This thesis has investigated the application of CFRP and GFRP bars as longitudinal reinforcement for continuously supported concrete beams. Two series of simply and continuously supported CFRP and GFRP reinforced concrete beams were tested in flexure. In addition, a continuously supported steel reinforced concrete beam was tested for comparison purposes. The FRP reinforced concrete continuous beams were reinforced in a way to accomplish three possible reinforcement combinations at the top and bottom layers of such continuous beams. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported FRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. However, continuous concrete beams reinforced with CFRP bars exhibited a remarkable wide crack over the middle support that significantly influenced their behaviour. The ACI 440.1R-06 equations have been validated against experimental results of beams tested. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested. However, The potential capabilities of these equations for predicting the load capacity and deflection of continuous CFRP reinforced concrete beams have, however, been adversely affected by the de-bonding of top CFRP bars from concrete. An analytical technique, which presents an iterative procedure based on satisfying force equilibrium and deformation compatibility conditions, has been introduced in this research. This technique developed a computer program to investigate flexural behaviour in particular the flexural strength and deflection of simple and continuously supported FRP reinforced concrete beams. The analytical modelling program has been compared against different prediction methods, namely ACI 440, the bilinear method, mean moment inertia method and Benmokrane¿s method. This comparison revealed the reliability of this programme in producing more enhanced results in predicting the behaviour of the FRP reinforced beams more than the above stated methods.

A concrete beam is rarely subjected to pure torsion loading. However, in many design applications a beam is subjected to torsional loads in addition to bending and shear loading. The American Concrete Institute has developed a specification for the design of beams subjected to torsion. These specifications are found in ACI 318-83. In this research report, a computer program is presented, using these specifications, which will aid engineers in the design of reinforcement for concrete beams subjected to torsional loading. The provisions of the ACI 318-83 specification and their implementation into the computer program are presented. A sample problem is solved to compare the results of normal hand calculations to the results of the computer program. A listing of the computer program, written in Microsoft's GW BASIC, is provided. The designer enters information pertaining to the beams cross sectional properties, material properties and loading conditions. The program computes the concrete and reinforcement strength requirements and determines the amount of reinforcement required. The stirrup spacing and longitudinal reinforcement required are then determined and output to the designer.

The level of safety associated with the ACI Standard 318-83 design criteria for torsional reinforced concrete members is evaluated. Advanced first-order, second-moment reliability analysis is used to compute the reliability index. Reinforced concrete beams, subjected to both equilibrium and compatibility torsion, are analyzed. The uncertainties associated with the various torsion design parameters are included in the reliability-based formulation. For beams designed to carry equilibrium torsion, reliability indices ranging from 3.10 to 3.65 are obtained. The reliability indices for the compatibility torsion designs, analyzed in this study, vary from 1.88 to 2.09. For a given beam section, the reliability index is found to decrease with an increase in beam reinforcement. When the live load is reduced for members having a load influence area greater than 400 ft 2, the reliability index is found to increase with increase in basic live load to nominal dead load ratio. / M.S.

M.S.

