Finite Element Model Of Structure Research Articles

Vacuum and Hover Tests of a Dihedral–Anhedral Tip Composite Rotor

This paper presents test data from vacuum and hover tests of a 2.8-ft-radius dihedral–anhedral tip composite rotor. The paper describes the blades, their fabrication, properties, instrumentation, the test conditions, and the data acquired. The blades were Mach-scaled to a generic but representative modern rotor. Vacuum chamber tests measured rotating frequencies and strains. Hover tests measured performance, blade loads, pitch-link loads, and strains under steady and cyclic loading conditions. Three-dimensional finite element structural models were developed to ensure completeness and consistency of property definition. The three-dimensional analysis was also used for a preliminary assessment of the test data. The test data revealed that the dihedral–anhedral tip influences the torsional and higher frequencies of a rotor blade significantly. The oscillatory blade loads show patterns consistent with the vertical center-of-gravity offset introduced by the tip. The surface strains reveal interesting higher-harmonic patterns of loading particularly near the dihedral junction.

Application of Finite Element Method to Create a Digital Elevation Model

The generation of a topographical surface or digital elevation model for a given set of points in space is a known problem in civil engineering and topography. In this article, we propose a simple and efficient way to obtain the terrain surface by using a structural shell finite element model, giving advice on how to implement it. The proposed methodology does not need a large number of points to define the terrain, so it is especially suitable to be used with data provided by manual topographical tools. Several examples are developed to demonstrate the easiness and accuracy of the methodology. The digital terrain model of a real landscape is modeled by using different numbers of points (from 49 to 400) using a regular mesh or a randomly generated cloud of points. The results are compared, showing how the proposed methodology creates a sufficiently accurate model, even with a low number of points (compared with the thousands of points handled in a LiDAR representation). A real case application is also shown. As an appendix, the sample code to generate the examples is provided.

Sensitivity Analysis of the Main Structural Parameters of the Four-Tower Partially Cable-Stayed Bridge

We established a structural finite element model based on a four-tower partially cable-stayed bridge. We performed a study to determine the appropriate settings of several main parameters of the four-tower partially cable-stayed bridge. Given changes in the stiffness of the main girder, stayed cable and length of cable-free zones in the span, a three-parameter coupling coordination model was constructed. The coupling degree and coordination degree between different parameters are calculated and compared, the primary and secondary parameters affecting the structural performance of some cable-stayed bridges are determined, and a more suitable parameter composition interval is proposed. The sensitivity analysis of the main structural parameters of the four-tower partial cable-stayed bridge has not been published in the literature, and there is no coupling study on the length of the cable-free zone and the stiffness of the main girder and stay cable. The overall structural stiffness was improved by increasing the main girder’s stiffness and stayed cable, with the main girder stiffness being the primary parameter. The increase in uncoupled zone length in the span improved the utilization rate of the line within a specific range; however, too long a length led to a reduction in overall structural stiffness. The main girder stiffness was set between EG′IG/EGIG = 1~3, while stayed cable stiffness was set between ECAC′/ECAC = 0.8~1.4. The length of the cable-free zone in the span was set between l1/l0 = 0.08~0.15, while the coupling coordination degree was medium to high coordination. The structural performance of the background engineering bridge was improved. However, the conclusion of this paper is more applicable to low-pylon cable-stayed bridges, and it has not been verified whether it applies to traditional cable-stayed bridges.

Model Updating for a Continuous Concrete Girder Bridge Using Data from Construction Monitoring

Finite element (FE) model updating can guarantee the accuracy of the numerical analyses for civil structures. However, two deficiencies currently exist with the traditional FE model updating technique based on the measurements of modal parameters and/or the static structural responses of the built structure with respect to its reference information insufficiency and its non-unique solution generally obtained, hampering its extensive use. It becomes the goal of the whole engineering community to introduce new effective methods for the civil structural FE model update. To this end, an innovative FE model updating method using data from construction monitoring is proposed in this article. With regard to its theoretical novelty, the new method transforms the complicated multi-variable optimization mathematical problem with the traditional FE model updating technique into many simple single-variable parameter identification problems. Under the engineering background of Huangsha Harbor Bridge, a three-span concrete continuous box girder bridge constructed utilizing the symmetric cantilever casting method, the effectiveness and the efficiency of the new model updating practice were validated. It is demonstrated using quantitative data that the abundant data measured on Huangsha Harbor Bridge in construction stages can enhance the reference information for the more accurate FE model updating of the structure, and the uncertain parameters with the initial FE model of Huangsha Harbor Bridge can be progressively and easily identified for the proposed model updating method using many single-variable linear regression models, instead of one complicated multi-variable mathematical or numerical model employed by the traditional model updating approaches, which generally leads to non-unique solutions rendered by normal optimization algorithms.

