<p> Gaining insight into the pressworking properties of laminated sheet metal is the aim of this work. One of the deformation processes in which the difference in behaviour between single and laminated sheet metal is most distinct and possibly the easiest to analyze is that of pure plastic bending. A bending theory, initially proposed by Crafoord, is further developed to analyze the pure bending of laminated metals. The bending behaviour of single and laminated nonstrain hardening and strain hardening sheets, with and without Bauschinger effect, is treated extensively from a theoretical point of view. </p> <p> Stretch forming, bending and deep drawing tests on laminated sheets are also performed experimentally. It is found that the orientation of the laminated sheet during the deformation process has a significant influence on the bending behaviour and the deep drawability of laminated sheet. The change in deep drawability can be qualitatively predicted from the bending behaviour. </p> / Thesis / Master of Engineering (MEngr)

This thesis describes an investigation into the experimental accuracy of a close-up stereo vision system. Surfaces are measured from any orientation through the synergy of a Coordinate Measurement Machine (CMM) and a custom made stereo vision head. Calibration of the stereo cameras is achieved using bundle adjustment non-linear optimization, commonly used in photogrammetry. Point set registration techniques are used to calibrate the stereo head with respect to the CMM coordinate system. The fully calibrated stereo vision system is used to provide experimental accuracy results under ideal imagining conditions. The system is then applied to the practical problem of sheet metal strain analysis. This problem involves many non-ideal imaging components that affect system accuracy. Experimental results for this non-deal situation are provided in the form of three-dimensional strain distribution plots. / Thesis / Master of Engineering (ME)

