Fifteen splice specimens reinforced with plain steel bars, including three specimens instrumented with both steel and concrete strain gauges, were tested under monotonically applied four-point loading to develop a database of reliable bond test results and contribute to the development of a reliability based bond provision for plain steel bars to evaluate historical concrete structures. The maximum applied load for the specimens and their observed failure behaviour are reported. In addition to that, a strain compatibility analysis, average bond stress distribution, and flexural section analysis within the lap splice length of the instrumented specimens are also reported.<p> All of the specimens failed in bond within the lap splice length. The load capacity of two specimens reinforced with plain steel bars was 60% of the reported load resistance of specimens with identical geometry and reinforced with deformed bars. The CEB-FIP Model Code provisions for average bond stress of plain steel bars underestimated the maximum applied load recorded for the tested specimens by 16% on average. An empirically derived equation to predict the bond capacity of plain steel bars was determined to be proportional to both the splice length and the nominal bar diameter. <p> Observed cracks in the shear spans remained vertical and suggest the development of arch action within this region. The formation of a large crack at one end of the lap splice length and a review of the load versus deflection behaviour indicated a sudden bond failure of the specimens. Removal of concrete cover at the ends of the lap splice length following testing of the specimens showed evidence of slip of the lapped bars.<p> Instrumented splice specimens provided evidence of bond loss within the lap splice region. As-measured steel strains were higher than those measured for the surrounding concrete due to a loss of strain compatibility. The average bond stress distribution within the lap splice length became more uniform as the applied load approached the maximum applied load. The flexural analysis calculated based on concrete strains above the neutral axis and steel strain provided a reasonable estimate of specimen capacity.

An experimental program was performed for qualitative and quantitative comparison of the maximum tensile resistance of contact and non-contact lap spliced bars in reinforced concrete block masonry using double pullout and wall splice specimens. A total of 32 specimens were tested, consisting of an equal number of double pullout specimens and full-scale wall splice specimens. Both specimen types had the identical cross-section. Eight replicate specimens for each specimen type were constructed with both contact and non-contact lap splice arrangements. Grade 400 deformed reinforcing bars with a 300 mm lap splice length were provided in all specimens. The double pullout specimens were tested applying direct tension to the lapped reinforcing bars. The splice resistance and displacement were recorded during testing. All double pullout specimens with contact lap splices developed, as a minimum, the yield strength of the reinforcing bars and generally displayed evidence of a yield plateau. In contrast, the double pullout specimens with non-contact lap splices failed when only 46.1% of the theoretical yield strength of the reinforcing bars was recorded as the maximum splice resistance. The difference between the average value of the tensile resistance in the contact and non-contact spliced bars was identified as being statistically significant at the 95% confidence level. Wall splice specimens were tested under a four-point loading arrangement with the lapped bars located in the constant moment region. The applied load and specimen deflection were recorded until failure occurred. A numerical analysis was then performed to calculate the maximum resistance of the spliced bars. The specimens with contact lap splices developed the theoretical yield capacity of the reinforcing bars. In contrast, the wall splice specimens with non-contact lap splices developed an average tensile resistance of 78% of the theoretical yield capacity. The difference between the average tensile resistances of the lapped bars in the two splice arrangements was identified as being statistically significant at the 95% confidence level. On average, the contact and non-contact lap spliced bars in the double pullout specimens developed 8.47% and 41.2% less tensile resistance, respectively, as compared to the wall splice specimens with the identical splice arrangement. Both differences were identified as being statistically significant at the 95% confidence level. Bond loss between the reinforcing bars and the surrounding grout was identified as the failure mode for both the double pullout and wall splice specimens with contact lap splices. In contrast, bond loss at the masonry block/grout interface was observed along the non-contact lapped bars in both specimen types, as identified by visual observations upon removal of the face shell and the surrounding grout. Based on the test results of the wall splice specimens with non-contact lap splices, a correction factor of 1.5 is suggested when calculating the effective splice length for the non-contact splice arrangement as tested.

