Beam Segments Research Articles

Structural Performance of Deteriorated and Strengthened Precast Concrete Segmental Beams with Epoxy Joints under Concentric and Eccentric Loads

Structural Performance of Deteriorated and Strengthened Precast Concrete Segmental Beams with Epoxy Joints under Concentric and Eccentric Loads

A Probabilistic Model-Based Framework for Damage Detection in Beam-Like Structures Considering Temperature Effects

To improve the assessment outcomes of structural health monitoring systems, it has been acknowledged that the damage diagnostics process is associated with a considerable amount of uncertainties from operational and environmental sources such as temperature. This study presents a probabilistic framework for structural health monitoring aimed at identifying common defects such as cracks and corrosion in beam-like structures under varying temperature conditions. The framework utilizes optimization methods integrated with a probabilistic approach, comprising two levels of damage identification: first, determining the optimal probability mass function for the damage location ratio, followed by the optimal conditional for the damage depth ratio. A simply supported beam divided into four segments was modeled to evaluate the effectiveness of the proposed algorithm across various damage scenarios using frequency response signals. Structural damage was simulated by manipulating the length and depth ratios of specific beam segments. The modeling procedure for defects in the simply supported beam was validated through comparison with experimental measurements, achieving a maximum difference of less than 1%. The proposed algorithm consistently yielded improved damage detail outcomes in the second level, characterized by higher probabilities and lower uncertainties for both damage location and depth ratios. Identifying cracks and corrosion with a 0.1 depth ratio at low temperatures proved challenging, but the algorithm effectively addressed such scenarios, achieving identification probabilities exceeding 90%. The analysis outcomes demonstrate the advantages of the proposed framework for structural health monitoring that accounts for temperature effects, thereby improving the fidelity of damage assessment in real-world conditions.

Testing and Validation of the Vehicle Front Camera Verification Method Using External Stimulation.

The perception of the vehicle's environment is crucial for automated vehicles. Therefore, environmental sensors' reliability and correct functioning are becoming increasingly important. Current vehicle inspections and self-diagnostics must be adapted to ensure the correct functioning of environmental sensors throughout the vehicle's lifetime. There are several promising approaches for developing new test methods for vehicle environmental sensors, one of which has already been developed in our previous work. A method for testing vehicle front cameras was developed. In this work, the method is improved and applied again. Various test vehicles, including the Tesla Model 3, Volkswagen ID.3, and Volkswagen T-Cross, are stimulated by simulating driving scenarios. The stimulation is carried out via a tablet positioned before the camera. The high beam assist is used to evaluate the vehicle's reaction. It was observed whether the vehicle switched from high to low beam as expected in response to the stimulation. Although no general statement can be made, the principle of stimulation works. A vehicle reaction can be successfully induced using this method. In further test series, the influence of display brightness is examined for the first time in this work. The results show that the display brightness significantly influences the test procedure. In addition, the method is validated by stimulation with colored images. It is shown that no complex traffic simulation is necessary to trigger a vehicle reaction. In the following validation approach, the CAN data of the Tesla Model 3 is analyzed during the tests. Here, too, the assumption that the vehicle reaction is based solely on the detected brightness instead of identifying road users is confirmed. The final validation approach examines the method's applicability to other vehicles and high beam assist technologies. Although the method could not be used on the Volkswagen T-Cross due to a fault detected by the vehicle's self-diagnosis, it worked well on the Volkswagen ID.3. This vehicle has a dynamic light assist in which individual segments of the high beam are dimmed during stimulation. Although the method developed to stimulate vehicle front cameras is promising, the specific factors that trigger the vehicle responses remain to be seen. This uncertainty suggests that further research is needed better to understand the interaction of stimulation and sensor detection.

