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Jacket structures and piles penetrating the seabed are connected through grouted connections. The shear key shape is designed to improve the shear strength of grouted connections. On a construction site, it is difficult to control the height error of the inner and outer steel tubes because of the environmental load. In addition, an installation error leads to an error in the arrangement of the shear keys, degrading the structure's performance. Among the construction methods for installing jacket structures, prepiling is more economical than the post-file method, but construction errors are likely. In this study, the fracture shape and maximum axial load capacity were evaluated according to the arrangement error of the shear key. It was found that when an arrangement error of the shear key occurred, the maximum axial load decreased to within 10%.

A detachable spudcan enables the operation of a jackup barge on any seabed. A general detachable spudcan uses a pin to connect the separate footing and leg. However, this type of structure can cause excessive stress on the pin. In this study, a new type of detachable spudcan reinforced with ring plates (upper and lower) is proposed to improve the structural performance of the conventional detachable spudcan. Finite element analysis revealed that the stress concentration in the connection part was relieved by reinforcing the lower and upper rings. In particular, reinforcing both lower and upper rings resulted in superior structural performance under eccentric supported conditions than when reinforcing only the lower ring. The structural strength of the spudcan when both the upper and lower rings were reinforced was found to be 120% of the spudcan as compared to when only the lower ring was reinforced. It is thought that the safety of the connection part can be secured when designing a detachable spudcan using the reinforcement plan verified in this study.

This study proposed a novel method of crushing glass aggregates to reduce the alkali-silica reaction (ASR). Glass aggregates were crushed while immersed in different calcium bearing solutions. ASR measurement and compressive strength tests of mortars incorporating the glass aggregate were performed to investigate the feasibility of the crushing method. The results indicate that the crushing method was effective in both ASR mitigation and compressive strength improvement. Calcium nitrite solution was found to be more effective than calcium chloride solution for mitigating ASR damage. The ASR expansion after 14 days, measured in accordance with ASTM C1260, was 0.228% when the glass aggregates were conventionally crushed in air, which is potentially unsafe. This value decreased to 0.082% when the aggregates were crushed in calcium nitrite solution, a value which is considered innocuous. The compressive strength of the mortar was enhanced by approximately 12% compared to that of a mortar with conventionally crushed glass aggregate by incorporating glass aggregates crushed in calcium nitrite solution.

This paper presents an improved numerical model for the reliability analysis of corrosion initiation due to the combined action of carbonation and chloride ingress. The coupled mechanism of carbon dioxide, chloride ions, heat and moisture is considered in the model. The probability of corrosion initiation is evaluated by means of a single limit state function in which the critical concentration of chloride ions depends on the degree of carbonation. In addition, the coupled diffusion coefficients are interpolated linearly depending on the degree of carbonation in order to simplify the structure of the model without compromising accuracy.

We report the fabrication of a stretchable array of active-matrix (AM) electrochromic devices (ECDs). The ECD is made of poly(3-methylthiophene) and Prussian blue electrodes with a mixed gel electrolyte of acetonitrile, poly(methyl methacrylate), propylene carbonate, and lithium perchlorate. The ECD displays can express red, green, or blue (RGB) depending on the applied voltage and has a high stability in air. It exhibits low power consumption levels of 331 and 378 μW cm−2 (10 s duration) at −1.0 and 1.0 V, respectively, and a high coloration efficiency of 201.6 cm2 C−1 at 1.0 V. A 4 × 4 AM ECD array is integrated on a deformable Ecoflex substrate via a dry transfer method using patterned liquid metal interconnections. The display shows a mechanical stability under bending and biaxial stretching by 30%. Finite element method analysis of the strain distribution also confirms that strain is not applied to the ECDs, guaranteeing stable operation of the array under deformation. Furthermore, a stretchable 6 × 6 AM ECD array for higher resolution display also exhibits mechanical stability under 30% biaxial stretching. This work demonstrates the high potential of our stretchable ECD array in low power-consuming displays for stretchable electronics, wearable devices, and electronic skin.