This research investigates the flexural behavior of reinforced concrete (RC) beams retrofitted with fiber metal laminate (FML), an advanced hybrid material composed of alternating layers of metal and fiber-reinforced polymer (FRP) composites bonded through a thermoplastic or thermoset polymeric matrix. While FRP composites are commonly used for structural retrofits, their brittle failure mode, due to the linear elastic behavior of the fibers that cannot deform plastically, limits their effectiveness in applications requiring ductility. To address the drawbacks associated with FRP, this project proposes FML as a potential alternative. Flexural testing was conducted on seven RC beams with different configurations of FML and FRP under four-point bending. The goal of the project was finding an ideal retrofit for the RC beam that increased the peak load without a sacrificing the ductility. The beams, which were simply supported, were subjected to two point loads in order to assess their complete load-deformation behavior. Displacements and applied loads were measured at the midspan, and strain data wasrecorded along the length of the retrofits. Four beams were retrofitted with FML, two with FRP, and one served as a control specimen that did not have a retrofit. In order to prevent a premature debonding failure between the RC beam and retrofit, this study also explored different bonding methods: hybrid bonding and unbonded anchorage configurations. Four of the retrofitted beams had a hybrid bonded anchorage configuration and two had an unbonded anchorage configuration. Analytical modeling was performed to predict the behavior of RC beams with various retrofit configurations and bonding types. The modeling procedure for fully bonded retrofits followed the prescribed method in ACI 440.2R-17 that assumes full strain compatibility between the RC beam and retrofit. Due to the lack of strain compatibility for unbonded retorifts, an analytical procedure was developed to generate the moment-curvature response and is reported in Appendix D. The modeling techniques accurately predicted the load-deformation behavior observed in the experiments. The results indicated that FML is an appropriate retrofit material for RC beams, with beam behavior highly dependent on the fiber orientation within the FML. RC Beams retrofitted with fully bonded, unidirectional fibers experienced the highest strength gains but exhibited decreased ductility. In contrast, beams retrofitted with fully bonded, off-axis fibers showed moderate strength gains without a reduction in ductility. Unbonded retrofits were effective in increasing both the strength and ductility of the beams, displaying performance similar to the fully bonded retrofits fiber orientation. This study demonstrates the potential of FML as a retrofit material that offers a balance between strength enhancement and ductility. The main findings highlights the significance of fiber orientation and bonding methods in optimizing the performanae of RC beam retrofits. / Master of Science / This project explored methods to strengthen reinforced concrete (RC) beams using fiber metal laminate (FML), a material created by layering metal sheets with fiber-reinforced polymers (FRP). While FRP is commonly utilized for structural retrofits, it has significant deficiencies: its fibers are brittle and lack ductility compared to metals. FML addresses these issues by combining metals with FRP, resulting in a more ductile and reliable strengthening solution. Seven RC beams were tested by applying two-point loads near the center until failure occurred. Four of these beams were retrofitted with FML, two with FRP, and one remained unaltered as a control specimen. To prevent premature debonding failure between the RC beam and the retrofit, different bonding methods were explored: four retrofitted beams had the retrofit materials fully bonded using hybrid bonded anchorage configurations, while two featured unbonded anchorage configurations. During testing, midspan displacement, applied loads, and strain along the retrofitted areas were measured. Analytical modeling was employed to predict the behavior of RC beams with various retrofit configurations and bonding types. For the fully bonded retrofits, established guidelines from ACI 440.2R-17 were adhered to, assuming full strain compatibility between the RC beam and retrofit. Due to the lack of strain compatibility for unbonded retrofits, a new analytical procedure was developed to generate the moment-curvature response, detailed in Appendix D. These modeling techniques accurately predicted the load-deformation behavior observed in the experiments. The results demonstrated that FML is an effective material for reinforcing RC beams. Performance was largely influenced by the fiber orientation within the FML. Beams reinforced with FML having fibers aligned in one direction exhibited the greatest strength gains but reduced ductility. Conversely, beams with fibers arranged at angles achieved moderate strength increases without compromising ductility. Unbonded retrofits were also effective, enhancing both the strength and ductility of the beams in a manner consistent with fiber orientation trends. In summary, FML offers a promising method for retrofitting RC beams by balancing increased strength with maintained ductility. Fiber orientation and bonding methods are critical factors in optimizing the performance of the strengthened beams.

No description available.

Yes / This paper reports the testing of three continuously and two simply supported concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars. The amount of CFRP reinforcement in beams tested was the main parameter investigated. A continuous concrete beam reinforced with steel bars was also tested for comparison purposes. The ACI 440.1R-06 equations are validated against the beam test results. Test results show that increasing the CFRP reinforcement ratio of the bottom layer of simply and continuously supported concrete beams is a key factor in enhancing the load capacity and controlling deflection. Continuous concrete beams reinforced with CFRP bars exhibited a remarkable wide crack over the middle support that significantly influenced their behaviour. The load capacity and deflection of CFRP simply supported concrete beams are reasonably predicted using the ACI 440.1R-06 equations. However, the potential capabilities of these equations for predicting the load capacity and deflection of continuous CFRP reinforced concrete beams have been adversely affected by the de-bonding of top CFRP bars from concrete.

