• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.88-97
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• 2012

The objective of this research is to investigate the seismic performance and flexure-shear behavior of square reinforced concrete bridge piers with solid and hollow cross section. Test specimens were nonseismically designed with the aspect ratio 4.5 Two reinforced concrete columns were tested under constant axial load while subjected to lateral load reversals with increasing drift levels. Longitudinal steel ratio was 2.217 percent. The transverse reinforcement ratio As/($s{\cdot}h$), corresponding to 58 percent of the minimum lateral reinforcement required by Korean Bridge Design Specifications for seismic detailing, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. This study are to provide quantitative reference data for the limited ductility design concept and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, collapse, etc. Failure behavior, ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio, residual deformation, effective stiffness, plastic hinge length, strain of reinforcements and nonlinear analysis are investigated and discussed in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.1-8
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• 2006

Nonseismic designed RC frame have a possibility of shear failure because of deficiencies of reinforcing details. To model the shear failure in numerical analysis, shear strength degradation models which Include Moehle's and ATC 40 are compared and applied to push-over analysis. For numerical analysis, three storied building frame is selected and designed according to Korean Concrete Design Code(2003). As results, It is shown that Moehle's shear strength degradation model estimates the shear strength lower than NZSEE model and has less variation than ATC 40 model and all the shear strengths of models are greater than the nominal shear strength of ACI 318. Also, from the numerical analysis, it is pointed out that there may be great difference in lateral drift capacity if a different shear strength model is used. And the capacity can be severely underestimated if the restraining model of plastic rotation of ATC 40 is used, compared to the use of shear spring model for shear degradation.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.727-734
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• 2005

High-rise residential buildings these days tend to adopt a building frame system as primary earthquake resisting structural system for some architectural reasons. But there exist several ambiguities in designing such building frame systems according to current codes with regards to : the effective stiffness property of RC cracked section in static and dynamic analyses, analytical model to evaluate story drift ratio, and deformation compatibility requirements of frames. The comparative study for these issues by appling KBC 2005 to a typical building frame system shows that demands of member strength and story drift ratio can be different significantly depending on engineer's Interpretation and application of code requirements. And a building frame system can be noneconomical, compared with the dual system, because of higher demands on strength or ductility in both frames and shear walls.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.27-35
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• 2005

Several damages due to large displacement caused by liquefaction have been reported increasingly. Numerical procedures based on effective stress analysis are therefore necessary to predict liquefaction-induced deformation. In this paper, the fully coupled effective stress model called UBCSAND is proposed to simulate pore pressure rise due to earthquake or repeated loadings. The proposed model is a modification of the simple perfect elasto-plactic Mohr-Coulomb model, and can simulate a continuous yielding by mobilizing friction and dilation angles below failure state. Yield function is defined as the ratio of shear stress to mean normal stress. It is radial lines on stress space and has the same shape of Mohr-Columob failure envelope. Plastic hardening is based on an isotropic and kinematic hardening rule. The proposed model always causes plastic deformation during loading and reloading but it predicts elastic unloading. It is verified by capturing direct simple shear tests on loose Fraser River sand.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.79-86
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• 2008

Four RC shear wall specimens with a/d of 2.2 are designed. And a flexural retrofitting is performed for one specimen by both enlarging wall section and adding additional vertical reinforcements. Also the effectivity of jaketting wall sides is evaluated for the two methods using only steel plate or welded wire mesh with enlargement of section. Cyclic loads are applied to the retrofitted specimens according to the loading history proposed by ACI under constant axial force. Test result showed that the strength and ductility of specimen were improved where the section was enlarged after the installation of additional vertical reinforcements. Confining the ends of wall by U shape W.W.F. with enlargement of section showed most excellent structural capacity regarding to the strength and ductility. Retrofitting by using steel plate was much effective not only to protect the abrupt decrease of strength after yield but also to improve the deformation capacity.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.335-343
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• 1998