Method for identifying damage to stay cables based on local beam deflection

Abstract In this study, for the problem of difficulty in identifying the damage of diagonal cable using the overall beam deflection, a method of identifying the cable based on the flexibility matrix of local beam segments is proposed. The range of influence of cable damage on the deflection of beams under self-weight is investigated and analysed using the finite element method , and the results show that the damage of cables mainly affects the deflection in their vicinity, while the change of deflection at other locations is minimal; with the change of the location of damaged cables, the influence of the range also changes accordingly. Building on this, the relationship between the difference in deflection of local beams and the change in cable force before and after the cable damage is deduced by combining with the principle of structural mechanics, and the damage index ∆F is proposed, and the validity of the method is confirmed by experiments. The experimental results indicate that the deflection of the local beam can be utilized to assess the change in cable force, allowing for the identification of the damaged cable's location, specifically where the change in cable force is negative. The method is highly resistant to interference. The method can quickly and accurately locate the damaged cable.

Azimuthally segmented MIG-type electron beam for terahertz harmonic gyrotron

We propose an azimuthally segmented configuration of a MIG-type (magnetron injection gun) electron beam with azimuthal periodicity for terahertz harmonic gyrotrons, featuring enhanced mode selection. By azimuthally modulating the emitter ring of MIG into segments to generate several electron beamlets (small-orbit) evenly distributed in the electron guiding phase, we can selectively induce the degeneracy of the oppositely rotating waves of the desired harmonic mode, forming a standing-wave like pattern that nearly doubles the mode's coupling strength to the beam. The proposed approach can help to mitigate the mode competition and increase the output power of the terahertz harmonic gyrotron, paving the way for advancement in the development of gyrotrons with higher frequencies and higher harmonics.

Performance evaluation of single-cell precast concrete segmental beams under accelerated corrosion and direct load: numerical and experimental investigation

Performance evaluation of single-cell precast concrete segmental beams under accelerated corrosion and direct load: numerical and experimental investigation

Mechanical Behavior of Multiple Edge‐Cracked Nanobeams by Taking Into Account the Multiple Cracks Effects

ABSTRACTBy exploiting the stress‐driven model, within the Euler–Bernoulli beam theory, a novel nonlocal analytical model is proposed in order to simulate the mechanical behavior of multiple edge–cracked nanobeams by taking into account the multiple cracks effects. According to the present model, the nanobeam is split in correspondence with each of the edge cracks, thus obtaining beam segments, connected to each other by means of massless elastic rotational springs. Firstly, the proposed model is validated by considering experimental data available in the literature, related to bending tests on two cantilever microbeams, each of them containing a single edge crack (i.e., ). Then, the model is employed to simulate a bending test on a cracked cantilever microbeam containing two edge cracks (i.e., ) and a parametric study is performed by varying both the crack depth, the distance between cracks, and the characteristic length of the material in order to investigate the influence of such parameters on the microbeam mechanical response.

A Stacked Neural Network Model for Damage Localization.

Traditional vibration-based damage detection methods often involve human intervention in decision-making, therefore being time-consuming and error-prone. In this study, we propose using Artificial Neural Networks (ANNs) to detect patterns in the structural response and create accurate predictions. The features extracted from the response signal are the Relative Frequency Shifts (RFSs) of the first eight weak-axis bending vibration modes, and the predictions refer to the damage location. To increase the accuracy of the predictions, we propose a novel stacked neural network approach, capable of detecting damage locations with high accuracy. The dataset used for training involves, as input data, the RFSs calculated with an original method for numerous damage locations and severities. The following models were used as building blocks for our stacked approach: Multilayer Perceptron, Recurrent Neural Network, Long Short-term Memory, and Gated Recurrent Units. The entire beam was thus split into segments and each network was trained in this stacked model on one beam segment. All results obtained with the models are also compared to a standard neural network trained on the entire beam. The results obtained show that the model that performs the best contains 14 stacked two-layer feedforward networks.

Experimental Study on the Bending Behavior of Precast Concrete Segmental Bridges with Continuous Rebars at Joints

Longitudinal ordinary rebars are discontinuous at the joints of precast concrete segmental bridges (PCSBs), which can open under tensile stresses induced by bending moments. This will lead to durability issues with the joints. To improve the bending properties of PCSBs, a novel joint type featuring continuous rebars was proposed in the present study. Three specimens were subjected to testing to examine the bending behavior of PCSBs using this new joint design compared to traditional joints. The crack propagation, structural deformation, joint opening width, strain in rebars, failure mode, stiffness, and flexural capacity were comprehensively investigated. The test results reveal that the continuous rebars effectively transferred bending normal stress between joints, ensuring full development of cracks in each beam segment. Effective control of joint opening width was also observed. Compared to traditional joints, the new joints exhibited a 29% to 33% increase in cracking load and a 32% increase in ultimate load. Failure in the continuous rebar joints was characterized by partial anchorage failure of the rebars along with localized concrete crushing in the top compression zone. Based on the test results, a computational method was proposed for calculating the cracking strength and flexural capacity of the new joints.

