Dynamic Response Of Structure Research Articles

H2 Optimization of a New Type of Tuned Lever Inerter-like Mass Damper (TLIMD) for Attenuating Structure Vibrations

The lever or the lever-type mechanism can achieve an inertia amplification effect by appropriately calibrating its structural configuration, and it is also proven to be one of the most cost-effective solution for the inerter realization compared with other mechanical devices. Benefitting from this property, the present paper adopted a new type of tuned lever inerter-like mass damper (TLIMD) for attenuating stochastic load-induced structure dynamic responses. A set of closed-form formulae for the TLIMD optimal parameters are developed by the use of H2 norm optimization criterion, wherein the structure’s inherent damping is explicitly accounted for. It is theoretically demonstrated that the TLIMD optimal parameters are mainly dominated by three critical parameters, i.e., the damper mass ratio, the lever length ratio (known as the inertia amplification ratio) and also the host structural damping. The proposed formulae for the TLIMD optimization are validated through the seismic analysis, where two classic inerter-based dampers (i.e., the tuned mass damper inerter (TMDI) and the tuned inerter damper (TID)) optimized by the numerical technique are included in the discussion. It is found that the TLIMD has a superior advantage in reducing the structure responses and also exhibits stronger robustness for the detuning condition than the classic inerter-based dampers. Furthermore, the increase in the damper mass ratio and the lever length ratio can be beneficial for enhancing its performance.

Dynamic responses of monopile offshore wind turbines under different wind-wave misalignment angles

Wind-wave misalignment is a common occurrence for monopile offshore wind turbines during extreme typhoon conditions. This phenomenon has a significant impact on the structural dynamic response of turbine structures and poses a threat to their structural integrity. In this study, finite element analysis is conducted on 75 sets of working conditions of monopile offshore wind turbines to investigate their dynamic response under different wind turbine operating states, wind-wave misalignment angles, and randomness of wind and wave load conditions. The results of the analysis indicate that the impact of wind-wave misalignment angles on the dynamic response of the monopile offshore wind turbine varies depending on the operational conditions. Furthermore, the study reveals that there are variations in the dynamic response of the monopile offshore wind turbine under different combinations of wind and wave loads. During the parked state and yaw system fault of the monopile offshore wind turbine, the most adverse working conditions need to consider wind-wave misalignment angles of 0° and 180°. In contrast, the most adverse working conditions for operational states emerge when the wind-wave misalignment angle is 90°. These findings highlight the importance of considering wind-wave misalignment angles and the randomness of wind and wave load conditions when assessing the dynamic response and structural integrity of monopile offshore wind turbines.

Experimental investigation of the relation between operating conditions and offshore wind turbine drivetrain dynamics

Abstract This study investigates the impact of operating and environmental conditions on the vibration induced on an offshore wind turbine drivetrain. Furthermore, it explores the role of the dynamic response of the global wind turbine structure to vibration on the drivetrain. A prolonged experimental campaign dedicated to condition monitoring the drivetrain provides experimental vibration signals. These vibration signals are acquired under varying operating conditions across multiple locations of an offshore wind turbine drivetrain of a Belgian Offshore Wind farm and serve as the basis for analysis. The signals’ statistics facilitate establishing connections between dynamic behaviour and operational variables, such as active power, rotor speed, blade pitch angle, and turbulence intensity, sampled at every second and provided by Fast-SCADA. The initial phase of the analysis involves a comprehensive examination of various statistical properties of the vibration signals to link the drivetrain’s dynamic response to operational conditions. This exploration includes both active and standstill periods of the wind turbine. A comprehensive summary that relates the global vibration characteristics with the operating conditions is formed by scrutinizing the overall vibration signals. In the study’s second phase, a detailed investigation is conducted on the vibration signals recorded during standstill conditions. Investigation of standstill data ensures that the structural modes’ spectral content does not interfere with the machines’ kinematic content. The analysis of standstill data proceeds from determining the most energetic resonance frequencies through the average power spectral density of the vibration signals. These identified frequency bands enable a thorough exploration, revealing the interlink between the offshore wind turbine drivetrain’s dynamic response and the operating/environmental conditions.

