Evaluation Of Dynamic Response Research Articles

A machine learning-based crashworthiness optimization for a novel pine cone-inspired multi-cell tubes under bending

Bionic tubes are of interest in vehicle engineering due to their superior crashworthiness potential. This study proposes a crashworthiness response investigation and machine learning-based multi-objective optimization of pine cone-inspired muti-celled tubes (PCMTs). The base computer PCMT model was correlated using existing experiments, followed by a dynamic response evaluation of different PCMT geometrical and thickness configurations to assess their structural performance. Surrogate models of these PCMTs were then constructed using machine learning algorithms, and their main and interaction effects were analyzed. A non-dominated sorting genetic algorithm II (NSGA-II) approach was employed to perform a multi-objective optimization. The results demonstrate that thickness change had more effect on the initial peak force (IPF) and the mean crushing force (MCF) than the specific energy absorption (SEA). Besides, due to the coupling effect, IPF, MCF and SEA of the optimal design solution of the PCMTs could reach a 36.82 %, 61.66 % and 72.95 % increase than the sum case, suggesting that embedding inner tubes could significantly increase energy absorption with a relative minor IPF increase. Moreover, the MCF and SEA of optimal design gave an average difference of 18.01 % and 5.91 % from the original tubes. PCMTs, therefore, could be used as an ideal energy absorption structure in the vehicle body structures.

Predictive evaluation of dynamic responses and frequencies of bridge using optimized VMD and genetic algorithm-back propagation approach

Predictive evaluation of dynamic responses and frequencies of bridge using optimized VMD and genetic algorithm-back propagation approach

Hybrid self-centering braces with NiTi-SMA U-shaped and frequency-dependent viscoelastic dampers for structural and nonstructural damage control

This study proposes a novel hybrid self-centering brace (HSB) with structural and nonstructural damage-control capabilities for the seismic resilience of building structures. NiTi-based shape memory alloy (SMA) U-shaped dampers and frequency-dependent viscoelastic dampers are included in HSBs to provide self-centering capacity for avoiding structural damage and velocity-proportional damping for nonstructural damage control, respectively. This study includes two major parts, i.e. component-level mechanical behaviour and system-level dynamic response evaluation of HSBs. The working principle and desired nonlinear behaviour of the HSB were first presented. Then, the preliminary design procedures were developed. After validating the efficiency of the modelling of SMA U-shaped and viscoelastic dampers using prior test results, comprehensive 3D finite element model simulations were performed to study the hysteretic responses of HSBs under cyclic loadings, where the influences of loading frequency, loading amplitude and viscoelastic damper’s contribution were considered. Analysis results demonstrated that the designed HSB can attain the desired deformation mechanism and nonlinear hysteretic behaviour during dynamic cyclic loadings. Higher loading frequency and amplitude and more contributions of the viscoelastic damper can introduce higher loading and energy-dissipation capacity. Subsequent dynamic analyses of the single-degree-of-freedom systems were conducted to assess the dynamic performance and advantages of HSBs. Results showed that compared with traditional self-centering systems without velocity-proportional damping, the systems with HSBs can achieve zero residual deformations, lower base shear demands and smaller absolute acceleration responses, confirming the promising potential of HSBs in developing seismic resilient building structures by reducing structural and nonstructural damage.

Review on Design, Characterization, and Prediction of Performance for Asphalt Materials and Asphalt Pavement Using Multi-Scale Numerical Simulation.

