductile steels.
2
Soutsos, Marios Nicou. "Mix design, workability heat evolution and strength development of high strength concrete". Thesis, University College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308062.
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A literature survey of the properties and uses of high strength concrete, defined for this study as having a strength in excess of 60 N/tnm2, has shown that of prime need is a systematic, reproducible procedure for attaining high strength concrete. The "Maximum Density Theory", i.e. the requirement that the aggregate occupies as large a relative volume as possible, has been adopted as an approach to optimisation of the mix proportions. However, this does not consider the effect that the aggregate suIface area has on the requirement of excess paste for lubrication. To investigate the combined effect of void content and surface area, mixes with lower sand proportions than that required for minimum void content were tested for slump. The optimum sand proportion is the one that produces the highest slump, for a particular cement content. This procedure has been called: "The Modified Maximum Density Theory". Having thus optimised the cement and aggregate contents, partial cement replacement by mineral admixtures, at low water-cement ratios, has been investigated in order to assess: a) their contribution to long term strengths, b) their contribution to reducing the heat evolution of concrete mixes, and c) their effect on the workability of concrete. Condensed silica fume (at replacement levels of up to 15%) produced higher compressive strengths than ordinary Portland cement. Ground granulated blast furnace slag (at replacement levels of up to 30%) can be used without decreasing the 28-day strength. Replacement by 20% pulverised fuel ash resulted in a 15% decrease in the 28-day strength and equal strength to ordinary Portland cement concrete at ages beyond 56-days. Temperature measurements during hydration, under adiabatic conditions, have however shown that these replacement levels do not lower the temperature rise at a water-binder ratio of 0.26. The higher levels required for significant temperature reduction will also cause a significant reduction in the strength. To offset this ground granulated blast furnace slag (58%) and pulverised fuel ash (36%) in combination with 10% condensed silica fume 4 were used. These combinations reduced the temperature rise by more than 10°C while the reduction in the 28-day compressive strength was less than 15%. Partial cement replacement by pulverised fuel ash and ground granulated blast furnace slag improved the workability and therefore allowed a reduction in the superplasticiser dosage required for a given slump. The use of condensed silica fume reduces the workability at low superplasticiser dosages, but it has a water-reducing effect above a certain superplasticiser dosage. Results from these studies have been used to formulate guidelines for the proportioning of materials for producing high strength concrete.
3
Cladera, Bohigas Antoni. "Shear design of reinforced high-strength concrete beams". Doctoral thesis, Universitat Politècnica de Catalunya, 2003. http://hdl.handle.net/10803/6155.
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Aunque el hormigón de alta resistencia se está utilizando de manera creciente en los últimos años para la construcción de estructuras, la norma Española vigente, la Instrucción EHE, sólo abarca hormigones de resistencias características a compresión inferiores a 50 MPa. El aumento de resistencia del hormigón está directamente asociado a una mejora en la mayoría de sus prestaciones, especialmente de la durabilidad, aunque también produce un aumento en la fragilidad y una disminución de la rugosidad de las fisuras, lo que afecta de forma muy especial a la resistencia a cortante.El objetivo principal de este trabajo es contribuir al avance del conocimiento del comportamiento frente a la rotura por cortante de vigas de hormigón de alta resistencia. Para ello, y en primer lugar, se ha llevado a cabo una extensa revisión del estado actual del conocimiento de la resistencia a cortante, tanto para hormigón convencional como para hormigón de alta resistencia, así como una profunda investigación de campañas experimentales anteriores.
Se ha realizado una campaña experimental sobre vigas de hormigón de alta resistencia sometidas a flexión y cortante. La resistencia a compresión del hormigón de las vigas variaba entre 50 y 87 MPa. Las principales variables de diseño eran la cuantía de armadura longitudinal y transversal. Los resultados obtenidos experimentalmente han sido analizados para estudiar la influencia de las distintas variables en función de la resistencia a compresión del hormigón.
Con el objetivo de tener en cuenta, no sólo los resultados de nuestros ensayos, sino también la gran cantidad de información disponible en la bibliografía técnica, se ha preparado una base de datos con vigas de hormigón convencional y de alta resistencia a partir del banco de datos de la Universidad de Illinois. Los resultados empíricos han sido comparados con los cortantes últimos calculados según la Instrucción EHE, las especificaciones AASHTO LRFD, el Código ACI 318-99 y el programa Response-2000, basado en la teoría modificada del campo de compresiones.
Se han construido dos Redes Neuronales Artificiales (RNA) para predecir la resistencia a cortante en base a la gran cantidad de resultados experimentales. La principal característica de las RNA es su habilidad para aprender, mediante el ajuste de pesos internos, incluso cuando los datos de entrada y salida presentan un cierto nivel de ruido. Con los resultados de la RNA se ha realizado un análisis paramétrico de cada variable que afecta la resistencia última a cortante.
Se han propuesto nuevas expresiones que tienen el cuenta el comportamiento observado para el diseño frente al esfuerzo cortante de vigas tanto de hormigón convencional como de alta resistencia con y sin armadura a cortante, así como una nueva ecuación para la determinación de la armadura mínima a cortante. Las nuevas expresiones presentan resultados que se ajustan mejor a los resultados experimentales que los obtenidos mediante la utilización de las normativas vigentes.
Finalmente se han planteado varias sugerencias de futuras líneas de trabajo, que son resultado de la propia evolución del conocimiento sobre el tema de estudio durante el desarrollo de esta tesis.
Although High-Strength Concrete has been increasingly used in the construction industry during the last few years, current Spanish Structural Concrete code of practice (EHE) only covers concrete of strengths up to 50 MPa. An increase in the strength of concrete is directly associated with an improvement in most of its properties, in special the durability, but this also produces an increase in its brittleness and smoother crack surfaces which affects significantly the shear strength.
The aim of this research is to enhance the understanding of the behaviour of high-strength concrete beams with and without web reinforcement failing in shear. In order to achieve this objective, an extensive review of the state-of-the-art in shear strength for both normal-strength and high-strength concrete beams was made, as well as in-depth research into previous experimental campaigns.
An experimental programme involving the testing of eighteen high-strength beam specimens under a central point load was performed. The concrete compressive strength of the beams at the age of the tests ranged from 50 to 87 MPa. Primary design variables were the amount of shear and longitudinal reinforcement. The results obtained experimentally were analysed to study the influence of those parameters related to the concrete compressive strength.
With the aim of taking into account, in addition to the results of our tests, the large amount of information available, a large database was assembled based on the University of Illinois Sheardatabank for normal-strength and high-strength concrete beams. These test results were compared with failure shear strengths predicted by the EHE Code, the 2002 Final Draft of EuroCode 2, the AASHTO LRFD Specifications, the ACI Code 318-99, and Response-2000 program, a computer program based on the modified compression field theory.
Furthermore, two Artificial Neural Networks (ANN) were developed to predict the shear strength of reinforced beams based on the database beam specimens. An ANN is a computational tool made up of a number of simple, highly-interconnected processing elements that constitute a network. The main feature of an ANN is its ability to learn, by means of adjusting internal weights, even when the input and output data present a degree of noise. Based on the ANN results, a parametric study was carried out to study the influence of each parameter affecting the failure shear strength.
New expressions are proposed, taking into account the observed behaviour for the design of high-strength and normal-strength reinforced concrete beams with and without web reinforcement. A new equation is given for the amount of minimum reinforcement as well. The new expressions correlate with the empirical tests better than any current code of practice.