This study investigates the implications of carbon nanomaterial type and amount on the electrical properties of cement paste. For this, five different nanomaterials, i.e., carbon nanotube (CNT), carbon fiber (CF), graphite nanofiber (GNF), graphene (G), and graphene oxide (GO), and two different volume fractions of 0.5 and 1% were considered. In addition, the self-sensing capacity of the cement composites with nanomaterials was evaluated under cyclic compressive loads. Test results indicate that the conductivity of plain cement paste was improved by adding carbon nanomaterials. In most cases, the conductivity of the composites was reduced by an increase in curing age and a decrease in nanomaterial amount, except for CF. The composites with CNTs exhibited the best self-sensing capacity regardless of volume fraction (vf), and the order of self-sensing capacity of the composites at a vf of 1% was CNT > GO ≈ GNF > G. The composites with 0.5 and 1 vol% CFs were determined to be not appropriate for a sensor measuring compressive behaviors. The gauge factor of the composites incorporating 1 vol% CNTs was obtained as 77.2–95.5.

A safe and reliable railway operation requires an organic and systematic approach to railway maintenance. Despite the importance of timely and valid track maintenance and applicability of inspected data to the optimum track management process, inspected wear data inspected by a railway inspection system in Korea have not been utilized for decision making of maintenance scenario, but just accumulated. Moreover, the process of inspecting wear data includes some uncertainties, probabilistic-based models have more reasonable application in field. This can be accomplished by developing probabilistic-based stochastic model considering uncertainties for the prediction of rail wear using inspected data. This paper reports on the development and verification of a probabilistic forecasting model for rail wear progress. This developed forecasting model utilizes the particle filter method concept based on Bayesian theory and real inspected wear data of Seoul Metro are applied to verify the model.

A chemo-damage model is proposed to predict the expansion caused by the alkali silica reaction (ASR). The model covers the formation of the pre-expansion gel driven by alkali and the swelling of the gel driven by water. The swelling capacity of the ASR gel is quantified by the sodium to calcium ratio in the pore solution. The bound alkali in the gel recycled by calcium is also considered in this model. Both external alkali supply and internal alkali released from aggregates are included. Several sets of experimental data are compared with the simulation results for the verification of the model.

In this paper, the phantom-node method is developed for cracked plates and shells simulated by continuum mechanics based 4-node quadrilateral shell elements using the mixed interpolation of tensorial components (MITC) technique for the shear-locking removal. The proposed method permits an arbitrary crack to cut through elements. The discontinuity across the crack is described by continuous displacement fields of overlapping elements that are constructed by duplicating homologous nodes and realized on the real parts of the cracked elements. New kinematical constraints for the nodal displacements of the overlapping triple elements are derived to represent the displacement fields of the partially cracked elements. The interaction domain integral of cracked shell structures is formulated to extract the fracture parameters. Several numerical benchmark cracked plates and shells are analyzed to evaluate the accuracy and robustness of the proposed method.

The aim of this paper is to report on the fabrication of a stretchable array of high-performance solid-state micro-supercapacitors (MSCs), which can be charged with integrated, commercial Si-based solar cells (SCs). This would facilitate the powering of an integrated strain sensor. The planar MSCs comprised electrodes of potentiostatically deposited polypyrrole, on spray-coated multi-walled carbon nanotube film, and a gel-type electrolyte of LiCl/polyvinyl alcohol with a redox additive of 1-methyl-3-propylimidazolium iodide. The fabricated MSC achieved an areal capacitance of 5.17 mF cm−2. After 5000 charge/discharge cycles, the MSC retained 80% of their initial capacitance. A strain sensor was fabricated utilizing a composite film of fragmentized graphene foam and polydimethylsiloxane. Such fabricated twelve parallel connected MSCs, a strain sensor, and SCs were integrated on a single deformable polymer substrate with embedded stiff platforms of negative epoxy series resist (SU-8) via long serpentine interconnections of polyimide encapsulated Ti/Pt metal film for mechanical stability under stretching. After 1000 repetitive biaxial stretching/releasing cycles by 30%, no noticeable change was observed in the charge/discharge behavior of the MSC array. Furthermore, both the photo-charge/discharge characteristics and electrochemical performance remained stable. When the whole integrated system was attached to the wrist, the integrated strain sensor could detect both externally applied strain and the arterial pulse using the energy stored in the MSCs from the SCs.