The load-carrying capacity of aging bridge members may at times be found insufficient due to deterioration and a historical trend towards increased truck axle loads beyond their design capacity. Structurally deficient bridges are problematic for bridge owners and users because they restrict traffic usage and require bridges to be posted (operate at less than their ideal capacity). Structural deficiency is the primary motivation for bridge owners to retrofit bridges to meet a specified operating demand. It may be required to replace or retrofit a portion or all of a deficient bridge. The replacement of an entire bridge or even a part of the bridge is generally less desirable than a retrofit solution because retrofits are generally a cheaper alternative to the entire replacement of a structure and usually do not require the bridge's closure. Standard strengthening solutions for corroded members include bolting or welding steel cover plates, replacing sections of the girder, or adding external prestressed tendons. However, these methods also have several challenges, including required lane closures, high installation costs, increased dead weight, and continuing corrosion issues. One alternative to conventional retrofits is the use of carbon fiber-reinforced polymer (CFRP) laminates, which can be adhered to increase both strength and stiffness. CFRPs are a highly tailorable material with an extremely high strength-to-weight ratio, ease of installation and can potentially mitigate further corrosion concerns. Fiber Reinforced Polymers (FRPs) have already been widely accepted as a means of retrofitting reinforced concrete structures (AASHTO 2012, 2018a; ACI 2002, 2017; National Academies of Sciences, Engineering 2010, 2019) but have not yet been widely adopted in the steel industry due to the retrofit's material limitations (lower elastic modulus [less than 29,000 ksi], unanswered questions related to debonding, and no unified design or installation guides). However, newly developed materials and manufacturing processes have allowed for the economic development of stiffer CFRP materials suitable for steel structures, such as the high modulus (HM) CFRP strand sheet. This research analytically and experimentally investigates how newly developed HM strand sheets perform in small scale tensile testing and large scale flexural testing (laboratory and in situ testing). During the laboratory testing, these HM strand sheets were compared against normal modulus (NM) CFRP plates to draw conclusions on these different retrofitting materials (strength, stiffness, bond behavior, and applicability of the retrofit). Another central point in examing these different retrofit materials is how CFRPs perform when attached to structural steel with significant corrosion damage. Corrosion damage typically results in a variable surface profile, which may affect a CFRP retrofit's bond behavior. While limited laboratory testing has been conducted on CFRP attached to steel structures with simulated deterioration, the surface profile does not represent realistic conditions. The effects of a variable surface profile on the NM plate material and HM strand sheet were investigated using small scale tensile testing and large scale flexural testing. All the variable surface profiles tested for bond strength were fabricated based on "representative" simulated corrosion samples or on specimens with significant corrosion. Once all the variables pertaining to the new materials and the effect of a variable surface profile on CFRP retrofits had been examined in a laboratory setting, these retrofitting techniques were implemented on deteriorated in-service steel bridge structures. This research was the first to retrofit deteriorated in-service bridge structures with HM CFRP strand sheets in the United States. This in situ testing was used to compare the laboratory test data of an individually retrofitted girder to the behavior of a single girder that had been retrofitted in a bridge structure. This information was used to verify results on the behaviors of strengthening, stiffening, effects on live load distributions, and modeling assumptions of retrofitted bridge structures. The results from the laboratory testing and in situ testing of CFRP retrofits on corroded steel structures were synthesized to provide information on performance and design guidance for future retrofits. This dissertation provides additional information on CFRP retrofits applied to variable surface profiles and provides data on new CFRP materials (HM strand sheets). With this information, Departments of Transportation (DOT) can be confident as to where and when different types of CFRPs are a suitable retrofit material for corroded or uncorroded steel structures. / Doctor of Philosophy / The capacity of aging bridges may at times be found insufficient due to deterioration and a trend towards increased loading. Structurally deficient bridges are problematic for bridge owners and users because they restrict traffic usage and require bridges to operate at less than their intended capacity. Inadequate capacity are the primary motivation for bridge owners to repair (retrofit) bridges to meet specified traffic demands. Repairs usually do not require the bridge's closure to traffic. Standard repairs for corroded steel members include bolting or welding steel cover plates, replacing sections of the girder, or adding external prestressed tendons. However, these methods also have several challenges, including required bridge closures, high installation costs, increased weight, and continuing corrosion issues. One alternative to conventional repairs is the use of carbon fiber-reinforced polymer (CFRP) laminates, which can be adhered to the deteriorated members to increase strength and stiffness. CFRPs are an extremely versatile material with high strength, high stiffness, ease of installation and can potentially mitigate concerns about further corrosion. Fiber Reinforced Polymers (FRPs) have already been widely accepted as a means of retrofitting reinforced concrete structures(AASHTO 2012, 2018a; ACI 2002, 2017; National Academies of Sciences, Engineering 2010, 2019) but have not yet been widely adopted in the steel industry due to the lack of literature and economical implementation of the CFRPs on steel. However, over the past 20 years, research has been completed on the application of CFRPs on steel, and newly developed materials were created for the economic implementation of CFRP materials suitable for steel structures. In particular, this material is a high modulus (HM) CFRP strand sheet, which has a higher stiffness than a conventional CFRP. This research investigated how newly developed HM strand sheets perform in small-scale laboratory testing and large-scale laboratory testing. Where material strengths, bondability, and the efficacy of different repairs were examined against conventional means on steel structures with and without corrosion deterioration. Once all the variables pertaining to the new materials and the effects corrosion had on CFRP retrofits had been examined in a laboratory setting, these retrofitting techniques were implemented on a deteriorated in-service steel bridge structure (field study) that required repair. This research was the first to repair deteriorated in-use bridge structures with HM CFRP strand sheets in the United States. This information was used to verify results on the material's behavior. The laboratory testing and field testing of CFRP retrofits on corroded steel structures were summarized to provide information on performance and design guidance for future retrofits. This dissertation provides additional information on CFRP repairs applied to corroded steel and provides data on new CFRP materials (HM strand sheets). With this information, Departments of Transportation (DOT) can be confident as to where and when different types of CFRPs are a suitable retrofit material for corroded or uncorroded steel structures.