No / This paper presents a numerical method for estimating the curvature, deflection and moment capacity of hybrid FRP/steel reinforced concrete beams. A sectional analysis is first carried out to predict the moment-curvature relationship from which beam deflection and moment capacity are then calculated. Based on the amount of FRP bars, different failure modes were identified, namely tensile rupture of FRP bars and concrete crushing before or after yielding of steel reinforcement. Comparisons between theoretical and experimental results of tests conducted elsewhere show that the proposed numerical technique can accurately predict moment capacity, curvature and deflection of hybrid FRP/steel reinforced concrete beams. The numerical results also indicated that beam ductility and stiffness are improved when steel reinforcement is added to FRP reinforced concrete beams. (C) 2015 Elsevier Ltd. All rights reserved,

Yes / The results of testing two simply and three continuously supported concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented. The amount of GFRP reinforcement was the main parameter investigated. Over and under GFRP reinforcements were applied for the simply supported concrete beams. Three different GFRP reinforcement combinations of over and under reinforcement ratios were used for the top and bottom layers of the continuous concrete beams tested. A concrete continuous beam reinforced with steel bars was also tested for comparison purposes. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported GFRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested.

Countries world-over have thousands of critical structures and bridges which have been built decades back when strength-based designs were the order of the day. Over the years, magnitude and frequency of loadings on these have increased. Also, these structures have been exposed to environmental degradation during their service life. Hence, structural health monitoring (SHM) has attracted the attention of researchers, world over. Structural health monitoring is recommended both for vulnerable old bridges and structures as well as for new important structures. Structural health monitoring as a principle is derived from condition monitoring of machinery, where the day-to-day recordings of sound and vibration from machinery is compared and sudden changes in their features is reported for inspection and trouble-shooting. With the availability of funds for repair and retrofitting being limited, it has become imperative to rank buildings and bridges that require rehabilitation for prioritization. Visual inspection and expert judgment continues to rule the roost. Non-destructive testing techniques though have come of age and are providing excellent inputs for judgment cannot be carried out indiscriminately. They are best suited for evaluating local damage when restricted areas are investigated in detail. A few modern bridges, particularly long-span bridges have been provided with sophisticated instrumentation for health monitoring. It is necessary to identify local damages existing in normal bridges. The methodology adopted for such identification should be simple, both in terms of investigations involved and the instrumentation. Researchers have proposed various methodologies including damage identification from mode shapes, wavelet-based formulations and optimization-based damage identification and instrumentation schemes and so on. These are technically involved but may be difficult to be applied for all critical bridges, where the sheer volume of number of bridges to be investigated is enormous. Ideally, structural health monitoring has to be carried out in two stages: (a) Stage-1: Remote monitoring of global damage indicators and inference of the health of the structure. Instrumentation for this stage should be less, simple, but at critical locations to capture the global damage in a reasonable sense. (b) Stage -2: If global indicators show deviation beyond a specified threshold, then a detailed and localized instrumentation and monitoring, with controlled application of static and dynamic loads is to be carried out to infer the health of the structure and take a decision on the repair and retrofit strategies. The thesis proposes the first stage structural health monitoring methodology using natural frequencies and static deflections as damage indicators. The idea is that the stage-1 monitoring has to be done for a large number of bridges and vulnerable structures in a remote and wire-less way and a centralized control and processing unit should be able to number-crunch the in-coming data automatically and the features extracted from the data should help in determining whether any particular bridge warrants second stage detailed investigation. Hence, simple and robust strategies are required for estimating the health of the structure using some of the globally available response data. Identification methodology developed in this thesis is applicable to distributed smeared damage, which is typical of reinforced concrete structures. Simplified expressions and methodologies are proposed in the thesis and numerically and experimentally validated towards damage estimation of typical structures and