Deflection Of Structure Research Articles

Experimental Study on the Optimal-Based Vibration Control of a Wind Turbine Tower Using a Small-Scale Electric Drive with MR Damper Support

The paper presents an experimental implementation of an optimal-based vibration control for a scaled wind turbine tower-nacelle structure. A laboratory model of the approximate power scale of 340 W, equipped with a nonlinear tuned vibration absorber (TVA), is analysed. For control purposes, a combined operation of a small-scale electric servo drive and a magnetorheological (MR) damper is used in the TVA system. Nonlinearities of both the electric drive and the MR damper are intrinsic parts of the adopted nonlinear control concept. The aim of the research is the simple-hardware real-time implementation and the experimental investigation of the simultaneous actuator and damper control, including the analysis of the influence of optimal control law parameters and quality function weights on the vibration attenuation efficiency and actuator energy demand. As a reference, an optimal-based, modified ground-hook control with the single goal of the primary structure deflection minimisation is used along with the passive system with zero MR damper current and idling electric actuator, proving the advantages of the proposed method. The regarded solutions guarantee 57% maximum structure deflection reduction concerning the passive TVA configuration, using an MR damper of 32 N maximum force and an electric drive of 12.5 N nominal force and 0.76 W nominal power. An interesting alternative is the optimal control concept tuned with regard to the actuator power minimisation—it provides 30% maximum structure deflection attenuation (concerning the passive TVA configuration) while using a passive damper of 3.3 N maximum force and an actuator of 0.17 W nominal power only. It makes evident the advantage of the properly tuned optimal control algorithm over the modified ground-hook law—it requires 51% less actuator energy than the latter parametrised to exhibit the same vibration attenuation properties.

Novel constitutive model of UHPC under impact and blast loadings considering compaction of shear dilation

Based on the framework of elastic-plastic-hydrocode concrete model, this study established a novel constitutive model of ultra-high performance concrete (UHPC) for impact and blast loadings considering the compaction of shear dilation. First, the established UHPC model is introduced, including five parts: (i) the dynamic failure strength surface, which is divided into tensile, compressive, and tensile-to-compressive regions and considers the Lode-dependence and strain rate effect; (ii) equation of state (EOS) that accounts for the nonlinear volumetric compaction; (iii) damage of strength, which contains independently described tensile and compressive strength hardening or softening formulae; (iv) damage of stiffness for depicting the compaction of shear dilation; (v) plastic flow rule, where the radial return algorithm is adopted for updating stress and an independent plastic potential function is employed to model the shear dilation. Then, parameters of the established UHPC model are systematically calibrated according to tests and empirical suggestions, and are further validated by conducting single element tests under varying loading paths. Through simulating the tests of reinforced UHPC beams/columns and UHPC filled steel tubes under drop hammer impact and reinforced UHPC panels under field explosion, it demonstrates that both the damage patterns and deflection-time histories of UHPC members are precisely reproduced by the established UHPC model. Furthermore, based on comparative simulations, it shows the compaction of shear dilation is critical for predicting the structural residual deflection of reinforced UHPC members. This study discloses a possibility to establish a constitutive model of concrete suitable for impact and blast scenarios with a wide range of strain rate and hydrostatic pressure.

Research on the accuracy of the generalized Lévy’s solution for deflection of open cylindrical shell structures

In the last century, the plate and shell theory has been developed and matured through the research of many theoretical workers at home and abroad. The generalized Lévy’s solution can be used to obtain the static response of a semi-cylindrical shell with curved ends simply supported under arbitrary load. However, the solution is complex and difficult to calculate, so on this basis, a series of simplified methods under specific working conditions are developed, such as the moment-free theory and semi-moment-free theory of cylindrical shells. In this paper, MATLAB will be used to calculate the generalized Levi’s solution and semi-moment-free theory, and compare them with the finite element results of ANSYS. Finally, it is found that the two theoretical solutions can only roughly predict the distribution form of displacement, with an order of magnitude difference. The engineering significance is limited, and the results still need to be improved.