Finally, as a natural corollary to the evolution of our understanding of this field, some recommendations for future studies are made.
4
Wilson, R. C. "Welded airframes : static strength, structural design and analysis". Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546430.
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Vennapusa, Siva Koti Reddy. "Design of bi-adhesive joint for optimal strength". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-16675.
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To support the trust in the design development of adhesively bonded joints, it is important to precisely predict their mechanical failure load. A numerical simulation model with a two-dimensional linear elastic cohesive zone model using a combination of a soft and a stiff adhesive is developed to optimize the strength of a lap-joint. Separation under mixed-mode conditions (normal and shear direction) is considered. By varying the length of the adhesives, the fracture load is optimized. The results obtained from the numerical experiments show an improvement in strength.
6
Wang, Jie. "Behaviour and design of high strength steel structures". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43758.
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High strength steels (HSS), which are generally considered to be those with yield strengths over 460 MPa, are being increasingly utilised in construction, particularly in high rise structural applications and where long and column-free spans are an important design requirement. In place of ordinary carbon steels, the use of HSS can enable structural elements with smaller cross-sections, resulting in significant material savings. However, compared to normal strength steels, the structural use of HSS is still quite rare. The European design code EN 1993-1-12 provides design rules for HSS up to S700, but was conceived as a simple extension of the rules in EN 1993-1-1 for normal strength steels. In order to contribute to the existing limited HSS data pool and to verify and develop the current Eurocode 3 design rules, a comprehensive experimental programme on hot-finished S460 and S690 square and rectangular hollow sections has been carried out. The testing programme covered different structural aspects at the material, cross-section and member levels and consisted of 40 tensile coupon tests, 11 compressive coupon tests, 11 stub column tests, 11 full section tensile tests, 22 in-plane bending tests, 12 eccentrically loaded stub column tests, 30 long column tests, as well as measurements of geometrical imperfections and residual stresses. Numerical models, validated against the test results, were also developed to examine the cross-section and member behaviour, and subsequently employed in a comprehensive parametric study in order to generate further data. Based on the combined test and numerical data set, as well as experimental results reported in the literature, the current HSS design rules in Eurocode 3, including the slenderness limits for cross-section classification, effective width equation, N-M interaction curves and column buckling curves, were assessed by means of reliability analyses in accordance with Annex D of EN 1990. To realise the potential of HSS in long span structures, a novel structural form was also examined, namely an HSS truss with prestressing cables housed within the tubular bottom chord. A total of 4 prestressed trusses, made of S460 square hollow sections with different prestress levels, were tested under static downward loading. The truss test results showed the enhanced structural efficiency brought about by the addition of prestressing cables and by the application of prestress. Additionally, 12 tensile and 10 compressive member tests with cables, representing the bottom chord of the truss under gravity and uplift loading, respectively, were carried out to investigate the behaviour of individual prestressed cable-in-tube members. Analytical models and numerical models were also established to compare with the test behaviour and to contribute to the development of design rules for prestressed cable-in-tube systems.
7
Reis, Jonathan M. "Structural Concrete Design with High-Strength Steel Reinforcement". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277124990.
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Khurshid, Mansoor. "Static and fatigue analyses of welded steel structures : some aspects towards lightweight design". Doctoral thesis, KTH, Lättkonstruktioner, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200829.
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The objectives of this thesis comprise of overcoming the challenges in designing lightweight welded structures such as material selection, choice of fatigue design methods, and increased performance by using improvement techniques. Material selection of welded joints is dependent on the filler and base material strengths. Partially and fully penetrated cruciform and butt welded joints were designed in under-matching, matching, and over-matching filler materials. Base material steel grades were S600MC, S700MC, and S960. Current design rules are developed for welds in steel up to yield strength of 700MPa. Therefore, design rules in Eurocode3, AWS d1.1, and BSK 07 were verified and recommendations for developing design rules for designing welded joints in S960 were concluded. Numerical methodology for estimating static strength of welded joints by simulating heat affected zone was also developed. Another objective of the thesis work was to overcome the challenges in selection of fatigue design methods. The available design curves in standards are developed for uniaxial stress states, however, in real life the welds in mechanical structures are subjected to complex multiaxial stress states. Furthermore; weld toe failures are frequently investigated, weld root failures are seldom investigated. Therefore, in this work the multiaxial fatigue strength of welded joints failing at the weld root was assessed using experiments and various nominal and local stress based approaches. Butt welded joints with different weld seam inclinations with respect to applied uniaxial loading were designed to assess the root fatigue strength in higher multiaxial stress ratio regime. The fatigue strength of multi-pass tube-to-plate welded joints subjected to internal pressure only and combined internal pressure and torsion in and 90° out of phase loading was also investigated. Test data generated in this thesis was evaluated together with the test data collected from literature. Last objective of the thesis included investigation of the increased performance in fatigue strength by post weld treatment methods such as HFMI. The behavior of residual stresses induced due to HFMI treatment during fatigue loading is studied. Numerical residual stress estimations and residual stress relaxation models are developed and the effect of various HFMI treatment process parameters and steel grade on the induced residual stress state is investigated. Specimens studied were non load carrying longitudinal attachments and simple plates. Residual stresses in both test specimens were measured using X-ray diffraction technique.QC 20170206
9
Domingo, Eric Ray. "An introduction to Autoclaved Aerated Concrete including design requirements using strength design". Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/543.
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Peng, Jun, i 彭军. "Strain gradient effects on flexural strength and ductility design of normal-strength RC beams and columns". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48329630.
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The stress-strain characteristics of concrete developed in flexure is very important for flexural strength design of reinforced concrete (RC) members. In current RC design codes, the stress-strain curve of concrete developed in flexure is obtained by scaling down the uni-axial stress-strain curve to account for the strain gradient effect. Therefore, the maximum concrete stress that can be developed under flexure is smaller than its uni-axial strength, and the use of which always underestimates the flexural strength of RC beams and columns even though the safety factors for materials are taken as unity. Furthermore, the value of strength underestimation was different for RC beams and columns, which indicates that the extent of strain gradient will affect the maximum concrete stress and stress-strain curve developed under flexure.
To investigate the maximum concrete stress, 29 column specimens were fabricated and tested in this study. They were divided into 9 groups, each of which was poured from the same batch of concrete and contained specimens with identical cross-section properties. In each group, one specimen was tested under concentric load while the rest was/were subjected to eccentric or horizontal load. To study the strain gradient effects, the ratio of the maximum concrete compressive stress developed in the eccentrically/horizontally loaded specimens to the maximum uni-axial compressive stress developed in the counterpart concentrically loaded specimens, denoted by k3, is determined based on axial force and moment equilibriums. Subsequently, the concrete stress block parameters and the equivalent rectangular concrete stress block parameters are determined. It is found that the ratios of the maximum and equivalent concrete stress to uni-axial cylinder strength, denoted respectively by k3 and , depend significantly on strain gradient, while that of the depth of stress block to neutral axis depth, denoted by , remains relatively constant with strain gradient. Design equations are proposed to relate and with strain gradient for strength calculation, whose applicability is verified by comparing the strengths of RC beams and columns tested by various researchers with their theoretical strengths predicted by the proposed parameters and those evaluated based on provisions of RC codes.
