• Tunnel and Underground Space
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• 제26권3호
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• pp.192-200
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• 2016

We analyzed the behavior of the lining segments considering the middle slab and lateral pressure coefficients when planning the construction of a duplex tunnel for the underground network. Reviewed segment lining analysis for research, the analytical model was determined for duplex tunnel. Also reviewed the vertical load, and a load of middle slab is considered the static load and the live load by vehicles. Section force by middle slabs a load applied was mainly generated in the lower tunnel had the greatest effect on the bending moment. In addition, the bending moment acting direction changes appeared with a large variable, and the section force according to the load applied to the middle slab is relatively constant and the effect on the segment lining from the smallest section force of the lateral pressure coefficient of 1.00 was found to occur appears most significantly. As a result of this research to identify the behavior of the slab and the segment lining by the effect of the lateral pressure coefficient (K) of the duplex tunnel will be able to present a method of the duplex tunnel structure is reasonable and economical design.

• Journal of Korean Society of Transportation
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• 제21권4호
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• pp.91-101
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• 2003

This study modeled 4-lane highway in three-dimensional virtual reality in order to overcome difficulties of field experiment. and the research subject was placed in a driving simulator. We survey the driver's cognitive characteristics to the alignment changes in the three-dimensional virtual reality highway. Especially, maximizing the identity of driving movements and virtual scenery on the basis of the data obtained by dynamic analysis module. we minimized simulator sickness for the graphic module of driving simulator. And we carried out cognitive evaluation on the basis of adjective words extracted by dictionary and the opinion of specialist. In this study LISREL model was used to detect the causal relation between geometry and safety in cognitive side, and found that geometric change affects the safety of drivers by static and dynamic road safety model in three-dimensional combined alignments. As the result, for constructing safety road. we consider drivers' cognitive characteristics as human factors in road design, and we think that they are very important factors to improve road safety.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제30권3호
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• pp.278-286
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• 2006

Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades$(\alpha)$ and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, $\alpha=60^{\circ}$ and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of $\Omega=0.33$, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed.

• Journal of the Korea institute for structural maintenance and inspection
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• 제7권4호
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• pp.191-199
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• 2003

The inelastic response of many structural steel and reinforced concrete structures subject to extreme loadings can be characterized by elastoplastic behaviors. Although excursion beyond the elastic range is usually not permitted under normal conditions of service, the extent of permanent damage a structure may sustain when subjected to extreme conditions, such as severe blast or earthquake loading, is frequently of interest to the engineer. A blast is usually the result of an explosion defined as a "sudden expansion". This paper discusses the basic concept that defines blast loadings on structures and corresponding elastoplastic structural response (displacement, velocity, and acceleration) and try to explain a crack propagation of concrete in sudden expansion. According to nonlinear finite element analysis, the crack forms of static and dynamic states displayed different in RC structural members. This paper also provides useful data for the dynamic fracture analysis of RC frame structures.

• Journal of the Korea institute for structural maintenance and inspection
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• 제13권6호통권58호
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• pp.148-155
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• 2009

A remarkable discrepancy of lateral deformation of shear wall structures for seismic loads due to a rigid diaphragm assumption without floor slab modelling asks a study how much effective the slab stiffness ratio is to the lateral behaviour. Typical shear wall type 15 stories structure is selected to analysis using MIDAS-ADS2008 commercial softwares modelling three types; 1) rigid diaphragm (RD model) 2) considered out-of plane slab flexural stiffness (DB model), and 3) considered in and out of plane slab flexural stiffness (SRC model). Based on National Code of KBC2005, the Equivalent Static and Response Spectrum seismic analysis are undertaken to compare each responses of the three models. The differences of lateral responses due to the three slab stiffness ratios applied on the models are compared and discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• 제14권1호
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• pp.165-174
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• 2010

In this paper, a two-phase structural health monitoring system using acceleration response signatures are presented to firstly alarm the change in structural condition and to secondly detect the changed location for full-scale concrete girder bridges. Firstly, Mihocheon Bridge which is a two-span continuous concrete girder bridge is selected as the target structure. The dynamic response features of Mihocheon Bridge are extracted by forced vibration test using bowling ball. Secondly, the damage alarming occurrence and the damage localization techniques are selected to design two-phase structural health monitoring system for Mihocheon Bridge. As the damage alarming techniques, auto-regressive model using time-domain signatures, correlation coefficient of frequency response function and frequency response ratio assurance criterion are selected. As the damage localization technique, modal strain energy-based damage index method is selected. Finally, the feasibility of two-phase structural health monitoring systems is evaluated from static loading tests using a dump truck.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.395-406
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• 2020