Dynamic Responses and Damage of a Model Ship in Multi-Rock Grounding

Ship grounding onto multiple rocks is one of the scenarios where a ship may suffer severe hull damage, thus leading to some serious consequences, such as casualties, oil spill pollution, and property damage. Ship bottom raking is the most common and severe damage type in grounding caused by sharp rocks moving against the bottom plate. This paper investigates the dynamic responses of ship grounding onto multiple sharp rocks, which has rarely been studied in the literature. Nine ship grounding in-tank model tests were conducted to provide experimental data for ship grounding onto a single rock or multiple rocks. A simplified scaled ship model with replaceable bottom plating was designed and used in the model test. Some artificial cone rock models with a 1 mm tip radius and a 15° semi-apex angle were assumed. The damage modes of the bottom plating and motions during ship grounding onto multiple rocks were obtained and recorded in the model tests, as well as the longitudinal grounding resistances. The effects of the initial relative height of each rock and the size of rock distribution on the structural damage mode and dynamic response of a ship model in multi-rock ship grounding were investigated. In addition, the results obtained from single-rock and multi-rock ship grounding model tests are compared.

Shaking table test and numerical simulation of rocking wall frame structure considering dynamic soil-structure interaction

This study investigates the seismic response of a rocking wall frame structure considering dynamic soil-structure interaction (DSSI) through shaking table tests. A comparison with conventional frame structures and structures with fixed-base foundations is made to examine the influence of DSSI effects on various aspects including structural damage distribution, dynamic characteristics, and floor responses. Test results indicate that the presence of a rocking wall reduces structural responses across different site conditions, although the reduction is less significant under soft soil conditions compared to fixed-base foundation conditions. Overall, DSSI diminishes the mitigating effect of the rocking wall on the maximum structural response. Furthermore, a three-dimensional finite element model of the shaking table test is established. The numerical model employs the equivalent linear method to simulate the soil's nonlinear behavior and incorporates the concept of the rocking wall. Comparative analysis between experimental and simulated results demonstrates that the model effectively predicts the dynamic response of the rocking wall frame structure in DSSI systems.

Life Prediction and Reliability Evaluation of Reinforced Concrete Frame Structures Considering the Collision Response Under Earthquake Conditions

Firstly, in this study, we utilize the high-order element model (truss link model) simulation method in OpenSees (3.7.0) software and verify the feasibility of this method by comparing it with the shaking table test. Secondly, the structural dynamic response of adjacent structures with different performance levels, spacing, and layout forms under large earthquakes is analyzed, and the corresponding structural failure probability is studied. Furthermore, the life distribution within the design service life of the structure is predicted according to the nonparametric Kaplan–Meier estimation model. Finally, the reliability of adjacent structures is evaluated by using the joint engineering demand parameters. The analysis method of replacing the theoretical analysis based on engineering experience and certainty in the current specification with probability analysis is proposed, which provides a more reliable theoretical basis for decision-making regarding the reinforcement, maintenance, or demolition of structures in the later stage.