We report the application of our rhodium-catalyzed nucleophilic ring-opening methodology to the enantioselective synthesis of nitrogen-substituted polycyclic heterocycles. By using a cationic Rh(I) triflate catalyst in the presence of the chiral Josiphos ligand PPF-PtBu2, the ring opening reactions on dihydrooxaquinoline and dihydrooxaisoquinoline using different nucleophiles afford access to multiple dihydroquinolines and dihydroisoquinolones in high yield and high enantioselectivity (up to 99% total yield and >99%ee). A variety of nucleophiles were shown to be compatible with the catalytic system. The electronic effects in the new ring opening reactions were investigated using a variety of nucleophiles. It was found that reactivity and enantioselectivity of the ring opening products depends on the electronic effects as well as the position of the substituents on the substrates. Good yields and high ee of regioisomeric products are obtained using electron donating substituents, whereas electron withdrawing substituents decelerate the reactions.

We report the application of our rhodium-catalyzed nucleophilic ring-opening methodology to the enantioselective synthesis of nitrogen-substituted polycyclic heterocycles. By using a cationic Rh(I) triflate catalyst in the presence of the chiral Josiphos ligand PPF-PtBu2, the ring opening reactions on dihydrooxaquinoline and dihydrooxaisoquinoline using different nucleophiles afford access to multiple dihydroquinolines and dihydroisoquinolones in high yield and high enantioselectivity (up to 99% total yield and >99%ee). A variety of nucleophiles were shown to be compatible with the catalytic system. The electronic effects in the new ring opening reactions were investigated using a variety of nucleophiles. It was found that reactivity and enantioselectivity of the ring opening products depends on the electronic effects as well as the position of the substituents on the substrates. Good yields and high ee of regioisomeric products are obtained using electron donating substituents, whereas electron withdrawing substituents decelerate the reactions.

Online communities thrive on their members participation and contributions. Continuous encouragement of participation of these members is vital for an online community. Social visualizations are one of the methods to make members explicitly aware of their connections and relationships. There are numerous ways to visually represent information, current-status, power, and acceptance of members in an online community. In this thesis I present a design of a visualization representing the evolving reciprocity of relationships among users based on the comments they give to each others posts. The purpose of the visualization is to emphasize and hopefully trigger a common bond in the community and thereby increase their participation. We developed and deployed the visualization in an online community called WISETales where women in science and engineering share personal stories. We also deployed modified and improved versions of the visualization in two other communities, I-Help class discussion forums and the Vegatopia discussion forum for vegetarians. In this thesis we present the results of the evaluation in these three communities. The results unfortunately, were negative. Even though separate explanations for the lack of motivational effect can be found in each of the experiments, it seems that the chosen motivational approach was too gentle to encourage participation. It seems for reciprocation to take place, the users need to be committed to the community and already have some other underlying motivation to participate actively. The visualization also should provide some new information that they werent aware of previously. This was not the case with the users in the three chosen communities. WISETales was too new and can barely be called a community. I-Help was not a community, but a place for student to post questions for the teacher to answer. Vegatopia, in contrast, is well established, active community, where people know each other, and engage in conversations with each other. The visualization did not provide any new information for them that they didnt know and only served as a brief attraction for a day (novelty effect). We are still optimistic, however, that the visualization may be useful for active and too dynamic communities where people are unaware of their social relationships because they are too many, for example, social network sites like Twitter.

Understanding stock-bond return correlation is a key facet in asset mix, asset allocation and in an investor’s portfolio optimisation strategy. For the last couple of decades, several studies have probed this cardinal relationship. While initial literature tries to understand the fundamental pattern of co-movements, later studies aim to model the economic state variables influencing such time-varying volatility behaviour of stock-bond returns. This study provides a systematic literature review in the field of stock and bond return correlation. The review investigates the existing literature in three key dimensions. First, it examines the effect of macro-economic variables on SB return co-movements. Second, it illustrates the effect of financial integration on the asset correlation dynamics. Third, it reviews the existing models that are employed to estimate the dynamic relationship. In addition to the systematic review, I conduct an empirical analysis of stock-bond return co-movements on U.S. capital market. Both the literature and the empirical investigation substantiate my claims on existing research gaps and respective scope for further research. Evidence shows that existing models impose strong restrictions on past stock-bond return variance dynamics and yield inconclusive results. I, therefore, propose an alternative method, i.e. copula function approach, to model stock and bond time-varying co-movements. Since the previous studies largely focus on developed economies, I suggest an empirically investigation of emerging economies as well. This will allow me to examine the effect of financial integration on the dynamic asset return correlation. Apart from this academic contribution, the study provides an illustration of the economic implications which relate to portfolio optimization and minimal-risk hedge ratio.

