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Monitoring systems currently applied to concrete bridges include strain gauges, inclinometers, accelerometers and displacement transducers. In general, vertical displacements are one of the parameters that more often need to be assessed because their information reflects the overall response of the bridge span. However, the implementation of system...
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... procedure was first assessed on a simply supported prestressed concrete beam with a 150 mm × 200 mm cross-section and an effective span of 3.96 m (Fig. 5). A concrete of class C40/50 and steel of class S500 were used. The longitudinal reinforcement consists of 4φ12 mm, while for the transversal direction the reinforcement is set by 2φ6 mm 10 cm spaced. Additionally, the beam was prestressed with a force of 172 kN, by using a seven-wire strand with a 1.40 cm 2 cross-section and yield ...
Context 2
... illustrated in Fig. 5, three cross-sections, S1, S2 and S3, are monitored with six electric strain gauges each, two sensors being embedded into concrete (CD) and the remaining four bonded to the reinforcement bars (SD). Additionally, the vertical displacements on cross-sections SA, SB and SC were measured with LVDT's, and the rotations at the two end ...
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Citations
... In addition, it has given higher accuracy compared to other monitoring techniques relying on foil-type strain gages. Helder Sousa et al [2] estimated bridge deflection of pre-stressed concrete beam in order to appraise its performance in laboratory conditions. The evaluation of the bridge deflection based on rotation measurements, the obtained results allowed for the definition of the relative position of the inclinometers for both bridges erected using the balanced cantilever method. ...
This paper presents a comprehensive study of the interpretation of changes in stress measurements using strain gauges during stressing of prestressed cables in a bridge span. The use of prestressed concrete in bridge construction has become prevalent owing to its ability to counteract tensile stresses and enhance structural integrity. Strain gauges are commonly employed to monitor the stress levels within the prestressing cables during the stressing process. This paper employs computer simulations to analyze and interpret the changes in stress measurements obtained from strain gauges during cable stressing, contributing to a deeper understanding of the structural behavior and load distribution. The study employs a finite element analysis (FEA) to simulate the cable stressing process, providing insights into the stress redistribution within the bridge span. The findings highlight the significance of accurate stress interpretation in ensuring the safety and efficiency of pre-stressed concrete bridge structures.
... Sun et al. [4] proposed a novel method for bridge displacement estimation based on inclinometer data by developing a hybrid monitoring algorithm that uses the finite-element model and the monitored data. In addition, placing a tiltmeter or strain gauge is also an effective method of monitoring deflection [5]. Penuntun et al. [6] proposed a new method depending on the Lagrange Interpolation Half approach to obtain deflection data from rotational data; they examined the deflection of a cable-stayed bridge using tiltmeters and approved the accuracy of the proposed method. ...
Deflection is one of the main parameters often required to reflect and monitor the overall health state of bridge structures. Several approaches have been developed to monitor deflection accurately and economically. This research proposes a theoretical method to estimate the maximum deflection of the longest section of a seven-span continuous bridge using stress data collected through strain gauges. Firstly, initial data were collected from field tests under various controlled loadings to obtain the maximum deflections and stresses. Then, the stress-deflection regression equations are derived to reconstruct deflection from estimated gauges. Finally, the maximum deflection values are compared with analytical results using finite element simulations to verify the method’s effectiveness.
... Furthermore, none of the previous studies anticipate the results presented here from a methodological perspective. Some representative contributions can be found in [38][39][40][41][42]. ...
The deformation of press bolster plates under load can significantly impact the quality of manufactured workpieces. Consequently, press manufacturers are usually obliged to provide the metric proof of the permissible deformation values during the press commissioning process. Unfortunately, the existing measurement methods for determining bolster plate deformations present flaws in the measurement accuracy, the application flexibility, the metrological effort, and other aspects. These issues have been addressed through the development of a new measurement method using multiple inclination profiles on the surface of the measured object. Based on the difference in the inclination between the unloaded and loaded states, the method approximates the inclination surface and calculates the deformation of the measured object through integration. The measurement method was first used for commissioning tests of forming presses. A comparison with the results obtained with a measurement frame equipped with high-resolution measurement probes demonstrates an accuracy of the new method of less than 20 µm.
