Piezoelectric skin sensor for electromechanical impedance responses sensitive to concrete damage in prestressed anchorage zone

Ngoc-Loi Dang,Quang-Quang Pham,Jeong-Tae Kim 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.6

This study presents a numerical investigation on the sensitivity of electromechanical (EM) impedance responses toinner damaged concrete of a prestressed anchorage zone. Firstly, the Ottosen yield criterion is selected to simulate the plasticity behavior of the concrete anchorage zone under the compressive loading. Secondly, several overloading cases are selected to analyze inner damage formations in the concrete of the anchorage zone. Using a finite element (FE) model of the anchorage zone, the relationship between applied forces and stresses is analyzed to illustrate inner plasticity regions in concrete induced by the overloading. Thirdly, EM impedance responses of surface-mounted PZT (lead-zirconate-titanate) sensors are numerically acquired before and after concrete damage occurrence in the anchorage zone. The variation of impedance responses is estimated using the RMSD (root-mean-square-deviation) damage metric to quantify the sensitivity of the signals to inner damaged concrete. Lastly, a novel PZT skin, which can measure impedance signatures in predetermined frequency ranges, is designed for the anchorage zone to sensitively monitor the EM impedance signals of the inner damaged concrete. The feasibility of the proposed method is numerically evaluated for a series of damage cases of the anchorage zone. The results reveal that the proposed impedance-based method is promising for monitoring inner damaged concrete in anchorage zones.

Shear Performance of Wood-Concrete Composite II -Shear Performance with Different Anchorage Length of Steel Rebar in Concrete-

Sang Joon Lee,Chang Deuk Eom,Kwang Mo Kim 한국목재공학회 2012 목재공학 Vol.40 No.5

Wood and concrete show significantly different physical properties, and it need to be firstly understood for using wood-concrete composite. This study is performed for compensating this and effective hybridization of wood and concrete. This research in planned for wood-concrete composite after previous research which deals the shear performance with different anchorage length of steel rebar in wood. Yield mode and reference design value (Z) were derived using EYM (European Yield Model). And the yield mode changed before and after anchorage length of 10∼15 mm - Is mode to IV mode. There was not increasing tendency of shear performance with increased anchorage length for over 20 mm of anchorage in concrete. And wood composite shows 65% and 93% on initial stiffness and yield load respectively compared with the wood-concrete composite. Wood-concrete composite showed brittle failure after yield point while wood-to-wood composite showed ductile failure.

Research on Whole‑Process Tensile Behavior of Headed Studs in Steel–Concrete Composite Structures

Liang?Dong Zhuang,Hong?Bing Chen,Yuan Ma,Ran Ding 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.4

The headed studs have been widely applied in steel–concrete composite structures as shear connectors. However, the tensile performance of headed studs is also key to the structural performance in many cases such as the semi-rigid composite joints including steel beam–concrete wall joint and steel column–base joint. Therefore, this study presents experimental and analytical study on the whole-process tensile behavior of headed studs. Tests on a total of 33 pullout specimens are first conducted. The tensile capacity and load–deformation behavior of the anchorage concrete, which dominates the structural performance of headed studs, are thoroughly analyzed. In addition, test data in the literature are collected for quantitatively evaluating the influence of embedment depth, bearing area, boundary conditions, and concrete strength on the tensile behavior of the anchorage concrete. On the basis of the influence evaluation, an analytical model represented by a piecewise function is proposed to describe the whole-process load–deformation behavior of the anchorage concrete and validated through the comparison between the predicted curves and all collected experimental results. Then the proposed model is applied to simulate the rotational behavior of the typical semi-rigid joint anchored by headed studs, which takes the contribution of the anchorage concrete into consideration, and is verified by experimental results. The research findings indicate that tensile behavior of anchorage concrete is crucial to the structural performance of semi-rigid joints, even for headed studs with large embedment depth and bearing area.