Parked aeroelastic field rotor response for a 20% scaled demonstrator of a 13‐MW downwind turbine

AbstractAeroelastic parked testing of a unique downwind two‐bladed subscale rotor was completed to characterize the response of an extreme‐scale 13‐MW turbine in high‐wind parked conditions. A 20% geometric scaling was used resulting in scaled 20‐m‐long blades, whose structural and stiffness properties were designed using aeroelastic scaling to replicate the nondimensional structural aeroelastic deflections and dynamics that would occur for a lightweight, downwind 13‐MW rotor. The subscale rotor was mounted and field tested on the two‐bladed Controls Advanced Research Turbine (CART2) at the National Renewable Energy Laboratory's Flatiron Campus (NREL FC). The parked testing of these highly flexible blades included both pitch‐to‐run and pitch‐to‐feather configurations with the blades in the horizontal braked orientation. The collected experimental data includes the unsteady flapwise root bending moments and tip deflections as a function of inflow wind conditions. The bending moments are based on strain gauges located in the root section, whereas the tip deflections are captured by a video camera on the hub of the turbine pointed toward the tip of the blade. The experimental results are compared against computational predictions generated by FAST, a wind turbine simulation software, for the subscale and full‐scale models with consistent unsteady wind fields. FAST reasonably predicted the bending moments and deflections of the experimental data in terms of both the mean and standard deviations. These results demonstrate the efficacy of the first such aeroelastically scaled turbine test and demonstrate that a highly flexible lightweight downwind coned rotor can be designed to withstand extreme loads in parked conditions.

The combined refraction–diffraction effect on water wave scattering by a vertical flexible–porous structure

This article investigates the combined effect of refraction–diffraction due to bottom topography on water wave scattering by a vertical flexible–porous structure. This model problem assumes two partial configurations of the structure, such as surface-piercing and bottom-standing positions. Wave scattering is studied under the assumptions of small amplitude water wave theory and Darcy law for flow through the porous medium. The solution method uses Eigenfunction expansion of velocity potentials in the uniform bottom region and the Galerkin-Eigenfunction expansion in the variable bottom region. The structure deflection is obtained by Green’s function technique. From the porous boundary condition, a Fredholm integral equation with Green’s function as the kernel is derived, and its solution is approximated by Galerkin expansion. The associated boundary value problem is converted to a system of algebraic equations. The variations of reflection and transmission coefficients of incident waves are illustrated with parameters related to waves and flexible structure. The flexible structure effect on Bragg resonance is explored in the case of a rippled bottom. Furthermore, the effect of depth ratio on wave scattering is studied in the case of a sloping plane step-type bottom. Some striking results are derived from this model. Bragg resonance reduces with increasing thickness of flexible structure and friction of porous medium at Bragg primary frequency, whereas it increases at other frequencies. On the other hand, the resonance enhances when plate flexibility decreases and porosity increases. Further, Bragg resonance magnifies with a wide frequency band while shifting towards the left at higher incident angles. In this situation, structure deflection increases with the increased incident wave angle and diminishes for angles greater than a particular incident angle. Structure deflection increases with decreasing water-depth ratio in the presence of sloping plane bottom.

Thermal, electrical and structural characteristics under different concentrator positions for Fresnel concentrating photovoltaic system

There are always installation errors in linear Fresnel concentrating photovoltaic (CPV) system that make the system unable to work under the designed conditions. Based on the optical, thermal, electrical, and structural coupling principle, the influences of vertical position (including distance and direction) e of concentrator deviation from the focal length on the thermal (heat flux and temperature distributions), electrical (average electrical efficiency) and structural (stress and deflection) characteristics of PV panel under natural convection conditions were investigated numerically by MCRT-FVM-FEM coupling method. The results reveal that, the thermal, electrical and structural characteristics change slightly with the tilt angle α of PV panel from 15° to 60°, while these characteristics experience a relatively greater change for α increasing to 75°. The concentrator position has little effect on the flow and temperature fields near the PV panel. Compared with the situation at α = 30°, changing the concentrator position at α = 75° has a more obvious effect on the thermal and structural characteristics of PV panel. When the concentrator moves from the designed position (e = 0 mm) to the deviated position (e = −45mm) at α = 75°, the maximum thermal stress and maximum deflection of cells are dropped by 30.12% and 13.72%, respectively. Even if the concentrator moves the same distance, different directions (upward and downward) of movement can lead to differences in the thermal and structural characteristics. The change trend and magnitude of average electrical efficiency with the position of concentrator when α = 30° are both opposite to those when α = 75°. The average electrical efficiency at α = 30° decreases from 7.76% at the designed position (e = 0 mm) to 7.62% at the deviated position (e = −45mm), while the average electrical efficiency at α = 75° increases from 9.26% to 10.54%.

