• Computers and Concrete
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• v.27 no.3
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• pp.211-223
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• 2021

This paper presents a review of the two widespread approaches which deal with the ultimate strength design of RC slabs subjected to bending moments and torsion: The Field of Moments Method (FoMM) and the Sandwich method (SM). Special attention is paid to the ultimate strain distribution implicitly assumed when using each one of the methodologies, in particular, the yielding of the steel reinforcement. This work analyzes the initial assumption regarding ultimate strain distribution in the SM. Furthermore, this work studies the resisting moments field on which the Wood-Armer method is based, and it finds some inconsistencies. Several examples have been developed.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.77-86
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• 2013

Embankments on soft ground experience significant deformation during time-dependent consolidation settlement, as well as an initial undrained settlement. Since infinitesimal strain theory assumes no configuration change and minute strain during deformation, finite strain analysis is required for better prediction of geotechnical problems involving large strain and geometric change induced by imposed loadings. Updated Lagrangian formulation is developed for time-dependent consolidation combining both force equilibrium and mass conservation of fluid, and mechanical constitutive equation is written in Janumann stress rate. Numerical convergence during Newton's iteration in large deformation analysis is improved by Nagtegaal's approach of considering the effect of rotation in mechanical constitutive relationship. Numerical simulations are conducted to discuss numerical reliability and applicability of developed numerical code: deformation of cantilever beam, two-dimensional consolidation. The numerical results show that developed formulation can efficiently describe large deformation problems. Proposed formulation is expected to facilitate the upgrading of a numerical code based on infinitesimal strain theory to that based on finite strain analysis.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.214-221
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• 1995

In the paper, we have proposed a new method to determine the initial billet for the forged products using a function approximation in the neural network. The architecture of neural network is a three-layer neural network and the back propagation algorithm is employed to train the network. By utilizing the ability of function approximation of a neural network, an optimal billet is determined by applying the nonlinear mathematical relationship between the aspect ratios in the initial billet and the final products. The amount of incomplete filling in the die is measured by the rigid-plastic finite element method. The neural network is trained with the initial billet aspect ratios and those of the unfilled volumes. After learning, the system is able to predict the filling regions which are exactly the same or slightly different to the results of finite element simulation. This new method is applied to find the optimal billet size for the plane strain rib-web product in cold forging. This would reduce the number of finite element simulation for determining the optimal billet size of forging product, further it is usefully adapted to physical modeling for the forging design.

• Journal of Korean Port Research
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• v.14 no.3
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• pp.331-340
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• 2000

For the rational and economic design of the structural elements of ships which is built using welding, the ultimate strength analyses of the plates having initial imperfections, such as welding residual stresses and strains, are needful. The welding deformation usually relied on approximative equations or based on expert's experience. But in this paper, for the thermal elasto-plastic analysis of plates, the finite element analysis was performed, based on initial strain method. In formulating the incremental analysis, unbalanced force terns were included. In the plastic domain during the incremental process, the 2nd order terns stress increment and yield stress increment were considered, so that time increment could be controlled for a more stable solution. The ultimate strength analysis program of the plates having initial imperfections was made. The ultimate strength analysis was carried out based on the results of the welding deformations of this paper. In the ultimate strength analysis the Rayleigh-Ritz method based on the minimum potential theory was used.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.335-339
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• 2007

A jointed plain concrete pavement(JPCP) slab was tested in Incheon International Airport construction work to study the early-age property of JPCP slab. The temperature and moisture data of the concrete slab had been collected and analyzed. The setting time of the concrete was decided by using the maturity method. The initial setting time is 2 hours 40 minutes after the placement of the slab. The investigation and analysis of the slab began from the initial setting time. The strains of different locations and different depths of the slab show different variation character.

• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.185-187
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• 1998

Pseudomonas putida KCTC 2401 degrades 1,1, 2-trichloroethylene (TCE) using phenol as a cosubstrate. The initial TCE degradation rate decreased with the initial TCE concentration up to 20mg/l of TCE at $30^{\circ}C$ and pH 6.5. The initial degradation rate and total removal efficiency increased with inoculum size. The strain also degraded dichloroacetic acid, which was supposed to be a degradation by-product. Phenol monooxygenase apparently participates in the TCE degradation mechanism.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1329-1339
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• 1993

Creep tests were performed to determine the nonlinear viscoelastic properties of apples and pears with the creep experiment apparatus designed in this study. Compressive creep characteristics of fruits were tested at two kinds of storage conditions, four periods of storage and three levels of initial stress. Ten replications were made at each treatment combination. The creep behavior of the fruits could be well described by the nonlinear viscoelastic model as a function of initial stress and time. however, for each level of initial stress applied, the compressive behavior of the samples was satisfactorily represented by Burger's model. For all sample fruits, the longer the samples was stored, the higher the instantaneous elastic strain was observed, and the creep progressed at a high rate. These phenomena were even more remarkable on the fruit stored at the normal temperature storage rather than at the low temperature storage.

• Geomechanics and Engineering
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• v.16 no.1
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• pp.11-19
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• 2018

Propagation of the generalized Rayleigh waves in an elastic half-space covered by an elastic layer for different initial stress combinations and imperfect contact conditions is investigated. Three-dimensional linearized theory of elastic waves in initially stressed bodies in plane-strain state is employed, the corresponding dispersion equation is derived and an algorithm is developed for numerical solution to this equation. Numerical results on the influence of the initial stress patterns and on the influence of the contact conditions are presented and discussed. The case where the external forces are "follower forces" is considered as well. These investigations provide some theoretical foundations for the study of the near-surface waves propagating in layered mechanical systems and can be successfully used for estimation of the degree of the bonded defects between layers, fault characteristics and study of the behavior of seismic surface waves propagating under the bottom of the oceans.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.722-728
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• 2001

Applying a general coupled lateral and torsional vibration finite element model of gear pair element this paper intends to look into in detail the coupled lateral and torsional vibration characteristics in a turbo-chiller rotor bearing system, having a bull-pinion speed increasing gear. Investigations have been carried out systematically by comparing the uncoupled and coupled analyses natural vibration frequencies and their mode shapes upon varying the gear mesh stiffness, and also by comparing the strain energies of lateral and torsional vibration modes. Results have shown that some modes may have coupled lateral and torsional mode characteristics as the gear mesh stiffness increases over a certain value, and moreover that their associated dominant modes may be different from their initial modes, i.e., the dominant mode changes from an initial torsional one to a lateral one or from an initial lateral one to a torsional one.

• Transactions of Materials Processing
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• v.8 no.5
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• pp.454-464
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• 1999

A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between the deformed blank contour and the target contour shape into account. the minimization object function R is proposed. Based on the method, a computer program composed of blank design module, FE-analysis module and mesh generation module is developed. The rollback method is applied to square cup, reentrant cross section, L-shaped cup drawing process with the flange of uniform size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary blank shape after several modifications. Good agreements are recognized between the numerical results and the published experimental results for initial blank shape and thickness strain distribution. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.