• Smart Structures and Systems
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• v.30 no.1
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• pp.35-47
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• 2022

Data-driven engineering is crucial for information delivery between design, fabrication, assembly, and maintenance of prefabricated structures. Design for manufacturing and assembly (DfMA) is a critical methodology for prefabricated bridge structures. In this study, a novel concept of digital engineering model that combined existing knowledge of DfMA with object-oriented parametric modeling technologies was developed. Three-dimensional (3D) geometry models and their data models for each phase of a construction project were defined for information delivery. Digital design models were used for conceptual design, including aesthetic consideration and possible variation during fabrication and assembly. The seismic performance of a bridge pier was evaluated by linking the design parameters to the calculated moment-curvature curves. Control parameters were selected to consider the tolerance control and revision of the digital models. Digitalized fabrication of the prefabricated members was realized using the digital fabrication model with G-code for a concrete printer or a robot. The fabrication error was evaluated and the design digital models were updated. The revised fabrication models were used in the preassembly simulation to guarantee constructability. For the maintenance of the bridge, the as-built information was defined for the prefabricated bridge piers. The results of this process revealed that data-driven information delivery is crucial for lifecycle management of prefabricated bridge piers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.881-891
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• 2008

The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DIANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.

• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.333-346
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• 2023

This paper presents findings from an experimental study that was focused on evaluating the use of Forta-Ferro (FF) and Polyvinyl Alcohol (PVA) fibers on the response of moderate and special ductility beams under load cycles. For this reason, eight full-scale specimens, identical in geometry, were subjected to gradual cyclic loading. The specimens included two plain concrete beams with medium and special ductility, three beams with medium ductility and stirrup spacing of one-quarter the effective depth (d/4) and three beams with special ductility, and stirrup spacing of one-half the effective depth (d/2), strengthened with FF and PVA fibers separately. The use of fibers was aimed at reducing the amount of shear reinforcement in flexural members. Here, the variation of parameters including the maximum strength, ultimate strength, stiffness, ductility, damage index, energy dissipation, and equivalent damping was studied. Utilizing FF and PVA fibers improved the performance in beams with moderate ductility when compared to those beams with special ductility. Therefore, in special ductility beams, fibers can be used instead of crossties and in moderate ductility beams, fibers can be added to reduce the ratio of shear reinforcement. Furthermore, increasing the stirrup spacing in the moderate ductility beams from d/4 to d/2 and adding 0.6% FF or 1.5% PVA fibers resulted in behavior similar to those of the moderate ductility beam.

• Steel and Composite Structures
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• v.45 no.2
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• pp.249-261
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• 2022

This paper presents a numerical study to develop a guideline for estimating the plastic strength of elliptical steel slit damper with reasonable accuracy. The strut width increases from middle to end in elliptical steel slit damper and it is observed from the past studies that variation of the width is not considered for calculating the plastic strength of the damper. It is also noticed that the existing formulas for predicting plastic strength of this kind of damper may not be accurate and further refinement is warranted. Study is then carried on elliptical steel slit damper made of mild steel and having different geometry to find out equivalency of it with oblong steel slit damper having similar plastic strength. A few three-dimensional finite element models of seismic moment connection system with steel slit damper are developed and validated against past experiments for carrying the present study considering both the material nonlinearity as well as geometric nonlinearity. The results of the parametric studies have been compared with energy quantities and presented graphically to better understand the effects of different parameters on the system. Based on the pattern of parametric study results, closed-form semi-empirical algebraic expression of damper plastic strength is developed for elliptical steel slit damper which shows very good agreement with finite element analysis as well as experiments. This developed expression can now be used for elliptical steel slit damper in replacement with any type of damper in the design of moment connection.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.149-163
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• 2023

This paper presents stability evaluation of unlined tunnels with semi-circular arch and straight sides (SASS) driven in non-homogeneous and anisotropic undrained clay. Numerical analysis has been conducted based on lower bound finite element limit analysis with second order cone programming under plane strain condition. The solutions will be used for the assessment of stability of unlined semi-circular arch tunnels and tunnels in which semi-circular roof is supported over rectangular/square sections. The stability charts have been generated in terms of a non-dimensional factor considering linear variation in undrained anisotropic strength for normally consolidated and lightly over consolidated clay with depth, and constant undrained anisotropic strength for heavily over-consolidated clay across the depth. The effect of normalized surcharge pressure on ground surface, non-homogeneity and anisotropy of clay, tunnel cover to width ratio and height to width ratio of tunnel on the stability factor and associated zone of shear failure at yielding have been examined and discussed. The geometry of tunnel in terms of shape and size, and non-homogeneity and anisotropy in undrained strength of clay has been observed to influence significantly the stability of unlined SASS tunnels.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.255-267
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• 2004

