• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.6
• /
• pp.67-80
• /
• 2011

This paper presents the results of shaking table tests on a 1:5 scale 10-story R.C. wall-type residential building model. The following conclusions are drawn based on the test results. (1) The model responded linear elastically under the excitations simulating an earthquake with a return period of 50 years, and showed a nonlinear response under the excitations simulating the design earthquake of Korea. (2) The model showed a significant strength drop under the maximum considered earthquake, with a return period of 2400 years. (3) The major portion of the resistance to lateral inertia forces came from the walls used for the elevator and stair case. (4) Finally, the damage and failure modes appear to be due to the flexural behavior of walls and slabs. A significant deterioration of stiffness and an elongation of the fundamental periods were observed under increased earthquake excitations.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.4
• /
• pp.449-455
• /
• 2011

Recently, international collaborative research which was organized at Bhabha Atomic Research Centre in India, was conducted to develop for pressure capacity and nonlinear behavior of PHWR 1/4 scale nuclear containment building between experimental test and numerical code. In this paper, a nonlinear finite element analysis was carried out in order to predict ultimate pressure capacity and nonlinear behavior of the 1/4 scale containment building. The 1/4 scale containment building is consisted of basemat, cylinder wall, dome and 4-buttress. For the finite element analysis, commercial program ABAQUS was used. Finite element models including concrete, rebar and tendon have been developed for assessment of ultimate pressure capacity and failure mode for nuclear containment building. From the analysis results, first crack of the concrete, the yielding of the rebar and ultimate capacity pressure occurred at $1.6P_d$(design pressure), $3.36P_d$ and $4.0P_d$, respectively.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.35 no.3
• /
• pp.183-190
• /
• 2022

The construction of an underground silo structure was the first stage of erecting the Gyeongju low-and-intermediate-level radioactive waste disposal facility. The facility, completed in 2014, has a scale of 100 000 drums and is currently in operation. The underground silo structure, 25 and 50 m in diameter and height, respectively, consists of cylindrical (for storing waste packages) and dome parts. The dome is divided into lower (connected to the operation tunnel) and upper parts. The wall of the underground silo structure is an approximately 1-m-thick reinforced concrete liner. In this study, finite element analysis was performed for each phase of the construction sequence and operation of the underground silo structure. Two-dimensional axial symmetric finite element analysis was implemented using the SMAP-3D program. Three-dimensional finite element analysis was also performed to examine the reliability of the two-dimensional axial symmetric finite element model. The structural behavior of the underground silo structure was predicted, and its structural safety was examined.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.5
• /
• pp.151-160
• /
• 2022

Owing to the recent increase in the frequency of explosion accidents, blast resistive design has garnered attention to reduce the damage of important structural elements. However, domestic research on the blast resistive structures is still insufficient, and domestic design guideline against blast loads are not documented yet. In this study, a numerical study on the RC blast resistive walls, where the test variable was the presence of FRP sheet, was performed using LS-DYNA program. Based on the numerical results, displacement-time hysteretic curve, pressure-impulse diagram, and fragility curve of the test specimens were derived. It was shown that the FRP sheet strengthening method is efficient to improve the blast resistive performance of the RC wall. Also, the strengthening effect of FRP sheet on the RC wall was stronger when the magnitude of the blast load was greater.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.3
• /
• pp.48-54
• /
• 2022

This research describes a quantitative procedure used to estimate the effect of concrete cracking on stiffness degradation of concrete shear walls and provides analytical references for the seismic design of concrete shear walls. As preliminary research on the seismic response of concrete shear walls, nonlinear transient analysis was performed with commercial FE software. The study presents the nonlinear time history analysis results in terms of concrete damage and cracking behavior induced by seismic input motions. By varying the input motions, concrete strength and shear wall thickness, the seismic responses of a shear wall were examined with nonlinear time history analysis, and the progressive cracking behavior and corresponding hysteresis loop were described. Based on the analysis results, frequency and stiffness degradation of the shear wall from progressive concrete damage and cracking were captured with respect to the seismic levels. The results of this study suggest that stiffness degradation from concrete cracking should be appropriately considered when determining the seismic capacity of RC shear wall structures.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.621-637
• /
• 2006