Based on the test results, the stress-strain curve of normal-strength concrete (NSC) developed under strain gradient is derived using least-square method by minimising the errors between the theoretical axial load and moment and the respective measured values. Two formulas are developed to derive the flexural stress-strain curve, whose applicability is verified by comparing the predicted strength with those measured by other researchers.
Lastly, the application of the proposed stress-block parameters and stress-strain curve of NSC will be illustrated by developing some charts for flexural strength design of NSC beams and columns. The application will further be extended to develop strength-ductility charts for NSC beams and columns, which enable simultaneous design of strength and ductility. By adopting the proposed design charts, the flexural strength design, as well as that of the plastic hinge forming mechanism during extreme events, will be more accurate. The resulting design will be safer, more environmentally friendly and cost effective.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
11
Meyers, Anthony G. "The determination of rock mass strength for engineering design /". Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phm6134.pdf.
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Batista, Sofia Alexandra Ferreira. "Design and processing of high-strength anorthite/mullite porcelains". Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392540.
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Cuadros, Olave Gladys. "Evaluation of high strength concrete prestressed bridge girder design". Texas A&M University, 2003. http://hdl.handle.net/1969/208.
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Kauffman, Joseph Ulrich IV. "The Xcel Sleeve: Fall Prevention Through Digital Strength Training". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32712.
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In America, a person has a 1 in 3 chance of falling each year once they reach the age of 65. When someone falls, they risk bodily injury. There are products available to help people when they fall, but they are only effective once a person reaches a point where they are at risk of falling. In order to reduce an individualâ s chance of falling as they age, preventive measures must be taken before the problems develop. With the use of digital technology, adults can be properly instructed on how to keep they bodies strong and balanced for there golden years. This thesis documents the research, conceptualization, and development of the Xcel Sleeve.Master of Science
15
Hatch, Gerald L. "Strength evaluation of strut-purlins". Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-05092009-040637/.
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Hennage, John B. "Characterization of a Pressure Sensitive Adhesive (PSA) for Mechanical Design". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35572.
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This thesis outlines a methodology for formatting and applying stress models, collecting visco-elastic material properties, and presenting the material data for use in adhesive joint designs. There are a number of models/theories that can be applied to the design of Pressure Sensitive Adhesive (PSA) joints. Unfortunately, few design engineers are familiar with these models and the models are not formatted in a manner that can easily be applied to joint designs. By developing a format that is based on the existing knowledge of the designer and presenting them in a familiar manner the theories/models can easily be used in joint designs. This technique was demonstrated with Beam-on-Elastic Foundation, Shear Lag, and Shape Factors. Design examples successfully demonstrated the application of all of these models in the analysis and design of simple adhesive joints.
The material properties of PSAs are a function of loading/displacement rate, temperature, relative humidity, and stress state. The Arcanm fixture was used to test VHB™ 4950 over a range loading and stress states including fixed load and displacement rates. Several bond widths were tested to determine the extent of the shape factor effect. A second fixture was used to determine the impact of gradient-tensile stresses on the failure strength.
All of the collected data was used to generate design plots. The strength data was presented as allowable strength envelopes with respect to rate. The moduli were calculated from the load-displacement data and plotted with respect to the displacement rate. The failure strength from the fixed load and displacement data were used to transform from one loading case to the other and a plot was generated. These three plots were used in the design and analysis of several adhesive joints.
The methods demonstrated in this thesis show a great deal of promises as a design tool, but there is still a large amount of work to be done. The design space for this material is much larger than what was covered by this work. Additional strength testing needs to be conducted to fully characterize the material for all key applications. The principle of time-temperature superposition, beam-on-elastic foundation, shear lag, and shape factors all need to be validated for this material.
Master of Science
17
Stater, Lydia M. "Female Friendship: Strength Found Through Support". Kent State University Honors College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1525691709141172.
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Lord, Michael. "Design and modelling of ultra-high strength steel weld deposits". Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/221873.
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Zahn, Franz August. "Design of reinforced concrete bridge columns for strength and ductility". Thesis, University of Canterbury. Department of Civil Engineering, 1985. http://hdl.handle.net/10092/2872.
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Methods for the design of reinforced concrete bridge columns and
piers for strength and ductility are considered. The investigations cover
the following areas.
An experimental investigation of the influence of reinforcing steel
grade and amount of confining steel on the stress-strain behaviour of
confined concrete is presented. The results are discussed and compared
with theoretical models. Special attention is given to the possibility
of fracture of the confining steel.
An extensive experimental investigation into the ductile performance
of a range of reinforced concrete columns is presented. The columns were
subjected to constant axial load and cyclic lateral displacements. The
test units included four square columns with the lateral load applied
in the direction of a cross section diagonal, six circular hollow columns
with different wall thickness to diameter ratios, and four columns with
transverse reinforcement from Grade 380 steel. The available strength and
ductility of the columns is discussed and compared with the performance
of columns tested previously at the University of Canterbury, and with
theoretical predictions using monotonic as well as cyclic moment-curvature
analyses. The main variables for the solid columns were the influence of
biaxial bending, the use of Grade 380 transverse steel for confinement,
and the spacing between transverse bars along the column axis. The
circular hollow columns were unconfined on the inside face of the tube
wall, and the main variables were the influence of the axial load level
and the wall thickness.
The implications of the column test results, including the results
of other investigations, for the design of reinforced concrete columns
for strength and ductility are discussed and, where appropriate, used to
calibrate theoretical models. In particular, the influence of cyclic
loading on the strength deterioration of reinforced concrete columns with
high axial loads is emphasized. More realistic definitions of the ideal
flexural strength, of the flexural overstrength and of the yield curvature
are suggested and, together with a set of criteria for the ultimate limit
state, used to establish design charts for the available strength and
ductility of reinforced concrete columns. A cyclic moment-curvature
analysis was used for this purpose, incorporating cyclic stress-strain
models for the concrete and for the steel, thus taking into account the
cyclic strength deterioration observed for columns with high axial loads.
Finally, a rational step-by-step design procedure is presented that
will make less complex the task of considering the great number of
variables involved in the seismic design of reinforced concrete columns
for both strength and ductility.
20
Liew, Andrew. "Design of structural steel elements with the Continuous Strength Method". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24699.
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The current practice of ultimate limit state design for steel structures involves an elastic--perfectly plastic material model and the classification of cross-sections into discrete behavioural classes. This leads to a design philosophy which is simple, but generally over-conservative. The Continuous Strength Method is a strain based design approach which allows for the beneficial influence of strain hardening. At the core of the method is a base curve which relates the deformation capacity of a cross-section to its cross-section slenderness. Deformation capacity is defined through a strain ratio, which is the ratio of the maximum strain that a cross-section can endure to its yield strain. The formulation for the base curve was derived by means of stub column and bending tests collected from the literature. Knowing the limiting strain and assuming plane sections remain plane, the resistance of cross-sections to combinations of axial load and bending moments can be calculated by integrating the stresses arising from a suitable strain hardening material model over the area of the cross-section. Analytical and design expressions have been developed, and the resistance predictions for open and closed cross-section shapes have been compared with existing collated test data, and shown to give additional capacity over current design approaches, with a reduction in scatter and a more consistent method. Beyond the analysis of the cross-section, the method has been extended to the global instability of pin-ended columns by utilising moment--curvature--thrust curves. The curves were paired with an assumed buckled displacement shape to find applicable equilibrium configurations, and to extract the peak axial loads for producing buckling curves. The column buckling curves showed two distinct regions based on the global slenderness of the column. Firstly a region of global-dominated failure, where the columns failed by a loss of overall flexural rigidity, and secondly a local-dominated failure region, where the mid-height cross-sections failed by local buckling. The local cross-section failure mode allowed for axial loads greater than the cross-section yield loads. The column buckling curves were found to be dependent on the initial out-of-straightness, the cross-section geometry and the material yield stress. An experimental program provided insight into the cross-section resistance of hot-rolled rectangular hollow sections (RHS). The experiments included 32 material tensile coupon tests, eight stub column tests and four simply supported beam tests, and exhibited little strain hardening. Overall, a series of developments to a strain based approach for steel structures has been presented, and areas for future developments have also been highlighted.