... The method was validated for both static and dynamic deflections using laboratory-scale and full-scale tests. Using inclinometers and strain gauges, [21] showed that polynomial functions can be used to estimate bridge deflections, with the procedure tested on a prestressed concrete beam and two full-scale bridges built using the balanced cantilever method. [22] proposed using similar inclinometers along with a placement optimisation method to calculate dynamic bridge deflections on a full-scale high-speed railway bridge. ...
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... However, the neutral axis may be shifted in response to temperature variations or if any physical damage such as cracking was present. These structural complexities can be resolved by defining the curvature, κ, as the difference in strain measurements at two arbitrary positions in the cross-section divided by their distance of separation [19]. ...
... Future condition evaluations will then compare their assessment to the initial conditions. In their studies, Sousa et al. [33] stated that vertical deflection is related to bridge performance under short-term and longterm observations. This paper reports a recent investigation as the initial step in the structural health behavior of a continuous long-span box girder bridge with a main span that extends to 148 m in Hungary. ...
This paper presents the results of a recent field test carried out before the opening phases of the Szapáry motorway bridge across the Tisza River in central Hungary. The evaluation test was based on static and dynamic load tests that provided information on deflection, stresses, and dynamic mode shapes along the bridge. The structure has two large continuous independent steel box girders that cover spans across the floodplain and river. Various configurations of truck loading applied up to 6400 kN of loading on the deck. During the static tests, string potentiometers recorded deflections at mid-span. Additionally, strain gauges enabled strain/stress measurements at the mid-point of the longest span and directly above one support. Dynamic loadings showed variation in deflection response due to vehicle speed, and ambient vibration testing led to determining vibration modes and frequencies. A three-dimensional finite-element model produced similar deflections, stresses, and modal behavior. Measured and modeled deflections and stresses indicated that the bridge performed within design margins. The testing and analysis results will be part of a future program assessing conditioned-based maintenance.
... Since strain is strongly related to the behavior of individual structural members, it is considered to be more appropriate as a damage evaluation index than acceleration. Many attempts have been made to detect fractures in civil infrastructure using strain gauges and optical fiber sensors to measure traffic load and changes in stress distribution (Brownjohn et al. 2007;Catbas et al. 2002;Kobayashi et al. 2004;Li et al. 2006;Liu et al. 2009;Miura et al. 1994;Pines et al. 2002;Reynders et al. 2007;Sousa et al. 2013;Toyota et al. 2008). For building structures, Kurata et al. (2013) and Matarazzo et al. (2018) proposed the use of piezoelectric sensors to measure the strain at the lower flange of beam ends and compared the strain amplitudes before and after seismic loading to detect the reduction in cross-sectional area due to crack propagation or fracture. ...
Large-span steel structures have been widely adopted in stadiums, airports, factories, and train stations because they provide a large space for multi-functional use. To ensure business continuity, post-earthquake damage surveys and structural status estimation of such important and large-spaced buildings have attracted increasing attention. Structural health monitoring of buildings using accelerometers is already in widespread use; however, measuring the acceleration response alone cannot directly estimate the damage of individual structural members. Another potential approach is to measure strain; however, its application to building structures is very limited. The goal of this study is to establish a method for quantitatively determining the damage of a large-scale truss structure immediately after an earthquake. Truss structure specimens were statically loaded or shaken by a shaking table to cause buckling damage, and the relationship between the changes in acceleration and strain response before and after buckling and the progress of the damage were investigated. The response properties of both acceleration and strain changed as buckling damage progressed. However, the strain amplitude measured on the chord members showed significant change according to the progress of buckling damage, while the changes in the predominant frequency and mode shape calculated from the acceleration response were small. It was shown that the observed out-of-plane deformation was almost linear to the strain response, indicating the possibility of quantitative assessment of damage by strain measurement.
... Tese commercial instruments can achieve stable and accurate static defection measurements, albeit only at certain structure points. Te points defection measurement is often unsatisfactory, and the inclinometer is often employed to reconstruct the static defection curve of the entire bridge [5,6]. ...
... Moving average Using Eq. (6)(7)(8)(9)(10)(11)(12)(13)(14) Frequency response ...
