Synthetic fiber reinforced concrete sample sets were exposed to two different environments. One set, of six samples, was exposed to filtered seawater in the lab with wet and dry cycles, while the other set of samples was exposed, on a barge, to the marine environment, in the intracoastal waterways, at SeaTech. The samples were exposed for 8 months, and then removed for experimental and mechanical testing. Upon removal, the barge samples were photographed to observe surface organisms that were attached to each sample. The barge samples, after cleaning, were then exposed to UV light to observe surface bacteria. The barge samples were also taken to Harbor Branch facility for DNA testing, and then sent in for sequencing. This sequencing was used to identify the organisms that were present inside the concrete samples. An Indirect Tensile Strength Test, IDT, was performed on both sets of samples to observe the first crack, max load, and fracture toughness of each sample. The Barge samples had a lower first crack, max load, and fracture toughness, which means that it took less force to break these samples, than the Seawater samples. As the fiber content increased, the Seawater samples grew stronger, while the Barge samples grew weaker. Also, as the fiber content increased, the biodiversity found on the surface of the Barge samples increased as well. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

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In the Australian Standard, AS 3600-2001, the neutral axis parameter Ku is used as a convenient, but approximate, parameter to design for moment redistribution in building frames. The research work reported herein was conducted to obtain complete information regarding moment redistribution of beams and one-way slabs using 500 MPa steel reinforcement.A computer based iterative numerical method was developed to analyse reinforced two-span continuous concrete beams and one-way slabs. The method takes into account the material and geometrical non-linearities in the calculations. The deflected shape of the beam and one-way slab was calculated by dividing the span length into a number of rigid segments. The program also calculates the failure load and extent of moment redistribution. The analytical method was verified against the test results reported in the literature. The analytical results for load-deflection graphs and moment redistribution showed a good agreement with the test results.A parametric study was conducted using analytical method. The results of this study showed that moment redistribution depends not only on the neutral axis parameter (Ku) but also on the ratio of neutral axis parameter (Ku-/Ku+), ultimate steel strain (ªsu) and concrete compressive strength (fc).

A numerical model for the cathodic protection of steel in reinforced concrete is developed. Parameters are set to represent a three-dimensional section of a bridge beam exposed to the atmosphere and coated with a thermally sprayed zinc anode. Both diffusion of oxygen and conduction of charge within the concrete are considered explicitly through a two-dimensional finite element model. The diffusivity and conductivity are represented as functions of concrete moisture content. Electrochemical reactions considered at the rebar-concrete interface are reduction of oxygen, oxidation of iron, and evolution of hydrogen in a constant-potential cathodic protection circuit. Reaction-kinetic parameters for actively corroding steel (not passivated steel) are used. Reactions at the zinc-concrete interface are not considered explicitly. The effectiveness of protection is found to vary significantly with both concrete moisture content and position on the rebar. For spatially uniform pore saturation, the drier the concrete is, the greater the corrosion current and the greater the non-uniformity. Protection is significantly more effective at the "front" of the rebar (closest to the zinc anode) than at the "back" (closest to the center of the beam). Corrosion current is greater under drying conditions than under wetting conditions. The numerical model is applied towards interpretation of the "100-mV polarization decay criterion" that is often used to assess the effectiveness of cathodic protection. It is found that the polarization decay predicted from relaxation of oxygen concentration gradients was comparable in magnitude to that observed experimentally, but depends on location on the rebar. A numerical model for the transport of ions in porous concrete under cathodic protection is presented. In this initial model, transport of the ions zinc, calcium, chloride and hydroxide is described by a one-dimensional Nernst-Planck equation at constant current density with generation of zinc ions at the anodic interface, generation of hydroxide ions at the cathodic interface, and no chemical reactions in the bulk of the concrete. The equations are solved numerically by two methods: the point method, in which concentrations and electric potentials are solved for directly through finite-difference approximations of the differential equations and the box method, in which the domain is divided into discrete volume elements with flux balances for each chemical component and for charge. A base grid of 41 nodes is used. Results for the system after 96 and 9600 days of cathodic protection are discussed. Both numerical methods yielded concentration profiles that are virtually indistinguishable. Numerical noise in the box method leads to values in the first and second derivatives of the electric potential that tend to oscillate around the central values represented by the same smooth curve of the point method. In contrast, the point method shows greater apparent numerical deviation from electroneutrality which is largest near the boundaries and decays towards the center in damped oscillations. The deviations decrease with smaller size of grid elements and higher order difference approximations. The magnitude of the charge density in the bulk of the concrete calculated from the second derivative of the electric potential through Poisson's equation is shown to be negligible compared to the overall electroneutrality calculated from the concentrations of ions. At 96 days, the relative contributions of migration and diffusion to the overall flux are shown to vary widely with position and species; migration can neither be neglected nor can a "corrected" Fick's law approach be used. Zinc ions are found to have moved approximately 15 mm into the bulk of the concrete at 96 days. / Graduation date: 2006

