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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.

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.

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.

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.

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.

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.

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.

The speed of vehicles on highways has increased due to improved driving environments. However, this increased speed has become one of the main reasons for collisions between vehicles and ro...

This paper presents a computational reliable optimization approach for internal cooling channels in Ceramic Matrix Composite (CMC) under thermal and mechanical loadings. The algorithm finds the optimal cooling capacity of all channels (which directly minimizes the amount of coolant needed). In the first step, available uncertainties in the constituent material properties, the applied mechanical load, the heat flux and the heat convection coefficient are considered. Using the Reliability Based Design Optimization (RBDO) approach, the probabilistic constraints ensure the failure due to excessive temperature and deflection will not happen. The deterministic constraints restrict the capacity of any arbitrary cooling channel between two extreme limits. A “series system” reliability concept is adopted as a union of mechanical and thermal failure subsets. Having the results of the first step for CMC with uniformly distributed carbon (C-) fibers, the algorithm presents the optimal layout for distribution of the C-fibers inside the ceramic matrix in order to enhance the target reliability of the component. A sequential approach and B-spline finite elements have overcome the cumbersome computational burden. Numerical results demonstrate that if the mechanical loading dominates the thermal loading, C-fibers distribution can play a considerable role towards increasing the reliability of the design.

It is well known that the seismic performance of bridge systems is directly related to that of its columns since these provide the lateral resistance of the bridge and dissipate the input energy induced from ground motions. However, segmental bridge columns have small energy dissipation capacity, compared to conventional monolithic columns. In order to improve the energy dissipation capacity of the columns, several approaches have been suggested such as the use of mild steel bars, high-performance steel bars, exterior yielding braces, and elastomeric bearing pads, which are installed at the base of the columns. Recently, a combination of cast-in-place (CIP) and precast has been suggested by other researchers to increase the energy capacity. As an example of CIP application, a new precast segmental column is suggested in this paper and its cyclic behavior is examined. The base of the present circular segmental column is cast-in-place, while the upper parts are given by partial precast hollow circular segments. The column specimen has a height of 7500 mm, a diameter of 1500 mm and reinforcement ratios of 1.23–1.46%. In the cyclic test, the vertical load applied to the top of the column is about 10% of the column’s nominal strength. The results of the experimental test show that the column has excellent energy dissipation capacity producing an equivalent viscous damping ratio of about 23% at 4.29 drift ratio (final drift). The ductility ratio is 4.67 and the peak lateral strength is also high, namely about 26% of the total applied vertical load. A simplified analytical model of the column is developed and the results compared to those of the cyclic test. Sectional moment–curvature envelopes are used for the analytical model. Furthermore, nonlinear time history analyses are conducted using Northridge (Newhall) earthquake records. From the seismic analysis, the peak acceleration responses are shown as 0.23–0.25 g. The values are much smaller than the values given by the elastic response spectra of the earthquake records since the column produces the enough energy dissipating and yielding behavior.

A probabilistic approach is presented for the prognosis of fatigue crack growth for asphalt concretes using the particle filtering method based on Bayesian theory. The random response of fatigue behavior is successively updated with the accumulation of the measured data by the particle filtering method. During the updating, particles with high probability are reproduced more, while others are eliminated via resampling procedures. The J integral is adopted for the fatigue crack growth to take into account the viscoelastic characteristics of asphalt concretes. The prognosis of fatigue crack growth and remaining service life under different conditions is presented using this method.

The flexural resistance of fiber reinforced cementitious composites (FRCCs) under biaxial condition was investigated by using two different types of biaxial bending test methods: the biaxial flexural test (BFT) and the centrally loaded round panel test (RPT). The flexural responses of FRCCs under biaxial condition were then compared with those of FRCCs under uniaxial condition; i.e. four-points bending test (4PBT). The test results, including the equivalent biaxial strength and normalized energy absorption capacity of the RPT, were found to be clearly higher than those of the BFT, and completely different cracking behavior was observed between the two biaxial test methods; the BFT generated numerous randomly distributed micro-cracks at the bottom of specimens, whereas the RPT mostly showed three major cracks, with minor radial cracks around them. In addition, the equivalent flexural tensile strength and normalized energy absorption capacity of the FRCCs under biaxial condition were found to be higher than those under uniaxial condition. The energy absorption capacity and the ratio of flexural tensile strength to the direct tensile strength of FRCCs are dependent on the stress state.