21
Al-Azzawi, Hosam Abdullah. "Strength Tuned Steel Eccentric Braced Frames". PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4981.
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The primary component in eccentrically braced frames (EBF) is the link as its plastic strength controls the design of the frame as well as the entire building within which it is installed. EBFs are the first part of building design and every other component is sized based on the forces developed in the link. Oversized link elements lead to the use of unnecessary materials and can increase construction costs. Additionally, the advantages of using a continuous member of the same depth for both the link and the controller beam (in terms of the cost and the time) motivates researchers to find a way to control the link strength in conventional EBFs. Previous studies on the link-to-column connections in EBF have shown that the links are likely to fail before reaching the required rotation due to fractures at low drift level. Moreover, improving the strength of the links in EBF depends primarily on their ability to achieve target inelastic deformation and to provide high ductility during earthquakes. Therefore, in this study, the concept of tuned link strength properties in EBF, T-EBF, is experimentally introduced as a solution to improve the performance of the link in conventional EBF by cutting out an opening in the link web. Furthermore, a new brace-to-link connection is proposed to bolt the brace member with the link in contrast to the conventional method of welding them. This new idea in continuous beam design was investigated to verify the stability of the tuned eccentrically braced frame, either welded or bolted, with a bracing member. A total of four full-scale cyclic tests were conducted to study the ability of T-EBF to achieve inelastic deformation. The specimens have two different cross sections: W18x76 and W16x67, two different sections where the brace was welded to the link, and two other specimens at different sections where the brace was bolted to the link were examined. The experimental results indicate that the link in T-EBF can achieve high rotation, exceeding 0.15 rad, and an overstrength factor equal to 1.5. Failure involved included web buckling at very high rotation. The T-EBF displayed a very good, non-replaceable ductile link. The experiments were followed by an isotropic kinematic-combined hardening model in the finite element analyses (FEA). The FEA analysis is developed to predict the effect of web opening configuration on the local section stresses and strains and global characteristics of the frame. FEA exhibits good agreement with the experimental results and can capture the inelastic buckling behavior of the sections. The link configuration parameters of the T-EBF were studied extensively on a W18x76 shear link subjected to the 2016 AISC seismic design provisions loading protocol (ANSI/AISC 341-16, 2016). The parametric study also included the performance of a range of wide flange sections. The analysis shows that the reduced web section has effect on the plastic strain in which low plastic strain observed near ends and connections and high at the center of the web. Results also demonstrate that if the shear link is appropriately sized with web opening and intermediate web stiffeners provided, an excellent shear link with high ductility under cyclic loads can be obtained. Changing the configuration of the opening cutout also had a significant effect on reducing the transition zone cracks.
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Kelly, Fergal S. "Characterisation and design of fire-resistant steels for construction". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324824.
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Ho, Ching-ming Johnny, i 何正銘. "Inelastic design of reinforced concrete beams and limited ductilehigh-strength concrete columns". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B27500305.
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Allen, Jonathan. "Casting for the voice of strength : Austin Spare and the cultures of cartomancy". Thesis, Kingston University, 2017. http://eprints.kingston.ac.uk/41926/.
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This practice-based PHD project tests cross/trans disciplinary approaches to historical artifacts, set in the field of contemporary fine art research. It is predicated specifically upon my discovery in 2013 of a forgotten deck of fortune-telling cards, hand painted 1906 by the English artist and mystic Austin Osman Spare. Spare's cards had lain unnoticed for almost seventy years within the collection of London's secretive Magic Circle, following their accession to the magic club's museum in 1944; before that date, no record of the deck exists. I respond to this historical find in the form of two interdependent "readings" of the artist's deck of cards. 'Reading One' provides the first in-depth descriptive survey of the deck, as well as establishing its provenance, its place in the artist's oeuvre and within the wider histories of cartomancy. 'Reading Two' adopts complementary approaches that are contingent upon, and shaped by, specific findings within 'Reading One'. These include an elaboration of the deck's release from captivity at The Magic Circle ('Facsimilate and proliferate'), an evaluation of its internal connective logic ('Combinatoric consciousness'), its introduction to the moving image ('Cartomantic cinema') and to historical time ('Making up for lost time'), and the articulation of a card that is missing from the deck ('Casting for the voice of Strength'). The relationship between these two constituent readings is explored as a continuity which follows a cyclical, rather than linear, progression - second readings are contingent upon first but often lead to renewed first readings, leading to renewed second readings and so on. Within this reanimating process, the object can be seen directing its researcher, sometimes casting her/him in particular roles that meet its needs. In the realm of art production, this orientation towards the object implies that the appropriation of historical material by artists be appropriate, with all the psychological, ethical, and political consequences that such encounters entail. While applied here to a single object - Austin Spare's cartomancy deck - the project's model of contingent and continuous knowledge production encourages other researchers to respond innovatively to the directives, even demands of their chosen objects of research.
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Chen, Mantai, i 陈满泰. "Combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206429.
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The stress-strain relationship of concrete in flexure is one of the essential parameters in assessing the flexural strength and ductility of reinforced concrete (RC) structures. An overview of previous research studies revealed that the presence of strain gradient would affect the maximum concrete stress and respective strain developed in flexure. Previously, researchers have conducted experimental studies to investigate and quantify the strain gradient effect on maximum concrete stress and respective strain by developing two strain-gradient-dependent factors k3 and ko for modifying the flexural concrete stress-strain curve.
In this study, the author established a new analytical concrete constitutive model to describe the stress-strain behavior of both normal-and high-strength concrete in flexure with the effect of strain gradient considered. Based on this, comprehensive parametric studies have been conducted to investigate the combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns with concrete strength up to 100 MP a by employing the strain-gradient-dependent concrete stress-strain curve using non-linear moment-curvature analysis.
From the results of the parametric studies, it is evident that both the flexural strength and ductility of RC beams and columns are improved under strain gradient effect. A design value of ultimate concrete strain of 0.0032and anew equivalent rectangular concrete stress block incorporating the combined effects of strain gradient and concrete strength have been proposed and validated by comparing the proposed theoretical strength with the strength of 198 RC beams and 275 RC columns measured experimentally by other researchers. It is apparent from the comparison that the proposed equations can predict more accurately the flexural strength of RC beams and columns than the current RC design codes.
Lastly, for practical engineering design purpose, design formulas and charts have been produced for flexural strength and ductility design of RC beams and columns incorporating the combined effects of strain gradient and concrete strength.published_or_final_version
Civil Engineering
Master
Master of Philosophy
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Vardanega, Paul Joseph. "Strength mobilisation for geotechnical design & its application to bored piles". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610440.
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Barr, Paul J. "Consistent crudeness in prestressed concrete girder design /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10128.
