• Steel and Composite Structures
• /
• v.22 no.5
• /
• pp.937-974
• /
• 2016

While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength ($f^{\prime}_c=20-110N/mm^2$), steel yield strength ($f_y=220-850N/mm^2$), width-to-thickness (B/t) ratios in the range of 15-52, as well as the length-to-width (L/B) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.

• Earthquakes and Structures
• /
• v.11 no.5
• /
• pp.741-777
• /
• 2016

A simplified approach of assessing torsionally balanced (TB) and torsionally unbalanced (TU) low-medium rise buildings of up to 30 m in height is presented in this paper for regions of low-to-moderate seismicity. The Generalised Force Method of Analysis for TB buildings which is illustrated in the early part of the paper involves calculation of the deflection profile of the building in a 2D analysis in order that a capacity diagram can be constructed to intercept with the acceleration-displacement response spectrum diagram representing seismic actions. This approach of calculation on the planar model of a building which involves applying lateral forces to the building (waiving away the need of a dynamic analysis and yet obtaining similar results) has been adapted for determining the deflection behaviour of a TU building in the later part of the paper. Another key original contribution to knowledge is taking into account the strong dependence of the torsional response behaviour of the building on the periodic properties of the applied excitations in relation to the natural periods of vibration of the building. Many of the trends presented are not reflected in provisions of major codes of practices for the seismic design of buildings. The deflection behaviour of the building in response to displacement controlled (DC) excitations is in stark contrast to behaviour in acceleration controlled (AC), or velocity controlled (VC), conditions, and is much easier to generalise. Although DC conditions are rare with buildings not exceeding 30 m in height displacement estimates based on such conditions can be taken as upper bound estimates in order that a conservative prediction of the displacement profile at the edge of a TU building can be obtained conveniently by the use of a constant amplification factor to scale results from planar analysis.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.3
• /
• pp.243-260
• /
• 2011

To predict TBM performance in design stage is indispensable for its successful application. The NTNU model, one of the representative TBM performance prediction models uses two distinct parameters such as DRI and CLI obtained from three different tests on bored rock cores. Based on DRI and CLI, it is possible to predict TBM advance rate and cutter life in the NTNU model. In this study, NTNU testing methods and their related testing equipments were introduced to measure DRl and CLI for the NTNU model. Then, in order to derive their relationships, the two key parameters measured for 39 domestic rocks were compared with physico-mechanical properties of rock such as uniaxial compressive strength and quartz content. Lastly, the experimental results were also compared with NTNU database to verify their reliability.

• Composites Research
• /
• v.28 no.5
• /
• pp.260-264
• /
• 2015

In this paper, molecular dynamics (MD) simulation was carried to predict thermo-mechanical behaviors for carbon nanotube (CNT) reinforced epoxy composites and to analyze the trends. Total of six models having the volume fractions of CNT from 0 to 25% in epoxy were constructed. To predict thermal behaviors, temperature was increased constantly from 300 to 600 K, and the glass transition temperature ($T_g$) and coefficient of thermal expansion (CTE) analyzed using the relationship between temperature and specific volume. The elastic moduli that represented to the mechanical behaviors were also predicted by constant strain. Additionally, the effects of functionalization of CNT on mechanical behaviors of composite were analyzed. Models were constructed to represent CNTs functionalized by nitrogen doping and COOH groops, and interfacial behaviors and elastic moduli were analyzed. Results showed that the agglomerations of CNTs in epoxy cause by perturbations of thermo-mechanical behaviors, and the functionalization of CNTs improved the interfacial response as well as mechanical properties.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.6
• /
• pp.488-495
• /
• 2008

In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.4
• /
• pp.611-634
• /
• 2017

In rapid urbanization, demand for utility tunnel increases more, and tunnel boring machine (TBM) has been used widely. Prediction of TBM penetration rate is important for proper estimation of construction period and cost. Although there are several methods, such as NTNU model and CSM model that require many input parameters, fundamental understanding on correlations between rock properties and TBM penetration rate is critical. In this study, we explored the brittleness indices of hard rocks according to various definitions, and the correlations between the brittleness indices and the TBM penentration rates.

