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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Society of Civil Engineers
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Journal DOI :
Korean Society of Civil Engeneers
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Volume & Issues
Volume 15, Issue 6 - Nov 1995
Volume 15, Issue 4 - Jul 1995
Volume 15, Issue 3 - May 1995
Volume 15, Issue 2 - Mar 1995
Volume 15, Issue 1 - Jan 1995
Selecting the target year
The Influence of Traffic Information on Drivers' Route Preference
NamGung, Moon ; Sung, Soo-Lyeon ; Jang, Jong-Cheol ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1479~1479
A Driver Information System provides drivers with dynamic traffic information such as travel time and travel speed. A driver receives real-time traffic information from a variable message board, and chooses the most appropriate route In this study we empirically analyzed the influence of traffic information on drivers' route preferences by earring out a stated preference survey at a model street and its detour in the city of Ik San, Korea. Comparing the route preferences of. drivers who predicted that average speed would be faster on the model street and those drivers who predicted that average speed would be faster on the detour route. before and after receiving traffic information revealed that the such information altered the preferred route. This indicates that drivers' route preferences after receiving traffic information depends on what route was planned before receiving that information. We also found that traffic information influenced the route preference of experienced drivers more than those of inexperienced drivers for the de-lour and that the lack of traffic information significantly affected the preference for the detour route.
Assessment of Response Reduction Factor Using Monte Carlo Analysis
Hong, Won-Kee ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1489~1489
Both randomness of structural materials and structural mechanics equations must be quantified to define structural behavior and behavioral limit states. Strength reduction factor is one of important design parameters which can be prescribed in terms of safety levels of structural response based on proper measure of reliability involved. In this study structural engineering materials were tested to obtain the statistics of uncertainty in structural engineering materials. This paper employs Monte Carlo technique to propose strength reduction factors of four shear walls made of different steel ratio and subjected to different axial load. The strength and response reduction factors were com-pared among the four types of shear walls with different design parameters. And also comparison was made with the results obtained from linear statistical analysis for the validation of both practicability and applicability.
Diagnosis of Cracks in a Cantilever Beam from Measured Modal Response
Shin, Soo-Bong ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1501~1501
A non-destructive damage detection and assessment algorithm is developed based on a system identification method using a parameterized finite element model and the measured modal response of a structure. Damage is defined as the reduction in an element constitutive property from a baseline value. An adaptive parameter group updating scheme is proposed to localize the damaged zones in a structure and a measured data perturbation scheme is proposed to provide a statistical basis for assessing damage. Damage indices from the Monte Carlo sample of data perturbation iterations are used to assess damage. The threshold value for each damage index is established through Monte Carlo simulation on the baseline structure to distinguish damage from measurement noise. The proposed algorithm is applied to the problem of locating a crack in a cantilever beam. A Bernoulli-Euler beam model and Timoshenko beam model are employed to illustrate the use of the developed non-destructive diagnosis method and com- pare the efficiency of the two models for crack detection.
Code Requirements on Minimum Shear Reinforcement in High-Performance Concrete Beams
Yoon, Young-Soo ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1511~1511
This paper presents the evaluation of the minimum shear reinforcement requirements in normal. medium and high-strength reinforced concrete beams. Twelve shear tests were conducted on full-scale beam specimens having design concrete compressive strengths of 35, 70 and 100 MPa. Different amounts of minimum shear reinforcement were investigated, including the amounts required by Korean Concrete Standard (KCI88). JCI86, ACI89 (revised 1992) and CSA94 standard. The performance of the different amounts of shear reinforcement are discussed in terms of the shear capacity, the ductility and the crack control at service load levels. An assessment of code provisions for minimum shear reinforcement, and the prediction and comparison of the ultimate shear capacity are also presented.
