Acceleration Response Research Articles

Field study on vibration characteristics of geocell-reinforced aeolian sand subgrades

Constructing highways in deserts is expensive due to the difficulty of acquiring materials; utilizing aeolian sand effectively has become a problem, especially in the Xinjiang region, where the desert widely occurs. This paper aims to investigate the vibration response of a geocell-reinforced aeolian sand subgrade under traffic loading based on field tests of highways in deserts. The vibration acceleration response of geocell-reinforced aeolian sand and gravelly soil upper roadbed structures is tested. The field test results illustrate the effects of dynamic loading on geocell-reinforced aeolian sand roadbeds, and the thickness substitution ratio between geocell-reinforced aeolian sand roadbeds and conventional gravelly soil roadbeds is determined and verified based on the vibration acceleration monitoring values. The results show that the vibration response induced by the test vehicle is concentrated within the 30 Hz frequency band, and the higher the vibration frequency, the faster the vertical decay in the road. The vibration damping capacity of the reinforced aeolian sand roadbed is better than that of the gravelly soil roadbed; when replacing the gravelly soil roadbed with the reinforced aeolian sand roadbed, the substitution ratio is 0.31–0.42. It is verified that half thickness of gravel soil on roadbeds can be replaced by geocell-reinforced aeolian sand under different working conditions. The results of this study can provide reference data for the design of highway subgrades in deserts.

Comprehensive analysis of a butterfly-shaped piezoelectric shunting vibration absorber for robust vibration reduction and isolation: Theoretical and experimental validation

The Piezoelectric Shunting Vibration Absorber (PSVA) has garnered attention for its effectiveness in vibration control. This paper aims to propose a novel PSVA capable of simultaneously amplitude reduction and vibration isolation under various conditions. The PSVA consists of a butterfly-shaped link component and a piezoelectric stack, connected to the structure to be damped via bolts. Subsequently, an equivalent schematic diagram of the PSVA is established, and its equivalent stiffness is determined. Taking a single-degree-of-freedom structure as an example, considering the dynamic stiffness of the shunting circuit, a dynamic model of the electromechanical coupled system is developed, obtaining the system’s acceleration response and force transmissibility frequency response functions. Following this, experimental equipment is designed and fabricated, and the performance of the PSVA is tested under various excitation conditions. Finally, inspired by the experimental results, a segmented inductance circuit is designed and tested for its capability to broaden the vibration control bandwidth.

Simplified soil–structure interaction modeling techniques for the dynamic assessment of end shield bridges

In this paper, the dynamic behavior of four railway bridges with integrated retaining walls, considering the effect of soil–structure interaction (SSI), is investigated both numerically and experimentally. Among these bridges, two are single-span, and the remaining two are three-span. Each bridge is equipped with numerous accelerometers and is excited by a hydraulic actuator across various frequencies. Full 3D solid Finite Element (FE) models incorporating the railway bridges and surrounding soils are developed and calibrated using the Frequency Response Functions (FRFs) from each accelerometer. Furthermore, simplified 3D solid and 2D beam models are created for each railway bridge, incorporating springs and dashpots to account for the effect of surrounding soils. The values for these springs and dashpots are obtained from simple equations, except for the impact of the backfill soil in the simplified 2D beam models, which are derived from the impedance functions of the soil medium. The performance of these simplified models is then compared to the calibrated 3D models in terms of modal properties of the first bending mode and the maximum acceleration response during high-speed train passages. The results indicate that the simplified models closely align with the calibrated models in terms of modal properties and high-speed train passage response and can be used as simple and efficient alternatives for practical usage in bridge design.

