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A mesoscopic plastic strain-based fatigue model is introduced to evaluate the fatigue damage of typical fillet welded details of orthotropic steel decks. Verification of the model is performed by comparing the experimental lives of structural steels under biaxial random loadings. When the model was used to estimate the fatigue damage of fillet welded details of an orthotropic steel deck, fatigue damages that significantly deviate from the nominal stress-based approach were observed. Simplified formulae are proposed to predict the multiaxial fatigue life of fillet welded detail using only nominal stress-based fatigue damage. Proposed relations show good agreement with the experimental fatigue lives of fillets welded joints. Introduction Most of the constructional details of steel structures are generally subjected to the effect of stress concentration. This is one of the main reasons for fatigue damage (Fisher et al., 1987; Imam et al., 2005, 2007). Inspections of orthotropic steel decks (i.e., fabricated steel decks that consist of a deck plate stiffened longitudinally with ribs) can often detect fatigue cracks in some of the welded details (Xiao et al., 2006, 2008; Fu et al., 2019). The current fatigue life assessments of these decks are usually calculated using uniaxial fatigue theories (Sonsino et al., 2012; Fu et al., 2019). The crack propagation directions are not perpendicular to the nominal stress direction. This indicates that these welded details are in a state of multiaxial stress and subject to multiaxial fatigue damage. A considerable number of multiaxial fatigue theories have been published in the literature; they can be classified into a few main approaches such as the equivalent effective stress approach, maximum principle stress approach, critical plane approach, strain energy approach, and plastic meso strain-based approach (Carpinteri et al., 2003; Jabbado and Maitournam, 2008; Siriwardane et al., 2009). This classification is mainly based on the fatigue damage variable. The equivalent effective stress approach or maximum principle stress approach is mostly used in steel design codes. The fatigue lives calculated according to these two approaches deviate from the experimental fatigue lives, whereas those calculated according to the critical plane and plastic meso strain-based approaches give good agreement with experimental fatigue lives (Carpinteri et al., 2003; Siriwardane et al., 2009). However, applications of these approaches to fillet welded details of steel structures are few because of the difficult process of model parameter determination and the complexity of algorithms (Fu et al., 2019).
This paper studies the nonlinear dynamic response of the bottom-hinged oscillating wave surge converters (OWSCs) based on both the frequency-domain and time-domain methods under regular waves. The linearizations of nonlinear stiffness, drag moment, and power takeoff (PTO) frictional moment were applied in the nonlinear frequency-domain analysis. The numerical results of the pitch amplitude in study cases compared well with the published experimental data. The nonlinear items cannot be neglected, especially when the pitch amplitude grows up to 30. Surface-piercing OWSC can capture more power than the same-sized fully submerged one in most wave conditions. The moderate increase of the PTO stiffness for a thin OWSC helps to enhance the peak of efficiency. A proper PTO damping helps to maximize the efficiency for peak energy conditions. The PTO friction can significantly reduce the efficiency at the whole wave period range, whereas the maximum influence of the viscosity occurs at the resonant wave period. Introduction A bottom-hinged oscillating wave surge converter (OWSC) is a nearshore device with the operation principle of moving back and forth like a flap in the waves to absorb wave energy. Babarit et al. (2012) showed that the bottom-hinged OWSCs were able to capture more mean annual power than most other wave energy converters (WECs)—in particular, heaving floaters. Budal’s upper bound (Budal and Falnes, 1982) explained that the maximum captured wave power of the bodies oscillating in surge or sway was double that of the axisymmetric heaving bodies. The bottom-hinged OWSC can either be fully submerged or pierce the water free surface. The most well-known devices, because of their advanced stage of development, are the WaveRoller and the Oyster, which are illustrated in Fig. 1 (Cheng et al., 2019). The Finnish company AW-Energy has been developing WaveRoller technology since 2004. Oyster was being developed in the early 2000s by Aquamarine Power Ltd. in cooperation with Queen’s University Belfast. The main difference between them is the position of the top edge, which is fully submerged for WaveRoller and pierces through the water surface for Oyster.