A Study on the Wheel Load Distributuion of Composite I-Girder Bridges
Oh, Ji-Taek ; Yang, Chang-Hyun ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1521~1521
The composite I-girder bridges are frequently encountered in current bridge constructions because of advantages of composite sections. Highway Bridge Design Codes of many countries give formulas, tables or graphs for simple and reasonable bridge design. For examples, AASHTO (American Association of State Highway and Transportation Officials) specifications and OHBDC (Ontario Highway Bridge Design Code) methods are based on equivalent orthotropic plate theory and semicontinuum theory, respectively. This paper presents an idealization technique, which can be used to analyze the composite I-girder bridges. The transverse section of the deck of a composite I-girder bridge is idealized as a continuous beam on I-girders which can be assumed as discrete elastic supports The slop-deflection equations are modified and proposed to be applied to this idealized model to obtain translational and rotational behaviors of the elastic supports. Results of proposed method are compared with those by AASHTO specifications, OHBDC methods, and finite element method to confirm validity of the pro-posed method. Proposed method is shown to give rational maximum design bending moments for I-girder regardless of the type of trucks, and seems to be used to analyze the composite I-girder bridges with simplicity and effectiveness.
Active Control of Structural Vibration by Optimal Output Feedback Controller Considering Design Constraints
Koh, Hyun-Moo ; Park, Kwan-Soon ; Park, Won-Suk ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1535~1535
A control algorithm considering control force limitation and state constraints is developed for the active control of structural vibration. The controller using linear quadratic regulator with output feedback solves successfully problems of multi-degree of freedom and limited number of sensors. Control forces are calculated by multiplying precalculated feedback gains by output measurements. The concept of energy normalization and relative weighting parameters are introduced to consider design constraints, i.e., limitation of control forces and states of a structure. Numerical simulations are illustrated through the control of a three degrees of freedom shear building excited by the 81 Centre earthquake (1940, NS). Free vibration control tests of single degree of freedom shear building model and cable stayed bridge model with random initial conditions show effectiveness of the proposed controller.
A Study on Failure Criterion for Cement Concrete Pavement Slabs
Lee, Seong-Won ; Kim, Moon-Kyum ; Kim, Soo-Il ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1545~1545
Failure criterion for cement concrete pavement slabs are developed combining the finite element analysis and the AASHTO design equation. Analysis model is constituted for considering domestic concrete pavement slabs. The tensile stress at the bottom of concrete pavement slabs and number of load repetition for failure are computed from the finite element analysis and the AASHTO design equation respectively. therefore failure equation are developed through the regression analysis. The developed failure criterion is compared with existing failure criteria. Load repetition for failure for doemstic concrete pavement slabs is calculated and the effects of load repetition for failure on the back calculation error is analyzed.
Mechanical Characteristics of Asphalt Concrete at Low Temperatures
Kim, Kwang-Woo ; Yeon, Kyu-Seok ; El Hussein, M. ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1557~1557
In this study, a laboratory investigation to evaluate characteristics of asphalt concrete at low temperatures was performed using two asphalt cements, 85/100 and 150/200. Occurrence of localized damage as a result of tensile stress caused by differential thermal contraction has been supported by existing data and by studies dedicated to investigation of this phenomenon. Exposure of asphalt concrete to extremely low temperatures (below
) results in reduced flexural strength. fracture toughness and fatigue resistance. These reductions can be explained as a direct consequence of hairline cracks caused by differential thermal contraction. The asphalt cement grade showed a minor control of the flexural strength and to a lesser extent the fracture toughness of the mix at extremely low temperatures. Further investigations are required to compare the performance of other mixes using modified binders and other aggregates with that of the conventional binder mixes evaluated in this study.
