Dynamic Displacement Response Research Articles

Experimental and numerical analysis of seismic performance of jacket platforms subjected to onshore and offshore earthquakes

Offshore platforms located in seismically active areas may be subjected to different seismic effects during service. The seismic performance of offshore platforms under different earthquakes was studied using shaking table tests and finite element analysis (FEA). The dynamic properties, acceleration, displacement and strain responses of the scale model under near-field, far-field and offshore earthquakes were studied. On this basis, more consideration was given to soil-pile-structure interactions (SPSIs), and this finite element (FE) model was analyzed for seismic fragility using incremental dynamic analysis (IDA). By combining the results of the tests and FEA, it was found that the dynamic response of the platform was significantly larger under offshore earthquakes than under onshore earthquakes. The collapse resistance of offshore platform under offshore earthquakes was inferior to that under onshore earthquakes. Therefore, seismic performance assessment of long-period offshore platforms based on onshore earthquakes may overestimate its seismic capacity and pose potential risks to platforms in service.

Intelligent identification of moving forces based on visual perception

The task of identifying moving forces presents a challenging inverse problem for bridge health monitoring and condition assessment. Existing methods for identifying moving loads rely on complex structural response measurement equipment, resulting in inefficiency and elevated costs. To address these challenges, this study introduces an innovative intelligent identification method for moving forces on bridges using visual perception techniques. The proposed method utilizes cameras to capture displacement changes at specific points on the bridge surface to reconstruct moving forces in the time domain. Initially, numerical simulations were conducted to ascertain the feasibility and robustness of identifying moving forces based solely on the structural displacement response. This phase also investigates the influence of different measurement point combinations on identification accuracy. Subsequently, the accuracy of the proposed method in measuring the dynamic displacement response of the structure was carefully evaluated by an outdoor shaking table test. Furthermore, a meticulously designed simply supported beam model was fabricated, followed by the execution of precise vehicle-bridge coupling dynamic experiments. This phase rigorously validates the effectiveness and accuracy of the proposed moving force identification method at varying vehicle speeds. The obtained results substantiate the proposed approach's capability not only to comprehensively capture bridge response data for full-area monitoring but also to consistently and reliably identify information on moving vehicle forces. This study underscores a pioneering application of intelligent visual perception technology in the field of identifying moving forces. The introduced noncontact intelligent identification method is an effective solution for monitoring moving forces on bridges, which has a wide range of applications in the future.

CNN-based model updating for structures by direct use of dynamic structural response measurements

This study presents a convolutional neural network (CNN)-based model updating method for structures using dynamic structural responses. In the presented method, the dynamic structural response is used directly for model updating, thereby omitting the manual process of extracting modal parameters. In the method, the type of stiffness variable in the target structure for model updating is selected, and a number of candidate models are generated by multiple selected stiffness variables in the structures and possible values of variables. Dynamic structural responses are then extracted by time history structural analysis of the candidate models, and a CNN sets dynamic structural response as input, and information on stiffness variables as output is introduced to learn the relationship between the two data. CNNs trained using dynamic displacement response and dynamic acceleration response are presented as Model_XT and Model_XTa, respectively. The presented models can rapidly estimate stiffness of the target structure by entering dynamic responses into the models. These models are applied to model updating for three example structures, and the stiffness estimation performance for model updating is evaluated. Furthermore, the length of data used for CNN training, the stiffness estimation performance according to the CNN input layer settings, and the stiffness estimation applied with limited data to the updated model are analyzed.

Numerical Simulation Study of the Vibrational Response of Continuous Arch Tunnels under the Action of Overlying Train Loads

With the rapid development of transportation infrastructure in China, continuous arch tunnels passing under existing operational railways are increasingly encountered. This paper primarily investigates the mechanical response patterns of the lining of continuous arch tunnels under the vibrational loads generated by trains traveling on railways. To this end, a three-dimensional finite element model of the dynamic response of continuous arch tunnels under train vibrational loads was constructed using Midas GTS/NX software. This model explores the patterns of acceleration, dynamic displacement, and dynamic strain responses of continuous arch tunnels under the action of moving train loads. The study reveals that under train vibrational loads, the vertical acceleration, vertical displacement, and strain time history curves at various monitoring points in the continuous arch tunnel exhibit vibrational characteristics. The acceleration, vertical displacement, and dynamic strain increase as the train enters, fluctuate within a certain range, and then decrease to zero as the train exits. Under high-speed train loads, the acceleration peak values at the arch feet and outer sidewalls of the left and right tunnels are larger, with a greater peak value difference. The vertical displacement peak values at the arch shoulders and crown are larger, whereas those at the middle partition wall and base slab are smaller. During the process from the train's entry to its exit, the dynamic strain exhibits a trend of initially increasing, then stabilizing, and finally decreasing to zero, all while displaying vibrational characteristics. The strain response on the tunnel side where the train enters is greater than that on the side where it exits.

