부착식 앵커의 인발 특성에 관한 실험적 연구

유성원(Yoo Sung Won),정상화(Jung Sang-Hwa),곽기석(Kwak Ki-Suk),이주형(Lee Ju-Hyung) 대한토목학회 2006 대한토목학회논문집 A Vol.26 No.3A

최근 많은 교량들이 점증하는 교통량에 의해 상부슬래브 폭이 부족해지거나 침식으로 인해 하부구조가 구조적으로 취약해지는 경향이 있다. 이 경우 상부슬래브나 교각을 확장하여 보강하는 것이 경제적이기 때문에 실험 자료와 현장의 시공경험 등을 통해 적절한 교량의 확장방안을 확립할 필요가 있다. 그렇지만, 부착식 앵커를 사용하여 교량의 하부구조를 보수ㆍ보강하는 경우 신ㆍ구 콘크리트의 일체성 확보와 관련된 기존 실험자료는 매우 부족한 실정이며, 이에 따라 부착식 앵커를 사용하여 구조적인 일체성을 확보하기 위한 실험적인 연구가 매우 시급하다고 할 수 있다. 이와 관련하여 본 논문에서는 부착식 앵커를 시용할 경우의 인발 및 전단 특성을 실험을 통해 밝히고자 하였다. 이를 위해 부착길이, 앵커직경 및 앵커경사를 포함한 다양한 실험변수를 가진 시편을 제작하여 인발 및 전단실험을 수행하였다. 실험결과 부착길이가 길어지고 앵커직경이 커질수록 부착력은 증가하고 부착강도는 감소하였다. 또한, 앵커경사가 커질수록 부착력 및 부착강도가 증가하지만 경사가 5° 이상인 경우 경시에 의한 효율이 감소하는 것을 알 수 있었다. 전단실험을 통해서는 앵커직경이 D19 이상을 사용하는 것이 적절할 것으로 판단되었다. 결론적으로 향후 모델실험을 포함한 관련 자료의 축적이 이루어지는 경우 본 연구에서 수행한 실험 자료와 함께 부착식 앵커를 사용하여 보강된 신ㆍ구 콘크리트의 일체성을 확보하는데 많은 기여를 할 수 있을 것으로 기대된다. Recently, many bridges become not only functionally obsolete of bridge deck due to inadequate width but also structurally deficient of substructure due to erosion. In these cases, widening is almost always more economical than complete replacement, and therefore there is a need to make available the results of research and field experience pertaining to the widening of bridge substructure. But, an experimental study for the guarantee of unification between existing and new substructure with adhesive anchor is so insufficient that the development of adhesive anchor system for the unification should be settled promptly. The purpose of the present study is to explore pull out and shear characteristics of adhesive anchor system. For this purpose, several series of concrete specimens have been tested. Major test variables were the bonded length, anchor diameter and anchor slope. The pullout strength, bond stress and shear strength of adhesive faces were measured for the specimens. The present study indicates that the pull out strength increased with more bonded length and more anchor diameter, and that the bond stress decreased with more bonded length and more anchor diameter. The pull out strength and the bond stress increases with more anchor slope and it is considered that the slope of 5° was more efficient. From the shear tests, it is supposed that anchor diameters more than D19 was proper to the adhesive anchor. Finally, it is expected that both experimental data in these tests and further study including mock-up tests will contribute to the establishment of the unification between existing and new substructure with adhesive anchor.

Study on Dynamic Bond-Slip Constitutive Relation of Corroded Mortar Anchor

Haitao Wang,Yue Xin,Pengbo Zhang,Minghua Cui 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.12

In order to study the bonding performance of corroded mortar anchor under dynamic load and reveal the mechanism of dynamic bond-slip, dynamic pull-out tests for mortar anchors with different corrosion degrees were carried out. On the basis of the average bond stress and relative slip, the basic bond-slip constitutive relation of corroded mortar anchor was established according to the measured data. The bond stress under different loading frequency were fitted, and the dynamic influence coefficient affecting the bond performance of mortar anchor was obtained. Based on the bond stress-slip relationship of each point in the anchorage section under different corrosion degrees, the position function in anchorage section was deduced. According to the above basic bond-slip relation, dynamic influence coefficient and anchorage position function, the dynamic bond-slip constitutive relation of corroded mortar anchor regarding to anchorage position was established, which could provide reference for the study on the durability of mortar anchor and its dynamic anchorage performance.