Bending deformable tension-shear model for nacre-like composites

The nacre-like structures widely exist in biomaterials and bioinspired composites, where the tension-shear load transfer is the common load carrying mode due to the discontinuous platelet. However, under bending deformation the local tension-shear load transfer is coupled with the global bending deformation which can't be described by the widely-adopted theoretical models in nacre-like composites, like the tension-shear chain (TSC) model and deformable tension-shear (DTS) model. In this work, a bending deformable tension-shear model (BDTS) model was developed to capture the tension-shear load transfer under bending configuration. In order to obtain a closed-form solution of BDTS model, the bending deformation of equal curvature was first studied, based on which two failure modes were defined, i.e., intralayer failure (Mode G) and interlayer failure (Mode I). Then, the effective bending rigidity of nacre-like structure, defined as the ratio of the average moment to curvature, was obtained, indicating the influence of material and geometrical parameters can be unified to a dimensionless length parameter. Furthermore, a general beam theory of nacre-like structures was constructed by introducing the effective bending rigidity to the modified Timoshenko beam model, which can predict the deflection of nacre-like structures well. This work first explores the two coupled deformations of local tension-shear and global bending-shear in nacre-like composites, which may guide the design of nacre-like artificial nanocomposites toward various applications where bending deformation is inevitable.

Biomimetic laminated basalt fiber-reinforced composite with sinusoidally architected helicoidal structure integrating superior mechanical properties and microwave-transmissibility

High-efficient microwave-transmissibility, mechanical durability, and lightweight are in significant demand for wireless communication components. Unfortunately, conventional materials can hardly meet the requirements for emerging radio-frequency (RF) devices so far. Herein, inspired by the sinusoidally architected helicoidal structure of mantis shrimp's dactyl club, a biomimetic laminated basalt fiber-reinforced composite (BL-BFRC) is designed and manufactured through a method combining linear helicoidal layup and hot press forming. Remarkably, the flexural strength and flexural modulus of BL-BFRC are 259.71 MPa and 22.61 GPa, which increase by 28.4% and 36.9% over those of conventional BFRC (202.27 MPa and 16.52 GPa). In addition, BL-BFRC exhibits a dielectric constant of 2.2858 and a loss tangent of 1.55 × 10−3, which are much lower than those of conventional BFRC (3.6459 and 9.73 × 10−3). Accordingly, the microwave-transmissibility increases from 93.53% (conventional BFRC) to 98.34% (BL-BFRC). In fact, the superior mechanical durability of BL-BFRC is mainly attributed to the crack deflection of helicoidal structure and stress dissipation of sinusoidal morphology. And the efficient microwave-transmissibility benefits from dielectric transition effect on non-smooth sinusoidal surface. This work uniquely combines the features of high-efficient microwave-transmissibility and mechanical durability into RF devices and would enable a broad range of wireless communication applications.