Effect of process parameters on the mechanical performance of fusion-joined additively manufactured segments

PurposeHerein, the authors report the effects of printing parameters, joining method, and annealing conditions on the structural performance of fusion-joined short-beam sections produced by additive manufacturing.Design/methodology/approachThe authors first identified appropriate printing parameters for joining segmented short beams and then used those parameters to print and fusion-join segments with different configurations of stiffeners to form a longer section of a wing or small wind turbine blade structure.FindingsIt was found that the beams with three lateral and three base stiffening ribs give the highest flexural strength among the three beams investigated. Results on joined beams annealed at different conditions showed that annealing at 70 °C for 0.5 h yields higher performance than annealing at the same temperature for longer times. It is also found that in the case of the hot-plate-welded three-dimensional (3D)-printed structures, no annealing is needed for reaching a high strength-to-weight ratio, but annealing is helpful for maximizing the modulus-to-weight ratio. Both thermal buckling and edge wrapping were observed under annealing at 70°C for 0.5 h for 3D-printed beams comprising two lateral and four base stiffening plates.Originality/valueFusion-joining of additively manufactured segments is needed owing to the constraint in building volume of a typical commercial 3D-printer. However, study of the effect of process parameters is needed to quantify their effect on mechanical performance. This investigation has therefore identified key printing parameters and annealing conditions for fusion-joining short segments to form larger structures, from multiple 3D-printed sections, such as wind blade structures.

Compliance analysis of transversely asymmetric flexure hinges for use in a piezoelectric Scott-Russell microgripper

Notch flexure hinges with longitudinal/transverse asymmetries can be widely found in compliant mechanisms to balance the performance trade-offs. However, the transverse asymmetry often leads to difficult analyses of kinetostatics and dynamics. In this paper, a miniaturized piezoelectric gripper featuring reversed Scott-Russell compliant amplifier with transversely asymmetric single-notched flexure hinges is designed for use in confined spaces. The compliance and vibration characteristics of the transversely asymmetric single-notched flexure hinges are quantitatively analyzed by a new transfer matrix method. The proposed theoretical methodology involves discretizing the transversely asymmetric flexure hinge into a series of constant beam segments with non-coaxial nodes, which enables a straightforward modeling process and hence simplifies the kinetostatic and dynamic analyses of compliant mechanisms comprised of complex flexure hinges. Comparative validations with respect to the finite element simulation and experiments confirm the advantages of easy operation and small-scale equation sets of the proposed modeling method. As to the designed piezoelectric microgripper with single-notched flexure hinges, the jaw displacement amplification ratio of 20 and resonance frequency of 1250 Hz has been experimentally tested with a small size of 38 mm × 15 mm × 7 mm.

Derivation and Evaluation of LAI from the ICESat-2 Data over the NEON Sites: The Impact of Segment Size and Beam Type

Derivation and Evaluation of LAI from the ICESat-2 Data over the NEON Sites: The Impact of Segment Size and Beam Type

MR-OCTAVIUS 4D with 1500 MR and 1600 MR arrays is suitable for plan QA in a 1.5 T MRI-linac

