• Steel and Composite Structures
• /
• v.17 no.4
• /
• pp.371-386
• /
• 2014

This paper presents a tri-linear restoring force model based on the test results of 12 circular RC columns strengthened by CFRP strips under low cyclic loading. The pre-stress of CFRP strips and axial load ratio of specimens are considered as the affect parameters of the proposed model. All essential characteristics of the hysteretic behavior of the proposed model, including the hysteretic rules, main performance points, strength degradation, stiffness degradation and confinement effects are explicitly analyzed. The calculated results from the proposed model are in good agreement with the experimental results, which shows that the recommended model can be reliably used for seismic behavior predictions of circular RC columns strengthened by pre-stressed CFRP strips.

• Structural Engineering and Mechanics
• /
• v.52 no.4
• /
• pp.767-786
• /
• 2014

This paper presents the design of reinforced concrete circular footings subjected to axial load and bending in two directions using a new model. The new model considers the soil real pressure acting on contact surface of the circular footings and these are different, with a linear variation in the contact area, these pressures are presented in terms of the axial load, moments around the axis "X" and the axis "Y". The classical model takes into account only the maximum pressure of the soil for design of footings and it is considered uniform at all points of contact area. Also, a comparison is presented in terms of the materials used (steel and concrete) between the two models shown in table, being greater the classical model with respect the new model. Therefore, the new model is the most appropriate, since it is more economic and also is adjusted to real conditions.

• Steel and Composite Structures
• /
• v.23 no.2
• /
• pp.229-238
• /
• 2017

This paper presents a combined numerical and theoretical study on the composite action between steel and concrete of circular steel tube confined concrete (STCC) stub columns under axial compressive loading with a full theoretical elasto-plastic model and finite element (FE) model in comparison with experimental results. Based on continuum mechanics, the elasto-plastic model for STCC stub columns was established and the analysis was realized by a FORTRAN program and the three dimensional FE model was developed using ABAQUS. The steel ratio of the circular STCC columns were defined in range of 0.5% to 2% to analyze the composite action between steel tube and concrete, and make a further study on the advantages of the circular STCC columns. By comparing the results using the elasto-plastic methods with the parametric analysis result of FE model, the appropriate friction coefficient between the steel tube and core concrete was defined as 0.4 to 0.6. Based on ultimate balance theory, the formula of ultimate load capacity applying to the circular STCC stub columns was developed.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.3 s.21
• /
• pp.87-92
• /
• 2006

This paper is a study on the experiment and elasto-plastic discrete limit analysis of reinforced concrete circular cylindrical shell by the rigid-bodies spring model. In the rigid bodies-spring model, each collapsed part or piece of structures at the limiting state of loading is assumed to behave like rigid bodies. The present author propose new discrete elements for elasto-plastic analysis of cylindrical shell structures, that is, a rectangular-shaped cylindrical element and a rhombus-shaped cylindrical element for the improvement and expansion of this rigid-bodies spring model. In this study, it is proposed how this rigid element-bodies spring model can be applied to the elasto-plastic discrete limit analysis of cylindrical shell structures. Some numerical results of elasto-plastic discrete limit analysis and experimental results such as the curve of load-displacement and the yielding and fracturing pattern of circular cylindrical shell under horizontal load are shown.

• Steel and Composite Structures
• /
• v.22 no.3
• /
• pp.497-520
• /
• 2016

The confined concrete stress-strain curves utilised in computational models of concrete-filled steel tubular (CFST) columns can have a significant influence on the accuracy of the predicted behaviour. A generic model is proposed for predicting the stress-strain behaviour of confined concrete in short circular, elliptical and octagonal CFST columns subjected to axial compression. The finite element (FE) analysis is carried out to simulate the concrete confining pressure in short circular, elliptical and octagonal CFST columns. The concrete confining pressure relies on the geometric and material parameters of CFST columns. The post-peak behaviour of the concrete stress-strain curve is determined using independent existing experimental results. The strength reduction factor is derived for predicting the descending part of the confined concrete behaviour. The fibre element model is developed for the analysis of circular, elliptical and octagonal CFST short columns under axial loading. The FE model and fibre element model accounting for the proposed concrete confined model is verified by comparing the computed results with experimental results. The ultimate axial strengths and complete axial load-strain curves obtained from the FE model and fibre element model agree reasonably well with experimental results. Parametric studies have been carried out to examine the effects of important parameters on the compressive behaviour of short circular, elliptical and octagonal CFST columns. The design model proposed by Liang and Fragomeni (2009) for short circular, elliptical and octagonal CFST columns is validated by comparing the predicted results with experimental results.

• Journal of The Korean Association For Science Education
• /
• v.28 no.4
• /
• pp.302-315
• /
• 2008

Circular motion has been one of the most difficult concepts for students to understand. To facilitate for students to form scientific mental models about circular motion, this study developed 4M learning cycle teaching model based on the integrated mental model theory and strategies. For this study, fifty-three eleventh graders at a technical high school in Inchon were taught for 3 class hours. We conducted tests of basic physics concept and mental model of circular motion before, after, and two months after instruction. In results, we found that there were statistically significant improvement in the test of basic physics concept and mental model related with circular motion after instruction. Especially, this teaching model affected learning effectiveness of Correctness and Coherence of mental model.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1998.03a
• /
• pp.187-194
• /
• 1998

• Korean Journal of Organic Agriculture
• /
• v.11 no.2
• /
• pp.1-21
• /
• 2003

Customary agriculture seeks to increase production and supply people with safe foods. Thus. the promotion and establishment of organic agriculture are required to reduce water and soil pollution caused by customary agriculture. Although organic agriculture is an agricultural technology system whose basic principle is organic water circulation in agronomic agriculture and livestock industry. the livestock raising sector has not been developed in Korean organic agriculture: hence the limited development of agronomic agriculture. This study therefore sought to develop a standardized model connected with organic livestock raising and organic agronomic agriculture to secure symmetric and continued development. Specifically, this study reviewed the technological and economic problems related to the development of a naturally circular standard model where organic agronomic agriculture and organic livestock raising are connected. Likewise, a model for calculating the appropriate quantity of fertilizers to be applied and appropriate number of livestock to be bred was proposed as important factors in the development of a regionally circular agriculture model, and an alternative to a system connecting the two factors suggested.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1522-1525
• /
• 2007

Circular milling operations are used to enlarge die and cylinder bores, and machine airframe pockets. In this case, cutting force varies as cutting tool position relative to workpiece. This paper presents a mechanistic model of geometric uncut chip thickness by predicting time varying cutter-part intersection as the cutter travels along the circular path. Compared with experimental results, the suggested cutting force model shows a good agreement.

• The Korean Journal of Applied Statistics
• /
• v.25 no.4
• /
• pp.651-659
• /
• 2012

In this paper we developed a statistical model for circular data with noises. In this case, model fitting by single circular model has a lack-of-fit problem. To overcome this problem, we consider some mixture models that include circular uniform distribution and apply an EM algorithm to estimate the parameters. Both von Mises and Wrapped skew normal distributions are considered in this paper. Simulation studies are executed to assess the suggested EM algorithms. Finally, we applied the suggested method to fit 2008 EHFRS(Epidemic Hemorrhagic Fever with Renal Syndrome) data provided by the KCDC(Korea Centers for Disease Control and Prevention).