This dissertation first investigates the possible house price trend and the relationship with the mortgage market, from the perspective of risk management; then it chooses the angle from bond insurers and figures out possible methods to avoid capital procyclicality. In Chapter I, we apply vector auto regression models (VAR) and simultaneous equations models (SEM) to estimate the dynamic relations among house price returns, mortgage rates and mortgage default rates, using historical data during the time period of 1979 through second quarter 2008. We find that house prices would be better estimated and predicted with the consideration of the mortgage market. In Chapter II, following the methodology of co-integration, we first construct several succinct measures to display the possible intrinsic values of house prices. In the short run, house price return dynamics are investigated by dynamic adjustments following Capozza et al (2002) and error correction models. We examine the possible overshooting problem of house price returns. By analytical derivations and simulations, we demonstrate the effects of the coefficients on overshooting. In Chapter III, we adopt a structural model with time-varying correlations for bond insurers. We consider losses due to bond insurers’ downgrading and losses from both insurance contracts and investment portfolio. On that basis, we propose forward-looking smoothing rules of capital over a full business cycle, instead of only based on a short-term horizon, to avoid the procyclicality. With the smoothed capital, a bond insurer can actually establish some capital buffer in good times to support the potential losses in crisis.

The formation of aberrant disulfide bonds is a structural consideration for the manufacturing of the extracellular domain of human CD83 (hCD83ext), a potential therapeutic protein. In certain instances, hCD83ext protein products, even when stored frozen, tend to dimerize or even multimerize through the formation of aberrant intermolecular disulfide bonds. Herein, we discovered an analytical inconsistency and applied a modified sample preparation protocol for proper structural analysis of hCD83ext products which are heterologously expressed in Escherichia coli and subsequently purified. In addition, a mutant derivative with the Cys100Ser mutation was identified as an improved version which did not form dimers or multimers. The identification of this mutant variant as a more potent therapeutic protein than other hCD83ext species demonstrated that the structural variation associated with disulfide bond formation can be a critical issue for rigorous control of the quality and bioactivity of therapeutic proteins. The application of this mutant variant for protein therapeutic is currently under exploration. As a comparative study, the hCD83ext was expressed as a glutathione-S-transferase (GST) fusion in two E. coli B strains, i.e. BL21 and Origami B having a reductive and oxidative cytoplasm. The final therapeutic products of hCD83ext produced by the two expression hosts exhibited significant differences in protein conformation and molecular properties, which presumably resulted from different disulfide patterns. The study highlights the importance of developing proper host/vector systems and biomanufacturing conditions for the production of recombinant therapeutic proteins with a consistent product quality. Cys27 in the hCD83ext was identified as a target for molecular manipulation. Two E. coli strains of BL21(DE3) and Origami B(DE3) were used as the expression host to produce the Cys27 mutants. It was observed that Cys27 was involved in the in vivo formation of intramolecular disulfide bonds when hCD83ext was expressed in Origami B(DE3). The Origami-derived protein products had a higher tendency than the BL21-derived counterparts for multimerization via the in vitro formation of intermolecular disulfide bonds. Various analyses were conducted to identify the structural differences among these mutant variants. Most importantly, molecular stability was enhanced by the Cys27 mutations since the Cys27 mutants derived from either BL21 or Origami were much less susceptible to degradation compared to wild-type hCD83ext. This study highlights the implications of aberrant disulfide bond formation on the production of therapeutic proteins. To address an inconsistent bioactivity issue that is primarily due to the aberrant formation of disulfide bonds associated with the presence of five cysteine residues, i.e. AA 27, 35, 100, 107, and 129, the molecular role that each cysteine plays upon the formation of intramolecular or intermolecular disulfide bonds was characterized, using various hCD83ext mutant variants derived by two E. coli expression hosts, i.e. BL21(DE3) and Origami B(DE3). Among the five cysteines, Cys100 and Cys129 can act as a bridging cysteine for in vitro multimerization via the formation of intermolecular disulfide bonds. The multimerization can be alleviated to some extent with less free Cys129 residues, associated with the possible formation of Cys27-Cys129 intramolecular disulfide bond. As a result, introducing the Cys27 mutation can increase the multimerization presumably via freeing more Cys129 residues. In addition, protein stability can be improved in the presence of the Cys27 mutation. The formation of the Cys27-Cys129 intramolecular disulfide bond appears to be more effective in the presence of the Cys100 mutation, resulting in the suppression of multimerization. The two conserved cysteine residues, i.e. Cys35 and Cys107, can be potentially linked to form an intramolecular disulfide bond, particularly when the protein is produced in Origami B(DE3).

