The recent earthquakes in Christchurch have made it clear that issues exist with current RC frame design in New Zealand. In particular, beam elongation in RC frame buildings was widespread and resulted in numerous buildings being rendered irreparable. Design solutions to overcome this problem are clearly needed, and the slotted beam is one such solution. This system has a distinct advantage over other damage avoidance design systems in that it can be constructed using current industry techniques and conventional reinforcing steel. As the name suggests, the slotted beam incorporates a vertical slot along part of the beam depth at the beam-column interface. Geometric beam elongation is accommodated via opening and closing of these slots during seismically induced rotations, while the top concrete hinge is heavily reinforced to prevent material inelastic elongation. Past research on slotted beams has shown that the bond demand on the bottom longitudinal reinforcement is increased compared with equivalent monolithic systems. Satisfying this increased bond demand through conventional means may yield impractical and economically less viable column dimensions. The same research also indicated that the joint shear mechanism was different to that observed within monolithic joints and that additional horizontal reinforcement was required as a result. Through a combination of theoretical investigation, forensic analysis, and database study, this research addresses the above issues and develops design guidelines. The use of supplementary vertical joint stirrups was investigated as a means of improving bond performance without the need for non-standard reinforcing steel or other hardware. These design guidelines were then validated experimentally with the testing of two 80% scale beam-column sub-assemblies. The revised provisions for bond within the bottom longitudinal reinforcement were found to be adequate while the top longitudinal reinforcement remained nominally elastic throughout both tests. An alternate mechanism was found to govern joint shear behaviour, removing the need for additional horizontal joint reinforcement. Current NZS3101:2006 joint shear reinforcement provisions were found to be more than adequate given the typically larger column depths required rendering the strut mechanism more effective. The test results were then used to further refine design recommendations for practicing engineers. Finally, conclusions and future research requirements were outlined.

Abstract not available

Abstract not available

Large numbers of 1950's vintage conventionally reinforced concrete (CRC) bridges remain in-service in the national bridge inventory. Many of these bridges are lightly reinforced for shear. Evaluation of these bridges to prevent unnecessary and costly repairs requires refined analytical techniques. This dissertation presents finite element (FE) modeling and comparisons of various analytical methods for predicting capacity of CRC girders typical of reinforced concrete deck girder (RCDG) bridges. Analyses included bridge-system load distribution, member capacity prediction, and consideration of corrosion damage for strength deterioration. Two in-service RCDG bridges were inspected and instrumented to measure response under known load configurations. Load distribution was developed for the bridges based on the field data. Comparisons with AASHTO factors indicated the design factors for load distribution are conservative. Load distribution of the tested bridges was numerically obtained using FE analysis. The comparisons between predicted results and field-test data indicated the elastic FE analysis can be used for modeling of cracked RCDG bridges to predict load distribution factors for more accurate bridge evaluation. Analyses were performed for a large set of full-size RCDG, designed to reflect 1950's vintage details, and tested using various loading configurations. Four different analysis methods were used to predict the capacity of the specimens considering details of various stirrup spacing, debonded stirrups, flexural-bar cutoff, anchorage of flexural reinforcing, and moving supports. Nonlinear FE analyses were performed to predict behavior of two groups of experimental reinforced concrete (RC) specimens. Two different span-to-depth ratios were included: 2.0 and approximately 3.0. Concrete confinement effects were included in the material modeling. A quasi-displacement control technique was developed to reduce solution times. The FE predicted results correlated well with the experimental data. FE modeling techniques were developed to isolate different contributions of corrosion damage to structural response of experimental RC beams designed to produce diagonal-tension failures. Corrosion-damage parameters included concrete cover spalling; uniform stirrup cross-sectional loss; local stirrup cross-sectional loss due to pitting; and debonding of corrosion-damaged stirrups from the concrete. FE analyses were performed including both individual and combined damages. The FE results matched experimental results well and quantitatively estimated capacity reduction of the experimental specimens. / Graduation date: 2005 / Best scan available.

