This research project on the campus of Southern Illinois University Carbondale is an extension to the inquiry into the feasibility and reliability of the technology known as Digital Laser Speckle Image Correlation (DiLSIC). This is a hybrid approach of combining two existing technologies. The first being Digital Image Correlation (DIC) which is a nondestructive evaluation commonly used to find displacement, in-plane strain, as well as deformation. The second being the of laser speckle patterns. This hybrid has achieved level of resolution measured to be 3.4μ. DiLSIC increases the application ability of the DIC technique to situations that generally would not be an option to use. DiLSIC needs no artifact speckle patterns to be applied to the specimen as a preparation for nondestructive testing. In DIC testing, the surface of a specimen must artifact speckles applied to the subject surface. Often the application of artifact speckles is not desirable or possible. DiLSIC is an acceptable alternative to the previously discussed industry-wide practice. This method broadens the usage of the DIC technique to situations which previously were not possible. This technology can identify, quantify, and detect the distribution of strain and stress concentrations in composite structures. For this study, a honeycomb-backed glass fiber reinforced polymer (GFRP) panel from a Cessna aircraft exterior luggage door was obtained and a defect panel is created. The panel is constructed with one area containing a repair compliant with manufacturer standardized methods and a repair area is not compliant and consists of multiple incorrect repair steps. An area with no repair is also tested to act as a control for comparison and quantification. The results for the inspected areas showed a linear strain increase in the noncompliant repair. The data plot for the compliant repair showed a trend of following the same basic curve as the no repair area. A verification process follows the DiLSIC testing consisting of using Infrared Thermography, Air-coupled ultrasonic, and white light artifact speckle DIC. These tests show DiLSIC is a viable alternative to the testing that is available in the industry. DiLSIC can detect defect location, size, geometry and map strain to determine the difference between compliant and noncompliant repairs when compared to a base level non-repair area

Recent studies showed the need for timber connections with high fire performance. Connections of members in timber structures commonly comprise steel connectors, such as dowels, screws, nails and toothed plates. However, multiple studies have shown that the presence of exposed metal in timber connections leads to a poor performance under fire conditions. Replacing metallic fasteners with non-metallic fasteners potentially enhances the fire performance of timber connections. Previous studies showed that Glass Fibre Reinforced Polymer (GFRP) dowels can be a viable replacement for steel dowels and that Densified Veneer Wood functions well as a flitch plate material. However, as the resin matrix of GFRP dowels is viscoelastic, connection creep, which is not studied before, can be of concern. Also no research has been carried out on the fire performance of these connections. Therefore, a study of the creep behaviour and the fire performance of non-metallic timber connections comprising GFRP dowels and a Densified Veneer Wood flitch plate was performed, as is discussed in this thesis. Predictive models were proposed to determine the connection slip and load bearing capacity at ambient and elevated temperatures and in a fire. The material properties and heat transfer properties required for these models were determined experimentally and predictions of these models were experimentally validated. Furthermore, an adjustment of the predictive model of connection slip at ambient temperature allowed approximating the creep of the connection. The material properties, required for the creep model, were determined experimentally and predictions of the model were compared to results of longterm connection tests. The study confirmed that timber members jointed with non-metallic connectors have a significantly improved fire performance to timber joints using metallic connections. Models developed and proposed to predict fire performance gave accurate predictions of time to failure. It was concluded that non-metallic connections showed more creep per load per connector, than metallic connections. However, the ratio between initial deflection and creep (relative creep) and the ratio between load level and creep were shown to be similar for metallic and non-metallic connections.