Full wavefield modeling and dispersion characteristics of underwater MASW

The underwater multichannel analysis of surface wave (UMASW) is becoming an essential tool for surveying subbottom shear wave velocity. Current practice is limited to interpretation based on the fundamental mode. This paper investigates the full dynamic response of the underwater-multilayered structure under two different types of sources (impact and explosion). Fundamental solutions in the transformed domain, after applying both Fourier transform and Fourier–Bessel transform, are derived utilizing the global stiffness matrix method, analogous to a 1-D finite element approach. Solutions in the physical domain are then obtained using the fast and accurate Fourier series and Fourier–Bessel series approach proposed in this paper. The most attractive feature of this novel approach is that the expansion coefficients (or Love numbers) can be pre-calculated, saved, and repeatedly used for other field points. Through numerical analyses, we quantitatively investigate the effect of the water depth and source/receiver types/locations on different wave features (i.e., Scholte, fast-guided, and acoustic modes) from different perspectives (i.e., dispersion curve, Green’s function, frequency-velocity spectrum (FVS), and waveform). We find that (1) unlike the impact source, stronger acoustic waves can be produced by the explosive source, which sometimes causes difficulty in identifying the Scholte waves. (2) The acoustic and interface-guided waves exhibit distinct behaviors depending on the source and receiver locations. Scholte waves and fast-guided waves are weakened when the source and receivers are elevated far from the water/soil interface. Moreover, (3) the response of the Scholte wave can be enhanced by muting the direct acoustic waves. However, (4) the fast-guided wave may also arise in underwater surveys when the Vs of the underlying half-space is much higher than those of the upper layers, exerting a significant influence on the shallow water scenarios and posing challenges for correct mode identification. With the ability to model the entire wavefield (or FVS) that takes into account all propagation modes and the actual survey configuration, inversion can be performed by fitting the entire FVS. This approach eliminates the need to pick dispersion curves and provides a more accurate and stronger model constraint.

A new semi-analytical approach for nonlinear dynamic responses of functionally graded porous graphene platelet-reinforced circular plates and spherical shells

This paper presents the semi-analytical approach for nonlinear dynamic responses of porous graphene platelet-reinforced circular plates (CiPs) and spherical shells (SpSs) resting on the Pasternak foundation in thermal environment. The graphene platelets (GPLs) are distributed in the functionally graded (FG) distribution patterns and uniform distribution pattern through the CiP and SpS thickness direction. The governing equations of the GPL-reinforced structures subjected to time-dependent external pressure respected to the harmonic and linear functions of time are established based on the geometrically nonlinear higher-order shear deformation theory. A simple and effective semi-analytical solution for the considered problem is established using the Euler-Lagrange equations, and the damping viscosity of the foundation can be counted using the Rayleigh dispassion function. The Runge-Kutta method is employed to determine the dynamic responses of the GPL-reinforced structures, while the fundamental frequencies of free and linear vibration, and frequency-amplitude curves are obtained in explicit form. The numerical results obtained reveal that the GPL and porous distributions, geometrical and material properties can significantly affect the frequency-amplitude curves, and dynamic responses of harmonically loaded and linearly loaded structures, specially, the dynamic buckling phenomenon is clearly observable with the SpSs but not with the CiPs.

Performance-based seismic design of controlled rocking reinforced concrete frame with beam-end hinge

This study investigates the seismic performance of the Controlled Rocking Reinforced Concrete Frame with Beam-end Hinge (CR-RCFB) system. The novelty of our research lies in the development and validation of a finite element model that accurately predicts the dynamic response of CR-RCFB structures under various seismic conditions, specifically focusing on the innovative use of joint stiffness ratios and the integration of dampers. A finite element model was developed and validated through shaking table tests. The research examined the dynamic responses of the CR-RCFB under ten ground motion records, varying the node relative stiffness ratios. The interstory displacement amplification coefficient (α) was found to range between 1.08 and 1.20, while the earthquake-reduction coefficient (β) varied from 0.8 to 0.3 depending on the stiffness ratio. Results indicate that node stiffness ratios between 0.01 and 0.25 optimize performance, minimizing peak interstory displacement and base shear response. Additionally, integrating dampers increased the damping ratio from 14.48% to 30.51%, enhancing energy dissipation by shifting absorption from plastic deformation to damper yield. Pushover analysis was used to recalculate and validate the parameters α and β, demonstrating that the integration of dampers effectively controls displacement response. These findings suggest that the CR-RCFB system with integrated dampers offers enhanced seismic resilience by reducing displacement and base shear forces compared to traditional reinforced concrete frames.