We predict the macroscopic tensile strength and fracture toughness of fully exfoliated nano silicate clay epoxy composites accounting for the interphase behavior between the polymeric matrix and clay reinforcement. A phase field approach is employed to model fracture in the matrix and the interphase zone of the polymeric nanocomposites (PNCs) while the stiff clay platelets are considered as linear elastic material. The effect of the interphase zones, e.g. thickness and mechanical properties (Young’s modulus and strain energy release rate) on the tensile strength, and fracture parameters of the composite is studied in detail. The dissipation energy due to fracture in the PNCs is extracted for different thicknesses and properties of the interphase zones. We show through numerical experiments that the interphase thickness has the most influence on the tensile strength while the critical strain energy release rate of the interphase zones affects the dissipation energy depending on the interphase zone thickness.

Display devices that can visually present various bio-signals are a core future technology required for skin attachable wearable electronics. Quantum dot light emitting diodes (QD-LEDs), which can be used as high performance display devices, exhibit many advantages such as a narrow bandwidth, high color purity, high environmental stability, easy and fast processing, and a high brightness at low voltage. In this study, we report on the fabrication of a stretchable QD-LED array for the visual display of body movement and skin temperature signals from skin-attached sensors. After forming an array of a rigid NOA63 islands, an array of CdSe/ZnS QD-LEDs is fabricated on top of that island array and electrically connected using liquid metal Galinstan interconnections. Finally, the array of QD-LEDs on the NOA63 islands is transferred onto a stretchable elastomer substrate of Ecoflex/PDMS. Of particular importance, for stable performance of the QD-LEDs under deformation, in replacement of the conventionally used ITO, a flexible and highly transparent electrode of Au grid/Ethylene glycol doped PEDOT:PSS is used. Such a design architecture can minimize the strain applied to the QD-LEDs by concentrating the strain onto the soft elastomer film substrate and the Galinstan interconnections. As a result, the fabricated QD-LED array exhibits stable operation under both 50% uniaxial and 30% biaxial strains. After attachment of the stretchable QD-LED array onto skin, the extent of knee bending, and changes in skin temperature are displayed as changes in the pattern of the QD-LED array. This work demonstrates the potential application of our stretchable array of QD-LEDs for easy and daily monitoring of health conditions through a visual display.

In the strain-based design, pipeline steels are required to satisfy not only the stress capacity but also the strain capacity. Thus, considerable efforts have been made to meet the various requirements of the pipe-material properties that might undergo large deformation during the installation stage in various hostile environments. An adequate compressive strain capacity can help effectively avoid local buckling. Hence, highly deformable steel becomes crucial in achieving the required strain capacity. This study proposes a nonlinear finite element procedure based on the commercial software ABAQUS combined with the User-defined Material Module (UMAT), which is created using Fortran language. The Gurson–Tvergaard–Needleman (GTN) model is implemented in UMAT to fully consider the nonlinear behavior of an API X100 pipe subjected to compressive loading. The numerical simulation results of the full-scale bending test were compared with the experimental results to verify the nonlinear finite element procedure equipped with the GTN model. The simulation results are in good agreement with the experimental results. The parametric studies reveal the effects of geometric imperfections and material properties on the compressive strain limit.

Computational modeling of geological materials is challenging. Firstly, they are heterogeneous with numerous uncertainties in the input parameters and secondly, the computational cost of modeling geological structures is time consuming due to the large and different length scales involved. In this article, we propose an efficient computational method for heterogeneous geological materials based on goal oriented error estimation and adaptive mesh refinement. Instead of estimating the error in a specific norm, the proposed novel error estimation approach which is called dual-weighted residual error estimation, approximates the error with respect to the quantity of interest. The dual-weighted residual error estimation is a dual-based scheme which requires an adjoint problem. The adjoint or dual problem is described by defining the quantity of interest in a functional form. Then by solving the primal and dual problems, errors in terms of the specified quantities are calculated. In many applications in engineering geology, the material is heterogeneous. In such cases, the material properties can be regarded as random fields. This variety of material properties leads to non-uniform distributions of the solution gradients, e.g. stresses. Therefore, it is vital to apply a reliable error estimation approach to be able to do efficiently the mesh-adaptivity procedure with regard to varying material parameters with pre-defined correlation lengths. Hence, the proposed error estimator is extended by accounting for a random field model to describe the material properties. Local estimated errors are exploited in order to accomplish the mesh adaptivity procedure. The goal-oriented mesh adaptivity controls the local errors in terms of the prescribed quantities. Both refinement and coarsening processes are applied to raise the efficiency. The performance of the proposed computational approach is demonstrated for several examples.