Deep Learning Frequency Loss Functions for Predicting the Seismic Responses of Structures

Novel loss functions for seismic response prediction, such as physics-informed loss functions, have attracted considerable attention. However, existing loss functions are based on the time domain and do not consider the frequency domain differences contained in structure response signals. This study accordingly designed three loss functions based on frequency domain information — one pure frequency domain loss function and two combined frequency- and time-domain loss functions — using Fourier transforms. The proposed loss functions were applied using a trusted publicly available dataset for a frame structure, and their performances were compared with those obtained using the conventional mean squared error (MSE) loss function. The proposed frequency domain loss function exhibited superior performance, accelerating the convergence of learning curves for long-period signals while simultaneously enhancing their frequency domain accuracy and facilitating the prediction of high-sampling-rate response signals. In addition, the designed loss functions exhibited more stable performances and superior accuracy than the MSE when random dataset partitioning was employed. Finally, the combined time- and frequency-domain loss functions were shown to predict the seismic displacement time-history of tall, long-span bridges more accurately than the MSE by training the model to predict structural acceleration responses, then integrating them to predict displacement responses.

Seismic vulnerability and performance-based assessment of monopile offshore wind turbine considering turbine blades

This paper investigated the seismic vulnerability and performance-based assessment of offshore monopile wind turbine (OWT) considering turbine blades. A three-dimensional finite-element model of NREL 5-MW OWT was established with detailed consideration of the nonlinear-behavior of turbine, monopile, blades, pile-soil interactions and pile-water interaction etc. Subsequently, incremental dynamic analysis and fragility evaluation were conducted via a great number of nonlinear time history analysis involving far-field and near-fault records with and without pulse characteristics. It is found that the ignorance of turbine blades in conventional lumped mass (LM) model would significantly underestimate the vulnerability of OWT's acceleration responses, and more importantly, underestimates the stress level at turbine top, misleading the failure pattern of OWT which may be probably damaged at both top and middle part of OWT rather than solely the middle part as estimated by the LM model ignoring the effect of turbine blades. Finally, it can be concluded that the modeling of turbine blades should be consider in the numerical studies.

Survival probability surfaces of hysteretic fractional order structures exposed to non-stationary code-compliant stochastic seismic excitation

A novel first-passage probability stochastic incremental dynamics analysis (SIDA) methodology tailored for hysteretic fractional order structural systems under a fully non-stationary seismic excitation vector consistently designated with contemporary aseismic codes provisions (e.g., Eurocode 8) is developed. Specifically, the vector of the imposed seismic excitations is characterised by evolutionary power spectra that stochastically align with aseismic codes elastic response acceleration spectra, defined for specified modal damping ratios and scaled ground accelerations. Leveraging the concepts of stochastic averaging and statistical linearization, the approximative non-stationary response displacement joint probability density function (PDF) is derived, retaining the particularly coveted attribute of computational efficacy. Subsequently, the coupling with the survival probability model allows for the efficient determination of the response first-passage time probability density surfaces and the survival probability surfaces across various limit-state rules and scalable intensity measures. The first-passage time probability serves as a robust engineering demand parameter, effectively monitoring structural behaviour by considering both intensity and timing information, while inherently aligned with pertinent limit-state requirements. Notably, the associated low computational cost and the ability to handle a wide range of complex nonlinear/hysteretic structural behaviours, coupled with its compliance with modern aseismic codes, underscore its potential for applications in the fields of structural and earthquake engineering. A nonlinear system endowed with fractional derivative elements is used to exemplify the method’s reliability. The accuracy of the proposed method is validated in a Monte Carlo-based context, conducting nonlinear response time–history analyses with an extensive ensemble of accelerograms compatible with Eurocode 8 response acceleration spectra.

Dynamic force identification considering modeling errors using modal expansion method and relevant vector regression algorithm

Accurate identification and estimation of external forces on launch vehicles, aircraft, and other in-service engineering structures plays a vital role in structural design and health monitoring. Considering structural modeling errors, this paper develops a novel force identification method based on modal expansion and relevant vector regression (RVR). Initially, the incomplete and noisy experimental modal data are used to modify the stiffness and mass matrices of the finite element (FE) model, reducing the impact of modeling errors on force identification accuracy. Subsequently, to account for noise disturbances and potential information about unknown initial conditions in the measured acceleration responses, the external forces and the unknown initial conditions are respectively expanded using trigonometric functions and the mode shapes based on the function fitting technique. On this basis, the force identification equation is established for the updated model. The RVR algorithm is integrated into modal expansion and force identification. Firstly, the mode shapes of the FE model are utilized to expand the incomplete and noisy experimental mode shapes to their full degree of freedom, significantly enhancing the accuracy of the model updating. Secondly, by combining the measured acceleration responses, the base coefficients can be solved sparsely, effectively identifying the dynamic forces even when unknown initial conditions are present.

