Since concrete bridge deck slabs are much longer in the traffic direction, they experience transverse early-age cracks due to volumetric instability and restraint. In the last decade, the lower cost of the non-corrodible Glass Fiber Reinforced Polymer (GFRP) bars, as alternative to steel reinforcement, has made them attractive to the bridge construction industry. However, low modulus of GFRP bars may lead to wider cracks in GFRP-RC structures. This serviceability issue can be aggravated by harsh environmental conditions. Hence, the main objective of this thesis is to investigate the effect of early-age cracking in restraint bridge deck slabs reinforced with GFRP bars subjected to different environments. This research consists of two phases: an experimental investigation and a numerical study. In the experimental phase, four full-scale cast-in-place slabs reinforced with different longitudinal GFRP reinforcement ratios (0.30, 0.50, 0.70 and 1.1%) and one with steel reinforcement ratio of 0.7% measuring 2500 mm long × 765 mm wide × 180 mm thick were constructed and tested in the laboratory. Three environmental conditions were implemented; normal (laboratory) adiabatic conditions as well as freezing-thawing and wetting-drying cycles. The main test results are presented in terms of cracking pattern, width and spacing, and strains in the reinforcement and concrete. Test results indicated that the minimum reinforcement ratio (0.7%) recommended by CHBDC for bridge deck slabs reinforced with GFRP bars satisfied the serviceability requirements after being subjected to the simulated exposures of normal laboratory conditions, freezing-thawing, and wetting-drying cycles. In the numerical phase of this research, a finite element model (FEM) was constructed using ATENA software package (ver. 5) to simulate the behaviour of the test specimens. According to the FEM results, a reinforcement ratio of 0.45% Carbon FRP (CFRP) can control the early-age crack width and reinforcement strain in CFRP-RC members subjected to restrained shrinkage. Also, the results indicated that changing the bar surface texture (sand-coated and ribbed bars) or concrete cover had an insignificant effect on the early-age crack behavior of FRP-RC bridge deck slabs subjected to shrinkage. However, reducing bar spacing and concrete strength resulted in a decrease in crack width and reinforcement strain. / October 2015

No description available.

Human factor issues related to flight deck automation require thorough knowledge of airline pilots’ perceptions of advanced automated aircraft. This understanding is important in designing effective training programmes and developing the standard operating procedures (SOPs) of an airline that are needed to fly these aircraft safely. The purpose of this study was to identify the core components of advanced flight deck automation and to construct a valid and reliable instrument to measure the perceptions of airline pilots with regard to automated flight deck systems on modern commercial jet aircraft. An Automation Attitude Questionnaire, the AAQ, was constructed and distributed to all the pilots employed at a major South African carrier. The subsequent data, received from 262 respondents, was interpreted and then analysed using the SPSS and StatsPac statistical software packages. Exploratory factor analysis indicated that five distinct factors were responsible for a significant portion of the variability in pilots’ perceptions of advanced flight deck automation systems and training on those systems. After analysis, these factors were labelled ‘comprehension’, ‘training’, ‘trust’, ‘workload’ and ‘design’. The results indicated that those pilots who operated mainly Airbus-manufactured aircraft types had a statistically significantly more positive perception of the design of the automation system than those of their counterparts who flew mainly Boeing-manufactured aeroplanes. Co-pilots who operated primarily on the company’s long-range aircraft expressed significantly more positive perceptions of advanced flight deck automation training than the line captains dedicated to long-range flying. It was found that captains flying the company’s short-range aircraft also held a more positive perception of automation training than captains operating long-range aircraft. The biographical variables of age, years of flying experience and total flying hours, appeared to be negatively related to both the comprehension and training dimensions of advanced flight deck automation. However, the mere opportunity to fly these advanced automated aircraft seemed to affect pilots’ perceptions of these systems more positively than negatively. Finally, the overall responses of the majority of participants in this study were very positive with regard to the five core factors related to perceptions of advanced flight deck automation. It is suggested that future studies of this nature should incorporate a larger sample consisting of cross-cultural carriers in the global industry. This will confirm the external validity of the present study and support the transfer of findings to other airline pilot populations. / Dissertation (MPhil)--University of Pretoria, 2009. / Human Resource Management / unrestricted