Structure damage identification in dams using sparse polynomial chaos expansion combined with hybrid K-means clustering optimizer and genetic algorithm

Structural damage identification plays a crucial role in structural health monitoring. In this study, a novelty method for structural damage identification is developed, which employs an advanced surrogate modelling technique to drive a new hybrid optimization strategy, namely a combination of K-means clustering optimizer and genetic algorithm (HKOGA). The core of this method is using the reliable sparse polynomial chaos expansion model as a cost-effective substitute for the computationally expensive structural finite element models, thus greatly improving the efficiency of the optimization strategy in finding the optimal value of the objective function. To evaluate the performance of this hybrid optimization strategy, seven optimization algorithms are selected and compared with it for 23 classical benchmark functions, and the comparative results show that the HKOGA has the best performance. Taking a small-scaled laboratory dam as an example, the efficiency and reliability of the proposed method to cope with the problems concerning finite element model updating and structural damage identification are explored. Two important findings are as follows. (i) For finite element model updating, compared to the conventional method based on iterative optimization, the proposed method improves computational efficiency by a factor of 59 while maintaining computational accuracy. (ii) For structural damage identification, leaving aside the huge leap in computational efficiency, the HKOGA has a faster convergence rate, stronger robustness, and higher accuracy than its sub-algorithm K-means clustering optimizer (KO). The results show that this method can be severed as an extremely efficient and potential tool to identify damage in large and complex structures.

Tool Failure Analysis and Multi-Objective Optimization of a Cutting-Type Energy-Absorbing Structure for Subway Vehicles

This paper aims to provide essential guidance for the crashworthiness design of cutting energy-absorbing structures for subway vehicles. By investigating tool failure with experiment and numerical approaches, a new energy-absorbing tube structure was proposed and optimized to improve the crashworthiness and reliability of the cutting energy-absorption structure. The impact test results revealed that multiple failure modes occurred in the tool. Mechanical wear occurs mainly in the middle of the cutting edge, while the tool’s tip failure is primarily due to thermal wear. Impact forces were no longer stable due to tool failure. The simulation results of the established tool-tube thermal–structural coupling finite element model were consistent with the tests. The temperature distribution indirectly validated the failure modes in different tool areas. By eliminating the tearing-type fracture mode, the proposed new structure effectively reduced the high temperature of the tool’s tip, better maintained the uniform temperature of the cutting edge, and smoothed changing of the cutting force. Finally, the Kriging surrogate model and NSGA-II algorithm were utilized to obtain the tool’s minimum steady-state temperature (STT) and maximum mean average cutting force (MCF). The optimal solution determined by the minimum distance method is STT = 514 K, MCF = 131 kN.

Strain-Sensing Composite Nanofiber Filament and Regulation Mechanism of Shoulder Peaks Based on Carbon Nanomaterial Dispersion.

Conductive polymer composite-based strain sensors are essential components of flexible wearable devices. However, nonmonotonic responses with shoulder peaks limit their practical application. Herein, we innovatively optimized the shoulder-peak phenomenon in a strain-sensing composite nanofiber filament by regulating carbon nanomaterial dispersion. Further, the preparation methods, characteristics, and performances of the filament strain sensors were systematically introduced. On this basis, transmission electron microscopy, finite element analysis, and mathematic and structural evolution models were used to explore the origin of shoulder peaks and explain the sensing mechanism of conductive networks. Results confirmed that the beacon tower-shaped conductive network designed by constructing nanofiller agglomerates could cause strain concentration and resist the Poisson transverse contraction of nanofibers, considerably improving the monotonicity and sensitivity of the sensor. The strain-sensing performance was optimal when the nanofillers were dispersed using 2.5 wt % of an anionic dispersant. The sensor exhibited a maximum detective strain of 120%, an ultralow detection limit of 0.01%, and high sensitivity and linearity of 9.66 and 0.996 within 20% strain, respectively. Moreover, it showed the advantages of a fast response time (120 ms), excellent durability (3000 cycles), anti-interference, washability, and antibacterial capability. Finally, a smart Kinesio tape was developed for protecting/treating the human body and detecting joint/muscle movement via simple sewing.

