Damage-sensitive impedance sensor placement on multistrand anchorage based on local stress variation analysis

Ngoc-Loi Dang¹ | Thanh-Canh Huynh² | Quang-Quang Pham¹ | So-Young Lee³ | Jeong-Tae Kim¹

¹Department of Ocean Engineering, Pukyong National University, Busan, Republic of Korea. ²Center for Construction, Mechanics and Materials, Institute of Research and Development, Duy Tan University, Danang, 550000, Vietnam.

³Research Institute for Smart Infrastructure Technology, Department of Ocean Engineering, Pukyong National University, Busan, 48513, Republic of Korea

Correspondence

Jeong-Tae Kim, Ocean Engineering Department, Pukyong National University, 599-1 Daeyon-3dong, Nam-gu, Busan 608-737, Republic of Korea.

Summary

An important issue in impedance-based damage monitoring is to deploy sensors in proper positions in which damage-sensitive impedance responses can be captured effectively. In this study, a full-scale multi-strand anchorage is analyzed to determine optimal locations of piezoelectric sensors for impedance-based monitoring of locally damaged strands.

First, stress variations of the multi-strand anchorage are experimentally measured to estimate the anchorage behavior under the effect of locally damaged strands. Strain signals are examined for axial, circumferential, and radial stress components under the variation of prestress forces. Second, a finite element analysis is made on the multi-strand anchorage to back up the experimental findings. Third, a damage-sensitive structural model is interpreted for the local strand breakage.

 Finally, impedance responses sensitive to local strand breakage are experimentally examined for a few scenarios simulated in the anchorage system. PZT (lead zirconate titanate) sensors deployed on the anchor head and the bearing plate are evaluated to comparatively determine ideal regions of interest for impedance monitoring. The results show that the greater stress variation yields the greater variations in impedance responses and the near-top and near-anchor heads are ideal regions of interest for damage-sensitive impedance monitoring.

Keywords

Electromechanical impedance, multi-strand anchorage, prestress force, sensor placement, strand breakage detection, stress analysis

Received: 11 November 2019 Revised: 28 January 2020 Accepted: 18 February 2020

Struct Control Health Monit. 2020;e2547.

DOI: 10.1002/stc.2547

Experimental behavior of fire-exposed reinforced concrete slabs without and with FRP retrofitting

Vui Van Cao^a,b, Huy Ba Vo^c, Luan Hoai Dinh^c, Det Van Doan^d

^aFaculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Viet Nam

^bVietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Viet Nam

^cFaculty of Urban Infrastructures, Mien Tay Construction University, 20B Pho Co Dieu Street, Ward 3, Vinh Long City, Vinh Long Province, Viet Nam

^dCentre of Construction and Environment Experiment, Mien Tay Construction University, 20B Pho Co Dieu Street, Ward 3, Vinh Long City, Vinh Long Province, Viet Nam

Abstract

In this study, experiments were conducted on nine reinforced concrete slabs which were divided into three groups, namely S0, S45, and S75. Group S0 included one slab which was not exposed to fire to use as the control specimen. Each of groups S45 and S75 included four slabs which were subjected to 45 min and 75 min of fire, respectively. After exposure to fire, two fire-exposed slabs of each group were retrofitted using fiber reinforced polymer (FRP). These slabs were monotonically or cyclically loaded to failure. The test results showed that the control and fire-exposed slabs exhibited flexural failure while the FRP-retrofitted fire-exposed slabs failed in the form of FRP debonding. Fire slightly decreased the ductility but it was still much larger than 4, classifying the specimens to be highly ductile. Fire marginally reduced the yield and ultimate strengths while it significantly reduced the stiffness by about 30%. Retrofits with 1/2 and 1 FRP layer for fire-exposed slabs increased the yield strength by 30% and 45% and increased the ultimate strength by 46% and 65%, respectively. The effect of cyclic loading caused negligible strength degradation, but it caused considerable stiffness degradation of 20% and 35% for the 1/2 and 1 FRP retrofitted fire-exposed slabs, respectively. Finally, a theoretical model was developed to compute the capacity of FRP retrofitted fire-exposed slabs. The model can be useful for engineers to estimate the capacity of FRP retrofitted fire-exposed slabs in practice.

