This study addresses the flexural performance of sandwich panels composed of a polyurethane foam core and glass fibre-reinforced polymer (GFRP) skins. Panels with and without GFRP ribs connecting the skins have been studied. While the motivation of the study was to develop new insulated cladding panels for buildings, most of the work and findings are also applicable to other potential applications such as flooring, roofing and light-weight decking. The study comprises experimental, numerical, and analytical investigations. The experimental program included three phases. Phase I is a comprehensive material testing program of the polyurethane core and GFRP skins and ribs. In Phase II, six medium size (2500x660x78 mm) panels with different rib configurations were tested in one-way bending. It was shown that flexural strength and stiffness have increased by 50 to 150%, depending on the rib configuration, compared to a panel without ribs. In Phase III, two large-scale (9150x2440x78 mm) panels, representing a cladding system envisioned to be used in the field, were tested under a realistic air pressure and discrete loads, respectively. The deflection under service wind load did not exceed span/360, while the ultimate pressure was about 2.6 times the maximum factored wind pressure in Canada. A numerical study using finite element analysis (FEA) was carried out. The FEA model accounted for the significant material nonlinearities, especially for the polyurethane soft core, and the geometric nonlinearity, which is mainly a reduction in thickness due to core softness. Another independent analytical model was developed based on equilibrium and strain compatibility, accounting for the core excessive shear deformation. The model also captures the localized deformations of the loaded skin, using the principals of beam-on-elastic foundation. Both models were successfully validated using experimental results. Possible failure modes, namely core shear failure, and compression skin crushing or wrinkling were successfully predicted. A parametric study was carried out to explore further the core density, skin thickness, and rib spacing effects. As the core density increased, flexural strength and stiffness increased and shear deformations reduced. Also, increasing skin thickness became more effective as the core density increased. The optimal density was 95-130 kg/m3. Reducing the spacing of ribs enhanced the strength up to a certain level; It then stabilized at a spacing of 2.9 times the panel thickness. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-21 16:29:00.315

Masonry arch bridges have played a significant role in the road and rail transportation network in the world for centuries. They are exposed to damage due to overloading and deterioration caused by environmental actions. In order to reestablish their performance and to prevent their collapse in various hazardous conditions, many of them require strengthening. Fibre reinforced polymer (FRP) systems are increasingly used for repair and strengthening of structures, with particularly widespread application to concrete structures. However, the application of FRP composites to masonry structures is less well established due to the complexity of masonry caused by the material discontinuity. FRP strengthening masonry arch bridges has been even less studied due to the additional complexity arising from the co-existence of the normal interfacial stress and the shear interfacial stress at the curved FRP-to-masonry bondline. This thesis presents an extensive study investigating the behaviour of FRP strengthened masonry bridges. The study started with a laboratory test of a two span masonry arch bridge with sand backfill. A single ring arch bridge was first tested to near failure, and then repaired by bonding FRP into their intrados and tested to failure. It was found that the FRP strengthening not only improved the loading capacity and stiffness of bridge, but also significantly restrained the opening of cracks in the masonry. Shear and peeling debonding of FRP was observed. There have been two common strategies in finite element (FE) modelling of FRP strengthened structures in meso-scale: direct model and interface model. The former is necessary when investigating the detailed bond behaviour but challenges remain due to the difficulties in concrete modelling. A new concrete damage model based on the plastic degradation theory has been developed in this study to study the bond behaviour of FRP strengthened concrete structure. This robust model can successfully capture this bond behaviour and simulate the entire debonding process. A numerical study of masonry arch bridges including the backfill was conducted to study the behaviour of masonry arch bridge. A total of four modelling strategies were examined and compared. Although they all can successfully predict the behaviour of arch, a detailed solid model newly developed in this study is more suitable for modelling both plain masonry and FRP strengthened structures. Finally, a numerical study of bond behaviour and structural response of FRP strengthened masonry arch structures with sand backfill was conducted. In addition to the masonry and backfill, the mixed mode interfacial behaviour was modelled by the aforementioned interface model strategy and investigated in detail to achieve a deeper understanding of the behaviour of FRP strengthened masonry arch structures. The results are in close agreement with test results, and highlight the influence of the key parameters in the structural response to failure and revealed the mechanisms on how the load is transmitted through this complex multi-component structural system.

