• Magazine of the Korea Concrete Institute
• /
• v.4 no.1
• /
• pp.135-145
• /
• 1992

With the increasing tendency to construct high rise reinforced concrete building~i, it is required to use high strength materIals, smaller member sections, and larger reinforcing bars, I t is generally recognized that under severe seismic loads beam column jomts may become more critical structural components than other structural elements. In a ductile momentresistmg reinforced concrete frame, the connection of bearncolumn must be capable of resistll1g the large lateral forces caused by seismic actions, The purpose of this experimental study is to evaluate and ll1vestigate the earthquake resistant perform ance of beam-colurrm subassemblies constructed with high-strength concrete cast by the concrete of com¬pressive strength of 700kg / cm2 subjected to reversed cyclic loadings. New approaches for moving the plastic hinging zone away from the column face and preventing the di¬agonal crack in the joint region are adopted to advance the earthquake-resistant performance of beam-column subassemblies using high-strengh concrete under severe earthquake-type loading. Exper¬imental results indicate that the modified new details which are introduced by intermediate reinforcement in the beam over a specific beam length adjacent to the joint are able to attain the stable hysteretic behavior and the enhancement of earthquake-resistant performance. Keywords: high strength concrete: beam-column Joints; seirnic loads(reversed cyclic loading) : earth¬quake-resistant performance; plastic hinge zone: diagonal crack: intermediate reinforce¬ment ; closed strirrup: hysteretic behavior: enhancement .

• The Journal of the Petrological Society of Korea
• /
• v.9 no.4
• /
• pp.254-270
• /
• 2000

To clarify the geological structure of North Sobaegsan Massif in the Sangunmyeon area, Bonghwagun, Korea, where the Yecheon Shear Zone passes and the NE-SW and E-W trending structural lineaments are developed, the rock-structures of its main constituent rocks(Precambrian Won-nam Formation and Mesozoic Hornblende Granite) were examined. In this area, the geological structure was formed at least by four phases of deformation after the formation of gneissosity or schistosity of the Wonnam Formation: one deformation before D2 ductile shearing related to the for-mation of the Yecheon Shear Zone and two deformations after that. The NE-SW and E-W trending structural lineaments were formed by a giant open or gentle type of F4 fold, and their trends before D4 deformation are interpreted to be parallel to the orientation(ENE-WSW trend) of folded surface in the F4 hinge zone. The structural features of Dl-D3 deformations and their relative occurrence times are as follows. Dl deformation is formative period of the boudin structures and ENE-WSW trending isoclinal folds with sub-horizontal hinge lines and steeply inclined axial surfaces. D2 deformation is that of the mylonite foliation, stretching lineation and Z-shaped asymmetric folds related to top-to-the ENE dextral strike-slip shearing on the distinct foliations of Wonnam Formation(after intrusion of Mesozoic Hornblende Granite). D3 deformation is that of the ENE trending S-shaped asymmetric folds with sub-horizontal hinge lines and axial surfaces related to normal-slip shearing on the distinct foliations. It is expected that the result will be contributed to as valuable data for interpreting the tectonic evolution of the North Sobaegsan Massif and the Northeast Ogcheon Belt whose tectonic lineaments are changed from NE-SW to E-W trends at the Sindong-Bonghwa line.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.559-564
• /
• 2001

The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo-dynamic test has been done for two nonseismic test specimens which were nonseismic designed by the related provisions of the Highway Design Specification, and four nonseismic test specimens retrofitted with fibers in the plastic hinge region. Important test parameters were load patterns, and retrofit. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.0 displacement ductility was observed for nonseismic test specimens retrofitted with fibers. It is concluded that these retrofitting test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1989.10a
• /
• pp.77-82
• /
• 1989

In this paper an experimental approach of the relocation plastic hinging zones of nine reinforced concrete exterior beam-column subassemblages under cyclic loads was tried. The main parameters of the testing program were location of the plastic hinge, difference of the special reinforcement, inclined or intermediate layers of longitudinal reinforcement, applied maximum shear stress. The conclusions presented herein are based on the limited texts conducted. Inclined or intermediate layers of longitudinal reinforcement and extra top and bottom steel in the beam over a specific legnth can be used to move the beam plastic hinging zone away from the column face. But, for the use of intermediate layers of longitudinal reinforcement, sheat reinforcement detail need further investigation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.879-884
• /
• 2002

The objective of this study is to investigate the seismic capacity of the non-seismically detailed RC bridge piers before and after applying a seismic retrofitting method using stainless steel wire mesh. Total nine circular section RC piers were constructed. Different lap splice longitudinal reinforcement details were adapted for four specimens and various types of stainless steel wire mesh were applied for the remaining five specimens. Harmonic cyclic lateral load was applied on each specimen under a constant axial load. The test results indicated that the existing circular piers have low seismic capacity while the stainless steel wire mesh retrofitting method improves the seismic capacity considerably. In addition, test results revealed that the circular section piers could have a considerable amount of ductility if longitudinal bars are not lap-spliced in potential plastic hinge zone. Based on this experimental study it could be concluded that the seismic performance, that is ductility and energy absorption capacity, of the non-seismically detailed RC bridge piers would be increased by applying the stainless steel wire mesh seismic retrofitting method.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.464-469
• /
• 2000