Journal of Building Engineering. Volume 51, 1 July 2022, 104315

Antimicrobials in Animal Faeces (Chicken, Cow and Swine) from The Breeding Farms in The Upstream of Sai Gon River

Le Thi Bach Tuyet¹*, Do Trong Nghia²

¹Department of Urban and Infrastructure Engineering, Mien Tay construction university (MTU), 20B, Pho Co Dieu, Ward 3, Vinh Long city, Vinh Long District, Viet Nam

²Department of Civil Engineering, Mien Tay construction university (MTU), 20B, Pho Co Dieu, Ward 3, Vinh Long city, Vinh Long District, Viet Nam

Received: 30 December 2020; Accepted for publication: 18 August 2021

Abstract

The widespread use of antimicrobials in husbandry has increased antimicrobial residues in animal faeces. Therefore, the investigation of antimicrobials in animal faeces is essential because they are the main cause of environmental pollution. This study analyzed and assessed samples of chiken, cow and swine faeces for seven antimicrobials, namely trimethoprim (TRI), ormethoprim (ORM), ofloxacin (OFL), norfloxacin (NOR), tetracycline (TET), chlortetracycline (CTE) and tylosin (TLS). Samples were taken from faeces heaps at breeding farms in the upstream of the Sai Gon river. The samples were analyzed in the laboratory by using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine antimicrobials. TRI, with the highest mean concentration, was found in all fecal samples (10,399 - 47,987 µg/kg) while ORM with the lowest average concentration was only detected in chicken fecal samples (542 µg/kg). CTE, with the second high mean concentration, was also found in all fecal samples (1,085 - 12,385 µg/kg), whereas TET was only detected in chicken fecal samples (9,050 µg/kg). OFL with the third average concentration, was also found in all fecal samples (1,516 - 9280 µg/kg), while NOR was detected in cow fecal samples at a low mean concentration (2,479 µg/kg). TLS was only found in chicken and cow fecal samples (798 - 5,802 µg/kg). These numbers show a very large amount of consumption of antimicrobials in livestock production. The results from this study are likely to encourage further monitoring of antimicrobials used in livestock production, and promote discussion of existing policies regarding the inclusion of antimicrobials in animal feed rations and veterinary medicines.

Keywords: antimicrobial, faeces, Sai Gon river, concentration, livestock.

Vietnam Journal of Science and Technology 60 (1) (2022) 105-113

DOI:10.15625/2525-2518/15811

Salinity Intrusion in the Vietnamese Mekong Delta, a Threat: Possible Causes, Effects on People’s Life and Production, and Temporary Solutions and Adaptable Strategies

Nguyen Van Tho

Mien Tay Construction University, 20B, Pho Co Dieu Street, Ward 3, Vinh Long City, Vinh Long Province, Vietnam.

Abstract

The Vietnamese Mekong Delta is the most important agricultural production area in Vietnam. Most of this deltaic plain has an extremely low mean elevation of about 0.8 m above sea level and dissected by an inter-linked system of natural rivers and man-made canals connected to the sea. It is recognized as one of the areas worldwide most vulnerable to the impacts of climate change. In recent years, saline intrusion into the Vietnamese Mekong Delta has become increasingly serious due to a combination of factors, including the low topography, a dense system of rivers and canals connected to the sea, drought, low flow rates in the Mekong River during the dry season, growing competition for rapidly depleting water resources, sea level rise, and land subsidence. In 2020 saltwater intruded further inland than ever before and affected 10 out of 13 provinces of the Vietnamese Mekong Delta, causing severe damage to millions of hectares of farming land and the livelihoods of thousands of households. Solutions and adaptation strategies include storage of fresh water in ponds, shifting to farming systems and varieties that are more resilient to high salinity, changing cropping schedules, and building sluices to regulate salt-water intrusion. This paper discusses the main causes of salt intrusion, its effects on people’s life and production, and adaptation strategies to mitigate its impacts.

Keywords: Salinity intrusion, Vietnamese Mekong Delta, Climate change.

Published 22 October 2022

The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 H.-Y. Jeon (ed.), Sustainable Development of Water and Environment, Environmental Science and Engineering,