Restoration of missing structural health monitoring data using spatiotemporal graph attention networks

For structural health monitoring systems with many low-cost sensors, missing data caused by sensor faults, power supply interruptions and data transmission errors are almost inevitable, significantly affecting structural diagnosis and evaluation. Considering the inherent spatial and temporal correlations in the sensor network, this study proposes a spatiotemporal graph attention network for restoration of missing data. The proposed model was stacked with a graph convolutional layer and several spatiotemporal blocks composed of spatial and temporal layers. The monitoring data of normal sensors were first mapped to all sensors through the graph convolutional layer, and attention mechanisms were used in the spatiotemporal blocks to model the spatial dependencies of sensors and the temporal dependencies of time steps, respectively. The extracted spatiotemporal features were assembled through a fully connected layer to reconstruct the missing signals. In this study, both homogeneous and heterogeneous monitoring items were used to calculate the spatial attention coefficients. The data restoration accuracy with and without the multi-source data fusion was discussed. Application on a long-span cable-stayed bridge to restore missing cable forces demonstrates that spatiotemporal attention modelling can achieve satisfactory restoring accuracy without any prior analysis.

Temporary Cable Force Monitoring Techniques During Bridge Construction-phase. The Tajo River Viaduct Experience

This article addresses the comparative analysis of current techniques for monitoring cable forces. Additionally, the experience of three cable force different monitoring techniques for strain control in bridge cables during the construction phase is included: a) installing load cells on the active anchorages of the cables, b) installing unidirectional strain gauges, and c) assessing the stress on cables by applying the vibrating wire technique through the installation of accelerometers. The main advantages and disadvantages of each technique analyzed are highlighted in the construction process context of the Tajo Viaduct, one of the most singular viaducts recently built in Spain.

Analysis and Design of Cable Stayed and Suspension Bridge Subjected to Wind Loading

Bridge can be defined as a structure which is built to pass a physical obstacle such as river road or valley and this structure does not close the way underneath it. The main objective of the bridgeis to provide a passage which can surpass any obstacle. A bridge is designed according to various specific purposes depending upon the need function and various physical factors. Cable-stayed bridge is having one or more columns called towers or pylons, with the cables directly supporting the bridge deck. Cable-stayed bridge is the bridge form in which the weight of the deck is supported by a number of nearly straight diagonal cables in tension running directly to one or more vertical towers. The towers transfer the cable forces to the foundations through vertical compression. The tensile forces in the cables also put the deck into horizontal compression. A suspension bridge is able to carry vertical loads with the help of curved cables in tension. Transfer of load takes place to both the towers, which is transferred by vertical compression to the ground, and anchorages, which is able to withstand the inward and occasionally vertical pull of the cables. The suspension bridge is often looked as an upside-down arch in tension with only the towers as compression members. In this research work, analysis and design of cable stayed and suspension bridge subjected to wind loading has been carried out.

Research on Non-Contact and Non-Fixed Cable Force Measurement Based on Smartphone

Stay cable is the major load-carrying element in cable-stayed bridges. The process of monitoring cable forces would be beneficial to ensure the safety of bridges. The conventional sensor-based approaches to measure stay cable forces is complicated in operation, time-consuming and relatively expensive. In order to confront these disadvantages, a lightweight measurement method using smartphone imagery was proposed in this paper. The video data acquisition process was first standardized by using a pre-designed target. Then, a novel algorithm to extract the vibration displacement of stay cables under complex condition was developed. An automatic correction algorithm was provided to further improve the displacement results. On top of that, a smartphone-based software for determining cable forces was developed and tested on a real-life bridge. The results showed a maximum error of 1.99% compared with the cable force obtained by using a dynamic tester. The developed software is proven to be feasible in real-life projects and can achieve high accuracy in cable force determination. At the same time, the proposed method does not require a fixed camera for measurement and is not limited by personnel experience and measurement time, facilitating real-time monitoring of multiple projects, multiple cable surfaces and multiple personnel in a visual vibration environment.

Nonlinear Analysis of Cable Net Structures

Objective: To present a methodology for implementing in MathCAD, a based on force densities for analytical form finding to three-dimensional cable net structures subjected to static loading. It is desired that the routines present a stability of the solution algorithm and fast convergence. Methodology: Theoretical background of the cable net structures behavior and FDM are first introduced. Then, a series of MathCAD routines are created to perform the nonlinear analysis of cable net structures. Finally, a well-documented cable net structure example found in the literature, and the results from a cable net software are used as a way to validate the output results provided by the created MathCAD routines. Results: The simulation results show that the proposed methodology implemented in MathCAD can accurately estimate the free nodes displacements and cable forces of 3D cable net structures subjected to vertical and horizontal static loading. Conclusions: This paper has demostrated that the propossed methodology is consistent when comparing with the results given in the reference paper and the used software. Stability of the algorithms is controlled and no numerical issues was presented during the analyzed examples thus, divergence complications were not found. The routines provided a clear way to visualize the assumptions, methods, and critical data obtained in the geometric analysis of cable net structures helping to overcome the inherit limitations of commercial packages.

