• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.89-98
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• 2017

The offshore plant structure has been transported to the site by barge because it is hard to manufacture in site. When the structure was transported on the sea, offshore plant structures and connection were experienced repetitive submarine load. For this reason, it was known for that the axial force of high-strength bolted connection was declined. Therefore, in this study, high-strength bolted connection was evaluated the shear fatigue performance under longtime fatigue load during marine transport. The experimental variables were selected intial axial force, surface type, and bolt type because they ar important factors in the change of axial force of bolts. As a experimental results of considering various variables, the variation of axial force showed within 1%. Therefore, the high-strength bolted connection was verified structural safety under longtime fatigue load.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.119-127
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• 2013

In cases of wooden structure and wooden house installed on the outside, metal goods used for basic connection are usually screw bolts, strainless nails and general iron nails. As metal connections on wood are directly exposed to exterior environment, friction resistibility of nails on metal connections declines and continual defects on this are generated and maintenance for it is required. However, experiments and analyses for preparing basic data for improvement of the problems have been not conducted so far and wooden structures with defects are abandoned. Accordingly, by analyzing friction resistibility of connections by each kind of woods and metal goods, the study aims to suggest to use metal goods appropriately by kinds of woods and manufacture conditions with analysis on characteristics of resistibility of extracting nails for solving such problems and to secure basic data for establishing maintenance, repair and reinforcement plans.

• Steel and Composite Structures
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• v.9 no.4
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• pp.381-395
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• 2009

This paper presents the details of an advanced Finite Element (FE) analysis of a plane steel portal frame with semi-rigid beam-to-column connections subjected cyclic loading. In spite of several component models on cyclic behaviour of connections presented in the literature, works on numerical investigations on cyclic behaviour of full scale frames are rather scarce. This paper presents the evolution of an FE model which deals comprehensively with the issues related to cyclic behaviour of full scale steel frames using ABAQUS software. In the material modeling, combined kinematic/isotropic hardening model and isotropic hardening model along with Von Mises criteria are used. Connection non-linearity is also considered in the analysis. The bolt slip which happens in friction grip connection is modeled. The bolt load variation during loading, which is a pivotal issue in reality, has been taken care in the present model. This aspect, according to the knowledge of the authors, has been first time reported in the literature. The numerically predicted results using the methodology evolved in the present study, for the cyclic behaviour of a cantilever beam and a rigid frame, are validated with experimental results available in the literature. The moment-rotation and deflection responses of the evolved model, match well with experimental results. This proves that the methodology for evolving the steel frame and connection model presented in this paper is closer to real frame behaviour as evident from the good comparison and hence paves the way for further parametric studies on cyclic behaviour of flexibly connected frames.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.511-519
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• 2017

Multi-regional water supply system, which installed for supplying multiple water demands, is characterized by large-sized, long-distance, tree-type layout. This system is vulnerable to long-standing service interruption when a pipe breaks is occurred. In this study, a numerical method is proposed to calculate drainage time that directly affects time of service interruption. To begin with, governing equations are formulated to embed the delayed drainage effect by the friction loss, and to resolve complicated connection of pipelines, which are derived from the continuity and energy equations. The nonlinear hydraulic equations are solved by using explicit time integration method and the Newton-Raphson method. The developed model is verified by comparing the result with analytical solution. Furthermore, the model's applicability is validated by the examples of pipelines in serial, in parallel, and complex layout. Finally, the model is utilized to suggest an appropriate actions to reduce the deviation of draining time in the C transmission line of the B multi-regional water supply system.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.277-289
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• 2019

In this study, an innovative anchoring approach has been developed dealing with all relevant aspects in consideration of previous works. An ultimate pulling force calculation of anchor is presented from a geotechnical point of view. The proposed umbrella anchor focuses not only on the friction resistance capacity, but also on the axial capacity of the composite end structure and the friction capacity occurring around the wedge. Even though the theoretical background is proposed, in-situ application requires high-level mechanical design. Hence, the required parts have been carefully improved and are composed of anchor body, anchor cap, connection brackets, cutter vanes, open-close ring, support elements and grouting system. Besides, stretcher element made of aramid fabric, interior grouting system, guide tube and cable-locking apparatus are the unique parts of this design. The production and placement steps of real sized anchors are explained in detail. Experimental results of 52 pullout tests on the weak dry soils and 12 in-situ tests inside natural soil indicate that the proposed approach is conservative and its peak pullout value is directly limited by a maximum strength of anchored soil layer if other failure possibilities are eliminated. Umbrella anchor is an alternative to conventional anchor applications used in all types of soils. It not only provides time and workmanship benefits, but also a high level of economic gain and safe design.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.3
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• pp.221-230
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• 2020

In actual seawater desalination plant, the pressure loss due to frictional force of pipe is about 3~5 bar. Also, the pressure loss at pipe connection about 1~3 bar. Therefore, the total pressure loss in the pipe is expected to be about 4~8 bar, which translates into 0.111 to 0.222 kWh/㎥ of energy when converted into the Specific Energy Consumption(SEC). Reducing energy consumption is the most important factor in ensuring the economics of seawater desalination processes, but pressure loss in piping is often not considered in plant design. It is difficult to prevent pressure loss due to friction inside the pipe, but pressure loss at the pipe connection can be reduced by proper pipe design. In this study, seawater desalination plant piping analysis was performed using a commercial network program. The pressure loss and SEC for each case were calculated and compared by seawater desalination plant size.

• Structural Engineering and Mechanics
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• v.61 no.4
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• pp.527-538
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• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.43-50
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• 2008

The analysis and results of flexural behavior for steel composite beam with built-up cross-section considering bolt deformation are presented in this paper. The bolt deformation and the restrict effect due to bolt-connection and friction are considered to investigate the flexural behavior of steel composite beam. Nonlinear spring element in ABAQUS is used to consider bolt deformation, also the results are compared with those in case bolt deformations are ignored. The displacement, bending stresses and shear stresses are calculated by F.E. model, and these results are compared with the analytical value of no interaction beam, partial interaction beam and full interaction beam. As a result of analysis, the behavior of composite beam is more dependant on the composite rate than the friction of the steel. When the composite rate is more than 50%, the behavior of composite beam considering the effects of bolt deformation is similar to that of fully composite beam.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.461-468
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• 2012

P.E.B (Pre-Engineering Building) system means an economical system, which designs and uses optimal section proportion of tapered members according to the magnitude of bending moment. However, it is hard to adjust the friction type bolted joint in the joint of tapered member in the P.E.B system. End-plate connection is mainly used in this system due to that difficulty. Because P.E.B system has end-plate vertical defacts by heat welding deformation, a gap between end-plates and rafter or rib can be observed. In this study, an examination of construction stability was throughly performed and analyzed by the investigation of permissible internal force of bolts in end-plate connections under the bending moment using the end-plate's initial connection-defect (gap).

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.