In the present paper, a quasi nonhydrostatic numerical (QNH) method for marine hydrodynamics is presented, based on a complete wave–current coupling in the time domain. In fully nonhydrostatic methods, free surface flows are typically handled by 3-D Navier–Stokes equations (e.g., the free surface fractional step method). In the QNH method, the flow is computed as in hydrostatic models, but the pressure is given by a suitable vertical distribution, taking into account wave propagation. Namely, the proposed QNH method avoids the numerical solution of the time-consuming Poisson equation for fully nonhydrostatic pressure. Some numerical 2-D and 3-D results for simple-shaped test cases are shown. Introduction Shallow water flow analysis is one of the most important issues in coastal engineering. The main features of this framework are wave refraction and diffraction, shoaling and breaking, wave– structure interaction, jet diffusion, and wave–current interaction. The classical approach is typically based on the separation between wave and current features. Usually, waves are studied by means of spectral methods or by using models that describe their statistical properties, such as WAM (WAMDI Group, 1988) and SWAN (Booij et al., 1996). On the other hand, concerning coastal currents, depth-averaged 2-D equations are widely implemented in the hypothesis of hydrostatic pressure distribution. Indeed, although 3-D models are widely used, sometimes the geometry of the problem (i.e., large, shallow embayments) allows the use of depth-averaged equations, which are still successfully used in some applications. For examples, see Casulli (1990), Borthwick and Barber (1992), Lloyd and Stansby (1997), Zhou and Stansby (1999), Guillou and Nguyen (1999), Liska and Wendroff (1999), Lalli et al. (2004, 2007, 2010), Bates et al. (2010), Kanayama and Dan (2013), and Pudjaprasetya and Magdalena (2014). Wave–current interaction, in this framework, is typically tackled by means of the radiation stress approach (Longuet-Higgins and Stewart, 1964), to account for the mean flow induced by wave motion. This term, obtained by means of wave models, is introduced in current solvers as barotropic forcing.
Very flexible floating structures have been proposed for offshore floating photovoltaics installation. Characterized by having structural lengths much longer than wavelengths, small thickness, and low bending stiffness, these structures are prone to large vertical deflections and strong hydroelastic interactions. Experimental information on these structures is scarce. In this study, we employed digital image correlation (DIC) to investigate the hydroelastic interaction of a flexible floating sheet with a length-to-height ratio of 1,000 in regular long-crested head waves. The wavelength was one-tenth and one-fifth of the structure length, with a wave steepness of 0.04. The repeatability of wave conditions and measurement results was demonstrated, and measurement errors were quantified. Surface elevations showed that the sheet followed a local wave elevation in long waves. In shorter waves, strong hydroelastic interactions led to wave lengthening underneath the floating structure and three-dimensional (3D) effects across the structure width. Wave lengthening agreed well with prediction from the hydroelastic dispersion relation. Observed 3D effects necessitate further research into the possible influence of viscoelastic effects. It was shown that the DIC technique is suitable to measure flexible floating structures in waves with low error and good repeatability. Experimental data are publicly available. Introduction Over the past decennia, investigation of the hydroelastic response of floating structures has been mainly motivated by research on sea ice and very large floating structures (VLFSs); see the reviews by Karmakar et al. (2011) as well as Squire (2007, 2011), Chen et al. (2006), and Lamas-Pardo et al. (2015). More recently, hydroelasticity has received renewed attention with the rise of (offshore) floating photovoltaics (FPVs). Large modular floating structures for rigid photovoltaic (PV) panels are envisaged in various projects, as summarized by Trapani and Redón Santafé (2015). Flexible structures for FPVs based on thin-film PV modules have been demonstrated to have technical and economic potential (Trapani et al., 2013; Trapani and Millar, 2014).