A simplified approach for judging and evaluating the contribution of higher-order modes to the wind-induced acceleration of high-rise buildings

Acceleration is the control parameter for the occupant comfort, often solved in the frequency domain with modal decomposition. In general, the first-order mode response is adopted to represent the total acceleration in practice. However, considering only the first-order mode has been demonstrated to yield underestimated results up to 20 %, while no exact criterion exists to determine whether higher-order modes require to be considered or not. Hence, underlying factors, like the structural natural frequencies, the excitation dominant frequencies, and the distributions of building masses/stiffness, which may significantly affect the contribution of higher-order modes to the acceleration, are analyzed first. Notably, the ratio of the natural frequency of the higher-order mode to that of the first-order mode plays a decisive role in the contribution of the higher-order mode's acceleration. Moreover, the third-order and beyond modes can be largely disregarded. Subsequently, an empirical approach is introduced to determine the need for considering high-order modes. Finally, a simplified formula for estimating acceleration response in the frequency domain is derived to consider second-order modal response. This study provides a method for determining the contribution of higher-order vibration modes to acceleration and a simplified formula to consider the higher-order modal response.

Dynamic performance of a supertall building with an active tuned mass damper system during Super Typhoon Saola

This paper investigates the dynamic characteristics (natural frequencies and damping ratios) of a 600-m-tall supertall building with an active tuned mass damper (ATMD) system during Super Typhoon Saola. Based on the wind speed, wind direction, and wind-induced acceleration response records by the structural health monitoring (SHM) system installed on the skyscraper, the wind characteristics during the passage of Saola are first investigated, and the relations between the mean wind speeds atop the skyscraper and the root-mean-square (RMS) acceleration responses are established. Then, employing the stochastic subspace identification (SSI) method and an uncertainty quantification method, this paper comprehensively investigates the uncertainty bounds, time-varying features, and amplitude-dependency characteristics of the modal parameters with and without the operation of the ATMD system. Next, on the basis of the identified modal parameters and time-frequency analysis, the performance and effectiveness of the ATMD system in suppressing the wind-induced vibrations of the skyscraper is investigated. Lastly, the structural health condition is evaluated from the perspective of building natural frequency and damping ratio changes before and after the typhoon hit. The goal of this study is to advance the understanding of the wind effects on supertall buildings and provide useful information for the wind-resistant design and vibration control of supertall buildings in tropical cyclone-prone regions.

Experimental investigation of wind-induced vibration of multi-cross-section steel tube lightning rods in substation

The multi-cross-section steel tube lightning rod (MSTLR) in the substation are susceptible to along-wind buffeting and vortex-induced vibration due to their inherent flexibility, low damping properties and multi-circular-section. This paper conducted a wind tunnel experiment on a 1:5 aeroelastic model of MSTLR under three wind fields with different turbulence intensity (uniform, 4.0%, and 7.0%). The amplitude, PSD, time-frequency curves, frequency components, and trajectory of wind-induced vibration are analyzed by measuring the acceleration responses at different heights and bottom reaction responses in the along-wind and cross-wind directions. A comparison was made between the relevant wind load parameters and those specified in the Eurocode. The results indicate that the distribution of the key participating modes exhibits different patterns with the variance of wind speed and turbulence intensity. Multi-order vibrations and structural coupling in orthogonal directions are observed with total response higher than the Eurocode. With the increase of turbulence intensity from 4.0% to 7.0%, the contribution of turbulence to along-wind acceleration response reaches saturation and has the opposite effects. When the speeds are 21.55 m/s and 27.33 m/s, respectively, the vortex-shedding frequencies of section 2 and section 3 coincide with the second-order natural frequency, and the vortex-induced resonance occurs. Those two vortex-induced resonances lead to a sudden increase in the standard deviation of the cross-wind response.