Arterial thrombus forms from the capture and accumulation of circulating platelets on a stenosis. As the thrombus grows, the lumen becomes further stenotic producing very high shear rates as the blood velocities increase through the narrowed cross-section. This study explores the molecular binding conditions that may occur under these pathologic shear conditions where circulating platelets must adhere quickly and with strong bonds. Platelets binding in an arterial stenosis of >75% are subject to drag forces exceeding 10,000 pN. This force can be balanced by 100 simultaneous GPIb-vWFA1 bonds of 100 pN each. The number and density of GPIb on platelets is sufficiently high; however, platelet capture under high shear would require the density of A1 receptors to be increased to over 416 per square micron. A computational model is used to determine platelet capture as a function of shear rate, surface receptor density, surface contact and kinetic binding rate. A1 density could be increased by a combination of vWF events of: i) plasma vWF attach to the thrombus surface and elongate under shear; ii) the elongated vWF strands create a net with 3-D pockets; and iii) additional vWF is released from mural platelets by activation under shear. With all three events, A1 density matches the existing high GPIbα densities to provide sufficient multivalency for capture at 100,000 s-1 with greater than 170 bonds per platelet. If the on-rate is greater than 108 M-1s-1, then a platelet could be captured within 15 microseconds, the amount of time available to form bonds before the platelet is swept away. This mechanism of platelet capture allows for the rapid platelet accumulation in atherothombosis seen clinically and in high shear experiments.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 168-170.

No description available.

No description available.

The effect of mechanical shear on brewing yeast was investigated with a focus on losses incurred through cell rupture and viability loss. The influence of various environmental conditions was studied with regards to the influence on Saccharomyces cerevisiae's ability to resist mechanical shear. Further investigation was performed in order to locate a structure within the yeast cell that contributes to mechanical shear resistance. / It was found that yeast cells grown anaerobically in limited glucose media were more prone to losses in cell viability than cells grown aerobically in the same media, when subjected to mechanical shear. Cells grown anaerobically in high glucose concentrations and allowed to ferment the media to exhaustion were slightly more resistant to mechanical shear compared to cells grown anaerobically without fermentation in minimal glucose media. Higher ethanol concentrations lead to marginally decreased resistance to mechanical shear. / Cell walls of S. cerevisiae were partially digested or extracted using enzymatic treatment or chemical attack. It was found that while the outer mannoprotein layer does not contribute significantly, the inner beta-(1 → 3)-glucan structure plays a significant role in resistance to mechanical shear.

The motivation behind this study is the lack of specialized analysis regarding internal failure caused by the adiabatic shear hand (ASB) phenomenon in the cold-headed products. Its aim was to present an integrated workability study to improve and assist cold-heading (CH) multistage design procedures to replace the current design rules of thumb, as they are neither effective nor adequate in fulfilling the needs of the new developments in the rapidly expanding CH industry. / To achieve these goals, a comprehensive testing methodology and FE modeling, implemented within ABAQUS/Explicit, were established. This methodology includes an instrumented Drop Weight Compression Test (DWCT) tower equipped with a guided pocket die-set configuration capable of developing internal failure at different stages of ASBs and integrated metallographic inspection techniques. A validated FE model of the DWCT and guided pocket die-set configuration was a valuable tool in establishing the failure criteria and indicating the workability limits. / A detailed experimental and FE study for the ASB stages in the CH process was introduced to uncover the affect of different parameters controlling the failure mechanisms within the ASBs in the CH process. This study investigated the effect of the thermal, geometric and the material flow softening and hardening mechanisms affecting ASB evolution. Moreover, a detailed metallurgical and FE study of the internal ductile and Transformed Adiabatic Shear Band (TASB) failures caused by the ASB phenomenon in DWCT was conducted. / Three ductile failure criteria were introduced to predict the initiation and location of the internal ductile failure in the ASBs. One TASB failure criteria was introduced to predict the phase transformation to undesirable brittle martensite. These failure criteria were employed to establish integrated workability methodologies to indicate the objective workability limits. / Applying these workability methodologies on multistage CH FE models showed that these methodologies are an efficient tool to predict the damage levels and failure initiation locations within the cold-headed bolts. Moreover, these methodologies were successful in optimizing the die designs in order to reduce damage levels.