• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5654-5663
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• 2015

In the unsaturated soil, suction, the negative pore water pressure leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Therefore, in this study, the stress-strain relationship based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the 1st and the 2nd yield functions was induced in order to account for these effects of suction under the dynamic loading condition such as the earthquake. Through the program code considering this relationship and the routine of the cyclic loading with the reversion of loading direction, the numerical simulation of the cyclic triaxial test under the unsaturated condition would be possible. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.205-214
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• 2010

Masonry structures have been used throughout the world for the construction of residential buildings. However, from a structural point of view, the masonry material is characterized by a very low tensile strength. Moreover, the bearing and shear capacity of masonry walls have been found to be vulnerable to earthquakes. In this study, to improve the seismic performance of masonry walls, hexagonal blocks were developed and six masonry walls made with hexagonal block were tested to failure under reversed cyclic lateral loading. This paper focuses on an experimental investigation of different types of wall with hexagonal blocks, i.e. walls with different hexagonal blocks and with different reinforcing bar arrangements, subjected to applied cyclic loads. The cracking, damage patterns and hysteretic feature were evaluated. Results from the hexagonal masonry wall were shown more damage reduction and less brittle failure in comparison to the existing rectangular masonry walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.83-90
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• 2018

Considering the increased threats from worldwide terrors and the increased demands on the blast resistant design of commercial buildings, this study is aimed at understanding the basic concept of blast resistant design and evaluating the blast performance with an actual design example. Although there are many differences between earthquake and blast loads, the design concept against both loads is similar in terms of allowing the plastic behavior of a structure and sharing the ductile detailing. Through the blast performance evaluation of a target building provided in this study, it is noted that a well-designed building for the conventional loads can have a certain level of blast resistance. However, this cannot be generalized since the blast load on a structure varies depending on the type of weapon, TNT equivalence, standoff distance, etc. Architectural planning with positioning the sacrificial structure or maintaining a sufficient standoff distance from the expected detonation is the simple and effective way of improving the blast resistance of a building.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.51-58
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• 2018

In this study a series of centrifuge tests were carried out in dry sand to analyze the comparison of lateral pile behavior for static loading and dynamic loading condition. In case of static loading condition, the lateral displacement was applied up to 50% of pile diameter by deflection control method. And the input sine wave of 0.1 g~0.4 g amplitude and 1 Hz frequency was applied at the base of the soil box using shaking table for dynamic loading condition. From comparison of experimental static p-y curve obtained from static loading tests with API p-y curves, API p-y curves can predict well within 20% error the ultimate subgrade reaction force of static loading condition. The ultimate subgrade reaction force of experimental dynamic p-y curve is 5 times larger than that of API p-y curves and experimental static p-y curves. Therefore, pseudo-static analysis applied to existing p-y curve for seismic design could greatly underestimate the soil resistance at non-linear domain and cause overly conservative design.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.133-143
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• 2006

A fully coupled effective stress dynamic analysis procedure for modeling seismic liquefaction on slope is presented. An elasto-plastic formulation is used for the constitutive model UBCSAND in which the yield loci are radial lines of constant stress ratio and the flow rule is non-associated. This is incorporated into the 2D version of Fast Lagrangian Analysis of Continua (FLAC) by modifying the existing Mohr-Coulomb model. This numerical procedure is used to simulate centrifuge test data from the Rensselaer Polytechnic Institute (RPI). UBCSAND is first calibrated to cyclic direct simple shear tests performed on Nevada sand. Both pre- and post-liquefaction behaviour is captured. The centrifuge test is then modeled and the predicted accelerations, excess porewater pressures, and displacements are compared with the measurements. The results are shown to be in general agreement. The procedure is currently being used in the design of liquefaction remediation measures for a number of dam, bridge, tunnel, and pipeline projects in Western Canada.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.128-137
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• 2012

In high multistory buildings, hybrid coupled shear walls can provide an efficient structural system to resist horizontal force due to wind and seismic loads. Hybrid coupled shear walls are usually built over the whole height of the building and are laid out either as a series of walls coupled by steel beams with openings to accommodate doors, elevator walls, windows and corridors. In this paper, the behavior characteristics of hybrid coupled shear wall system considering connection details is examined through results of an experimental research program where 5 two-thirds scale specimens were tested under cyclic loading. Such connections details are typically employed in hybrid coupling wall system consisting of steel coupling beams and reinforced concrete shear wall. The test variables of this study are embedment length of steel coupling beam and wall thickness of concrete shear wall. The results and discussion presented in this paper provide fundamental data for seismic behavior of hybrid coupled shear wall systems.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.171-180
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• 2005

In this study the seismic performance of a three-story knee-braced moment-resisting frame (KBMRF), which is typically employed to support pipelines for oil or gas, was investigated. Nonlinear static pushover analyses were performed first to observe the force-displacement relationship of KBMRF under increasing seismic load. The results show that, when the maximum inter-story drift reached 1.5% of the story height, the main structural members, such as beams and columns, still remained elastic. Then nonlinear dynamic time-history analyses were carried out using eight earthquake ground motion time-histories scaled to at the design spectrum of UBC-97. It turned out that the maximum inter-story drift was smaller than the drift limit of 1.5 % of the structure height, and that the columns remained elastic. Based on these analytical results, it can be concluded that the seismic performance of the structure satisfies all the requirements regulated in the seismic code.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.69-72
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• 2008

The so-called Pier-Shafts system which consists of the continuous column and shaft is often used to support the highway bridge structure because of advantages in easy construction and low cost. In the earthquake region, the Pier-Shafts system undergoes large displacements and represents a nonlinear behavior under the lateral seismic loading. The soil-pile interaction should be considered for more accurate analysis of the Pier-Shafts system. In this study, a transverse response of a reinforced concrete Pier-Shafts system inside multi-layered soil medium is predicted using a finite element program which adopts an elasto-plastic interface model for the interface behavior between the shaft and the soil. Then, seismic analysis is performed to evaluate the performance of Pier-Shafts system under strong ground motion and their results are verified with experimental data.

• Journal of Korean Association for Spatial Structures
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• v.12 no.2
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• pp.65-72
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• 2012

In this stury, control performance of tuned mass damper (TMD) with torsional rigidity for an eccentric structure showing torsional responses is investigated. To this end, an eccentric structure subjected to earthquake excitation is used to evaluate the control performance of torsional TMD by varying installed location and torsional rigidity of TMD, To reduce computational time required for repetitive time history analysis of an example structure having non-proportional damping system due to TMD, an equivalent analytical model is used in this study. Torsional properties of TMD usually neglected in typical TMD are verified to be effective in reduction of torsional responses of the eccentric structure. In the case of eccentric structures, it has been seen that the center of a plane of a structure may not be optimal location of TMD.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.13-26
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• 2005

It was known that the aging effect of sands is insignificant in comparison with clays, and hence the study on this effect had seldom been performed prior to the early 1980s. However, field tests for this effect have been actively carried out since it was investigated that penetration resistance of reformed sands increased with the lapse of time. Recently, the aging effect of sands has also been examined in laboratory testings. In this study, undrained static triaxial tests were performed to evaluate the effect on the Nak-dong River sands, with different .elative densities $(D_r)$, consolidation stress ratios $(K_c)$, and consolidation times. As a result of the tests, it was proved that the undrained cyclic shear strength $(R_f)$ increased with the aged time on the sands. The in situ range of Rf on the sands, which is applicable to the magnitude of earthquake in the Nak-dong River area, was proposed by using the test results.