• Geomechanics and Engineering
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• v.12 no.1
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• pp.139-160
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• 2017

The bearing mechanism of tunnel-type anchorage (TTA) for suspension bridges is studied. Model tests are conducted using different shapes of plug bodies, which are circular column shape and circular truncated cone shape. The results show that the plug body of the latter shape possesses much larger bearing capacity, namely 4.48 times at elastic deformation stage and 4.54 times at failure stage compared to the former shape. Numerical simulation is then conducted to understand the mechanical and structural responses of plug body and surrounding rock mass. The mechanical parameters of the surrounding rock mass are firstly back-analyzed based on the monitoring data. The calculation laws of deformation and equivalent plastic strain show that the numerical simulation results are rational and provide subsequent mechanism analysis with an established basis. Afterwards, the bearing mechanism of TTA is studied. It is concluded that the plug body of circular truncated cone shape is able to take advantage of the material strength of the surrounding rock mass, which greatly enhances its bearing capacity. The ultimate bearing capacity of TTA, therefore, is concluded to be determined by the material strength of surrounding rock mass. Finally, recommendations for TTA design are proposed and discussed.

• Advances in concrete construction
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• v.6 no.3
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• pp.245-268
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• 2018

The numerical investigations have been carried out on deep beam with opening subjected to static monotonic loading to demonstrate the accuracy and effectiveness of the finite element based numerical models. The simulations were carried out through finite element program ABAQUS/CAE and the results thus obtained were validated with the experiments available in literature. Six simply supported beams were modelled with two square openings of 200 and 250 mm sides considered as opening at centre, top and bottom of the beam. In order to define the material behaviour of concrete and reinforcing steel bar the Concrete Damaged Plasticity model and Johnson-Cook material parameters available in literature were employed. The numerical results were compared with the experiments in terms of ultimate failure load, displacement and von-Mises stresses. In addition to that, seventeen beams were simulated under static loading for studying the effect of opening location, size and shape of the opening and depth, span and shear span to depth ratio of the deep beam. In general, the numerical results accurately predicted the pattern of deformation and displacement and found in good agreement with the experiments. It was concluded that the structural response of deep beam was primarily dependent on the degree of interruption of the natural load path. An increase in opening size from 200 to 250 mm size resulted in an average shear strength reduction of 35%. The deep beams having circular openings undergo lesser deflection and thus they are preferable than square openings. An increase in depth from 500 mm to 550 mm resulted in 78% reduced deflection.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.100-109
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• 2020

Pipelines subjected to ground movement would be easily exposed to large-scale deformation. Since such deformations may cause the pipeline failure, it is important to ensure the safety of pipelines in various operation conditions. However, crack in weld metal have been considered as one of the main causes that can deteriorate the structural integrity of the pipeline. For this reason, the structural integrity of the pipe containing the crack in the weld should be obtained. In order to assess cracked pipe, J-integral and crack-tip opening displacement(CTOD) have been applied widely as the elastic-plastic fracture mechanics parameters representing crack driving force. In this study, engineering solutions to calculate the J-integral and CTOD of pipes with a circumferential outer surface crack in the weld are proposed. For this purpose, 3-dimensional elastic-plastic finite element(FE) analyses have been performed considering the effect of overmatch and width of weld. The shape of the weld was simplified to I-groove, and axial displacement was employed as for loading condition. Based on FE results, the effects of crack size, material properties and width of weldment on J-integral and CTOD were investigated. Additionally, the J-integral and CTOD for I-groove were compared with those for V-groove to examine the effects of the weld shape, and a proportionality coefficient of J-integral and CTOD was calculated from the results of this paper.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.1-10
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• 2007

A laboratory investigation is conducted to characterize and quantify fatigue lives of continuously reinforced concrete pavements (CRCP) with initial design parameters. Eight specimens scaled were made based on results of finite-element analyses and stress-strain curve comparisons. Static tests were firstly performed to obtain magnitudes of static failure loads and to predict crack patterns before fatigue tests. The fatigue lives measured in the study were compared based on each initial design parameter. The comparison indicates that the fatigue lives of CRCP specimens with initial cracks increases with increasing the initial crack spacing, and CRCP specimens with reinforcements at top of the concrete slab have more fatigue lives than those with reinforcements at midheight of the concrete slab. In addition, the fatigue lives were significantly affected by soil conditions under the CRCP specimens. The results obtained in the study can be used for maintenance and retrofit of the continuously reinforced concrete pavements.

• Journal of Korean Neurosurgical Society
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• v.42 no.4
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• pp.317-325
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• 2007

Objective : The purpose of the study was to determine the clinical effects of anterior radical debridement on a series of patients with spontaneous spinal infection. Methods : We retrospectively analyzed the clinical characteristics of 32 patients who underwent surgical treatment from January 2000 to December 2005 in our department. The average follow-up Period was 33.4 months (range, 6 to 87 months). Thirty-two patients presented with the following : 23 cases with pyogenic spondylitis, eight with tuberculous spondylitis and one with fungal spondylitis. The indications for surgery were intractable pain, failure of medical management, neurological impairment with or without an associated abscess, vertebral destruction causing spinal instability and/or segmental kyphosis. Results : The study included 15 (46.9%) males and 17 (53.1%) females ranging in age from 26 to 75 years (mean, 53.1 years). Diabetes mellitus (DM) and pulmonary Tbc were the most common predisposing factors for pyogenic spondylitis and tuberculous spondylitis. Staphylococcus aureus (13%) was the main organism isolated. The most prevalent location was the lumbar spine (75%). Changes in the pain score, Frankel's classification, and laboratory parameters demonstrated a significant clinical improvement in all patients. However, there were recurrent infections in two patients with tuberculous spondylitis and inappropriate debridement and intolerance of medication and noncompliance. Autologous rib, iliac bone and allograft(fibular) were performed in most patients. However, 10 patients were grafted using a titanium mesh cage after anterior radical debridement. There were no recurrent infections in the 10 cases using the mesh cage with radical debridement. Conclusion : The findings of this study indicate that surgery based on appropriate surgical indications is effective for the control of spinal infection and prevention of recurrence with anterior radical debridement, proper drug use and abscess drainage.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.53-61
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• 2015

