• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.186-193
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• 2012

The wood-concrete composite can be effectively applied for bridge superstructure, and the concept of fully composite action between each member is one of the most important consideration. Until now, related researches have been done mainly in North America and EU countries not enough to cover the fundamental studies. Therefore, this study is planned to perform one of the important issue for using the wood-concrete composite. The objective of this study is evaluation of shear performance with different anchorage length of steel rebar in wood. Prediction of the yield mode and the reference design value was firstly performed as the preliminary investigation. Then, initial stiffness, yield load and maximum load were derived from the shear test due to different anchorage length of the steel rebar (SD30A in Korean Standard) in wood. It was found out from this study that initial stiffness and yield load are not related with the anchorage length over 20 mm of anchorage length while maximum load shows increasing tendency till 60 mm of anchorage length. Pullout strength of inserted steel rebar in wood is considered to be one reason and this was also verified with the x-ray radiography.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.511-520
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• 2007

There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. The advantages of fibre reinforced plastic(FRP) composites over conventional materials motivate their use in highway bridges for replacement of structures. Recently, an FRP deck has been installed on a state highway, located in New York State, as an experimental project. In this paper, a systematic approach for analysis of this FRP deck bridge is presented. Multi-step linear numerical analyses have been performed using the finite element method to study the structural behavior and the possible failure mechanism of the FRP deck-superstructure system. Deck's self-weight and ply orientations at the interface between steel girders and FRP deck are considered in this study. From this research, the results of the numerical analyses were corroborated with field test results. Analytical results reveal several potential failure mechanism for the FRP deck and truss bridge system. The results presented in this study may be used to propose engineering design guideline for new and replacement FRP bridge deck structure.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.580-610
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• 1993

The purpose of this study was to analyse the deflection and stress distribution at the supporting bone and it's superstructure by the alteration of angulation between implant and it's implant abutment. For this study, the free-end saddle case of mandibular first and second molar missing would be planned to restore with fixed prosthesis. So the mandibular second premolar was prepared for abutment, and the cylinder type osseointegrated implant was placed at the site of mandibular second molar for abutment. The finite element stress analysis was applied for this study. 13 two-dimensional FEM models were created, a standard model at $0^{\circ}$ and 12 models created by changing the angulation between implant and implant abutment as increasing the angulation mesially and distally with $5^{\circ}$ unittill $30^{\circ}$. The preprocessing decording, solving and postprocessing procedures were done by using FEM analysis software PATRAN and SUN-SPARC2GX. The deflections and von Mises stresses were calculated under concentrated load (load 1) and distributed load(load 2) at the reference points. The results were as follows : 1. Observing at standard model, the amount of total deflection at the distobuccal cusp-tip of pontic under concentrated load was largest of all, and that at the apex of implant was least of all, and the amount of total deflection at the buccal cusp-tip of second premolar under distributed load was largest of all, and that at the apex of implant was least of all. 2. Increasing the angulation mesially or distally, the amounts of total deflection were increased or decreased according to the reference points. But the order according to the amount of total deflection was not changed except apex of second premolar and central fossa of implant abutment under concentrated load during distal inclination. 3. Observing at standard model, the von Mises stress at the distal joint of pontic under concentrated load was largest of all, and that at the apex of implant was least of all. The von Mises stress at the distal margin of second premolar under distributed load was largest of all, and that at the apex of Implant was least of ail. 4. Increasing the angulation of implant mesially, the von Mises stresses at the mesial crest of implant were increased under concentrated load and distributed load, but those were increased remarkably under distributed load and so that at $30^{\circ}$ mesial inclination was largest of all. 5. Increasing the angulation of implant distally, the von Mises stresses at the distal crest of implant were increased remarkably under concentrated load and distributed load, and so those at $30^{\circ}$ distal inclination were largest of all.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.507-524
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• 2002