The wave-current combined effect on the dynamic response of monopile-supported system considering fluid-structure interactions

ABSTRACT The monopile-supported offshore wind turbines (OWTs) are subjected to complex marine environment loads, the dynamic responses of wind turbine structures under wave and current loads are critical for structural safety assessment, which involves the interaction of fluid and structure fields. This study proposed an approach for simulating the two-way (T-W) fluid-structure interaction (FSI), the dynamic responses of the wind turbine support structure under the combined action of wave and current load are investigated. Subsequently, the effect of wave-current interaction, scour depth and flow velocity on the dynamic responses of monopile-supported OWTs are analysed and some useful guidelines are provided. The results indicate that the wave-current interaction can strongly influence the dynamic responses of OWTs, especially for larger scour depth and higher flow velocity. In addition, the displacement amplitude of OWT decreases by 15% under the current load in consideration of the fluid-structure interaction and the bearing performance of the pile improves accordingly.

Dynamic performance of a 5-story full-scale prestressed precast space frame structure under edge and corner column failure scenarios

Progressive collapse resistance is more critical for precast concrete than cast-in-place structures. Most existing studies utilized scaled-down and quasi-static pushdown tests on substructures with rigid constraints under key member failure scenarios. However, the connection details, the spatial action of floors and the constraint stiffness of the remaining structure significantly affect the structure's progressive collapse resistance. Full-scale structural testing is the most direct method to evaluate the progressive collapse resistance of a new prefabricated structure, although it is difficult and costly to load and measure. A 2 × 2 bay 5-story full-scale frame structure was constructed according to the minimum requirements of the Code for Seismic Design of Buildings to investigate the progressive collapse resistance of a new precast, prestressed, efficiently fabricated frame (PPEFF) system. The structure's dynamic performance was analyzed by removing the 4th-floor edge column and bottom corner column. The slider and double micro-friction surface configuration proved suitable for the rapid removal of large axial force columns in a full-scale progressive collapse experiment. The layout of the full-scale structural test and the structure's dynamic responses are described. The effect of the lateral constraint stiffness and the duration of column removal on the dynamic response of the test structure were analyzed using finite element analysis. The progressive collapse resistance mechanism of the PPEFF structure was discussed. The PPEFF system remained in an elastic state and exhibited good progressive collapse resistance.

Dynamic Response Prediction Model for Jack-Up Platform Pile Legs Based on Random Forest Algorithm

Jack-up offshore platforms are widely used in many fields, and it is of great importance to quickly and accurately predict the dynamic response of platform pile leg structures in real time. The current analytical techniques are founded upon numerical modelling of the platform structure. Although these methods can be used to accurately analyze the dynamic response of the platform, they require a large quantity of computational resources and cannot meet the requirements of real-time prediction. A predictive model for the dynamic response of the pile leg of a jack-up platform based on the random forest algorithm is proposed. Firstly, a pile leg dynamic response database is established based on high-fidelity numerical model simulation calculations. The data are subjected to cleaning and dimensional reduction in order to facilitate the training of the random forest model. Cross-checking and Bayesian optimization algorithms are used for the selection of random forest parameters. The results show that the prediction model is capable of outputting response results for new environmental load inputs within a few milliseconds, and the prediction results remain highly accurate and perform well at extreme values.

Dynamic response of hemispherical-shell sandwich structures subjected to underwater impulsive loading

