• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1118-1125
• /
• 2005

In this study, seismic safety of CFRD(Concrete-Face Rockfill Dam) type "D" dam in operation is evaluated from the results of 1-g shaking table test using similitude laws. Model dam is made by similitude law considering the grain size of prototype dam component. After the model dam is impounded to the normal water level(N.W.L), it is excited by artificial earthquake wave corresponding to standard design respond spectrum of the "D" dam site. Displacement response behavior of the dam is examined through the measurement of vertical and horizontal displacement of dam crest. Also, amplification characteristics of acceleration with dam height is examined through the measurement of acceleration with dam height. Finally, the purpose of this study is to evaluate seismic safety of "D" dam in operation. From the results of acceleration measurement, it was found that acceleration of dam crest was amplified about 1.52 times compared to the acceleration of dam bottom and amplification phenomenon is outstanding at three quarters of dam height from the bottom of dam. From the analysis of displacement behavior, it was estimated that vertical displacement of prototype dam is 6.8cm (0.1% of dam height) and horizontal displacement 12.3cm(0.2% of dam height). These percentages is much lower than 1% of dam height(general stability criteria). Therefore, it was concluded that seismic stability of "D" dam against an estimated earthquake is guaranteed.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.4
• /
• pp.92-100
• /
• 2001

It is very important to determine the coefficient of earth pressure at rest accurately in order to estimate the behavior of soil structure. For estimation of K/sub 0/-value depending upon the stress history of dry sand, a new type of K/sub 0/-oedeometer apparatus is devised, and the horizontal earth pressure is accurately measured. For this study, 2 types of one-cyclic K/sub 0/-Loading/unloading models have been studied experimentally using four relative densities of the sand. The results obtained in this test are as follows : K/sub on'/ the coefficient of earth pressure at - rest for virgin loading is a function of the angle of internal friction Φ' of the sand and is determined as K/sub on/=1 - 0.914 sin Φ', K/sub ou'/ the coefficient of earth pressure at rest for virgin unloading is a function of K/sub on/ and over consolidation ratio(OCR), and is determined as K/sub ou/=K/sub on/(OCR)K/sup a/. The exponent α, increases as the relative density increases. K/sub or'/ the coefficient of earth pressure at rest for virgin reloading decreases in hyperbola type as the vertical stress, σ/sub v/’, increases. And, the stress path at virgin reloading leads to the maximum prestress point, independent upon the value of the minimum unloading stress. The gradient of this curve, m/sub r/ increases as OCR increases.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.6
• /
• pp.81-90
• /
• 2011

The purpose of this study was to investigate the seismic performance of reinforced concrete bridge columns with interlocking circular hoops. Three interlocking columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used for the analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve the existing practice in the design and construction of reinforced concrete bridge columns with interlocking circular hoops.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.14 no.1
• /
• pp.51-62
• /
• 2010

The purpose of this study was to investigate the performance of hollow precast segmental PSC bridge columns. The proposed system can reduce work at a construction site and makes construction periods shorter. Shortened construction times, in turn, lead to important safety and economic advantages when traffic disruption or rerouting is necessary. Two hollow precast segmental PSC bridge columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures, was used. The proposed numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated.

• KCI Concrete Journal
• /
• v.13 no.1
• /
• pp.69-78
• /
• 2001

The inelastic behavior of a reinforced concrete columns is influenced by a number of factors : 1) level of axial load, 2) tie spacing, 3) volumetric ratio of lateral steel, 4) concrete strength, 5) distribution of longitudinal steel, 6) strength of lateral steel, 7) cover thickness, 8) configuration of lateral steel, 9) strain gradient, 10) strain rate, 11) the effectively confined concrete core area, and 12) amount of longitudinal steel. A new constitutive model of a confined concrete is suggested in order to investigate the nonlinear behavior of the reinforced concrete columns under concentric loading. The developed constitutive model for the confined concrete takes into account the effects of effectively confined area as well as the horizontal and longitudinal distributions of the confining pressures. None of the existing models incorporated these two main effects at the same time. A total of different six constitutive models for the behavior of the confined concrete under concentric compression were compared with the sixty-one test results reported by different researchers. The superiority of the developed model in its accuracy is demonstrated by evaluating the error function, which compares the weighted averages for the sum of squared relative differences in peak compressive strength and corresponding strain, stress at strain equal to 0.015, and total area under stress-strain curve up to strain equal to 0.015.

