• Journal of the Korea institute for structural maintenance and inspection
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• 제21권2호
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• pp.138-145
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• 2017

The purpose of this study is to establish a reasonable analytical method for the estimation of overall behavior characteristic from cracking to yielding of rebar and crushing of concrete and seismic performance of reinforced concrete shear wall with high-strength reinforcing bar. A total of 8 specimens of reinforced concrete walls which have constant aspect ratio and a variety of variables such as reinforcement ratio, reinforcement yielding strength, reinforcement details, concrete design strength, section shape and whether lateral restraint hoop were selected and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the proposed constitutive equation by the authors. The mean and coefficient of variation for maximum load from the experiment and analysis results was predicted 1.04 and 8%. The mean and coefficient of variation for displacement corresponding maximum load from the experiment and analysis results was predicted 1.17 and 19% respectively. The analytical results were predicted relatively well the fracture mode and the overall behavior until fracture for all specimens. These results are expected to be used as basic data for application of high-strength reinforcing bar to design codes in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• 제20권6호
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• pp.46-55
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• 2016

Three small scale hollow circular reinforced concrete columns(4.5 aspect ratio) were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable are transverse steel ratio. Volumetric ratio of spirals of all the columns is 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The final objectives of this study are to provide quantitative reference data and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, steel fracture, etc. In this paper, describes mainly failure behavior, strength degradation behaviour, displacement ductility of circular reinforced concrete bridge columns with respect to test variables.

• Journal of the Korea institute for structural maintenance and inspection
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• 제17권2호
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• pp.71-82
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• 2013

Eight small scale circular reinforced concrete columns (4.5 aspect ratio) were tested under cyclic lateral load with constant axial load. The selected test variables are longitudinal steel ratio (2.017%, 3.161%), transverse steel ratio, and axial load ratio (0, 0.07, 0.15). Volumetric ratio of spirals of all the columns is 0.335~0.894% in the plastic hinge region. It corresponds to 39.7~122.3% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The final objectives of this study are to provide quantitative reference data and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, steel fracture, etc. In this paper, describes mainly failure behavior, strength degradation behaviour, displacement ductility of circular reinforced concrete bridge columns with respect to test variables.

• Journal of the Korea Concrete Institute
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• 제15권2호
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• pp.323-334
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• 2003

For performance-based design using nonlinear static analysis, it is required to predict the inelastic behavior of structural members accurately. In the present study, a nonlinear numerical analysis was peformed to develop the method describing the moment-curvature relationship of structural wall with boundary confinement. Through the numerical analysis, variations of behavioral characteristics and failure mechanism with the arrangement of vertical reinforcement and the length of boundary confinement were studied. According to the analysis, the maximum moment-carrying capacity of structural walls with adequately confined boundary elements is developed at the moment the unconfined concrete reaches the ultimate compressive strain. Walls with flexural re-bars concentrated on the boundaries fails in a brittle manner. As vortical re-bars in the web increases, the brittle failure is prevented and a ductile failure occurs. Based on the findings, moment-curvature curves for walls with a variety of re-bar arrangement were developed. According to the proposed relationships, deformability of the structural walls wth boundary confinement increases as the compressive strength of the confined concrete increases compared to the applied compressive force.

• Journal of the Korea Concrete Institute
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• 제13권6호
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• pp.544-552
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• 2001

Korea is classified into low and moderate seismic zone from the view-point of seismic hazard level. Korean seismic provisions has been developed based on UBC and ATC 3-06. Thus, in calculation of design base shear according to Korean provisions response modification factor (R) is included in the formula of design base shear. The major role of this factor is to reduce the elastic design base shear whereby structures can behave in inelastic range during design level earthquake ground motions(mean return period of 475 yrs.). R factor is assigned according to material and structural systems. In this study, R factor for bearing wall system is considered. Most of the walls of apartment buildings in Korea resist gravity and seismic loads simultaneously so that this wall system can be classified into bearing wall system. Structural details of these walls are different from those used in Japan and U.S.. They are all rectangular in sectional shape rather than barbell in shape, and also have special lateral reinforcement details at the boundaries of a wall. In Korean seismic design provisions(1988), two different values(3.0 and 3.5) of R factor are assigned to the bearing wall systems according to the wall details. However, in updated seismic provisions(2000), only one value is assigned to R factor(3.0) irrespective of wall details. In this study, the design base shear values in Korean seismic design provisions(1988, 2000), ATC 3-06, UBC are compared. Also experimental study was carried out to evaluate the seismic performance of structural walls. For this purpose, five test specimens were made which have special details used in apartment bearing wall systems in Korea. Based on the results of this study, response modification factor for bearing wall system is discussed.