Civil engineers are presently faced with the challenge of strengthening and repairing many existing structures to assure or increase their structural safety. The reasons for this include changes in the use of structures, and increased traffic loads on bridges. In Iraq, for example, several highway bridges needed to accommodate increased axle load during the transportation of huge turbines for electricity generating stations. The requirement for structural strengthening and repair methods is, however, driven by the worldwide need to ensure the safety and sustainability of our aging infrastructure which is deteriorating at a rate faster than it can be renovated. The ever increasing damage caused by environmental effects and the corrosion of steel and deterioration of concrete, reduce structural safety and lead to disruption for the users, which can have serious economic consequences. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. The two primary functions of the web plate in a plate girder are to maintain a relative distance between the top and bottom flanges and to resist the induced shear stresses. In most practical ranges of plate girder bridges’ spans, the induced shear stresses are relatively low compared to the bending stresses in the flanges induced by flexure. As a result the web plate is generally chosen to be much thinner than the flanges. The web panel consequently buckles at a relatively low shear force. For steel girder structures dominated by cyclic loading, as is the case with repeated vehicle axle loads on bridges, this can lead to the so-called ‘breathing’ phenomenon; an out-of-plane buckling displacement that can induce high secondary bending stresses at the welded plate boundaries. In the current work, a novel FRP strengthening technique using bonded shapes is applied to resist these out of plane deformations, and hence reduce the breathing stresses, and improve the fatigue life of the plate girder which is very different to the majority of applications of FRP strengthening that exploit the FRP for its direct tensile strength and stiffness. The objective of the current experimental programme is to strengthen thinwalled steel girders against web shear buckling using a corrugated CFRP or GFRP panel bonded externally along the compression diagonal of the web plate. The programme was divided into three main phases, including: (1) the development of a new preformed corrugated FRP panel, and (2, 3) testing its performance in two main experimental series. The initial series involved tests on 13 steel plates strengthened with the proposed preformed corrugated FRP panel and subjected to in-plane shear loading using a specially manufactured “picture-frame” arrangement designed to induce the appropriate boundary conditions and stresses in the web plates. This initial test series investigated the performance of different forms of strengthening under static load, in preparation for another series of cyclic tests to investigate their fatigue performance. The test variables included FRP type (CFRP or GFRP), form of FRP (closed or open section), number of FRP layers, and orientation of GFRP fibres used to produce the FRP panel. In the second series, six specimens were manufactured to simulate the end panel of a plate girder. These were strengthened with the optimized FRP panel from the initial series and tested for shear buckling under repeated cyclic loading with a stress range 40-80% of the static ultimate capacity. A considerable increase in the stiffness of the strengthened specimens is evident in the observed reductions of the maximum out-of-plane displacement. The stiffness of the strengthened specimens is assessed to be increased by a factor ranging between 3 to 9 times the stiffness of the corresponding unstrengthened specimen, depending upon the type of the FRP panel used and the aspect ratio of the tested specimens. The breathing phenomena is also significantly reduced, consequently the surface, membrane and secondary bending stresses are reduced. The 45° strengthening scheme succeeded the best both in reducing the breathing stresses and increasing the ultimate shear capacity of the specimen by 88%. Fatigue analyses indicated that the proposed strengthening technique is able to considerably elongate the life expectancy of the strengthened plate girders by a factor ranging between 2.5 and 7 depending on the applied cyclic load amplitude. In addition, the proposed strengthening technique did not show any debonding or delamination under both static and cyclic loading which makes it a good candidate for strengthening thin-walled structural members, especially, when ductility is a concern. In fact, the proposed strengthening technique succeeded in improving the energy absorption capacity of the strengthened specimens by a factor ranging between 1.5 and 2.5 times the corresponding control specimen which means that the ductile failure type associated with shear buckling of steel plate girders is not only maintained, but it was improved as well. This type of ductile failure is not common in other types of FRP strengthening techniques. Finally, a geometrical and material non-linear finite element model is presented both for the steel and composite sections which showed very good correlation with test results and was capable of predicting both the strength and deformational behaviour of the tested specimens. This numerical model is used for a parametric study to support the proposed design method.