Advances in research on the ballast bed stability on railway bridges

The rapid development of high-speed railway bridges in China has brought enormous challenges to the ballast bed stability on the bridge. With the increase in the bridge span, the bridge deformation under the temperature load increases gradually, as well as the stability difference of ballast bed between different regions. Moreover, the track vibration response under high-speed driving conditions is larger, which can easily cause differential settlement, flying ballast, and deterioration of the ballast bed, thereby affecting the bearing capacity and stability of the ballast bed. In view of this, this article summarizes relevant research work on a ballast bed on the bridge from the perspectives of the resistance, deformation, and acceleration response of the ballast bed. In addition, this study discusses the existing measures for improving the ballast bed stability on the bridge, including the optimization of the sleeper and ballast bed structures. Finally, the main issues that need to be addressed to improve the ballast bed stability on the bridge are pointed out, and ideas for future research on ballast beds on bridges with different spans and structures are proposed.

Numerical analysis of seismic response of a circular tunnel-rectangular underpass system in liquefiable soil

Earthquake-induced liquefaction can lead to uplift displacements of underground structures. While the behaviour of a single underground structure has been extensively studied, the coupled response of a shallow buried circular tunnel adjacent to an underpass with a rectangular section in liquefiable ground remains unclear. In this study, the finite difference method based on the fully coupled effective stress is employed to analyse the seismic response of two adjacent underground structures. Firstly, comprehensive parameters of Hostun sand for P2Psand constitutive model was calibrated. The accuracy of the numerical method is verified through a centrifuge test. Subsequently, comparisons are made between the seismic response of the tunnel-soil-underpass interaction and other cases: free field, tunnel, and underpass. The tunnel-soil-underpass interaction in liquefiable ground is analysed, with a special emphasis on the development of excess pore pressure, acceleration response of the soil, displacement and deformation of the structures. A section deformation coefficient was proposed to depict the tunnel deformation. Finally, horizontal spacing, buried depth of tunnel and underpass are discussed to clarify the interaction of two structures. The optimal relative position of two structures is suggested, providing valuable insights for the spatial design of underground structures in liquefiable ground.

Seismic response of the composite bucket foundation supported offshore wind turbines under marine environmental loadings

Many offshore wind turbine (OWT) foundations are situated in earthquake-prone areas, where complex environmental loads intensified the seismic responses of the OWTs. In response to this situation, the composite bucket foundations is proposed and extensively applied due to its reliable installation and high seismic resistance. To analyze the seismic response of composite bucket foundations subjected to environmental loads, refined numerical models of the 6.45 MW OWT system are established, and parametric analyses are conducted, considering the influence of seismic frequency contents and intensities, the soil layer distributions and wind velocities. The results show that the composite bucket foundations undergo cumulative rotational deformation around a point biased toward the windward side of the foundation under the seismic and environmental loads. The increasing mean wind velocity significantly enlarges the displacement response envelope, while has limited influence of the acceleration response envelope of OWTs. Increasing the bucket diameter enhances the deformation resistance of the OWT, while the efficiency of this improvement diminishes as the diameter increases. Greater bucket skirt length also enhances its deformation resistance, but may lead to increased lateral acceleration response of the OWT.

Wind Tunnel Test Research on the Aerodynamic Behavior of Concrete-Filled Double-Skin Steel (CFDST) Wind Turbine Towers

To explore the potential application of concrete-filled double-skin steel tubular (CFDST) structures in wind turbine towers, this study carried out wind tunnel tests to explore the aerodynamic behavior of CFDST tower-based wind turbine systems. Two scaled models including traditional steel tower-based and CFDST tower-based wind turbine systems were designed and tested in the field of typhoons. Then, the vibration characteristics in both the downwind and crosswind directions were systematically investigated, in terms of acceleration and displacement response, motion trajectory, dynamic characteristics, etc. The findings demonstrate that CFDST structures can have significantly improved performance against both blade harmonic excitation and external environmental excitation. Compared to traditional steel towers, CFDST towers exhibit a substantial reduction in aerodynamic response. In particular, the reduction in the RMS value can be over five times in the resonance case and 457.69% in the non-resonance case. The CFDST towers predominantly exhibited converged motion trajectory and concentrated on lower vibration modes. The energy dissipation capability was remarkably enhanced, with the damping ratio increasing up to 40.98%. Overall, it was experimentally demonstrated that CFDST towers can efficiently address the dynamic problems of large-scale wind turbine towers in engineering.

