Preliminary Design Stage Research Articles

Film cooling effectiveness from upstream purge slots of a turbine vane endwall: Experiment, modeling, and correlation

The design of an efficient cavity slot between assembled components, where purge air is injected, is especially crucial to the durability and efficiency of an aero-engine, since the purge air is relevant to sealing and film cooling of the hot component. In this paper, film cooling for purge flow injected from slots upstream the endwall of a turbine vane is systematically investigated in a linear cascade using Pressure-Sensitive Paint (PSP). The influence of the slot width (0.020−0.044 times vane axial chord length), position (0.11−0.24 times vane axial chord length in front of turbine passage inlets), and inclination angle (20−45°) is examined for coolant injection ratios of 0.3−2.0 %, with an attempt to develop a new correlation specifically for purge flow film cooling over a turbine endwall, since existing correlations in literature only work for slot injection on flat plates. The experimental tests are undertaken in extensive ranges of the slot geometry and the injection rate that are typically seen in a modern engine. For better understanding the impacts of the affecting parameters, five-hole probe and thermocouple measurements and numerical simulations were carried out as well to visualize the coolant-with-mainstream mixing flows. The measured local film coverage, pitchwise- and area-averaged cooling effectiveness are presented and discussed, in combination with the probe-detected and numerically-modeled flow structures to elaborate the experimental observations. The current results sufficiently reveal the changing tendency of purge flow film cooling caused by the variations of the slot geometry. Additionally, the newly-developed correlation is well validated using own experimental data and datasets in literature, proving the capability of the correlation to predict film cooling for purge flow injected from slots with such geometrical parameter ranges. The correlation can be a helpful tool to support the selection of an efficient slot in its preliminary design stage.

Parametric design of a residential building system through solar energy potential: the case of Guelma, Algeria

To evaluate the potential of retrofitting roofs of residential buildings in Algeria with building integrated photovoltaics (BIPV). A case study of a family residential building in the city of Guelma, was selected to receive building-integrated photovoltaic (BIPV) systems as a retrofit to their roofs using Rhinoceros software and plugins Grasshopper, Ladybug, and Honeybee, adding photovoltaic panels on the roof taking into account the study of solar radiation analysis on the building, and meteorological data from Meteonorm Software 7.3. The method used, is based on measured data for final energy consumption (yearly average of 14600 kWh), building morphology, and photovoltaic module parameters. The results of the renovation of roofs with building-integrated photovoltaic solutions are presented for the existing residential building, it is also shown that a small photovoltaic area on the roofs can meet the demand of the buildings. The results identify the aspects that need to be improved in the development of future design tools and highlight the importance of integrating parametric design software and simulation tools for BIPV systems at the preliminary design stage, to ensure good building performance, both in terms of comfort and energy performance.

Fast time-domain model for the preliminary design of a wave power farm

This study presents a novel, fast time-domain model developed for an array of interacting point-absorber wave energy converters. The model is validated using experimental wave tank data. The point-absorbers, based on Uppsala University’s design, are arranged in a symmetric grid and interact with scattered and radiated waves while constrained to the heave motion. The model employs linear potential flow theory to solve the hydrodynamic coefficients in the frequency domain and employs Cummins’ formulation to solve the equations of motion in the time domain. Modeling an array of wave energy converters in the time domain yields a system of integro-differential equations, featuring convolution terms in the excitation and radiation forces. This implies that past waves radiated by the body continue to impact future dynamics. Irregular long-crested waves, generated from the Bretschneider spectrum, serve as the incident waves for the study. The model’s accuracy in capturing the dynamics and power absorption of the farm is demonstrated through validation against experimental data from a 1:10 scaled prototype of a six-point-absorber array. Despite inherent differences between the experimental and numerical set-ups, the model accurately represents the farm’s behavior. Furthermore, an efficiency test reveals that the numerical scheme approximates the performance of wave power farms comprising 6, 12, 24, 48, and 96 interacting devices within a maximum computational time of 20 s. Overall, this research presents a novel and accurate time-domain model for analyzing an array of point-absorber wave energy converters. The model’s ability to capture the dynamics and power absorption, along with its efficiency in simulating larger wave power farms, make it a valuable tool for the preliminary design stage.