In this study, experiments and numerical simulations are designed on aluminum sandwich structures with a hemispherical-shell core layer under underwater impact loading to investigate the dynamic response and energy absorption mechanisms. After the hemispherical-shell sandwich panels are designed and fabricated, they are loaded using an experimental apparatus incorporating fluid–structure interactions. The dynamic response of the sandwich panels is captured using the three-dimensional digital image correlation (3D-DIC) method of high-speed photography, and the energy-absorption mechanisms are analyzed via numerical simulation. This study primarily considers the effects of installation orientation, shock wave impulse and adhesive film on the sandwich panels. The results indicate that the deformation mode and impact resistance of the sandwich panels vary depending on the installation orientation. The displacement at the midpoint of the dry facesheet is linearly related to the shock wave impulse. At non-dimensional impulses exceeding 0.0085, the impact resistance of the forward installation target plate is higher. Additionally, the adhesive film significantly affects the deformation mode of the hemispherical-shell core layer. Its removal slightly increases the proportion of energy absorbed at the core. Quantitative and qualitative analyses of the structure-response-energy relationship are performed on the hemispherical-shell sandwich panels, thus providing guidance for investigations pertaining to the underwater impact resistance of future metal sandwich structures.

Investigation on typhoon-induced aero-elastic response of membrane structures by wind tunnel test and numerical simulation

Extreme winds, such as typhoons, can lead to serious vibration and damage for flexible membrane roofs. An understanding of the aeroelastic behavior experienced by membrane structures during typhoons is therefore significant to allow well designed in practice. This paper investigates the aeroelastic response of umbrella shaped membrane structures under typhoon experimentally and numerically. The flexible scaled model is tested in typhoon field simulated in wind tunnel to investigate the aeroelastic characteristics varying with wind velocities and wind directions, including displacement response, non-Gaussian characteristics, frequency, modal shape and damping ratios et al. The full coupled fluid-structure interaction numerical model proposed is benchmarked and expanded in parameter discussions. The results indicate that non-Gaussian characteristics appear significant with positive skewness in pressure region and negative skewness in suction region. The probabilistic distribution proves leptokurtic type with kurtosis beyond three. The displacement response in statistics increases almost linearly with wind velocity while the non-Gaussian characteristics remain robust. The high-order mode shapes can be excited in typhoon, and their frequencies and damping ratios vary with wind velocities. The effects of both wind velocity and membrane pretension are proved to be more remarkable than rise-span ratio. This study can address the deficiency of current studies and provisions on the dynamic response of membrane structures in typhoons.

Seismic Response of Foundation Settlement for Liquid Storage Structure in Collapsible Loess Areas

To investigate the impact of foundation settlement in loess areas on the dynamic response of liquid storage structure (LSS) under seismic motion, a finite element analysis model of the liquid–solid coupling of LSS was established using ADINA V9.6 software. By analyzing the dynamic response patterns of LSS under seismic motion with foundation failure, this study examines the effects of foundation failure and the direction of seismic wave incidence on the equivalent stress, maximum shear stress, wall displacement, and liquid sloshing wave height of the structure. The results indicate that among the three foundation failure scenarios, foundation failure at the center of the tank bottom has the least impact on the structural dynamic response. In contrast, foundation failure affecting one-fourth of the tank base has the greatest impact. Furthermore, compared to seismic motion along the X-axis, the dynamic response of the structure is more significantly affected when seismic motion co-occurs along the X-Z-axis.

Computing the dynamic response of a periodic structure coupled with a nonlinear junction using the harmonic balance method and Floquet-Bloch modelling

Structures constituted of assembled sub-components are often subject to nonlinear effects due to the presence of joints or contacts, which can induce higher-order harmonics of the source excitation. In the context of periodic structures, these nonlinearities cannot be tackled using the Floquet-Bloch theory in its usual harmonic formulation. This study hence presents an adaptation of the classical Floquet-Bloch theory to address multi-harmonic systems arising from a finite number of localized nonlinearities in periodic waveguides. We adopt the Harmonic Balance Method to recast the governing equations into a nonlinear algebraic system, which can then be solved using numerical continuation algorithms. To demonstrate the validity and benefit of this approach, the predictions derived from the proposed methodology are compared to results obtained through conventional Finite Element analysis. Excellent agreement and a notable reduction in computational cost are observed. This efficient procedure for analysing the nonlinear dynamic response of periodic waveguides opens up new possibilities in the study of damaged composite structures.