Analytical Study on the Effectiveness of the Use of Asphalt-Rubber Membrane to Reduce Reflection Cracking in Overlay Pavement
Jin, Myung-Sub ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1565~1565
The incidental problem, when an overlay with an asphalt cement on an existing concrete cement pavement is undertaken, is a reflection cracking, that is a cracking shown on a surface through an overlay from the ones produced on the existing pavement. Among several methods to reduce this reflection cracking, one method which lays down asphalt-rubber on an existing pavement as a stress-absorbing membrane interlayer (SAMI) before overlay is done is being applied very often in the other advanced countries. In this paper, the theoretical study was made through the FEM analysis to reveal that SAMI is actually effective in lessening reflection cracking by absorbing a stress which may be produced during the overlay period. The effect of SAMI utilization was examined as the magnitude of the effective stress obtained by the FEM analysis for the selected point which was chosen arbitrarily from the crack-tip, and as the change of the magnitude of a thermal stress due to the temperature change at the surface of the overlay. As a result, it was found that the effective stress decreased remarkably in case SAMI was used, and that the SAMI's elastic modulus and the thickness of an asphalt layer were the major factors affecting the effective stress. In addition, this study showed that, when SAMI was not utilized, the effective stress decreased with increasing the overlay's thick-ness, increasing the elastic modulus of an asphalt layer, and decreasing the elastic modulus of concrete. It was also shown that SAMI was effective in minimizing a reflection cracking by reducing a thermal stress remarkably at the crack-tip.
Validation of Back-Calculated Moduli Using Laboratory-Determined Resilient Modulus of Field Cores
Kim, Nak-Seok ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1575~1575
Falling weight deflectometer (FWD) drops were applied on two test roads, and the resulting surface deflections were measured simultaneously using FWD geophones. The MODULUS 4.0 back-calculation program developed by the Texas Transportation Institute (TTI) was used to back-calculate the asphalt concrete layer moduli values of each test section. In the validation process, the comparison between the back-calculated and la-oratory-determined asphalt concrete layer moduli was made to evaluate the influence of different assumptions made before back-calculation. Strategic Highway Research Program (SHRP) Load Guide (LG) device was used to measure the laboratory-determined asphalt concrete layer moduli. The SHRP LG device was developed as a part of the Strategic Highway Research Program's Long-Term Pavement Performance project. This device was recommended by the National Co-operative Highway Research Program (NCHRP) Project 1-28 as the most promising testing equipment after extensive comparisons among conventional testing equipments. The effects of test condition variables on laboratory-determined resilient modulus of asphalt concrete were also studied.
A Performance Evaluation of the Continuously Reinforced Concrete Pavement in Korea through Field Condition Surveys
Nam, Young-Kug ; Suh, Young-Chan ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1587~1587
A performance evaluation study of the Korean Continuously Reinforced Concrete Pavements (CRCP) was conducted through field condition surveys. The survey items included crack width, crack spacing, and steel stress which are the AASHTO CRCP performance criteria. Surveys were conducted on the several locations of the Kyongbu Expressway, Jungbu Expressway and Pangyo-Guri Expressway. The survey results were compared with the AASHTO performance criteria and several foreign field survey results. It was found from this study that the Korean CRCP generally met the AASHTO performance criteria and compares quite well with foreign CRCPs.
Friction Factor of Commercial Pipe
Yoo, Dong-Hoon ; Wun, Yoo-Seung ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1593~1593
Yoo (1995) has developed two methods for the estimation of friction factor of commercial pipes; one is named as mean zero velocity point method and the other as mean friction factor method, both of which are based on the assumption that smooth surfaces and rough surfaces co-exist inside the same commercial pipe. In the present study the data collected by Colebrook (1938) are re-analyzed using Yoo's methods assumming the smooth surface has no roughness at all so that the Nikuradse equivalent roughness and probability of rough surface are determined for each commercial pipe. It is found that both roughness height and probability have a clear trend in relation with the pipe diameter, and functional relations of both are suggested. The present approach has exellent agreement with most of Colebrook data of friction factor, while Colebrook-White approach has poor agreement with most of his data.
Three-Dimensional Boundary Integral Equation Model for Prtential Flow Problem
Cho, Yong-Sik ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1607~1607
The boundary integral equation method for three-dimensional potential flow problems involves surface integrals over the boundaries. When linear elements are used to discretize the boundaries, the surface integrals can be converted into line integrals by the Green's theorems. Analytical expressions are obtained for these line integrals, The analytical integrations give accurate results even for integrals including a nearly singular case. A boundary integral equation model based on analytical integrals is developed. The model is simpler and requires less computing time than the existing model. Finally, the developed model is applied to solve a simplified confined aquifer system governed by the Laplace equation. The model can also be applied to the potential flow problems governed by the three-dimensional Laplace equation such as the calculation of hydrodynamic pressure acting on the gravity dam during earthquake.
