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Blasts and impacts are two of the severest loads a structure can experience. Blast experimenters, however, have observed that the load imparted to a circular member was lower than the predicted design load. Additionally, numerous investigations have established the superiority of concrete filled FRP tubes (CFFTs) over conventional reinforced concrete members. These observations indicated CFFTs’ potential to resist dynamic blast and impact loads. The experimental and numerical investigations presented in this thesis aimed to demonstrate the suitability of CFFTs to resist blast and impact loads, to determine the parameters that influence their behaviour under such loads, and to develop a design procedure for resisting these loads. The initial numerical investigation determined the reflected blast loading parameters experienced by a circular cross section. The experimental phase consisted of testing twelve full scale specimens, two monotonically, four under impact loading, and six under close-in blast loading. The monotonically tested specimens acted as controls for the entire program. The results of the impact testing investigation were used to develop and validate a non-linear single degree of freedom (SDOF) model. This impact phase also led to the development of relatively simple procedures for designing CFFTs under impact loading using either SDOF modeling or the conservation of energy. Analysis of the blast testing results led to the development of numerical procedures for obtaining an equivalent close-in blast loading for SDOF analysis of CFFTs and Pressure-Impulse diagrams. The use of SDOF modeling and conservation of energy in blast design were also discussed. Finally, a non-linear explicit dynamic model of CFFTs was developed using the commercial software ANSYS Autodyn. This model was verified using the experimental impact and blast test results and used to conduct a parametric study. The results of these investigations indicated that CFFTs were particularly suitable for blast and impact resistant applications, as their geometry diffracted blast waves and the addition of the tube increased their energy absorbing capacity significantly giving them additional strength and ductility. The tube also confined and protected the concrete core and simplified construction. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2014-01-27 15:57:52.768

This study presents experimental results from nine large-scale circular concrete columns reinforced with longitudinal and transverse glass fiber-reinforced polymer (GFRP) bars. These specimens were tested under lateral cyclic quasi-static loading while simultaneously subjected to constant axial load. Based on the measured hysteretic loops of moment vs. curvature and shear vs. tip deflection relationships, a series of parameters related to ductility and flexural strength are used to evaluate the seismic behavior of each column. The results showed that concrete columns reinforced with GFRP bars have stable post-peak branches and can achieve very high levels of deformability. Longitudinal GFRP bars maintained their stiffness at high strains and transverse GFRP spirals provided increasing confinement for the entire duration of the test without any spiral damage. The tests showed that, as an innovative material with excellent corrosion resistance GFRP bars can be successfully used as internal reinforcement in ductile concrete columns.

This study presents experimental results from nine large-scale circular concrete columns reinforced with longitudinal and transverse glass fiber-reinforced polymer (GFRP) bars. These specimens were tested under lateral cyclic quasi-static loading while simultaneously subjected to constant axial load. Based on the measured hysteretic loops of moment vs. curvature and shear vs. tip deflection relationships, a series of parameters related to ductility and flexural strength are used to evaluate the seismic behavior of each column. The results showed that concrete columns reinforced with GFRP bars have stable post-peak branches and can achieve very high levels of deformability. Longitudinal GFRP bars maintained their stiffness at high strains and transverse GFRP spirals provided increasing confinement for the entire duration of the test without any spiral damage. The tests showed that, as an innovative material with excellent corrosion resistance GFRP bars can be successfully used as internal reinforcement in ductile concrete columns.

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Concrete is an integral material in modern infrastructural requirements worldwide. The production of Portland cement is however expensive, energy intensive, and results in globally significant greenhouse gas emissions. Natural pozzolans such as pumice can be used as a partial replacement for Portland cement in concrete, which can reduce production costs and greenhouse gas emissions, and improve concrete performance. A fluvial pumice deposit which may be suited for use as a natural pozzolan has been identified on the floodplains of the Waikato River. A sample was milled in Germany, and returned to New Zealand in two subsamples. These were tested in concrete, with tests divided into four rounds. The first two rounds established baseline concrete strengths at water/binder (w/b) ratios of 0.6 and 0.5, with pumice replacing cement at 5, 10, 15 and 30%. Round Three assessed the use of high pH mix water (pH=12.9), and Round Four assessed the use of a polycarboxylate superplasticiser, both with 10% pumice. Pumice is known to retard early concrete strength, however through optimisation of mix design, improvements in concrete strength and durability can be made. Indeed, all 28 day concrete strengths in this research were below Ultracem, however half of these achieved or exceeded Ultracem strengths at 91 days. The use of superplasticiser achieved the best 28 day concrete strengths, and dosage optimisation is expected to yield further improvements. Concrete durability was tested at w/b=0.5, with 10% and 30% pumice. After prolonged curing (231 days), composite concrete showed substantial improvements in electrical resistivity and resistance to chloride attack, most notably with 30% pumice. Concrete porosity was essentially unaffected. This pumice has shown significant promise as a partial cement replacement. Further mix optimisation is likely to yield greater improvements in concrete strength and durability, and will provide a more economically and environmentally sustainable product for the New Zealand concrete market.

Following the evolution of a damage avoidance design (DAD) frame system, with rocking beam-column joints, at the University of Canterbury, analytical studies are carried out to evaluate the performance of proposed structures, and verify the proposed design methodology. A probabilistic seismic risk assessment methodology is proposed, from which the expected annualised financial loss (EAL) of a structure can be calculated. EAL provides a consistent basis for comparison of DAD frame systems with state-of-practice ductile monolithic construction. Such comparison illustrates the superior performance of DAD frame systems. The proposed probabilistic seismic assessment methodology requires the response of the structure to be evaluated over a range of seismic intensities. This can be achieved by carrying out an incremental dynamic analysis, explicitly considering seismic randomness and uncertainty; or from a pushover analysis, and assuming an appropriate value of the dispersion. By combining this information with the seismic hazard, probabilistic response curves can be derived, which when combined with information about damage states for the particular structure, can be transformed into 'resilience curves'. Integration of information regarding the financial loss occurring due to each of the damage states, results in an estimate of EAL.

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