재사용 시스템비계와 시스템동바리 수직재의 허용강도 분석

박진석,고상섬,원정훈,Park, Jin-Suk,Ko, Sang Seom,Won, Jeong-Hun 한국안전학회 2021 한국안전학회지 Vol.36 No.4

The allowable strength based on experiments and the design allowable strength calculated using the design criteria were compared, which suggested a ratio between the allowable strengths for the reused vertical members of the system scaffolding and system support. By investigating a total of 421 certification reports for reused vertical members, the experimental allowable strengths were collected. Using design criteria such as the road bridge design and KDS 14 30 10, the design allowable strengths were calculated for various slenderness ratios. For the system scaffolding, the average ratio between the experimental and design allowable strengths was calculated to be 0.880 by assuming a normal distribution for all specimens. However, by analyzing the strength ratio according to the slenderness ratio, the lowest average strength ratio was found to be at least 0.844. Therefore, it is reasonable to assume that the allowable strength of the reused vertical members was 80-84% of the design allowable strength. In addition, assuming the allowable strength to be 85% of the design allowable strength is a possible method for reused vertical members of system supports.

고강도 콘크리트를 적용한 얇은 RC 판부재의 정적 강도 안전성 평가

황훈희,박성용,Hwang, Hoon-Hee,Park, Sung-Yong 한국안전학회 2017 한국안전학회지 Vol.32 No.5

Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

Experimental Study on Load Carrying Capacity Enhancement of System Supports Considering Full Installation of Bracing Members

Hyung Do Lee,원정훈,Nam-Gwon Jang,마호성,Seong-choon Jeong,김승준 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.6

This study investigated the ultimate load capacity of assembled system supports by comparing cases with and without bracing members. Supports used as temporary structures are essential to resist the concrete casting load. Current trends encourage the use of system supports to prevent the collapse of supports, which occur frequently. Studies regarding the ultimate behavior of system supports in Korea are fewer than those in other countries. Existing studies have only focused on the behavior of unit members, such as vertical members. However, studies that focused on unit vertical members under axial loading reported diffi culty in predicting the ultimate behavior of assembled system supports. Furthermore, the ultimate strength of the system support can be decreased signifi cantly in cases without a bracing member, which occur frequently at actual sites. Therefore, the ultimate behavior of the system support considering actual construction site conditions was investigated through experimental tests, focusing on whether bracing members were installed. Experimental results showed that the load-carrying capacity of a three-story system support without a bracing member was 38.4% that of the system support with full bracing members. In addition, the load-carrying capacity of the three-story system support without bracing members decreased by 41.2% compared with that of a two-story system support without bracing members. This indicates that the installation of bracing members is essential for increasing the ultimate load capacity of system supports, and the number of stories of system supports should be considered to determine their ultimate strength.

고강도 재료가 사용된 철근콘크리트 부재의 전단파괴모드

이정윤,김경원 한국공간구조학회 2006 한국공간구조학회지 Vol.6 No.2

고강도 재료(고강도 콘크리트, 고강도 철근)가 사용된 철근콘크리트 부재의 전단파괴모드는 보통강도 재료를 사용한 부재의 전단파괴모드와 상이한 결과를 나타낼 수 있다. 고강도 재료가 사용될 경우에 구조설계기준식에서 요구하는 전단보강철근이 먼저 항복한 후에 콘크리트가 압축파괴하는 것과는 다르게, 철근이 항복하기 이전에 콘크리트가 압축파괴할 수 있다. 이 논문에서는 고강도 재료가 사용된 철근콘크리트 부재의 최대철근비를 균형파괴시의 재료의 응력 및 변형률 상태를 이용하여 계산하였다. 제안식에서 최대철근비는 콘크리트의 압축강도와 전단보강철근의 상호관계에 의하여 변화하였다. 제안식은 97개의 철근콘크리트 부재에 대한 실험결과와 비교되었다. 실험결과 및 계산결과는 철근콘크리트 부재의 파괴모드가 전단보강철근의 양과 콘크리트의 압축강도와 밀접한 관계가 있음을 나타내었다. The shear failure modes of reinforced concrete members using high-strength materials (high-strength concrete and high-strength steel) are different to those of reinforced concrete members using normal-strength materials. The reinforced concrete members using high-strength materials are inclined to fail due to concrete crushing before the shear reinforcing bar reaches its yield strength. This paper presents an evaluation equation to calculate the maximum shear reinforcement ratio based on the material stresses and strains when the reinforced concrete members fail in shear. The maximum shear reinforcement ratio calculated by the proposed equation increases as the compressive strength of concrete increases. Test results of 97 reinforced concrete members reported in the technical literatures are used to check the validity of the proposed equation. The comparison between the test results and the ratio calculated using the proposed equation indicated that the shear failure modes depended on the interaction between the amount of shear reinforcement and the compressive strength of concrete.