Reduced-Order Identification of Aeroelastic Systems with Constrained and Imposed Poles

This work investigates the identification of reduced-order state-space models from aeroelastic simulations of the interaction of a built-in structural finite element model and a linear aerodynamic model using unsteady potential theory. The objective is to propose and compare different new frequency-based identification methods operating on frequency response associated to the inputs and outputs of interest. The first methods considered are the Loewner interpolation method and a subspace algorithm. Subsequently, the paper introduces the possibility to apply stability constraints and to impose a certain number of poles estimated beforehand by the method in order to make the identified models closer to the true aeroelastic physics. To achieve this goal, new dedicated techniques are developed and subsequently validated on data generated by random state-space models of various orders, and on aeroelastic data obtained from structural and aerodynamic aircraft models.

Parametric design methods development for the comparison of American football faceguards using validated structural stiffness models

Recent advances in headgear design research have sought to inform athletes’ safety related decisions by ranking headgear systems according to impact performance. These rankings have provided athletes with greater agency in their safety-related decisions. Despite these improvements, little quantitative information exists to compare faceguard performance. Using validated structural stiffness finite element models, this study sought to develop a parametric design approach that could be consistently applied to faceguards of different qualitative categories and of different helmet-compatible series. The methods presented in this study detail the objective measurement techniques and parameters of interest used to fully define three common American football faceguards. The results of this study indicate an ability to define parameters consistently for faceguards of different qualitative categories and of different helmet-compatible series. The high degree of correlation between mass and structural stiffness indicates expected model performance – providing increased confidence in results. Intuitively, the greatest effect on mass and structural stiffness was the size of the diameter of the main bars. Increases in mass were achieved with minimal changes in structural stiffness. Conversely, increases in structural stiffness were achieved with minimal changes in mass. These results have implications for manufacturers as some faceguards, such as those classified as “overbuilt,” are banned – in part – for their weight. Future work should continue to compare manufacturers’ original designs and investigate other metrics to further quantify performance and safety for athletes. This tool may be used to improve new faceguard designs by comparing new models to faceguards allowed for use.

Предложения по комплексным обследованиям и расчетным исследованиям сооружений и конструкций ТЭЦ с целью повышения сейсмостойкости

The purpose of the work is to carry out surveys to determine the actual state of thermal power plants located in areas with high seismic activity on the basis of comprehensive instrumental surveys and computational studies. The authors present an approach to the assessment of long-term operated thermal power plants in the zone of increased seismic activity. Over the period of long-term operation, the building structures have undergone changes in comparison with the design prerequisites, while the current regulatory documents contain instructions for the use of an increase in the calculated seismicity by 1‑2 points relative to the design data of the 60‑70 years. The article provides recommendations for drawing up a program for visual inspection of metal and reinforced concrete structures, as well as comprehensive instrumental surveys Thus, the thermal power plants built 45‑60 years ago and currently in operation are experiencing a lack of reliability during high-intensity seismic events. The article provides recommendations for drawing up a program of visual inspection of metal and reinforced concrete structures, as well as comprehensive instrumental surveys. Recommendations for drawing up a program for visual inspection of metal and reinforced concrete structures, as well as comprehensive instrumental surveys are presented. Proposals are given for the development of finite element models of structures for assessing seismic resistance to the effects of a design and control earthquake.

Behaviour of non-ballast pre-stressed and precast track structures in high speed railway based on multiscale finite element model

In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures, which was self-designed in China, based on the method of the multiscale finite element model (FEM), the traditional FEM of slab non-ballast track structures was improved. The multiscale FEM of CRTSIII type slab non-ballast track structures was established based on the general finite element program ABAQUS. Then the comparative calculation was made between various FEMs, showing that the high solution precision, fast modelling speed and high solution efficiency could be obtained. Therefore, the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSIII type slab non-ballast track structures, and then the key influence factor and constructions could be optimized.

Collapse mechanism of historical masonry mosques under strong ground motions

The protection of historical masonry mosques against earthquakes can be achieved by an accurate assessment of nonlinear behavior, such as heavy damage and collapse. To this end, nonlinear analysis of 3D finite element models of structures is a common and reliable approach. This article examines the seismic performance of four historical mosques, which are defined as cultural assets by the Ministry of Tourism and Culture of the Republic of Turkey, under the influence of earthquake ground motion. Three of these mosques have not been studied before using any advanced numerical simulation method. In addition, no studies have been conducted to determine the damage propagation and collapse mechanisms of these mosques. Detailed finite element models were developed by defining the architectural features of mosques. In order to obtain the seismic behavior and collapse mechanisms of the mosques, nonlinear dynamic analyses were performed using the ground motion records from 1992 Erzincan, 1992 Cape Mendocino and 1995 Kobe earthquakes. An evaluation has been made for mosques in terms of mode shapes, maximum principal strains, maximum displacements, damage distributions and failure mechanisms. It has been determined that the crack distribution and damage mechanism can be generalized in historical masonry domed mosques with square plan.