This paper presents a comprehensive model for the prediction of the process of steel reinforcement corrosion and concrete damage in two dimensions. The ingress of chloride ions, carbonation, electrochemical reaction and corrosion-induced mechanical damage are coupled in this model. The evolution of the active zone on the reinforcement is determined automatically. Using this model, we can predict the non-uniform distribution of the corrosion product, the expansive pressure, and the growth of corrosion-induced cracks.

The growing demand for compact energy storage devices may be met through the use of thin-film microbatteries, which generally rely on charge storage in thin or conformal layers. A promising technique for creating thin-film electrodes is layer-by-layer (LbL) assembly, based on the alternating adsorption of oppositely charged species to a surface to form a nanostructured electrode. Thin-film energy storage devices must have a high energy density within a limited space, so new electrode structures, materials, and assembly methods are important. To this end, both two-dimensional MXenes and polyaniline nanofibers (PNFs) have shown promising energy storage properties. Here, we report on the LbL assembly of positively charged PNFs and negatively charged Ti

This study aims to investigate the grindability and performance of glass-blended cements depending on the grinding method and glass type. Two grinding methods, intergrinding and separate grinding, and two types of waste glass, liquid crystal display glass (LCDG) and soda-lime glass (SLG), were considered. To study grindability, the milling characteristics of the coarse waste glass and fine glass-blended mixtures were investigated. The four types of glass-blended cements produced by the two grinding methods and the two types of waste glass were evaluated on particle size distribution, chemical composition, heat flow of hydration, hydration behavior, strength development and mitigation in alkali–silica reaction (ASR) expansion. It was found that the intergrinding method was more cost-efficient in producing glass-blended cements than the separate grinding method. Intergrinding of the glass-blended mixtures resulted in finer cement and coarser glass fractions. The interground glass-blended cements showed faster hydration reactivity but slightly lower strength and mitigation in ASR expansion than did separately ground glass-blended cements.

In this study, the strength and alkali-silica reaction (ASR) of concrete by incorporating pretreated soda-lime glass particles as fine aggregates were investigated. The glass aggregates were pretreated with three different solutions: Ca(OH)2, NaOH, and a mixture of Ca(OH)2 and NaOH. The glass aggregates were pretreated for 1, 4, and 7 days to investigate the time-dependent effect. Results show that the ASR was mitigated in all pretreatments. The effect was more noticeable with pretreatment in a mixed solution. The effect increased with an increase in pretreatment time. The ASR expansion was reduced by approximately 50% by pretreating the glass aggregate in the mixed solution at 80 ° C for 7 days. Moreover, pretreatment of the glass aggregate was beneficial for strength improvement. For example, by pretreating the glass aggregate in the Ca(OH)2 solution at 80 ° C for 7 days, the 28-day compressive strength demonstrated an approximate 6% increment compared with the specimen with non-pretreated glass aggregates.

In this paper, the combined effect of domain size, lattice orientation and crack length on the mechanical properties of Graphene, namely the yield strength and strain, are studied extensively based on molecular dynamics simulations. Numerical predictions are compared with the continuum- based laws of size effect and multifractal scaling. The yield strength is found to vary with the specimen size as approximate to L-1/3, which is in agreement with the multifractal scaling law, and with the inverse square of the initial crack length as approximate to a(0)(1/2), according to the Griffith's energy criterion for fracture. (C) 2016 Elsevier B.V. All rights reserved.

This paper presents a comprehensive probabilistic model for the corrosion initiation of steel reinforcement due to the combined action of carbonation and chloride ingress in reinforced concrete structures. The coupled mechanism of the transport of carbon dioxide, chloride ions, heat and moisture is taken into account in this model. A minimum number of random variables were chosen from a sensitivity analysis to reduce the computational cost. The corrosion is assumed to be initiated when either the concentration of the free chloride ion exceeds its threshold value or the pH of the pore solution decreases to below 11. According to this model, the probability of the corrosion initiation in the above-mentioned combined action of carbonation and chloride ingress is almost two times higher than the case in which the two mechanisms are considered separately. The Kolmogorov-Smirnov test indicates that the time of corrosion initiation approximately follows a log-normal distribution in this combined action.