Verification of the Model for Wave Propagation by Water Release from Reservoirs
Woo, Hyo-Seop ; Kim, Won ; Lee, Jin-Won ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1615~1615
Water released from upstream dams for downstream water supply increases river discharge and propagates downstream as monoclinal wave in the river. This study tests the applicability of the monoclinal wave model to this condition. The data used for this test are the ones collected from the Nakdong River during the water pollution accident in the early 1994, when the upstream two dams released a large amount of waters in order to dilute and flush the pollutants inflowed into the river. The physical meanings and characteristics of the monoclinal wave are carefully reviewed with existing literature concerning that type of water wave. Then, the monoclinal wave model is verifed mainly with the data observed in the Nakdong River. This study confirms that the propagation speed of the monoclinal wave, expressed as C=KV with the value of K of 1.5, can be used properly for the estimation of the propagation speed of a step-increased river discharge released from upstream dams.
Application of Multigrid Method for Fully Developed Flow in Rectangular Duct
Lee, Jong-Seol ; Heo, Jun-Haeng ; Cho, Won-Cheol ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1627~1627
The multigrid method is introduced and applied to a fully developed flow in the rectangular duct. The applicability of the multigrid method was examined comparing the results with those from the conventional iterative methods. The convergences of the multigrid and the convention리 methods were compared within the same tolerance. The multigrid method showed faster convergence than the successive line over-relaxation (SLOR) method by sixty to ninety percent. The multigrid method's CPU time was also faster than that of the successive over-relaxation (SOR) method by thirty to eighty percent. Ex cept the aspect ratio of the rectangular duct is one, the governing equation for the fully developed flow in the rectangular duct became the anisotropic elliptic partial differential equation. Thus, the convergence of each method was different based on the aspect ratio. When the aspect ratio was not one, the Gauss-Seidel method, which is the point re-laxation method, had no smoothing property. When the line relaxation method was used as the smoother, the convergence and the CPU time were getting faster as the aspect ratio increased.
Application of Regression Model for Determination of Parameters in Confined Nonleaky Aquifer
Chung, Il-Moon ; Heo, Jun-Haeng ; Cho, Won-Cheol ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1639~1639
In this study, the nonlinear regression model is applied to determine the parameters in confined nonleaky aquifer The selected nonlinear equation is Theis' and its approximated form is also selected for this purpose. Theis equation can be linearized using Taylor series expansion, and the regression model is established by Gauss-Newton method which fits computed values to the measured ones through iteration process. The damping parameter is used to induce convergence, and the parameters such as transmissivity and storage coefficient in the equation are computed. These results are very close to the graphical results. The statistical validity for the regression model is shown through various statistical measures such as goodness of fit of computed and measured data, correlation of the parameters, error variance and residual analysis. Thus, the regression model is proved as an appropriate approach to determine the parameters in confined nonleaky aquifer.
Study on Applicability of Probability Weighted Moment Method to Rainfall Frequency Analysis
Kim, Yang-Su ; Heo, Jun-Haeng ; Ryu, Hee-Jung ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1647~1647
The parameter estimation of the probability distribution functions (PDF) are important in the rainfall frequency analysis. Recently. a WMO' report presented that Probability Weighted Moment (PWM) method is effective in the parameter estimation of PDF. This study is focused on discussion of applicability of PWM to rainfall frequency analysis. A comparative study of skewness coefficients for five PDFs and two parameter estimation methods such as method of moments (MOM) and PWM method were conducted by using Korean rainfall data sets. The results showed that PWM was robustic in parameter estimation of PDF and didn't derive skewed distribution type even though the data set comprised rainfall event of extremely large amount. But the MOM derived skewed distribution type when data set used in the analysis comprised rainfall event o extremely large amount. As a result. PWM method is stable in parameter estimation of PDF, and estimates smaller skewness coefficient relatively in the rainfall frequency analysis.