FEM Applications of Catenary Type Structures

The paper deals with Finite Element Modeling of catenary type structures starting from practical problems related to a single cable segment in the case of an electric transmission line. Finite element models allow the analysis of the resulting deformed position and stress state for a given configuration obtained by using the geometric and physical data of a cable. Beam type linear/nonlinear finite element models which can take into account also the temperature variation and extra loading on the cable were developed. Another application of this type of models is for the case of form finding of aerial refueling cable subjected to dynamic pressure. The results were obtained by the commercial finite element software ANSYS.

Investigation on temperature uniformity control of titanium extrusion in hot stretch bending process

Regarding to the impact of temperature on springback in hot stretch bending (HSB) process, this work proposed an investigation on temperature uniformity control of titanium extrusion in HSB process based on the mould which can be elevated by resistance heating. Prior to the HSB test, mould structure was designed to fit for resistance heating. Coupled thermal electrical structural finite element model of HSB process was created in ABAQUS. Resistance heating and HSB tests were performed using displacement control electrically assisted stretch bending machine. The results of simulation indicate that the temperature uniformity of titanium extrusion and the forming accuracy of curved part can be effectively improved by increasing the initial temperature of mould. At last, the curved part of titanium extrusion with L-section was achieved, and the forming accuracy of which was measured and evaluated.

Finite Element Model Updating of RC Bridge Structure with Static Load Testing: A Case Study of Vietnamese ThiThac Bridge in Coastal and Marine Environment.

Diagnostic load testing refers to the use of the measured historical responses of the structure in the field data to better understand its dynamic and static structural behaviours. It is important and necessary to predict the health state, load capacity, and aging of the structure by updating the finite element (FE) model, which can give useful information to aid the design of retrofits and the maintenance of the existing bridge in the future. The paper presents an update of the full-scale FE model for the reinforced concrete (RC) bridge structure over the seawater river based on the experimental strains under the static load testing in which the representative FE model of the actual structure is determined from the optimisation procedures. The optimisation variables are applied, including the cross-sectional properties and concrete material calibrated through the genetic algorithm (GA) optimisation in the MATLAB software, which interfaces with the FE modelling in the scripting of the SOFISTIK TEDDY software automatically. The bending moments at the mid-span of the RC girders are determined in the FE modelling to compute stresses, which are compared with the measured stresses through optimisation scenarios with a percentage error of the objective function less than 10%. The measured data of concrete strains are recorded from reusable strain transducers installed on the mid-span girders for every bridge span, which are used to calibrate the bridge model in static load testing. The novelty of the solution is to implement innovative techniques using field data as an improved approach for calibrating automatically the analytical FE model parameters of all RC spans of the bridge until its static behaviours are very similar to those of the actual bridge. The final updated FE modelling is used to apply truck load configurations according to bridge design standards such as the AASHTO specifications, which can predict the load limits of the existing bridge structure more accurately and reliably. These proposed approaches can be applied to large bridges as well as complex structures with supporting FE analysis software and data processing software.

Biomechanical effects of the tibial slope angle change on total knee prosthesis: 3D finite elements analysis

: In total knee arthroplasty, finding the correct tibial slope angle while placing the prosthesis affects the joint load. In our study; the load on the tibial insert and the notch of the insert as a result of flexion of the knee joint 0-30-60-90 degrees at each inclination in prostheses applied with posterior inclination angles of 0,3,5 and 7 degrees was examined in the three-dimensional right knee finite element structural model. In this way, it was aimed to reveal at which slope the resulting load is the lowest. The finite element structural model was created using the 3D 2.5 number right knee solid model. Two types of analysis were performed to examine the effect of angle change of the PE Insert on tibia component; static structural analysis with static loads at certain fixed flexion angles, and transient analysis with time for varying loadings at dynamically changing flexion angles with rotation of the knee between 0-90 degrees. In the 0 and 30 degree models, the least load on the tibial insert was found at 7 degree tibial slop angle (11.6 and 9.87 mpa, respectively), in 60 and 90 degree models at 5 degree tibial slop angle (9.07 and 11.4 mpa respectively). In the models of 0 and 30 degrees, no pressure occured on the tibial insert notch at 3,5,7 degrees of tibial slop angles, while in the 60 degree model, a pressure of 0,153 MPa occured at all 0,3,5,7 degrees at 0 degrees tibial insert slop angle and this pressure was centered at the junction with the tibial insert. The higher the load on the tibial insert, the greater wear of the tibial insert in the knee prosthesis. For this reason, it is important with which slop angle the tibial insert should be placed during surgery.