There are approximately 6000 Gulfport-type wood structures used to support 1600 km of 230 kV electrical transmission lines in Ontario. An unexpected structural failure caused by wood deterioration has been recognized as a major risk to the safety of these transmission lines. Since the reliability of the electricity transmission and distribution lines is extremely important to the electrical industry and other users of electricity, failure of these structures can result in devastating incidents. Due to the remote location of the transmission network and the requirement to keep the power lines in continuous service, replacement of the Gulfport structures has proved to be very difficult and expensive. This research program investigated the use of Glass Fibre Reinforced Polymer (GFRP) wrap as a light weight and durable strengthening system that can be applied to the existing structures without any interruptions in the functionality of the transmission lines. A total of three control specimens and three strengthened samples were tested in Phase I of the experimental program, which was designed as a feasibility study. It was concluded that the average strength of strengthened samples was 42% higher than the average strength of the control samples, and was greater than the end of life (EOL) threshold of 30 MPa for the cross arms. Therefore, the proposed strengthening system was concluded to be an effective solution for strengthening the deteriorated cross arms of the Gulfport structures. Taguchi methods and Analysis of Variation (ANOVA) were employed in Phase II to optimize the proposed strengthening system. The optimal configuration was determined to be the application of the filler material, non-sanded surface, and the shorter width of wrap (width of 0.6 m). The mean strength of the optimal configuration was estimated to be 52 MPa with a 95% confidence interval of: 38.7 MPa < True Mean < 65.3 MPa. Phase III confirmed the estimated mean and the confidence interval for the optimal configuration in Phase II. The strengthening system changed the failure mode from combined shear-flexure failure to pure flexure and resulted in more consistent strength and stiffness values. The strain values of the GFRP wrap showed that a single layer of wrap was sufficient for the confinement purposes.

There are approximately 6000 Gulfport-type wood structures used to support 1600 km of 230 kV electrical transmission lines in Ontario. An unexpected structural failure caused by wood deterioration has been recognized as a major risk to the safety of these transmission lines. Since the reliability of the electricity transmission and distribution lines is extremely important to the electrical industry and other users of electricity, failure of these structures can result in devastating incidents. Due to the remote location of the transmission network and the requirement to keep the power lines in continuous service, replacement of the Gulfport structures has proved to be very difficult and expensive. This research program investigated the use of Glass Fibre Reinforced Polymer (GFRP) wrap as a light weight and durable strengthening system that can be applied to the existing structures without any interruptions in the functionality of the transmission lines. A total of three control specimens and three strengthened samples were tested in Phase I of the experimental program, which was designed as a feasibility study. It was concluded that the average strength of strengthened samples was 42% higher than the average strength of the control samples, and was greater than the end of life (EOL) threshold of 30 MPa for the cross arms. Therefore, the proposed strengthening system was concluded to be an effective solution for strengthening the deteriorated cross arms of the Gulfport structures. Taguchi methods and Analysis of Variation (ANOVA) were employed in Phase II to optimize the proposed strengthening system. The optimal configuration was determined to be the application of the filler material, non-sanded surface, and the shorter width of wrap (width of 0.6 m). The mean strength of the optimal configuration was estimated to be 52 MPa with a 95% confidence interval of: 38.7 MPa < True Mean < 65.3 MPa. Phase III confirmed the estimated mean and the confidence interval for the optimal configuration in Phase II. The strengthening system changed the failure mode from combined shear-flexure failure to pure flexure and resulted in more consistent strength and stiffness values. The strain values of the GFRP wrap showed that a single layer of wrap was sufficient for the confinement purposes.