A practical compensation algorithm of stress relaxation due to single tension

PurposeDue to the deformation between the pylon and the girder caused by single tension of cables, the previously tensioned steel strands have stress relaxation, resulting in the actual cable forces being less than the design cable forces. To compensate the stress loss caused by the single tension of cables, this paper aims to present a practical compensation algorithm of stress relaxation during the construction period.Design/methodology/approachFrom the perspective of the essential cause of the stress relaxation, finite element analysis is used to solve the tension control force of each steel strand after a rigorous theoretical formula derivation.FindingsThe deformation and tension control force of each steel strand decrease with the advance of the tension sequence, and the decline rate drops gradually. However, the calculated force values of the steel strand are in good agreement with the measured value as the cable length decreases.Originality/valueThe previous rough calculation methods for the tension force of steel strands cannot meet the accuracy, and the accurate calculation methods often include the solution of nonlinear equations, which complicate the calculating process. Otherwise, there are few studies on the compensation of stress loss by calculating the deformation of the steel strand during the tension process. So, it developed an accurate and efficient algorithm to determine the tension control forces.

Estimation of Extreme Cable Forces of Cable-Stayed Bridges Based on Monitoring Data and Random Vehicle Models

For long-span cable-stayed bridges, cables serve as one of the most important components to guarantee structural integrity. Forces of stay cables indicate not only the performance of cables themselves but also the overall condition of bridges. In order to help stakeholders to make maintenance decisions, an extreme cable force estimation method was proposed based on cable force measurements and traffic data from the weighing system. First, raw monitoring data were preprocessed based on a median filtering to obtain usable cable force signals. The multiresolution wavelet method was used to extract traffic-induced force component from mixed signals. Then, a Monte Carlo-based random vehicle model was developed using traffic data from the weighing system. Based on field temperature measurements and simulation of traffic-induced effects, extreme cable forces with respect to vehicle loads and temperature effects were predicted by extreme value theory. The Generalized Pareto Distribution (GPD) was adopted to establish the probability distribution models of the daily maximum cable force. Then, the extreme value within a return period of 100 years was determined and compared with the design loading demand. Finally, the effectiveness of the proposed method was validated through a cable-stayed bridge in China. As a result, the low-frequency varying component of cable force response had positive correlation with environmental temperatures, and the extreme value of the predicted cable force under prospective traffic volumes was within limit interval value according to the design code. The conclusions can be utilized by bridge owners to make maintenance decisions.

Lumped, Constrained Cable Modeling With Explicit State-Space Formulation Using An Elastic Version of Baumgarte Stabilization

This paper presents a modeling approach for efficient simulation of slender structures, such as wires, cables and ropes. Lumped structural elements are connected using constraints. These are solved explicitly, using an elastic version of Baumgarte stabilization. This avoids singularities in the matrix inversions. The resulting explicit state-space formulation filters the higher order dynamics and can be solved using simple numerical integration methods. Constraints are demonstrated for modeling different aspects: Internal cable forces, one cable sliding along another cable and contact between cable and seabed. Also, a cable initialization routine is presented for rapid building of different interconnected cable geometries, ranging from cases in offshore crane operations to in-sea equipment such as seismic cables. Two case studies are presented to illustrate the effectiveness and the robustness of the proposed modeling approach; the first one being a test of two connected, sinking cables, and the last one being a larger case demonstrating the use of the cable library in an offshore seismic survey case.

Novelty detection of cable-stayed bridges based on cable force correlation exploration using spatiotemporal graph convolutional networks

The novelty detection of bridges using monitoring data is an effective technique for diagnosing structural changes and possible damages, providing a critical basis for assessing the structural states of bridges. As cable forces describe the state of cable-stayed bridges, a novelty detection method was developed in this study using spatiotemporal graph convolutional networks by analysing spatiotemporal correlations among cable forces determined from different cable dynamometers. The spatial dependency of the sensor network was represented as a directed graph with cable dynamometers as vertices, and a graph convolutional network with learnable adjacency matrices was used to capture the spatial dependency of the locally connected vertices. A one-dimensional convolutional neural network was operated along the time axis to capture the temporal dependency. Sensor faults and structural variations could be distinguished based on the local or global anomalies of the spatiotemporal model parameters. Faulty sensors were detected and isolated using weighted adjacency matrices along with diagnostic indicators of the model residuals. After eliminating the effect of the sensor fault, the underlying variations in the state of the cable-stayed bridge could be determined based on the changing data patterns of the spatiotemporal model. The application of the proposed method to a long-span cable-stayed bridge demonstrates its effectiveness in sensor fault localization and structural variation detection.