• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권6호
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• pp.440-447
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• 2020

Masonry structures are used as bearing walls in small buildings, but they are generally considered non-bearing walls. They are used as partition walls that divide the interior spaces of the frame structures of buildings. In addition, wetting techniques that use mortar as an adhesive between blocks or bricks in construction are vulnerable to climatic conditions, especially cracks in mortar, which can cause conduction collapse of the walls in seismic loading. The purpose of this research was to propose a dry concrete block construction method that complements the weak axial shear stiffness and improves the weakness of the wet construction method as well as to investigate its structural behavior. In this study, the material properties of concrete blocks were examined, and the seismic performance of the proposed dry assembly structure was verified by structural behavior tests on horizontal cyclic loads. First, in these study results, concrete blocks can be applied to the dry block construction method instead of wet construction methods because they secure more than C-type blocks in KS regulations. Second, the structural performance of the wall against a horizontal cyclic load indicates that the resisting force of the assembly block wall is increased by increasing the horizontal length of the wall, forming several diagonal cracks. Finally, the proposed dry block wall structure requires a seismic performance assessment considering that the ratio of the shape of the wall by height and length is considered a major influence variable on the structural behavior under a horizontal load.

• Earthquakes and Structures
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• 제14권1호
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• pp.73-84
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• 2018

Low cyclic loading tests are conducted on the steel reinforced recycled concrete (SRRC) column-steel (S) beam composite frame joints. This research aims to evaluate the earthquake damage performance of composite frame joints by performing cyclic loading tests on eight specimens. The experimental failure process and failure modes, load-displacement hysteresis curves, characteristic loads and displacements, and ductility of the composite frame joints are presented and analyzed, which shows that the composite frame joints demonstrate good seismic performance. On the basis of this finding, seismic damage performance is examined by using the maximum displacement, energy absorbed in the hysteresis loops and Park-Ang model. However, the result of this analysis is inconsistent with the test failure process. Therefore, this paper proposes a modified Park-Ang seismic damage model that is based on maximum deformation and cumulative energy dissipation, and corrected by combination coefficient ${\alpha}$. Meanwhile, the effects of recycled coarse aggregate (RCA) replacement percentage and axial compression ratio on the seismic damage performance are analyzed comprehensively. Moreover, lateral displacement angle is used as the quantification index of the seismic performance level of joints. Considering the experimental study, the seismic performance level of composite frame joints is divided into five classes of normal use, temporary use, repair after use, life safety and collapse prevention. On this basis, the corresponding relationships among seismic damage degrees, seismic performance level and quantitative index are also established in this paper. The conclusions can provide a reference for the seismic performance design of composite frame joints.

• Journal of Korean Society of Steel Construction
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• 제29권3호
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• pp.205-215
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• 2017

This study presents an example of conceptual design for hollow circular section multi-column tower system subjected to 10MW level wind load by introducing a method based on member utilization that examine both structural stability and economical efficiency. The basic assumptions for the proto type of a multi-column tower that can replace a single-cylinder tower were suggested and structural models were constructed following the assumptions and analyzed for identifying member forces. Based on the calculated member strengths and acting loads, the member utilization of the proposed multi-column tower structures were calculated for axial force, shear, bending and torsion and evaluaed for suitability as a wind tower. Design parameters such as steel tube dimensions, slenderness ratio, and number of floors for braces was proposed in the acceptable range of member utilization for conceptual design of multi-column wind towers.

• Journal of the Korea Concrete Institute
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• 제15권6호
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• pp.877-887
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• 2003

For a performance-based design of structural walls, it is necessary to develop a rational design method for determining the length and detail of boundary confinement so as to satisfy the given ductility demand. In the present study, the curvature capacity of a structural wall with boundary confinement was estimated considering the effects of various design parameters. The curvature demand of the plastic hinge corresponding to the given design displacement was also determined. By equalizing the curvature capacity to the demand, a design method for determining the length of boundary confinement, was developed. According to the design method, the length of boundary confinement increases as axial compressive load and design displacement increase, and as concrete strength, wall thickness, amount of lateral reinforcement and aspect ratio decrease. A study was performed on details for effective lateral confinement of walls with rectangular cross-section. Based on the findings, design guidelines on spacings of ties and cross-ties were proposed.