Wave Group Behavior for Time-Dependent Mild-Slope Equations
Lee, Chang-Hoon ; Pyun, Chong-Kun ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1659~1659
The time-dependent mild-slope equations are studied in order to determine whether the models preserve the proper behavior of wave groups for narrow-banded random waves. Analytical studies of modulation of wave amplitudes are presented. Analytical and numerical studies are also shown for bichromatic waves propagating over a bottom with constant water depth. Smith and Sprinks' model (1975) (or mathematically equivalent, Radder and Dingemans' model (1985)) and Kubo et al.'s model (1992) can analyze not only monochromatic waves but also narrow-banded random waves with accuracy of O(
). However, Nishimura et al.'s model (1983) (or mathematically equivalent, Copeland's model (1985)) can analyze only monochromatic waves. The former models may be defined as first-order unsteady time-dependent mild-slope equations and the latter model as a steady time-dependent mild-slope equation.
An Analysis of Shallow Water Flow by Two Step Explicit Finite Element Scheme
Kim, Nam-Hyeong ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1669~1669
A finite element method for analyzing shallow water flow is presented. The Galerkin method is employed for spatial discretization. Two step explicit finite element scheme is used to discretize the time function, which has advantage in problems treating large numbers of elements and unsteady state. As to a test example, progressive waves have been carried out. The numerical result is in good agreement with the analytical solution. As a practical application, the tidal current of Cheju harbor has been computed. The computed results have shown the good adaptability of the two step explicit scheme. From these studies, it can be concluded that the present method is a useful and effective tool in progressive waves and tidal current analysis.
Analysis of River Bed Change by Using Computer Model GSTARS
Seo, Il-Won ; Kim, Dae-Geun ; Lee, Jae-Hyung ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1679~1679
Analyses of long-term and short-term changes of river bed in Keum and Han Rivers were implemented by using computer model GSTARS that is a semi two-dimensional model. Comparison of the long-term simulations by GSTARS and HEC-6 models with measured data shows that simulations by both models are in fair agreements with the measured data in overall trend of the river bed changes. GSTARS model predicted the overall changes of lateral profile of the river bed quite well except local aggradation and scour. Comparison of the short-term simulations by GSTARS and CHARIMA models with measured data shows that simulation by GSTARS model gives better agreement with the measured data than the CHARIMA model. Based on these analyses, it is considered that GSTARS model can predict both long-term and short-term changes of river bed relatively well.
Estimation of Maximum Scour Depth at Bridges Due to Flood by Using 2-Dimensional Hydrodynamic Model
Yoon, Yong-Nam ; Yoon, Jae-Young ; Lee, Jae-Soo ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1689~1689
The safety against hydraulic scouring at bridge section is often regarded as important as the structural safety of the bridge itself. Hence, the objective of this study is to apply the existing methodology for the scour estimation at a bridge section. To estimate scour depth two steps are generally followed. One is the calculation of hydraulic characteristics of the flood flows, and the other is the estimation of scour depth. For the first step, 2-dimensional hydrodynamic model, TABS-MD is employed and for the second step, the procedure proposed in HEC-18 published by U.S. Federal Highway Administration is followed. To investigate the effect of the magnitude of river flows, 6 different discharges are selected and finally maximum scour depth, which has great importance for design purpose, is estimated. Although the estimation has not been verified with field data, the procedure can be usefully referenced as a guide to estimate the scour at a bridge section for the future flood event, and it can also be referenced for the design of new bridges in the same manner.
Flood Frequency Analysis at Indogyo Station in Han River Basins(I) -Data Analysis & Selection of PDF-
Seo, Kyu-Woo ; Kim, Kyung-Duk ; Heo, Jun-Haeng ; Cho, Won-Cheol ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1697~1697
The annual maximum water level at Indogyo Station was standardized based on the section of 1991 as a standard since a remarkable change in river bed has been occurred due to Han River Development Project and there was a big flood in 1990. The previous levels and discharges were converted based on the present rating curve. A comparative analysis was performed for the converted water levels and peak flows of the selected floods. Also, total runoff caused by such floods were compared each other. The flood data was divided into three groups excluding the missing data. The estimated parameters were obtained and tested by considering the validity of the parameters for the selected thirteen probability distributions. Finally, the appropriate probability distributions for flood data at Indogyo station were selected based on the goodness of fit tests and graphical analysis of empirical and fitted probability density functions and cumulative distribution functions.