The tension type joint is a mechanically very efficient connection method, as it directly uses the load capacity of base metal or high tension bolt, the reduction of the number of drilling hole and fastening and the fatigue resistance. It is applied to the joint of girder and cross beam, horizontal joints of towers, beam to column joints, the secondary member joints of deck floor ends, and brackets. In this paper, static load tests for the T-type tension joint were conducted to investigate the structural behavior of the joint. The parameters were bolt diameter, flange thickness, and the reduction of clamping force of the joint. The failure modes and load capacity of joints and the effects of flange thickness, bolt diameter and clamping force were investigated.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.77-85
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• 2015

This paper describes the development of force limiting device(FLD). The FLD could induce compressive yield before occurring elastic buckling for slender member under compressive load. Therefore, it might prevent reduction of load carrying capacity by elastic buckling and the structures with the devices would behave stable. A new type of FLD reduced cross area is proposed in this study different to existing studies like as out of plane type, slit type and folded plate type. The parameters of specimens are depth, width and number of cutting. The structural capacity and characteristics of proposed types were verified by experiment and FEM analysis. The FLD of cutting type is efficient in compressive member.

• Earthquakes and Structures
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• v.6 no.4
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• pp.409-436
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• 2014

Although it is widely accepted that the interaction -between masonry infill and structural members significantly affects the seismic response of reinforced concrete (RC) frames, this interaction is generally neglected in current design-oriented seismic analyses of structures. Moreover, the role of masonry infill is expected to be even more relevant in the case of existing frames designed only for gravitational loads, as infill walls can significantly modify both lateral strength and stiffness. However, the additional contribution to both strength and stiffness is often coupled to a modification of the global collapse mechanisms possibly resulting in brittle failure modes, generally related to irregular distributions of masonry walls throughout the frame. As a matter of principle, accurate modelling of masonry infill should be at least carried out by adopting nonlinear 2D elements. However, several practice-oriented proposals are currently available for modelling masonry infill through equivalent (nonlinear) strut elements. The present paper firstly outlines some of the well-established models currently available in the scientific literature for modelling infill panels in seismic analyses of RC frames. Then, a parametric analysis is carried out in order to demonstrate the consequences of considering such models in nonlinear static and dynamic analyses of existing RC structures. Two bay-frames with two-, three- and four-storeys are considered for performing nonlinear analyses aimed at investigating some critical aspects of modelling masonry infill and their effects on the structural response. Particularly, sensitivity analyses about specific parameters involved in the definition of the equivalent strut models, such as the constitutive force-displacement law of the panel, are proposed.

• Structural Engineering and Mechanics
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• v.24 no.1
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• pp.1-18
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• 2006

Strengthening of existing old structures has traditionally been accomplished by using conventional materials and techniques, viz., externally bonded steel plates, steel or concrete jackets, etc. Alternatively, fibre reinforced polymer composite (FRPC) products started being used to overcome problems associated with conventional materials in the mid 1950s because of their favourable engineering properties. Effectiveness of FRPC materials has been demonstrated through extensive experimental research throughout the world in the last two decades. However there is a need to use refined analytical tools to simulate response of strengthened system. In this paper, an attempt has been made to develop a numerical model of strengthened reinforced concrete (RC) beams with FRPC laminates. Material models for RC beams strengthened with FRPC laminates are described and verified through a nonlinear finite element (FE) commercial code, with the help of available experimental data. Three dimensional (3D) FE analysis has been performed by assuming perfect bonding between concrete and FRPC laminate. A parametric study has also been performed to examine effects of various parameters like fibre type, stirrup's spacing, etc. on the strengthening system. Through numerical simulation, it has been shown that it is possible to predict accurately the flexural response of RC beams strengthened with FRPC laminates by selecting an appropriate material constitutive model. Comparisons are made between the available experimental results in literature and FE analysis results obtained by the present investigators using load-deflection and load-strain plots as well as ultimate load of the strengthened beams. Furthermore, evaluation of crack patterns from FE analysis and experimental failure modes are discussed at the end.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.248-258
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• 2002

The sixth underground pumped powerhouse cavern is now under construction in Korea. For the stability analysis for the caverns of the five underground powerhouses, finite element method was used. For the analysis, in-situ rock stress were measured by overcoring method. The stress measurement showed that initial horizontal to vertical stress ratio was 1.07-1.32 in low powerhouse sites. Rock mass strength and elasticity were assumed from rock core properties through engineering processes. So the ratio of input elasticity fur the analysis were about 0.16-0.55 to rock core elasticity. In most of the analysis, elasto-plastic condition with Mohr-Coulomb failure criteria were applied. But in one case, viscoelastic condition was applied, too. The input cohesion and internal friction angle were approximately 0.12-0.22, 0.6-0.87 to rock core strength parameters, respectively.