Shear Behavior of Single Cast-in Anchors in Plastic Hinge Zones

Derek Petersen,Zhibin Lin,Jian Zhao 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.3

This paper presents two shear tests of 3/4-in. diameter cast-in anchors embedded in the plastic hinge zone of reinforced concrete columns. Design codes, such as ACI 318-14, require special reinforcement for concrete anchors in concrete that could be substantially damaged during an earthquake. The test anchors in this study were equipped with the anchor reinforcement recommended and verified in the literature. The column specimens were subjected to quasi-static cyclic loading before the test anchors were loaded in shear. Steel fracture was achieved in both test anchors despite cracks and concrete spalling occurred to the concrete within the plastic hinge zones. Meanwhile, the measured anchor capacities were smaller than the code-specified capacity, especially for the anchors subjected to cyclic shear. Concrete cover spalling was found critical to the observed capacity reduction, which caused combined bending and shear action in the anchor bolts. Measures should be developed to mitigate such adverse impact. In addition, further studies are needed for post-installed anchors before practical applications.

Shear capacity of cast-in headed anchors in steel fiber-reinforced concrete

Lee, Jong-Han,Cho, Baiksoon,Kim, Jae-Bong,Lee, Kun-Joon,Jung, Chi-Young Elsevier 2018 ENGINEERING STRUCTURES Vol.171 No.-

<P><B>Abstract</B></P> <P>This paper investigates the concrete breakout shear capacity of a single cast-in headed anchor embedded in steel fiber-reinforced concrete (SFRC). Experiments were carried out for anchors with a diameter of 30 mm, embedment depth of 240 mm, and edge distance of 150 mm. Fiber volume fractions of 0.33, 0.67, and 1.00% were examined. In addition to shear tests, four-point bending tests were carried out to evaluate the relationship between the material properties of SFRC and the shear capacity of anchors. The experimental results show that the current design formulas are valid for anchors in conventional plain concrete but not appropriate for the shear capacity of anchors in SFRC. Using the equivalent flexural strength ratio, a revised design equation is proposed to incorporate the effect of the steel fiber content on the concrete breakout shear capacity and provide reasonably similar safety for anchors in both un-reinforced and SFRC.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Shear Behaivor and breakout capacity of CI anchors embedded in SFRC were investigated. </LI> <LI> Relationship between the shear capacity of anchors and the material properties of SFRC were evaluated. </LI> <LI> Ultimate shear capacity exhibited strong correlations with fiber volume fraction and equivalent flexural strength ratio. </LI> <LI> A revised equation was proposed to account for the effect of steel fibers on the breakout shear resistance of anchors. </LI> </UL> </P>

Experimental Evaluation of Tension and Shear Capacities of New Headed Cast-in Specialty Inserts in Cracked Concrete

정상덕,오창수,이창환 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.5

Headed cast-in specialty inserts are often developed and employed for their improved constructability and time-saving benefits over traditional cast-in and post-installed anchors. Their acceptance criteria (AC 446) were established by The International Code Council Evaluation Service. However, previous research on the behavioral characteristics of headed specialty inserts is rare. This study investigates the performance of a newly developed insert anchor for use as an earthquake-resistant anchor for fire protection systems and suspended lightweight piping. Firstly, three cyclic tension tests of the specialty insert with a threaded rod were conducted in accordance with AC 446. These tests resulted in all experimental subjects achieving the target strength without defects. Subsequently, monotonic tension and shear tests of the insert anchor in cracked concrete were performed five times each to assess the tensile and shear capacities of the new insert anchor. The results were compared with the nominal strength determined by the anchor design equation provided by the ACI 318 for cast-in headed anchors, finding that the latter adequately approximates the concrete breakout strength of the new insert anchor in tension but underestimates the concrete pryout strength in shear. Based on the measured breakout failure surface angles, a projected area of the failure cone of the corresponding anchor with a relatively large head size is proposed.

프리캐스트 콘크리트 패널 분절 아치 시공을 위한 선설치 앵커의 인발 강도 평가

안진희,임홍재,방진수,전석현 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 논문집 Vol.24 No.2