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Chigusa, S., N. Hayakawa i H. Okubo. "Quench-induced dynamic breakdown strength of liquid helium for superconducting coils". IEEE, 2000. http://hdl.handle.net/2237/6763.
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Ho, Ching-ming Johnny, i 何正銘. "Design and detailing of high strength reinforced concrete columns in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31224398.
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Winter, Gerrard Martin. "Determination of the design strength of thin structural veneer cladding panels /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17531.pdf.
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Kim, Bij-Na. "Design and modelling of ultra-high strength steels : nanoprecipitation and plasticity". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245234.
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Understanding the changes occurring in the mechanical properties during martensite tempering is essential in the development of new industrial grades. The aim of this research was to develop new ultra-high strength steels via nanoprecipitation control, which requires an understanding of the processing-microstructure-property relationship in medium carbon (0.5-0.6 wt.%) steels throughout tempering. Much of the work has been centred in understanding the role of silicon at the precipitation level and in the recovery of martensite. By using an existing spring steel grade, the effect of interrupted ageing (IA) in tempered martensite has been studied. In IA, an intermediate step between quenching and tempering is introduced, where quenched martensite is left to rest at room temperature for a defined period of time. By allowing carbon segregation into dislocation cores, the incorporation of IA resulted in a more stable microstructure and hardness improvement. The effect of silicon in the epsilon to cementite carbide transition has also been studied. The classical nucleation theory was applied in order to model cementite formation under paraequilibrium conditions, thus incorporating silicon during nucleation. Characterisation using high energy X-rays showed the inhibiting effect of silicon in the overall cementite precipitation. The second effect of silicon was observed in the martensite recovery. A series of experiments were carried out in order to capture the various microstructural changes taking place during tempering: precipitation, grain size and dislocation density evolution. It was observed that the addition of silicon reduces the rate of martensite recovery, owing to the reduced cross-slip in the ferrite lattice. A plasticity model based on irreversible thermodynamics and EBSD characterisation was applied to identify the effective grain size. The results from these two techniques require further research. Nevertheless, based on the post-failure analysis by TEM, it appears that at relatively early tempering stages, even low angle lath boundaries can contribute to strengthening, where piled-up dislocations have been observed at lath boundaries.
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Bjureland, William. "Analysis of deep excavations using the mobilized strength design(MSD) method". Thesis, KTH, Jord- och bergmekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136584.
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The population in Sweden and around the world is increasing. When population increases, cities become more densely populated and a demand for investments in housing and infrastructure is created. The investments needed are usually large in size and the projects resulting from the investments are often of a complex nature. A major factor responsible for creating the complexity of the projects is the lack of space due to the dense population. The lack of space creates a situation where a very common feature of these types of projects is the use of earth retaining systems. The design of retaining systems in Europe is performed today based on Eurocode. Eurocode is a newly introduced standard for the design of structures and is developed in order to make it easier to work cross borders by using the same principle of design in all countries. For the design of retaining walls in Sweden, Eurocode uses the old standard as the basis of the design procedure consisting of two separate calculations, ultimate limit state and serviceability limit state. Since soil does not consist of two separate mechanisms consisting of failure and serviceability, this approach to solving engineering problems fails to address the real behavior of soils. To handle this problem Bolton et. al. (1990a, 1990b, 2004, 2006, 2008, 2010) developed the theory of “mobilized strength design” where a single calculation procedure incorporates both the calculation of deformations and the safety against failure. The calculation uses conservation of energy and the degree of mobilized shear strength to study deformations in and around the retaining system and the safety against failure in mobilizing the maximum shear strength of the soil. The aim of this thesis was to introduce the theory of mobilized strength design to geotechnical engineers in Sweden working both in academia and in industry. Another aim of the thesis was to develop a tool that could be used to perform calculations of earth retaining systems based on this theory. The development of a working tool has resulted in a Matlab code which can in a simple way be used to calculate both deformations in the retaining system and the safety against failure by using the degree of mobilized shear strength presented in the theory. The Matlab code can handle ground layering with different shear strengths and weights of the soil. A comparison instrument in a Mathcad calculation sheet have been developed to produce results based on the original theory where the feature of soil layering is not incorporated into the calculation procedure. The thesis shows that the Matlab code developed performs well but is not yet sensitive enough to produce the same results as the Mathcad calculation sheet and needs to be further developed to make it more robust in order to handle all different excavation scenarios. v The theory of mobilized strength design has been introduced to geotechnical engineers in Sweden and the thesis studies the theory and shows the calculation procedure and how the different input values and calculations affect the analysis. The thesis also shows some areas in which the theory and the code can be modified and where further research can be performed in order to make them fully applicable to Swedish conditions. As an example the use of rock dowels drilled into the bedrock and attached to the retaining structure is a common feature for deep excavations in Sweden. Further research can be pursued on how to incorporate the energy stored in the rock dowels into the calculation procedure.
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Hu, Wei. "Data-driven metallurgical design for high strength low alloy (HSLA) steel". [Ames, Iowa : Iowa State University], 2008.
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Alameddine, Fadel F. "Seismic design recommendations for high-strength concrete beam-to-column connections". Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185042.
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The present recommendations of the ACI-ASCE Committee 352 for the design of ductile moment resistant beam to column connections limit the joint shear stress to γ√f'(c), where the factor γ is a function of the joint geometric classification and the loading condition. The value of compressive strength f'(c) used in the above expression should not exceed 6000 psi. This limitation causes considerable difficulty in the design of high-strength concrete frames. An experimental study of twelve large-scale exterior beam to column subassemblies was completed at The University of Arizona. The specimens were subjected to cyclic inelastic loading. The variables studied were the concrete compressive strength (8.1, 10.7, and 13.6 ksi), the joint shear stress (1100 and 1400 psi), and the degree of joint confinement provided in the form of closed ties. Although high-strength concrete is more brittle than normal-strength concrete, the study showed that frames constructed of high-strength concrete can perform satisfactorily in earthquakes zones when attention is given to proper detailing of joints. The flexural strength ratio, degree of joint confinement, development length of bars, and joint shear stress are all very important factors to be considered in the design process. The maximum permissible joint shear stress suggested by ACI-ASCE Committee 352 was modified for frames constructed with high-strength concrete. The proposed joint shear stress drawn from test results does not affect the factor γ which depends on the joint type and its geometric classification. Therefore, in the absence of any further data about interior joints, the proposed joint shear limit for high-strength concrete can be used for all types and geometric classifications of joints. Furthermore, new requirements for joint confinement were presented to ensure ductile behavior of frames. It is important to note that current Recommendations for joint confinement, which were developed for normal-strength concrete, cannot be satisfied for high-strength concrete frames. The hysteresis response of specimens tested and other normal-strength concrete specimens tested by different investigators were compared in terms of their energy absorption capacity. This comparison was essential to alleviate concern about the lack of ductility of high-strength concrete. Favorable results were obtained. This research is important for practitioners to gain more confidence using high-strength concrete for structural design applications especially in seismic zones.
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AHMAD, SAJJAD. "Innovative mix design of cementitious materials for enhancing strength and ductility". Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2604771.
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Cement based composites i.e. paste, mortar and concrete are the most utilized materials in the construction industry all over the world. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to their low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses) etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. Therefore, it is necessary to develop such types of cement composites possessing higher resistance to crack growth, enhanced flexural strength and ductility.
