• Steel and Composite Structures
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• v.37 no.2
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• pp.117-136
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• 2020

Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25° and 45° were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.269-281
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• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• International journal of steel structures
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• v.18 no.4
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• pp.1210-1218
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• 2018

A new type of earthquake-resisting element that consists of a steel plate shear wall with slits is introduced. The infill steel plate is divided into a series of vertical flexural links with vertical links. The steel plate shear walls absorb energy by means of in-plane bending deformation of the flexural links and the energy dissipation capacity of the plastic hinges formed at both ends of the flexural links when under lateral loads. In this paper, finite element analysis and experimental studies at low cyclic loadings were conducted on specimens with steel plate shear walls with multilayer slits. The effects caused by varied slit pattern in terms of slit design parameters on lateral stiffness, ultimate bearing capacity and hysteretic behavior of the shear walls were analyzed. Results showed that the failure mode of steel plate shear walls with a single-layer slit was more likely to be out-of-plane buckling of the flexural links. As a result, the lateral stiffness and the ultimate bearing capacity were relatively lower when the precondition of the total height of the vertical slits remained the same. Differently, the failure mode of steel plate shear walls with multilayer slits was prone to global buckling of the infill steel plates; more obvious tensile fields provided evidence to the fact of higher lateral stiffness and excellent ultimate bearing capacity. It was also concluded that multilayer specimens exhibited better energy dissipation capacity compared with single-layer plate shear walls.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.35-45
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• 2006

강원도 홍천일대의 지역은 경기육괴의 편마암이 주암종으로 이루어진 지역으로 대규모의 홍천단층이 지나고 있다. 과거 이 단층대 부근에서 건설된 도로건설시에 발생된 많은 절토사면의 붕괴를 통해 그 원인 파악 및 차후 고려해야 할 사항을 파악하는 것이 매우 중요한 과제 중에 하나이다. 본 논문은 붕괴를 토대로 붕괴의 원인 및 대책방안을 파악하고자 한다. 홍천일대의 사면붕괴를 유발시키는 원인으로는 크게 두 가지 지질구조적인 요인을 들 수 있는데 하나는 사면방향으로 발달하는 편마암내에 발달하는 엽리면을 따라 붕괴가 발생되는 사례가 있고 둘째는 단층파쇄대 및 단층대를 따라 붕괴가 발생되는 원인으로 대별할 수 있다. 두 번째의 요인은 비교적 규모가 큰 사면붕괴를 유발하게 되고 막대한 복구비용이 수반되는 결과를 초래하게 된다. 이러한 단층의 수반에 의해 발생되는 절토사면은 대책방안으로 사면경사완화 방안, 앵커 및 억지말뚝과 같은 보강방법에 의해 안정화를 시키는 사례가 주를 이루었으며 차후 이 일대의 건설공사시에는 단층대의 방향 및 규모에 대한 조사를 세밀히 이루어져야 할 것이다.

• Structural Engineering and Mechanics
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• v.10 no.1
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• pp.53-66
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• 2000

This paper proposes a simple numerical model for use in a finite analysis (FEA) of scaffold-shoring systems. The structural model consists of a single set of multiple-story scaffolds with constraints in the out-of-plane direction at every connection joint between stories. Although this model has only two dimensions (termed the 2-D model), it is derived from the analysis of a complete scaffold-shoring system and represents the structural behavior of a complete three-dimensional system. Experimental testing of scaffolds up to three stories in height conducted in the laboratory, along with an outdoor test of a five-story scaffold system, were used to validate the 2-D model. Both failure modes and critical loads were compared. In the comparison of failure modes, the computational results agree very well with the test results. However, in the comparison of critical loads, computational results were consistently somewhat greater than test results. The decreasing trends of critical loads with number of stories in both the test and simulation results were similar. After investigations to explain the differences between the computationally and experimentally determined critical loads, it was recommended that the 2-D model be used as the numerical model in subsequent analysis. In addition, the computational critical loads were calibrated and revised in accordance with the experimental critical loads, and the revised critical loads were then used as load-carrying capacities for scaffold-shoring systems for any number of stories. Finally, a simple procedure is suggested for determining load-carrying capacities of scaffold-shoring systems of heights other than those considered in this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.141-154
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• 1987