Precast concrete segment arch system has an economic and construct ability that combined with advantage of precast concrete and arch behavior. A precast concrete segment arch system with outrigger is consisted of segmented precast panels, a steel outrigger rib, and V-strip to connect precast panels with a steel outrigger rib and cast-in-place anchors in precast panels to connect V-strip should have sufficient pull-out capacity to form its arch shape by site lifting for assembled precast panels and outriggers. However, it is difficult to secure its embedment depth due to the relatively shallow thickness of precast panel. It can be also occurred that flexure deformation of precast panels caused by its pull-out behaviors. In this study, pull-out capacity of cast-in-place anchor was examined for construction of precast concrete segment arch system with outriggers. Therefore, a total of 24 precast panel specimens were fabricated to examine pull-out capacities of cast-in-place anchor in precast panels, and installation depth of anchors, diameter of anchors and wire mesh effects for the precast panel were examined. From this pull-out tests, its pull-out capacities and failure modes were evaluated and the type of the cast-in-place anchor applicable to the precast concrete segment panel arch system with outriggers was determined from comparison of the design specification values. 프리캐스트 콘크리트의 장점과 및 석조 아치의 거동을 접목한 콘크리트 패널 분절 아치 시스템은 가설재가 불필요한 시공성을 확보할 수 있는 경제적 시공법이다. 프리캐스트 새그먼트 패널의 연속 배치로 구성된 아치는 인양 및 시공을 위한 V형-스트립 연결부의 선설치 앵커 설치가 필수적이다. 그러나 좁은 폭과 얇은 두께의 콘크리트 패널은 선설치 앵커의 충분한 묻힘 깊이 확보를 보장할 수 없고 앵커 인발 거동 시 패널의 휨변형을 동반하는 등 앵커 저항성능 확보를 위한 콘크리트 패널의 기하학적 영향이 고려되어야 한다. 따라서 본 연구에서는 프리캐스트 패널과 강재 아웃리거로 구성된 아치구조의 제작시 설치되는 선설치 앵커의 인발 강도 평가를 위한 실험 연구를 수행하였다. 이를 위해 실제 아치 시스템과 동일한 크기의 프리캐스트 콘크리트 패널을 제작하였으며, 선설 앵커의 직경, 앵커 묻힘 깊이, 와이어 매쉬 사용 등의 영향에 따라 총 24개 실험체의 선설치 앵커 인발 강도를 측정하였다. 또한 측정 변수에 따른 설계기준강도 확보 및 파괴 모드 평가를 통해 프리캐스트 콘크리트 패널 분절 아치 구조에 적용 가능한 선설치 앵커의 형태를 결정하였다.

Dynamic shear strength of unreinforced and Hairpin-reinforced cast-in-place anchors using shaking table tests

김동현,박용명,강충현,이종한 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.58 No.1

Since the publication of ACI 318-02, the concrete capacity design (CCD) method has been used to determine the resistance of unreinforced concrete anchors. The regulation of steel-reinforced anchors was proposed in ACI 318-08. Until ACI 318-08, the shear resistance of concrete breakout for an unreinforced anchor during an earthquake was reduced to 75% of the static shear strength, but this reduction has been eliminated since ACI 318-11. In addition, the resistance of a hairpin-reinforced anchor was calculated using only the strength of the steel, and a regulation on the dynamic strength was not given for reinforced anchors. In this study, shaking table tests were performed to evaluate the dynamic shear strength of unreinforced and hairpin-reinforced cast-in-place (CIP) anchors during earthquakes. The anchors used in this study were 30 mm in diameter, with edge distances of 150 mm and embedment depths of 240 mm. The diameter of the hairpin steel was 10 mm. Shaking table tests were carried out on two specimens using the artificial earthquake, based on the United States Nuclear Regulatory Commission (US NRC)’s Regulatory Guide 1.60, and the Northridge earthquake. The experimental results were compared to the current ACI 318 and ETAG 001 design codes.

새로운 형태의 선설치 인서트 앵커에 대한 단조 인장 및 전단강도 평가

전주성,김지훈,오창수,이창환,Jeon, Ju-Seong,Kim, Ji-Hoon,Oh, Chang-Soo,Lee, Chang-Hwan 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2

The damage to non-structural elements in buildings has been increasing due to earthquakes. In Korea, post-installed anchors produced overseas have been mainly used for seismic anchorage of non-structural components to structures. Recently, a new cast-in-place concrete insert anchor installed in concrete without drilling has been developed in Korea. In this paper, an experimental study was conducted to evaluate the tensile and shear strengths of the newly developed anchor under monotonic load. The failure modes of the tension specimens were divided into concrete breakout failure and steel failure, and all shear specimens showed steel failure. In both tension and shear, the maximum loads of specimens were greater than the nominal strengths predicted by the concrete design code (KDS 14 20 54). As a result, it is expected that the current code can also be used to calculate the strength of the developed cast-in anchor.

