Importance Of 3D Effects Research Articles

Three-dimensional spreading of prestressing forces in box girders

In most applications of post-tensioning, especially for bridge girders, the cross section over which the post-tensioning acts is not rectangular. Since the design of the box girder anchorage zone is not currently addressed in any code provisions, a detailed investigation of the three-dimensional (3D) spreading of the tendon force in flanged sections is required. To accomplish this objective, a computer-based tool is developed for plotting load paths in 3D bodies, from which the flow of forces in the box-girder anchorage zone can be clearly visualized. It is found that the 33.7-degree criterion is appropriate to describe the dispersion of the tendon force in the box-girder. Meanwhile, planar strut-and-tie models are built to approximate the flow of forces in orthogonal planes of the box section. As a useful supplement to the current design codes, direct equations are established for the design of the box-girder anchorage zone. Finally, a case study is carried out to find the cause of cracking in a span-by-span constructed box-girder bridge. The large transverse tensile stress in the bottom flange is primarily caused by the post-tensioning of web tendons, indicating the importance of 3D effects in the box-girder anchorage zone.

Electrothermal and Electrochemical Modeling of Lithium-ion Batteries: 3D Simulation with Experimental Validation

This work presents two lithium-ion battery models which are implemented in the multiphysics software package FIRE®, developed by AVL List GmbH: an efficient electrothermal model based on an empirical voltage/current relationship and a physically based, non-isothermal electrochemical model. The models are applied to a 3D simulation of a high energy lithium-ion pouch battery. Both models are adjusted to measured discharge curves for various currents and temperatures. Then their results are compared and a deep insight into the electrodes is given by the electrochemical model. Here, the importance of 3D effects and temperature influence are pointed out – both effects which are often neglected in electrochemical models presented in literature. Finally, both models are compared to voltage and temperature measurements using a realistic, strongly dynamic driving profile. A highly accurate prediction of the experimental data can be achieved with both models.

Comprehensive Modeling of Superluminescent Light-Emitting Diodes

We present a self-consistent electric and optic model for superluminescent light-emitting diodes (SLED) using 3D finite-element method. The carrier transport is calculated by the drift-diffusion method, which is coupled with the radiative recombination obtained from the solution of Shrodinger-Poison equations self-consistently. The spontaneous emission noise is described by the fundamental theory using the Green's function method. Our model allows 2D treatment of the carrier dynamics and optical confinement on the transverse plane, along with the electronic and optical variation on the longitudinal axis. The theoretical model has been benchmarked with an InP-based edge-emitting SLED. The device has nonidentical quantum wells with broad bandwidth from 1300 to 1600 nm. The results show the importance of 3D effects and demonstrate the validity of the model.

Comparative Magnetotelluric Modeling of Smooth 2D and 3D Conducting Bodies Using Rayleigh-Fourier Codes

—Recently, a method for 3D magnetotelluric modeling was developed, which is based on the application of the Rayleigh scattering theory. This method, RF-3D, is especially capable of modeling multilayered structures with smooth irregular boundaries. The formulation allows inclusion of layers with vertically anisotropic electrical conductivity.¶Using RF-3D, the response of smooth structures of practical interest is calculated and the importance of 3D effects is evaluated. Two models consisting of a 3D conductive body in the presence of a 2D shallow distortion are analyzed. In the first model, the direction of maximum elongation of the body is perpendicular to the strike direction of the 2D upper structure, and in the second one both directions coincide. In addition, the case of a small 3D shallow conductor over a regional 2D structure is also considered.¶3D effects are compared to those generated by 2D models with identical cross sections. In all the cases, the 3D responses differ from those of the 2D, especially directly over the bodies. A good agreement between the 2D transverse magnetic response and the corresponding components of the 3D response, along centrally located transverse profiles, is expected for elongate, prismatic conductors. Then, the differences obtained for the models considered in this study, particularly for the second and third models, are a consequence of the smooth geometry. They can be explained in terms of galvanic effects produced by boundary charges, which are greater near the vertical sides of a prism than on the sides of a body with smooth contours.¶Equivalent 2D models of the first and second structures are also obtained. In these models, the thickness of the conductor is underestimated, respectively, by about 30% and 24%.¶For the third model, when vertical anisotropy is analyzed, it is found that only the anisotropy of the first layer can be detected. This is because the effect of vertical anisotropy decreases strongly with depth and appears to be important only near the 3D anomaly.

