• Journal of Welding and Joining
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• v.35 no.1
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• pp.55-60
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• 2017

There are many Industry Code and Standard (ICS) for Structural Integrity Assessment (SIA) on welded structure with defect. The general ICSs, such as R6, BS 7910 and API 579-1/ASME FFS-1, provide equations to determine the upper bound residual stress profiles based on collections from many literatures. However, these residual stress profiles used in the SIA cause the conservative design for welded structures. In this study, the structural integrity assessment for girth weld in pipeline has been conducted based on fracture mechanics. In addition, thermo-elastic plastic FE analysis was performed for evaluating the residual stress of girth weld in pipeline. The weight function solution is used to determine the stress intensity factor using the residual stress profile obtained by the FE analysis. This approach can account for redistribution and relaxation of residual stress as the defects grow. In order to the evaluate quantitative comparison between BS 7910 and weight function solution, structural integrity assessment determining allowable crack size on cracked pipe was performed with failure assessment diagram.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.922-927
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• 2006

There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. The advantages of fibre reinforced plastic(FRP) composites over conventional materials motivate their use in highway bridges for replacement of structures. Recently, an FRP deck has been installed on a state highway, located in New York State, as an experimental project. In this paper, a systematic approach for analysis of this FRP deck bridge is presented. Multi-step linear numerical analyses have been performed using the finite element method to study the structural behavior and the possible failure mechanism of the FRP deck-superstructure system Deck's self-weight and ply orientations at the interface between steel girders and FRP deck are considered in this study. From this research, the results of the numerical analyses were corroborated with field test results. Analytical results reveal several potential failure mechanism for the FRP deck and truss bridge system The results presented in this study may be used to propose engineering design guideline for new and replacement FRP bridge deck structure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.590-595
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• 2014

We have investigated anamorphic prism lenses with distortions of 0.3-0.5%. We designed the plastic triangular lens and confirmed the minimum resolution using MTF graphs. Also we confirmed that the SVGA optical system can realize a resolution of $864{\times}648$ 56 megapixels. A distortion of about 0.5% aberration appears in the maximum field, and a finite beam aberration of about $15{\mu}m$ is confirmed. We made a mold based on the design data and completed the prism lens through exodus molding. We confirmed the shape error (< $30{\mu}m$) and surface roughness (> 40 nm) of the three sides. We made the video-information-display prototype glasses using prism lens by measuring the performance, we determined the distortion aberration (0.3%) and SVGA resolution. Our approach will enable fabrication of a portable large-screen display device for glasses and sunglasses for the domestic market and, after 2015, for the world market.

• Computers and Concrete
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• v.33 no.4
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• pp.385-398
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• 2024

As concrete dominates the construction industry, alternatives to traditionally used steel reinforcement are being sought. This study explored the suitability of carbon fiber-reinforced polymer (CFRP) as a substitute within rigid frames, focusing on its impact on section ductility and overall structural durability against seismic events. However, current design guidelines address quasi-static loads, leaving a gap for dynamic or extreme circumstances. Our approach included multiscale simulations, parametric study, and energy dissipation analyses, drawing upon a unique adaptation of modified compression field theory. In our efforts to optimize macro and microparameters to improve yield strength, manage brittleness, and govern failure modes, we also recognized the potential of CFRP's high corrosion resistance. This characteristic of CFRP could significantly reduce the frequency of required repairs, thereby contributing to enhanced durability of the structures. The research reveals that CFRP's durability and seismic resistance are attributed to plastic joints within compressed fibers. Notably, CFRP can impart ductility to structural designs, effectively balancing its inherent brittleness, particularly when integrated with quasi-brittle materials. This research challenges the notion that designing bendable components with carbon fiber reinforcement is impractical. It shows that creating ductile bending components with CFRP in concrete is feasible despite the material's brittleness. This funding overturns conventional assumptions and opens new avenues for using CFRP in structural applications where ductility and resilience are crucial.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3C
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• pp.149-158
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• 2010

In this study, the behavior of Pile-Bent structure with varying diameters subjected to lateral loads were evaluated by a load transfer approach. An analytical method based on the beam-column model and nonlinear load transfer curve method was proposed to consider material non-linearity (elastic, yielding) and P-${\Delta}$ effect. For an effective analysis of behavior Pile-Bent structure, the bending moment and fracture lateral load of material were evaluated. And special attention was given to lateral behavior of Pile-Bent structures depending on reinforcing effect of materials and ground conditions. Based on the parametric study, it is shown that the maximum bending moment is located within a depth (plastic hinge) approximately 1~3D (D: pile diameter) below ground surface when material non-linearity and P-${\Delta}$ effect are considered. And distribution of the lateral deflections and bending moments on a pile are highly influenced by the effect of yielding. It is also found that this method considering material yielding behavior and P-${\Delta}$ effect can be effectively used to perform the preliminary design of Pile-bent structures.

