• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.53-58
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• 2002

A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.61-71
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• 2010

Five half-scale beam-to-column connections in a precast concrete frame were tested with cyclic loading that simulated earthquake-type motions. Five half -scale interior beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including one monolithic specimen and four precast specimens. Variables included the detailing used at the joint to achieve a structural continuity of the beam reinforcement, and the type of special reinforcement in the connection (whether ECC or transverse reinforcement). The specimen design followed the strong-column-weak-beam concept. The beam reinforcement was purposely designed and detailed to develop plastic hinges at the beam and to impose large inelastic shear force demands into the joint. The joint performance was evaluated on the basis of connection strength, stiffness, energy dissipation, and drift capacity. From the test results, the plastic hinges at the beam controlled the specimen failure. In general, the performance of the beam-to-column connections was satisfactory. The joint strength was 1.15 times of that expected for monolithic reinforced concrete construction. The specimen behavior was ductile due to tensile deformability by ECC and the yielding steel plate, while the strength was nearly constant up to a drift of 3.5 percent.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.165-172
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• 2002

Generally, the steel rigid frame has been analyzed using finite element analysis tools. While many efforts have been poured into the understanding and accurate prediction for the nonlinear behavior of the columns and beam-columns connections, the base of the columns are modeled as simply hinged or fixed. However, the base of the steel columns practically is neither fixed not hinged. It behaves as semi-rigid. In this paper, the supports of the columns we modeled as semi-rigid and the importance of such approach in moment-resisting columns is evaluated. Two typical buildings designed by the US specification are modeled and analyzed by the finite element based on stiffness method and flexibility method. The column bases of three-story buildings are modeled as rotational springs with a varying degree of stiffness and strength that simulates the semi-rigidity of the base. Depending on the degree of stiffness and strength, the semi-rigidity varies from the hinged to the fixed. Buildings with semi-rigid column bases behaves similarly to the building with fixed bases. It has been numerically observed through the pushover and nonlinear time history analyses that the decrease of the stiffness of the column base induces the rotational demand on the int air beams. an increase of rotation demands on the first store connections and lead to a soft-story mechanists Due often to the construction and environmental effects, undesired reduction of column base stiffness may cause an increase of rotation demands on the first store connections and lead to a soft-story mechanism.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.2
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• pp.87-95
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• 2018

This paper introduces a new explicit spectral element method for the simulation of SH-waves in semi-infinite domains. To simulate the wave motion in unbounded domains, it is necessary to reduce the infinite extent to a finite computational domain of interest. To prevent the wave reflection from the trunctated boundaries, perfectly matched layer(PML) wave-absorbing boundary is introduced. The forward problem for simulating SH-waves in PML-truncated domains can be formulated as second-order PDEs. The second-order semi-discrete form of the governing PDEs is constructed by using a mixed spectral elements with Legendre-gauss-Lobatto quadrature method, which results in a diagonalized mass matrix. Then the second-order semi-discrete form is transformed to a first-order, whose solutions are calculated by the fourth-order Runge-Kutta method. Numerical examples showed that solutions of SH-wave in the two-dimensional analysis domain resulted in stable and accurate, and reflections from truncated boundaries could be reduced by using PML boundaries. Elastic wave propagation analysis using explicit time integration method may be apt for solving larger domain problems such as three-dimensional elastic wave problem more efficiently.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.1-11
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• 2012

In this paper, non-linear analysis was performed for Reinforced Concrete (RC) walls using different macroscopic models subjected to cyclic loading, and the analytical results were compared with previous experimental studies of RC walls. ASCE41-06 (American Society of Civil Engineers) specifies that the hysteresis behaviors of RC walls are different due to the aspect ratio of the walls. For a comparison between analytical and experimental results, a slender wall with an aspect ratio exceeding 3.0 and a squat wall with an aspect ratio of 1.0 were selected among previous research works. For the non-linear analysis, each test specimen was modeled using two different macroscopic methods: the first representing the flexural behavior of the RC wall, and the second considering the diagonal shear in the web of the wall. Through nonlinear analysis of the considered RC walls, the analytical difference of a slender wall was negligible due to the different macroscopic modeling methods. However, the squat wall was significantly affected by the considered components of the modeling method. For an accurate performance evaluation of the RC building with squat walls, it would be reasonable to use a macroscopic model considering diagonal shear.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.145-151
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• 2008