The development of new technologies and materials has revolutionized every field of science by opening new horizons in production and manufacturing. In construction materials, especially in cement and concrete composites, the use of nano/micro particles and fibers in the mix design of these composites has opened new ways from improved mechanical properties to enhanced functionalities. Generally, the production or manufacturing processes of the nano/micro sized particles and fibers are energy intensive and expensive. Therefore, it is very important to explore new methods and procedures to develop less energy intensive, low cost and eco-friendly inert nano/micro sized particles for utilization in the cement composites to obtain better performance in terms of strength and ductility.
The main theme of the present research work was to develop a family of new type of cementitious composites possessing superior performance characteristics in terms of strength, ductility, fracture energy and crack growth pattern by incorporating micro sized inert carbonized particles in the mix design of cementitious composites. To achieve these objectives the micro sized inert carbonized particles were prepared from organic waste materials, namely: Bamboo, coconut shell and hemp hurds. For comparison purposes and performance optimization needs, another inorganic waste material named as carbon soot was also investigated in the present research.
The experimental investigations for the present study was carried out in two phases; In the first phase of research work, a methodology was developed for the synthesis of the micro sized inert carbonized particles from the above mentioned organic raw materials. In the second phase of research, various mix proportions of the cementitious composites were prepared incorporating the synthesized micro sized inert carbonized particles. For micro sized inert carbonized particles obtained from bamboo and coconut shell three wt.% additions i.e. 0.05, 0.08, 0.20 were investigated and for particles synthesized from hemp hurds 0.08, 0.20, 1.00 and 3.00 wt.% additions were explored.
The cement composites were characterized by third-point bending tests and their fracture parameters were evaluated. The mechanical characterization of specimens suggested that 0.08 wt.% addition of micro sized inert carbonized bamboo particles enhances the flexural strength and toughness of cement composites up to 66% and 103% respectively. The toughness indices I5, I10 and total toughness of the cement composites were also enhanced. The carbonized particles synthesized from coconut shell resulted in improved toughness and ductility without any increase in the modulus of rupture of the cement composite specimens. Maximum enhancements in I5 and I10 were observed for 0.08% addition of both carbonized and carbonized-annealed particles. For the carbonized hemp hurds cement composites the results indicate that the micro sized inert carbonized particles additions enhanced the flexural strength, compressive strength and the fracture energy of the cement composites.
The microstructure of the cement composites was also studied with the help of field emission scanning electron microscope (FESEM) by observing small chunks of cement composite paste samples. The FESEM observations indicated that the micro sized inert carbonized particles utilized in the mix design of these mixes were well dispersed in the cement matrix. It was also observed that the fracture paths followed by the cracks were tortures and irregular due the presence of micro particles in the matrix. The cracks during their growth often contoured around the inert particle inclusions and resulted in enhanced energy absorption capacity of the cement composites.
The study was further enhanced to the cement mortar composites and their performances were studied. The results indicated that the energy absorption behavior of the composites was enhanced for all the cement composites containing micro carbonized particles.
Finally, it is concluded that the ductility and toughness properties of the cement composites can be enhanced by incorporating the micro sized inert carbonized particles in the cement matrix. The fracture energy, ductility and toughness properties enhancement of the cement composites greatly depends upon the source and synthesis procedure followed for the production of micro sized inert carbonized particles.
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Mujagic, Ubejd. "Strength Calculation Model for Standoff Screws in Composite Joists". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35960.
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The objective of the research reported herein is to present a comprehensive evaluation of all available experimental data from push-out tests utilizing the ELCO Grade 8 standoff screws. The goal is to develop a strength prediction equation and determine reliability parameters compatible with the Load Factor Resistance Design (LRFD) procedure that would allow the use of this shear connector in design of composite floor systems.
The study considers results from push-out tests using this type of screw reported by Hankins et al. (1994), Alander et al. (1998), Webler et al. (2000), and Mujagic et al. (2000). Further, this study identifies the limitations in earlier approaches aimed at predicting the strength of standoff screws. An improved strength prediction model is developed that considers all applicable limit states and determines maximum strength of a connector. A reliability study was also conducted to derive strength reduction factors to be used in design. Parameters considered in the model include deck type and geometry, screw height, concrete compressive strength, top chord angle yield strength, and stand-off screw rupture strength. Results from strength prediction model were compared with results from composite joist tests.Master of Science
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Phillips, Erin Katherine. "Investigation of Required Tensile Strength Predicted by Current Reinforced Soil Design Methodologies". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49246.
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Geosynthetic Reinforced Soil (GRS) is a promising technology that can be implemented
in walls, culverts, rock fall barriers, and bridge abutments. Its use in walls and abutments
is similar to Mechanically Stabilized Earth Walls (MSEW) reinforced with geosynthetics.
Both GRS and MSEW are reinforced soil technologies that use reinforcement to provide
tensile capacity within soil masses. However, the soil theories behind each method and
the design methodologies associated with GRS and MSEW technologies are quite
different.
Therefore, a study was undertaken to compare the required tensile strength predicted by
these various reinforced soil design methodologies. For the purposes of this study, the
required ultimate tensile strength was defined as the ultimate tensile strength needed in
the reinforcement after all applicable factors of safety, load factors, and reduction factors
were applied. The investigation explored both MSEW and GRS. GRS has been made an
FHWA "Every Day Counts" initiative. Due to the push to implement GRS technology, it
is critical to understand how GRS design methods differs from classic MSEW design
methods, specifically in the prediction of ultimate tensile strength required.
A parametric study was performed comparing five different reinforced soil analysis
methods. Two are current MSEW design methods and one was a proposed revision to an
existing MSEW design method. The final two were GRS design methods. These design
methods are among the most current and/or widely used design references in the United
States regarding reinforced soil technology. There are significant differences between the
methods in the governing soil theory particularly between GRS and MSEW design
methods. The goal of the study was to understand which design parameters had the most
influence on calculated values of the required ultimate tensile strength and nominal
"unfactored" tensile strength. A base case was established and a reasonable set of
parameter variations was determined. Two loading conditions were imposed, a roadway
loading scenario and a bridge loading scenario.
Based on parametric study findings, conclusions were drawn about which design
parameters had the most influence for different design methods. Additionally, the
difference in overall predicted required tensile strength was assessed between the various
methods. Finally, the underlying soil theory and assumptions employed by the different
methods and their influence on predicted required tensile strength values was interpreted.Master of Science
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Iqbal, Shoaib, i Zuhaib Ahmad. "Impact of degree or Polymerization of Fiber on Viscose Fiber Strength". Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-20861.
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The aim of the study was to find out the relationship between the DP and the tensile properties of different regenerated cellulose fibers. During the process to make regenerated cellulose fibers from wood, the reduction in DP of cellulose is a necessary process to enable fiber extrusion. The reduction of the DP is usually from 1000 to 350 (Coley 1953). The reduction in DP is necessary, first to make the cellulose soluble, and then further decrease in DP is required to control the viscosity of the solution to minimize the mechanical difficulties during processing faced. It is a fact that the reduction in DP is a compromise which is necessary, as reduction in DP means reduction in tensile properties of the fiber produced. The reduction in DP is optimized to make the process both processing and the final product more feasible. The relation in DP and the strength of the fibers is rather obvious i.e. higher the DP higher the tensile strength, but researchers have different views regarding the relationship. By the experiments performed by us we tried to come to a conclusion regarding the difference in opinions. Different types of regenerated cellulose fibers were collected from various sources. Both wet and dry tenacities of 19 different viscose, bamboo viscose, kupro viscose, modal and Tencel fibers were determined. The fiber linear density was also measured, but for some samples we had to take the fiber density value as provided by the manufacturer, due to the limitation of the instrument regarding the fiber length and low fiber linear density. Then out of all the samples 10 were selected (based on our and company’s interest). SEC analysis was used to determine the DP of the samples. These tests were not carried out by us but by MoRe Research. The results of both the analysis were gathered, analyzed and commented upon.Program: Master Programme in Textile Technology
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Ho, Ching-ming Johnny. "Design and detailing of high strength reinforced concrete columns in Hong Kong". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22331815.