Since the occurrence of 1995 Kobe earthquake, there have been much concern about seismic design for various infrastructures, inclusive of bridge structures. This research aims at evaluating the seismic performance of the existing R/C bridge piers, which were nonseismically or seismically designed in accordance with the provision of Korea Highway Design Specification. Further experimental investigations have been doing to figure out the retrofitting effects of nonseismic R/C bridge piers confined with glass fiber at the plastic hinge zone. Pseudo-dynamic tests have been carried out in nine scaled R/C column specimens to investigate their hysteretic behavior under earthquake loading. Test parameters are axial load, input ground motion confinement steel ratio, glass fiber and etc.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.4 s.37
• /
• pp.629-639
• /
• 1998

This paper summarizes the results of full-scale cyclic seismic performance tests on three column-tree type steel moment connections. Each test specimen consisted of a $H-600{\times}200$ beam and a $H-400{\times}400$ column of SS41 (SS400). Key parameter included was column PZ (panel zone) strength relative to beam strength. The seismic performance of specimen with stronger PZ tended to be inferior. Total plastic rotations available in the specimens ranged from 1.8 to 3.0 (% rad). The limited test results in this study seem to support the speculation that permitting PZ yielding shall be more beneficial to enhancing total plastic rotation capacity of the moment connection. Beam flange fracture across the heat affected zone and divot-type pullout of the column flange were observed in the tests. A conceptual mechanical model consistent with observed test results was also sought.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.4
• /
• pp.169-179
• /
• 1995

The purpose of this study is to spread beam plastic hinging zone of the high-strength($f'_c=700kg/cm^2$) reinforced concrete beam-column joints away from the column face by vertically anchored intermediate reinforcements. The newly proposed intermediate reinforcements which are vertically anchored by interlinking each intermediate rebars are tested to insure the ductile behavior of R /C beam-column joins. Main variable is the shape of intermediate reinforcements. From the test results, the newly proposed intermediate rebar detail can move arid expand the beam plastic hinging zone about 1.Od from column face and can delay the strength decay of the high-strength R /C beam-column joint. Also energy dissipation capacity of specimen IV-1.OD10 which is reinforced by vertically anchored intermediate rebars about 1.0d is 1.6 times as high as the specimen CM-STAN which is designed by ACI318-89.

• Earthquakes and Structures
• /
• v.9 no.4
• /
• pp.831-849
• /
• 2015

Seismic-design procedures for walls require that the confinement in the critical (plastic hinge) regions should extend over a length in the compression zone of the cross section at the wall base where concrete strains in the Ultimate Limit State (ULS) exceed the limit of 0.0035. In a performance-based framework, confinement is linked to required curvature ductility so that the drift demand at the performance point of the structure for the design earthquake may be met. However, performance of flexural walls in the recent earthquakes in Chile (2010) and Christchurch (2011) indicates that the actual compression strains in the critical regions of many structural walls were higher than estimated, being responsible for several of the reported failures by toe crushing. In this study, the method of estimating the confined region and magnitude of compression strain demands in slender walls are revisited. The objective is to account for a newly identified kinematic interaction between the normal strains that arise in the compression zone, and the lumped rotations that occur at the other end of the wall base due to penetration of bar tension yielding into the supporting anchorage. Design charts estimating the amount of yield penetration in terms of the resulting lumped rotation at the wall base are used to quantify the increased demands for compression strain in the critical section. The estimated strain increase may exceed by more than 30% the base value estimated from the existing design expressions, which explains the frequently reported occurrence of toe crushing even in well confined slender walls under high drift demands. Example cases are included in the presentation to illustrate the behavioral parametric trends and implications in seismic design of walls.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.4
• /
• pp.83-95
• /
• 2001

Scale model tests were performed to investigate the seismic behavior and capacity of reinforced concrete piers that were not detailed for seismic load. The prototype pier is of solid circular section. Additional lateral reinforcing bars were not provided that might be required for the confinement. Two kinds of reinforcement details are considered for the vertical longitudinal reinforcing bars: lap spliced and continuous. In the case of lap spliced model all the longitudinal bars were lap spliced at the same height in the bottom plastic hinge zone. Three specimens were constructed and subjected to quasi-static cyclic lateral loading while the vertical load held constant. Non-ductile failure modes were observed in the test of lap spliced models but limited ductile behavior was observed in the test of a continuous longitudinal reinforcement model.