• Earthquakes and Structures
• /
• v.7 no.5
• /
• pp.705-718
• /
• 2014

This paper presents an analytical model for determining the transverse reinforcement required for reinforced concrete exterior beam-column joints subjected to reversed cyclic loading. Although the joint aspect ratio can affect joint shear strength, current design codes do not consider its effects in calculating joint shear strength and the necessary amount of transverse reinforcement. This study re-evaluated previous exterior beam-column joint tests collected from 11 references and showed that the joint shear strength decreases as the joint aspect ratio increases. An analytical model was developed, to quantify the transverse reinforcement required to secure safe load flows in exterior beam-column joints. Comparisons with a database of exterior beam-column joint tests from published literature validated the model. The required sectional ratios of horizontal transverse reinforcement calculated by the proposed model were compared with those specified in ACI 352R-02. More transverse reinforcement is required as the joint aspect ratio increases, or as the ratio of vertical reinforcement decreases; however, ACI 352R-02 specifies a constant transverse reinforcement, regardless of the joint aspect ratio. This reevaluation of test data and the results of the analytical model demonstrate a need for new criteria that take the effects of joint aspect ratio into account in exterior joint design.

• Computers and Concrete
• /
• v.10 no.3
• /
• pp.241-258
• /
• 2012

The need for long-span members increases gradually in recent years, which makes issues not only on ultimate strength but also on excessive deflection of horizontal members important. In building structures, the post-tension methods with unbonded tendons are often used for long-span members to solve deflection problems. Previous studies on prestressed flexural members with unbonded tendons, however, were mostly focused on the ultimate strength. For this reason, their approaches are either impossible or very difficult to be implemented for serviceability check such as deflection, tendons stress, etc. Therefore, this study proposed a flexural behavior model for post-tensioned members with unbonded tendons that can predict the initial behavior, before and after cracking, service load behavior and ultimate strength. The applicability and accuracy of the proposed model were also verified by comparing with various types of test results including internally and externally post-tensioned members, a wide range of reinforcement ratios and different loading patterns. The comparison showed that the proposed model very accurately estimated both the flexural behavior and strength for these members. Particularly, the proposed model well reflected the effect of various loading patterns, and also provided good estimation on the flexural behavior of excessively reinforced members that could often occur during reinforcing work.

• Geomechanics and Engineering
• /
• v.27 no.5
• /
• pp.419-431
• /
• 2021

Construction of retaining walls with geocell has been gaining in popularity because of its easy and fast installation compared to conventional methods. In this study, model tests were conducted by constructing the geocell retaining wall (GRW) at a constant height (i.e., 90 cm) and using aggregate as an infill material at four different configurations and two different surface angles. In these tests, a circular footing was placed behind the walls at different lateral distances from the wall surface and loaded monotonically. Subsequent to this vertical loading being applied to the footing, horizontal displacements on the GRW surface were measured at three different points. The performance of Type 4 GRW exceeded the other three types of GRW, with the highest lateral displacement occurring in Type 4 GRW at approximately 0.67 % of wall height. In addition, the results of these tests were compared with theoretical approaches widely accepted in the literature. The stress levels reached beneath the footing were found to be compatible with theoretical results.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.3
• /
• pp.41-49
• /
• 2007

The typical bonding methods which connect steel pipe pile and spread footing is bolted bonding method using +type cover plate for reinforcing a head of steel pipe pile. In this paper, stability of spread footing in pile foundation have been evaluated by loading test of +type cover plate for reinforcing a head of pile and hook type bonding method. The presents results from a series of pilot model test on vertically loaded piles foundation of bolted bonding method and hook type bonding method, pile foundation is identified to safety due to pile foundation exceed 8.5~21% which more than yield stress of steel pipe pile. As the results of horizontal loading tests, peak load of piles foundation of hook type bonding method has estimated in 41.1tonf and it was exceed about 33% which more than pile foundation of bolted bonding method.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.265-275
• /
• 2003

In this study, shaking table tests were conducted to estimate dynamic interface properties between geosynthetics such as geomembrane, geotextile and geosynthetic clay liner. Accelerations of both shaking table and upper box, and relative displacements between geosynthetics under dynamic loading were measured. Also, the influence of normal stress, frequency of excitation and dry/wet conditions were investigated through the analyses of test results. from the test results, it was found that there is a limited acceleration below which dynamic farce can be transmitted between geosynthetics without the loss of horizontal acceleration. Dynamic interface friction angle between geosynthetics could be calculated through the limited acceleration. Relative displacements induced along geosynthetic interfaces under dynamic loading were not consistent depending on the type of interface and test conditions. The maximum slip displacements between geosynthetics are normalized and normalized slip equations were developed for each interface. By using the normalized slip equation, maximum slip displacements for the geosynthetic interface could be predicted for the given base acceleration and frequency of excitation.