The conventional design methods for sheet-pile cellular cofferdams were developed in the 1940's and 1950's based on field and limited experimental observations. The analytical techniques of the day were unable to account for the complexities involved. The procedures used only rudimentary concepts of soil-structure interaction which do not exhibit the true response of the cofferdam for most circumstances. During the past decade it has been demonstrated that with proper consideration of the soil-structure interaction effects, the two-dimensional finite element models can be powerful tools in the investigation of cellular cofferdam behavior. However, universal implementation of the findings of these analyses was difficult to justify, since uncertainties remain about the assumptions made in arriving at the two-dimensional models. The only way to address these uncertainties was to perform a three-dimensional analysis. This investigation has focused on the study of the three-dimensional behavior of Lock and Dam No. 26 (R) sheet—pile cellular cofferdam. The work involved the development of a new three-dimensional soil-structure interaction finite element code for cellular cofferdam modeling, and the application of the new code to the study of the behavior of the first- and second-stage cofferdam at Lock and Dam No. 26 (R). The new code was used to study the cell filling process where the main cell is filled first with the subsequent filling of the arc cell. The finite element results show that interlock forces in the common wall were 29 to 35 percent higher than those in the main cell which are less than those calculated by conventional methods and compare well with the observed values. After cell filling, the new code was used to model the cofferdam under differential loading due to initial dewatering of the interior of the cofferdam and changes in river levels. The finite element analysis results show that increasing differential water loads cause the confining stresses in the cell fill to increase which results in a decrease in the level of mobilized shear strength in the cell fill. This explains why the cellular cofferdam can withstand extremely high lateral loads and lateral deformations without collapsing. / Ph. D.

Hot-rolled sheet piling has long-been believed to have a better flexural performance than cold-formed sheet piling based on a test conducted by Hartman Engineering twenty years ago. However, cold-formed steel can have similar strength to the hot-rolled steel This experimental program studied the flexural behavior of hot-rolled and cold-formed steel sheet pilings. This program quantified the influence of transverse stresses from soil pressures on the longitudinal flexural strength. Four cross-sections with two pairs of equivalent sectional modulus were investigated. Sheet-piling specimens were subjected to simulated soil pressure from an air bladder loaded transversely to their longitudinal axis. The span lengths were varied, while the loading area remains unchanged to examine the effect of different transverse stresses. Lateral bracings were provided at discrete locations to establish a sheet piling wall behavior and allow the development of transverse stresses. Load-pressure, load-deflection, load-strain, and moment-deflection responses were plotted to demonstrate the behavior of each specimen. The moment-deflection curves were then normalized to the corresponding yield stress from tensile coupon tests to make a meaningful comparison. The results indicate that transverse stresses influence the flexural capacity of the sheet pilings. The longer span length has less amount of transverse strains, resulting in a higher moment capacity. The hot-rolled sheet pilings have better flexural performance also because of less transverse strains. / Master of Science / Sheet piling wall is an essential structure used during the excavation process. Sheet piling can be hot-rolled and cold-formed. Hot-rolled sheet piling has long-been believed to have a better bending performance based on a test conducted by Hartman Engineering twenty years ago. However, cold-formed steel can have similar strength to hot-rolled steel. This experimental program studied the bending behavior of hot-rolled and cold-formed steel sheet pilings. This program quantified the influence of lateral loading from soil pressure on the moment capacity of the sheet piling. Four cross-sections with two pairs of equivalent bending properties were investigated. Sheet-piling specimens were set up as beam members and subjected to simulated soil pressure from an air bladder. The span lengths of the specimens were varied, while the loading area remains unchanged to examine the effect of different amounts of load. Lateral bracings were provided at discrete locations to establish a sheet piling wall behavior and allow local deflection of the cross-section. Load-pressure, load-deflection, load-strain, and moment-deflection responses were plotted to demonstrate the behavior of each specimen. The moment-deflection curves were then normalized to the corresponding material property of each specimen to make a meaningful comparison between different specimens. The results indicate that lateral loading of the soil pressure influences the bending capacity of the sheet pilings. The longer span length has less amount of transverse strains, resulting in a higher bending capacity. The hot-rolled sheet pilings have better bending performance also because of less transverse strains.