Integrating flexibility-based curvature with quasi-static features induced by traffic loads for high-resolution damage localization in bridges

Curvature is one of the most popular damage-sensitive features in vibration-based structural health monitoring applications, typically calculated from identified modal features. While the relevant strategic or historical importance of bridges may justify dense sensor networks, a limited budget is generally assigned to monitor “minor” viaducts, thus involving inexpensive devices or extremely sparse sensing solutions. Modal parameters can only be obtained at instrumented locations. Thereby, damage assessment methods based on identified features typically have a low spatial resolution, especially when using low-cost monitoring setups with a modest number of sensing devices. This paper proposes an original identification method for the curvature of bridges based on sparse acceleration measurements that can be collected using standard accelerometers. The raw acceleration signal is processed through a particular filter bank that extracts dynamic and quasi-static signal components. The first components are employed to identify modal parameters, from which sparse yet robust estimates of the structural curvature are retrieved. On the other hand, the quasi-static acceleration generated by the structural deflection induced by traffic load is used to identify the curvature influence lines of the bridge, which are fused with modal estimates using a Kalman filter. The state variable of the analyzed system, representing a dense curvature profile of the structure subjected to concentrated loads, can be used as a damage-sensitive feature for high-resolution damage localization. The method is applied to a steel truss bridge subject to different damage configurations.

Flexural Behavior of Insulated Concrete Sandwich Panels using FRP-Jacketed Steel-Composite Connectors

This study presented the experimental and theoretical results of insulated concrete Sandwich panels with innovative dumbbell-shaped steel fiber-reinforced polymer (FRP) composite bar (SFCB) connectors under flexural load. The influences of FRP thickness and raised thickness of dumbbell ends of connectors, axial compression ratio, the content of vitrified microspheres in the wythes, and loading direction were discussed. The increase in thickness of a glass FRP (GFRP) jacket on the hybrid bar from 2 to 3 mm led to increased initial cracking load, ultimate load, and flexural stiffness of the Sandwich panels by 75, 49, and 16%, respectively. The increase in the thickness of dumbbell ends from 4 to 6 mm led to increased initial cracking load, ultimate load, and flexural stiffness of the Sandwich panels of 18, 46, and 9%, respectively. The incorporation of vitrified microspheres in concrete wythes resulted in a significant increase in the load-carrying capacity of Sandwich panels but decreased ductility. Increased axial compression ratio from 0/1 to 0.2/1 contributed in improving the crack resistance and ultimate loads of Sandwich panels. Further increase of the axial compression ratio to 0.4/1 led to crushing failure of concrete wythe ends. Specimens under negative loads had higher ultimate loads than the counterparts under positive loads. Three-dimensional finite-element (FE) models were developed to simulate Sandwich panel flexural behavior and numerical results compared with the test data. Then, the verified FE model was used to analyze the influence of the arrangement of dumbbell-shaped SFCB connectors. Increased connector spacing from 550 to 650 mm was found to have an insignificant influence on load-deflection responses. Moreover, analytical solutions for deflection of Sandwich panels under combined axial-flexural load were obtained, in which the effect of slipping between the facade and structural wythes and shear deflection were considered. The predicted deflection at the ultimate load agreed well with the test results. This study provided a theoretical basis and design reference for FRP-jacketed steel-composite connectors in applications of Sandwich wall panels with large insulation layer thickness.

Dam deformation early warning model based on cluster analysis and spatiotemporal data fusion

The deformation behavior has a vitally spatial correlation to hydraulic concrete structures. The majority of traditional monitoring model focuses on the displacement law of local monitoring points, in which the single objective method is employed, and results in the ignorance of temporal and spatial diversity of structural behaviors. Thus, the state of the whole structure cannot be truly reflected. In this paper, the correlation between the field data obtained from different measuring points was considered, and a dam deformation early warning model based on spatiotemporal data fusion was proposed. The model was established with respect to temporal and spatial dimensions, and the correlation of monitoring points was explored by utilizing cluster analysis. The cross-sectional series fusion model was used to establish the mapping relationship between environmental factors and cross-sectional clusters for extracting the variation regulation of overall horizontal displacements or the structural deflection curve for dams during long-term operation and identifying the abnormal deformation position. Meanwhile, the time series fusion model was established based on the insight of the Stacked Single-Target strategy, in which the correlation between monitoring points was fully utilized to improve the prediction accuracy. Then, it was used to judge whether the monitoring points conform with the operation regulation in temporal dimension. Based on the early warning model in spatiotemporal dimension, a comprehensive diagnosis method of dam deformation was proposed. In addition, this method can be used for further analyzing the critical environmental factors affecting the local and overall deformation of dams. Finally, a project was selected to verify the effectiveness of the proposed model through cluster analysis and spatiotemporal data fusion.