• Magazine of the Korea Concrete Institute
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• 제4권1호
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• pp.135-145
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• 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 Engineering Geology
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• 제15권3호
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• pp.309-323
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• 2005

Dynamic stiffness of subsurface materials is one of the most important geotechnical parameters in predicting deformational behavior of structures as well as practicing seismic design and performance evaluation. In an effort to measure the parameter efficiently and accurately, various borehole seismic testing techniques have been, thus, developed and used during past several decades. Moreover, recent rush of underground-space projects and increasing size of structures put more stress on reliable site investigation techniques in estimating stiffness of rock mass. In this paper, a new technique called 'in-hole seismic test' has been implemented to measure the dynamic stiffness of rock masses at subsurface foundations and tunnel-faces. The reliance of in-hole seismic test was evaluated by comparing the testing results at several rock sites with those of other borehole techniques and the technique tunnls out to be an efficient and accurate in-situ testing technique.

• Journal of Korean Society of Steel Construction
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• 제15권4호통권65호
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• pp.359-368
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• 2003

Design and detailing requirements of seismic provisions for Concentrically Braced Frames (CBF) were specified based on the premise that bracing members with large KL/r and low b/t have superior seismic performance. However, relatively few tests have been done to investigate the cyclic behavior of CBF. Therefore, the question lies on whether the compression member of CBF plays as significant a role as what has been typically assumed by design providers. In this paper, existing experimental data were reviewed to quantify the extent of hysteretic energy achieved by bracing members in past compression tests as well as the extent of degradation of the compression force given repeated cycling loading.

• Journal of Korean Society of Steel Construction
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• 제20권6호
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• pp.691-700
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• 2008

Contemporary architectural structures have diverse and complex forms. Such structural variety demands requisite performance from the connections in the steel structure so that the latter could resist a horizontal force, such as an earthquake. The connections are the all-important components that create the discontinuous form and that support stress concentration, determining the stiffness and toughness of the entire steel frame. In this study, a real-scale column-to-beam connection was constructed in the 600MPa-grade high-strength and high-performance steel, to test its behavior. Its material and welding characteristics were examined in this study, and its structural performance was analyzed by conducting seismic-resistance tests on the full-scale, cross-shaped column-to-beam welded connections with non-scallop, ordinary-scallop, and reinforced-scallop details. The weld ability of the high-strength, high-performance steel was also evaluated, and data regarding the seismic design for practical application were provided.

• Journal of the Earthquake Engineering Society of Korea
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• 제6권4호
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• pp.65-73
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• 2002

It has been recognized that the damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear time history analyses, monotonic static nonlinear analyses, or equivalent static analyses with simulated nonlinear influences. Some building codes propose the capacity spectrum method based on the nonlinear static analysis(pushover analysis) to determine the earthquake-induced demand given by the structure pushover curve. These procedures are conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) systems. The purpose of this paper is to investigate the accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters. The conclusions of this study are as follows; 1) NDSM is considered as practical method because the peak deformations of nonlinear system of MDF by NDSM are almost equal to the results of nonlinear time history analysis(NTHA) for various ground motions. 2) When the results of NDSM are compared with those of NTHA. mean of errors is the smallest in case of post-yielding stiffness factor 0.1, static force by MAD(modal adaptive distribution) and unloading stiffness degradation factor 0.2~0.3.