• Structural Engineering and Mechanics
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• v.45 no.5
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• pp.703-722
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• 2013

In this paper a study about concrete arch bridges built by lattice cantilevers is presented. Lattice cantilevers are partial structures composed of deck, arch, piers and provisional steel diagonals, organized as reticular cantilever girders, in order to build arch bridges without the use of centrings, supports or temporary towers. Characteristics of this construction methodology with its variants are explained together with their implications in the erection sequence. Partial elastic scheme method is implemented in order to find initial forces of temporary cables and a forward analysis is carried out to follow the actual sequence of construction, by extending a procedure already applied to concrete cable-stayed bridges and to arches built by the classical suspended cantilever method. A numerical application on a case-study of a concrete arch bridge is performed together with a comparison between different methodologies followed for its construction sequence. Differences between erection by lattice cantilevers and cable-stayed cantilevers, are discussed. Results can be useful for designers in conceptual design of concrete arch bridges.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.33-45
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• 2006

Cable-stayed bridges are more inherently vulnerable to wind during the erection stages than when they are already being used. Even if a bridge that is already being used is aerodynamically stable, it is prone to having aerodynamic instabilities within the design wind speed during construction. Therefore, when the bridge's designers deliberate on the method they will use in constructing the bridge, they must likewise come up with a suitable plan to ensure the stability of the bridge during its erection (e.g., conducting a wind-tunnel investigation). This paper describes the aeroelastic full-bridge model tests that were conducted to investigate the aerodynamic behavior of the bridge during erection, with emphasis on aerodynamic stability and the mitigation of the buffeting response through temporary stabilization. The aerodynamic performance of a cable -stayed bridge with a main span of 50 m was studied in its completed stage and in two erection stages, corresponding 50% and 90% completion, respectively. In the 50% erection stage tests, a balanced cantilever configuration, with wind cable and temporary support at the tower, was conducted. The system that was determined to be most effective in reducing wind action on the bridge during construction was proposed in the paper, based on the results of the comparative study that was conducted.

• The Journal of Internal Korean Medicine
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• v.22 no.3
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• pp.431-436
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• 2001

Objective : Erectile dysfunction is defined as the inability to attain and maintain penile rigidity sufficient to allow sexual intercourse. Although erectile dysfunction is usually considered a benign disorder, it has a dramatic impaction quality of life of the patient as well as their sexual partners. we carried out 2 cases of erectile dysfunction patient with cerebral infarction in past history. Method : 2 patients with erectile dysfunction were included in this study. Each patient was treated with palmigihwang-tang and acupuncture. The erection was evaluated clinically by manual palpation and estimated on a 5-point scale as no response, some enlargement, full, enlargement, erection sufficient for intercourse, and full rigidity, In addition ,each patient assessed his satisfaction with the treatment using a 3-point scale as poor, fair, or good Result : 2 cases patients with erectile dysfunction was improved full rigidity by treatment of using palmigihwang-tang and acupunction. Satisfaction with the treatment was reported Good. Conclusion : Treatment of using Palmigihwang-tang and acupuncture was highly effective at producing an erection satisfaction for vaginal intercourse.

• Wind and Structures
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• v.38 no.1
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• pp.43-58
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• 2024

To ensure the flutter stability of three-tower suspension bridges under skew wind, by using the computational procedure of 3D refined flutter analysis of long-span bridges under skew wind, in which structural nonlinearity, the static wind action(also known as the aerostatic effect) and the full-mode coupling effect etc., are fully considered, the flutter stability of a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River in completion and during the deck erection is numerically investigated under the constant uniform skew wind, and the influences of skew wind and aerostatic effects on the flutter stability of the bridge under the service and construction conditions are assessed. The results show that the flutter critical wind speeds of three-tower suspension bridge under service and construction conditions fluctuate with the increase of wind yaw angle instead of a monotonous cosine rule as the decomposition method proposed, and reach the minimum mostly in the case of skew wind. Both the skew wind and aerostatic effects significantly reduce the flutter stability of three-tower suspension bridge under the service and construction conditions, and the combined skew wind and aerostatic effects further deteriorate the flutter stability. Both the skew wind and aerostatic effects do not change the evolution of flutter stability of the bridge during the deck erection, and compared to the service condition, they lead to a greater decrease of flutter critical wind speed of the bridge during deck erection, and the influence of the combined skew wind and aerostatic effects is more prominent. Therefore, the skew wind and aerostatic effects must be considered accurately in the flutter analysis of three-tower suspension bridges.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.1-8
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• 2013