Theoretical study on progressive collapse of truss string structures under cable rupture

Cables are critical components of truss string structures and cable failure can cause serious damage to the structure or even progressive collapse. However, little theoretical research work deals with this phenomenon. In this study, a rapid analysis method for the progressive collapse of truss string structures based on the nonlinear buckling material model was proposed. The results showed that the rapid analysis method could reduce the computational time by at least 30% and effectively improve computational efficiency. Based on the validated rapid analysis method, the progressive collapse failure mechanism of truss string structures under cable rupture was analyzed. The results showed that progressive collapse failure mechanisms could be divided into two categories. In one category, compression buckling of the upper chord member leads to a loss of load capacity and a rapid increase in deflection without convergence, resulting in progressive collapse of the structure. In the other category, tensile yielding of the lower chord member results in a gradual loss of stiffness and a slow increase in deflection without convergence, leading to progressive collapse of the structure. Moreover, a series of assumptions and simplifications were made, followed by the establishment of calculation equations for the progressive collapse load capacity and deflection of truss string structures under cable rupture. By comparing the theoretical values with the finite element values as well as test values, the accuracy of the equations proposed in this study for calculating the progressive collapse load capacity and deflection of truss string structures was verified.

The role of soil structure interaction (SSI) on seismic response of tall buildings with variable embedded depths by experimental and numerical approaches

The soil-structure interaction is an integral part of the seismic evaluation, especially for structures with variable embedment depths. The purpose of this work is to ensure the adequacy of the small scaling factor in the dynamic analysis and study the seismic behavior of tall building with considering variable embedment depths and soil structure interaction effects. Therefore, scaled model tests of a 15-story steel structure were performed using shaking table tests and numerical simulations. Three scaled earthquake records, namely: Chi-Chi (1999), Northridge (1994), and Kobe (1995), were selected. The numerical scaled coupled models were implemented with Plaxis 3D software and validated with the experimental observations. Afterward, the experimental and numerical results of scaled models were verified with prototype models to ensure the adequacy of the small scaling coefficient. The results generated from small-scale models derived from experimental and numerical simulations were in good agreement. In addition, these results achieved good accuracy with full-scale field conditions in the seismic analysis. Therefore, a small geometric scaling coefficient of 1:50 achieved good accuracy for buildings with embedded parts to represent the dynamic behavior of structures. Within the frame results, it is noted that the SSI has an essential role in amplifying the lateral deflection of structures compared with a fixed base and thus the embedded depths significantly affect the lateral seismic response of the considered structures.

Investigation of Offshore Wind Turbine Structure Deflection Using Experimental Work, Numerical, and Theoretical Approach

Electrical energy from offshore wind turbines is an important source of clean, renewable energy production. One of the reasons for the low efficiency of wind turbines is the change in the flow angle of attack, denoted by the symbol (α), as a result of the deflection of the structure. The study aims to know the values of the maximum deflection of the proposed structure under the environmental conditions of the Arabian Gulf water area. Our research adopted a novel approach to extracting results; the characteristics of sea waves were extracted from the experimental work after fixing five sea waves, knowing the displacement of the top of the structure, and using the numerical approach in the ANSYS-Fluent program to know the average wind and wave forces. Two simulations were performed. The first included the five cases of sea wave characteristics without rotating wind turbine blades. The second was for the fifth case only with the wind turbine blades rotating at a speed of (20.5 rpm), assuming that the structure was exposed to a constant wind speed (12 m/s) for the two simulations. The study also included obtaining the maximum deflection value of the structure. Then, the equations of the theoretical approach were developed based on the Euler-Bernoulli bending moment equation, and the forces extracted from the simulations were entered into the theoretical equations to extract the maximum deflection values of the structure. Reading the experimental work resulted in the highest displacement of the top of the structure in the fifth case (0.178 m). The result of the second simulation had the highest value of the structure deflection (0.201 m). In comparison, its value came in the theoretical approach (0.160 m), which adopted the forces of the second simulation.