RELIABILITY OF HYDROPNEUMODRIVES FOR METAL CUTTING EQUIPMENT

The reliability of hydropneumodrives largely determines the safety of machine tools, metal cutting equipment, the movement of transport vehicles, and the flight of modern passenger aircraft, and their failures can in some cases lead to accidents. The design stage is crucial in ensuring reliability. The main tasks of reliability research and calculation at this stage can be divided into three groups. First, it is a justification of reliability requirements for the main elements of the hydraulic pneumatic actuator (the task of reliability norming). This task is solved at an early stage of design and involves the preliminary development of the unit structure and justification of design principles. Secondly, it is to ensure the reliability of the elements and the unit as a whole. This group of tasks includes research and quantitative assessment of the efficiency of possible ways to ensure reliability; selection of basic design characteristics, statistical reserves of durability and longevity, stability reserves and other indicators; comparative analysis of options and selection of optimal designs. Thirdly, these are control calculations of the unit's reliability according to the design documentation. Algorithms for the distribution of normalised reliability indices at the design stage for hydropneumodrives implemented by the standard positional structure method and the minimisation method are obtained. Algorithms allow already at the early stages of hydropneumodrive design to normalise reliability indices, which makes it possible to obtain optimal solutions of reliability issues at the subsequent stages of development of the drive life cycle. The methods of calculation and determination of design relations for finding quantitative characteristics of failure-free indices of designed hydropneumodrives, implemented by the method of standard positional structure and the method of minimisation, are selected, which allows designing highly reliable hydropneumodrives for new metal cutting equipment. Evaluation of reliability indicators of hydropneumodrives at the stage of preliminary design allows to make a rational choice of structural scheme and parameters, to select appropriate materials and elements of scheme realisations.

Investigation of neutronic and thermal–electric coupling phenomenon in a 100 kWe-level nuclear silent heat pipe-cooled reactor

Heat pipe-cooled reactors are attractive because of their compact structure, high power capacity and reliability, and inherent safety features. These reactors are distinguished by the use of high-temperature heat pipes that directly bridge the reactor core and energy conversion devices, thus creating a tightly knit modular system. However, comprehensive coupled analysis of these reactors remains challenging because of the intricate multiphysics interactions involved. To address this, the neutronic and thermoelectric coupled phenomena of heat pipe-cooled reactors are investigated in this study. Models are introduced for the point reactor kinetics, core heat transfer, channel heat transfer, two-phase two-dimensional heat pipes, thermoelectric coupling, and cold plates. The channel heat transfer is refined in a 100 kWe-level nuclear silent heat pipe-cooled reactor and a model for the three-dimensional heat transfer process in its thermoelectric matrix established, which effectively resolves the calculation distortions of the lumped model. The maximum deviation between the calculation results from the proposed model and the verification data for a full-system coupled computation is less than 10 K. The core temperature difference from the three-dimensional model is five times that of the lumped model with a maximum average fuel temperature difference of 225.7 K. The maximum and average thermoelectric conversion efficiencies are 15.56 % and 14.43 %, respectively. The failures of one, five, and nine heat pipes are analysed. The failure of a single heat pipe has negligible effects with a peak fuel temperature surge of only 121 K. In contrast, a failure involving nine heat pipes leads to a peak fuel temperature spike of 778 K and a 47.1 % increase in the maximum heat transfer power, marking a critical operational threshold. It is therefore imperative to consider the safety margin in the potential failure of multiple central heat pipes during the preliminary design stages.

CDTC: Automatically establishing the trace links between class diagrams in design phase and source code

AbstractContextThe UML class diagram is commonly used to model functional structures and software code structures in both the preliminary and detailed design stages. And the abstraction level of UML class diagrams is usually higher than that of source code. Usually, there is a lack of trace links between these class diagrams and the source code, which may cause difficulties in understanding the source code, and affect the software evolution and maintenance.ObjectiveThe main goal of this article is to establish the trace links between highly abstracted UML class diagrams in the design phase and source code, and eventually help practitioners better understand source code.MethodWe propose an approach for the automated trace link establishment between UML class diagrams in the design phase and source code. To address the problem of abstraction level gap between them, we extend the UML class diagram by mining the synonymous phrases of class names and deducing the latent missing relationships between classes from multiple design documents. Then we build the trace links with a two‐phase approach including initial construction with fuzzy matching and further optimization by class relationship inference.ResultsExperiments on five open‐source projects show that the recalls of our approach are over 94%, and the F2‐scores are over 88%, with the gains of 30% to 60% than the four baselines.ConclusionOur work can be a reference for establishing the initial trace links between highly‐abstracted UML class diagrams and source code. Towards the higher abstraction of design diagrams, we extend UML class diagrams with the statistical analysis on multiple design documents. To guarantee the quality of trace links, we design a two‐phase approach by obtaining the “full but not good enough” trace links and filtering the “probably wrong” links. Experiments show that the main techniques of our approach behave as important role for tracing between high‐level class diagrams and source code.