Although Glass Fiber Reinforced Polymer (GFRP) has many potential advantages as reinforcement in concrete structures, the loss in tensile strength of the GFRP reinforcing bar can be significant when exposed to the high alkali environments. Much effort was made to estimate the durability performance of GFRP in concrete; however, it is widely believed the data from accelerated aging tests is not appropriate to predict the longer-term performance of GFRP reinforcing bars. The lack of validated long-term data is the major obstacle for broad application of GFRP reinforcement in civil engineering practices. The main purpose of this study is to evaluate the longer-term deterioration rate of GFRP bars embedded in concrete, and to develop an accurate model that can provide better information to predict the longer-term performance of GFRP bars. In previous studies performed by Trejo, three GFRP bar types (V1, V2, and P type) with two different diameters (16 and 19 mm [0.625, and 0.7 in. referred as #5 and #6, respectively]) provided by different manufacturers were embedded in concrete beams. After pre-cracking by bending tests, specimens were stored outdoors at the Riverside Campus of Texas A&M University in College Station, Texas. After 7 years of outdoor exposure, the GFRP bars were extracted from the concrete beams and tension tests were performed to estimate the residual tensile strength. Several physical tests were also performed to assess the potential changes in the material. It was found that the tensile capacity of the GFRP bars embedded in concrete decreased; however, no significant changes in modulus of elasticity (MOE) were observed. Using this data and limited data from the literature, a probabilistic capacity model was developed using Bayesian updating. The developed probabilistic capacity model appropriately accounts for statistical uncertainties, considering the influence of the missing variables and remaining error due to the inexact model form. In this study, the reduction in tensile strength of GFRP reinforcement embedded in concrete is a function of the diffusion rate of the resin matrix, bar diameter, and time. The probabilistic model predicts that smaller GFRP bars exhibit faster degradation in the tensile capacity than the larger GFRP bars. For the GFRP bars, the model indicates that the probability that the environmental reduction factor required by The American Concrete Institute (ACI) and the American Association of State Highway Transportation Officials (AASHTO) for the design of concrete structures containing GFRP reinforcement is below the required value is 0.4, 0.25, and 0.2 after 100 years for #3, #5, and #6, respectively. The ACI 440 and AASHTO design strength for smaller bars is likely not safe.

Flat slab-column connections are common elements in reinforced concrete (RC) structures such as parking garages. In cold weather regions, these structures are exposed to de-icing salts and aggressive environments. Using fiber reinforced polymer (FRP) bars instead of steel in such structures will overcome the corrosion problems associated with steel reinforcement. However, the available literature shows few studies to evaluate the behaviour of FRP-RC interior slab-column connections tested mainly under concentric loads, which seldom occurs in a real building. The main objectives of this research are to deal with this gap by investigating the behaviour of full-scale glass (G) FRP-RC interior slab-column connections subjected to eccentric load and to provide design recommendations for such type of connections. This study consisted of two phases, experimental and analytical. The experimental phase included the construction and testing of ten full-scale interior slab-column connections. The parameters investigated in the experimental phase were flexural reinforcement ratio, concrete compressive strength, type of the reinforcement, moment-to-shear ratio and the spacing between the shear stud reinforcement. Test results revealed that increasing the GFRP reinforcement ratio or the concrete strength increased the connection capacity. Moreover, compared to the control steel-RC specimen, the GFRP-RC connection with similar reinforcement rigidity showed comparable capacity and deflection at failure. Also, increasing the moment-to-shear ratio resulted in a reduction in the vertical load capacity, while using the shear stud reinforcement enhanced the strength up to 23%. In the analytical phase, a 3-D finite element model (FEM) was constructed using specialized software. The constructed FEM was able to predict the experimental results within a reasonable accuracy. The verified FEM was then used to conduct a parametric study to evaluate the effects of perimeter-to-depth ratio, column aspect ratio, slab thickness and a wide range of flexural reinforcement ratio. The numerical results showed that increasing the reinforcement ratio increased the connection capacity. In addition, increasing the perimeter-to-depth ratio and slab thickness reduced the punching shear stresses at failure, while, the effect of the column rectangularity diminished for a ratio greater than three. Moreover, the results showed prominent agreement with the experimental results from literature. / October 2015

