This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.

No description available.

Corrosion of the reinforcing steel is a primary deterioration mechanism for reinforced concrete bridges. Heavy use of de-icing salts is believed to be a major contributor in Ontario to severe girder soffit spalling in certain cases. This thesis develops an assessment methodology to evaluate spalled bridges based on ultimate limit states. Specifically, a deterministic program is developed for assessment. It is subsequently compared to laboratory test results and used as a basis for a probabilistic reliability study. A modified area concept is proposed in this thesis to consider the effects of exposing reinforcement at various locations along the girder length. A multipoint analysis program, BEST (Bridge Evaluation Strength Tool), is developed that employs this concept, along with graphical spalling surveys and structural drawings, to evaluate reinforced concrete bridge girders. The program is adapted for a full bridge analysis and to consider the other effects of corrosion, such as bar section loss and bond deterioration. A case study bridge is evaluated to show that the BEST program offers a viable tool for the rapid assessment of spalled bridge girders and to facilitate the prioritization of rehabilitation projects. This evaluation indicates that the spatial distribution of the spalling along a girder, relative to bar splices and laps, has the most significant influence on structural capacity. Single girders show strength deficiencies in flexure and shear due to spalling. In general, the consideration of system effects improves the predicted bridge condition, while considering section loss and bond deterioration has the opposite effect. Laboratory work is used to validate the proposed model and identify a number of areas for future research. The laboratory test results also suggest that the current repair methods are effective in restoring bond and strength. In order to further explore potential uses for the BEST program, modifications are made so that it can be used to perform reliability analyses using Monte-Carlo simulation techniques. A simplified approach for estimating the reliability index as a function of the deterministic resistance ratio is proposed based on the reliability analysis results.

ix, 231, [123] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Depts. of Chemical Engineering and Physical and Inorganic Chemistry, 1993

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Muzzy, John D.; Committee Member: Cook, Fred L.; Committee Member: Jones, Christopher W.; Committee Member: Mayor, J. Rhett; Committee Member: Realff, Matthew J.; Committee Member: Schork, F. Joseph.

Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Tannenbaum, Rina; Committee Member: Garmestani, Hamid; Committee Member: Jacob, Karl; Committee Member: Patterson, Tim; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

Although gas turbine engines are designed to use dry air as the working fluid, the great demand over the last decades for air travel at several altitudes and speeds has increased aircraft’s exposure to inclement weather conditions. Although, they are required to perform safely under the effect of various meteorological phenomena, in which air entering the engine contains water, several incidents have been reported to the aviation authorities about power loss during flight at inclement weather. It was understood that the rain ingestion into a gas turbine engine influences the performance of the engine and particular the compressor and the combustor. The effects of water ingestion on gas turbine engines are aerodynamic, thermodynamic and mechanical. These effects occur simultaneously and affect each other. Considering the above effects and the fact that they are timedependent, there are few gas turbine performance simulation tools, which take into account the water ingestion phenomenon. This study is a new research of investigating theoretically the water ingestion effects on a gas turbine performance. It focuses on the aerodynamic and mechanical effects of the phenomenon on the compressor and the combustor. The application of Computational Fluid Dynamics (CFD) is the basic methodology to examine the details of the flow in an axial compressor and how it is affected by the presence of water. The calculations of water film thickness, which is formed on the rotor blade, its motion (direction and speed) and the extra torque demand, are provided by a code created by the author using FORTRAN programming language. Considering the change in blade’s profile and the wavy characteristics of the liquid film, the compressor’s performance deterioration is calculated. The compressor and combustor’s deterioration data are imported to a gas turbine simulation code, which is upgraded to calculate overall engine’s performance deterioration. The results show a considerable alteration in engine’s performance parameters and arrive at the same conclusions with the relevant experimental observations.

This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.

M.Tech. (Civil Engineering) / Every year, millions of Rands are being spent in rehabilitation, repairs and maintenance of reinforced concrete structures projects around the country due to corrosion. There are a number of studies and investigations that have been done recently to address the effect of corrosion on reinforced concrete structures. Concrete provides an ideal environment for steel, supplying both physical and chemical protection from corrosive attack. The effect of corrosion on reinforced concrete structures contributes to the reduction of steel cross sectional area, weakening the bond strength between steel and concrete and thereby reducing the ductility, deflection capacities and load carrying capacity of the structure. In this research, five series of three samples each of reinforced concrete beams were fabricated, some with reduced cross-sectional area and with exposed bars to simulate loss of bonding through spalling. The structural performance of these beams was tested in terms of maximum load carrying capacity, deflections and ductility ratio. The main conclusions are as follows:  As little as 1 % loss in mass of tension steel resulted in a load carrying capacity decrease of 6.9 %  Beam deflection increased by a factor of 1.5 times when the steel mass loss level was 14%  5 % steel loss in mass resulted in a 16.5 % decrease in relative ductility.