Asphalt pavement, which is mainly made up of the asphalt mixture, exhibits complicated mechanical behaviors under the combined effects of moving vehicle loads and external service environments. Multi-scale numerical simulation can well characterize behaviors of asphalt materials and asphalt pavement, and the essential research progress is systematically summarized from an entire view. This paper reviews extensive research works concerning aspects of the design, characterization, and prediction of performance for asphalt materials and asphalt pavement based on multi-scale numerical simulation. Firstly, full-scale performance modeling on asphalt pavement is discussed from aspects of structural dynamic response, structural and material evaluation, and wheel-pavement interaction. The correlation between asphalt material properties and pavement performance is also analyzed, and so is the hydroplaning phenomenon. Macro- and mesoscale simulations on the mechanical property characterization of the asphalt mixture and its components are then investigated, while virtual proportion design for the asphalt mixture is introduced. Features of two-dimensional and three-dimensional microscale modeling on the asphalt mixture are summarized, followed by molecular dynamics simulation on asphalt binders, aggregates, and their interface, while nanoscale behavior modeling on asphalt binders is presented. Finally, aspects that need more attention concerning this study's topic are discussed, and several suggestions for future investigations are also presented.

Distributed real-time hybrid simulation method for dynamic response evaluation of floating wind turbines

Limited land and near coast spaces led to the development of floating wind turbine (FWT) farms in unlimited space of deep water with steady winds. Experimental evaluation of dynamic responses of FWT is essential to ensure its safe operation. However, due to laboratory limitations and scaling issues, realistic FWT responses are difficult to be replicated on scaled-down test specimens. To facilitate larger-scale testing of FWT and apply realistic wind and wave loads, distributed real-time hybrid simulation (dRTHS) method is proposed which combines the testing of FWT substructures at geographically distributed laboratories using wind tunnels and wave tanks. In this research, dRTHS experimental method for FWT is developed and its feasibility is verified through a series of virtual dRTHS (vdRTHS) and proof-of-the-concept partial dRTHS tests. The equation of motion of a prototype FWT structure under coupled aerodynamic and hydrodynamic loads was partitioned to represent the wind turbine tower and platform substructures, based on which substructural formulation was derived. During the vdRTHS, two distributed real-time controllers were used to simulate the physical testing of the two substructures tested in the wind tunnel and water tank, respectively, with interfacing data being transferred in real-time through a network. FWT responses from vdRTHS match well with those obtained from numerical simulations of the whole FWT model and the substructured models, demonstrating that the feasibility of the proposed dRTHS method. In addition, the substructuring approach, the vdRTHS testing platform, and the method to overcome network communication delay are effective in the vdRTHS resulting in reliable FWT dynamic responses under coupled loading conditions. Furthermore, the proposed dRTHS concept was verified through a partial distributed physical tests during which the wind turbine substructure was tested physically, while the platform substructure and the hydrodynamic loads were simulated numerically.

Dynamic response and design evaluation of circular CFT columns with ring-shaped voids under transverse impact

Presently, the research on the impact performance of the concrete-filled steel tubular (CFT) members has never considered the problem of void defect. Hence, this paper fosters a refined finite element (FE) model of the circular CFT column with ring-shaped voids under transverse impact, which considers the initial contact status of concrete. After validating the accuracy of FE models, the effects of void ratio, steel ratio, impact speed and mass of the drop hammer on the dynamic behaviour of the circular CFT column with ring-shaped voids are explored. Detailed impacting mechanisms of the defect column are acknowledged by elaborating its dynamic time history curves, failure morphology, impact force diffusion path, contact process, and stress/strain distribution rule. Calculation methods for evaluating the impact resistance of the circular CFT column with ring-shaped voids are proposed. The results declare that the appearance of ring-shaped voids would significantly weaken the impact resistance of the CFT column. The impact force and energy dissipation are greatly decreased with the increase in void ratio. Under the transverse impact, the steel tube would be seriously depressed due to the absence of effective support acted by concrete with ring-shaped void, and the core concrete would be heavily damaged in return.

