Long-term structural health monitoring (SHM) plays an important role in the safety of public transport infrastructure such as bridges or tunnels and warns in the event of any emerging problem. This ...article describes development and testing of system based on fiber Bragg grating (FBG) sensors that can detect changes in strain and temperature. The first phase of the research has been focused on the development of new fiber optic sensors for the monitoring of concrete structures and their investigation in laboratory conditions. The work also shows novel applicability of the same FBG technology for glulam structures. Mechanical loading tests of the concrete beam as well as glulam beam with embedded sensors were carried out. Data measured by developed fiber optic sensors were compared with the readings from reference sensors as well as with the analytically calculated values. The achieved results proved good agreement between the measured data, analytical data and reference methods. In second phase of the research, the pilot installation of the sensors was carried out on the newly constructed prestressed-concrete bridge. The bridge was monitored throughout pre-stressing phase and monitoring continued after the completion of the construction works. Problems with the fragility of the sensors occurred during the measurements, but the obtained results provide a good basis for further improvement of the system.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Mass timber construction systems, incorporating engineered wood products as structural elements, are gaining acceptance as a sustainable alternative to multi-story concrete or steel-frame structures. ...The relative novelty of these systems brings uncertainties on whether these buildings perform long-term as expected. Consequently, several structural health monitoring (SHM) projects have recently emerged to document their behavior. A wide and systematic use of this data by the mass timber industry is currently hindered by limitations of SHM programs. These limitations include scalability, difficulty of data integration, diverse strategies for data collection, scarcity of relevant data, complexity of data analysis, and limited usability of predictive tools. This perspective paper envisions the use of avatars as a Web-based layer on top of sensing devices to support SHM data and protocol interoperability, analysis, and reasoning capability and to improve life cycle management of mass timber buildings. The proposed approach supports robustness, high level and large-scale interoperability and data processing by leveraging the Web protocol stack, overcoming many limitations of conventional centralized SHM systems. The design of avatars is applied in an exemplary scenario of hygrothermal data reconstruction, and use of this data to compare different mold growth prediction models. The proposed approach demonstrates the ability of avatars to efficiently filter and enrich data from heterogeneous sensors, thus overcoming problems due to data gaps or insufficient spatial distribution of sensors. In addition, the designed avatars can provide prediction or reasoning capability about the building, thus acting as a digital twin solution to support building lifecycle management.
Social workers require a better understanding of the impact of pandemic measures on the level of physical activity of their clients to better target client activation. In this retrospective ...tracker-based study (two years of measurement), we examined changes in the physical activity of the elderly population (204 participants with an average age of 84.5 years) in the Czech Republic as a result of measures to prevent the spread of COVID-19. Physical activity was statistically compared according to the physical, demographic and social conditions of the participants. In addition to observing the expected activity decrease during the COVID-19 pandemic, we made several hypotheses based on the sex, age group, body mass index, type of housing (apartment or house) and size of the city of residence. We found that 33% of the 204 participants had increased levels of physical activity in the period following the COVID-19 pandemic outbreak in Central Europe. We found that the size of the city where the seniors lived and the type of housing did not affect the general level of physical activity. When comparing physical acquisition rates in each month of 2019 and 2020, we saw the largest declines in April and May 2020, that is, one month after the start of the lockdown.
•By simulating PV systems for local energy usage in households, time resolution of input data is critical if no energy storage system is present.•To keep the relative error of self-consumption index ...below 5%, time resolution of input data should not exceed 1min.•If the time resolution is below these limits, the self-consumption index is overestimated, grid interaction index is underestimated.
This article focuses on simulation accuracy of photovoltaic (PV) systems designed for local energy usage in households. The results of simulations can be misleading when the input data is estimated not correctly or the input data has a low time resolution. Load profile is difficult to estimate due to the changes in user behaviour and possible high power fluctuations. In contrast to many other studies, 15s data are used as PV power and household load data input. Using this data for simulations we show the influence of averaging interval on the results and thus we indicate the variance in the simulated system performance (rates of self-consumption, energy independence and grid interaction).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
5.