To ensure the accuracy of radiation delivery to patients in a 1.5 T MRI-linac, the implementation of quality assurance (QA) devices compatible with MR technology is essential. The OCTAVIUS 4D MR, made by PTW (Freiburg, Germany) is designed to ensure consistent and ideal alignment of its detectors with the direction of each beam segment. This study focuses on investigating the fundamental characteristics of the detector response for the OCTAVIUS Detector (OD) 1500 MR and OCTAVIUS 1600 MR when used in the MR-compatible OCTAVIUS 4D. Characteristics examined included short-term reproducibility, dose linearity, field size dependency, monitor unit (MU) rate dependency, dose-per-pulse dependency, and angular dependency. The evaluation of OD 1500 MR also involved measuring 25 clinical treatment plans across diverse target sizes and anatomical sites, including the liver/pancreas, rectum, prostate, lungs, and lymph nodes. One plan was measured with the standard setup and with a 5 cm left offset. The OD 1600 MR was not available for these measurements. The capability of the OD 1500 MR to identify potential errors was assessed by introducing a MU and positional shift within the software. The results demonstrated no significant differences in short-term reproducibility ( <0.2% ), dose linearity ( <1% ), field size dependency ( <0.7% for field sizes larger than 5 cm × 5 cm), MU rate dependency ( <0.8% ), dose-per-pulse dependency ( <0.4% ) and angular dependency (standard deviation <0.5% ). All tests of clinical plans were successfully completed. The OD 1500 MR demonstrated compatibility with the standard 95% pass rate when employing a global 3%/3 mm gamma criterion, and a 90% pass rate using a global 2%/2 mm gamma criterion. The detector demonstrated the capacity to measure treatment plans with a 5 cm left offset. With the standard parameters, the gamma test was sensitive to position errors but required an addition tests of mean/median dose or point dose in order to detect small dose difference.

Information encoding with a segmented vortex beam

In this paper we propose an information encoding method based on a segmented vortex beam. The segmented vortex beam with a single uniform-intensity ring and a combination of multiple topological charges is designed for information encoding. The radius of the beam can be designed to be arbitrary, with multiple orbital angular momentum states superimposed along the ring. We encoded the information into the segmented vortex beam in the transmitting unit for information transmission. Due to the segmented phase structure of the beam, information can be encoded in each segment, and the information capacity is significantly increased. Additionally, enormous combinations of encoded information in the beam can greatly enhance the security of the encoded information. This proposed method has great potential in free-space optical communication.

Shear behavior of externally prestressed precast concrete segmental beams with both positive and negative moment regions

To investigate the shear behavior of externally prestressed precast concrete segmental beams with both positive and negative moment regions (EPCS P&N beams), eight specimens were subjected to failure under various shear span to depth ratios, moment ratios, and joint types. Throughout the testing process, critical crack initiation and development, joint slippage and opening, failure processes and modes, as well as strains in concrete, stirrups, and external prestressing tendons were meticulously recorded. At the point of failure, the concrete in the shear-compression zone near the top surface of the joint section (closest to the loading point in the positive moment region) or near the bottom surface of the joint section (closest to the interior support in the negative moment region) experienced crushing. Subsequently, the external tendons lost support and underwent elastic retraction, causing the two segments on either side of the critical web-shear crack to slide against each other. The elastic strain energy was released significantly as a consequence of the external tendons retracting, leading to the rupture of stirrups intersecting the failure cracks, followed by flange buckling. Based on the test results, a strut-and-tie model was developed to analyze the shear resistance mechanism, and a detailed flowchart for computing the shear resistance of EPCS P&N beams was established. The predictions from the proposed analytical method were compared with the test results, showing good agreement and confirming the rationality of the proposed shear resistance mechanism.

Transfer matrix modeling for asymmetrically-nonuniform curved beams by beam-discrete strategies

Nonuniform and curved beams can be found in extensive engineering scenarios, ranging from big-scale structures of buildings, bridges to small mechanical systems of aerofoils, blades, micromachines, robotics and sensors. However, variable curvature and transverse asymmetry often lead to a complicated dynamic modeling. In this paper, two beam-discrete strategies are comparatively presented for the free vibration analysis of transversely asymmetric and curved beams and even their combinations. The proposed methodology involves discretizing a general nonuniform and curved beams into a sequence of constant beam segments with non-coaxial nodes or inclination angles, which enables a modular transfer matrix modeling process and hence offers a new way to divide the complex modeling into easier steps. A unified transfer matrix is derived for constant beam elements with non-coaxial nodes and inclination angles accounting for the shear deformation, rotary inertia and axial load in any combinations. The proposed beam-discrete strategies with a unified transfer matrix provide a new perspective in contrast to previous investigations. The advantages of easy programming and small degrees of freedom in the traditional transfer matrix method is extended to transversely asymmetric nonuniform and curved beams. Comparative validation with several engineering beams confirms these advantages.