Estimation of transfer lengths in precast pretensioned concrete members based on a modified thick‐walled cylinder model

Han, Sun‐,Jin,Lee, Deuck Hang,Cho, Sang‐,Heum,Ka, Soon‐,Beum,Kim, Kang Su Ernst Sohn 2016 Structural Concrete Vol.17 No.1

<P><B>Abstract</B></P><P>In pretensioned concrete members, prestress is introduced by the bond mechanism between prestressing tendon and surrounding concrete. Therefore, to secure the intended level of effective prestress in the tendon, sufficient bond stresses between the prestressing tendon and the concrete should be developed at release, for which a certain length from the end of the pretensioned concrete member is required, and this required distance is defined as the transfer length of the prestressing tendon. In this study, the prestress introduction mechanism between concrete and prestressing tendon was mathematically formulated based on thick‐walled cylinder theory (TWCT). On this basis, an analytical model for estimating the transfer length was presented. The proposed model was also verified through comparison with test results collected from the literature. It was confirmed that the proposed model can accurately evaluate the effects of influential factors – such as diameter of prestressing tendon, compressive strength of concrete, concrete cover thickness and magnitude of initial prestress – on the transfer lengths of prestressing tendons in various types of pretensioned concrete member.</P>

1-D CNN deep learning of impedance signals for damage monitoring in concrete anchorage

Quoc-Bao Ta,Quang-Quang Pham,Ngoc-Lan Pham,Jeong-Tae Kim Techno-Press 2023 Structural monitoring and maintenance Vol.10 No.1

Damage monitoring is a prerequisite step to ensure the safety and performance of concrete structures. Smart aggregate (SA) technique has been proven for its advantage to detect early-stage internal cracks in concrete. In this study, a 1-D CNN-based method is developed for autonomously classifying the damage feature in a concrete anchorage zone using the raw impedance signatures of the embedded SA sensor. Firstly, an overview of the developed method is presented. The fundamental theory of the SA technique is outlined. Also, a 1-D CNN classification model using the impedance signals is constructed. Secondly, the experiment on the SA-embedded concrete anchorage zone is carried out, and the impedance signals of the SA sensor are recorded under different applied force levels. Finally, the feasibility of the developed 1-D CNN model is examined to classify concrete damage features via noise-contaminated signals. The results show that the developed method can accurately classify the damaged features in the concrete anchorage zone.

Experimental and analytical behaviour of cogged bars within concrete filled circular tubes

Tilak Pokharel,Huang Yao,Helen M. Goldsworthy,Emad F. Gad 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.5

Recent research on steel moment-resisting connection between steel beams and concrete filled steel tubes has shown that there are considerable advantages to be obtained by anchoring the connection to the concrete infill within the tube using anchors in blind bolts. In the research reported here, extensive experimental tests and numerical analyses have been performed to study the anchorage behaviour of cogged deformed reinforcing bars within concrete filled circular steel tubes. This data in essential knowledge for the design of the steel connections that use anchored blind bolts, both for strength and stiffness. A series of pull-out tests were conducted using steel tubes with different diameter to thickness ratios under monotonic and cyclic loading. Both hoop strains and longitudinal strains in the tubes were measured together with applied load and slip. Various lead-in lengths before the bend and length of tailed extension after the bend were examined. These dimensions were limited by the dimensions of the steel tube and did not meet the requirements for “standard” cogs as specified in concrete standards such as AS 3600 and ACI 318. Nevertheless, all of the tested specimens failed by bar fracture outside the steel tubes. A comprehensive 3D Finite Element model was developed to simulate the pull-out tests. The FE model took into account material nonlinearities, deformations in reinforcing bars and interactions between different surfaces. The FE results were found to be in good agreement with experimental results. This model was then used to conduct parametric studies to investigate the influence of the confinement provided by the steel tube on the infilled concrete.

Experimental study on RC beams externally bonded by CFRP sheets with and without end self-locking

Chaoyang Zhou,Yanan Yu,Chengfeng Zhou,Xuejun He,Yi Wang 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.48 No.5

To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

The anchorage-slip effect on direct displacement-based design of R/C bridge piers for limiting material strains

P.E. Mergos 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.6

Direct displacement-based design (DDBD) represents an innovative philosophy for seismic design of structures. When structural considerations are more critical, DDBD design should be carried on the basis of limiting material strains since structural damage is always strain related. In this case, the outcome of DDBD is strongly influenced by the displacement demand of the structural element for the target limit strains. Experimental studies have shown that anchorage slip may contribute significantly to the total displacement capacity of R/C column elements. However, in the previous studies, anchorage slip effect is either ignored or lumped into flexural deformations by applying the equivalent strain penetration length. In the light of the above, an attempt is made in this paper to include explicitly anchorage slip effect in DDBD of R/C column elements. For this purpose, a new computer program named RCCOLA-DBD is developed for the DDBD of single R/C elements for limiting material strains. By applying this program, more than 300 parametric designs are conducted to investigate the influence of anchorage slip effect as well as of numerous other parameters on the seismic design of R/C members according to this methodology.