Virtual modelling technique for geometric-material nonlinear dynamics of structures

This paper presents a virtual modelling technique for dynamic safety assessment of practical structures undergoing geometric and material blended nonlinearities. The variational inputs of systematic properties are treated within the 3D dynamic geometric-elastoplastic analyses. To circumvent numerical challenges in solving the coupled nonlinear problems, a freshly developed dynamic virtual modelling (DVM) technique is employed to determine the inherent relationship between the variational input data and the nonlinear structural response by using a new clustering based extended support vector regression (C-XSVR) algorithm with a novel T-spline polynomial kernel function. The virtual modelling models can be constructed at each time step within the Newmark’s time integration procedure, which then can be used to predict deflection, force, and stress of the concerned structure at different periods. The DVM is capable of visibly forecasting potential large deformation nonlinear behaviours in an efficient manner, based on the explicit relationship functions. To demonstrate the accuracy and effectiveness of the proposed framework, nonlinear behaviours of two practical applications under future forecasted working conditions are predicted and validated in the numerical investigations.

The Simulation of the Dynamic Characteristics of Friction Stir Welding and the Structural Deflection of Base Materials

Friction stir welding requires an optimized process because the quality of the weld can vary depending on the dynamic characteristics of the welding tool. In addition, controlling the structural deflection of the base material according to the load of the welding tool is important. In this study, the structural deflection of thin base material according to the dynamic characteristics of the welding tool was confirmed using dynamic simulation. The generated deflection was controlled through the fixing clamp, and the results according to the rotation and progress speed of the welding tool were compared and analyzed through finite volume analysis. Thus, factors of the welding tools were obtained based on computational data without accompanying experimental data, and a process guide for efficient friction stir welding for thin base materials was presented.

ПАРАМЕТРИЧЕСКАЯ ОПТИМИЗАЦИЯ КОНСТРУКЦИИ НАВЕСА ЧИСЛЕННЫМИ МЕТОДАМИ

The article sets and solves the problem of finding the minimum weight of the canopy structure under the specified design scheme and loading conditions. At the same time, two variants of the design scheme are considered – with a canopy length of 3 and 6 m. The metal consumption of the structure is accepted as the criterion of optimality. The shape of the cross-section of the beam, the strength characteristics of the structural material and the geometric parameters of the structure are selected as variable parameters. The problem is solved by numerical method, for this purpose, by methods of structural mechanics, the forces in the structural elements, displacements and deflections of the beam and suspension are determined, then the obtained formal conditions of strength and stiffness are included in the algorithm on the basis of which a program is developed in one of the programming languages. In fact, the article solves the optimization problem according to the optimality criterion in the form of the cost of the structure, with limitations in the form of overall dimensions and conditions of strength and rigidity. This method will allow to quickly determine the stress of the structure, with a given design scheme, for any size, load and type of elements used. This approach can be considered as one of the applications of the BIM methodology, that is, to automate the process of designing a specific structure and can be used in practical work. It allows to significantly save time designing to find the optimal solution