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Laham, Noor. "Episodic DSS tests to measure changing strength for whole-life geotechnical design". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Changes in seabed soil strength due to loading events during the life of a structure, affect the response of the structure to any future event. This change in soil strength due to loading events, in particular cyclic loads, was of great concern in the field of offshore geotechnics during the last decades. Allowing for these changes can have a beneficial outcome on the design. Studying the changes occurring in the soil can be mainly done using large scale centrifuge tests or Laboratory element testing, where the latter proved to be able to successfully illustrate soil strength changes during periods of cyclic loads and reconsolidation.
A new approach of life design known as “the whole life design” has been introduced lately to the industry “. Whole life design embraces the time-varying evolution of actions and resistances to create a continuous assessment of conditions of a structure.
This dissertation studies the possibility of one of the most famous element tests which is the “Direct simple shear testing” to capture the changing in strength under cyclic (i.e., episodic in this context) loads and the settlement of subsea layers for the whole life geotechnical design. The outcome of the DSS testing in addition to outcomes from other previous methods (eg T-bar penetrations and Triaxial testing) can form the basis for a new framework to be adopted in the future for demonstrating a whole life design for subsea structures.
In general, the project introduces the concept of whole-life geotechnical design through practical examples and shed lights on Direct simple shear testing ability to simulate specific cyclic loading scenarios. The topic closes with a discussion of next steps to enable whole-life geotechnical design to be more readily adopted in routine practice where appropriate.
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Tabassum, Javeria, i javeriaajaz@yahoo co in. "Analysis of current methods of flexural design for high strength concrete beams". RMIT University. Civil, Environmental & Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080725.143153.
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Considerable amount of research was carried out into the properties and structural performance of high strength concrete for more than few decades. Whilst this research has produced relevant and useful results, there are several properties of high strength concrete like compressive and tensile strengths, stiffness, durability etc. that need to be evaluated and investigated to determine an accurate representation for the determination of different structural properties of beams made of high strength concrete. For this purpose, an investigation into the behaviour of beams made of higher concrete strengths has been carried out and conclusions drawn for the design of high strength concrete beams in flexure. Experimental data from previous research was considered for the study to establish some understanding of flexural behavior of HSC beams. A number of spreadsheets in Excel were developed using available data and various graphs were plotted to determine the accuracy of the code provisions for calculating the ultimate moment capacity of beams. A study on flexural ductility of beams has been carried out using a computer program FRMPHI which generates moment-curvature curves for the beams. Ductility has been studied using ductility factors. The influence of ductility on the value of the depth of neutral axis has been analysed and discussed. A chapter on the short-term deflection of simply supported high strength concrete beams under instantaneous deflections is presented. This chapter includes analysis of the available formula to calculate deflection to determine if these can be adopted for high strength concrete. Extensive ongoing research on the shear strength of beams by several researchers since many years has lead to the generation of a large body of knowledge. Although each author has analysed the data comparing them with existing relationships, the whole body of information has not been analysed to establish a statistical significance. In this study, regression analysis on experimental data collected from published research is carried a relationship between the different parameters affecting the shear strength of beams. The level of significance of the association between parameters influencing shear strength is also discussed.
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Lambeth, David M. S. M. Massachusetts Institute of Technology. "Design considerations for an indoor location service using 802.11 wireless signal strength". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/47808.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 63-67).
This thesis compares approaches to the problem of discovering a mobile user's location indoors. The particular challenges of location discovery using 802.11 (Wi-Fi) signals and "organically collected" (i.e. user-generated) received signal strength maps are discussed. Several existing and novel localizer algorithms are compared on a database of organically collected data. Features of local Wi-Fi "signatures" which are relevant to location discovery are identified and applied to algorithm design considerations. Future directions for algorithm refinement are discussed.
by David M. Lambeth.
S.M.
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Palanivel, Sivanesh. "Thermomechanical Processing, Additive Manufacturing and Alloy Design of High Strength Mg Alloys". Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849628/.
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The recent emphasis on magnesium alloys can be appreciated by following the research push from several agencies, universities and editorial efforts. With a density equal to two-thirds of Al and one-thirds of steel, Mg provides the best opportunity for lightweighting of metallic components. However, one key bottleneck restricting its insertion into industrial applications is low strength values. In this respect, Mg-Y-Nd alloys have been promising due to their ability to form strengthening precipitates on the prismatic plane. However, if the strength is compared to Al alloys, these alloys are not attractive. The primary reason for low structural performance in Mg is related to low alloying and microstructural efficiency. In this dissertation, these terminologies are discussed in detail. A simple calculation showed that the microstructural efficiency in Mg-4Y-3Nd alloy is 30% of its maximum potential. Guided by the definitions of alloying and microstructural efficiency, the two prime objectives of this thesis were to: (i) to use thermomechanical processing routes to tailor the microstructure and achieve high strength in an Mg-4Y-3Nd alloy, and (ii) optimize the alloy chemistry of the Mg-rare earth alloy and design a novel rare—earth free Mg alloy by Calphad approach to achieve a strength of 500 MPa.
Experimental, theoretical and computational approaches have been used to establish the process-structure-property relationships in an Mg-4Y-3Nd alloy. For example, increase in strength was observed after post aging of the friction stir processed/additive manufactured microstructure. This was attributed to the dissolution of Mg2Y particles which increased the alloying and microstructural efficiency. Further quantification by numerical modeling showed that the effective diffusivity during friction stir processing and friction stir welding is 60 times faster than in the absence of concurrent deformation leading to the dissolution of thermally stable particles. In addition, the investigation on the interaction between dislocations and strengthening precipitate revealed that, specific defects like the I1 fault aid in the accelerated precipitation of the strengthening precipitate in an Mg-4Y-3Nd alloy. Also, the effect of external field (ultrasonic waves) was studied in detail and showed accelerated age hardening response in Mg-4Y-3Nd alloy by a factor of 24.
As the bottleneck of low strength is addressed, the answers to the following questions are discussed in this dissertation: What are the fundamental micro-mechanisms governing second phase evolution in an Mg-4Y-3Nd alloy? What is the mechanical response of different microstructural states obtained by hot rolling, friction stir processing and friction stir additive manufacturing? Is defect engineering critical to achieve high strength Mg alloys? Can application of an external field influence the age hardening response in an Mg-4Y-3Nd alloy? Can a combination of innovative processing for tailoring microstructures and computational alloy design lead to new and effective paths for application of magnesium alloys?
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hung, ching-chang, i 洪慶章. "Optimal Analysis of Strength Design for Transformer". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/78246527567818478361.