Structural health monitoring (SHM) is widely applied to assess the service condition of bridges. Defection measurements are essential to determine a bridge's performance, and in particular, dynamic defection is increasingly required in SHM. However, continuous and high-precision measurements of the absolute dynamic defection are challenging without a reference point placed at a distance from the bridge. We proposed a reference point-free dynamic defection measurement system consisting of a level sensor and an accelerometer. Te level sensor measures the low-frequency defection components, while the accelerometer measures the high-frequency defection components. We redesigned the level sensor from the hydrostatic level sensor and further provided a correction method to achieve the dynamic defection measurement. A numerical algorithm fuses the signals from the level sensor and accelerometer to obtain the absolute dynamic defection, and key parameters are calculated. Te accuracy of the measurement system was tested in the laboratory, and the sensor results were similar to the ones obtained by the laser test under simple harmonic and random excitation. Field tests conducted on a T-shaped rigid frame bridge with random traffic flow indicate that the system can achieve continuous high-precision defection measurements of bridges loaded by traffic flow.
... In addition, several scholars (such as [40][41][42]) reported the traditional use of inclinometers studying the boundary condition response of the bridge abutments. Another common use of these types of sensors is the calculation of bridge deck deflections [43][44][45]. Table 1 illustrates the characteristics of some of the commercially available inclinometers and is sorted by the price of the sensors. This information includes the measurement range, the resolution, the sampling rate and the cost of the introduced inclinometers. ...
Structural damage detection using inclinometers is getting wide attention from researchers. However, the high price of inclinometers limits this system to unique structures with a relatively high structural health monitoring (SHM) budget. This paper presents a novel low-cost inclinometer, the low-cost adaptable reliable angle-meter (LARA), which combines five gyroscopes and five accelerometers to measure inclination. LARA incorporates Internet of Things (IoT)-based microcontroller technology enabling wireless data streaming and free commercial software for data acquisition. This paper investigates the accuracy, resolution, Allan variance and standard deviation of LARA produced with a different number of combined circuits, including an accelerometer and a gyroscope. To validate the accuracy and resolution of the developed device, its results are compared with those obtained by numerical slope calculations and a commercial inclinometer (HI-INC) in laboratory conditions. The results of a load test experiment on a simple beam model show the high accuracy of LARA (0.003 degrees). The affordability and high accuracy of LARA make it applicable for structural damage detection on bridges using inclinometers.
... Recently, Popescu et al. [4] compared modern techniques and found close-range photogrammetry (CRP) to be more efficient and costeffective for bridge inspection. A summary of the obtained accuracy from modern and traditional methods over the last twenty years is presented in Figure 1 [5][6][7][8][9][10][11][12][13][14][15][16][17]. Off-site bridge inspection can be carried out using unmanned aerial vehicles (UAVs) equipped with sensors such as laser scanners, and infrared, ultrasonic, or digital single-lens reflex (DSLR) cameras. ...
For the inspection of structures, particularly bridges, it is becoming common to replace humans with autonomous systems that use unmanned aerial vehicles (UAV). In this paper, a framework for autonomous bridge inspection using a UAV is proposed with a four-step workflow: (a) data acquisition with an efficient UAV flight path, (b) computer vision comprising training, testing and validation of convolutional neural networks (ConvNets), (c) point cloud generation using intelligent hierarchical dense structure from motion (DSfM), and (d) damage quantification. This workflow starts with planning the most efficient flight path that allows for capturing of the minimum number of images required to achieve the maximum accuracy for the desired defect size, then followed by bridge and damage recognition. Three types of autonomous detection are used: masking the background of the images, detecting areas of potential damage, and pixel-wise damage segmentation. Detection of bridge components by masking extraneous parts of the image, such as vegetation, sky, roads or rivers, can improve the 3D reconstruction in the feature detection and matching stages. In addition, detecting damaged areas involves the UAV capturing close-range images of these critical regions, and damage segmentation facilitates damage quantification using 2D images. By application of DSfM, a denser and more accurate point cloud can be generated for these detected areas, and aligned to the overall point cloud to create a digital model of the bridge. Then, this generated point cloud is evaluated in terms of outlier noise, and surface deviation. Finally, damage that has been detected is quantified and verified, based on the point cloud generated using the Terrestrial Laser Scanning (TLS) method. The results indicate this workflow for autonomous bridge inspection has potential.