Charge and overpressure modelling in the North Sea: multi-dimensional modelling and uncertainty analysis

Over the past one and a half decades developments in our understanding of earth physics and the increase in computer power have enabled quantitative modelling of subsurface temperature, hydrocarbon charge, migration, overpressures and palinspastics. The North Sea has provided the test bed for many of these efforts. Initial developments focused on one dimensional models of temperature and charge as these were computationally possible at that time, and by the late 80s such models were widely available. Despite the current availability of 2D charge modelling tools, most modelling carried out at present is still ID. Hydrocarbon generation is driven by the temperature field which depends on the heat flow, which is only truly vertical in exceptional circumstances. In principle, a whole lithosphere ID model will only agree with a 3D model for a horizontally layered section. Thermal conductivity anisotropy (lateral/vertical conductivity) of mudstones can reach three. Lateral differences in geology also promote changes in geothermal gradients and therefore lateral heat movement. At the lithosphere scale, differences in the depth to the convecting asthenosphere, and the distribution of hot spots may also cause lateral heat flow. In the North Sea, the complex geology particularly within the syn-rift section makes heat flow strongly 3D. In the Inner Moray Firth and Halten Terrace there are considerable differences between the predictions of fully transient 1D and 3D models for the temperature and hydrocarbon expulsion flux histories of the kitchen areas. Differences can exceed 15°C close to major faults: kitchen areas in the hanging walls are typically cooler than would be expected from ID models, whereas basement cored highs are typically hotter than might be expected. The differences between the predictions of ID and 3D models are driven by structural effects and are thus temporally variant. The importance of 3D effects in charge modelling is compounded in hydrocarbon migration models. Temporal changes in carrier bed interconnectivity, fault seal properties and basin structure influence migration, re-migration and even refilling of breached traps. For instance, hydrocarbons found in the Tertiary of the Central North Sea are derived from underlying Jurassic reservoirs where high overpressures have lead to hydrofracturing and hence leakage. Numerical models of overpressure generation, including rapid sedimentation (under-compaction), thermal expansion (aquathermal pressuring), smectite to illite transition (water generation), etc., tell only part of the story: in order for pressures to rise the fluids have to be contained by rocks with sufficiently low permeability. Furthermore, overpressures are transient and gradually diminish when generation ceases. These processes can be described by a relatively simple differential equation, which can be solved to predict overpressures in one or more dimensions. However, in the North Sea, widespread aquifers (e.g. the Fulmar Formation sands) allow pressure transmission out of synclines. Thus, simple ID models are of limited use, and pressure modelling requires prediction of the stratigraphy and temporal variations in aquifer connectivity resulting from structural movement. Palinspastic restoration is thus a prerequisite. In areas such as the Central North Sea, where there is good pressure calibration and relatively simple stratigraphy, modelling enables prediction of overpressure, trap integrity and reservoir continuity. One problem with physical models discussed above has been their inability to incorporate uncertainties. New models are capable of taking into account uncertainties in both model parameters (e.g. compaction coefficients) and input data (e.g. stratigraphic age) to calculate the uncertainty in the modelled variable (e.g. hydrocarbon flux history). Such models provide a much more realistic evaluation of wildcat prospects. The potential of basin models for prospect evaluation and field development is still in its infancy. From a commercial view point, in areas such as the North Sea where data are readily available to most competitors there is little advantage in having the same models as everybody else. The advantage lies in being able to evaluate acreage faster and with greater accuracy, both in the prediction and the uncertainties.