This study was conducted in order to improvement of fishing gear and fishing operating system for anchovy boat seine by bag net A-type and B-type was attached with half size modified nets. Field experiments were carried out observe geometry of nets by catcher boats. The obtained results are summarized as follows : The actual ratio of net opening in each part of the half size modified nets was increased from fore part to back part of the nets as shown the smallest value about 20% in wing net and the biggest value about 110% in bag net. In addition, vertical net opening of B-type net as measured as 10.9~11.8m in fore bag net and 5.8~8.0m in after bag net were 1~2m greater than 9.0~13.6m of A-type one, and 2~3m less than 9.3~10.4m of A-type one, respectively. Vertical net opening of half size modified net was shown as less variation of towing depth from wing net to inside wing net than those of traditional nets due to stable vertical performance. The mesh distortion or drift and variation of vertical net opening were decreased by improvement of bag nets in order to minimized shape of net pocket phenomenon whenever towing speed is slow. Bag net B-Type attached with dual flapper was shown as less variation in width of bag net and less escapement of anchovy.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.393-400
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• 2011

The mass transport is very complicated at the area which has the macro tide and complex geometry such as Gyeonggi bay. Especially, the long period current has a strong influence on the estuarine ecosystem and the long-term distribution of substances. The long period current is caused by several external forcing, whose unique characteristic varies spatially and temporally. The variation characteristics of long period current is analysed and its generation mechanism is studied. The tidal nonlinear constituents such as overtide and compound tide are generated due to nonlinear interaction and it causes mean sea level setup. The tidal wave propagating up into estuary is transformed rapidly by decrease of cross-sectional area and depth. Therefore the mean sea level is getting rise toward upriver. The high and low tide level is similar between down-river(Incheon) and up-river(Ganghwa) during neap tide when the tidal deformation is decreased. The tidal phase difference between two tidal stations causes a periodic fluctuation of sea level difference. The low water level of Ganghwa station during spring tide does not descend under EL(-)2.5 m, but the low water level of Incheon fall down under EL(-)4.0 m. The variation of tidal range and its sea level are increased during spring tide. It is found that the long period current $M_{sf}$ is quite similar to that of sea level difference between the two tidal stations. It means that the sea surface inclination caused by the spatial difference of tidal deformation is important forcing for the generation of long period current.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.1-13
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• 2009

A study for the nonlinear solution strategies to predict the ultimate behavior of a curved PSC cable-stayed bridge with complex geometry and highly nonlinear characteristics is presented. The load and displacement control strategies are used and found to be stable for the nonlinear solution of the PSC bridge up to the moderately excessive load. The ultimate analysis of curved PSC cable-stayed bridge using these solution strategies is not converged due to the propagation of the cracks in the wide range of the concrete elements and excessive variation of the stresses in the concrete elements and cables according to the complex geometry. The load control strategy using scale-down of the unbalanced loads is proposed as an alternative method for the case that the solution is not converged due to the severe nonlinearities involved in the PSC structures like a curved PSC cable-stayed bridge. Through the ultimate analysis of the PSC girder, the accuracy and the stability of the proposed solution strategies are evaluated. Finally, the numerical results for the ultimate analysis of the curved PSC cable-stayed bridge using scale-down of the unbalanced loads are compared with those obtained from other investigator. The validity of the proposed nonlinear solution strategy is demonstrated fairly well.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.659-672
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• 1997

Thermal response induced from nonlinear temperature distribution in composite box gilder bridges depends on several variables(environmental conditions, physical and material properties, location and orientation of bridge, and cross-section geometry). In this paper, parametric study are conducted in order to find the effects of variations of seasons, location and orientation of bridge, sectional geometry and some material properties on the axial deformation, curvature and stresses in composite box girder bridge. A two-dimensional transient finite element model to conduct this parametric studies is briefly presented. Firstly, the effects of the parameters on the diurnal variation of curvature are considered, and for the time of maximum curvature, on the distribution of temperature and stresses of composite box girder sectional are considered. Finally, some considerations about the influence of the parameters on the daily maximum values of axial deformation, curvature and stresses are carried out. The influence of thermal effect on structures is important as much as the influence of live or dead load in some cases. In the design of steel composite bridges, the thermal stresses calculated on the supposition that the temperature difference between the concrete slab and steel girder is $10^{\circ}C$ and the temperature distributions are uniform in concrete slab and steel girder can be underestimated.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.10 no.2
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• pp.63-71
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• 1992

The digital map database is often produced for multiple purposes, including mapping at multiple scales; it is increasingly rare that a base map is digitized for mapping at a single scale. The most important problems in process of line simplification in map generalization and multiple representation is that tolerance value selected for simplifying base map information must be modified as feature geometry varies within the digital file to ensure both accuracy and recognizability of graphic details on a generalized map. In this study, we explored various algorithms regarding to line simplication at many scales from a single digital file, and presents a rule by which to determine those scale at which line feature geometry might be expected to change in map representation. By applying two measured of displacement between a digitized line and its simplification, five algorithms have been evaluated. The results indicate that, of the five, the Douglas-Peucker routine produced less displacement between a line and its simplification. The research has proved to automating map simplification, incorporating numeric guidelines into digital environment about what magnitude and variation in geometric detail should be preserved as the digital data is simplified for representation at reduced map scales.