Glue laminated wood deck systems are commonly used for bridge decks on girder bridge systems. These decks are usually covered with a hot-mix asphalt wearing surface in conjunction with a bituminized fabric sheet waterproofing membrane. Often cracks occur in the asphalt at the intersection of two adjacent deck panels which limits the useful life of the wear surface, provides a poor riding surface and potentially allows moisture to flow to wooden bridge components. The purpose of this study was to investigate the structural behavior of asphalt/wood/membrane deck systems. This was accomplished experimentally by determining the deflection of bridge deck panels with respect to each other under simulated truck loading. A classical linear analysis model and a finite element analysis model were developed for the deck panel deflections. These analytical results were compared to the experimental results and a value of approximately 0.05 in for the interpanel differential deflection was determined to be a reasonable, conservative value for the typical configuration considered. This deflection was then used to load various asphalt/membrane/ wood configurations to investigate the effectiveness of the arrangement with regards to resisting hot-mix asphalt cracking. It was found that when subjected to repeated deflections of 0.05 in, the following experimental composite bridge deck performed best in terms of reduced cracking: 1) hot-mix asphalt base layer applied directly onto the glulam deck panel; 2) waterproofing membrane placed on the base layer of asphalt; 3) hot-mix asphalt surface layer placed on the waterproofing membrane. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / With the development of the electric mower, an electrical control system is necessary to drive the blades and the traction wheel. This thesis introduces an electrical deck control system. The system includes a high-powered deck controller and a permanent magnet synchronous motor (PMSM). A PMSM control model has been built in MATLAB/Simulink to verify and support the physical design. Three different PWM modulation methods have also been implemented and compared in MATLAB/Simulink. Furthermore, a model for the distribution and features of grass was built based on sampling of Google Street View images. A six-step pulse width modulation (PWM) control strategy was realized using a PIC33 embedded microprocessor. An enhanced closed-loop control system design was implemented to keep a constant blade speed in order to cut grass efficiently.

No description available.

No / This paper presents a numerical investigation into the behaviour of headed shear stud in composite beams with profiled metal decking. A three-dimensional finite element model was developed using general purpose finite element program ABAQUS to study the behaviour of through-deck welded shear stud in the composite slabs with trapezoidal deck ribs oriented perpendicular to the beam. Both static and dynamic procedures were investigated using Drucker Prager model and Concrete Damaged Plasticity model respectively. In the dynamic procedure using ABAQUS/Explicit, the push test specimens were loaded slowly to eliminate significant inertia effects to obtain a static solution. The capacity of shear connector, load-slip behaviour and failure modes were predicted and validated against experimental results. The delamination of the profiled decking from concrete slab was captured in the numerical analysis which was observed in the experiments. ABAQUS/Explicit was found to be particularly suitable for modelling post-failure behaviour and the contact interaction between profiled decking and concrete slabs. It is concluded that this model represents the true behaviour of the headed shear stud in composite beams with profiled decking in terms of the shear connection capacity, load-slip behaviour and failure modes.

Since the use of epoxy coated steel has become mandatory starting in the 1980s, recent studies have shown that epoxy coating does not prevent corrosion, but instead will debond from the steel reinforcement in as little as 4 years (Weyers RE et al, 1998) allowing instead a much more insidious form of corrosion to take place known as crevice corrosion. Therefore, it is important to determine if the nondestructive corrosion activity detection methods are applicable to ECR as well as institute guidelines for interpreting the results. Since the corrosion of reinforcing steel is directly responsible for damage to concrete structures, it is surprising that nondestructive corrosion assessment methods are not part of regular bridge inspection programs such as PONTIS and NBIS. Instead, the inspection and bridge rating guidelines of federally mandated programs such as NBIS are so vague as to allow for a relatively subjective application by the field inspectors. Clear cover depths, resistance, corrosion potentials, linear polarization data, as well as environmental exposure and structural data were collected from a sample of 38 bridge decks in the Commonwealth of Virginia. These structures were further divided in three subsets: bridge decks with a specified w/c ratio of 0.47, bridge decks with a specified w/c ratio of 0.45 and bridge decks with a specified w/cm ratio of 0.45. This data was then correlated to determine which parameters are the most influential in the assignment of NBIS condition rating. Relationships between the non-destructive test parameters were also examined to determine if corrosion potentials and linear polarization are applicable to epoxy coated steel. Based on comparisons of measurements distributions, there is an indication that corrosion potential tests may be applicable to structures reinforced with epoxy coated steel. Furthermore, these conclusions are supported by statistical correlations between resistivity, half cell potentials and linear polarization measurements. Unfortunately, although apparently applicable, as of now there are no guidelines to interpret the results. Based on the linear corrosion current density data collected, no conclusion can be drawn regarding the applicability of the linear polarization test. As far as the NBIS deck rating is concerned, since the inspection guidelines are so vague, age becomes a very easy and attractive factor to the field personnel to rely on. However, this conclusion is far from definitive since the very large majority of structures used in this particular study had only two rating values out of theoretically ten and realistically five possible rating values. / Master of Science

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 391-394). Also available via the World Wide Web.

The purpose of this research was to evaluate the performance history of continuous bridge decks in the State of Georgia, to determine why the current design detail works, to recommend a new design detail if necessary, and to recommend the maximum and/or optimum lengths of continuous bridge decks. The continuous bridge decks have continuous reinforcement over the junction of two edge beams with a construction joint for crack control. The current technical literature and current practices and design procedures were synthesized and summarized. GDOT maintenance reports were reviewed, and field evaluations were conducted to determine the performance of the continuous deck detail. The effects of bridge movement due to thermal strains, shrinkage, and live loads were considered in the analytical studies to better understand the demands placed on the GDOT continuous deck detail. A summary of the design and length recommendations was provided upon completion of the research.