Mirabolghasemi, Maryam (Mississippi State University) | Heshmati, Mohammad (Mississippi State University) | Thorn, Dakota (Mississippi State University) | Shelton, Blake (Mississippi State University) | Diop, Fatou (Mississippi State University)
Abstract End-of-life production or injection wells may be converted into wellbore heat exchangers for geothermal energy extraction. Whether this conversion is technically and economically feasible depends on several factors such as geothermal potential of the formation, well depth, and working fluid circulation parameters. Here we present a case study where we analyze these parameters and determine their optimum operational brackets. We focus on repurposing active wells that are located in regions with high geothermal potential in the state of Mississippi. Geothermal gradient map of the state of Mississippi was used to select potential candidate wells. Well logs of these candidate wells were used to find formation temperature and other properties such as well diameter and depth. Next, we conducted heat transfer calculations to estimate the temperature rise of various working fluids as a result of circulating inside these wellbores. We ran sensitivity analyses to determine the effect of circulation rate, tubing insulation, and time. Finally, we estimated the power production potential of each well. Our results indicate that geothermal energy production through repurposed end-of-life wells may be viable depending on well depth and geothermal potential of the region. With insulated tubing, the thermal energy delivered by a number of candidate wells is sufficient for a small-scale binary power plant with organic Rankine cycle.
BP is in the midst of planning a large-scale hydrogen-production facility in the Teesside area of northern England that may be operational as soon as 2025. The company confirmed in a release on 29 November that the initial phase of the project, called HyGreen Teesside, is slated to have 60 MW of electrolyzer capacity by 2025--or enough hydrogen output to fuel about 1,300 trucks. The project is pending a final investment decision that BP said it expects to make by 2023. The London-listed supermajor said, depending on demand, additional buildout of the facility could scale hydrogen production up to 500 MW of electrolyzer capacity by 2030. As the name suggests, HyGreen Teesside is to rely on renewable sources of electricity to generate "green" hydrogen for use in the transportation and industrial sectors.
What is the energy transition, and why should you care? As society is actively making goals to shift away from carbon-intensive processes--such as combusting coal and gas for power and heat-use production--a need for more clean and reliable power and heating/cooling production is emerging. Wind, solar, and other renewable energy sources can generate emission-free power for our grid, but these clean energy resources are intermittent in their supply and therefore cannot be solely relied on for a baseload (constant) supply of energy like coal and gas. Because of this, the industry should focus on utilizing conventional geothermal and industrial waste-heat to provide a baseload resource for reliable emission-free power and heating/cooling projects. Conventional geothermal energy projects rely on drilling multiple miles into the earth (anywhere from 1 to 4 miles) where high-temperature geothermal brine (greater than 70 F) is produced to surface.
Gray Alton is the vice president of Project Development at Terrapin Geothermics (Terrapin). He leads the company's geographical expansion across Canada and internationally. With 17 years of construction and project development experience, Alton scouts project opportunities and brings together all stakeholders required to conceptualize, develop, and finance waste heat and geothermal power projects.
Three sacrosanct years as governments across the world have unleashed ambitious net-zero targets at the recent COP26 conference. Undoubtedly, the race to achieve net-zero has gathered momentum. Governments, companies, and institutions have all joined the bandwagon working hard to meet these ambitious decarbonization targets. Recent commitments by a number of governments to net-zero emission targets have underlined both the need and the desire to rapidly reduce hydrocarbon consumption. To meet these ambitious targets, existing and new technologies will need to be deployed at a pace and scale far beyond anything previously imagined or experienced.
Waste Not … Clean Energy Fuels and BP announced that their renewable natural gas (RNG) joint venture will build on previously announced plans to finance and develop new projects at dairy farms, starting in the Midwest. Located in South Dakota and Iowa, the dairy farms, with more than 30,000 cows, have the estimated potential to convert the methane produced from waste into more than 7 million gallons of RNG annually. Agriculture accounts for nearly 10% of US greenhouse-gas (GHG) emissions, according to the US Environmental Protection Agency, and the idea is that capturing methane from farm waste can lower these emissions. RNG is used as a transportation fuel and has lower GHG emissions on lifecycle basis when compared with conventional gasoline and diesel. The California Air Resources Board has given similar projects a carbon intensity (CI) score of weighted average of 320 compared with CI scores of 101 for conventional diesel fuel and 15 for electric batteries.