elements from measured natural frequencies and static deflections. The first-order perturbation equation for a dynamical system is used to derive the relevant expressions for damage identification. The sensitivity of Eigen-value-cumvector pair to damage, modeled as reduction in flexural rigidity (EI for beams, AE for axial rods and Et 12(1 2 )3− μ for plates) is derived. The forward equation relating the changes in EI to changes in frequencies is derived for typical structural elements like simply-supported beams, plates and axial rods (along with position and extent of damage as the other controlling parameters). A distributed damage is uniquely defined with its position, extent and magnitude of EI reduction. A methodology is proposed for the inverse problem, making use of the linear relationship between the reductions in EI (in a smeared sense) to Eigen-values, such that multiple damages could be estimated using changes in natural frequencies. The methodology is applied to beams, plates and axial rods. The performance of this inverse methodology under influence of measurement errors is investigated for typical error profiles. For a discrete three dimensional structure, computationally derived sensitivity matrix is used to solve the damages in each floor levels, simulating the post-earthquake damage scenario. An artificial neural network (ANN) based Radial basis function network (RBFN) is also used to solve the multivariate interpolation problem, with appropriate training sets involving a number of pairs of damage and Eigen-value-change vectors. The acclaimed Cawley-Adams criteria (1979) states that, “the ratio of changes in natural frequencies between two modes is independent of the damage magnitude” and is governed only by the position (or location) and extent of damage. This criterion is applied to a multiple damage problem and contours with equal frequency change ratios, termed as Iso_Eigen_value_change contours are developed. Intersection of these contours for different pairs of frequencies shows the position and extent of damage. Experimental and analytical verification of damage identification methodology using Cawley-Adams criteria is successfully demonstrated. Sensitivity expressions relating the damages to changes in static deflections are derived and numerically and experimentally proved. It is seen that this process of damage identification from static deflections is prone to more errors if not cautiously exercised. Engineering and physics based intuition is adopted in setting the guidelines for efficient damage detection using static deflections. In lines of Cawley-Adams criteria for frequencies, an invariant factor based on static deflections measured at pairs of symmetrical points on a simply supported beam is developed and established. The power of the factor is such that it is governed only by the position of damage and invariant with reference to extent and magnitude of damage. Such a revelation is one step ahead of Caddemi and Morassi’s (2007) recent paper, dealing with static deflection based damage identification for concentrated damage. The invariant factor makes it an ideal candidate for base-line-free measurement, if the quality and resolution of instrumentation is good. A moving damage problem is innovatively introduced in the experiment. An attempt is made to examine wave-propagation techniques for damage identification and a guideline for modeling wave propagation as a transient dynamic problem is done. The reflected-wave response velocity (peak particle velocity) as a ratio of incident wave response is proposed as a damage indicator for an axial rod (representing an end-supported pile foundation). Suitable modifications are incorporated in the classical expressions to correct for damping and partial-enveloping of advancing wave in the damage zone. The experimental results on axial dynamic response of free-free beams suggest that vibration frequency based damage identification is a viable complementary tool to wave propagation. Wavelet-multi-resolution analysis as a feature extraction tool for damage identification is also investigated and structural slope (rotation) and curvatures are found to be the better indicators of damage coupled with wavelet analysis. An adaptive excitation scheme for maximizing the curvature at any arbitrary point of interest is also proposed. However more work is to be done to establish the efficiency of wavelets on experimentally derived parameters, where large noise-ingression may affect the analysis. The application of time-period based damage identification methodology for post-seismic damage estimation is investigated. Seismic damage is postulated by an index based on its plastic displacement excursion and the cumulative energy dissipated. Damage index is a convenient tool for decision making on immediate-occupancy, life-safety after repair and demolition of the structure. Damage sensitive soft storey structure and a weak story structure are used in the non-linear dynamic analysis and the DiPasquale-Cakmak (1987) damage index is calibrated with Park-Ang (1985) damage index. The exponent of the time-period ratio of DiPasquale-Cakmak model is modified to have consistency of damage index with Park-Ang (1985) model.