Seismic performance of a frame‐supported shear wall over‐track building through shaking table test

SummaryThis research deals with a frame‐supported shear wall for urban over‐track building of vehicle depot in Chisha, Guangzhou, China, which is characterized by its remarkable height of 160.8 m. Technical issues are commonly encountered in these kinds of buildings due to discontinuous vertical structural rigidity, large podium, and structural transition. These challenges significantly impact the engineering process, especially when the rigidity difference between transfer story exceeding the threefold, as well as the building height exceeds limit as in code. In this paper, a shaking table test was developed based on a 1:10 scaled model of the structure. Using similarity theory, the dynamic similarity relationship was established for the design of the model. Subsequently, the experimental model was constructed with the configuration of critical parameters such as mass design, sensor placement, and seismic test conditions. This was followed by in‐depth analysis, recording component failures and investigating key aspects such as dynamic characteristics, that is, acceleration and displacement responses and shear force distribution under different earthquake intensities. A theoretical seismic response of the prototype structure was derived from the test results. The shaking table tests confirmed that the structure met the stringent seismic design requirements as prescribed in the Chinese standards, with no damage under minor earthquakes, repairability under moderate earthquakes, and collapse prevention under rare earthquakes. The results of the study provide valuable insights along with improvement measures for the design and development of similar urban over‐track buildings, potentially contributing to more efficient land use in urban China.

Reliability-based design optimization scheme of isolation capacity of nonlinear vibration isolators

Nonlinear vibration isolators (NVIs) are beneficial to isolate or suppress the adverse effects caused by harmful vibration. To a large extent, the isolation capacity of NVIs depends on the selection of design parameters (including structural, geometric, and excitation parameters) of vibration isolators. However, existent uncertainties of these parameters are unavoidable, which influence the reliability of the isolation capacity of NVIs. In this respect, an effective reliability-based design optimization (RBDO) scheme of isolation capacity of NVIs is presented by taking into account the parameter uncertainties of NVIs. In the proposed RBDO scheme, the force transmissibility of nonlinear isolators is regarded as the objective function, and the fundamental frequency, the dynamic displacement response amplitude, and reliability of vibration isolation performance are supplied as the constraints to search the optimal design parameters of NVIs. Considering the influence degree of design parameters uncertainties, the global reliability sensitivity analysis is employed for identifying the critical design parameters in NVIs. A surrogate model of the failure probability function is established by the adaptive learning Kriging approach to decrease the computational cost of the reliability evaluation nested in the RBDO scheme. An advanced meta-heuristic algorithm is executed to search for the design parameters for optimal isolation capacity of NVIs. The proposed scheme provides a potential direction for optimizing the isolation capacity of complicated vibration isolators.

Parallel transient response topology optimization based on PETSc

Improving the dynamic properties and reducing the vibration levels is extremely important for the design of many engineering structures. In this paper, we develop a dynamic topology optimization program based on parallel computing with the help of the PETSc Portable Extension Toolkit for Scientific Computing and the MPI communication protocol. The SIMP model is used as the topology optimization model, and the sensitivity analysis schemes of the dynamic compliance and displacement response as opposed to the density design variables are given in the paper. Using this optimization formulation, we developed a parallel topology optimization program for minimizing the transient response. The convergence performance of the program is shown with a relatively large-scale numerical example.