Over the past decade, extensive research has been conducted on the strengthening of reinforced concrete (RC) structures using externally bonded fibre reinforced polymer (FRP). More recently, near-surface mounted (NSM) FRP reinforcement has attracted an increasing amount of research as well as practical applications. In the NSM method, grooves are first cut into the concrete cover of an RC element and the FRP reinforcement is bonded inside the groove with an appropriate filler (typically epoxy paste or cement grout). The FRP reinforcement is either prestressed or non-prestressed depending on the required level of strengthening. In all cases, the bond between an NSM bar and the substrate material plays a key role in ensuring the effectiveness of NSM strengthening. The present work investigated experimentally the bond behaviour of non-prestressed and prestressed beams reinforced with near surface mounted carbon fibre reinforced polymer (CFRP) bars under monotonic and fatigue loading. Forty concrete beams were cast and tested in seven groups. The test variables considered in this study were: presence of internal steel reinforcement or not, the type of CFRP rod (spirally wound or sand coated) and the prestressing force (non-prestressed or prestressed). Twenty eight beams were strengthened with non-prestressed CFRP rods; fifteen beams without internal steel reinforcement and thirteen beams with internal steel. Ten beams with internal steel were strengthened with prestressed CFRP rods. The beams were tested in four point bending. In each group, one beam was loaded monotonically. The remaining beams were loaded under different fatigue load levels. The minimum load was kept constant for all beams at 10% of their monotonic capacity and the peak load was varied from one beam to another (denoted as a percentage of the peak load level). Twenty eight beams were strengthened with non-prestressed CFRP rods. Bond failures for the beams with and without internal steel, strengthened with CFRP rods and tested under monotonic or fatigue loads was by debonding between the CFRP rod and the epoxy that started at the loading point and as the load was increased or cycled, the debonding spread towards the support until failure occurred. A comparison of the fatigue life curves for the beams with and without steel, strengthened with CFRP rods revealed that the sand coated rod had better bond characteristics than the spirally wound rod (at the same load range the beam strengthened with sand coated rod had a longer life than the beam strengthened with spirally wound rod). Beams with internal steel, strengthened with CFRP rods and tested under fatigue loading failed in bond at high load levels (short fatigue lives) and by rupture of the steel rebar at low load levels (long fatigue lives). Ten beams with internal steel were strengthened with prestressed CFRP rods. The CFRP rods were prestressed to a force of 62 kN which corresponds to 45% and 40% of the monotonic capacity of the spirally wounded and sand coated rods, respectively. Almost all the beams with internal steel that were strengthened with prestressed CFRP rods failed by slipping between the CFRP rod and the epoxy that started at the support and propagated inwards towards the loading point. The exception to this was the beam strengthened with prestressed sand coated rod and tested under monotonic loading that failed by debonding between the CFRP rod and the epoxy that started at the loading point and propagated towards the support. Comparing the load range (kN) versus life curve for the beams with steel, strengthened with prestressed spirally wound and sand coated rods that failed in bond, shows that the beam strengthened with sand coated rod has longer fatigue lives than beam strengthened with spirally wound rod. A model was used to describe the progress of the debonding crack until excessive slipping occurred. The model predicted the number of cycles until excessive slipping between the CFRP rod and the epoxy occurred and the forces in the CFRP rod at all locations in the shear span at the onset of failure with reasonable accuracy.