• Archives of design research
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• v.18 no.3 s.61
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• pp.171-180
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• 2005

The purpose of this research is to investigate the nature of direction of the design corresponding to a human-centered design, digitalism, ecological design, and culture-oriented design which is an issue of design in the 21st century, from the design of the inside of a room. As a method of approach to this objective, first, 1 understand the form of boundary structure appearing in space, through the theoretical investigation of a boundary form. This research is trying to elicit the expression characteristic of kineticism which was introduced to the boundary form as a factor constituting space, by investigating the characteristic of kinaticism which was expressed in plastic arts and other genres. As a process of the proceeding of this investigation, It is explained the background, purpose, and method of this study in Chapter I, and look into the characteristic of the unfolding and expression of kinetic arts as well as the structure of a boundary form of space in Chapter II. In Chapter III, I divide the aspect of modern architectural space into realistic movement, relative movement, and associational movement and examine them. In Chapter IV, I investigate a case of modern space in which the three types of the characteristic of movement mentioned in Chapter Three was expressed, and analyze to what boundary structure the space was introduced. Last of all, in Chapter V, I elicit the characteristic of a boundary form of kineticism which was the result that appeared through the above analysis, and present the nature of future direction of interior.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.31-42
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• 2015

The plastic stress distribution method and the strain compatibility method are the two representative methods to calculate the P-M interaction strength of RCFT (rectangular concrete filled tube) columns. The plastic stress distribution method is approximate while the stress compatibility method should approach the exact solution if accurate constitutive relations of the materials involved are used. Recent study by the authors pointed out that, because of lack of accurate constitutive model for the concrete confined by the rectangular steel tube, no strain compatibility method according to the current structural provisions provides a satisfactory prediction of the P-M interaction strength of RCFT columns under various material combinations. An empirical constitutive model which can capture the stress-strain characteristics of the confined concrete of RCFT columns is proposed based on analyzing extensive exisitng test database. The key idea was to define the concrete crushing strain as a function of steel-to-concrete strength ratio and width-to-thickness ratio of steel tube. It was shown that the proposed model leads to more accurate and more consistent prediction of the P-M interaction strength of RCFT columns under general design conditions.

• Structural Engineering and Mechanics
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• v.37 no.4
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• pp.385-399
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• 2011

The aim of this research is to model the behaviour of recently developed high force to volume (HF2V) passive energy dissipation devices using a simple finite element (FE) model. Thus, the end result will be suitable for use in a standard FE code to enable computationally fast and efficient analysis and design. Two models are developed. First, a detailed axial model that models an experimental setup is created to validate the approach versus experimental results. Second, a computationally and geometrically simpler equivalent rotational hinge element model is presented. Both models are created in ABAQUS, a standard nonlinear FE code. The elastic, plastic and damping properties of the elements used to model the HF2V devices are based on results from a series of quasi-static force-displacement loops and velocity based tests of these HF2V devices. Comparison of the FE model results with the experimental results from a half scale steel beam-column sub-assembly are within 10% error. The rotational model matches the output of the more complex and computationally expensive axial element model. The simpler model will allow computationally efficient non-linear analysis of large structures with many degrees of freedom, while the more complex and physically accurate axial model will allow detailed analysis of joint connection architecture. Their high correlation to experimental results helps better guarantee the fidelity of the results of such investigations.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.675-680
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• 2002

Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling service have been well known problems in the petrochemical, power and nuclear industries. However, published literature and industry surveys show that similar problems have been occurring during the last 50 years. A better understanding of the causes of cracking and bulging causes is needed to improve the reliability of these pressure vessels. This study attempts to add information required for increasing the knowledge and fundamental understanding required. Typical examples of this problem are the coke drums in the delayed coking units refinery process. This case was selected for experimental work, field study and results comparison. Delayed coking units are among the refinery units that have higher economical yields. To shut down these units represents a high negative economical impact in refinery operations. Also, the maintenance costs associated with repairs are commonly very high. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. To design and operate more robust coke drums with fewer problems, an improved metallurgical understanding of the cracking and bulging mechanisms is required. A methodology that is based field experience revision and metallurgical analyses for the screening of the most important variables, and subsequent finite element analyses to verify hypotheses and to rank the variables according to their impact on the coke drum lives has been developed. This indicated approach provides useful information for increasing coke drum reliability. The results of this work not only order the most important variables according to their impact in the life of the vessels, but also permit estimation of the life spans of coke drums. In conclusion, the current work shows that coke drums may fail as a combination of thermal fatigue and other degradation mechanisms such as: corrosion at high and low temperatures, detrimental metallurgical transformations and plastic deformation. It was also found that FEA is a very valuable tool for understanding cracking and bulging mechanisms in these services and for ranking the design, fabrication, operation and maintenance variables that affect coke drum reliability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.15-25
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• 1993

In order to promote the efficient use of composite materials, effort is currently being directed at the development of design criteria for composite structures. Insofar as design against buckling is concerned, it is well known that, for metal shells, a key step is the definition of 'knockdown' factors on the elastic critical buckling stress accounting mainly for the influence of initial geometric imperfections. At present, the imperfection sensitivity of composite shells has not been explored in detail. Due to the large number of parameters influencing buckling response (considerably larger than for isotropic shells), a very large number of tests would be needed to quantify imperfection sensitivity experimentally. An alternative approach is to use validated numerical models for this task. Thus, the objective of this paper is to outline the underlying theory used in developing a composite shell element and to present results from a validation exercise and subsequently from a parametric study on axially loaded glass fibre-reinforced plastic (GFRP) curved panels using finite element modelling. Both eigenvalue and incremental analyses are performed, the latter including the effect of initial geometric imperfection shape and amplitude, and the results are used to estimate 'knockdown' factors for such panels.