An extended isogeometric element formulation (XIGA) for analysis of through-the-thickness cracks in thin shell structures is developed. The discretization is based on Non-Uniform Rational B-Splines (NURBS). The proposed XIGA formulation can reproduce the singular field near the crack tip and the discontinuities across the crack. It is based on the Kirchhoff–Love theory where C 1 -continuity of the displacement field is required. This condition is satisfied by the NURBS basis functions. Hence, the formulation eliminates the need of rotational degrees of freedom or the discretization of the director field facilitating the enrichment strategy. The performance and validity of the formulation is tested by several benchmark examples.

We propose a concurrent multiscale method for fracture coupling two three-dimensional continuum domains. Fracture in both domains is treated by the extended finite element method. The coupling is based on the Arlequin method which blends the energies of different scales in a so called "handshake domain". To our knowledge, it is the first time that a three dimensional extended Arlequin method for fracture is reported for dynamic applications. To show the suitability of the proposed method, two crack problems with a very fine region around the crack front are solved. The results show that the method is capable of effectively coupling the two regions while having the same accuracy of the full scale model based on a very fine mesh. DFG, Qatar National Research Fund, Grant No. NPRP 09-145-2-061 and Humboldt Foundation. Scopus

The paper presents a multiscale method for crack propagation. The coarse region is modelled by the differential reproducing kernel particle method. Fracture in the coarse scale region is modelled with the Phantom node method. A molecular statics approach is employed in the fine scale where crack propagation is modelled naturally by breaking of bonds. The triangular lattice corresponds to the lattice structure of the (111) plane of an FCC crystal in the fine scale region. The Lennard-Jones potential is used to model the atom-atom interactions. The coupling between the coarse scale and fine scale is realized through ghost atoms. The ghost atom positions are interpolated from the coarse scale solution and enforced as boundary conditions on the fine scale. The fine scale region is adaptively refined and coarsened as the crack propagates. The centro symmetry parameter is used to detect the crack tip location. The method is implemented in two dimensions. The results are compared to pure atomistic simulations and show excellent agreement. (C) 2014 Elsevier B. V. All rights reserved.

Cement-based sensors with hybrid conductive fillers using both carbon fibers (CFs) and multi-walled carbon nanotubes (MWCNTs) were experimentally investigated in this study. The self-sensing capacities of cement-based composites with only CFs or MWCNTs were found based on preliminary tests. The results showed that the percolation thresholds of CFs and MWCNTs were 0.5–1.0 vol.% and 1.0 vol.%, respectively. Based on these results, the feasibility of self-sensing composites with four different amounts of CFs and MWCNTs was considered under cyclic compression loads. When the amount of incorporated CFs increased and the amount of incorporated MWCNTs decreased, the self-sensing capacity of the composites was reduced. It was concluded that cement-based composites containing both 0.1 vol.% CFs and 0.5 vol.% MWCNTs could be an alternative to cement-based composites with 1.0 vol.% MWCNTs in order to achieve equivalent self-sensing performance at half the price. The gauge factor (GF) for that composite was 160.3 with an R-square of 0.9274 in loading stages I and II, which was similar to the GF of 166.6 for the composite with 1.0 vol.% MWCNTs.