Improvement of Pullout Loads by Variation of Two Load Points in Anchorage System

이강일,이재욱,김재홍 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8

Multiple compression type anchors were developed to relive the problem of uneven exertions of bond stress across the bond lengths of existing anchors. Unlike existing anchors, these anchors can have different lengths of strand to adjust the spacing of load points between anchors and also can have different orders of tensions of anchors to ensure even exertions of bond stress across the bond length. The spacing of load points and the order of tensions are considerations that can affect the pullout load of anchors because interference effects between anchors vary with them. However, existing studies have investigated the pull-out characteristics of anchors without considering the aforementioned factors. In this study model tests were conducted to investigate the pull-out characteristics of multiple compression type anchors that vary with the spacing of load points between anchors and the order of tensions. Through the results of the study on the pull-out characteristics of two load points of anchorage system, it was identified that interference effects between anchors varied with the spacing of load points between anchors and the order of tensions to affect the pullout load.

부착형 암반앵커기초의 인발지지력 평가

김대홍,이용희,Kim, Dae-Hong,Lee, Yong-Hee 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.10

This paper presents the results of full-scale loading tests performed on 54 passive anchors and 4 group anchored footings grouted to various lengths at several sites in Korea. The test results, the failure mechanisms as well as uplift capacities of rock anchors depend mostly on rock type and quality, embedded fixed length, properties of the discontinuities, and the strength of rebar. Anchors in poor quality rocks generally fail along the grout/rock interfaces when their depths are very shallow (a fixed length of less than 1 m). However, even in such poor rocks, we can induce a more favorable mode of rock pull-up failure by increasing the fixed length of the anchors. On the other hand, anchors in good quality rocks show rock pull-up failures with high uplift resistance even when they are embedded at a shallow depth. Laboratory test results revealed that a form of progressive failure usually occurs starting near the upper surface of the grout, and then progresses downward. The ultimate tendon-grout bond strength was measured from $18{\sim}25%$ of unconfined compressive strength of grout. One of the important findings from these tests is that the measured strains along the corrosion protection sheath were so small that practically the reduction of bond strength by the presence of sheath would be negligible. Based on test results, the main parameters governing the uplift capacity of the rock anchor system were determined. By evaluation of the ultimate uplift capacity of anchor foundations in a wide range of in situ rock masses, rock classification suitable for a transmission tower foundation was developed. Finally, a very simple and economical design procedure is proposed for rock anchor foundations subjected to uplift tensile loads.

앵커 부착-미끄러짐 모형을 이용한 콘크리트-강재 구조물의 비선형 반복하중 해석

임주은(Lim Ju Eun),이지호(Lee Jee Ho) 대한토목학회 2009 대한토목학회논문집 A Vol.29 No.5A

본 논문에서는 앵커로 연결된 콘크리트-강재 구조물이 극한 반복주기하중을 받는 경우를 수치 시뮬레이션하기 위하여 필요한 콘크리트-앵커 부착모형에 대하여 논하였다. 제안되는 앵커의 부착-미끄러짐 수치모형은 비선형 일축 연결요소의 조합으로 이루어지며 인발실험 결과를 이용하여 부착-미끄러짐 모형의 인자를 결정할 수 있다. 제안된 앵커 부착-미끄러짐 모형을 Abaqus 요소의 조합으로 구성하고, 이를 사용한 해석 결과와 앵커의 완전부착모형을 사용한 해석 결과를 실험 결과와 비교하였다. 이로부터 극한 반복하중을 받는 콘크리트-강재 구조물 수치해석에는 합리적인 앵커 부착-미끄러짐 모형이 반드시 사용되어야 한다는 것을 알 수 있었으며 본 연구에서 제안한 합성 연결모형을 이용하면 사실적으로 앵커의 부착-미끄러짐 현상을 모사할 수 있다는 것을 확인하였다. In this paper, a numerical anchor bond-slip model is proposed to improve the numerical simulation of concrete-steel structures connected with steel anchor bolts and subjected to extreme cyclic loading. The suggested bond-slip model is composed of a group of nonlinear uniaxial connector elements and its parameters can be determined by calibrating the model with pull-out test data. Numerical analysis results from simulating a concrete foundation-steel column structure using the proposed bond-slip anchor model, which is implemented based on Abaqus elements, and the perfect-bond anchor model are compared with the experimental results. It is concluded that a reasonable anchor bond-slip model is required to realistically simulate concrete-steel structures subjected to extreme cyclic loading, and the proposed anchor bond-slip model shows acceptable performance in the present numerical analysis.