A Study on the Educing of Inquire Data in Traffic Accident Using Close Range Photogrammetry
Kim, Gam-Lae ; Kim, Myoung-Bae ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1711~1711
We revive a traffic accident with the main object of educing the bases for settlement of the accident through a accurate reconstructions of situation before or after the vehicle collision. And yet, there are many troubles due to a deficiency of scientific and logical measure for conduct of traffic accidents. In this study, consequently, we developed the scientific method to secure the materials on the scene of accident by means of close lange photogrammetry. On the basis of data extracted by the close range photogrammetry, we present a method to calculate the speed and aspect at that time for the scientific conduct of traffic accident.
A Study on the Acquisition of Image Coordinates in Digital Image for 3 Dimensional Measurement
Han, Seung-Hee ; Kang, Joon-Mook ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1721~1721
Industrial measuring and modeling with accuracy is an important, but also time consuming and expensive element in industry. The CCD imaging technology provides many advantages over film-based systems with respect to rapidity and efficiency. This paper discussed the acquisition method of digital image with CCD camera and tried to find a process of image enhancement in accordance with the characteristics of the CCD. And we also developed the method of transforming BIN image file to BMP file for the application on the windows program. Digital image was acquired suitable to coordinate measurement after image enhancement such as histogram analysis to BMP image, equalization, brightness, contrast, noise elimination, and sharpening. Also we acquired pixel coordinate for target point on the object and transformed to image coordinate. Next, we selected a parts of automobile, tested bundle adjustment by method of this study and existing photogrammetry surveying, and consequently examined three dimensional accuracy and efficiency. In addition, We suggested three dimensional measurement method applicable to the whole range of industry by accomplishing fast and efficient modeling technique by means of digital photogrammetry.
GPS (Global Positioning System) - Aided Aerial Triangulation in Small Area
Park, Woon-Yong ; Kang, Joon-Mook ; Lee, Jae-One ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1731~1731
Since 1983 NAVSTAR GPS (NAVigation System with Time And Ranging Global Positioning System) has been one of the best methods for exact positioning in geodesy, engineering surveys and photogrammetry. The main advantage of GPS-supported aerial triangulation is the gross reduction of ground control points which are also determined indirectly by very tedious and costly terrestrial measurements. In this paper, the basic principle of GPS and the mathematical algorithm for GPS-aided combined bundle block adjustment are illustrated. As a example, Blumenthal-Test flight in 1988, one of the conducted experiments at the university of Hannover, shows that GPS-technique is a very powerful method for aerial triangulation. The achieved positioning accuracy was very high, about
cm in each of the three coordinates, with only four control points.
A Forward and Back Analysis of Underground Structures by the Coupled Method of Finite Elements and Boundary Elements
Kim, Moon-Kyum ; Jang, Jung-Bum ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1743~1743
In order to construct underground structural systems safely and economically, exact identification of the system parameters and accurate analysis of the system behaviors are required. In this study, a forward analysis program. which is able to eliminate numerical errors due to far field boundary effect, is developed by coupling finite elements and boundary elements. In this coupled analysis, boundary elements are used in the semi-infinite domain where stress variation is small, and finite elements in the stress concentration region where material nonlinearity should be considered. Reliability and usefulness of the developed forward analysis program are demonstrated by comparing the numerical results with those from the finite element analysis and FLAC. A back analysis program which can identify the system parameters is also developed using the direct method to be combined with the forward analysis program. Results of the back analysis program in this study show good agreement with that of Gens et al.
