Punching Shear Behaviour of Thick Reinforced Concrete Slabs

Experiments were conducted to investigate the punching shear behaviour of thick slabs with identical spans and depths, subjected to monotonic point load conditions. Variables included: reinforcement ratio, column size, and reinforcement size. Analytical studies conducted as part of this thesis indicate that the current CSA A23.3 and the ACI 318 can be unconservative for thick slabs with low reinforcement ratios. The new fib Model Code provisions for punching offer an effective method for determining the full load-rotation behaviour of a slab up to failure, including accurate failure predictions. A summary of the background of current design procedures and standards will be presented, and a comparison between the different design equations and theories will be given. Based on the findings of this project, it is proposed that the provisions accepted by the fib Model Code should be considered for implementation in the CSA and ACI standards.MAS

Evolution of Structure in a Comb Copolymer-Surfactant Coacervate

The interaction between a double-hydrophilic comb copolymer with the polyanionic backbone poly[methacrylic acid-stat-poly(ethylene glycol) methyl ether methacrylate] (PMAA-PEGMA) and the cationic surfactant N-dodecylpyridinium chloride (DPCl) was studied in alkaline aqueous solutions by using a combination of light and X-ray scattering techniques, covering 5 orders of magnitude in space (the q vector range from 10-5 to 5 nm-1) and time (from milliseconds to several hours). The results showed that the polyelectrolyte-surfactant (PE-S) complex of PMAA-PEGMA and DPCl forms micrometer-sized coacervate particles containing collapsed PMAA-PEGMA chains with attached and densely packed DPCl micelles. Time-resolved SAXS measurements coupled with a stopped-flow apparatus revealed that the phase separation of the PE-S complex into a coacervate phase occurred in <25 ms after mixing the polyelectrolyte and the surfactant. Thus, microphase separation was faster than the self-assembly of DPCl into densely packed micelles. The terminal stages of polyelectrolyte-surfactant coacervation were dictated by the Ostwald ripening of the droplets in the time range of hours