Bond characteristics of SFRP composites containing FRP core/anchors coated on geopolymer mortar

Khalid, Hammad R.,Ha, S.K.,Park, S.M.,Wang, Zhen,Lee, H.K. Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.189 No.-

<P><B>Abstract</B></P> <P>The present study investigates the bending bond characteristics of novel hybrid sprayed fiber-reinforced polymer (SFRP) composites containing fiber core/anchors. Carbon or basalt fiber cores were embedded in SFRP composites as core reinforcements, and of which their ends were inserted into the beams to act as anchors. Four-point bending bond tests were conducted to characterize the bonding behavior of these hybrid SFRP composites in terms of enhancement of the ultimate bond strength ( <SUB> τ u </SUB> ) . The effects of the type and number of FRP core/anchors on <SUB> τ u </SUB> of SFRP-coated geopolymer mortar were investigated. Furthermore, geopolymer mortar was reinforced with 0.5 and 1.5 wt% of short steel fibers to study the effects of fibers on <SUB> τ u </SUB> , and their results were compared with the efficiency of hybrid SFRP composites. The test results revealed that the hybrid SFRP composites had significant effects on the bond strength, and their bonding performance was relatively better than the fiber-reinforcement in geopolymer mortar. About 46% and 37% increments were observed in <SUB> τ u </SUB> through the use of hybrid SFRP composites and steel fiber-reinforcement, respectively. The effective bond length ( <SUB> L e </SUB> ) of hybrid SFRP composites was approximately 39 mm.</P>

실규모 현장시험을 통한 부착형 암반앵커의 인발저항력 평가

김대홍,오기대 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.10

This paper presents the results of full-scale uplift load tests performed on 24 passive anchors grouted to various lengths at Okchun and Changnyong site. Rock anchors were installed over a wide range of rock types and qualities with a fixed anchored depth of 1∼6 m. The majority of installations used D51 mm high grade steel rebar to induce rock failure prior to rod failure. However, a few installations included the use of D32 mm rebar at relatively deeper anchored depth so as to induce rod failure. In many tests, rock failure was reached and the ultimate loads were recorded along with observations of the shape and extent of the failure surface. In addition to field tests, laboratory pullout tests were conducted to determine bond strength and bond stress-shear slip relation at the tendon/grout interface when a corrosion protection sheath is installed in the cement-based grout. The test results show that the ultimate tendon-grout bond strength is measured from 18∼25% of unconfined compressive strength of grout. One of the important results from these tests is that the measured strains along the corrosion protection sheath were so small that practically the reduction of bond strength by the presence of sheath would be negligible.

Theoretical determination of stress around a tensioned grouted anchor in rock

Showkati, Alan,Maarefvand, Parviz,Hassani, Hossein Techno-Press 2015 Geomechanics & engineering Vol.8 No.3

A new theoretical approach for analysis of stress around a tensioned anchor in rock is presented in this paper. The solution has been derived for semi-infinite elastic rock and anchor and for plane strain conditions. The method considers both the anchor head bearing plate and its grouted bond length embedded in depth. The solution of the tensioned rock anchor problem is obtained by superimposing the solutions of two simpler but fundamental problems: A distributed load applied at a finite portion (bearing plate area) of the rock surface and a distributed shear stress applied at the anchor-rock interface along the bond length. The solution of the first problem already exists and the solution of the shear stress distributed along the bond length is found in this study. To acquire a deep understanding of the stress distribution around a tensioned anchor in rock, an illustrative example is solved and stress contours are drawn for stress components. In order to verify the results obtained by the proposed solution, comparisons are made with finite difference method (FDM) results. Very good agreements are observed for the teoretical results in comparison with FDM.

풍화암에 근입된 영구 앵커의 극한인발력

유남재,박병수,정길수,김진황 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

The purpose of this study is to estimate ultimate uplift capacity of permanent anchor which was cast into weathered rock. The ultimate uplift capacity was estimated from the load-displacement curve of four different anchors which have different bond length. The creep test was performed for 15minutes under the maximum load of each step in order to understand the load-transfer property of permanent anchor and to decide which anchor to choose. The destruction range of soil due to the changes in load was estimated by installing dial gauge on the ground which was cast into the weathered rock. Ultimately, the study on the behavior of the anchor case into the weathered rock was performed by comparing and analyzing the estimated result of the UUC obtained by the full scale pull out test in the field with the exsting theoretical and practical results of soil and rock anchor.

전단 하중을 경험한 후설치 고전단 링앵커의 인장 강도

전상현,천성철,김재열 한국공간구조학회 2018 한국공간구조학회지 Vol.18 No.4

Tensile load tests were conducted on High-Shear Ring Anchors (HRAs) after shear load had been applied to the HRAs, which had been developed to reduce the number of the anchors. Test variables include the embedment length of the rod and the width of the specimens and a total of 12 specimens were tested. Test results show that the HRAs pulled out due to bond failure or steel failure occurred in case that the HRAs were installed to the members with 300mm or greater width and the embedment length of 160mm (the actual embedment of rod is 140mm) or deeper. Except 4 HRAs showing steel failure of rod, the minimum and average of test-to-prediction by ACI 318-14 ratios are 1.18 and 1.79, respectively. The tensile strength of HRAs, after shear load was applied to the HRAs, can be safely evaluated by the minimum among the concrete breakout strength and bond strength with the actual embedment length of the rod.