The residual strength of components can be abruptly reduced due to multiple site damage (MSD). In general, the fatigue and fracture performance of MSD contains a significant number of uncertainties. Major uncertainties can be characterized by initial flaw, material variability and crack growth rates, among other factors. To cope with uncertain random variables, some probabilistic methods can be considered. However, these seldom obtain efficient and reliable results because of the complexities included in computations of fatigue and fracture mechanics, and probabilistic approaches. To overcome these difficulties in the life-cycle reliability analysis of MSD, the Gaussian process (GP) response surface model has been assembled with one of the recent multiple crack analysis tools, XFEM, in this study. The assembled GP-XFEM method represents a convenient way to obtain the response surface and sensitivity factors of multiple crack propagation in a structure (or a component) under a complex environment with computational efficiency. The accuracy and advantages of the proposed method were verified by a number of experimental results and numerical examples.

The combined effect of carbonation and chloride ingress in concrete is studied in this paper. Based on the change of the pore structure and the chemical equilibrium, a comprehensive model is proposed for this problem. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Several sets of experimental data were compared with the prediction by the numerical model developed in this paper, for its verification. Parametric study shows that the differences between the combined mechanism and the independent mechanisms are significant in many aspects.

The waste glass sludge is a waste produced in the glass industry. It is in a dust form and disposed with water. In the disposal process, various cohesive agents are incorporated in order to precipitate the glass particles efficiently. In this paper, we investigate the pozzolanic reaction of the waste glass sludge incorporating precipitation additives experimentally. The consumption of calcium hydroxide, the setting time and the compressive strength and the pore structure were tested for two different types of the waste glass sludge depending on whether precipitation additives were used. It was found that the waste glass sludge incorporating the precipitation additives had a higher pozzolanic potential than the reference waste glass sludge without precipitation additives.

We report on the fabrication of a fractal-designed transparent and stretchable (TS) microsupercapacitor (MSC) as a skin-attachable energy storage device for driving an integrated strain sensor (SS). The MSC is designed to have a fractal structure with long and narrow patterns to ensure high transparency and stretchability. MnO2/Carbon nanotubes (CNTs) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/poly(methyl methacrylate) ([BMIM][TFSI]/PMMA) are used as electrodes and a stretchable electrolyte for the MSC, respectively. The fabricated MSC exhibits high transparency of 79% and an areal capacitance of 12.6 mF cm−2 at a current density of 5 mA cm−2. The TS MSC shows excellent mechanical stability in that it can maintain stable electrochemical performance even after 2000 repeated stretching cycles up to 30%. The TS SS is facilely prepared via spray coating of Ag nanowires (NWs) and subsequent curing of PDMS, where the transparency and the electrical resistance are controlled by adjusting the deposited volume of Ag NWs. Wrist bending and a wrist pulse are detected by the SS driven with the stored energy of the MSC. This work demonstrates the possible application of our TS MSC to future skin-attachable electronics as an integrated energy storage device.

Clastic sandstone is widely distributed in oil and gas reservoirs, its internal structure has many micro-defects. Under different stress environments of burial depth, significant damage evolution and plastic deformation easily occur. A series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behavior of clastic sandstone samples at different burial depths ranging from 581.28 m to 979.82 m. Results reveal that the stress-strain responses of clastic sandstone samples exhibit significant nonlinear and softening characteristics. The mechanical behavior is due to the coupling of plastic deformation and mechanical damage. Plastic and damage internal variables cause damage stiffness degradation and plastic flow. Considering the coupling of elastoplastic damage in the loading process, an elastoplastic damage coupling model is proposed to study the mechanical behavior of different burial depth clastic sandstones. The model can effectively describe the mechanical behavior of clastic sandstone, such as the volume compression and dilatancy transformation, plastic hardening and damage softening, which are in good agreement with the experimental results. Furthermore, the mechanical behavior of the clastic sandstone shows a dependency on the confining pressure and burial depth. The load-bearing capacity and the ability to resist deformation of the clastic sandstone are improved as the confining pressure and burial depth increase. Relevant results can provide reliable basis for the safe exploitation of oil and gas engineering.