Dynamic response and vibration suitability analysis of the large-span double-connected structure under coupled wind and pedestrian loads

Modern buildings increasingly utilize lightweight, high-strength materials and feature high-rise, large-span structural designs. These structures often exhibit low natural frequencies and are susceptible to resonance from low-frequency dynamic loads such as wind and pedestrian loads. This paper focuses on a large-span double-connected structure and analyzes its dynamic response under the combined effects of wind and pedestrian loads. First, a finite element model of the structure was created using ANSYS, and model validity verification and modal analysis were performed. Second, a Fourier-based pedestrian model was used to simulate pedestrian loads and generate time-range data. The pulsating wind speed was generated from the Davenport spectrum using the harmonic superposition method. Wind load time-range data were calculated for different heights using Bernoulli’s theorem. Finally, the solution yields information about the dynamic response of the structure. The study revealed maximum vertical comfort ratings in the connecting corridor were achieved when crowd density did not exceed 0.3 persons/m2. The connecting corridor’s most unfavorable horizontal comfort level was evaluated as a medium, except for the 0-degree wind angle condition. This paper provides experience in studying the dynamic response and vibration suitability assessment of the large-span double-connected structure under wind and pedestrian loads.

Numerical Simulation of a Shed-Tunnel Structure’s Dynamic Response to Repeated Rockfall Impacts Using the Finite Element–Smoothed Particle Hydrodynamics Method

In practical engineering, a shed-tunnel structure often encounters repeated impacts from rockfall during its whole service life; therefore, this research focuses on exploring the dynamic response characteristics of shed-tunnel structures under repeated impacts from rockfall with a numerical method. First of all, based on a model test of a shed tunnel under rockfall impacts as a reference, an FEM (finite element method)-SPH (Smoothed Particle Hydrodynamics) coupled numerical calculation model is established based on the ANSYS/LS-DYNA finite element code. Numerical simulation of the dynamic response of the shed-tunnel structure under rockfall impacts is realized, and the rationality of the model is verified. Then, with this model and the full restart technology of the LS-DYNA code, the effects of four factors, e.g., rockfall mass, rockfall impact velocity, rockfall impact angle and rockfall shape, on the impact force and impact depth of the buffer layer, the maximum plastic strain and axial force of the rebar, the shed roof’s vertical displacement and plastic strain of the shed tunnel are studied. The results show that the impact force, impact depth, roof displacement and plastic strain of the shed tunnel are positively correlated with the rockfall mass, velocity and angle under multiple rockfall impacts. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the impact of rockfall consisting of cuboids are all greater than those under spherical rockfall, and the impact depth generated by the impact of spherical rockfall is greater than that of rockfall consisting of cuboids. For rockfall consisting of cuboids, the impact depth, roof displacement and plastic strain are negatively correlated with the contact area. Under repeated rockfall impacts, the peak impact force usually increases first and then tends to be stable.

Research on the response of underwater explosion liquid tank structure based on RKPM method

Abstract This work establishes a three-dimensional fluid-structure coupling calculation model for the response of SPH-RKPM underwater explosion structures and verifies its effectiveness. Using the established numerical model, the dynamic response of the water-containing liquid tank structure under underwater explosion shock wave load was modeled and calculated, and the response characteristics of the water-containing liquid tank under different detonation distances were discussed. The response law of the water-containing liquid tank structure under shock wave load is summarized.

Research on the response of underwater explosion side structure based on RKPM method

Abstract Based on smoothed particle hydrodynamics and reproducing kernel particle method, this paper establishes a fluid-structure interaction three-dimensional calculation model for the dynamic response of complex structures to underwater explosion shockwave, verifies the effectiveness, accuracy and progressiveness of SPH-RKPM coupling calculation, and establishes a control condition with detonation distance as a variable to determine the dynamic response characteristics of ship side under shockwave loads generated by underwater explosion at different detonation distances.