Tests results of three flanged and two rectangular cross-section concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars are reported. In addition, a companion concrete flanged beam reinforced with steel bars is tested for comparison purposes. The amount of CFRP reinforcement used and flange thickness were the main parameters investigated in the test specimens. One CFRP reinforced concrete rectangular beam exhibited concrete crushing failure mode, whereas the other four CFRP reinforced concrete beams failed owing to tensile rupture of CFRP bars. The ACI 440 design guide for FRP reinforced concrete members underestimated the moment capacity of beams failed owing to CFRP tensile rupture and reasonably predicted deflections of the beams tested. A simplified theoretical analysis for estimating the moment capacity of concrete flanged beams reinforced with FRP bars was developed. The experimental moment capacity of the CFRP reinforced concrete beams tested compared favourably with that predicted by the theoretical analysis developed.

War, terrorist attacks, explosions, progressive collapse and other unforeseen circumstances have damaged many structures, including buildings and bridges in war- torn countries such as Iraq. Most of the damaged structural members, for example, beams, columns and slabs, have not totally collapsed and can be repaired. Nowadays, carbon fibre reinforced polymer (CFRP) is widely used in strengthening and retrofitting structural members. CFRP can restore the load- carrying capacity of damaged structural members to make them serviceable. The effect of using CFRP to repair the damaged beams has not been not properly addressed in the literature. This research has the aim of providing a better understanding of the behaviour of reinforced concrete beams strengthened or repaired with CFRP strip under impact loading. Experimental and analytical work were conducted in this research to investigate the performance of RC beams strengthened or repaired using CFRP. To study the impact behaviour of the CFRP reinforced concrete beams, a new heavy drop weight impact test machine has been designed and manufactured to conduct the experimental work. Twelve RC beams were tested experimentally under impact load. The experimental work was divided into two stages; stage 1 (strengthened) and stage 2 (repair). At stage 1, three pairs of beams were tested under impact loading. External bonded reinforcement (EBR) and near surface mounted (NSM) techniques were used to strengthen the RC beams to find the most effective technique. Three pairs of beams were tested in stage 2 (repair). Different degrees of damages were induced using different impact energies. NSM technique was used to repair the damaged beams using CFRP strip. Stiffness degradation method was used to assess the degree of damage in beams due to impact. The study investigated the stiffness, bending load, impact energy, deflection and mode of failure of CFRP strengthened or repaired beams under impact loading. The distribution of the stresses, strains, accelerations, inertia forces, and cracks in the beam under impact loading was also investigated in this study. Empirical equations were proposed in this research to predict the bending load and maximum deflection of the damaged and repaired beams under impact loading. For validation purposes, finite element analysis was used with the LUSAS package. The FEA results were compared with the experimental load-deflection curves and ultimate failure load results. In this research, to simulate a real situation, different models were used to simulate the bonding between the CFRP and concrete and also between steel bars and concrete. In these FEA models, the bonding between the concrete and the CFRP was modelled using the Drucker-Prager model. To simulate the bonding between steel and concrete, a joint element was used with spring constants to model the bond between steel bars and surrounding concrete. The analytical results were compared with the experimental results. In most previous research, FEA has been used to simulate the RC beams under impact loading without any damage. In this thesis, a new 3D FEA model was proposed to simulate and analyse the damaged RC beams under impact loading with different degrees of damage. The effect of the damage on concrete stiffness and the bonding between the steel bars and the concrete were investigated in FEA model. The damage was modelled by reducing the mechanical properties of the concrete and the bonding between steel bars and concrete. This thesis has contributed to improving knowledge of the behaviour of damaged beams repaired with CFRP, and the experimental work conducted, together with the numerical analysis, have provided essential data in the process of preparing a universal standard of CFRP design and construction. In the FEA model, the damage to the beams due to impact loading was successfully modelled by reducing the beam stiffness.