The research so far has primarily analyzed efficiency improvement but in this research, it analyzes the characteristics of earthquake behavior, with changed pier heights, through ordinary and seismic analysis. For this, the kind of bridge bearing has been changed against PSC I-shaped bridge, which is mostly used in practice, and at all times earthquake analysis has been performed with through height of pier. Especially considering sectional power resulting from earthquake analysis, displacement of PSC I-shaped bridge bearing, diameter of pier pillar by earthquake load, and upper spare gap have been analyzed. In case of high-pear, seismic isolated device is decided as proper for cars' driving and for management of bridge since it decreases movement of upper structure, than elastic bearing, reducing size of elastic connect device, and it's been analyzed it is effective for improvement of fine view and economic efficiency reducing section of lower bridge structure. Finally, when design PSC I-shaped bridge bearing, for the proper structure and high-pier side, applying seismic isolated device through precise inner analysis is proper than applying equal elastic bearing.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.243-253
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• 2011

This paper describes an analytical study on seismic performance of domestic reinforced concrete (RC) school building not designed by seismic provision. The seismic index and the seismic performance of the building were evaluated through Japanese standard and Midas Gen, respectively. Seismic index (Is) of the RC school buildings in the X-direction is below 0.4. Based on the seismic index, for seismic-strengthening the building, infill shear wall or steel brace with a capacity of 1,300 kN was used. According to nonlinear static analysis results, the contribution of the seismic-strengthening to the shear resistance of the school building was measured to be greater than 30%. However, as expected, shear strength of school building strengthened with infill wall dropt rapidly after peak load and much narrower ductile behavior range was observed compared to steel brace strengthened building. Also, the building strengthened with steel brace showed 30% larger spectral displacement than that strengthened with infill shear wall. In nonlinear dynamic analysis, for the time history analysis, the maximum displacement showed tendency to decrease as amount of reinforcement increased, regardless of strengthening method. It was recommended that variable soil properties and earthquake record should be considered for improving seismic performance of buildings in seismic zone.

• Journal of the Korean Geotechnical Society
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• v.35 no.9
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• pp.5-13
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• 2019

The soil-water characteristic curve (SWCC) plays an important role in determining the soil suction parameters required to predict the seepage or shear behaviors of unsaturated soils. In addition, path dependency of the SWCC affects the mechanical and hydrologic behaviors. In general, there is a disadvantage that it takes a long time to measure both the drying and wetting paths of the SWCC by a stepwise pressurization method. Thus, the continuous pressurization method as an improved testing method for the SWCC was suggested, and the testing time for two paths of the SWCC was significantly shorter than the conventional methods. For the applicability evaluation of this method, the results of the SWCC obtained by the stepwise pressurization method and the evaporation method in this study were compared to the result obtained from this method. As a result, it was found that the difference among three methods was negligible, and the testing time of the continuous pressurization method was greatly decreased. Therefore, it can be said that it is possible to quickly and accurately measure the SWCC under various conditions by the continuous pressurization method.

• Tunnel and Underground Space
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• v.33 no.1
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• pp.57-69
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• 2023

In this study, we simulated induced seismicity in the Groningen natural gas reservoir using 2D hydro-mechanical coupled discrete element modelling (DEM). The code used is PFC2D (Particle Flow Code 2D), a commercial software developed by Itasca, and in order to apply to this study we further developed 1)initialization of inhomogeneous reservoir pressure distribution, 2)a non-linear pressure-time history boundary condition, 3)local stress field monitoring logic. We generated a 2D reservoir model with a size of 40 × 50 km² and a complex fault system, and simulated years of pressure depletion with a time range between 1960 and 2020. We simulated fault system failure induced by pressure depletion and reproduced the spatiotemporal distribution of induced seismicity and assessed its failure mechanism. Also, we estimated the ground subsidence distribution and confirmed its similarity to the field measurements in the Groningen region. Through this study, we confirm the feasibility of the presented 2D hydro-mechanical coupled DEM in simulating the deformation of a complex fault system by hydro-mechanical coupled processes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.3
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• pp.185-192
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• 2023

In this study, fluctuating wind velocity for time history analysis is simulated by a single variate, single-dimensional random process using the KBC2022 spectrum about across-wind direction. This study analyzed and obtained the inelastic dynamic response for structures modeled as a single-degree-of-freedom system. It is assumed that the wind response is excellent in the primary mode, the change in vibration owing to plasticization is minor, along-wind vibration and across-wind vibration are independent, and the effect of torsional vibration is small. The numerical results, obtained by the Newmark-𝛽 method, shows the time-history responses and trends of maximum displacements. As a result of analyzing the inelastic dynamic response of the structure with the second stiffness ratio(𝛼) and yield displacement ratio (𝛽) as variables, it is identified that as the yield displacement ratio (𝛽) increases when the second stiffness ratio is constant, the maximum displacement ratio decreases, then reaches a minimum value, and then increases. When the stiffness ratio is greater than 0.5, there is a yield point ratio at which the maximum displacement ratio is less than 1, indicating that the maximum deformation is reduced compared to the elastically designed building even if the inelastic behavior is permitted in the inelastic wind design.