A data-driven flow loss prediction model for the blade hub region of a boundary layer ingestion fan rotor

PurposeIn a boundary layer ingestion (BLI) propulsion system, the fan operates continuously under distorted inflow conditions, leading to an increment of aerodynamic loss and in turn impacting the potential fuel burn reduction of the aircraft. Usually, in the preliminary design stage of a BLI propulsion system, it is essential to assess the impact of fuselage boundary layer fluids on fan aerodynamic performances under various flight conditions. However, the hub region flow loss is one of the major loss sources in a fan and would greatly influence the fan performances. Moreover, the inflow distortion also results in a complex and highly nonlinear mapping relation between loss and local physical parameters. It will diminish the prediction accuracy of the commonly used low-fidelity computational approaches which often incorporate traditional physics-based loss models, reducing the reliability of these approaches in evaluating fan performances. Meanwhile, the high-fidelity full-annulus unsteady Reynolds-averaged Navier–Stokes (URANS) approach, even though it can give rather accurate loss predictions, is extremely time-consuming. This study aims to develop a fast and accurate hub loss prediction method for a BLI fan under distorted inflow conditions.Design/methodology/approachThis paper develops a data-driven hub loss prediction method for a BLI fan under distorted inflows. To improve the prediction accuracy and applicability, physical understandings of hub flow features are integrated into the modeling process. Then, the key physical parameters related to flow loss are screened by conducting a sensitivity analysis of influencing parameters. Next, a quasi-steady assumption of flow is made to generate a training sample database, reducing the computational time by acquiring one single sample from the highly time-consuming full-annulus URANS approach to a cost-efficient single-blade-passage approach. Finally, a radial basis function neural network is used to establish a surrogate model that correlates the input parameters and the output loss.FindingsThe data-driven hub loss model shows higher prediction accuracy than the traditional physics-based loss models. It can accurately capture the circumferentially and radially nonuniform variation trends of the losses and the associated absolute magnitudes in a BLI fan under different blade load, inlet distortion intensity and rotating speed conditions. Compared with the high-fidelity full-annulus URANS results, the averaged relative prediction errors of the data-driven hub loss model are kept less than 10%.Originality/valueThe originality of this paper lies in developing a new method for predicting flow loss in a BLI fan rotor blade hub region. This method offers higher prediction accuracy than the traditional loss models and lower computational time cost than the full-annulus URANS approach, which could realize fast evaluations of fan aerodynamic performances and provide technical support for designing high-performance BLI fans.

Shaping bridge decks for VIV mitigation: A wind tunnel data-driven adaptive surrogate-based optimization method

Vortex-induced vibration (VIV) of deck girders frequently drives the wind-resistant design of wind-sensitive bridges from the preliminary to final design stages. Shaping bridge decks is a proven strategy to mitigate VIV. While significant shape modifications are commonly restricted to preliminary design stages, only minor medications are possible at advanced design stages, typically involving adding flow modifiers or changing the shape and location of existing appendages. These mitigation strategies have been implemented in the last decades by carrying out expensive wind tunnel campaigns and following heuristic design rules. This paper proposes an experimental data-driven adaptive surrogate-based optimization approach to systematically identify optimum deck shapes that minimizes the economic cost of the bridge while fulfilling the VIV project specifications. The methodology is conceived to carry out simultaneously the general and detailed shape design of the final deck configuration by harnessing a sequential sampling plan aiming at reducing the sectional model construction costs. The proposed holistic design framework is successfully applied to a real application case involving 26 wind tunnel tests of 1.8-meter wide sectional models to figure out the optimal gap distance and location of maintenance tracks of a twin-box deck equipped with all the appendages included in the final deck design.

The Upper bound limit analysis of slope in cohesive-frictional soils using the node-based smoothed finite element method

This paper presents the upper bound limit analysis of slope in cohesive-frictional soils using the node-based smoothed finite element method (NS-FEM). The soil slope was discretized as triangular elements and modeled as Mohr-Coulomb material with the associated flow rule. This paper investigated the variation of slope stability numbers Ns with the change of the slope inclination angle a and b, and internal friction angle f. In this study, several numerical examples of slopes have been investigated, showing that the NS-FEM approach can demonstrate accuracy and efficiency solutions. Finally, the stability results are presented in design tables and charts for engineers to use in the preliminary design stage of the slope stability analysis.