Impact of Train-Induced Vibrations on Residents’ Comfort and Structural Damages in Buildings

AbstractThe rapid growth of urbanization and the progress of industrialization have resulted in the construction of over or near-track buildings. Train-induced ground-borne vibrations have attracted attention because they can damage buildings and cause residents discomfort. This study conducted a series of finite element analyses on three 5-story concrete framed buildings, which were subjected to the passage of trains at various speeds. One of the buildings was modeled as an over-track building, whereas the other two buildings were located in close proximity to the track but at different distances. The present study investigated the impact of train speed and track-to-building distance on the acceleration and velocity responses of buildings. The comparison of residents’ comfort levels and the structural safety of buildings against potential damages was conducted using international standards as the controlling criteria. Furthermore, an efficient mitigation technique was implemented, involving the utilization of open trenches with different depths between buildings and the railway track. This approach was employed with the aim of minimizing the detrimental impacts caused by trains-induced vibrations. The findings indicated that the over-track building was impacted by the train-induced vibrations more than near-track buildings. Furthermore, it was shown that although the passage of high-speed trains can disturb the comfort of building residents and potentially cause some structural damage to buildings, it did not lead to any significant story drifts in the structures. Finally, the minimum required depth of open trenches to mitigate train-induced vibrations was computed for every type of buildings and train speeds.

Sequence Deep Learning for Seismic Ground Response Modeling: 1D-CNN, LSTM, and Transformer Approach

Accurate seismic ground response analysis is crucial for the design and safety of civil infrastructure and establishing effective mitigation measures against seismic risks and hazards. This is a complex process due to the nonlinear soil properties and complicated underground geometries. As a simplified approach, the one-dimensional wave propagation model, which assumes that seismic waves travel vertically through a horizontally layered medium, is widely adopted for its reasonable performance in many practical applications. This study explores the potential of sequence deep learning models, specifically 1D convolutional neural networks (1D-CNNs), long short-term memory (LSTM) networks, and transformers, as an alternative for seismic ground response modeling. Utilizing ground motion data from the Kiban Kyoshin Network (KiK-net), we train these models to predict ground surface acceleration response spectra based on bedrock motions. The performance of the data-driven models is compared with the conventional equivalent-linear analysis model, SHAKE2000. The results demonstrate that the deep learning models outperform the physics-based model across various sites, with the transformer model exhibiting the smallest average prediction error due to its ability to capture long-range dependencies. The 1D-CNN model also shows a promising performance, albeit with occasional higher errors than the other models. All the data-driven models exhibit efficient computation times of less than 0.4 s for estimation. These findings highlight the potential of sequence deep learning approaches for seismic ground response modeling.

Nonlinear Dynamic Analysis of High-Strength Concrete Bridges under Post-Fire Earthquakes Considering Hydrodynamic Effects

This study employed the linear interpolation method to ascertain the curve relationship between the elastic modulus and stress of high-strength concrete C60 with temperature, and the nonlinear dynamic analysis of high-strength concrete bridge structures subjected to post-fire earthquake action at varying water levels was subsequently evaluated. It was established that both the hydrodynamic effects and the temperature effects have a considerable impact on the structural dynamic response of bridges. The presence of water has been observed to increase the dynamic response of pier structures. At water levels of 0 m and 10 m, the temperature effect results in a reduction in the fundamental frequencies of acceleration and displacement responses by 73.68% and a decrease in the fundamental frequency of stress responses by 83.33%. At a water level of 20 m, the fundamental frequencies of the acceleration, displacement, and stress responses decrease by 53.49%. In consideration of the acceleration and displacement at the pier top and stress at the pier base at a water depth of 10 m, the superposition of temperature effects and hydrodynamic effects results in an increase of 59.06% in acceleration, 25.93% in displacement, and 49.53% in stress than combination effects, respectively. At a water depth of 20 m, the superposition of temperature and hydrodynamic effects results in an increase of 92.82%, 100%, and 127.85% in acceleration, displacement, and stress, respectively. The combined effects of hydrodynamic and temperature effects cannot be described merely as a linear superposition of the two single actions. The research findings provide a significant theoretical basis for understanding the impact of multiple disasters, such as fires and earthquakes, on bridge structures.

