Carbon Fibre Reinforced Polymer composites are a proven method of providing structural strengthening that is lighter, non-corrosive, and less labour intensive than the application of steel plate or exterior post-tensioning. Corrosion of steel structures in bridges and other civil engineering applications induces a serious structural damage that could lead to the failure during operating conditions. Instead of replacing the damaged structures there is the current approach of repairing the corroded steel structures by strengthening the damaged steel beams or gridges using Carbon Fibre Reinforced Polymer (CFRP). The focus in this work is on tension angle members in truss type of steel structures. The loss of sectional area due to corrosion effect was represented by creating notches of different sizes (3 mm – 12 mm) in the angles. The results revealed that CFRP reinforcement is able to rehabilitate the corroded steel to the point that the tensile strength reached a value within 20% of the original value of the undamaged steel truss for artificial notch length lower than 9 mm. The effect of moisture on the corroded and rehabilitated steel structures was also investigated and the results revealed a decrease of 7% in the ultimate tensile strength of the steel truss after 2000 hours of continue immersion in water.
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The more negative potential is partly due to the strong cathodic polarization exerted by the ECE treatment, and corrosion measurements are suggested after an extended time period of depolarization that depends on the rate of oxygen arrival at the rebar (repassivation) [13, 15]. However, the several times increased concentration of alkaline ions with degrading C-S-H phase and the discolored black-brown corrosion products observed on the surface of rebar support further the possibility of a temporary alkaline attack on the pre-corroded steel. This is due to two factors. First, the treatment reduced any passive film along with any existing corrosion products on the surface of the steel leaving it susceptible to active general corrosion over the whole steel area. It also electrochemically reduced any dissolved oxygen in the local concrete pore solution, thereby eliminating any possibility of repassivation. Second, the treatment resulted in a localized accumulation of alkali (K + and Na + ) and hydroxide ions because of ion migration and water hydrolysis at the steel
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An increasing large number of structural elements such as steel beams, steel girders and chords used in the bridges, road decks, parking garages and etc., suffer from external forces (road salts, free/thaw cycles and etc.) that, unaddressed may lead to the structural deficiency of these structures over a prolonged period of time. In the interest of public safety, and with less money available for new structure design and construction, it is the writer’s position that many of these failing structures can be rehabilitated to the original design parameters. One of the most common and of significant concern is the noted deterioration of steel beams; especially the corrosion of the web section. This as noted, can be attributed to that could be due to various environmental attacks such as winter salt spray, and ineffective maintenance. One currently applied method of rehabilitation for a corroded steel beam is the attachment (welded to web section) of an additional steel plate to the affected area to replenish the loss of thickness. However, this rehabilitation method has many drawbacks such as: a dead load increase, potentially high repair cost, and additional residual stress. A better rehabilitation method to repair corroded steel beams is through the use of Fibre Reinforced Polymer (FRP) materials. FRP is a composite material consisting of two parts - the matrix (continuous phase) and the fiber (discontinuous phase). The beneficial characteristics of FRP materials are high strength-to-weight ratio, corrosion resistance, and high fatigue resistance . These materials are mostly applied using a technique to apply prefabricated FRP laminate plates or wet lay-up FRP fabrics. Commonly used FRP materials used for rehabilitation of structures include glass FRP (GFRP), carbon FRP (CFRP).
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The effects of steel corrosion become even more criti- cal in the evaluation of the mechanical properties of corroded steel bars. The change of behaviour of cor- roded steel reinforcement tested under monotonic ten- sile loads has been attributed to different reasons. At the material level, the non-homogeneous distribution throughout the bar cross-section of the different mate- rial phases originated from the modern manufacturing system named TEMPCORE ® is often considered a key factor (Apostolopoulos and Papadakis 2008; Apostolo- poulos et al. 2006; Fernandez et al. 2016a; Santos and Henriques 2015; Apostolopoulos 2007; Caprili et al. 2018). Additional mechanisms used to explain the modification of the observed mechanical properties of corroded steel bars involve the consideration of geo- metrical effects derived from the non-uniform reduc- tion of the bar cross-section. These effects include the appearance of a local bending moment due to the shift of the centre of gravity with respect to the original uncorroded cross-section and the stress concentration at the tip of a pit caused by the sudden change in cross- section, also known as the notch effect (Fernandez et al. 2016a, b; Apostolopoulos et al. 2013; Tang et al. 2014). However, due to the strong dependency between these effects and the actual corrosion shape as shown by Zhu et al. (2017; Zhu and François 2014), assuming
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Residual capacity of the corroded members is evaluated by classifying the section according to the level of corrosion. But, at times it becomes very much difficult to assess the residual capacity of an existing structure. A damage model was proposed by Kayser and Nowak which evaluated the reliability of a corroded steel girder bridge over time. Another theory called ‘interval probability theory’ was proposed by Sarveswaran for assessing the reliability of corrosion-damaged steel structures. Using this theory, the remaining thickness of a severely corroded element was represented by an interval number which expressed the range over which there was uncertainty about the thickness. Later, a methodology was developed by Hathout for assessing the reliability of existing transmission structures and lines in the presence of structural deterioration. He derived the model for probability of failure as a function of the cumulative distribution of the standardized safety margin and the damage state of the structure and then expressed the failure probability in terms of the first four moments of the safety margin probability distribution function. In the present study steel angle sections were corroded by galvanostatic method and retrofitted using FRP composites with epoxy adhesives. The specimens were then subjected to compression testing in order to understand the strength aspects. Numerical validation of corroded and retrofitted specimens were discussed.