In this work, we perform phase field simulations of ideal grain growth in a distorted polycrystalline aggregate. The distorted microstructure is assumed to be generated by homogenous deformation of an initially equiaxed polycrystalline aggregate. Phase field theory of curvature driven grain boundary migration under distortion is developed and the phase field kinetic relations are implemented in a numerical code based on an explicit time integration procedure. As a benchmark example, phase field simulations of the shrinkage of a distorted circular grain are performed and compared with that of an undistorted elliptical grain to validate the phase field theory and its numerical implementation and also to study the effect of distortion on the kinetics of grain boundary migration. The non-equiaxed distorted grain evolves towards an equiaxed geometry by curvature-driven boundary migration. The evolution rate towards equiaxity is proportional to the distortion magnitude. However, the distortion regardless of its magnitude has no effect on the decrease rate of the distorted grain surface area. We also investigate the evolution of a distorted polycrystalline microstructure by phase field simulations. The elongated distorted grains grow and evolve towards equiaxed grains by ideal grain growth. It has been observed that the distortion influences the directional measure of average grain size to a large extent, but the nondirectional average characteristics of the microstructure are not affected.

An asymmetric vibration is proposed for the design consideration of finger-type bridge joints. It is shown, both experimentally and numerically, that the vibration of the joint-plate is not symmetric, but asymmetric; and that the end moment of finger-type bridge joints becomes maximum when the joint plate springs upward, after the load moves out from the joint, in which the tension of the anchor bolts due to this upturned vibration is much greater than the static load case with the load at the tip of the joint-plate. A simplified design formula is developed based on an energy concept, to consider this new failure mode in the design procedure. It is shown that the actual maximum moment and tension can be closely estimated by a simple formula.

In this study, flexural strength properties of concrete under biaxial stress state were experimentally investigated. Tests for size effect and fatigue behaviour of concrete under biaxial stress were carried out by the ASTM C 1550 and the biaxial flexure test(BFT). The results given by the biaxial tests were compared to those by the third-point bending test. Test results showed that biaxial flexural strengths obtained from the ASTM C 1550 and the biaxial flexure test are greater than the strength by the third-point bending test. As the size increases, the uniaxial and biaxial flexural strength decreases. However, the slope of the size effect of the biaxial strength was greater than that of the uniaxial strength. Finally, the fatigue response of concrete under the biaxial stress state was similar with that for uniaxial stress state.

The effect of lattice orientation and crack length on the mechanical properties of Graphene are studied based on molecular dynamics simulations. Bond breaking and crack initiation in an initial edge crack model with 13 different crack lengths, in 10 different lattice orientations of Graphene are examined. In all the lattice orientations, three recurrent fracture patterns are reported. The influence of the lattice orientation and crack length on yield stress and yield strain of Graphene is also investigated. The arm-chair fracture pattern is observed to possess the lowest yield properties. A sudden decrease in yield stress and yield strain can be noticed for crack sizes < 10 nm. However, for larger crack sizes, a linear decrease in yield stress is observed, whereas a constant yield strain of 0.05 is noticed. Therefore, the yield strain of 0.05 can be considered as a critical strain value below which Graphene does not show failure. This information can be utilized as a lower bound for the design of nano-devices for various strain sensor applications. Furthermore, the yield data will be useful while developing the Graphene coating on Silicon surface in order to enhance the mechanical and electrical characteristics of solar cells and to arrest the growth of micro-cracks in Silicon cells.

This paper presents a novel numerical procedure based on the combination of an edge-based smoothed finite element (ES-FEM) with a phantom-node method for 2D linear elastic fracture mechanics. In the standard phantom-node method, the cracks are formulated by adding phantom nodes, and the cracked element is replaced by two new superimposed elements. This approach is quite simple to implement into existing explicit finite element programs. The shape functions associated with discontinuous elements are similar to those of the standard finite elements, which leads to certain simplification with implementing in the existing codes. The phantom-node method allows modeling discontinuities at an arbitrary location in the mesh. The ES-FEM model owns a close-to-exact stiffness that is much softer than lower-order finite element methods (FEM). Taking advantage of both the ES-FEM and the phantom-node method, we introduce an edge-based strain smoothing technique for the phantom-node method. Numerical results show that the proposed method achieves high accuracy compared with the extended finite element method (XFEM) and other reference solutions.

We investigated a conical crack formed near a fastening bolt of a concrete railway sleeper in a slab track system. The crack initiated from the bottom of the sleeper and penetrated the sleeper completely forming a conical shape. To study the reason for this and to examine the failure mechanism, we used a three dimensional finite element method and a series of experimental programs. The result of the numerical simulation was verified with the experimental data. From this study, we concluded that the conical crack was caused by the volume expansion of the freezing water leaking into the plastic insert of the fastener hole. The effect of location of the frozen insert holes, initial fastening force and compressive strength of concrete on the freezing force was also studied in this study.