Safety Evaluation of Crossing Tunnel Engineering: A Case Study

With the growing demand for transportation, there has been a significant increase in road-related projects, leading to potential risks in the safety of existing structures. This paper presents a study on the influence of new tunnel construction on the stability of an adjacent existing tunnel and provides valuable insights for the safety technology evaluation of similar tunnel crossing projects. In order to evaluate the influence of tunnel excavation on adjacent tunnels, the excavation process of a new tunnel near the original tunnel is simulated using the finite element software Midas GTS. This analysis includes the evaluation of static and dynamic responses. The results indicate that the horizontal and vertical displacements caused by the excavation of the railway tunnel are minimal. Furthermore, during the blasting excavation of the railway tunnel, the vibration velocity experienced by the highway tunnel remains below the safe allowable limit. These findings demonstrate that in this project, the influence of blasting excavation for the railway tunnel on the highway tunnel is both safe and manageable.

The footbridge Jesípek – application of radar interferometry for dynamic response evaluation

Recent advances in radar systems have led to the development of radar interferometry (RI) methods for contactless vibration monitoring of large-scale structures, i.e. bridges, water tower reservoirs, and factory chimneys. Interferometric radars are devices capable to measure with 200 Hz sampling frequency and relative movement precision of 0.1 mm up to 0.01 mm. The major part of this paper describes an in-situ footbridge experiment near Hradec Králové. Radar interferometry devices were deployed along with ordinary techniques compounded by accelerometers, wiring, and acquisition station. Experiment was focused on the evaluation of basic dynamic structural properties such as natural frequencies and mode shapes. A lot of attention was also given to the result comparison of these measurement methods. Test results have confirmed the applicability of RI for bridge vibration monitoring.

Vertical dynamics of high-pressure air cushion bearing module: Stability and auto-oscillation

Unstable static equilibrium and vertical auto-oscillations are problems encountered in the application of a high-pressure air cushion module (ACM) for the indoor transportation of heavy loads. The results of two base methods are compared: linear stability analysis based on the linearized equations of the perturbed motion coupled to airflow fluctuations and numerical evaluation of the nonlinear dynamic response of the system. The main distinguishing feature of the analysis is that it comprehensively examines air compressibility in the cushion plenum and in the inlet and outlet flow zones. Accordingly, the study and its findings are valid for high-pressure and low-flow applications of air cushion transportation. A narrow stability region in the parameter domain is identified when the cushion pressure approximates the supply pressure. The peculiarities of the vertical dynamics of the system near stable and unstable static equilibrium positions are described, and influence of viscous damping is considered. The study results contribute to the generalized representation of the stability and vertical dynamics of ACMs and to the theoretical database for ACM design.

Evaluation of static and dynamic responses considering thickness stretching effect for layered composite and sandwich arches using exponential shear and normal deformation theory

Present theory investigates the dimensionless vibration frequencies, deformations, and stresses for multilayered and sandwich arches using exponential shear and normal deformation theory (ESNDT). Present studies consider the effect of [1+(z/R)]radius of curvature while selecting the displacement field of arches under the action of uniform load. It includes the effects of transverse shear (γxz≠0) and transverse normal deformation(εz≠0)i.e., effect of thickness stretching. The governing relations are obtained using the Navier's method, and Hamilton's virtual work principle. The proposed layered arches are completely free from shear correction, and its top and bottom surfaces is satisfies zero traction free end conditions. Present study obtained very accurate natural frequencies for layered sandwich arches than other theories because, available literature not considered the thickness stretching effect i.e.,(εz=0). Hence, the present scientific investigation accounts the effect of thickness stretching i.e.,(εz≠0). However, the non-availability of exact elasticity results of bending and dynamic responses for layered sandwich arches. Present theory is obtained vibration frequencies, displacements, and stresses of layered composite and sandwich arches; the results are compared and validates through prior published literature.