The algorithm proposed utilizes the tow-levels technique. In the first level which consists of teeatment only the applied load and design stress as the random variables whose parent distribution has the normal distribution, the cross-sectional areas of the truss members such that the their probabilities of failure have the preseribed failure probabilites are optimized by transforming the nonlinear problem into SUMT, and solving it utilizing modified Newton-Raphson method. In the second level, the geometric shape of truss structure is optimized by utilizing the unidirectional search technique of Powell method which makes it possible to minimize only the objective function. The algorithm proposed is numerically tested for the several truss structures with various shapes and loading conditions. The numerical analysis shows that the rate of decreasing the weight of truss structures is dependent on the prescribed failure probability of the each member of truss structure and the covariance of the applied load and design stress.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.135-145
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• 2004

In this study, the behavior of unpropped diaphragm walls on decomposed granite soil was investigated through centrifugal and numerical modelling. Centrifuge model tests were performed by changing the interval distance of surcharge. Excavation was simulated during the centrifuge tests by operating a solenoid valve that allowed the zinc chloride solution to drain from the excavation. In these tests, ground deformation, wall displacement and bending moment induced by excavation were measured. FLAC program which can be able to apply far most geotechnical problems was used in the numerical analysis. In numerical simulation, Mohr-Coulomb model fur the ground model, an elastic model for diaphragm wall were used for two dimensional plane strain condition. From the results of model tests, failure surface was straight line type, the ground of retained side inside failure line had downward displacement to the direction of the wall, and finally the failure was made by the rotation of the wall. The angle of failure line was about 67 ∼ 74$^{\circ}$, greater than calculated value. The locations of the maximum ground settlement obtained from model tests and analysis results are in good agreements. The displacement of wall and the change of the embedment depth is likely to have linear relationship.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1293-1298
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• 2010

In most power plants, wall thinning in carbon-steel pipes due to flow-accelerated corrosion is one of the major aging phenomena, and it reduces the load-carrying capacity of the piping system. Various types of wall-thinning defects were manufactured in real-scale elbows, and monotonic in-plane bending tests were performed under internal pressure to evaluate the failure behavior of the elbows. In this paper, the behavior of elastic and plastic limit leads of locally thinned elbows in a real-scale failure test is presented. The loads determined on the basis of TES (twice elastic slope) were considered to be the limit loads of locally thinned elbows so that the integrity of the thinned elbows could be maintained, even when a small amount of plastic deformation might have occurred.

• Geotechnical Engineering
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• v.6 no.3
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• pp.65-76
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• 1990

A series of consolidated drained and untrained cubical triaxial tests were performed to investigate three dimensional strength characteristics of compressible sand. All specimens, which are formed by deposisting a fine sand loosely, were used. Failure strength in terms of effective stress analysis was greatly influenced by the variation of intermediate principal stress and so was failure criterion The adjusted effective frictional angles obtained by the stress state projected on the same octahedral plane showed almost same value, while the measured effective frictional angles showed considerable difference depending on the drainage conditions. Results of total stress analysis in undrained test turned out to fit Tresca's failure criterion well, but results of effective stress analysis turned out to fit Lade's failure criterion well.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.89-92
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• 2008

This study investigates the shear behavior of architectural masonry veneer wall reinforced with specific reinforcement details proposed by this study. For this purpose, experimental tests were conducted using one un-reinforced masonry(URM) wall specimen and three reinforced masonry(RM) wall specimens under quasi static cyclic loads. Un-reinforced(plain) masonry wall is expressed that behavior and failure mode are different for aspect ratio(L/H) and axial compressive force. The test variables are wall aspect ratio and presence of reinforcement. These specimens are masonry structure for architectural clading that is not to exist the axial compressive force. thus the axial compressive force is excepted from test variable. Test result, Behavior of specimens are dominated over rocking mode, but final failure modes are combined with different behaviors. And FEMA273 has proposed the equation of shear strength of masonry pier subjected to in-plane loading. Shear strength equations are classified four types of failure mode that is Rocking, and Toe-Crushing, Bed-Joint-Sliding and Diagonal-Tension. FEMA273 equations predict the behavior modes well, but shear strength is shown in different result.