A Study on the Pore Pressure Prediction for Unsaturated Soils
Lim, Heui-Dae ; Park, Soo-Yong ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1755~1755
The concept of pore pressure parameters has been convenient to visualize the pore pressure response of saturated soils for various applied stress changes. This paper derives pore pressure parameters that can be utilized in determining the pore pressure response of unsaturated soils such as the compacted clayey materials. Pore pressure parameter expressions are also derived for pore pressure induced as the result of isotropic stress and deviator stress changes during undrained loading. The parameters required to computation in the proposed model can be readily determined from the conventional triaxial compression tests. Emphasis has been placed on the analysis of construction pore pressures in partially saturated soil and a case study has been presented. The pore pressures in core of Juam regulation dam are estimated by the proposed model, on the basis of data obtained by triaxial compression tests of soil samples in the laboratory. The results of the pore pressure measuring in situ are also obtained from the measuring devices installed in clay core zone. The pore pressures predicted are com pared with the measured pore pressures of the core zone. It is shown from the comparison that they do not differ in some profiles and they have symmetrical position with regard to the core axis, whereas the isochrones from the measurements in situ show a specific distribution in other profiles. The reasons for this non-coincidence are explained.
Determination of Optimum Shape Ratio of Single Grouser of Tracked Vehicle and Prediction of Soil Thrust
Soek, Jeong-Woo ; Park, Young-Ho ; Kim, Oon-Young ; Kim, Myoung-Mo ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1765~1765
The optimum shape ratio (1.50-1.65) of single grouser was obtained from the relationship between the shape ratio of grouser and the soil thrust measured from the model soil-bin tests with varied soil densities and the contact pressure for the granite-weathered soil (SP). The soil thrust was numerically predicted using the stress characteristic curves determined by the modified Sokolovsky's method of considering the points of the soil density and the velocity characteristic curves of connecting the points of discontinuity of displacement. According to the results of the model tests and numerical analysis, the optimum shape ratio was found to increase with the contact pressure under the same density and the velocity characteristic curves showed a closer estimation of soil thrust and failure pattern to the test results than the stress characteristic curves.
Settlement Characteristics of Municipal Wastes
Lee, Bock-Soo ; Hwang, Kyu-Ho ; Lee, Kwang-Yeol ; Lee, Song ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1773~1773
The Landfilling method and efficien re-use Problem based on geo-environment engineering is raised with industrial development and population increase. When designed on geotechnical engineering. one of the important factors is the settlement of filling waste. In fact as the components of wastes are complex, it is difficult to analyze the settlement theoretically. In this study, two types of wastes were tested to observe the settlements about two years, which were high-rise waste and low-rise one composed of municipal waste. As a result, the primary settlement was terminated immediately in about two months and the time-dependent deformation was developed largely and continuously, and settlement rate was increased more relatively in the summer than in the winter due to growth of decomposition effect. Making use of creep equation and Gibson-Lo model based on experimental settlement data for first one year, the result is that power relation and Gibson-Lo model is available. The prediction by logarithmic, hyperbolic relation has a tendency to underestimate the monitored settlement and the case by exponential relation shows exact value assuming
Development of Analytical Method for Laterally Loaded Pile Groups
Kim, Soo-Il ; Jeong, Sang-Seom ; Lee, Sang-Won ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1783~1783
In this study, a computer program to predict the behavior of laterally loaded single pile and pile groups was developed by using a finite difference method and a matrix structural analysis in which the soils are modeled as nonlinear springs by a family of p-y curves for subgrade modulus. The emphasis was given to the lateral displacement of pile groups due to the soil condition and the cap rigidity. The analysis considering group effect was carried out for
pile groups with the pile spacing 3.0B, 4.0B and 5.0B. Based on the results obtained, it is found that the overall distributions of deflection, slope, moment, and shear force in a single pile give a reasonable results irrespective of cap connectivity conditions. It is also found that in pile groups, the prediction by present analysis simulates much better the general trend observed by the centrifuge tests than the numerical solution predicted by PIGLET.