Seismic mitigation performance evaluation of linked buildings with a vibration-suppression layer

Linked buildings (LBs) have been widely used in urban areas because of their aesthetic quality and versatility. As LBs are vulnerable to damage under earthquake excitation, undesired vibrations should be suppressed. The use of weak connections is an effective approach to improve the seismic performance of LBs; however, they are inapplicable to LBs with inherently strong connections. In this study, a novel control system—a LB with a vibration-suppression layer (LBVSL)—is proposed to reduce the seismic responses of the LBs with strong connections. The LBVSL system is implemented by introducing a vibration-suppression system into one of the buildings. To extensively investigate the seismic mitigation performance of the LBVSL, a parametric study is conducted to evaluate the trends of its mean vibration energy with the control and structural parameters based on a simplified calculation model. The control parameters include the equivalent stiffness and damping of the vibration-suppression system, and the structural parameters include the stiffness and mass of the LBs. To understand the damping effect of the LBVSL, several numerical examples are studied. The analytical results suggest that the LBVSL has substantially reduced vibration energy and responses compared to the plain LBs. For instance, the LBVSL with the optimal parameters achieves a vibration energy reduction of 69% and a stochastic seismic response decrease of 30–50% relative to those of plain LBs. Additionally, the LBVSL achieves better damping performance and robustness when the vibration-suppression layer is placed on a lower floor. Furthermore, the simplified model provides an alternative for effectively optimizing critical parameters in the preliminary design stage.

DESAIN MEJA BELAJAR ANAK BERGAYA TETRIS

Early childhood age is in a stage of growth and development both physically and mentally. In their activities at school, children who study at the kindergarten level need learning facilities, one of which is study tables and chairs. Sometimes these facilities do not meet the condition of the student's body, dealing with its terms of size, shape and parts. The impact of the mismatch between the school fascilities such asa tables and chairs with the body size of school children is one of the obstacles in the efforts of improving learning outcomes.
 Tetris is one of the most favorite games that prioritizes competition among players, but still the players have to follows the rules of the game. This toy is quite interesting and popular among young children. Based on this background, efforts are made to solve the problem, one of which is by making tables and chairs for kindergarten children with the concept of the Tetris game.
 In designing products so that are well directed, the Vinod Goel method is used with the stages of Preliminary Design, Design Development, and Final Design and Prototype.
 The results of this design are intended for children aged 5 - 6 years, with components of chairs, tables, Tetris cubes and Tetris puzzles, with configurations according to ergonomics and anthropometry. The connection system uses a butt joint with nail reinforcement and glue adhesive. The material used is multiplex, with a shape of a tetris concept, a retro fifties and colorful design style with rainbow colors

Development and validation of the genitourinary syndrome of menopause symptoms and vaginal treatments acceptability questionnaire (GSM-SVTAQ): An electronic patient-reported outcomes measure.

To develop and validate an electronic, patient-reported outcomes measure (PROM) specific for genitourinary syndrome of menopause (GSM) patients. The PROM aimed to accurately assess the burden of GSM symptoms, their impact on health-related and sexual quality of life, and the acceptability of vaginal treatments. The study encompassed a comprehensive three-stage approach to the development and validation of the PROM. Initially, during the preliminary design stage, the necessity for a new PROM was recognized, an expert panel was formed, and semi-structured qualitative interviews were carried out with GSM patients. In the second stage, the study used the five-step pre-validation methodology established by Prior et al. to generate and refine the PROM items. The third and final stage encompassed the determination of scale and item content validity indexes to ensure validity. Additionally, the reliability of each construct was evaluated using Cronbach's α. The resulting PROM was named GSM-SVTAQ (GSM-symptoms and vaginal treatments acceptability questionnaire). It demonstrated excellent validity in assessing symptoms burden, health-related and sexual quality of life, and vaginal treatment acceptability, with high content validity indices and strong internal consistency. The scale content validity indices and Cronbach's α coefficients for the three domains were (0.926, 0.939), (0.875, 0.947), and (0.824, 0.855), respectively. The GSM-SVTAQ stands as the first GSM-specific, valid, and reliable PROM capable of comprehensively measuring the three components of GSM and the acceptability of vaginal treatments. Its implementation has the potential to significantly enhance patient care and outcomes in GSM management.