Sustainable resource management and development have been at the forefront of important issues concerning the construction industry for the past several years. Specifically, the use of sustainable building materials and the reuse and recycling of previously used building materials is gaining acceptance and becoming common place in many areas. As one of the most commonly used building materials in the world, concrete, composed of aggregate, sand, cement and water, can be recycled and reused in a variety of applications. Using crushed concrete as fill and subgrade material under roads, sidewalks and foundations has been the most common of these applications. However, research has been ongoing over the past 50 years in many countries including Germany, Canada, Japan, the United States, China, and Australia investigating the use of crushed concrete from demolished old concrete structures to fully or partially replace the virgin aggregate used to produce new concrete for use in building and pavement applications. Producing concrete using recycled concrete aggregates (RCAs) has several advantages, namely, the burden placed on non-renewable aggregate resources may be significantly decreased, the service life and capacity of landfill and waste management facilities can be extended, and the carbon dioxide emissions and traffic congestion associated with the transport of virgin aggregates from remote sites can be reduced. This research is directed at benchmarking typical RCA sources for usage in structural concrete and investigating the inter-relationships between aggregate properties, concrete properties and the bond properties between reinforcing steel and RCA concrete. The experimental program focused on four main areas: aggregate properties testing, development of concrete mixture proportions, concrete fresh and hardened properties testing, and beam-end bond testing. Four coarse aggregate sources were investigated including one virgin or natural aggregate (NA) source, and three RCA sources. Two RCA sources were derived from the crushing of decommissioned building and pavement structures (RCA-1 and RCA-2) while the third source was derived from the crushing of returned ready-mix concrete (RCA-3). A variety of typical and non-typical aggregate tests were performed to provide a basis for correlation with fresh and hardened concrete properties results. A total of 24 concrete mixtures were developed and divided into three separate categories, 1) control, 2) direct replacement, and 3) strength-based mixtures. The control mixtures were proportioned to achieve compressive strengths of 30, 40, 50 and 60MPa with slump values between 75 and 125 mm and served as a basis for comparison with the RCA concrete mixtures. The direct replacement mixtures were developed to investigate the effect that fully replacing (i.e., 100% replacement by volume) virgin coarse aggregate with RCA has on the fresh and hardened properties of the resulting concrete. The strength-based mixtures were developed to investigate the influence of aggregate properties on reinforcement bond in concrete having the same compressive strength. In addition, two separate experimental phases were carried out which had varying compressive strength ranges, different RCA sources, and different suppliers of the same type GU cement. Concrete properties such as slump, compressive strength, splitting tensile strength, modulus of elasticity, Poisson’s ratio, linear coefficient of thermal expansion (LCTE), modulus of rupture and fracture energy were all measured. In total, 48 beam-end specimens were tested that incorporated three bonded lengths (125, 375, and 450 mm) and four concrete compressive strengths (30, 40, 50 and 60 MPa). Based on the results of the aggregate testing it was found that concrete incorporating pre-soaked (i.e., fully saturated) RCA as a 100% replacement for natural aggregate had slump values between 22% and 75%, compressive strengths between 81% and 137%, splitting tensile strengths between 78% and 109%, modulus of elasticity values between 81% and 98%, LCTE values in the same range, flexural strengths between 85% and 136%, and fracture energies between 68% and 118%, of the equivalent control (natural aggregate) concrete mixture. Overall, reductions in bond strength between natural aggregate and RCA concrete ranged between 3 and 21%. The strength of coarse aggregate as quantified by the aggregate crushing value (ACV) was found to be the most significant aggregate property for influencing bond strength. A regression model (based on the beam-end specimens test results) was developed to extrapolate the experimental development lengths as a function of f’c1/4 and ACV. The model, while not intended for use as a design equation, predicted that the required development lengths for the RCA concrete tested as part of this research study were up to 9% longer as compared to the natural aggregate concrete. A detailed flowchart of the various inter-relationships between aggregate properties, concrete properties and reinforced concrete bond properties was compiled based on the results of this research. A comprehensive guideline for use of RCA in concrete was developed based on the findings of this research. It includes a systematic decision tree approach for assessing whether a particular RCA source can be categorized into one of three performance classes. The range of allowable applications of a concrete which incorporates the RCA source as replacement of natural coarse aggregate will depend on the RCA performance class.