Dynamic response evaluation due to construction system modification of 155 m barge ship using finite element method

The application of lightweight sandwich material as a ship structure was an innovative breakthrough that provided an excellent strength-to-weight ratio. In the sandwich application process, the proposed structural design and scantling must be designed according to the equivalent strength requirement with low weight compared to the existing structure. The research aims to evaluate the dynamic response of different construction systems of barge ships due to applying various hybrid sandwich types in the deck, ship hull, and bottom structures using the current Lloyd’s Register standard. A total of three proposed construction systems: longitudinal, transverse and mixed framing systems, are investigated under different plate configurations, material types, and scantling sizes. The numerical-based finite element approach is used to evaluate dynamic properties of natural frequency and mode shape using free vibration analysis at low mode numbers. The finite element result from the dynamic characteristic and weight reduction estimation between the existing structure and the proposed construction systems under various plate configurations, material types, and scantling sizes is evaluated to determine the application of lightweight sandwich panels in the barge structure.

Experimental study on dynamic response of pile-supported wharf under wave and ship berthing collision

Pile-supported wharf is widely used in deep-water port engineering, which is inevitably subject to joint action of wave and ship berthing collision in marine environment. The evaluation of dynamic response of pile-supported wharf under wave and berthing collision is particularly essential for the design of deep-water port infrastructures. In this study, a wave flume experiment was carried out to investigate the dynamic response of pile-supported wharf embedded in a saturated sand stratum under a given wave and a three-stage pendulum steel ball collision. The pendulum collision was applied at the corner and edge midpoint of the wharf deck, respectively. A variety of representative responses are explored, including time histories of acceleration, displacement, hydrodynamic pressure, pore water pressure, and strain, which characterize the important aspects of dynamic behavior of pile-supported wharf-ground system. Acceleration and displacement of deck as well as acceleration of sand stratum are dominated by the berthing collision; hydrodynamic pressure on piles and pore water pressure of sand stratum are controlled by the wave action; and strain and bending moment on piles are depended on the joint action of wave and collision. It should be noted that dynamic response characteristics of pile-supported wharf will change significantly due to the decreasing of pile effective buried depth near berths induced by the berthing collision energy accumulation. Furthermore, pile group effects including wave scour around piles, collision energy propagation in a sand stratum, and peak bending moment on piles are explored. For comparison, dynamic response of a single pile-ground system and free field are also discussed. Dynamic response of sand stratum around single pile induced by berthing collision on wharf deck is greater than that of free field at the same distance. Experiment techniques and insights from this study may be of significance to the design and maintenance of pile-supported wharves.

On dynamic response and damage evaluation of bridge piers under far-field explosion loads

This paper aims to investigate of the dynamic response and damage mechanism of typical bridge piers under far-field explosions numerically and develop a feasible scheme for rapid damage evaluation of bridge piers. An ANSYS-AUTODYN-based explicit finite element formulation is introduced in which the dynamic input method of blast waves is developed using subroutines. The tests of drop hammer impact and far-field explosion are referenced to verify the reliability of the formulation and the mesh scale applicable to beam-column members is determined. Based on the validated formulation, the refined fluid–solid coupling models of typical single-column and double-column piers are established to explore their far-field blast responses. The effects of input parameters (i.e., the strength and angle of the blast wave,) on the pier response are analyzed. It is demonstrated that bending damage occurs in bridge piers is similar to that of cantilever beam under different strength loads, while the damage of double-column pier members under the constant displacement increases with the increase of the blast wave angle. By incorporating the crack distribution, quantitative assessing criterion and P-I diagram, a damage evaluating scheme is proposed and the damage regularities of piers under far-field blast loads are acquired. The present work can serve as a valuable reference for blast-resistant design and damage assessment of bridge piers under far-field blast loads.

Ponašanje betonskih ploča od cementnog morta pri udarnom opterećenju

As structural members can be subjected to impact loading during their service life, impact experiments are applied for various materials and objects by taking different methods into consideration. The effect of impact load on concrete slabs prepared with cement-based mortars is investigated in this study. A total of nine slab specimens measuring 500 x 500 x 50 mm are tested within the experimental program. Test specimens are prepared to provide different strength values and tested under impact load using the drop test setup. The impact resistance values of the specimens are determined based on the acceleration, impact load and displacement values, as obtained by measurement devices. In addition, crack distribution of the specimens is observed during impact tests. It has been noted that mortar types have a significant effect on the impact behaviour of the specimens. The finite element analysis is generated for each specimen to verify experimental results. Time histories of the acceleration, displacement and impact load values of the selected test specimens are compared. The relationship between experimental and numerical analysis results is presented, which reveals that the finite element procedure can be used in the evaluation of dynamic response of test specimens under the low velocity impact loading.

