Temperature Prediction of Flat Steel Box Girders of Long-Span Bridges Utilizing In Situ Environmental Parameters and Machine Learning

2022 ◽  
Vol 27 (3) ◽  
Author(s):  
Zhi-wei Wang ◽  
Wen-ming Zhang ◽  
Yu-feng Zhang ◽  
Zhao Liu
2018 ◽  
Vol 21 (14) ◽  
pp. 2099-2113 ◽  
Author(s):  
Yang Deng ◽  
Aiqun Li ◽  
Yang Liu ◽  
Suren Chen

The worldwide application of streamlined flat steel box girder on long-span bridges calls for more knowledge of its temperature distribution. The rapid development of structural health monitoring techniques offers a great opportunity to address this issue. A comprehensive approach of installing monitoring equipment, collecting data, and applying long-term temperature monitoring data to study the temperature distribution of flat steel box girders is developed. As demonstrated through the analysis of 1-year data of a suspension bridge, first, a mapping relation between effective temperature and ambient air temperature is established. Such a relation enables identifying the optimal time to finally join the flat steel box girders at the designed effective temperature based on the easy-to-obtain ambient air temperature. Second, the cycling variation of effective temperature is presented to provide information for design and assessment of expansion joints and bearings, including not only the maximum design displacements but also cumulative displacements related to the long-term durability and remaining life of expansion joints and bearings. Finally, both vertical and transverse temperature gradients are studied to provide some new insights about the temperature characteristics of flat steel box girders. The study suggests that the transverse and vertical temperature gradients should be applied to the bridge cross section individually since the data analysis supports that the two gradients are independent.


2015 ◽  
Vol 145 ◽  
pp. 196-208 ◽  
Author(s):  
Yongxin Yang ◽  
Rui Zhou ◽  
Yaojun Ge ◽  
Damith Mohotti ◽  
Priyan Mendis

2021 ◽  
Vol 11 (16) ◽  
pp. 7208
Author(s):  
Felipe de Luca Lopes de Amorim ◽  
Johannes Rick ◽  
Gerrit Lohmann ◽  
Karen Helen Wiltshire

Pelagic chlorophyll-a concentrations are key for evaluation of the environmental status and productivity of marine systems, and data can be provided by in situ measurements, remote sensing and modelling. However, modelling chlorophyll-a is not trivial due to its nonlinear dynamics and complexity. In this study, chlorophyll-a concentrations for the Helgoland Roads time series were modeled using a number of measured water and environmental parameters. We chose three common machine learning algorithms from the literature: the support vector machine regressor, neural networks multi-layer perceptron regressor and random forest regressor. Results showed that the support vector machine regressor slightly outperformed other models. The evaluation with a test dataset and verification with an independent validation dataset for chlorophyll-a concentrations showed a good generalization capacity, evaluated by the root mean squared errors of less than 1 µg L−1. Feature selection and engineering are important and improved the models significantly, as measured in performance, improving the adjusted R2 by a minimum of 48%. We tested SARIMA in comparison and found that the univariate nature of SARIMA does not allow for better results than the machine learning models. Additionally, the computer processing time needed was much higher (prohibitive) for SARIMA.


2019 ◽  
Vol 23 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Junjie Guo ◽  
Haojun Tang ◽  
Yongle Li ◽  
Lianhuo Wu ◽  
Zewen Wang

Wind environment in mountainous areas is very different from that in coastal and plain areas. Strong winds always show large angles of attack, affecting the flutter stability of long-span bridges which is one of the most important design factors. The central vertical stabilizer has been demonstrated to be an effective aerodynamic measure to improve the flutter stability, and this article optimizes the stabilizer to improve its applicability in mountainous areas. Computational fluid dynamics simulations are first performed to analyze the effects of stabilizers with different positions and forms on the flutter stability of an ideal box girder, and the aerodynamic mechanism is discussed based on the static and the dynamic flow fields, respectively. Wind tunnel tests are then carried out to test the critical flutter wind speed of a real box girder equipped with different stabilizers, and the change in its flutter stability is further analyzed. The results show that the vertical stabilizer with appropriate positions and heights can improve the participation level of structural heaving vibration, and thereby increases the flutter stability. At large angles of attack, the big vortex on the leading edge which may drive the bridge to flutter instability is gradually weakened with the increase in stabilizer’s height. Compared with a single stabilizer, double vertical stabilizers, in the midst of which exists a negative pressure region, could achieve better effects.


2020 ◽  
pp. 136943322096902
Author(s):  
Chen Fang ◽  
Ruijie Hu ◽  
Haojun Tang ◽  
Yongle Li ◽  
Zewen Wang

Vortex-induced vibration (VIV) depends on aerodynamic shapes of bridge girders, which should be treated carefully in the design of long-span bridges. This paper studies the VIV performance of a suspension bridge with the truss girder which contains two separated decks. Although truss girders generally show better VIV performance than box girders, significant vibrations of this type of girders occurred in the wind tunnel tests based on a large-scale sectional model. Several lock-in regions with the same vibration frequency were observed, corresponding to different shedding vortices. Computational fluid dynamics (CFD) simulations were carried out, and monitoring points were set behind different components to study the characteristics of the shed vortices. As the truss girder consists of many members, the results show that various vortices with different dominant frequencies are formed in the wake flow. The vertical VIV of the bridge is probably driven by the vortices behind or above the upper deck, which is related to the guardrails. The torsional VIV of the bridge is probably driven by the vortices behind or below the lower deck, which is related to the service road at lower wind speeds while may be related the vertical stabilizers at higher wind speeds.


2020 ◽  
pp. 136943322095682
Author(s):  
Junjie Guo ◽  
Haojun Tang ◽  
Yongle Li ◽  
Zewen Wang

Normally strong winds in mountainous areas possess potential threats to the safety of vehicles travelling over the long-span bridges. Generally, decreasing the porosity of the guardrails could improve wind environment for vehicles, while the changed flow field around the bridge’s girder may weaken the structural aerodynamic stability simultaneously. To solve the two seemingly contradictory issues, such a long-span suspension bridge in mountainous areas is taken as the case study, and the guardrails are optimized with different schemes. The effects on wind environment for vehicles under normal traffic conditions are first studied by computational fluid dynamics (CFD) simulations. The further effects on the aerodynamic stability of the bridge under extreme winds are then determined by wind tunnel tests, and the observed non-divergent flutter is explainedbythe change in dynamic flow field. Results show that reducing the porosity of guardrails does improve the wind environment above the bridge deck, and the improvement on wind environment increases with the increase in angle of attack. After closing the guardrails completely, however, the girder appears non-divergent vibration different from the linear theoretical flutter when the critical wind speed is exceeded. The different post-flutter behaviors at different angles of attack are mainly related to the synchronization condition between the movement of vortex and the motion of the girder.


PCI Journal ◽  
1980 ◽  
Vol 25 (4) ◽  
pp. 48-58
Author(s):  
Felix Kulka
Keyword(s):  

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