• Journal of the Earthquake Engineering Society of Korea
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• 제7권6호
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• pp.25-34
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• 2003

Recently, performance-based analysis/design methods such as the capacity spectrum method and the direct displacement-based design method were developed. In these methods, estimation of energy dissipation capacity of RC structures depends on empirical equations which are not sufficiently accurate, On the other hand, in a recent study, a simplified method for evaluating energy dissipation capacity was developed. In the present study, based on the evaluation method, a new seismic design method for flexure-dominated RC walls was developed. In determination of earthquake load, the proposed design method can address variations of energy dissipation capacity with design parameters such as dimensions and shapes of cross-sections, axial force, and reinforcement ratio and arrangement, The proposed design method was compared with the current performance-based design methods. The applicability of the proposed method was discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제40권8호
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• pp.751-757
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• 2016

The aim of this study is to estimate the reliability of fatigue limit of the material used for crank throw components according to the staircase method. The material used for crank throw components is forged S34MnV grade steel, which is heat treated by normalizing and tempering. In this work, to predict the reliability of the design fatigue strength, axially loaded constant amplitude fatigue testing was conducted. The test specimens were loaded with an axial push/pull load with a mean stress of 0 MPa, which corresponds to a stress ratio of R=-1. The fatigue test results were evaluated by Dixon-Mood formulas. The values of mean fatigue strength and standard deviation predicted by the staircase method were 296.3 MPa and 10.6 MPa, respectively. Finally, the reliability of the fatigue limit in some selected probability of failure is predicted. The proposed method can be applied for the determination of fatigue strength for design optimization of the forged steel.

• Geotechnical Engineering
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• 제5권4호
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• pp.37-46
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• 1989

The object of this paper is to study the general characteristics of overconsolidated silty clays subjected to repeated loading. The samples are first remolded. overconsolidated and a series of strain - controlled triaxial repeated tests are carried out. Generally the relationship of deviator stress - axial strain of overconsolidated clay is similar in pattern to the normally consolidated clay under single load. But the behavior of the pore water pressure build up in the sample subjected to repeated loading is dependent upon the consolidation history and the level of repeated stress. Therefore through the series of the tests, the characteristics of stress -strain relationship of soils which are differentlly overconsolidated are investigated, analysed and then compared with each soils. And also, from the relationship of test results, the strength and strain characteristics of soils are obierved. The equilibrium lines which presents the critical repeated stress and equilibrium state in the sample under repeated loading, are often straight, but may be curved. And the tendency of the equilibrium lines is observed as to the variation of overconsolidation ratio.

• Journal of the Korea Concrete Institute
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• 제14권4호
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• pp.566-577
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• 2002

As advanced earthquake analysis/design methods such as the nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and capacity of energy dissipation. However, currently, estimation of energy dissipation depends on empirical equations that are not sufficiently accurate, or experiment and sophisticated numerical analysis which are difficult to use in practice.0 the present study, nonlinear finite element analysis was performed to investigate the behavioral characteristics of flexure-dominant RC members under cyclic load. The effects of axial force, arrangement of reinforcing bars, and reinforcement ratio on the cyclic behavior were studied. Based on the investigation, a simplified method to estimate the capacity of energy dissipation was proposed, and it was verified by the comparison with the finite element analyses and experiments. The proposed method can estimate the energy dissipation of RC members more precisely than currently used empirical equations, and it is easily applicable in practice.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제26권2호
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• pp.336-344
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• 2002

In this study, the flow and combustion characteristics of flat flame burner with twirler were investigated. There are several factors that define the characteristics of burner. Among them, the experiments was focused on swirl effect by four types of twirler in terms of flow structure, distribution of temperature and emission characteristics. In PIV(Particle Image Velocimetry) experiment, the less of swirl number, axial flow is dominant at the center. As swirl number increases, the flow develops along the burner tile and backward flow becomes stronger at center. From the combustion characteristics, as long as combustion load increases, blow-off limit was improved. But at the higher swirl number, the limit is decreased. At swirl number 0, the temperature is shown typical distribution of long flame burner. but swirl number increases, the temperature distribution is uniform in front of round tile. Therefore, the temperature distribution is coincided with flow structure. As excess air ratio increases, NO concentrations are high. But high swirl number gives rise to become low NO concentrations. The flame characteristics are comprised in wrinkled laminar-flame regime according to turbulence Reynolds number(Rel) and Damkohler number(Da).

• Steel and Composite Structures
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• 제39권4호
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• pp.383-399
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• 2021

In the study, three 1:3-scale unequal span steel-concrete composite substructures with top-seat angle and double web angle connection were designed and identified as specimens GTSDWA-0.6, GTSDWA-1.0, and GTSDWA-1.4. Pseudo-static tests and refined numerical model analysis were conducted to examine the anti-progressive collapse performance of a semi-rigid steel-concrete composite substructure. The results indicated that the failure modes of the three specimens revealed that the fracture occurred in the root of the long leg of the top/seat angle in tension at the connection. With increases in the span ratio of the left and right composite beams, the bearing capacities of the composite substructures decreased, and the corresponding displacement increased. With respect to GTSDWA-0.6 and GTSDWA-1.4, the resistance due to the short composite beam corresponded to 62% and 60%, respectively, and the total resistance provided by the short composite beam exceeded that of the long composite beam. With respect to GTSDWA-1.0, the resistance due to the left and right composite beams was similar. All three specimens underwent the flexure mechanism and flexure-axial mixed mechanism stages. They resisted the external load mainly via the flexure mechanism. Moreover, the addition of stiffeners on both sides of the top and seat angles is advantageous in terms of improving the collapse resistance and ductility of unequal span composite substructures.