Dynamic behavior of precast epoxy asphalt track bed for transition zone in high-speed railway: A numerical approach

Elastic cured track bed is gradually used in high-speed railway construction for its high deformation tolerance and stress reduction capacity. Polyurethane and asphalt mixture are the most popular materials used in construction of such track. The usage of polyurethane is restricted by its high cost and constant stiffness at all sections, which causes unwanted deterioration in transition zone. Four kinds of dry-mixed rubberize epoxy asphalt mixture (DREAM) with different stiffness were designed and fabricated into prefabricated asphalt block used as the underlayment of the transition zone of a high-speed railway in this study, aiming to achieve smooth change of stiffness in the transition zone through dynamic response evaluation. To emphasize the feasibility of DREAMs and the special arrangement method proposed in this study, a 3-dimensional transition zone finite element model was established using the finite element software ABAQUS. Dynamic responses related to structure and material working conditions were specially calculated and compared with polyurethane track. The simulation results indicates that the DREAM has better performance under the load of 350 km/h high-speed train compared with polyurethane track. In addition, arrangement method of the four kinds of asphalt block composed of DREAMs was proved efficient in achieving smooth change of stiffness. Compared with polyurethane track, DREAM track has a better stress reduction capacity and plays an important role in protecting the substructure. Besides, structural deterioration of the asphalt mixture is much lower than the recommended value through the results of vertical deflection on the bottom of asphalt block. Finally, the maximum elastic strain and maximum vertical stress on the bottom of asphalt block were specially calculated, and the results indicate that they all meet the recommended values applied to the high-speed railway.

Comparative evaluation of dynamic responses of RCC composite pavement under different moving axles

Roller-compacted composite pavement is considered as an alternative for traditional pavements that provides the desired benefits of both rigid and flexible pavements in a cost-effective manner. To evaluate the performance of roller-compacted concrete (RCC) composite pavement under moving loads, a three-dimensional finite element model (FEM) was developed. A realistic dynamic moving load was applied to the surface of the pavement via DLOAD subroutines developed by FORTRAN. The dynamic response of the pavement at critical locations induced by single, tandem, and tridem axles at speeds of 8 and 80 km/h was determined using the developed FEM model and utilized to estimate pavement performance. Sensitivity analysis of design factors considering variations of hot mix asphalt (HMA) and RCC thicknesses, RCC elastic modulus, axle configurations, and moving speed was conducted to evaluate their impact on fatigue life and rutting development of RCC composite pavement. The results show that the performance of the pavement is significantly affected by axle configurations and moving speed. Among different axle configurations, the tandem axle creates the highest tensile stress and shear stress in the RCC base and HMA layer, respectively. The fatigue life of the pavement prolongs by increasing in the speed of moving loads, so it is expected that the pavement withstands higher load repetition when it is subjected to higher speed traffic. Moreover, increasing layer thicknesses and stiffness of the RCC layer improve fatigue life and rutting performance of the pavement. Even though increasing the thickness of the HMA layer enhances the fatigue life of pavement, increasing it to over 15 cm increases the potential of rutting.