Many PE (pre-erection) blocks are supported by wooden, concrete, or steel supports when they are stocked in the outdoor areas of a shipyard. Their positions and numbers are planned on the basis of the workers' experience. Recently, many shipyards have been making PE blocks with various shapes and weight distributions because of the variety of ships and building technologies. Therefore, it is now necessary to deal with blocks that they have no experience with. We propose a method to conveniently and quickly evaluate the structural safety of PE block supports, without the need for special knowledge and technology related to structural analysis. This method can reduce the large number of man hours (MH) normally needed for the analysis. The three-dimensional grillage analysis is performed for a simplified grillage model of a PE block. For efficiency, the grillage model of the PE block is automatically built from its three-dimensional CAD model, and its weight is also automatically distributed on the grillage model. The integrated system has been comprehensively implemented to perform the grillage analysis for the reaction forces on block supports. This paper describes how to make a grillage model of a PE block and estimate the weight distribution of the block on this grillage model. These steps are verified by comparing the supports reaction forces to those of the 3D finite element analysis for the PE blocks that are provided by a shipyard.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.4
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• pp.56-71
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• 1987

Determination of navigation variables (latitude, longitude, and altitude) near the earth's surface is termed 'Terrestrial Navigation'. The quantities that are measured inertially are the total acceleration (or the integral fo this acceleration over a fixed time interval) and the total angular rate (or the integral of this angular rate over the same time interval). These measurements when suitably compensated can be manipulated to yield the navigation variables. Hence, it is essential that the initial values of position, orientation and velocity are accurately set up during the initial alignment process. Initial alignment of gimballed inertial navigation system ( GINS) is accomplished by gyrocompassing techniques. These cannot be used, in the case of strapdown inertial navigation system(SDINS), where the inertial instruments are directly strapped down to a vehicle frame. The basic objective of this paper is the development of digital method for the determination of the initial axes erection of a SDINS from vibration and sway currupted data on the launch pad.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.165-170
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• 2005

The weight of a ship depends on the size of the ship. Normal lightweight of a ship is over 10,000 tons. So it is inevitable to divide a ship into about more than hundreds of lumps. Each of lumps is called as a block in shipbuilding. The sizes of blocks are decided by a yard's facilities. Among them lifting cranes are most decisive facilities. By block's size the productivity of a yard is decided very much. So it is very important to have a proper block division during shipbuilding. This paper refers to the recent trend of block division among yards. This paper would give an idea how to decide boundaries of blocks. Block division also decides both quality of a ship and work volume of it. These days the block erection method is changed dramatically due to use sea barge mounted crane for erection of a grand ring block. This paper explains the new trend of block division in shipbuilding.

• Magazine of the Korea Concrete Institute
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• v.22 no.1
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• pp.59-64
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• 2010

• Journal of the Society of Naval Architects of Korea
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• v.56 no.6
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• pp.488-496
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• 2019

The estimation of block erection work time at a dock is one of the important factors when establishing or managing the total shipbuilding schedule. In order to predict the work time, it is a natural approach that the existing block erection data would be used to solve the problem. Generally the work time per unit is the product of coefficient value, quantity, and product value. Previously, the work time per unit is determined statistically by unit load data. However, we estimate the work time per unit through work time coefficient value from series ships using machine learning. In machine learning, the outcome depends mainly on how the training data is organized. Therefore, in this study, we use 'Feature Engineering' to determine which one should be used as features, and to check their influence on the result. In order to get the coefficient value of each block, we try to solve this problem through the Ensemble learning methods which is actively used nowadays. Among the many techniques of Ensemble learning, the final model is constructed by Stacking Ensemble techniques, consisting of the existing Ensemble models (Decision Tree, Random Forest, Gradient Boost, Square Loss Gradient Boost, XG Boost), and the accuracy is maximized by selecting three candidates among all models. Finally, the results of this study are verified by the predicted total work time for one ship among the same series.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.164-172
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• 2009

Anchors and saddles are used to have sufficient geometrical rigidity and make target configuration of main cable of suspension bridge. Neglecting the sliding effect at saddles, points at them have been idealized as fixed nodes in lots of former studies. In general, sliding effects are reported to show significant structural behaviors of main cable and cause to the different responses of bridges. During early erection steps of the suspension bridge, especially, the sliding effect occurs easily because there is large difference of cable tension between main and side span in removing set-back ropes or not applying set-back. This study presents the finite element analysis considering to cable sliding effect and shows the comparison of differences between sliding and non-sliding at election sequence. The analysis of sliding between main cables and saddles needs to obtain more realistic responses because the analysis result can represent unfavorably different responses of bridges. Moreover, the sliding analysis method and results in this study can be used to basic criteria in engineering design and construction steps.