• Geomechanics and Engineering
• /
• v.23 no.4
• /
• pp.327-338
• /
• 2020

The role of precise prediction of subsurface fluids and discrimination among them cannot be ignored in reservoir characterization and petroleum prospecting. A suitable rock physics model should be build for the extraction of valuable information form seismic data. The main intent of current work is to present a rock physics model to analyze the characteristics of seismic wave propagating through a cracked porous rock saturated by a three phase fluid. Furthermore, the influence on wave characteristics due to variation in saturation of water, oil and gas were also analyzed for oil and water as wet cases. With this approach the objective to explore wave attenuation and dispersion due to wave induce fluid flow (WIFF) at seismic and sub-seismic frequencies can be precisely achieved. We accomplished our proposed approach by using BISQ equations and by applying appropriate boundary conditions to incorporate heterogeneity due to saturation of three immiscible fluids forming a layered system. To authenticate the proposed methodology, we compared our results with White's mesoscopic theory and with the results obtained by using Biot's poroelastic relations. The outcomes reveals that, at low frequencies seismic wave characteristics are in good agreement with White's mesoscopic theory, however a slight increase in attenuation at seismic frequencies is because of the squirt flow. Moreover, our work crop up as a practical tool for the development of rock physical theories with the intention to identify and estimate properties of different fluids from seismic data.

• Asian-Australasian Journal of Animal Sciences
• /
• v.33 no.11
• /
• pp.1787-1796
• /
• 2020

Objective: The objective of this study was to determine the digestible energy (DE) and metabolizable energy (ME) of yellow dent corn sourced from different meteorological origins fed to growing pigs and develop equations to predict the DE and ME of yellow dent corn from southwestern China. Methods: Sixty crossbred barrows were allotted to 20 treatments in a triplicate 20×2 incomplete Latin square design with 3 replicated pigs per dietary treatment during 2 consecutive periods. Each period lasted for 12 days, and total feces and urine during the last 5 days of each period were collected to calculate the energy contents. Results: On dry matter (DM) basis, the DE and ME in 20 corn grain samples ranged from 15.38 to 16.78 MJ/kg and from 14.93 to 16.16 MJ/kg, respectively. Selected best-fit prediction equations for DE and ME (MJ/kg DM basis) for yellow dent corn (n = 16) sourced from southwestern China were as follows: DE = 28.58-(0.12×% hemicellulose)+(0.35×% ether extract)-(0.83×MJ/kg gross energy)+(0.20×% crude protein)+(0.49×% ash); ME = 30.42-(0.11×% hemicellulose)+(0.31×% ether extract)-(0.81×MJ/kg gross energy). Conclusion: Our results indicated that the chemical compositions, but not the meteorological conditions or physical characteristics could explain the variation of energy contents in yellow dent corn sourced from southwestern China fed to growing pigs.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.3 no.3
• /
• pp.1-8
• /
• 2012

Recently, underground pipes are utilized in various fields of applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. Most of pipes are installed for long-term purposes and they should be safely installed in consideration of installation conditions because there are unexpected various terrestrial loading conditions. In this paper, we present the result of investigation pertaining to the structural behavior of glass fiber reinforced thermosetting polymer plastic (GFRP) flexible pipes buried underground. The mechanical properties of the GFRP flexible pipes produced in the domestic manufacturer are determined and the results are reported in this paper. In addition, ring deflection is measured by the field tests and the finite element analysis (FEA) is also conducted to simulate the structural behavior of GFRP pipes buried underground. From the field test results, we predicted long-term, up to 50 years, ring deflection of GFRP pipes buried underground based on the method suggested by the existing literature. It was found that the GFRP flexible pipe to be used for cooling water intake system in the nuclear power plant is appropriate because 5% ring deflection limitation for 50 years could be satisfied.

• Interdisciplinary Bio Central
• /
• v.5 no.2
• /
• pp.3.1-3.7
• /
• 2013

Recently, the productivity of drug discovery has gradually decreased as the limitations of single-target-based drugs for various and complex diseases become exposed. To overcome these limitations, drug combinations have been proposed, and great efforts have been made to predict efficacious drug combinations by statistical methods using drug databases. However, previous methods which did not take into account biological networks are insufficient for elaborate predictions. Also, increased evidences to support the fact that drug effects are closely related to metabolic enzymes suggested the possibility for a new approach to the study drug combinations. Therefore, in this paper we suggest a novel approach for analyzing drug combinations using a metabolic network in a systematic manner. The influence of a drug on the metabolic network is described using the distance between the drug target and an enzyme. Target-enzyme distances are converted into influence scores, and from these scores we calculated the correlations between drugs. The result shows that the influence score derived from the targetenzyme distance reflects the mechanism of drug action onto the metabolic network properly. In an analysis of the correlation score distribution, efficacious drug combinations tended to have low correlation scores, and this tendency corresponded to the known properties of the drug combinations. These facts suggest that our approach is useful for prediction drug combinations with an advanced understanding of drug mechanisms.