Concept, optimization and performance evaluation of a novel particle tuned inertial damper (PTID)

Developing more effective vibration control systems is a hot topic in the field of structural vibration control. In the past decades, many types of control systems have been developed, including the well-known particle dampers (PDs). However, the widespread applications of particle dampers are still limited due to some inherent issues: namely large secondary mass and low capacity of energy dissipation in some cases. To address the above issues, a novel particle tuned inertial damper (PTID) is proposed based on the concept of inerter. In particular, the configuration and working mechanism of PTID are first introduced, and a multi-objective optimization framework is formulated by concurrently minimizing both the displacement and acceleration responses. Subsequently, the seismic control effectiveness of PTID is demonstrated by using a single-degree-of-freedom (SDOF) system, and parametric studies are performed to investigate the influences of the preassigned particle mass ratio, inertance-to-mass ratio and amplification factor on the optimal parameters and control performance of PTID. Finally, case studies are performed to further illustrate the control effectiveness of PTID in the seismic protection of a three-story structure. The results demonstrate that, compared to the traditional PD, the proposed PTID could more effectively suppress both the displacement and acceleration responses by utilizing a much smaller particle mass ratio; and increasing the particle mass ratio and amplification factor can enhance the control effectiveness of PTID.

Study on pyroshock response of micro-satellite pyrotechnic cutter

When the micro-satellite panel is deployed in orbit, it needs to be unlocked by the pyrotechnic device. The high-amplitude pyroshock environment generated in the unlocking process is fatal to the sensitive components on the satellite. Therefore, accurate and quantitative analysis of the structural response caused by the explosion can better understood the transmission characteristics of pyroshock, so that effective isolation methods can be carried out. In this paper, the finite element model of the pyrotechnic cutter is established in LS-Dyna, and the explosive unlocking process of the pyrotechnic cutter is simulated by the Particle Blast Method (PBM). The whole motion process of the cutter from unlocking to cutting off the pretightening rod is obtained, the distribution of stress and the propagation law of pyroshock wave are extracted. The results show that before unlocking, the explosion shock is the main part of the pyroshock, while after unlocking, it is mainly caused by the prestress release of the pretightening rod and the impact of the cutter hitting the cutting board. Explosive shock is the main factor affecting the near-field pyroshock, while the far-field pyroshock is mainly affected by the impact. To verify the accuracy of the simulation, a unlock test of pyrotechnic cutter are performed, the acceleration response values of the main reference points are obtained, and the results show that the two results are in good agreement in time domain and frequency domain. Based on the study of the separation characteristics, some suggestions on the optimization of damping buffer are proposed here.

Studi Motion Sickness Incidence (MSI) Pada Kapal Patroli (KAL-28) Katamaran

Motion sickness or seasickness is a condition caused by the movement of a ship that results in dizziness, nausea, and vomiting. The Motion Sickness Incidence (MSI) Study on the Patrol Catamaran (KAL-28) aims to evaluate the comfort level of passengers and the safety of the ship's crew during operations, following the ISO 2631/1997 standards. The evaluation is conducted on the vertical acceleration response of the ship under various wave conditions, speeds, and wave directions. Mapping is performed in various areas of the ship, including the deck, navigation room, and engine room, considering wave heights of 0.875 meters and 2 meters at speeds of 15 knots, 22.5 knots, and 30 knots. The research results indicate that at a speed of 15 knots, the deck area, navigation room, and engine room meet the criteria from comfortable to somewhat uncomfortable. However, at speeds of 22.5 knots and 30 knots, these areas are rated as somewhat uncomfortable to very uncomfortable. This study emphasizes the need for ship design that considers both passenger comfort and safety, especially for patrol catamarans