A low-frequency piezoelectric wave energy harvester based on segmental beam and double magnetic excitation

Wave energy is a source of clean energy with huge reserves, but its application is limited owing to the low frequency of the waves. This paper proposes a low-frequency piezoelectric wave energy harvester (L-PWEH) based on segmental beam and double magnetic excitation. The L-PWEH uses a combination of mechanical and magnetic frequency tuning to achieve an improved output performance in low-frequency wave environments. The natural frequency of the segmental beam is effectively reduced by using the mechanical tuning method of the segmental beam structure. With the introduction of the tuning magnet, a double magnetic excitation of the segmental beam is formed to make it more susceptible to deformation. Multiple magnets on the rotor for excitation can obtain a better broadband effect. Through theoretical and simulation analysis, the primary variables influencing the output performance of the L-PWEH are discovered. Under ideal testing conditions, the L-PWEH can produce a peak power of 31.21 mW when the external resistance is 30 kΩ. The thermohygrometer can function effectively and be illuminated by 142 light-emitting diodes (LEDs) thanks to the L-PWEH. These findings confirm that the L-PWEH can supply low-power electronic devices with electricity.

Mechanical behavior of a novel compact steel-UHPC joint for hybrid girder bridges: Experimental and numerical investigation

Ultra-high-performance concrete (UHPC) has recently been applied as an alternative to normal concrete in steel-concrete composite structures. In this paper, a novel compact steel-concrete joint with UHPC grout, which utilizes shear connectors, a bearing plate and a simple I-shaped steel girder, is proposed for long-span railway hybrid girder bridges. To investigate the mechanical behavior and force transfer characteristics of the proposed compact steel-UHPC joint (CSUJ), a model test with reduced scale and push-out tests of its main force transfer components were conducted. The specimens' failure model, load-interface slip, and strain development were compared and discussed in detail. Furthermore, a finite element model of the CSUJ was established to investigate the internal damage evolution and the load transfer path. The test results indicated that the steel-UHPC joint possessed excellent axial stiffness and cracking resistance. The axial stiffness before cracking is 2.6 times that of the steel-concrete joint prototype with C60 concrete grout. Upon loading, the filled-in UHPC of the CSUJ was in elastic compression. In the ultimate limit state, the steel-UHPC joint exhibited great integrity, and the ultimate failure mode of the CSUJ was controlled by the adjacent axially loaded steel beam segment. Results of push-out tests showed that the force transfer component with perfobond leiste (PBL) connectors demonstrated greater ductility than other transfer components. In terms of the force transfer rate and uniformity, the proposed CSUJ provides desired stress distribution and force transfer behavior. The shear connectors, bearing plate, and end face of the I-girder transferred 49%, 35%, and 16% of the total axial force, respectively.

Research on Lightweight Method of Segment Beam Point Cloud Based on Edge Detection Optimization

In order to reduce the loss of laser point cloud appearance contours by point cloud lightweighting, this paper takes the laser point cloud data of the segment beam of the expressway viaduct as a sample. After comparing the downsampling algorithm from many aspects and angles, the voxel grid method is selected as the basic theory of the research. By combining the characteristics of the normal vector data of the laser point cloud, the top surface point cloud edge data are extracted and the voxel grid method is fused to establish an optimized point cloud lightweighting algorithm. The research in this paper shows that the voxel grid method performs better than the furthest point sampling method and the curvature downsampling method in retaining the top surface data, reducing the calculation time and optimizing the edge contour. Moreover, the average offset of the geometric contour is reduced from 2.235 mm to 0.664 mm by the edge-optimized voxel grid method, which has a higher retention. In summary, the edge-optimized voxel grid method has a better effect than the existing methods in point cloud lightweighting.

Tests and calculation methods for the shear performance of steel shear keyed joint segment beams

Tests and calculation methods for the shear performance of steel shear keyed joint segment beams