Although the approaches implementing strut-tie models are the valuable tools for designing discontinuity regions of structural concrete, the approaches of the current design codes have to be improved for the design of structural concrete subjected to complex loading and geometrical conditions because of the uncertainties in the selection of strut-tie model, in the use of an indeterminate strut-tie model, and in the effective strengths of struts and nodal zones. To improve the uncertainties, a grid struttie model approach is proposed in this study. The proposed approach, allowing to perform a consistent and effective design of structural concrete, employs an initial grid strut-tie model in which various load combinations can be considered. In addition, the approach performs an automatic selection of an optimal strut-tie model by evaluating the capacities of struts and ties using a simple optimization algorithm. The validity and effectiveness of the proposed approach is verified by conducting the analysis of the four reinforced concrete deep beams tested to failure and the design of shearwalls with two openings.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.12 no.4
• /
• pp.19-33
• /
• 2008

Dynamic response measurements from natural excitation were carried out for 25- and 42-story buildings to evaluate their inherent properties, such as natural frequencies, mode shapes and damping ratios. Both are reinforced concrete buildings adopting a core wall, or with shear walls as the major lateral force resisting system, but frames are added in the plan or elevation. In particular, shear walls in a 25-story building are converted to frames from the 4th floor level downwards while maintaining a core wall throughout, resulting in a fairly complex structure. Due to this, along with similar stiffness characteristics in the principal directions, significantly coupled and closely spaced modes of motion are expected in this building, making identification rather difficult. By using various state-of-the-art system identification methods, the modal parameters are extracted, and the results are then compared. Three frequency-domain and four time-domain based operational modal identification methods are considered. Overall, all natural frequencies and damping ratios estimated from the different identification methods showed a greater consistency for both buildings, while mode shapes exhibited some degree of discrepancy, varying from method to method. On the other hand, in comparison with analysis results obtained using the initial finite element(FE) models, test results exhibited a significant difference of about doubled frequencies, at least for the three lower modes in both buildings. To improve the correlation between test and analysis, a few manual schemes of FE model updating based on plausible reasons have been applied, and acceptable results are obtained. The advantages and disadvantages of each identification method used are addressed, and some difficulties that might arise from the updating of FE models, including automatic procedures, for such large structures are carefully discussed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.3
• /
• pp.88-98
• /
• 2011

Masonry structure is a style of building which has been widely applied as residential facilities of low and middle stories, commercial and public facilities etc. But it is possible to destroy by loss of adhesive strength or sliding when lateral forces, such as earthquake, occurs. This study proposes a seismic retrofit method for masonry structure and its seismic performance is demonstrated by shaking table test. Two specimens per each shaking direction were made, having out-of-plane(weak axis) and in-plane(strong axis) direction. External load of 1 ton was also applied for each specimen during the test, to model the behavior of reinforced masonry wall. As a result of shaking table tests, it is shown that the specimen applying the proposed seismic retrofit method showed acceptable behaviors in both of Korea building design criteria(0.14g) and USA seismic criteria suggested by IBC(0.4g). However, it was observed that stiffness of the specimen toward out-of-plane was rapidly decreasing when seismic excitations over 0.14g were loaded. In comparison of relative displacements, maximum relative displacement of specimens which were accelerated toward out-of-plane with 0.4g at once was 29~31% of maximum relative displacement when specimens were gradually accelerated from 0.08g to 0.4g, while the maximum relative displacement of specimens accelerated toward in-plane has similar value in both cases. Therefore, it is concluded that the wall accelerated toward out-of-plane is more affected by hair crack or possible fatigues caused by seismic excitation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.76-79
• /
• 2004

The use of recycled aggregate concrete is increasing faster than the development of appropriate design recommendations. This paper is making advances in the recycling of waste concrete material for use as recycled aggregate to make secondary concrete product. Using recycled aggregates from demolished concrete, we manufactured concrete blocks to experiment overall performance in feasible performances. This paper reports limited experimental data on the structural performance of shear wall used concrete blocks made in recycled aggregates. Reinforced concrete frame and shear walls were tested to determine their diagonal cracking and ultimate shear behavior. The variable in the test program was the existence of infilled wall used concrete blocks Made in recycled aggregates. Based on the experimental results, Infilled wall has a high influence on the maximum strength and initial stiffness of reinforced concrete frame. Structural performance of specimen WSB1 and WSB2 is quite different from RCF specimen, particularly strength, stiffness and energy dissipation capacity.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.403-408
• /
• 2003

The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.