Recently, new experimental criteria for reinforced concrete frame structures in high seismic regions have been reported in United States. The objective of the criteria is to get more reliable test data which are valid to compare with other test data done by different researchers. The criteria precribe test method of specimens, analysis method of test data, and limiting values needed to specimens like drift angle, energey dissipation ratio, stiffness, and strength. These criteria might be usefel to get objective conclusion. Shear wall structures, which belong to one of earthquake resisting systems, also need this kind of criteria. But, the general response of shear wall structures is a little bit different from that of frame structures since shear wall restrains the horizontal displacement caused by horizontal force and increases the stiffness and strength. The objective of this paper is to propose a criterion for limiting drift and energy dissipation ratio of shear walls based on structural testing. These are the most important values for presenting the capacity of shear walls. Limiting drift and energy dissipation ratios were examined for tests on shear walls having ductile type failures. Test data were analyzed and compared to the results for a suggested acceptance criteria that involve a limiting drift that is a function of aspect ratio and a limiting energy dissipation ratio that is a function of displacement ductility and damping.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.147-157
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• 2018

The basis of capacity design has been explicitly or implicitly regulated in most bridge design specifications. It is to guarantee ductile failure of entire bridge system by preventing brittle failure of pier members and any other structural members until the columns provides fully enough plastic rotation capacity. Brittle shear is regarded as a mode of failure that should be avoided in reinforced concrete bridge pier design. To provide ductility behavior of column, the one of important factors is that flexural hinge of column must be detailed to ensure adequate and dependable shear strength and deformation capacity. Eight small scale circular reinforced concrete columns were tested under cyclic lateral load with 4.5 aspect ratio. The test variables are longitudinal steel ratio, transverse steel ratio, and axial load ratio. Eight flexurally dominated columns were tested. In all specimens, initial flexural-shear cracks occurred at 1.5% drift ratio. The multiple flexural-shear crack width and length gradually increased until the final stage. The angles of the major inclined cracks measured from the vertical column axis ranged between 42 and 48 degrees. In particular, this study focused on assessing transverse reinforcement contribution to the column shear strength. Transverse reinforcement contribution measured during test. Each three components of transverse reinforcement contribution, axial force contribution and concrete contribution were investigated and compared. It was assessed that the concrete stresses of all specimen were larger than stress limit of Korea Bridge Design Specifications.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.99-107
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• 1997

A mixed type finite element method is applied to the nonuniform shear warping beam theory which is very useful for the structural analysis of thin-walled sectional beams considering the shear deformation. As known generally, it is shown that the mixed type finite element method, compared with the displacement type one, can give more balanced accuracy of results in calculating the stresses and displacements of the structure. In this paper, one typical example, the flexural-torsional problem of a discontinuously variable sectional beam under coupled end torsional moments, is selected and analyzed to validate the usefulness of the developed beam element.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.231-237
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• 2004

Most of the masonry buildings have many structural defects under an earthquake load due to the small tensile force and ductility. In the foreign countries there are many the reinforcing methods of masonry buildings, but the glass fiber sheet reinforcements must be used due to various conditions in Korea. The purpose of this paper is to estimate the seismic capacity of masonry buildings damaged by earthquake and reinforced by Glass Fiber Sheet. On the basis of test results, the maximum base shear force and deformation of the masonry building with GFS were remarkably increased. From the comparison by existing strength equations and test data, the new strength equation of reinforced masonry buildings with GFS was developed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.71-80
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• 2007

Because of the characteristics relating to high tensile ductility, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) are studied to be adopted in repair and retrofit of buildings. A series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral loading in order to evaluate the seismic retrofit that had been proposed for the shear wall with the opening. The retrofit involved the use of newly developed ECC and MDF(Macro Defect Free), both of which are sprayed through the high pressure pump, over the entire face of the wall. The results indicate that two difference types of retrofitting strategy make the different effects of a rise in the strength and ductility of each specimen.