• Geomechanics and Engineering
• /
• v.33 no.1
• /
• pp.29-40
• /
• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.

• Journal of the Korea Society for Simulation
• /
• v.19 no.3
• /
• pp.127-135
• /
• 2010

Modern marine navigation requires officers on the bridge to monitor a torrent of data on both the insides and outsides of the ship from numerous useful devices. But despite these tools, navigators can still find it difficult to make a safe decision for two reasons: one is that too much data if provided too quickly tends to cause fatigue and overwhelm the officer, and the other is that any inconsistency across data from several different types of devices can lead to confusion. Indeed, the fact remains that the many marine accidents can be attributed to human error, and hence there is a strong need for decision-support tools for marine navigation. One technique of providing decision support is through the use of simulation to evaluate or predict system dynamics over time using an accurate model. This paper, as a simulation method for risk prediction for a navigation safety information system of ship, suggests a navigation prediction simulation system using various knowledge bases and discrete event simulation methodology, and supports the validity of the system through the examples of components in a restricted navigation situation scenario.

• Korea Science and Art Forum
• /
• v.19
• /
• pp.601-612
• /
• 2015

Postmodernism has blurred the line between design and art. We would like to suggest a design case that took diversity in the modern era that harmonizes functionality and shape of the top board of a furniture and trend of the role of furniture and objet into consideration. This study aims to project a new role into space via convergence of objet that has aesthetic function and furniture design that plays practical role in space. Thus, furniture design attempts to combine ceramic and carpentry and demonstrate the value and potential the combination possesses. By creating a distinct design from previous furniture that had visual limitations with ceramic bridge that adopted existing piling method in ceramic design, we expect a fresh blend of furniture and space that encompasses a different sensation from color and texture of soil and glaze, unable to attain from simple wood.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.5A
• /
• pp.503-510
• /
• 2009

Latex modified concrete (LMC) is a successful polymer-portland cement concretes, which have been developed and used for many years, in overlaying bridge decks and resurfacing industrial floors. The excellent bond strength to substrate, easy application and high resistance to impact, abrasion, wear, aggressive chemicals and freeze-thaw deterioration have made this material used widely. The objective of this study was to determine experimentally the load-deflection response and ultimate strength of reinforced RC beams. The cracking patterns and the mode of failure were observed. Because of excellent bond strength and repairing effects, the RC beams repaired by LMC at compression or tension zone showed over 100% recovery from damaged structures. The RC beams overlaid by LMC showed significant improvement at load carrying capacity as overlay thickness increases. However, the beams repaired of tension zone without shear stirrups almost showed no strengthen effect, and indicated an interfacial failures. The interfacial behavior was estimated by numerical method adopting the concept of shear flow.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.2A
• /
• pp.113-120
• /
• 2010

The use of Concrete filled circular hollow steel section (CFCHS) members in bridge design is a relatively new concept. The most important part of the design and durability of such structures is the design and the construction of the joints. In the design of recently constructed steel-concrete composite bridges using CFCHS truss girders for the main load carrying structure, the fatigue verification of the tubular spatial truss joints was a main issue. Welded CFCHS joints are very sensitive to fatigue because the geometric discontinuities of the welds lead to a high stress concentration. New research done on the fatigue behaviour of such joints has focused on CFCHS N-joints, directly welded, with finite element analysis method. A commercial software, ABAQUS, is adopted to perform the finite element analysis on the N-joints. This paper is main focused on these topics, including hot spot stress.