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碩士國立臺灣科技大學
機械工程系
92
The equipment of transformers is an important device in the industrial production. The situation of actual stress distribution cannot be exactly analyzed by employing the methods of traditional design. Although the quality of the products is maintained, it is usually achieved with the price of a higher cost of production, which leads to the drop of profit. In order to increase the competitive ability of products and lower the productive cost, the optimal designed strength of transformer’s outer shell is an inevitable trend of reducing the cost while keeping the fine quality. This research is based on the design of whose various sizes of the items and materials’ character of the transformer’s outer shell. 3D CAD software can be applied to show clearly the relative positions and sizes of the parts. Also, taking the advantage of plastic mechanics method and CAE software, operating and analyzing can increase the accuracy of traditional material mechanics that is applied to analyze transformer and to get the distributed situation of stress. In addition, introducing CAD software to analyze model’s parameter definition’s function can rapidly correct or change the size of the model. Using CAE software operation can obtain analytical results fast as well as save the cost of researching and developing transformers. The analytical object of this model is the entity of present productive transformer’s outer shell. In addition to analyzing the model and providing optimal designed parameters, the data of limited element software analysis and the application of Topology Optimization and Electromagnetic analytical theory can correct the designed strength parameter of transformer’s outer shell. By employing stress optimal analysis, the weight of the primitive transformer’s model, 161/23.9KV-60MVA, 161/69KV-200MVA, has been reduced 23.765% and 18.986% respectively. If electromagnetic effect is considered, its structural weight will be reduced 20.876% and 14.964% respectively comparing to the original design.
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"Shear design of reinforced high-strength concrete beams". Universitat Politècnica de Catalunya, 2003. http://www.tesisenxarxa.net/TDX-0328103-122019/.
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HUA, HSIAO LI, i 蕭麗華. "Strength Analysis and Design Optimization of Press Machinery". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/22104475069171138392.
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碩士大葉大學
機械工程研究所碩士在職專班
96
The domestic machinery industry plays an important role in global machinery industry. It provides products of good quality in inexpensive prices to the metal-forming industry of the world. In particular, domestically the stamping and forging press machinery occupies about 20 % of all in terms of the total annual value of output. Nowadays, the prices of various raw materials are continuously rising. Besides, intensive competitions among machinery manufacturers are becoming ever intensive. So, every possible way is required to make one more competitive. Among these, the design optimizations of the various machinery structures should be highly emphasized and actually performed. In the design of various types of machineries, conventional design process normally can not provide accurate evaluation of the structural behavior and usually has problems of over design. To overcome such deficiencies, a computer-aided design and optimization analysis process by commercial software should then be employed not only to assure the quality of design but also to pursue a minimization of weight for reduction of material cost. In this study, a press frame is modeled in COSMOSWORKS. Particular dimensions in such a model are set as the design variables. Taking the total weight of the model as the objective function, this parametric model is subjected to design optimization from which the final optimal dimensions are then obtained. Based on the final model, the static stress distribution can be fully realized when it is loaded by the rated magnitude of force.
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Tseng, Chih-Ming, i 曾志銘. "Design Of Optimal High-Strength Steel Hole Flange". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/28215168058251316159.
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碩士國立高雄應用科技大學
模具工程系
98
Abstract The high-strength steel general application and development technology is to help the progressive die’s maturation, it helps the progressive die could produced a more complex part in the automotive stamping industry, continuously with multi-process within a progressive die. This is cut down reprocessing and cost. On traditional way, reprocessing is required at tapping section by using tapping machine. In this theory is emphasis to have tapping process completed within the die after the completion of flange hole or forming then tapping. This method not only reduced the part on re-processing procedures and necking the production time. This thesis focuses on high-strength steel in a progressive die , the hole flange behavior study when the hole flange at forming process, the flange of the height and thickness are limited by material’s strength. Usually when the hole flange at the forming process , the hole flange is less then desired height, plates is concurred necking or rupture and cause follow process failed. This theory is point out the high-strength steel has a certain thickness of material, a different punch shape and lower aperture size effecting on the material after molding height of the hole flange. This paper appeared the seven different punch shapes contain numerous punch angle and lower piercing diameter under three different sizes, using the finite element analysis theory to analyze the simulation. used CAE at high strength steel HSLA-420 provide by customers to analyze the simulation, analysis data from the simulation and design a prototype to verify, obtained result of the aperture size and punch shape are related to height and thickness of the hole flange. In used theory of Taguchi to find out the best of forming parameters and use this relationship will enable the industry to design the mold for the high-strength steel with a hole flange forming processing, a reference basis.
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Wang, Jhih-Yu, i 王誌育. "Strength Design and Analysis of Dual Purpose Canes". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46173136669604168237.
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碩士崑山科技大學
機械工程研究所
99
Dual purpose cane has double functions of cane and chair. The purposes of the study are mechanisms and machine strength designs of a dual purpose cane. First, we investigated and designed the geometric dimension of cane elements. Secondly, based on the Ergonomic and geometric dimension of cane, this work established the design kinematic constraints and objective function to design the geometry kinematic dimension of cane elements. Furthermore, by using ANSYS Workbench package to analysis the stresses and deflections of a dual purpose cane with given geometry kinematic dimensions, we can change the area dimensions of each cane element to obtain the can strength dimension and ensure their strength was satisfied with strength constraint. Finally, we design a Dual Purpose Cane with three kinematic and strength dimensions.
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HUANG, FU-MIN, i 黃富敏. "Dimensional Design of Lower Limb Strength Training Machine". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/22t594.
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碩士吳鳳科技大學
光機電暨材料研究所
107
The purpose of this study is to analyze the size of the linkage mechanism for the adjustment of the size of the new lower limb training machine. Combined with the basic design principle of the linkage of the mechanism, the size of the new lower limb training machine is designed. By adjusting the length of the size, the training step can be changed, and the training strength can be gradually increased. The simplified four-connected connecting rod will be used to simulate the walking path of the walking, so that the path of the foot is similar to the coupling point of the coupling rod in the four-bar linkage mechanism, and the path of the walking foot can utilize the four-link. The position analysis of the mechanism is analyzed and obtained. The principle of this mechanism is used to design the size of the assisted lower limb training machine, and the step can be gradually adjusted to achieve the progressive effect of the lower limb training.
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Cetkin, Erdal. "Constructal Vascularized Structures for Cooling and Mechanical Strength". Diss., 2013. http://hdl.handle.net/10161/7102.
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This dissertation shows how to use Constructal theory in order to design vascular structures with high cooling performance and mechanical strength. The vascular structures consist of grid, tree and hybrid (grid + tree) designs. The four chapters show how the cooling performance and mechanical strength can be increased by varying the vascular structure embedded in a plate for different models and boundary conditions. Chapter 2 shows that the fastest spreading or collecting flow (i.e. the steepest S curve) is discovered by allowing the tree architecture to morph freely. The angles between the lines of the invading tree architecture can be morphed (changed, selected) such that the overall flow proceeds along the fastest route, covering the greatest territory at any moment. Chapter 3 shows development of vascular designs that provide cooling and mechanical strength at the same time. This concept is illustrated with a circular plate vascularized with embedded channels. Chapter 4 shows how vascular design controls the cooling and mechanical performance of a solid slab heated uniformly and loaded with uniform pressure. Chapter 5 shows that a plate heated by a randomly moving beam can be cooled effectively by fluid that flows through a vasculature of channels embedded in the plate. In sum, constructal design governs the evolution of flow structures that offer flow access and mechanical strength at the same time.
Dissertation