are considered namely rigid bonded, rigid unbonded and flexible unbonded repairs (ASME PCC-2, 2008). For the rigidly bonded composite repair, the internal pipeline surface is cleaned and the composite materials are cured onto the pipe internal wall. The cured interface layer is very thin so that there is no relative deforma- tion in the interface between the composite liner and steel pipe. Rigid unbonded repair can be achieved by inserting a cured composite pipe into a steel pipeline or alternatively curing a composite repair into a pipe but preventing the form of bonding to the inside of the pipeline. For flexible unbonded composite repair, the repair material is a reinforced unimpregnated mem- brane which remains flexible (Cosham and Hopkins 2004). Moreover, most internal repair technologies are cured in place and bonded to the wall of the existing pipelines. The resin (or grout) adhesive provide suffi- cient bond strength between the existing pipeline and the repair systems. Compared with the traditional repair systems like cutting of damaged pipelines and welding, composite repair systems are more reliable and versatile (Palmer and Paisley 2000).
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Nine test specimens were supplied by Tilbury Steel. These specimens were fabricated and tested in the University of Windsor’s Structural Engineering Lab. The test specimens are identified using different labels which describe the specimen. The labels CC and RB denote control corrosion and rehabilitated beam, respectively, and the percentage of corrosion is indicated (if there is any) in front of this label. For example, the specimen 20CC represents the control corrosion specimen with 20% corrosion. The naming for the rehabilitated specimens is based on the extent of corrosion and the number of layers of fabric used. For example, the specimen, 20RB4L-B indicates that this beam specimen had 20% loss in flange thickness (20) resulting from the corrosion and the beam was rehabilitated (RB) with four layers (4L) of BFRP fabric (-B). The test matrix is shown in Table 3.1.
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For many years, different methods for computing the failure pressure of buried pipelines that transport crude oil, natural gas or any hydrocarbon derivative have been regularly implemented; however, these methods work with variables affected by uncertainty. Therefore, in this paper, the authors present a Monte Carlo methodology to evaluate the probabilistic behavior of several failure pressure methods in order to estimate their effect in the probability of failure calculations from the information published by the Pipeline Research Council International (PRCI) for the actual failure pressure of corroded pipelines.
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In this paper, in-situ formation superhydrophobic biomimetic coating on raw corroded steel surface is studied. The in-situ microscale texture of the corroded surfaces acted as the microscopical feature of the biomimetic structure, and a novel hierarchical surface feature with low surface energy formed from surface modification by chemical agents as the nanoscaled feature. This study can be a basement of applying SH surface in the anticorrosion of pipelines in the future.
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In recent years, increasing number of structural steel members with long service lives have begun to show corrosion damage that has been accumulated over time. These deficient structures will further age, crack, and weaken over time. Corrosion is one of the major causes of structural deterioration. Moreover, the prevalent use of de-icing salts in the colder countries further worsens the condition of these steel structures. According to the Infrastructure Report Card published by American Society of Civil Engineers in 2017, almost 40% of the existing bridges in the USA have already exceeded their design life of 50 years and 9.1% of existing bridges are structurally deficient . In a report published by Transportation for America in 2013, about 66,405 bridges in North America are structurally deficient and about 260 million trips are taken over these deficient bridges every day . According to the Canadian Infrastructure Report Card published in 2016 by Federation of Canadian Municipalities, about 5% of Canadian bridges are in very poor condition and has an estimated replacement value of about 50 billion CAD . Many of these structures needs immediate rehabilitation or strengthening to meet their structural demands. Traditional repair methods in steel structures which includes welding or bolting of additional steel plates have many drawbacks. Some of the major drawbacks are an increase in dead load, fatigue failure due to stress concentration resulting from welding or drilling, reduction in the durability due to the corrosion, and lesser adaptability of attached plates to fit the complex profiles. In addition, the regular services may have to be interrupted while rehabilitation work is progress. There is also a potential risk of weld cracking failure.