비구조재 정착부 앵커형상에 따른 선설치 앵커채널의 거동 특성

정영수,우태련,김재봉 한국복합신소재구조학회 2020 복합신소재구조학회논문집 Vol.11 No.3

Anchor channels are applied to the connected components of reinforced concrete structures as a result of their ease of and reliability in being affixed to the exterior of structures. Moreover, cast-in anchor channels do not damage the concrete reinforcement during drilling and have the advantage of minimizing damage due to field welding. In this study, the tensile and shear behaviors of anchor channels, coupled with the stud anchor and plate-welded anchor types, were evaluated experimentally. The test results show that the stud anchor type has a relatively large ultimate tensile strength compared to that of the plate-welded anchor type. As a result of comparing the geometric shape of the anchor embedded in the concrete, the presence or absence of rebar located at the edge, and edge distance, it was found that the shear strength of the plate-welded anchor type is approximately 55% lower than that of the stud anchor type. 앵커채널은 건축 외장재 등을 쉽고 안정적으로 고정하는데 적합하여 철근콘크리트 구조물의 연결 구성요소에 적용되고 있다. 선설치 앵커채널은 천공 중 콘크리트 보강재를 손상시키지 않으며, 현장용접 등에 의한 손상을 최소화 하는 장점이 있다. 본 연구에서는 원형앵커와 I형 앵커를 적용한 앵커채널의 인장 및 전단 거동을 실험적으로 평가하였다. 연단거리 및 피복철근 및 앵커형상에 따른 앵커채널의 인장 및 전단강도 평가를 위하여 인장 및 전단실험을 실시하였다. 시험 결과, 원형앵커의 인장강도는 I형 앵커보다 증가하는 경향이 나타났다. 그리고 콘크리트에 매립된 앵커의 기하학적 형상, 피복철근 유무 및 연단거리에 따라 비교한 결과, I형 앵커의 전단강도가 원형앵커보다 약 55% 낮은 것을 알 수 있었다.

Behavior and Strengths of Single Cast-in Anchors in Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) Subjected to a Monotonic Tension or Shear

최석환,조창빈,천성철 대한토목학회 2015 KSCE Journal of Civil Engineering Vol.19 No.4

Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) exhibits improved compressive and tensile strengths and strain capacity far superior to those of conventional concrete. The anchors used in UHPFRC are expected to have much higher strengths in concrete-related failure modes and to show a very reliable performance. A total of thirty-three tests, seventeen tension tests and sixteen shear tests, were conducted on anchors in UHPFRC of a 199 MPa compressive strength. The load capacities and displacement capacities of these anchors in UHPFRC were significantly improved compared with the anchors in normal concrete, in both tension and shear. The average ratios of the measured strengths to the predictions by the Concrete Capacity Design (CCD) method were 1.40 for the breakout strength in tension, 1.07 for the breakout strength in shear, and 2.62 for the pryout strength. The enhanced capacities can be attributed to the improved strain capacity and tensile strength of UHPFRC: the improved tensile strength enlarged the projected concrete failure area as well as enhanced the resisting strength and the improved strain capacity secured a reliable performance with low variance, i.e., a higher safety factor than a factor for normal concrete. Three design equations, i.e. breakout strength in tension, breakout strength in shear, and pryout strength, for anchors in UHPFRC were proposed by modifying design equations of ACI 318-11 through regression analyses of the tests, and using the 5% fractile coefficient, they have the same reliability as the design equations of ACI 318-11.

Shear Tests on Subassemblies Representing the Multi-anchored Connection between PC Wall Panels and RC Frames

손국원,하수경,송근택,유승룡 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.12

When existing Reinforced Concrete (RC) framed structures are strengthened with Precast Concrete (PC) wall panels, a special connection is required that can accommodate the time-dependent deformation of the RC frame when using PC members made of the same size and resist a large shear force. In this study, we propose a connection that can solve both of these issues through overlapping anchors. The purpose of this study is to investigate and analyze the shear resistance of the overlapped anchor connections between the PC panel and the RC elements in modeling tests. A total of ten full-scale specimens of anchored connection models were constructed and push-out tested. Two anchor groups were installed in three concrete segments and overlapped in the connection of the specimens. The tested average shear strength of the overlapped anchored connections was 109% of the calculated values according to the American anchor design code. The results of this study show that the new anchored connection model can be analyzed using the American anchor design code. Therefore, we can predict the effect of the proposed connection, and it is expected that the design safety and construction practicability of the infill method will be improved using these connections.

피로하중에 의한 캐스트 인 앵커 찬넬의 잔류강도 평가

원재식 ( Won Jae Sik ),허무원 ( Hur Moo Won ),채경훈 ( Chae Kyoung Hun ),안영승 ( An Yeong Seung ),이상현 ( Lee Sang Hyun ),박태원 ( Park Tae Won ) 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.24 No.1

최근 고층건물에서 사용되고 있는 캐스트 인 앵커 찬넬은 선행 연구를 통해 인장 및 인발 성능을 충분히 확보하고 있음을 알 수 있었지만, 피로하중에 의해 손상된 캐스트 인 앵커 찬넬의 기존 성능 및 내력이 유지되고 있는지에 대한 검토가 필요하다. 본 연구에서는 반복가력실험으로 손상된 캐스트 인 앵커 찬넬의 인발실험을 통해 잔류강도를 측정하여, 충분한 내력을 확보하고 있는지 검토하였다.