Coupled free vibration analysis of rotating non-uniform cantilever beams by an element-wise Ritz method using local hierarchical functions

The coupled free vibration behaviour of rotating non-uniform cantilever beams is investigated by an efficient and accurate element-wise Ritz method using Bardell’s polynomials as local hierarchical functions. Both bending-twisting and bending-extension coupling is included in the beam model. The same hierarchical set can be suitably modified to satisfy the essential boundary conditions and represent the stretching, bending and rotation of the beam. The global matrices are obtained by minimizing the Lagrangian functional. The inter-element compatibility conditions are satisfied, and a condensation procedure is used to obtain the condensed matrices for the eigenvalue problem. The procedure is validated with examples from published studies and various case studies are presented to demonstrate the accuracy and convergence of the proposed method. A parametric study is presented to show the effect of various parameters on the free vibration response of rotating non-uniform beams. The frequency veering phenomenon is observed during the study. The proposed approach provides a simple and efficient approach for analyzing the free vibrations of rotating structures such as wind turbine rotor blades, helicopter blades, propellers, and structures with strong discontinuities, especially in the preliminary design stage.

Methodology for Preliminary Flight Control Actuator Design

In this paper, a methodology for the preliminary design of decentralized civil-use flight control actuators is presented that is able to perform the calculations with a very small amount of input data. This enables the user to achieve good actuator key characteristics regarding the weight, power, and volume in the preliminary aircraft design stage without the need for an empirical database. Optionally adjustable setting parameters of the individual components allow the component design to be customized in detail. Both electromechanical and electrohydrostatic actuators are considered. The methodology presented here aims at sizing each individual component of the actuators in terms of volume, mass, and power consumption. The components are broken down into simple geometric shapes where possible. The methodology is evaluated on several actuators of different performance and weight classes from 3.2 kg up to 66.9 kg and provides more accurate results than other common approaches, which is suitable in the preliminary aircraft design stage.

Stable node-based smoothed finite element method for seismic stability analysis of a square tunnel in cohesive-frictional soils

This paper presents a stable node-based smoothed finite element method (SNS-FEM) based on the upper theorem for stability analysis of a square tunnel in cohesive-frictional soils subjected to seismic forces and surcharge loading. The soil behavior is considered homogeneous Mohr-Coulomb with cohesion c, friction angle ϕ and unit weight γ. Using the pseudo-static approach, the horizontal kh and vertical earthquake acceleration coefficients kv are applied to the entire soil mass. Then, the square tunnel is subjected to horizontal and vertical surcharge loadings on the ground surface. The variations of the seismic stability numbers with the change coefficients kh have been investigated for different values of the cover depth-to-width ratio of the tunnel H/B, soil properties γB/c, and internal friction angle ϕ. Several numerical results of square tunnels have been investigated, showing that the SNS-FEM approach can demonstrate accuracy and efficient solutions. The seismic stability numbers results are presented in design tables and charts for engineers to use in the preliminary design stage of the square tunnel. Finally, the article investigates the effect of horizontal and vertical seismic acceleration components on the corrective coefficients of a square tunnel.

PREDICTION OF SLOPES SAFETY FACTOR USING ANN AND TREE-BASED MODELS

Slope stability assessment is a non-linear engineering problem. The complex relationship between factors that affect slope instability is challenging to investigate theoretically and mathematically. This paper proposes the prediction of slopes safety factor, subjected to circular failure mode using artificial neural network (ANN) and two tree-based models using M5P and random forest (RF) algorithm. A dataset including 46 slope cases was divided into a 70/30 ratio to train and validate the model. The input parameters for slope stability evaluation include slope angle, slope height, cohesion, internal friction angle, unit weight and pore pressure ratio. The corresponding output parameter is a factor of safety (FS). The finest ANN structure was obtained as 6-7-1 using the trial-and-error method. The proposed model chooses elliot as the best activation function at a learning rate and momentum of 0.7 and 0.5 for the accurate estimation of FS. In validation phase of ANN, M5P and RF models, the coefficient of determination (R2) results as 0.94, 0.86 and 0.81, respectively. The result suggests that the developed ANN model provides higher accuracy than tree-based models which can be an effective tool for slope stability assessment. Furthermore, the significance of input variables for FS prediction has been investigated through sensitivity analysis, which identifies the complex relationship between the input and output variables. The accuracy achieved from the prediction model is crucial for preventing the risk of slope failure and increasing the slope safety during preliminary design stage.