<div>Research has shown that many adjacent box beam bridges in Indiana experience premature deterioration. Primarily caused by leaking joints between beams, this deterioration leads to corrosion and/or fracturing of prestressing strands, ultimately resulting in flexural deficiency of the bridge. A testing program was designed to simulate this observed deterioration by constructing test specimens and implementing various strengthening techniques using fiber reinforced polymer (FRP) systems. The objective of this testing program is to investigate the effectiveness of FRP strengthening systems to increase or even regain the full capacity of beams that have effectively lost tension reinforcing steel due to corrosion. The FRP-strengthened beam specimens incorporate the use of near-surface-mounted and externally bonded systems. Reinforcing bars in the beams are excluded or cut to simulate deterioration. Furthermore, two different methods of end anchorage for the externally bonded sheets, FRP fan anchorage and U-wrap anchorage, are investigated. Results and conclusions from the testing program are described in order to help advise best practices in implementing the aforementioned strengthening systems. </div>

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Although fiberglass reinforced polyester manholes and wetwalls have been proven by the American Society for Testing Materials (ASTM) and are currently being used in some parts of the world, there still exists a lack of investigation for testing manhole covers made with different inorganic fillers under static and dynamic behavior. The filler would not only improve the mechanical properties of fiber-reinforced polymer matrix composite not otherwise achieved by the resin ingredients alone but also lower the overall manufacturing costs by decreasing the amount of fiber content without adversely affecting the composite’s mechanical properties. The main objective involved the development of fiberglass laminated manhole covers with different inorganic fillers and to study the static and dynamic behavior of the material by performing experimental and numerical analysis. The materials used for the composite laminated test specimens consisted of E-glass woven roving fabric, epoxy, and filler. Two types of inorganic fillers were used for this study, calcium carbonate and high-density adhesive fillers. The static/dynamic test results showed that the laminates made with fiberglass and filler experienced lower performance in tensile strength but higher improvement in flexural strength. The modal analysis results showed that laminates with less filler experienced higher modes within the specified frequency range. This was expected since the material property of filler increased the stiffness and damping behavior in the composite material.

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yes / Tests results of three flanged and two rectangular cross-section concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars are reported. In addition, a companion concrete flanged beam reinforced with steel bars is tested for comparison purposes. The amount of CFRP reinforcement used and flange thickness were the main parameters investigated in the test specimens. One CFRP reinforced concrete rectangular beam exhibited concrete crushing failure mode, whereas the other four CFRP reinforced concrete beams failed due to tensile rupture of CFRP bars. The ACI 440 design guide for FRP reinforced concrete members underestimated the moment capacity of beams failed due to CFRP tensile rupture and reasonably predicted deflections of the beams tested. A simplified theoretical analysis for estimating the moment capacity of concrete flanged beams reinforced with FRP bars was developed. The experimental moment capacity of the CFRP reinforced concrete beams tested compared favourably with that predicted by the theoretical analysis developed.

Yes / The bond between FRP bars and concrete, the foremost performance for implementation of such reinforcements to corrosion-free concrete structures, is still unsatisfied due to the weak nature of duplex film in the interface. The existing approaches show low efficiency in improving the microstructures and bond between FRP bars and concrete. To address these issues, this paper provided a new approach for improving the bond between FRP bars and concrete by incorporating nanomaterials, as well as explored the modifying mechanisms and established the bond-slip models. For these purposes, the pull-out test, scanning electron microscope observation, as well as energy dispersive spectrometry analysis were performed. The experimental results demonstrated that the presence of nanomaterials increased the ultimate bond strengths between glass/carbon FRP bars and concrete by up to 16.2% and 37.8%, while the corresponding slips decreased by 28.7% and 35.4%, respectively. Such modification effects can be attributed to the optimized intrinsic composition and the reduced pore content of hydration products in the interface, especially in the duplex film, through the nanomaterial enrichment and nano-core effects. The bond-slip relationship between FRP bars and concrete with nanomaterials can be accurately predicted by the mBPE model. / The authors would like to thank the funding offered by the National Science Foundation of China (51978127 and 51908103), and the Fundamental Research Funds for the Central Universities (DUT21RC(3) 039).