Long-Range Magnetic Tracking System Vcelak, Jan; Ripka, Pavel; Zikmund, Ales
IEEE sensors journal,
2015-Jan., 2015-1-00, Volume:
15, Issue:
1
Journal Article
Peer reviewed
Open access
This paper presents a new long-range full 3-D magnetic tracking system for horizontal directional drilling, and describes its performance. The system is able to determine the full 3-D mutual position ...of the receiver with respect to the transmitter. The system presented here belongs to the category of hybrid trackers using an active magnetic ranger, an optical gyro, and three micromachined inclinometers. The gyro is used for dead-reckoning navigation over long distances (up to 2 km), and the magnetic tracking system, consisting of a coil magnetic transmitter and a magnetometer receiver, is used when two drill heads are approaching each other beneath the surface at the assumed meeting point. The functionality of the system was verified for the maximum range of 17 m with 1,2-m rms accuracy, and with 0,34-m rms accuracy for the range below 10 m.
The paper deals with the experimental analysis focused on the determination of strain in wooden building structures using optical fibers with FBG sensors. Firstly, optical fibers were used to measure ...displacements of layers and surface strain of the lower surface of the ceiling panels made from mechanically jointed cross laminated timber (CLT). The measured displacement values of the optical fibers were compared with the results obtained from the inductive displacement sensors. Secondly, optical fibers were used for long-term monitoring of the roof structure of the sports hall. The fibers were mounted on chords of timber trusses and their correct function was verified by a load test.
Fiber Bragg Grating (FBG) sensors are used worldwide in structural health monitoring as a highly effective strain sensing method. Compared to traditional strain sensing methods in geotechnics, such ...as measurement by extensometers, deformeters, or strain gauges, FBG technology is beneficial in many issues, such as small dimensions of the sensor, easy and fast installation, long-term stability, immunity to electromagnetic interference or possibility of having dozens of sensing points on a single measuring cable. One part of the D3 highway construction, connecting the capital city Prague with southern Bohemia, is Pohůrka tunnel in the suburbs of the city of České Budějovice. With regard to the geomorphology of the locality and directional and elevational design of the highway, the tunnel is designed to be cut and cover. It has two 995.5 m long tubes, guided in two opposing curves. Due to complicated geotechnical and hydrogeological conditions in combination with demanding construction, static load tests of selected individual lamellae of diaphragm walls designed as retaining, load-bearing as well as sealing structures of the cut and cover tunnel were planned. Two test lamellae were instrumented for the purpose of static load test by resistance strain gauges, as well as FBG sensors. After the load tests, the results from both measurement technologies were compared to each other. The differences between the values obtained from FBG sensors and the values from strain gauges are acceptable enough; both measuring technologies proved their suitability in static load test of a diaphragm walls.
Recently, there has been an increased interest in structural health monitoring (SHM) of building and transport structures. Standard strain gauges placed on a beam surface are mostly used to monitor ...the mechanical stresses of timber or concrete structures. However, these sensors are susceptible to mechanical damage, electromagnetic interference or negative influences of the measured data during the measurement, such as temperature variations or potential loss of data due to explosive environment. The fibre optic sensor system offers a more suitable and reliable solution – the sensors can be integrated directly into the load bearing structure during its production and thus protected by the construction material against ambient environmental conditions. The first part of this paper presents series of environmental tests of a measuring system based on Fibre Bragg Grating principle performed from 2016 to 2018 in a climate chamber. The chamber can generate defined humidity and/or temperature cycles, which can simulate the behavior of the structure under real environmental conditions. The tested fibre optic sensor system is suitable for load bearing timber (glued laminated timber beams) and concrete structures. In the second part of this paper, mechanical loading tests of glued laminated timber beam with integrated fiber optic sensors performed in 2016, 2017 and 2018 are presented. The article describes the design of test cycles, gives the results of testing, and is concluded with the discussion of given results together with the outline of the future research directions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Measuring an arrow's ballistic performance such as arrow velocity on impact, total time of flight and arrow shaft oscillation is challenging because of the dynamic nature of arrow flight. This ...challenge becomes increasingly difficult as the distance of the shot increases. It is also of great interest to bowhunters to understand the ballistic performance of arrows that include hunting broadheads. A miniaturized, sensory data acquisition system, located in the arrow tip and engineered to withstand the high accelerations experienced at launch and impact, enables the precise measurement of arrow ballistics in flight. By continuously recording arrow drag in flight, the system enables measurement of the ballistic performance of an arrow as it travels downrange. The authors have also built an adapter that is connected to the housing of the sensing system to allow for comparative ballistic tests to be performed on hunting broadheads. Here, we present results obtained using the sensing system to perform initial testing on two commercially available broadheads at shot distances of approximately 45 m.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