This thesis discusses the results of an experimental program designed to investigate the effect of corrosion on the behaviour of shear critical reinforced concrete (RC) beams. The results of twenty RC beams (ten deep beams and ten slender beams) are described and discussed. The test variables included: corrosion level (2.5%, 5% and 7.5%) and existence of stirrups (beams without stirrups and beams with stirrups). The feasibility of repairing the corroded shear critical RC beams with CFRP laminates was also investigated. Sixteen specimens were corroded using an accelerated corrosion technique whereas four specimens acted as control un-corroded. Following the corrosion phase, all specimens were tested to failure under three point bending. Test results revealed that the corrosion does not adversely affect the behaviour of shear critical RC beams rather it improves their behaviour. It was found that corrosion changed the failure mode of the corroded beams. The control un-corroded deep beams (beams with and without stirrups) failed in shear-compression failure whereas corroded deep beams (beams with and without stirrups) failed by splitting of the compression strut. The control un-corroded slender beams (beams with and without stirrups) failed in diagonal tension failure whereas the corroded slender beams failed in anchorage failure (beams without stirrups) and flexural failure (beams with stirrups). The analysis of the results showed that corrosion changed the load transfer mechanism and the change of failure mode was associated with the mechanism. The load transfer mechanism changed from a combination of beam and arch action in the control un-corroded deep beams to pure arch action in the corroded deep beams. The load transfer mechanism changed from pure beam action in the control un-corroded slender beams to pure arch action in the corroded slender beams. Two strut and tie models are proposed: one for corroded deep beams and one for corroded slender beams. The ultimate loads of the corroded beams were predicted using these struts and tie models and compared with the experimental results. A very good correlation was found between predicted and experimental results.

The effect of corrosion on a single-bent, reinforced concrete (RC) bridge subject to seismic loading is the primary focus of this research. This work attempts to determine the effects of decreasing rebar diameter and concrete cover spalling on the strength and stiffness of the RC bridge. The application of these results to the field of historic preservation will also be explored. Through the use of static and dynamic analyses, this research shows that the effects of corrosion only have a slight influence on the seismic fragility of the RC bridge. The loss of three inches of concrete cover from the bridge column is shown to have a greater effect on the strength and stiffness of the bridge than decreasing the rebar diameter by 10%. The deformation capacity and demand both increase for bridges with reduced reinforcing steel and concrete cover; however, the capacity increases to a greater degree than the demand. The seismic fragility of the bridge based on deformation criteria is greatest for the pristine structure, and it decreases as the level of damage increases. Future work should include verifying the hysteretic behavior by accounting for reinforcement slip caused by a loss of bond.

The design of reinforced concrete structures for extreme events requires accurate predictions of the ultimate rotational capacity of critical sections, which is dictated by the failure mechanisms of shear, hoop fracture, low-cycle fatigue and longitudinal bar buckling. The purpose of this research is to develop a model for the full compressive behavior of longitudinal steel including the effects of bar buckling. A computational algorithm is developed whereby experimental data can be rigorously modeled. An analytical model is developed from rational mechanics for modeling the complete compressive stress-strain behavior of steel including local buckling effects. The global buckling phenomenon is then investigated in which trends are established using a rigorous computational analysis, and a limit analysis is used to derive simplified design and analysis equations. The derived buckling models are incorporated into wellestablished sectional analysis routines to predict full member behavior, and the application of these routines is demonstrated via an incremental dynamic analysis of a ten-storey reinforced concrete building. The buckling models and the sectional analysis routine compare favorably with experimental data. Design recommendations and topics for further research are presented.

The shear capacity of reinforced concrete pier caps in existing bridge support systems can be a factor which limits the capacity of an existing bridge. In their usual configuration, pier caps behave as deep beams and have the ability to carry load through tied arch action after the formation of diagonal cracks. Externally bonded fiber reinforced polymer (FRP) reinforcement has been shown to increase the shear capacity of reinforced concrete members which carry load through beam action. However, there is an insufficient amount of research to make it a viable strengthening system for beams which carry load through arch action, such as pier caps. Accordingly, this research was aimed at investigating the behavior of reinforced concrete pier caps through a coordinated experimental and analytical program and to recommend an external strengthening method for pier caps with perceived deficiencies in shear strength. The experimental study was performed on laboratory specimens based on an existing bridge in Georgia. A number of factors were examined, including size, percentage longitudinal reinforcement and crack control reinforcement. The results showed that increasing the longitudinal tension reinforcement increased the beam capacity by changing the shape of the tied arch. In contrast, the presence of crack control reinforcement did not change the point at which diagonal cracking occurred, but it did increase the ultimate capacity by reinforcing the concrete against splitting. The results of the experimental study were used in conjunction with a larger database to examine different analytical methods for estimating the ultimate capacity of deep beams, and a new method was developed for the design of external strengthening. Two specimens were tested with externally bonded FRP reinforcement applied longitudinally to increase the strength of the tension tie. The test results correlated well with the proposed method of analysis and showed that increasing the strength of the longitudinal tension tie is an effective way to increase the strength of a reinforced concrete deep beam.