The non-corrodible nature of FRP bars along with their high strength, light weight and ease of installation made it attractive as reinforcement especially for structures exposed to aggressive environment. In addition, the transparency of FRP bars to magnetic and electrical fields makes them an ideal alternative to traditional steel reinforcement in applications sensitive to electromagnetic fields such as magnetic resonance imaging (MRI) units. Continuous concrete beams are commonly-used elements in structures such as parking garages and overpasses, which might be exposed to extreme weather conditions and the application of de-icing salts. In such structures, using the non-corrodible FRP bars is a viable alternative to avoid steel-corrosion problems. However, the linear-elastic behaviour of FRP materials makes the ability of continuous beams to redistribute loads and moments questionable. The objective of this research project is to investigate the flexural behaviour of continuous concrete beams reinforced with FRP and their capability of moment redistribution. An experimental program was conducted at the University of Manitoba to realize the research objectives. Ten full-scale continuous concrete beams were constructed and tested to failure in the laboratory. The specimens had a rectangular cross-section of 200×300 mm and continuous over two spans of 2,800 mm each. The main investigated parameters were the amount and material of longitudinal reinforcement, the amount and material of transverse reinforcement and the spacing of used stirrups. The experimental results showed that moment redistribution in FRP-reinforced continuous concrete beams is possible if the reinforcement configuration is chosen properly, and is improved by increasing the amount of transverse reinforcement. A finite element investigation was conducted using ANSYS-software. A 3-D model was created to simulate the behaviour of continuous beams reinforced with FRP. The model was verified against the experimental results obtained from the present study. This verified model was used to investigate the effect of the concrete compressive strength, longitudinal reinforcement ratio, midspan-to-middle support reinforcement ratio and the amount of transverse reinforcement on the behaviour of FRP-reinforced beams. The analytical results of this parametric investigation along with the experimental results were used to propose an allowable limit for moment redistribution in FRP-reinforced continuous concrete beams.

The use of fibre reinforced polymer (FRP) composites as an alternate to steel has proved to be an effective solution to the corrosion problem. However, FRP bars have low axial and transverse stiffness compared to steel bars which results in a lower shear capacity of FRP reinforced concrete (RC) elements compared to steel-RC elements. Flat plate systems are commonly used to take advantages of the absence of beams. They, however, are susceptible to punching shear failure where the column suddenly punches through the slab. An experimental program was conducted to investigate the punching shear behaviour of slab-column edge connections. Nine isolated full-scale slab-column edge connections were constructed and tested to failure. One connection was reinforced with steel flexural reinforcement, six with GFRP flexural reinforcement and two with GFRP flexural and shear reinforcement. The parameters investigated were the flexural reinforcement type and ratio, the moment-to-shear ratio and the shear reinforcement spacing.

The non-corrodible nature of FRP bars along with their high strength, light weight and ease of installation made it attractive as reinforcement especially for structures exposed to aggressive environment. In addition, the transparency of FRP bars to magnetic and electrical fields makes them an ideal alternative to traditional steel reinforcement in applications sensitive to electromagnetic fields such as magnetic resonance imaging (MRI) units. Continuous concrete beams are commonly-used elements in structures such as parking garages and overpasses, which might be exposed to extreme weather conditions and the application of de-icing salts. In such structures, using the non-corrodible FRP bars is a viable alternative to avoid steel-corrosion problems. However, the linear-elastic behaviour of FRP materials makes the ability of continuous beams to redistribute loads and moments questionable. The objective of this research project is to investigate the flexural behaviour of continuous concrete beams reinforced with FRP and their capability of moment redistribution. An experimental program was conducted at the University of Manitoba to realize the research objectives. Ten full-scale continuous concrete beams were constructed and tested to failure in the laboratory. The specimens had a rectangular cross-section of 200×300 mm and continuous over two spans of 2,800 mm each. The main investigated parameters were the amount and material of longitudinal reinforcement, the amount and material of transverse reinforcement and the spacing of used stirrups. The experimental results showed that moment redistribution in FRP-reinforced continuous concrete beams is possible if the reinforcement configuration is chosen properly, and is improved by increasing the amount of transverse reinforcement. A finite element investigation was conducted using ANSYS-software. A 3-D model was created to simulate the behaviour of continuous beams reinforced with FRP. The model was verified against the experimental results obtained from the present study. This verified model was used to investigate the effect of the concrete compressive strength, longitudinal reinforcement ratio, midspan-to-middle support reinforcement ratio and the amount of transverse reinforcement on the behaviour of FRP-reinforced beams. The analytical results of this parametric investigation along with the experimental results were used to propose an allowable limit for moment redistribution in FRP-reinforced continuous concrete beams.