노후화 모사 콘크리트와 후설치 앵커의 정착성능에 관한 실험적 연구

김정연,조승호,노영숙 대한건축학회 2022 대한건축학회논문집 Vol.38 No.4

An experimental study was conducted on the anchorage performance of post-installed anchors according to aged concrete. An aging simulation was performed by assuming the surface aging depth was 10, 20, 30, 40, 50mm and setting the compressive strength of concrete after 40, 30, and 20 years of construction to 10MPa, 15MPa, and 21MPa. As a result of this experiment, for both the 30-year and 40-year aging simulation groups, the pull-out strength before the aging simulation depth of 30mm showed a difference of less than 10% from the test with a 24MPa compressive strength. The strength decreased rapidly after the simulation depth of 40mm; it was found to show a difference within 20% compared to 18MPa concrete. In addition, the pulling strength increased as the embedding depth of the anchored concrete increased. The verticality of the anchor and the drilling depth of the concrete were affected at the aging simulation depth of 10 to 30mm. 본 연구에서는 노후화 콘크리트에 따른 후설치앵커의 정착성능에 대한 실험적 연구로, 표면 노후화 깊이 (10, 20, 30, 40, 50mm)와 건설연수 40, 30, 20년에 대한 콘크리트의 압축강도를 10, 15, 21 MPa로 설정하여 노후화 모사를 진행하였다. 실험 결과, 30년 및 40년 노후화 모사 시험군에서 깊이 30mm 이전의 인발 강도는 24MPa 강도와 10% 미만의 차이를 보였으며 40mm이후 급격한 강도가 저하를 나타났고, 10~30mm에서는 앵커의 수직도와 콘크리트의 천공 깊이의 영향을 받는 것으로 나타났다

발파 암반-콘크리트 경계면에서의 전단거동특성에 대한 수치해석적 연구

민경조,고영훈,Daisuke fukuda,오세욱,김정규,정문경,조상호 대한화약발파공학회 2019 화약발파 Vol.37 No.4

In designing a gravity-type anchorage of earth-anchored suspension bridge, the contact friction between a blasted rock mass and the concrete anchorage plays a key role in the stability of the entire anchorage. Therefore, it is vital to understand the shear behavior of the interface between the blasted rock mass and concrete. In this study, a portable 3D LiDAR scanner was utilized to scan the blasted bottom surfaces, and rock surface roughness was quantitatively analyzed from the scanned profiles to apply to 3D FEM modelling. In addition, based on the 3D FEM model, a three-dimensional dynamic fracture process analysis (DFPA-3D) technique was applied to study on the shear behavior of the interface between blasted rock and concrete through direct shear tests, which was analyzed under constant normal load (CNL). The effects of normal stress and the joint roughness on shear failure behavior are also analyzed. 타정식 현수교의 중력식 앵커리지를 설계하는 데 있어, 지반과 콘크리트 앵커블록 사이에 작용하는 접촉마찰력은 교량의 주케이블의 장력을 지지하는데 많은 기여를 하고 있기 때문에 콘크리트와 암반 사이 접촉면의마찰 및 전단 저항 특성을 이해하는 것이 중요하다. 이를 위해, 본 연구에서는 휴대용 레이저 스캐너를 활용하여발파 바닥면을 스캐닝하였으며, 이를 바탕으로 3차원 모델링 및 거칠기를 정량적으로 분석하였다. 또한 발파 바닥암반 단면 데이터를 활용하여, 발파 바닥암반-콘크리트 경계면을 갖는 모델을 생성하였다. 동적파괴과정해석기법(DFPA-3D)를 활용하여, 해당 모델에 대한 직접 전단시험 모사를 수행하였으며, 이를 바탕으로 발파 바닥암반- 콘크리트 접촉면에 대한 전단파괴 거동을 확인 및 분석하였다.