A hybrid floating structure system combined with pontoon and semi-submersible type modules is proposed. This new system can reduce tensile forces of bottom slabs which could cause fatal damage of concrete floating structures. We performed a parametric study on the dimensions of this new system and investigate the sensitivity of the parameters to the behavior. In order to investigate various cases efficiently, we developed a simple two-step static analysis method for the fluid-structure interaction. An optimum system is derived from the investigation of the analysis results, weights and drafts of the hybrid structure. This study shows that introducing this new system to concrete floating structures is an effective way to reduce the tensile force of the bottm slab of such a floating structure. Also, it was found that when the length of the semi-submersible module is about 15%, the behavior would be optimal in the considered case.

We present an extended finite element formulation for dynamic fracture of piezo-electric materials. The method is developed in the context of linear elastic fracture mechanics. It is applied to mode I and mixed mode-fracture for quasi-steady cracks. An implicit time integration scheme is exploited. The results are compared to results obtained with the boundary element method and show excellent agreement.

Fatigue life in critical parts of structure components, which is subjected to variable amplitude loading, is a very complex subject. When a fatigue life is influenced by these load variations, accelerations and/or retardations in crack growth rate can occur. Thus, an accurate prediction of fatigue life requires an adequate evaluation of these stress interaction effects. There are many different indexes for calculating fatigue damage at critical locations. The crack severity index based on crack growth is one of the methodologies implemented for modern military aircrafts to define mission severity relative to a known reference usage. But, this index cannot consider stress interaction. In this study, a novel index was proposed to evaluate an effect for stress interaction by using entropy concept, and fatigue life prediction methodology was developed by using entropy index of stress interaction and crack severity index of effective stress.

Finite element analysis was undertaken to investigate the effect of freezing force of water unexpectedly penetrated into inserts used in railway sleeper on pullout capacity of anchor bolts for fixing base-plate onto concrete sleeper. Based on the in-situ investigation and measurement of geometry of railway sleeper and rail-fastener, the railway sleeper was modeled by 3D solid elements. Nonlinear and fracture properties for the finite element model were assumed according to CEB-FIP 1990 model code. And the pullout maximum load of anchor bolt obtained from the model developed was compared with experimental pullout maximum load presented by KRRI for verification of the model. Using this model, the effect of position of anchor bolt, amount of fastening force applied to the anchor bolt, and compressive strength of concrete on pull-out capacity of anchor bolts installed in railway sleeper was investigated. As a result, it is found that concrete railway sleepers could be damaged by the pressure due to freezing of water penetrated into inserts. And the pullout capacity of anchor bolt close to center of railway is slightly greater than that of the others.

The strain capacity of pipelines is one of the primary factors for the design of those made of high-strength and hightoughness steel. The work presented in this paper describes the evaluation method for the compressive-bending plastic buckling capacity of pipeline steel tube based on strain-based design. The evaluation method developed in this paper used Gurson-Tvergaard -Needleman(GTN) model which is the constitutive model of the steel by user-material subroutine (UMAT) for the commercial software of ABAQUS. The model parameters were decided by comparison between experiment and simulated data. The compressive-bending experimental results are simulated using this evaluation method by means of the maximum bending moment as well as the critical compressive strain. Using this method, we simulated compressive-bending plastic buckling behavior of pipeline steel tube for the practical design in the hazardous region.

This paper develops a phantom-node method for MITC 3-node shell element. According to the phantomnode method, overlapping paired elements are used to represent an element cut through by a crack. In which, each element is created by extending a part of the cracked element to a phantom domain until it becomes a completely standard finite element. As a result, separate assumption for transverse shear strain of the MITC 3-node element to remove “shear locking” is employed straightforwardly. The development describes the crack in both thin and thick shell structures and is no need to remesh as the crack propagates. The method is applied to numerically simulate a fracture test of an internally pressurized cylindrical shell conducted by (Keesecker et al. 2003). Material constitutive law follows the J2-plasticity with linear isotropic hardening and the small strain assumption. The crack tip opening angle (CTOA) criterion, one of the fracture criteria, characterizes the crack growth condition. A predicted crack growth curve of pressure versus half-crack length is comparable to experimental measurements and other numerical results.