Dynamic Characterisation of a Heritage Structure with Limited Accessibility Using Ambient Vibrations

Historic Cairo has been a UNESCO World Heritage Site since 1979. It has more than 600 historic structures, which require extensive studies to sustain their cultural, religious, and economic values. The main aim of this paper is to undertake dynamic investigation tests for the dome of Fatima Khatun, a historic mausoleum in Historic Cairo dating back to the 13th century and consisting of mainly bricks and stones. The challenge was that the structure was difficult to access, and only a small portion of the top was accessible for the attachment of accelerometers. Current dynamic identification procedures typically adopt methods in which the sensors are arranged at optimal locations and permit direct assessment of the natural frequencies, mode shapes, and damping ratios of a structure. Approaches that allow for the evaluation of dynamic response for structures with limited accessibility are lacking. To this end, in addition to in situ dynamic investigation tests, a numerical model was created based on available architectural, structural, and material documentation to obtain detailed insight into the dominant modes of vibration. The free vibration analysis of the numerical model identified the dynamic properties of the structure using reasonable assumptions on boundary conditions. System identification, which was carried out using in situ dynamic investigation tests and input from modelling, captured three experimental natural frequencies of the structure with their mode shapes and damping ratios. The approach proposed in this study informs and directs structural restoration for the mausoleum and can be used for other heritage structures located in congested historic sites.

Dynamic response evaluation of the Shanghai Tower in along- and across-wind directions during super typhoon Lekima

The dynamic responses of the Shanghai Tower (ST) under Typhoon Lekima in 2019 were evaluated in the along- and across-wind directions based on SHM data. Compared to most similar studies that focus on two main axes of the buildings, this study focused on such dynamic responses in the along- and across-wind directions; these processes were also widely discussed regarding wind tunnel tests. The results of dynamic responses in wind directions were compared to those in the main axes of buildings. The vibration amplitudes in the along- and across-wind directions were closer than those in the two main axes. The relationship between acceleration amplitudes and reduced wind speeds showed a significant effect of the vortex shedding. Additionally, time-varying frequency spectra were used to discuss the modal contribution of the vibration signal. The fundamental frequencies and damping ratios were identified using the SSI method, and correlation analyses were carried out. The relationship between the identified damping ratios and the reduced wind speeds exhibits different aerodynamic effects in the along- and across-wind directions. Comparison of the data showed that dynamic response evaluation in the along- and across-wind directions was more suitable to analyze the wind-resistant performances of super high-rise buildings. All results can aid in understanding the characteristics of these interactions as well as perfect the wind-resistant design of super high-rise buildings.

Dynamic Response Evaluation for Single-Hole Bench Carbon Dioxide Blasting Based on the Novel SSA–VMD–PCC Method

Dynamic Response Evaluation for Single-Hole Bench Carbon Dioxide Blasting Based on the Novel SSA–VMD–PCC Method

A Modified Particle Swarm Optimization Algorithm for Power Sharing and Transient Response Improvement of a Grid-Tied Solar PV Based A.C. Microgrid

The increasing penetration of Distributed Generators (D.G.) into the existing power system has brought some real challenges regarding the transient response of electrical systems. The injection of D.G.s and abrupt load changes may cause massive power, current, and voltage overshoots/undershoots, which consequently affects the equilibrium of the existing power system and deteriorate the performance of the connected electrical appliances. A robust and intelligent control strategy is of utmost importance to cope with these issues and enhance the penetration level of D.G.s into the existing power system. This paper presents a Modified Particle Swarm Optimization (MPSO) algorithm-based intelligent controller for attaining a desired power-sharing ratio between the M.G. and the main grid with an optimal transient response in a grid-tied Microgrid (M.G.) system. The proposed MPSO algorithm includes an additional parameter named best neighbor particles (rbest) in the velocity updating equation to convey additional information to every individual particle about all its neighbor particles, consequently leading to the increased exploration capability of the algorithm. The MPSO algorithm optimizes P.I. parameters for transient and steady-state response improvement of the studied M.G. system. The main dynamic response evaluation parameters are the overshoot and settling time for active and reactive power during the D.G. connection and load change. Furthermore, the performance of the proposed controller is compared with the PI-PSO-based MG controller, which validates the effectiveness of the proposed M.G. control scheme in maintaining the required active and reactive power under different operating conditions with minimum possible overshoot and settling time.