Load transfer of implant overdenture varies depending on anchorage systems that are the design of the superstructure and substructure and the choice of attachment. Overload by using improper anchorage system not only will cause fracture of the framework or screw but also may cause failure of osseointegration. Choosing anchorage system in making prosthesis, therefore, can be considered to be one of the most important factors that affect long-term success of implant treatment. In this study, in order to determine the effect of anchorage systems on load transfer in mandibular implant overdenture in which 4 implants were placed in the interforaminal region, patterns of stress distribution in implant supporting bone in case of unilateral vertical loading on mandibular left first molar were compared each other according to various types of anchorage system using three-dimensional photoelastic stress analysis. The five photoelastic overdenture models utilizing Hader bar without cantilever using clips(type 1), cantilevered Hader bar using clips(type 2), cantilevered Hader bar with milled surface using clips(type 3), cantilevered milled-bar using swivel-latchs and frictional pins(type 4), and Hader bar using clip and ERA attachments(type 5), and one cantilevered fixed-detachable prosthesis(type 6) model as control were fabricated. The following conclusions were drawn within the limitations of this study, 1. In all experimental models. the highest stress was concentrated on the most distal implant supporting bone on loaded side. 2. Maximum fringe orders on ipsilateral distal implant supporting bone in a ascending order is as follows: type 5, type 1, type 4, type 2 and type 3, and type 6. 3. Regardless of anchorage systems. more or less stresses were generated on the residual ridge under distal extension base of all overdenture models. To summarize the above mentioned results, in case of the patients with unfavorable biomechanical conditions such as not sufficient number of supporting implants, short length of the implant and unfavorable antero-posterior spread. selecting resilient type attachment or minimizing distal cantilever bar is considered to be appropriate methods to prevent overloading on implants by reducing cantilever effect and gaining more support from the distal residual ridge.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.240-249
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• 2007

Statement of problem: A phenomenon of screw-loosening in implant abutment is frequently occurred in a single and multiple implant restoration. Purpose: This study was performed to evaluate an effect of abutment material on screw-loosening before and after a cyclic loading. In a single-tooth implant, different materials of abutment, Type III Gold alloy and Zirconium composite$(ZrO_2/Al_2O_3)$ were used. Material and method: The Gold alloy(Type III) and Zirconium composite$(ZrO_2/Al_2O_3)$ were used to make a superstructure of implant, the one of types of UCLA, Each group was constituted of 5 sample with a 30-degree offset angulated loading platform. The external hexagonal fixture was rigidly hel d in a special holding zig to ensure solid fixation without rotation during the tightening and a cyclic loading. A Titanium-alloy screw was used to connect and controlled to be tighten in 20Ncm torque by a digital torque gauge. A 20 times of consecutive closing/opening cycle were performed to evaluate the immediate torque loss. In 5 sample of each material group, an initial opening torque was recorded during 3 closing/opening cycle, then 2Hz, 200N, 1,000,000 cyclic loadings were performed, then a opening torque was evaluated. Result & Conclusion: 1. In this limited study, titanium alloy screw tightened in 20Ncm, a cold-welding phenomen on was not observed during the 20 times of closing/opening cycle(p=0.11, p=0.18). 2. In titanium alloy abutment screw, repeated opening and closing of the screw caused to progressive decrease of opening torque(p=0.014). 3. The difference in preload of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant(p=0.78). 4. The difference in torque loss of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant after 2Hz,200N, 1,000,000 cyclic loading(p=0.92). 5. In titanium alloy abutment screw tightened by 20Ncm, the screw loosening was not significant on each group after 2Hz, 200Ncm, 1,000,000 cyclic loading(p=0.59).

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.271-278
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• 2016

In the case of South Korea, steel girder bridge (steel box or H-steel) and PSC (Pre-Stressed Concrete) girder bridge are the representative upper structures of railroad and road bridges. These structures account for 75% of the total bridge constructions and 80% of the total construction cost. Since the form work for concreting bridge slab is difficult, various construction methods developed and applied. However, several problems in those methods did not solve partially, including cost increase by material loss and rise of labor costs, quality deterioration by unskilled workers, increased construction time by complicated method, reduced productivity, safety accident by high place work, difficult transportation by big member, and rise of maintenance cost by material characteristic. Alternative method is needed to solve problems of as-is methods. Therefore, the purpose of this study is development of the purlin hanging system form for the girder bridge slab and its economic analysis. Through the findings of this study, it was verified that the purlin hanging system form is possible 60% reduction in cost and 80% reduction in time as comparison with conventional method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.779-789
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• 2015