The classical use of 0.3 for the static coefficient of friction for sheet pile interlocks was investigated in this study. The effects of cyclic displacements on the coefficient of friction of the interlocks was also examined. A broad range of values for the coefficient of friction was observed for over 2000 observations of the shear force required to initiate interlock displacement. The mean observed value of the coefficient of friction was greater than 0.3 for low interlock stress. The mean coefficient of friction decreased with increased interlock stress. At interlock loads of five kips per inch the mean coefficient of friction was approximately equal to 0.3. The relationship between interlock stress and the coefficient of friction was found to be nonlinear. An exponential model to predict the coefficient of friction for interlock loads between 1 and 5 kips per inch was developed. To study the effects of cyclic displacements on interlock friction the specimen interlocks were displaced approximately one hundred times. No significant effect on interlock friction was observed. / M.S.

No description available.

Recent work suggests an emerging new paradigm for the Scandinavian ice sheet (SIS); one of a dynamically fluctuating ice sheet. This doctoral research project explicitly examines the history and dynamics of the SIS at four sites within Sweden and Norway, and provides results covering different time periods of glacial history. Two relatively new dating techniques are used to constrain the ice sheet history: the optically stimulated luminescence (OSL) dating technique and the terrestrial cosmogenic nuclide (TCN) exposure dating technique. OSL dating of interstadial sediments in central Sweden and central Norway indicate ice-free conditions during times when it was previously inferred the sites were occupied by the SIS. Specifically, the SIS was absent or restricted to the mountains for at least part of Marine Isotope Stage 3 around 52 to 36 kyr ago. Inland portions of Norway were ice-free during part of the Last Glacial Maximum around 25 to 20 kyr ago. Consistent TCN exposure ages of boulders from the Vimmerby moraine in southern Sweden, and their compatibility with previous estimates for the timing of deglaciation based on radiocarbon dating and varve chronology, indicate that the southern margin of the SIS was at the Vimmerby moraine ~14 kyr ago. In central Sweden, consistent TCN ages for boulders on the summit of Mt. Åreskutan and for the earlier deglaciated highest elevation moraine related to the SIS in Sweden agree with previous estimates for the timing of deglaciation around 10 ka ago. These results indicate rapid decay of the SIS during deglaciation. Unusually old radiocarbon ages of tree remains previously studied from Mt. Åreskutan are rejected on the basis of incompatibility with consistent TCN ages for deglaciation, and incompatibility with established paleoecological and paleoglaciological reconstructions. Altogether this research conducted in different areas, covering different time periods, and using comparative geochronological methods demonstrates that the SIS was highly dynamic and sensitive to environmental change. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

No description available.

Geomorphological evidence of glaciations exist for the Last Glacial Maximum (about 20 kyr ago). At this time, both North America and Eurasia were covered by extensive ice sheets which are both absent today. However, the temporal and spatial evolution of the ice sheets from the previous interglacial up to the fully-glaciated conditions at LGM is still unresolved and remains a vexing question in climate dynamics. The evolution of ice sheets is essentially controlled by the prevailing climate conditions. On glacial time-scales, the climate is shaped the by the orbital variations of the Earth, but also by internal feedbacks within the climate system. In particular, the ice sheets themselves have the potential to change the climate within they evolve. This thesis focuses on the interactions between ice sheets and the time-mean atmospheric circulation (stationary waves). It is studied how the stationary waves, which are forced by the ice-sheet topography, influence ice-sheet evolution through changing the near-surface air temperature. In this thesis, it is shown that the degree of linearity of the atmospheric response controls to what extent the stationary waves can reorganise the structure of ice sheet. Provided that the response is linear, the stationary waves constitute a leading-order feedback, which serves to increase the volume and deform the shape of ice sheets. If the stationary-wave response to ice-sheet topography is nonlinear in character, the impact on the ice-sheet evolution tends to be weak. However, it is further shown that the amplitude of the nonlinear topographical response, and hence its effect on the ice-sheet evolution, can be significantly enhanced if thermal cooling over the ice sheets is taken into account. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.