Pullout Characteristics of Anchors in Two Layered Clay
Shin, Bang-Woong ; Lee, Jun-Dae ; Lee, Bong-Jik ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1795~1795
Model tests were conducted with respect to various embedment depths and two different moisture contents in saturated clay. For the model tests, kaolinite and bentonite were used. The behaviour of plate anchor embedded in a two-layered clay deposit has been brought out. The experimental study has been carried out in two phases one plate anchor embedded in kaolinite bed overlain by bentonite bed and another in bentonite bed overlain by kaolinite bed. For plate anchors embedded in bentonite bed overlain by kaolinite bed, it is found that movements are quite large. So it is better to terminate the plate anchor in kaolinite bed without touching the bentonite bed. For plate anchors embedded in kaolinite bed overlain by bentonite bed, the uplift capacity depends on the kaolinite bed thickness only.
Comparison of Equilibrium Beach Profiles on On-Offshore Sediment Transport
Lee, Cheol-Eung ; Lee, Kil-Seong ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1803~1803
The comparison and investigation of all four equilibrium beach profiles including profile equation derived in this paper using energy dissipation are presented for the correct application of profile equations and solving the intrinsic problems. Two among equilibrium beach profiles were verified under the assumption of a constant median sediment size, while the other two equilibrium beach profiles were derived to consider the effect of a varying grain size. The results of the equilibrium profiles with the effect of a varying grain size are better in agreement with the measured data than those of the equilibrium profiles based on the constant grain size assumption. In particular it is concluded that the present profile equation is identified to the existing-profile equations under some conditions and well in agreement with the measured profile.
Generation and Simulation of Variability on Nearshore Bars by Hybrid Numerical Model
Lee, Cheol-Eung ; Lee, Kil-Seong ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1811~1811
A multi-domain hybrid numerical model for the prediction of cross-shore sediment transport including bar generation and movement is developed in this paper based on the morphologic sediment transport and conservation equations. It is assumed that the main cause of bar generation is the breaking wave, and the entire surf zone is then divided into several sub-domains, such as post-breaking zone, transition zone, breaking zone and pre-breaking zone. Different empirically-based sediment transport rate equation is defined in each region. The solutions in each domain are matched at the patching boundaries by the continuity of the beach profile and sediment transport rate. It is verified that the present hybrid numerical model reasonably simulates beach erosion, dune recession, and bar formation and movement by comparison with several large-scale experiments. The present numerical model is also validated through comparison with the fold data of Ocean City, Maryland.
Bragg Reflection of Shallow-Water Waves
Cho, Yong-Sik ; Lee, Jong-In ; Lee, Jong-Kyu ; Yoon, Tae-Hoon ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1823~1823
Based on the Boussinesq equations, the Bragg reflection of shallow-water waves was theoretically investigated. A set of governing equations the evolution of modulated shallow-water waves over slowly varying topography was derived. The governing equations include the nonlinear interactions of waves propagating both in the same and in the opposite directions as well as the shoaling effect over a slowly varying topography. It has been shown that the incident waves could be resonantly reflected by the interaction with the sinusoidally varying seabed under the Bragg reflection condition. The magnitude of the resonantly reflected wave was approximately equal to that of the incident wave. It has been found that the reflection is enhanced by increasing the number of seabed ripples.
Species Selection in Aeration Basin Using the Continuous Selector
Chun, Yang-Kun ; Choi, Yong-Su ; Choung, Youn-Kyoo ;
Journal of The Korean Society of Civil Engineers, volume 15, issue 6, 1995, Pages 1833~1833
This study was conducted to improve the performance of biological wastewater treatment system using the continuous selector with inclined wall. This selector was designed so that microorganisms might be separated by their specific weight and controlled by flowrate and inclined angle of selector. The kinetics of separated microorganisms and reactor maintenance coefficients were measured to determine the stability of the reactor. As a result, the separation of microorganisms was affected by the conditions of aeration basin and selector. The optimal range of inclined angle for separation within the selector was 35 to 40 degree to vertical axis. When the flowrate ratio (
) was in the range of 0.3 to 0.6, the maintenance coefficient was higher than 1.5 and the reactor was stable. Overflowed microorganisms had high value of yield coefficient and specific growth rate but poor settlability. If the selector is operated properly, it is expected that the efficiency of wastewater treatment system is improved by means of units process rearrangement and optimal scaling.