Diameter-thickness ratio influence on large civil aircraft fuse pins’ strength

The emergency break-away technology of civil aircraft is particularly important to the safety of aircraft, and the fuse pin is the key to the realization of emergency break-away technology. A type of civil aircraft pylon fuse pin was taken as the research object. Firstly, the finite element structure model of the fuse pin was established by ABAQUS, and the explicit dynamic algorithm was used to study the break-away process and load of the fuse pins. Secondly, the shear failure test of the fuse pin was designed to verify the accuracy of the finite element model. Finally, the influence of the diameter-thickness ratio on the failure mode and load of the fuse pins was studied. Comparing the failure load with the theoretical value, it can be concluded that the simulated and theoretical values of the failure load of the fuse pins were in good agreement under a certain range of diameter -thickness ratio, which provided references for the selection of the real fuse pins.

Numerical modelling of LSF walls under combined compression and bending actions and fire conditions

Numerical modelling of cold-formed steel walls used in determining the ambient temperature ultimate capacities has evolved from the use of idealised stud-only models to advanced models by employing sheathing and connection characteristics. Due to the convergence issues associated with elevated temperature structural models, attempts to incorporate sheathing are scarcely seen in the literature. In this study, the behaviour of light gauge steel framed (LSF) walls under combined axial and lateral loads and fire exposure was investigated by using stud-only and advanced structural finite element (FE) models. The advanced model is an improved single stud model which included gypsum plasterboard sheathing while also making models computationally less demanding. It incorporated material and geometric non-linearities, contact interactions, idealised in-plane restraints and explicit modelling of gypsum plasterboard sheathing, and was validated using full-scale fire test results. The predicted fire resistance levels (FRLs), failure modes, axial shortening and lateral deflection plots showed good agreement with fire test results. Furthermore, thermal FE models were also developed and validated against fire test results. They will be extended to obtain the time–temperature profiles of cavity insulated and non-insulated single and double plasterboard sheathed LSF walls exposed to fire for use in structural parametric studies. This paper summarises the findings of this study and proposes suitable recommendations for FE modelling of LSF walls under combined compression and bending actions and fire conditions.

Thermal-structural reduced order models for unsteady/dynamic response of heated structures in large deformations

This paper focuses on applications of recently developed thermoelastic reduced order models (ROMs) for the geometrically nonlinear response and temperature of heated structures. In these ROMs, both displacements and temperature fields with respect to the undeformed, unheated configuration are expressed in a reduced order modeling format, i.e., as modal-type expansions of the spatial and temporal variables with constant basis functions. Accordingly, the time varying generalized coordinates of the response and temperature expansions satisfy a generic set of coupled nonlinear differential equations derived from finite deformations thermoelasticity using a Galerkin approach. Finally, the coefficients of these governing equations, which characterize the structure considered and its loading conditions, are determined from structural and thermal finite element models non intrusively so that commercial finite element software can be used. This approach is considered here for the prediction of the displacements and stress fields in the presence of unsteady temperature distributions to enrich previous investigations limited to steady temperature distributions. Specifically considered here are: (i) a panel undergoing rapid heating and (ii) an oscillating flux on a panel. These problems not only demonstrate the extension of the thermal-structural reduced order framework to unsteady problems but also show the importance of the selection of the basis functions. It is also noted that the temperature dependence of the linear stiffness coefficients on temperature can induce in the unsteady situation the existence of a parametric-type excitation of the structure. This behavior is studied in the oscillating flux example and a strong sub-harmonic resonance is in particular found. The computational benefit of using ROMs is discussed and demonstrated.

The Effect of Cold Waves on the Structural Performance of Concrete Box Girders

As the frequency of thermal extremes gradually increases owing to climate change, the role of thermal loads on bridge performance increasingly becomes a concern. The purpose of this study is to investigate the suitability of AASHTO Bridge Design Specifications in quantifying with confidence the design thermal gradients that account for cold wave events. An advanced finite element platform was used to model the thermal performance of a prestressed concrete box girder and to analyse the thermal gradients that occur during cold wave events. Meteorological data on four historical cold wave events in Ontario, Canada, were used as input in the thermal models to simulate the temperature distribution within the bridge deck. The temperature–time history distributions obtained were then used as boundary conditions in a structural finite element model to simulate the structural response. The thermal results indicate that the AASHTO recommended gradients failed to capture the true thermal load distribution within the superstructure, which led to an underestimation of the resulting structural implications.