• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.48-56
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• 2021

Due to the recent earthquake that has occurred worldwide, interest in seismic reinforcement of structures is increasing. In order to improve the seismic performance of the structure, the seismic reinforcement of the column should be made. Various seismic retrofit methods are being developed to improve the seismic performance of columns. In this study, in order to improve the seismic performance of RC columns, an numerical study was conducted to evaluate the seismic performance of the columns by applying a surface constrained pressure. For the numerical study, the experimental study on the column was used, and the failure shape and behavior characteristics of the experimental results and the numerical results were compared. As a result of the numerical study, the ductile behavior of the RC columns occurred according to the strength of the surface constraining stress. In addition, ductile behavior occurred almost constant above a certain surface constrained pressure. Compared with the numerical results and the experimental results, he reinforcing effect of the used seismic reinforcement of the column in experimental study was compared with the value of the surface constrained pressure for the RC column, and the seismic reinforcing effect was examined as the surface constrained pressure value for the RC column. In conclusion, in this work, surface constrained stress and constrained strength for ductile behavior of RC columns are derived. Based on the results derived, it is believed that it can be used as basic data on the review of seismic design methods and seismic performance complementary effects using ductile behavior induction of RC columns.

• Structural Engineering and Mechanics
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• v.18 no.5
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• pp.645-669
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• 2004

In seismic analysis of moment-resisting frames, beam-column connections are often modeled with rigid joint zones. However, it has been demonstrated that, in ductile reinforced concrete (RC) moment-resisting frames designed based on current codes (to say nothing of older non-ductile frames), the joint zones are in fact not rigid, but rather undergo significant shear deformations that contribute greatly to global drift. Therefore, the "rigid joint" assumption may result in misinterpretation of the global performance characteristics of frames and could consequently lead to miscalculation of strength and ductility demands on constituent frame members. The primary objective of this paper is to propose a rational method for estimating the hysteretic joint shear behavior of RC connections and for incorporating this behavior into frame analysis. The authors tested four RC edge beam-column-slab connection subassemblies subjected to earthquake-type lateral loading; hysteretic joint shear behavior is investigated based on these tests and other laboratory tests reported in the literature. An analytical scheme employing the modified compression field theory (MCFT) is developed to approximate joint shear stress vs. joint shear strain response. A connection model capable of explicitly considering hysteretic joint shear behavior is then formulated for nonlinear structural analysis. In the model, a joint is represented by rigid elements located along the joint edges and nonlinear rotational springs embedded in one of the four hinges linking adjacent rigid elements. The connection model is able to well represent the experimental hysteretic joint shear behavior and overall load-displacement response of connection subassemblies.

• Journal of the Korean Institute of Gas
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• v.18 no.1
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• pp.41-45
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• 2014

This paper presents an analytical study on the displacement behavior safety of cylindrical hollow rollers. Using the finite element method, the hollow roller with Y-shaped column structures between three tubes has been developed to analyze the displacement behavior safety. For the same dimension and weight of two hollow roller models, the displacement behavior safety of a typical hollow roller is lower 4~6.6% than that of the newly designed hollow roller with Y-shaped column structures between three tubes. Thus, this paper recommends Y-shaped hollow roller for increasing the roller strength safety and decreasing a total roller weight, which may save a consuming electrical energy.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.324-333
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• 2009

This paper presents a numerical simulation study of the transient behavior of a $2{\times}340MW$ pump-turbine power plant, where the results show an unstable behavior at runaway. First, the modeling of hydraulic components based on equivalent schemes is presented. Then, the 2 pump-turbine test case is presented. The transient behavior of the power plant is simulated for a case of emergency shutdown with servomotor failure on Unit 1. Unstable operation at runaway with a period of 15 seconds is properly simulated using a 1-dimensional approach. The simulation results points out a switch after 200 seconds of the unstable behavior between a period of oscillations initially of 15 seconds to a period of oscillation of 2.16 seconds corresponding to the hydraulic circuit first natural period. The pressure fluctuations related to both the rigid and elastic water column mode are presented for oscillation mode characterization. This phenomenon is described as a switch between a rigid and an elastic water column oscillation mode. The influence of the rotating inertia on the switch phenomenon is investigated through a parametric study.

• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.67-76
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• 2011

Column base is very important part of steel structure because it transmits load to foundation in structure. Column base which is used frame construction in the inside and outside of the country is distributed into exposed-type, concrete encased and imbeded-type. Exposed-type column base is most profitable, if consider reuse and recycle of elements first of all. In this study, we proposed a new style exposed-type column base improved in performance for construction work and mechanical performance.

• Earthquakes and Structures
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• v.3 no.1
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• pp.37-57
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• 2012

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1132-1143
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• 2008

A single Column/Shaft which extended the pile to the column of the bridge with same diameter has better safety and economical profit, but it usually has larger lateral displacement due to lateral loads such as wind, earthquake, wave, etc. A series of horizontal pile load testing were performed to study the lateral behavior of single column/shaft with varying different free lengths and embedded pile lengths. Eight instrumented test piles were cast-in-placed by bonding strain gauges at certain locations on both faces of the pile to measure bending moment, from two-way loadings. Linear variable differential transformers(LVDTs) were installed to measure the lateral pile displacement. Based on this, it is found that the test single column/shaft with different free lengths shows different failure modes. If the test pile has a longer free length, the failure occurs at the near the ground surface, but the shorter one's failure occurs at the below the ground surface.

• Steel and Composite Structures
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• v.28 no.6
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• pp.767-778
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• 2018

The purpose of this study is to investigate how a fully restrained bolted beam splice affects the connection behavior as a column-tree connection in steel special moment frames under cyclic loading when located within the plastic hinge zone. The impacts of this attachment in protected zone are observed by using nonlinear finite element analyses. This type of splice connection is designed as slip-critical connection and thereby, the possible effects of slippage of the bolts due to a possible loss of pretension in the bolts are also investigated. The 3D models with solid elements that have been developed includes three types of connections which are the connection having fully restrained beam splice located in the plastic hinge location, the connection having fully restrained beam splice located out of the plastic hinge and the connection without beam splice. All connection models satisfied the requirement for the special moment frame connections providing sufficient flexural resistance, determined at column face stated in AISC 341-16. In the connection model having fully restrained beam splice located in the plastic hinge, due to the pretension loss in the bolts, the friction force on the contact surfaces is exceeded, resulting in a relative slip. The reduction in the energy dissipation capacity of the connection is observed to be insignificant. The possibility of the crack occurrence around the bolt holes closest to the column face is found to be higher for the splice connection within the protected zone.

• Steel and Composite Structures
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• v.26 no.3
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• pp.315-328
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• 2018

Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.

• Steel and Composite Structures
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• v.25 no.5
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• pp.603-615
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• 2017

This experimental research presents the seismic performance of steel reinforced high-strength concrete (SRHC) short columns. Eleven SRHC column specimens were tested under simulated earthquake loading conditions, including six short column specimens and five normal column specimens. The parameters studied included the axial load level, stirrup details and shear span ratio. The failure modes, critical region length, energy dissipation capacity and deformation capacity, stiffness and strength degradation and shear displacement of SRHC short columns were analyzed in detail. The effects of the parameters on seismic performance were discussed. The test results showed that SRHC short columns exhibited shear-flexure failure characteristics. The critical region length of SRHC short columns could be taken as the whole column height, regardless of axial load level. In comparison to SRHC normal columns, SRHC short columns had weaker energy dissipation capacity and deformation capacity, and experienced faster stiffness degradation and strength degradation. The decrease in energy dissipation and deformation capacity due to the decreasing shear span ratio was more serious when the axial load level was higher. However, SRHC short columns confined by multiple stirrups might possess good seismic behavior with enough deformation capacity (ultimate drift ratio ${\geq}2.5%$), even though a relative large axial load ratio (= 0.38) and relative small structural steel ratio (= 3.58%) were used, and were suitable to be used in tall buildings in earthquake regions.