Third-order aberration analysis of a Fresnel lens

This paper presents expressions for the third-order aberrations of a Fresnel surface (Seidel coefficients). The formulas are derived in a form that allows analytical aberration analysis to be performed at the stage of layout and preliminary design of a system composed of both classical and Fresnel surfaces. In addition to the five major monochromatic Seidel aberrations of the classical surfaces and the line coma which was described for the Fresnel-type surfaces, another aberration, called quadratic astigmatism, is described in this paper. Although the obtained expressions are an approximation for the third-order aberration domain, i.e. higher-order aberrations are ignored, they provide sufficient accuracy in practice, which is also shown in the paper. The derived expressions can be applied to the analysis of aberrations in schemes using a Fresnel lens, which makes it possible to identify the areas of rational use of elements of this type.

Preliminary stability design method and hybrid experimental validation of a floating platform for 10 MW wind turbine

Platform motions induced by wind and waves import strong nonlinear coupling effects in the aerodynamic characteristics of floating offshore wind turbines (FOWTs), which exacerbate the power instability of the wind turbine and should be considered during the preliminary platform design stage. For this reason, a platform motion-based method was proposed to estimate the power stability and successfully applied to the preliminary platform stability design in this paper. Firstly, a high-fidelity computational fluid dynamics (CFD) model of a 10 MW wind turbine was established using the oversetting grid and superposition motion technology. Then the influence laws of platform surge and pitch motions on the power characteristics of the wind turbine were summarized. Subsequently, a semi-submersible floating platform structure for supporting the 10 MW wind turbine was designed preliminarily. The power stability of the wind turbine and tilting stability of the platform were analyzed based on the hydrodynamic analysis results. Finally, a hybrid scaled model of the 10 MW FOWT was built, incorporating a six-degrees of freedom load actuation system based on multi-fans. The scaled model test was carried out in a wave basin, demonstrating that both the power stability and the tilting stability of the platform meet the proposed stability requirements.

A simplified ANN-based evaluation method for creep sensitive girder bridge identification at preliminary design stage

Excessive deflection which exceeded expectations has been identified as one of the main problems contributing to long-term performance degradation of long-span girder bridges. Although the 3D refined finite element model of the full bridge can improve the prediction accuracy of long-term creep deformation, there is still a lack of efficient creep-sensitive structural judgment methods in the preliminary design stage. This study was thus intended to develop a new evaluation method and model to identify the possibility of excessive deflection will occur by utilizing simple structural design parameters, which contributed to new understandings of the creep deformation of bridge structural level. A finite element model database established by 20 long-span prestressed concrete girder bridges with actual project backgrounds was used for providing training, testing, and validation sample datasets for the artificial neural networks (ANN). The Back Propagation (BP) model was chosen for creating mappings among variables and results and solving complex problems with a fairly accurate prediction even without sufficient information. The indicator of deflection-span ratio difference between creep models was proposed as the key analysis factor. A case study was conducted to validate the effectiveness of the ANN model. The mean absolute error (MAE) between the results of the ANN model and FE analysis was 6.25%, which indicated a high consistency. The analysis of bridge design parameters using the ANN model revealed that it had a high risk of excessive deformation, which was consistent with the conclusion of the actual situation. Multiparameter sensitivity analysis results from the model also suggest that the side-span ratio, the main span, and the deflection caused by the pavement are the most three significant impacts compared to different input variables in this model. Based on the results, it can be concluded that the performance of the ANN-based technique can predict possible excessive creep problems in advance.

Intelligent Identification and Verification of Flutter Derivatives and Critical Velocity of Closed-Box Girders Using Gradient Boosting Decision Tree

Flutter derivatives (FDs) of the bridge deck are basic aerodynamic parameters by which flutter analysis determines critical flutter velocity (CFV), and they are traditionally identified by sectional model wind tunnel tests or computational fluid dynamics (CFD) numerical simulation. Based on some wind tunnel testing results and numerical simulation data, the machine learning models for identifying FDs of closed-box girders are trained and developed via a gradient boosting decision tree in this study. The models can explore the underlying input–output transfer relationship of datasets and realize rapid intelligent identification of FDs without wind tunnel tests or numerical simulation. This method also provides a convenient and feasible option for expanding datasets of FDs, and the distribution of FDs can be analyzed through the post-interpretation of trained models. Combined with FD sensitivity analysis, the models can be verified by the calculation error of CFV. In addition, the proposed method can help determine the appropriate shape of the box girder cross-section in the preliminary design stage of long-span bridges and provide the necessary reference for aerodynamic shape optimization by modifying the local geometric features of the cross-section.