• Journal of the Korean Society for Advanced Composite Structures
• /
• v.2 no.4
• /
• pp.28-34
• /
• 2011

Because strong urban earthquakes must produce huge losses of both life and property, examinations about the effect of huge earthquakes for tall buildings are very required. The goal of this report is examining model safety and compare the behavior of 2-D tall models under huge seismic loads. This report examines high-rise models designed KBC2009 codes using 1) seismic loads regulated by KBC2009 and 2) amplified seismic loads assumed to strong earthquakes. And observing for more realistic behavior of tall buildings under huge earthquakes, this report takes two analysis methods - response spectrum analysis and non-linear time history analysis considering P-delta effect.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.3
• /
• pp.327-335
• /
• 2011

This study has two objectives: (1) to evaluate the degradation characteristics of symmetric unbraced steel frames by using analytical approach, and (2) to suggest equation which can approximately estimate the effect of degradation during the schematic design stage. For the analytical approach, the refined plastic hinge method with an arc length algorithm was adopted. The subject of analysis was one story one-bay, multistory one-bay, and multistory three-bay unbraced steel frames. The main parameters of the analytical approach include the stiffness ratio of column to beam and the axial force ratio. The study led to the following conclusions. The normalized stiffness of degradations is affected by both stiffness ratio of column to beam and the axial load ratio; however, the major influence on degradations is the axial force ratio. The equation, which can approximately estimate the effect of degradation, was suggested together with the research results.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.5
• /
• pp.27-33
• /
• 2010

In this study, a monotonic loading test to estimate structural capacity of 12 meter long full scale precast pre-stressed concrete beam specimen was performed with a 2,000 kN dynamic actuator. A couple of embedded steel plate was installed at the ends of the beam and specimens were connected to steel girder frame with high tension bolts. Nominal compressive strength of pre-stressed concrete beam and slab were 50 MPa and 24 MPa respectively. Two HD25 tensile steel reinforcements were welded on vertical plate of embedded steel plate. Pre-stressed concrete beam specimen was loaded by displacement control method with a certain loading pattern which was repeated loading and unloading with 10mm increment displacement. About 88.34%, 86.97% and 66.83% of displacement restoration ratios were evaluated at elastic, inelastic and plastic behavior region of specimen respectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.2 no.3
• /
• pp.1-13
• /
• 1982

Transition process of plastic region. displacements, stresses and strains ahead the flaw tips were analysed by the finite element method on the steel plate with the circular hole and the one with the elliptical hole under completely alternating load (repetition of tensile loading, unloading and compressive loading). As the results, the followings were obtained. Transition process of elastic failure (yielding) region was estimated. From this the tendency was confirmed that the fracture would be initiated from ahead the flaw tip, and propagated along the $45^{\circ}$ direction. The fundamental data available in estimating the stress intensity factor that was considered as the core in analysing the fracture mechanism of steel plates were obtained. It was indicated that when unloading after tension the effect of compressive loading, and even the compressive reyield, was occured ahead the flaw tip. Similarly it was indicated that when unloading after compression the effect of tensile loading, and even the tensile reyield, was occured ahead the flaw tip. It was considered that these phenomena were occured because the unloading effect was constrained by the residual strains when unloading. It was considered that the fatigue phenomenon was occured ahead, the flaw tip by repetition of tensile yield, the above compressive reyield, compressive yeild and the above tensile reyield. In addition, the tendency was confirmed that the fracture ahead the flaw tip was occured as the flaw was changed from the circular hole to the elliptical hole and became to be the crack lastly.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.3
• /
• pp.53-64
• /
• 2003

Many transmission towers, high-rise buildings and bridges are constructed near steep slopes and are supported by large-diameter piles. These structures may be subjected to large lateral loads, such as violent winds and earthquakes. Widely used types of foundations for these structures are pier foundations, which have large-diameters with high stiffness. The behavior of a pier foundation subjected to lateral loads is similar to that of a short rigid pile because both elements seem to fail by rotation developing passive resistance on opposite faces above and below the rotation point, unlike the behavior of a long flexible pile. This paper describes the results of several numerical studies performed with a three-dimensional finite element method (FEM) of model tests of a laterally loaded short pile located near slopes, respectively. In this paper, the results of model tests of single piles and pile groups subjected to lateral loading, in homogeneous sand with 30$^{\circ}$ slopes and horizontal ground were analyzed by the 3-D FE analyses. The pile was assumed to be linearly elastic. The sand was assumed to have non-associative characteristics, following the MC-DP model. The failure criterion is governed by the Mohr-Coulomb equation and the plastic potential is given by the Drucker-Prager equation. The main purpose of this paper is the validation of the 3-D elasto-plastic FEM by comparisons with the experimental data.

• Clinical and Experimental Pediatrics
• /
• v.52 no.4
• /
• pp.464-470
• /
• 2009

Purpose : This study assessed the incidence and outcome of congenital anomalies of the kidney and urinary tract (CAKUT) detected by prenatal ultrasonography Methods : There were 906 cases of CAKUT detected by prenatal ultrasonography and postnatally confirmed at the Asan Medical Center from October 1989 to October 2007. We investigated the incidence and outcome of these cases by reviewing medical records retrospectively. Results : The order of incidence was hydronephrosis, multicystic dysplastic kidney (MCDK), duplex kidney, vesico-ureteral reflux (VUR), single kidney, hydroureteronephrosis, ectopic kidney, polycystic kidney, ureterocele, and posterior urethral valve (PUV). There were 520 cases (57.4%) of hydronephrosis, and 20% of these needed an operation due to significant obstruction. MCDK was associated with other CAKUT in 25.4% of all cases. Approximately 57.9% of duplex kidney cases needed surgical treatment due to ureterocele and VUR. VUR had a male: female ratio of 10:1. Two out of seven cases of autosomal recessive polycystic kidney had progressed to chronic renal failure. Patients with PUV were relatively uncommon, and one out of nine cases progressed to end-stage renal disease. Conclusion : CAKUTs detected by prenatal ultrasonography were composed of various anomalies, and almost all of them had a good outcome without any intervention. However, in some cases, recurrent urinary tract infection or renal failure occurred, especially in bilateral cases. For further management, a long-term multicenter study is needed to investigate the precise incidence and outcome of each anomaly in the general population.