Because cable-supported bridges have long spans and large members, their movements and geometrical changes by temperatures tend to be bigger than those of small or medium-sized bridges. Therefore, it is important for maintenance engineers to monitor and assess the effect of temperature on the cable-supported bridges. To evaluate how much the superstructure expands or contracts when subjected to changes in temperature is the first step for the maintenance. Thermal movements of a cable-stayed bridge in service are evaluated by using long-term temperatures and displacements data. Displacements data are obtained from extensometers and newly installed GNSS (Global Navigation Satellite System) receivers on the bridge. Based on the statistical data such as air temperatures, each sensor's temperatures, average temperatures and effective temperatures, correlation analysis between temperatures and displacements has been performed. Average temperatures or effective temperatures are most suitable for the evaluation of thermal movements. From linear regression analysis between effective temperatures and displacements, the variation rate's of displacement to temperature have been calculated. From additional regression analysis between expansion length's and variation rate's of displacement to temperature, the thermal expansion coefficient and neutral point have been estimated. Comparing these parameters with theoretical and analytical results, a practical procedure for evaluating the real thermal behaviors of the cable-supported bridges is proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.849-856
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• 2011

This paper proposes a method for transforming unstructured text contents of engineering documents, which have complex hierarchical structure of subtitles with various heading symbols, into a semi-structured XML document according to the hierarchical subtitle structure. In order to extract the hierarchical structure from plain text information, this study employed a method of document structure extraction which is an analysis technique of the document structure. In addition, a method for processing enumerative text contents was developed to increase overall accuracy during extraction of the subtitles and construction of a hierarchical subtitle structure. An application module was developed based on the proposed method, and the performance of the module was evaluated with 40 test documents containing structural calculation records of bridges. The first test group of 20 documents related to the superstructure of steel girder bridges as applied in a previous study and they were used to verify the enhanced performance of the proposed method. The test results show that the new module guarantees an increase in accuracy and reliability in comparison with the test results of the previous study. The remaining 20 test documents were used to evaluate the applicability of the method. The final mean value of accuracy exceeded 99%, and the standard deviation was 1.52. The final results demonstrate that the proposed method can be applied to diverse heading symbols in various types of engineering documents to represent the hierarchical subtitle structure in a semi-structured XML document.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.681-688
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• 2005

This study investigates an existing steel plate girder railroad bridge after superstructure rehabilitation to monitor static and dynamic responses using Fiber Bragg Grating (FBG) sensors. This paper also presents an experimental technique to estimate the vertical deflection of the bridge using FBG sensors. Seven FBG sensors are multiplexed in a single optical fiber and installed in parallel pairs along the length of the bridge, with one set at the top flange and the other at the bottom flange. In addition to FBG sensors, a conventional electric strain gauge and anLVDT are installed at the mid-span of the bridge for comparison. A test train consisting of one locomotive is placed at the center of the bridge to produce the maximum static effect. The train is also made to pass over the bridge at different speeds ranging from 10 km/h to 90 km/h to monitor the dynamic response of the bridge. This study demonstrates that the measured strains using the FBG sensor compared well with the readings from the electric strain gauge. The results show that the proposed instrumentation technique is capable of estimating the vertical deflection of the bridge for various loading conditions, which is crucial in structural health monitoring. Several dynamic characteristics of the bridge were also identified.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.755-763
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• 2002

Multispan simply supported bridges and multispan continuous bridges take a large portion of bridges in Central and Southeastern United Sates. The superstructure of the bridges are supported by steel rocker bearings. In general, the rocker bearings are modeled with ideal rollers or Coulomb fricition in seismic analysis. However, the rocker bearings have rocking action on pintles after rolling some distance. This rocking action may have considerable effect on the seismic performance of bridges. This study compares the effect of expansion rocker bearings models on a multispan simply supported and a multispan continuous bridge. Since the ideal roller model produces larger responses than the rocking model, its use is undesirable. However, the fricition and hardening model does not have much difference from the responses of the rocking model. In addition, the use of the tow models is convenient in seismic analyses of bridges. Although the rocking model can obtain more exact responses, its behavior is complicated and it may induce the conversion problem in time history analysis because it includes the abrupt changing of stiffiness. The friction and hardening model of expansion rocker bearings is therefore recommended in sesismic analysis.