Many prefabricated concrete frame joints have been proposed, and most of them showed good seismic performance. However, there are still some limitations in the proposed fabricated joints. For example, for prefabricated prestressed concrete joints, prefabricated beams and prefabricated columns are assembled as a whole by the pre-stressed steel bar and steel strand in the beams, which brings some troubles to the construction, and the reinforcement in the core area of the joints is complex, and the mechanical mechanism is not clear. Based on the current research results, a new type of fabricated joint of prestressed concrete beams and confined concrete columns is proposed. To study the seismic performance of the joint, the quasi-static test is carried out. The test results show that the nodes exhibit good ductility and energy dissipation. According to the experimental fitting method and the "fixed point pointing" law, the resilience model of this kind of nodes is established, and compared with the experimental results, the two agree well, which can provides a certain reference for elasto-plastic seismic response analysis of this type of structure. Besides, based on the analysis of the factors affecting the shear capacity of the node core area, the formula of shear capacity of the core area of the node is proposed, and the theoretical values of the formula are consistent with the experimental value.

• Computers and Concrete
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• 제16권4호
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• pp.503-529
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• 2015

Traditionally, multi-story buildings are designed to provide stiffer structural support to withstand lateral earthquake loading. Introducing flexible elements at the base of a structure and providing sufficient damping is an alternative way to mitigate seismic hazards. These features can be achieved with a device known as an isolator. This paper covers the design of base isolators for multi-story buildings in medium-risk seismicity regions and evaluates the structural responses of such isolators. The well-known tower building for police personnel built in Dhaka, Bangladesh by the Public Works Department (PWD) has been used as a case study to justify the viability of incorporating base isolators. The objective of this research was to establish a simplified model of the building that can be effectively used for dynamic analysis, to evaluate the structural status, and to suggest an alternative option to handle the lateral seismic load. A finite element model was incorporated to understand the structural responses. Rubber-steel bearing (RSB) isolators such as Lead rubber bearing (LRB) and high damping rubber bearing (HDRB) were used in the model to insert an isolator link element in the structural base. The nonlinearities of rubber-steel bearings were considered in detail. Linear static, linear dynamic, and nonlinear dynamic analyses were performed for both fixed-based (FB) and base isolated (BI) buildings considering the earthquake accelerograms, histories, and response spectra of the geological sites. Both the time-domain and frequency-domain approaches were used for dynamic solutions. The results indicated that for existing multi-story buildings, RSB diminishes the muscular amount of structural response compared to conventional non-isolated structures. The device also allows for higher horizontal displacement and greater structural flexibility. The suggested isolation technique is able to mitigate the structural hazard under even strong earthquake vulnerability.

• Journal of the Korean Geophysical Society
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• 제9권2호
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• pp.77-86
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• 2006

Aplications of the real-time kinematic GPS surveying and inertial measurement unit have been beingRTK GPS allows the use of a static base station and remote rover unit to allow for data collectionwithin several seconds and in real time. It is useful for monitoring the behaviors of massive structureslike bridges. And this study purposed to implement a method of deciding the acurate dynaimc attitudeof structures by IMU. In this study, among GPS methods, we used RTK GPS to analyze the precisionof monitoring and then on the basis of it, we developed a monitoring system using RTK GPS anda deviation betwen observation values, X axis was 1mm, Y axis was 1mm and Z axis 2.2mm. I tturned out that it was possible to monitor and measure structures by RTK GPS and IMU.

• Journal of the Society of Naval Architects of Korea
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• 제58권2호
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• pp.84-89
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• 2021

Recently, shipyards are making many efforts to reduce the number of the mounted blocks by increasing the block size. This is to improve productivity and reduce related costs by minimizing block movement and shortening the building period. However, as the blocks become larger, the weight increases considerably. If the target block has a damage due to an unexpected accident during block lifting, it may seriously cause a problem of the reusability of the block. In this study, a large-sized block of the offshore structure weighing 480 tons was lifting with a total of seven sling belts, and one sling belt was broken while it was moving, resulting in a situation in which a part of the edge of the block collided with the ground. The aim of this paper is to verify the structural integrity of the block that directly collides with the ground in the form of free fall due to the sling breakage. Considering that the hook loads acting on several sling belts holding the block are redistributed when a sling belt is broken, the hook loads were recalculated at the angle just before the sling breakage. These loads were used to check the safety of the sling belts. In addition, FE analysis was performed by calculating the amount of impact from the free fall condition, obtaining the impact area by using Hertz's contact theory, and then applying the impact load to the area.