Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

AbstractCombination of carbon fiber reinforced polymer (CFRP) tendon and reinforced concrete encased steel composite (RCESC) beam can improve the workability and the energy dissipation capacity of members. In this paper, three RCESC beams reinforced with steel bars or CFRP bars were designed and fabricated to study the bond-slip behavior between I-shaped steel and CFRP reinforced concrete and the damage states between bond-slip interfaces of the beams. The lead zirconate titanate (PZT) patch as stress wave actuator, the smart aggregates (SAs) were installed in concrete as the sensors to collect the stress wave signal. A method based on piezoelectric active sensing was developed to monitor the bond-slip damage of CFRP-RCESC beam. The changes of responding signals were characterized in time- and frequency- domains. The characteristic information of bond-slip damage was further quantified by wavelet packet energy. Results show the bond-slip resistance of the CFRP-RCESC beams can be improved by increasing reinforcement ratio and elastic modulus of the main bars. The bond-slip damage process of the specimens can be effectively monitored by the active sensing method.

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Old - New Concrete Interfacial Bond Slip Monitoring in Anchored Rebar Reinforced Concrete Structure Using PZT Enabled Active Sensing

Frontiers in Materials ◽

10.3389/fmats.2021.723684 ◽

2021 ◽

Vol 8 ◽

Author(s):

Jian Jiang ◽

Yixuan Chen ◽

Junwu Dai

Keyword(s):

Wavelet Packet ◽

Concrete Specimen ◽

Shear Loading ◽

Shear Capacity ◽

Active Sensing ◽

Reinforced Concrete Structure ◽

Interfacial Bond ◽

Shear Forces ◽

Loading Test ◽

Bond Slip

Post-installed anchor technology is widely used for structural strengthening and for retrofitting existing constructions. The old–new concrete interface associated with using this technology is of great significance in the shear capacity of concrete structural member under shear forces. For such members, interface failures usually occur with bond slip. In this paper, an application of a piezoceramic enabled active sensing technique is put forward to monitor Old - New concrete interfacial bond slip. Three concrete specimens (S1, S2, and S3) are fabricated and each specimen consists of two parts. Each part is made of concrete poured at different times, and both are bonded with an anchored rebar embedded inside the specimen. Two PZT aggregates bonded to opposing sides of the concrete specimen helped to realize active sensing. During the shear loading test, both the load values and the signals from sensors are acquired every 20 s. The test durations of S1, S2 and S3 lasted 960, 1,120, and 1,110 s, respectively. Furthermore, the received signal energies are quantified through wavelet packet analysis to monitor the Old - New concrete interfacial bond slip process. The experimental results show that the change of WPEI in the received signals has a direct relation with the severity of the Old - New concrete interfacial bond slip. Moreover, the PZT-based active sensing approach is feasible to monitor the shear-induced bond slip in Old - New concrete interfaces.

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Real-Time Monitoring of Bond Slip between GFRP Bar and Concrete Structure Using Piezoceramic Transducer-Enabled Active Sensing

Sensors ◽

10.3390/s18082653 ◽

2018 ◽

Vol 18 (8) ◽

pp. 2653 ◽

Cited By ~ 43

Author(s):

Kai Xu ◽

Changchun Ren ◽

Qingshan Deng ◽

Qingping Jin ◽

Xuemin Chen

Keyword(s):

Stress Wave ◽

Lead Zirconate Titanate ◽

Concrete Structure ◽

Concrete Structures ◽

Fiber Reinforced Polymers ◽

Active Sensing ◽

Monitoring Method ◽

Bond Slip ◽

Pull Out ◽

Gfrp Bar

Glass fiber-reinforced polymers (GFRPs) have received increasing attention in recent years due to their overall performance of light weight, low cost and corrosion resistance, and they are increasingly used as reinforcement in concrete structures. However, GFRP material has low elastic modulus and linear elastic properties compared with steel bars, which introduces different bonding characteristics between bars and concrete. Therefore, a reliable monitoring method is urgently needed to detect the bond slip in GFRP-reinforced concrete structures. In this paper, a piezoceramic-based active sensing approach is proposed and developed to find the debonding between a GFRP bar and the concrete structure. In the proposed method, we utilize PZT (lead zirconate titanate) as two transducers. One acts as an actuator which is buried in the concrete structure, and the other acts as a sensor which is attached to the GFRP bar by taking advantage of machinability of the GRRP material. Both transducers are strategically placed to face each other across from the interface between the GFRP bar and the concrete. The actuator provokes a stress wave that travels through the interface. Meanwhile, the PZT patch that is attached to the GFRP bar is used to detect the propagating stress wave. The bonding condition determines how difficult it is for the stress wave traveling through the interface. The occurrence of a bond slip leads to cracks between the bar and the concrete, which dramatically reduces the energy carried by the stress wave through the interface. In this research, two specimens equipped with the PZT transducers are fabricated, and pull-out tests are conducted. To analyze the active sensing data, we use wavelet packet analysis to compute the energy transferred to the sensing PZT patch throughout the process of debonding. Experimental results illustrate that the proposed method can accurately capture the bond slip between the GFRP bar and the concrete.

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Liver Elastography in Healthy Children Using Three Different Systems – How Many Measurements Are Necessary?

Ultraschall in der Medizin - European Journal of Ultrasound ◽

10.1055/a-1283-5906 ◽

2020 ◽

Author(s):

Anders Batman Mjelle ◽

Anesa Mulabecirovic ◽

Roald Flesland Havre ◽

Edda Jonina Olafsdottir ◽

Odd Helge Gilja ◽

...

Keyword(s):

Shear Wave ◽

Transient Elastography ◽

Intraclass Correlation ◽

Age Groups ◽

Liver Stiffness ◽

Shear Wave Elastography ◽

Healthy Children ◽

Significant Difference ◽

Pediatric Liver Disease ◽

Liver Elastography

Abstract Purpose Liver elastography is increasingly being applied in screening for and follow-up of pediatric liver disease, and has been shown to correlate well with fibrosis staging through liver biopsy. Because time is of the essence when examining children, we wanted to evaluate if a reliable result can be achieved with fewer acquisitions. Materials and Methods 243 healthy children aged 4–17 years were examined after three hours of fasting. Participants were divided into four age groups: 4–7 years; 8–11 years; 12–14 years and 15–17 years. Both two-dimensional shear wave elastography (2D-SWE; GE Logiq E9) and point shear wave elastography (pSWE; Samsung RS80A with Prestige) were performed in all participants, while transient elastography (TE, Fibroscan) was performed in a subset of 87 children aged 8–17 years. Median liver stiffness measurement (LSM) values of 3, 4, 5, 6, 7, and 8 acquisitions were compared with the median value of 10 acquisitions (reference standard). Comparison was performed for all participants together as well as within every specific age group. We investigated both the intraclass correlation coefficient (ICC) with absolute agreement and all outliers more than 10 %, 20 % or ≥ 0.5 or 1.0 kPa from the median of 10 acquisitions. Results For all three systems there was no significant difference between three and ten acquisitions, with ICCs ≥ 0.97. All systems needed 4 acquisitions to achieve no LSM deviating ≥ 1.0 kPa of a median of ten. To achieve no LSM deviating ≥ 20 % of a median of ten acquisitions, pSWE and TE needed 4 acquisitions, while 2D-SWE required 6 acquisitions. Conclusion Our results contradict recommendations of 10 acquisitions for pSWE and TE and only 3 for 2D-SWE.

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