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tenth of typical blister width of 10 mm, and a time resolution of less than 30 s, one-tenth of that for the RANS experiment. These resolutions in both spatial and time could bring the ﬁrst quantitative measure for the study on under ﬁlm corrosion of steel. This experiment allowed us to simultaneously view most of the area of interest of a large corrosion blister. As an extension of time dependent water distribution, we derived an image, showing the average water content ratio, which was used to visualize the distribution of water accumulation in the corrosion blister.
The environmental temperature (-20 o C – 60 o C) and the effects of moisture (immersing the sample under tap water for 500 hrs – 2000 hrs) on corroded rehabilitated steel simulated by different sizes of notches (3 mm - 12mm) were considered in this investigation. To simulate the temperature difference during day and night or between seasons, the influences of the recycling temperature on the rehabilitation of the corroded steel were examined by subjecting the sample to fluctuated temperature.
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Three-point ﬂexural testing was performed in the speci- mens for creating cracks in FS2 and CS2 specimens. In this regard, specimens were loaded up to a vertical deﬂection of 3.5 mm (D3.5) in a Zwick Z250 materials testing machine (MTM) and then unloaded. In case of FM1 and CM1, specimens were loaded to a deﬂection of only 1.5 mm (D1.5). The number of cracks and crack widths were recorded. FS31 specimens were loaded up to two different levels of vertical deﬂections 5 mm and 7 mm (D5 and D7) respectively in the Zwick Z250 MTM, in order to study the effect of two different crack patterns. After unloading from the Zwick, all FS31 specimens were placed in special steel frames for sustained loading at the same level of deﬂections (D5 and D7) by tightening the bolts on both ends of each specimen as shown in Fig. 1c. In case of FS32 and FM2, cracks were formed by making notches in the specimens as shown in Table 2 and then specimens were placed and cracked in similar steel frames as FS31 specimens. The FS32 specimen cracks were formed while measuring the defor- mation over a central 100 mm gauge length on the notched surface as shown in Fig. 1c. Details of specimen surface strain and the number of notches are shown in Table 2. Figure 2a shows the way in which the number of crack and crack spacing were measured in the specimen and Fig. 2b shows the pitting depth measurement in the corroded steel bars which will be discussed in the research results section.
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The effect of surface treatment on joint strength of corroded steel sheet substrates depend- ing on time of exposure to ageing is shown in Fig. 5. As shown in Fig. 5, the highest strength was obtained in adhesive-bonded joints of corroded substrates that were prepared for bonding through cleaning with acetone and subjected to ageing for two months. The strength in those joints amount- ed to 4.10 MPa, and constituted the highest noted among the tested ageing variants. The exposure times of 14 days and 3 months produced joints whose strength corresponded to respectively 70% and 58% of the lap shear strength exhibited by joints after 2-month exposure time. Furthermore, it was observed that the strength of joints of corroded substrates that were subjected to pre- treatment with Wiko industrial degreasing agent was rather consistent in all ageing variants. The highest joint strength was obtained after 3-month exposure time, 3.69 MPa. In the remaining cases, i.e. the exposure of 14 days and 2 months, the ob- tained joint strength amounted to 3.24 MPa and 3.49 MPa respectively, which is equal to 88% and 95% of the maximum obtained strength. The scatter of results is considerably low, which indi-
The research work performed by Bai and Hauch ( 2001) proposed an analytical solution for calculating the bending moment capacity of corroded pipe under combined pressure, longitudinal force and bending moment. This solution is actually a modification of the analytical solution for calculation of bending moment capacity for noncorroded pipe under combined loading (pressure, axial loading and bending moment) condition proposed by Mohareb (1994). The corrosion defect was assumed to be symmetrical to the plane of bending which represents the worst case scenario. In this solution the moment capacity was defined as the moment at which the entire pipe cross section yields. The derived bending moment capacity equations were compared with the result from the finite element analysis. Four capacity equations were presented to cover four scenarios namely i) corroded area in compression; ii) corroded area in compression and some area in tension; iii) corroded area in tension and iv) most corroded area in tension and some area in compression. To reduce the complexity of the capacity equations, some assumptions were made for the pipe at maximum loading. The diameter-to-wall thickness (D/t) ratio was limited to 15-45 and it was assumed that the cross-section remains circular during the application of bending moment. It was also assumed that the entire cross section yielded at bending collapse. The material model was assumed to be elastic- perfectly plastic and the defect region was symmetric around the plane of bending. The corrosion defect was considered of infinite length and did not cause local stress concentration. In the analytical solution the von Mises yield criteria was used to obtain the longitudinal stress in terms of hoop stress and material yield strengths. While calculating the hoop stress due to internal pressure it was assumed that defect width had very minor influence on the collapse pressure and this assumption was confirmed by the numerical model as well.
