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Inaug-diss.--Greifswald. / Lebenslauf.

A study of existing research shows a need for an investigation of the bond properties of anchorage systems for GFRP bars including; straight, anchor heads and bends. The standard pullout test was modified to improve testing efficiency, accommodate bend tests, as well as reduce variability of concrete properties across specimens. Based on the results of the experimental work it was concluded that the surface profile of GFRP bars influences the post-peak phase of the bond stress-slip curve. It was also found that GFRP bars with anchor heads would still require a considerable embedment length to develop the bars’ full strength. Bend strengths of three GFRP manufacturers were determined to be between 58 and 80% of the strength of the straight portion of the same bar, while the development length of a two legged stirrup was found to be between five and ten times the bar diameter for all bar types.

A study of existing research shows a need for an investigation of the bond properties of anchorage systems for GFRP bars including; straight, anchor heads and bends. The standard pullout test was modified to improve testing efficiency, accommodate bend tests, as well as reduce variability of concrete properties across specimens. Based on the results of the experimental work it was concluded that the surface profile of GFRP bars influences the post-peak phase of the bond stress-slip curve. It was also found that GFRP bars with anchor heads would still require a considerable embedment length to develop the bars’ full strength. Bend strengths of three GFRP manufacturers were determined to be between 58 and 80% of the strength of the straight portion of the same bar, while the development length of a two legged stirrup was found to be between five and ten times the bar diameter for all bar types.

Solar thermal systems have great potential to replace or reduce the dependence of conventional fossil fuel based heating technologies required for space and water heating. Specifically solar domestic hot water systems can contribute 50-75% of the annual thermal load. To date residential users have been slow to purchase and install systems, primarily due to the large monetary investment required to purchase and install a system. Recent innovations in materials design and manufacturing techniques, offer opportunities for the development of absorber plate designs that have the potential to reduce cost, increase efficiency and reduce payback periods. Consequently, this design study was conducted in conjunction with industrial partners to develop an improved absorber based on roll bond manufacturing that can be produced at reduced cost with comparable or greater thermal efficiency. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-09-13 12:36:58.588

<p><font face="Times New Roman" size="4"><font face="Times New Roman" size="4"> <p align="left">The aim of this study is to investigate the repair bond strength of composite resin following micromechanical and chemical means of retention in improving the repair of composite resin specimens.</p> </font></font></p>

The objective of this study was to determine whether the composite bond strength acquired using a single step self-etching bonding system is as or more effective when compared to the two step etch-rinse-bond system at clinically relevant in-vitro standards. A total of 80 extracted human deciduous with at least one intact smooth surface were collected with parental consent. Collected teeth were randomly assigned to one of four treatment protocols (n=20): single step self-etch (Adper Prompt L-Pop, 3M ESPE), two step etch (15s)-rinse-bond (Optibond Solo Plus, Kerr), single step self etch (Adper L Pop, 3M ESPE) with 30s pre-etch, and two step etch (30s)-rinse-bond (Optibond Solo Plus, Kerr). A composite cylinder of uniform shape was bonded to each tooth using the designated adhesive system and specimens were tested with a universal testing machine. Descriptive statistics and statistical analysis was performed. Median shear bond strengths for all specimens, regardless of treatment group, ranged from 3.25 MPa to 43.13 MPa. These values are above suggested minimum clinical required values of 3MPa. A Kruskal-Wallis analysis between treatment groups found statistical significance (p<0.05) for shear bond strength between the groups and both one step system protocols, had higher mean and median shear bond strength values than the two step systems. An adhesive remnant index (ARI) was analyzed to confirm uniform adhesive fracture between all four treatment groups. Both a Fisher’s exact test, and a Hantel-Haenszel statistic found no significant difference (p<0.05) between the samples. Based on these findings we concluded that: 1. The ARI score for all treatment groups was not statistically significant, suggesting that the type of bond breakage was consistent regardless of adhesive system used. 2. Both Optibond Solo Plus and Adper Prompt L-Pop systems achieve adequate shear bond strengths as described by current literature. 3. The use of a one-step system to save chair time and aid in patient behavior management may be clinically useful.

No description available.

Experimental and analytical research has been conducted to investigate the degradation of shear performance of beams due to bond deterioration and longitudinal bar cutoffs. To achieve the controlled rate of bond degradation, the method of adjustment of the rib height by machining was adopted. Bond behaviour of the milled bars were measured in tension stiffening tests with internally installed strain gauges. Maximum bond stresses for the milled bars were reduced by up to 50% compared to those for normal deformed bar. The bond behaviour of the milled bars were compared with those of the bars subjected to accelerated corrosion. It was confirmed that the stripped bar had the possibility to simulate corroded bars to some extent. Based on the calculations of average tensile stresses in the cracked concrete for each specimen, appropriate tension stiffening factors for each type of bar were suggested and then verified with the 2-dimensional nonlinear finite element analysis program VecTor2. Next, eight simply supported beams were tested. In four of them half of the longitudinal bars were cut off near the supports. Various combinations of normal and machined reinforcing bars were selected for both longitudinal and transverse reinforcement. The predicted shear failure load for the cutoff beam based on the general method for shear design in CSA A23.3-04 was unconservatively estimated. Cutoffs of longitudinal reinforcement resulted in much more significant drops of shear resistance than did bond deterioration of reinforcement. The inclinations of diagonal cracks for the cutoff series were larger than those for the no-cutoff series due to significant concentrations of longitudinal strains near the cutoff locations. Finally modifications to the general shear design method in CSA A23.3-04 were proposed based on the results of VecTor2 analyses for the beam tests. It was found that the influence of bond deterioration on the shear strength of reinforced concrete member can be accounted for by adjusting the tension stiffening factor applied to the equation for β. With respect to bar cutoffs, its influence on shear strength can be expressed by the strain concentration factor applied to the equation for ε_x.