Damage Detection of Steel Truss Bridges Based on Gaussian Bayesian Networks

This paper proposes the use of Gaussian Bayesian networks (GBNs) for damage detection of steel truss bridges by using the strain monitoring data. Based on the proposed damage detection procedure, a three-layer GBN model is first constructed based on the load factors, structural deflections, and the stress measurements of steel truss bridges. More specifically, the load factors of the structures are defined as the first-layer network nodes, structural deflections are considered as the second-layer network nodes, and the third-layer nodes of the GBN model are built based on the stress data of the truss elements. To achieve the training for the constructed GBN model, the finite element analysis of the bridge structures under the different load factors is performed. Then, the training of the network is performing by using the maximum likelihood estimation approach, and the optimized network parameters are obtained. Based on the trained network model, the measured load factors and the corresponding stress monitoring data of a limited number of truss elements are considered as input, and the stress measurements of all truss elements of bridges can be accurately estimated by searching the optimized topological information among network nodes. For a steel truss bridge, when the truss elements are damaged, the stress states of the damaged elements will be changed. Therefore, a damage index is further constructed for damage detection of steel truss bridges based on the changed stress states of those damaged elements. To verify the feasible and effective use of the proposed damage detection approach, an 80 m steel truss bridge with various damage cases was conducted as numerical simulations, and the investigation results show that the trained GBN can be accurately used for stress prediction of steel truss bridges, and the proposed damage index with the estimated stress data can be further applied for structural damage localization and quantification with a better accuracy. Furthermore, the results also suggest that the proposed damage detection procedure is accurate and reliable for steel truss bridges under vehicle loads.

Modelling the relationship of smoothness and resistibility in non-rigid pavements based on theoretical and practical studies

Introduction. The existing means of measuring the elastic deflection of the road structure in most countries are low-performance for the volume of the road network of a region or country. Deflectometers used in assessing the strength of road structures perform annual measurements for the season of positive temperatures up to about 3000 km per year. Thus, for the Republic of Belarus, the main strength parameter of the road is measured with a frequency of 5-7 years on the network of republican roads of about 16,000 km and with an even greater frequency for the road network of Russia and Kazakhstan. The current situation does not allow to determine the bearing capacity of the structure in a timely manner and the lack of information leads to damage from the passage ofheavy trucks, fares with a decrease in bearing capacity, the formation of critical defects in the road structure, and a decrease in the efficiency of budget allocation when planning repairs.Materials and methods. The research methodology is based on the existing practice of calculating the total modulus of elasticity, methods for predicting changes in the evenness of coatings. The model can be an addition to the existing system for assessing the transport and operational condition of roads at all levels.Results. The article presents a model of the dependence of evenness on the strength of the road structure. Based on the operating conditions and the initial value of the evenness of road surfaces, it is proposed to calculate the strength factor of road structures. The changes in the structure of materials cause deformations and irregularities, and the evenness index integrates all types of deformations. For this reason, it is assumed that there is a relationship between strength and evenness of road structures.Conclusion. The proposed model can be used primarily to assess the strength of roads of low categories, road sections of the local road network, i.e. where diagnostics are not carried out or are carried out with a large frequency. This model can be widely used by road industry enterprises, by a customer to select the most weakened road sections for repair, and by the contractor to calculate the reinforcement during repair work. The practical measurements in experimental areas confirm the dependence of the decrease in strength in areas with unsatisfactory evenness.

Comparative study on two-constant-amplitude input shapers to maneuver flexible satellite in small structural deflection

The satellite attitude maneuver using thrusters is studied in this paper. The satellite consists of a rigid main body and two symmetrical solar panels that are so large that their flexibility cannot be neglected. The finite element method is used to discretize the elastic motion of the solar panels. The solar panels are modeled as a set of rectangular plate elements and only out-of-plane displacement is taken into account. The satellite is controlled by a thruster in its main body, while there are no other control inputs on the solar panels. For the attitude maneuver, the roll, pitch and yaw torques generated by the on-off thruster are used and here can produce two different constant amplitudes. Then two types of fuel-efficient input shaping are formulated and applied to perform satellite attitude correction. The first type of input LHHL is preceded by the use of a small amplitude torque followed by a large amplitude one, while the sequence of torque applied to the second type of input HLLH is the opposite of the first input. The two types of inputs are applied separately to the same satellite. They managed to dampen the residual vibrations after reaching the desired attitude, but in achieving this condition the solar panels experienced considerable deflection during the transient response. Due to this, the effectiveness of the shaped inputs for maneuvering the satellites at small structural deflections of the solar panels during their transient responses is compared. The simulation results show that the use of the LHHL input shaper can minimize the structural deflection that occurs in the transient response during the satellite attitude maneuvering process.