Flexural Strength of a Hybrid Member for Culverts Consisting of Mortar-filled Steel Tubes Laterally Connected by Headed Reinforcements

조선규,김성일,박덕혐,이종민 한국강구조학회 2009 International Journal of Steel Structures Vol.9 No.3

In this study, the temporary structural system for a trenchless method was developed. The developed structural system is a type of hybrid member consisting of mortar-filled steel tubes laterally connected by headed reinforcements. This lateral connection gives this system not only longitudinal but also lateral stiffness. Experimental studies were carried out to evaluate the flexural strength of the developed hybrid structural system. Behaviors of each component of this structural system, such as wing plate, connection plate and headed reinforcement were also studied. Experimental results showed that the developed system had superb flexural strength. The wing plate and connection plate had a positive effect on the flexural strength. Based on the experimental results, a simple design equation to evaluate the flexural strength of the developed structural system was suggested and compared with experimental results. In this study, the temporary structural system for a trenchless method was developed. The developed structural system is a type of hybrid member consisting of mortar-filled steel tubes laterally connected by headed reinforcements. This lateral connection gives this system not only longitudinal but also lateral stiffness. Experimental studies were carried out to evaluate the flexural strength of the developed hybrid structural system. Behaviors of each component of this structural system, such as wing plate, connection plate and headed reinforcement were also studied. Experimental results showed that the developed system had superb flexural strength. The wing plate and connection plate had a positive effect on the flexural strength. Based on the experimental results, a simple design equation to evaluate the flexural strength of the developed structural system was suggested and compared with experimental results.

Experimental Study and Numerical Simulation of G550 High Strength Cold-Formed Steel Z-Section Members Under Pure Bending and Moment Gradient

Jin-you Zhao,Cheng Yu 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.2

This paper presents a series of bending tests performed on G550 high strength cold-formed steel Z-section members under pure bending and moment gradient. In tests, failure resulted from distortional buckling or the interaction between local and distortional buckling. The test results indicated that the bending strength for moment gradient is greater than that for pure bending. The increasing magnitude is closely bound up with the member’s buckling modes since moment gradient has a signifi cant eff ect on distortional buckling but has a minor eff ect on local buckling. Moreover, fi nite element analysis was applied to verify the tests and the numerical results agree well with test data according to bending strength and failure modes. Furthermore, the test results were compared with the Direct Strength Method (DSM) formulas stipulated in AISI ( 2016) , and it is found that the DSM provides a good agreement with the bending strength for distortional buckling but provides unconservative predictions for the bending strength for interaction between local and distortional buckling.

철근부식 및 부착성능 변화에 따른 압축 및 휨 부재의 거동

정우영,권민호,안미경,Jung. Woo-Young,Kwon. Min-Ho,Ahn. Mi-Kyoung 한국방재학회 2011 한국방재학회논문집 Vol.11 No.5

본 연구는 염해의 영향을 받은 철근콘크리트 구조물의 성능평가에 관한 연구로서 철근부식에 따른 압축, 휨 부재의 거동을 실험적으로 평가하였다. 철근부식에 따른 유효단면적 변화에 의한 성능평가를 고려한 시험체의 경우 본 연구에서는 전위차 촉진법을 이용하였으며 장기간 발생된 과도한 부식작용으로 인하여 야기되는 철근-콘크리트 경계면 내 부착성능 저하 시험체의 경우 얇은두께의 압축고무 수축튜브를 이용하여 철근길이 대비 비부착 비율을 토대로 경계면 국부 비부착 시험체를 제작, 실험하였다. 두 조건의 시험체들에 대한 실험 결과, 압축부재의 경우 거동메커니즘의 특성을 고려할 때 철근부식에 경계면 부착성능 저하에 따른 큰 성능변화는 발생하지 않았으나 과도한 부식이 진행된 경우 철근유효단면적 변화 및 철근 이형부의 마찰력 저하에 의하여 구조물의 압축성능이 다소 감소하였다. 반면, 휨 부재의 경우 철근부식에 따른 거동결과 차이가 상대적으로 크게 발생하였는데 철근-콘크리트 부착성능 변화에 따른 휨 부재의 거동은 초기철근부식(2%)상태를 제외하고 부식이 진행됨에 따라 구조물 내 극심한 균열 및 초기 취성파괴를 나타내었다. This research presents an experimental study on the load capacity of reinforced concrete(RC) compression and flexural members induced by chloride corrosion. The parameters considered in this study are both the increased corrosion ratios of reinforcing bar and the variation of partial corroded length. Some test specimens are corroded by using Accelerated Potentiometeric Corrosion Method and the others which are fabricated by using compressive rubber tubes at the contact surface between concrete and steel bar are tested in order to investigate the load capacity of the structure in the events of the degradation of bonding strength at the interface between concrete and steel bar. It is finally shown that the overall load capacity of compression member with corroded reinforcing bars is decreased because it is mainly influenced by not the bonding strength at the concrete-steel contact surface but the reduction of the effective section area at the corroded reinforcing bar; while for the flexural members, compared to the compression member, the degradation of load capacity is remarkable. It is evident that the flexural member is influenced by both two parameters like the effective area and bonding strength at the contact surface except initial corrosion ratio 2%. The reduction of the load capacity of this member leads to occur severe crack and prematured failure after yielding the member.