• Smart Structures and Systems
• /
• v.31 no.3
• /
• pp.247-257
• /
• 2023

In structural health monitoring of large-scale structures, optimal sensor placement plays an important role because of the high cost of sensors and their supporting instruments, as well as the burden of data transmission and storage. In this study, a vibration sensor placement algorithm based on deep reinforcement learning (DRL) is proposed, which can effectively solve non-convex, high-dimensional, and discrete combinatorial sensor placement optimization problems. An objective function is constructed to estimate the quality of a specific vibration sensor placement scheme according to the modal assurance criterion (MAC). Using this objective function, a DRL-based algorithm is presented to determine the optimal vibration sensor placement scheme. Subsequently, we transform the sensor optimal placement process into a Markov decision process and employ a DRL-based optimization algorithm to maximize the objective function for optimal sensor placement. To illustrate the applicability of the proposed method, two examples are presented: a 10-story braced frame and a sea-crossing bridge model. A comparison study is also performed with a genetic algorithm and particle swarm algorithm. The proposed DRL-based algorithm can effectively solve the discrete combinatorial optimization problem for vibration sensor placements and can produce superior performance compared with the other two existing methods.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3A
• /
• pp.485-496
• /
• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, three load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.2 s.54
• /
• pp.122-128
• /
• 2009

This study is to improve constructability of LB-DECK construction in site such as inconvenience of main and distribution bars in arrangements LB-DECK Panel which is work is applied to many bridges these days as a permanent formwork. So, the constructability is improved by changing the method of allocation of main reinforcing bar and distribution bar which is reviewed for improving efficiency of design and construction process among the suggested methods. The crack shapes, deflections, and strains under static load of the improvement of LB-DECK Panel are compared and analyzed to former LB-DECK Panel. As a result, 13% of strength compared to before the improvement of LB-DECK Panel, and 10% of strength is increased in the case of slab.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.11
• /
• pp.111-119
• /
• 2019

The high-speed railway system is mainly composed of tunnel, bridge, and viaduct to meet the straightness needed for keeping the high speed up to 400 km/s. Seismic fragility for the high-speed railway infrastructure can be assessed as two ways: one way is studying each element of infrastructure analytically or numerically, but it requires lots of research efforts due to wide range of railway system. On the other hand, empirical method can be used to access the fragility of an entire system efficiently, which requires case history data. In this study, we collect the 2004 M_W 6.6 Niigata earthquake case history data to develop empirical seismic fragility function for a railway system. Five types of intensity measures (IMs) and damage levels are assigned to all segments of target system for which the unit length is 200 m. From statistical analysis, probability of exceedance for a certain damage level (DL) is calculated as a function of IM. For those probability data points, log-normal CDF is fitted using MLE method, which forms fragility function for each damage level of exceedance. Evaluating fragility functions calculated, we observe that T=3.0 spectral acceleration (SA_T3.0) is superior to other IMs, which has lower standard deviation of log-normal CDF and low error of the fit. This indicates that long-period ground motion has more impacts on railway infrastructure system such as tunnel and bridge. It is observed that when SA_T3.0 = 0.1 g, P(DL>1) = 2%, and SA_T3.0 = 0.2 g, P(DL>1) = 23.9%.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.2 no.2
• /
• pp.53-61
• /
• 2009

Purpose: This study was designed to evaluate the clinical usefulness of serial ultrasonography (USG) after arthroscopic rotator cuff repair and to assess the re-tear rate and the re-tear time according to the tear sizes and the repair method. Materials and Methods: Between January 2008 and June 2008, 52 patients were treated with arthroscopic rotator cuff repair, Of the 52 patients, 29 patients that had undergone more than six months follow-up underwent preoperative USG examinations and subsequent arthroscopic examinations. MRI and USG findings were compared with intraoperative results of arthroscopic examinations. The postoperative integrity of the rotator cuff was observed using serial USG examination performed postoperatively at two weeks, six weeks, three months, and six months. Results: Small to medium rotator cuff tear were identified in 10 patients where the double pulley suture bridge (DPSB) technique was performed; the re-tear rate was 20%. For 19 patients with large to massive rotator cuff tears, the re-tear rates was 100% for six patients who had undergone tendon to tendon (TT) repair, the re-tear rate was 50% for two patients who had undergone tendon to tendon and bone to tendon (TTBT) repair and the re-tear rate was 55% for11 patients where the DPSB technique was performed. Re-tear rates according to follow-up periods were 7% from two to six weeks, 66% from six weeks to three months and 27% from three to six months postoperatively. Conclusion: Serial USG examinations after arthroscopic rotator cuff repair were useful to assess the re-tear rate and the re-tear time. In addition, USG examination were useful for treatment planning during postoperative rehabilitation.