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In this experiment, corrosion condition was controlled to be similar to an in-service tank bottom. Specimen was set on neutral sand and 380 MPa was loaded on it. During the corrosion, corrosion rate and AE activity were measured simultaneously. From the experimental results, the relation between them was examined. Detected AE signals were analyzed and classiﬁed into some groups using AE param- eters such as peak frequency and RMS (AE Root Mean Square value of the eﬀective voltage [V]) of AE waveforms. The characteristics of AE waves originated from diﬀerent AE source were analyzed by the group classiﬁcation of AE waves and the AE activity of each peak frequency. To verify the AE corrosion monitoring for real above ground tanks, AE source from corroded tank bottom was discussed with the obtained results.
It was decided to conduct five full-scale experiments for this research to verify whether or not basalt fibre reinforced polymer (BFRP) is capable of restoring the load-capacity of corroded pipes to their uncorroded state while bending. Table 3.1 shows the test matrix used in this study. The first test was performed on an uncorroded pipe specimen in order to establish a reference for the bending performance. The second and fourth specimens were machined with defects of depths of 1.2 mm (20% of the wall thickness) and 2.4 mm (40% of the wall thickness), respectively (Figure 3.1). These two tests were used to determine the effect of two corrosion depths, and to make a relative comparison to the repaired specimens. Similar to the second and fourth specimens, the third and fifth specimens were also machined with defects of the same depth. However, before testing, specimens 3 and 5 were retrofitted with ten and twenty layers of uniaxial BFRP wrap respectively. The purpose of specimens 3 and 5 was to observe whether the performance of the corroded pipe improved, relative to the unrepaired pipe.
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Corrosion generates tensile stresses in steel reinforcement surroundings in the concrete, resulting to early cracks. In addition, steel reinforcement cross sectional – area reduction is noticed thereby causing decreased in ductility of the structure, especially during the occurrence of corrosion pitting An increase in the size of reinforcing steel bars such as expansion and volume is the result of rust products, it results to weakness of the reinforcing steel bar cross- sectional area as well reduces the rate of bonding between reinforcing steel bar and concrete thereby creating stress within the concrete surroundings, furthermore, cracking and spalling of concrete is noticed due to severe stress which reduces the reinforced concrete structures designed life and durability,(Almusallam et al. 1995, Cabrera 1996, Rashid et al. 2010).
exposure to acid and 5.4.5(b) after it had been exposed to 35% nitric acid for 15 s. The diffraction pattern for 5.4.5(a) was that expected for two overlapping (111) oriented face-centred-cubic structures in parallel orientation. Hie pairs of main spots surrounding the undiffracted beam arose from the two separate phases, copper and gold, and the clusters of weaker spots around the main reflections could be accounted for by double diffraction. There was some intensity detectable at superlattice (i.e. 110) positions but this was found to be much enhanced when the specimen had been exposed to acid (fig. 5.4.5(b)). The diffraction pattern from this corroded specimen contained a 220 reflection close to the main gold 220 reflection, indicating alloy formation. This is shown more clearly in Fig. 5.4.6(a) and (b) which are microdensitometer traces taken from the above diffraction patterns. These results are consistent with the existence of separate phases of pure gold and pure copper before corrosion, and pure gold and an alloy containing 32 ± 7% gold after corrosion. It is worth noting that without depositing a standard onto these specimens then the designation of the two initial phases as pure copper and pure gold is a matter of judgement. It is of course possible that they contained up to a few percent gold or copper respectively. Since they were prepared as separate phases, it is assumed that before corrosion they are still best described as pure copper and pure gold.
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The Gutter showed similar corrosion, microstructural, and tensile behaviour as other wheel components. Furthermore, the Gutter had consistent compositional values, with only slightly elevated levels of Silicon relative to other wheel components. Therefore, based on experimental observations throughout Chapter 4, it is difficult to explain with certainty why the as-extracted Gutter specimens showed statistically improved fatigue performance relative to other wheel components. The most likely explanation may be linked to specimen surface finish, which plays a large role in high- cycle fatigue behaviour. While surface roughness was periodically measured to ensure consistency between all specimens, it was not vigorously tracked. It is possible that Gutter specimens had a superior surface finish after completion of polishing relative to other specimens. Furthermore, during machining of Gutter specimens, the machinist indicated machining of Gutter specimens proved more difficult than other wheel components. This latter point may be indicative of some work hardening during the machining process of Gutter specimens that may have artificially improved fatigue life. No matter the cause, the increase in endurance limit of the as-extracted Gutter is only 16.7% relative to the mean ‘Rim’ endurance limit. Additionally, as-extracted fatigue data is meant only as a reference to pre-corroded data. In the mining environment, surface degradation of wheel components often occurs quickly, and so no wheel component should follow as-extracted fatigue behaviour.
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