고강도콘크리트와 고강도철근을 사용한 RC 보의 휨성능 평가

홍건호(Hong Geon-Ho) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.6

Recently, many research were performed to develop the high strength concrete and reinforcing bar because super tall building and large space structures require the high strength structural materials. The purpose of this paper is to evaluate the flexural performance of reinforced beams with high strength concrete and high strength reinforcing bars. Total 9 simple beam specimens divided by 3 groups tested for evaluating the flexural performance. Main test variables were concrete compressive strength from 27 to 68㎫ and yield strength of longitudinal reinforcement from 400 to 700㎫. Test data analyzed in the viewpoint of cracking load, ultimate flexural strength, load-deflection relationship, crack progress, failure aspects and ductility. Test results indicate that flexural capacity of the specimen is similar from a standpoint of unit strength-area of reinforcement regardless concrete compressive strength. Flexural stiffness of the specimens with high strength reinforcing bars were reduced, and this phenomenon is well agreed with the reduction of effective moment of inertia Ie. But stiffness reduction ratio was decreased when concrete compressive strength increase. Number of crack was decreased and maximum crack width was increased when concrete compressive strength increase.

장애인부모단체 회원의 가족건강성 영향 요인: 동료지지와 단체만족도를 중심으로

이강훈 한국장애인복지학회 2016 한국장애인복지학 Vol.- No.32

This study aimed to specifically verify influence factors on family strengths with focus on the environmental factors of disabled children parents group and the family environmental factors of members. For this, a hierarchical multiple regression analysis and a structural equation analysis were conducted on 356 questionnaires responding to questions of satisfaction with group and support of colleague by 62 disabled Children parents group members in 16 si·do throughout the country. According to research result, first, major factors influencing directly on family strengths were found in the order of marital satisfaction, parenting stress, and satisfaction with group. Second, main paths influencing on family strengths were analyzed as support of colleague → disabled children parents group → marital satisfaction → family strengths. Third, support of colleague considered as group environmental factor did not have direct influence but it had indirect influence through satisfaction with group, parenting stress, and marital satisfaction. It was analyzed that satisfaction with group had indirect influence on family strengths through parenting stress and marital satisfaction in addition to direct influence. This study suggested a specific intervention way to strengthen support system of disabled children parents group and members and to improve family strengths relying on analysis result. 본 연구는 장애인부모단체의 환경요인과 회원의 가족환경요인을 중심으로 가족건강성에 미치는 영향 요인을 구체적으로 검증하고자 하였다. 이를 위해 전국 16개 시·도 62곳의 장애인부모단체 회원들 중 단체만족도와 동료지지에 응답한 356부의 설문에 대한 위계적 다중회귀분석과 구조방정식 분석을 진행하였다. 연구결과 첫째, 가족건강성에 직접적인 영향을 미치는 주요변인은 결혼만족도, 양육스트레스, 단체만족도 순으로 나타났다. 둘째, 가족건강성에 영향을 미치는 주요 경로는 ‘동료의지지→장애인부모단체→결혼만족도→가족건강성’으로 분석되었다. 셋째, 단체 환경요인으로 고려한 동료지지는 직접적인 영향력은 없었으나 단체만족도, 양육스트레스, 결혼만족도를 통해 가족건강성에 간접적인 영향을 미쳤다. 단체만족도는 직접적인 영향력과 함께 양육스트레스와 결혼만족도를 통해 가족건강성에 간접적 영향력을 미치는 것으로 분석되었다. 주요 분석 결과를 중심으로 장애인부모단체와 회원의 지지체계를 강화하고 가족건강성의 향상을 위한 개입 방안을 구체적으로 제시하였다.

고강도철근이 배근된 철근콘크리트 보의 휨성능 평가

홍건호(Hong Geon-Ho) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.1

Korean building code requirements provide that the yield strength of longitudinal reinforcement shall not exceed 550 ㎫ in flexural members. The purpose of this paper is to evaluate the possibility of yield strength increase up to 600 ㎫ or 700 ㎫ in flexural reinforcement. Total 8 simple beam specimens divided by 3 groups tested for evaluating the flexural performance. Main test variables were yield strength of longitudinal reinforcement, reinforcement ratio and cover thickness. Test data analyzed in the viewpoint of cracking load, ultimate flexural strength, load-deflection relationship, crack progress, failure aspects and ductility. Test results indicate that flexural capacity of the specimen is similar from a standpoint of unit strength-area of reinforcement, but ductility of the specimens with high strength reinforcing bars was reduced in high reinforcement ratio. Flexural stiffness of the specimens with high strength reinforcing bars was also reduced, and this phenomenon is well agreed with the reduction of effective moment of inertia Ie. This paper concluded that flexural strength can be calculated using the present code provision without any change, but deflection checkup will be needed when the flexural member design with high strength reinforcing bars.