The strain change of a seven-wire strand is experimentally investigated for two different detensioning procedures of a pretensioned concrete bar: flame-cutting and hydraulic-jacking. Based on the results of strain changes, it is confirmed that the prestressing force was stepwise transferred to concrete for several seconds according to the individual cut of different wires in the flame-cutting procedure. In the hydraulic-jacking procedure, the detensioning was smoothly accomplished in a time of about one second shorter than that of flame-cutting. It seems that the pattern of strain changes during the detensioning procedure is more important than the elapsed time for detensioning. In addition, the drop in the strain of each wire at the moment of flame-cutting was reduced by the installation of the debonded region. Moreover, the test results showed that the placing of stirrups has an insignificant effect on the strain change. In particular, the initial prestressing force was estimated simply from the elastic recovering strain of the strand after detensioning. The prestressing force obtained from the procedure was very close to that obtained from a load cell.

A new robust and efficient approach for modeling discrete cracks in meshfree methods is described. The method is motivated by the cracking-particle method (Rabczuk T., Belytschko T., International Journal for Numerical Methods in Engineering, 2004) where the crack is modeled by a set of cracked segments. However, in contrast to the above mentioned paper, we do not introduce additional unknowns in the variational formulation to capture the displacement discontinuity. Instead, the crack is modeled by splitting particles located on opposite sides of the associated crack segments and we make use of the visibility method in order to describe the crack kinematics. We apply this method to several two- and three-dimensional problems in statics and dynamics and show through several numerical examples that the method does not show any “mesh” orientation bias.

Investigated was the fatigue behavior of the foam-filled GFRP bridge deck in the transverse direction which is an intermediate type between the modular type deck and the sandwich type. Four different types of the specimens were prepared and tested with different stress ratios. The failure mode and the change in stiffness by the foam inside the deck was reported. The role of the foam was very clear. It reduced the damage accumulation in the web-flange joint efficiently. Compared to the reference case which was not filled, the endurance of limit of the foam-filled deck was remarkably increased.

Fracture of prestressed concrete beams is studied with a novel and robust three-dimensional meshfree method. The meshfree method describes the crack as a set of cohesive crack segments and avoids the representation of the crack surface. It is ideally suited for a large number of cracks. The crack is modeled by splitting particles into two particles on opposite sides of the crack segment and the shape functions of neighboring particles are modified in a way the discontinuous displacement field is captured appropriately. A simple, robust and efficient way to determine, on which side adjacent particles of the corresponding crack segment lies, is proposed. We will show that the method does not show any "mesh" orientation bias and captures complicated failure patterns of experimental data well.

A three-dimensional meshfree method for modeling arbitrary crack initiation and crack growth in reinforced concrete structure is presented. This meshfree method is based on a partition of unity concept and formulated for geometrically non-linear problems. The crack kinematics are obtained by enriching the solution space in order to capture the correct crack kinematics. A cohesive zone model is used after crack initiation. The reinforcement modeled by truss or beam elements is connected by a bond model to the concrete. We applied the method to model the fracture of several reinforced concrete structures and compared the results to experimental data.

The static behavior of a modular bridge deck filled with a low-density polyurethane foam was experimentally investigated. The web-flange joint of the deck was strong enough so that a failure of the deck in the transverse direction was governed by the delamination of the bond between two adjacent modules whether the deck was filled or not. Although the elastic modulus of the foam was only a thousandth of the homogenized modulus of the GFRP deck, the structural performance of the deck in the transverse direction was significantly improved by the foam filled inside the deck. It was shown experimentally that tensile stress could develop in the top flange of the deck subjected to three point bending because of shear deformation. Such a development of tensile stress was significantly mitigated by the foam filled inside the deck.