Effect of debonding damage on transient dynamic response on stern ramp door of passenger ship 6311 GT

The sandwich, as an advanced material, increases innovation in the field of ship construction. One of the applications is on the ramp door structure. The characteristics of sandwich material which are light and strong, are the main reasons for the application of this material. However, sandwich material also has drawbacks, one of which is debonding damage, where the bond between the face and core is released. This damage can affect the structure’s stiffness, which impacts reducing the strength of the structure on the ramp door. The effect of debonding is identified by performing numerical tests using finite element software. This test aims to identify the ramp door’s dynamic response due to the debonding damage’s influence. This research uses finite element software with an explicit dynamics method to determine the dynamic response of stress and displacement due to loading on the ramp door. The results of testing with finite element software show that an increase in the ratio of debonding damage causes the amplitude of the dynamic response to increase when subjected to transient loading.

Numerical Study on the Evolution Law of Explosion Response of Extra-wide Self-anchored Suspension Bridge under the Influence of Concrete Shrinkage and Creep

In order to deeply reveal the evolution law of explosion response of super wide self anchored suspension bridge under the influence of concrete shrinkage and creep, the evolution law of explosion response of extra-wide self-anchored suspension bridge under the influence of concrete shrinkage and creep is studied by simulation experiment. Based on a real bridge, the dynamic response of vertical displacement of the bottom plate of the bridge under explosion load at different ages is analyzed by numerical simulation. Firstly, the refined finite element model of the whole bridge is established by using SolidWorks software and Hypermesh software; Secondly, the explosion load is applied by ANSYS/LS-DYNA software and *LOAD_BLAST_ENHANCED (LBE) method, and the reliability of the calculation method is verified by combining the explosion test results of concrete members in the literature; Finally, the dynamic response of the bridge at different ages is analyzed by modifying the elastic modulus of the material to make the main girder reach the linearity predicted in the literature. The results show that under the action of explosion shock wave, the stress of the concrete element on the top plate of the main girder reaches the limit value and fails, forming an elliptical breach. With the increase of the age of the bridge, the vertical displacement of the bottom plate in the middle of the bridge span increases continuously, and the growth rate is “fast in front and slow in back”, which is consistent with the impact of concrete shrinkage and creep on the bridge. The results of this paper can provide an important basis for the anti-explosion protection and reinforcement of concrete extra-wide self-anchored suspension bridge.

Inversion of dynamic displacement response of cable in the whole field based on single vibration measurement

Aiming at the problem that the dynamic displacement at critical positions of the cable cannot be measured due to economic or difficult installation, this paper proposes a method to invert the dynamic displacement of the cable in the whole field by using the dynamic displacement of a single measuring point. The method can realize the inversion of the lateral dynamic displacement response (L-DDR) and angular dynamic displacement response (A-DDR). Firstly, the exact mode shape functions of the L-DDR and A-DDR, considering bending stiffness, sag, inclination angle, and boundary conditions, are derived from the cable vibration control differential equation. The exact mode shape functions are a closed-form solution; thus, it can accurately calculate the cable mode shape at any frequency in real time. Then, an inversion method of the dynamic displacement of the cable in the whole field is proposed based on the amplitude ratio of the exact mode shape. This method can be used to invert the dynamic displacement of the cable in the frequency domain and time domain. Finally, through a numerical simulation and an actual cable test, it is verified that the accuracy of the proposed method is satisfactory. The cable dynamic displacement components at modal and external load frequencies are the main contributors to the dynamic displacement of the cable.

Predicting wildfire ignition induced by dynamic conductor swaying under strong winds

During high wind events with dry weather conditions, electric power systems can be the cause of catastrophic wildfires. In particular, conductor-vegetation contact has been recognized as the major ignition cause of utility-related wildfires. There is a urgent need for accurate wildfire risk analysis in support of operational decision making, such as vegetation management or preventive power shutoffs. This work studies the ignition mechanism caused by transmission conductor swaying out to nearby vegetation and resulting in flashover. Specifically, the studied limit state is defined as the conductor encroaching into prescribed minimum vegetation clearance. The stochastic characteristics of the dynamic displacement response of a multi-span transmission line are derived through efficient spectral analysis in the frequency domain. The encroachment probability at a specified location is estimated by solving a classical first-excursion problem. These problems are often addressed using static-equivalent models. However, the results show that the contribution of random wind buffeting to the conductor dynamic displacement is appreciable under turbulent strong winds. Neglecting this random and dynamic component can lead to an erroneous estimation of the risk of ignition. The forecast duration of the strong wind event is an important parameter to determine the risk of ignition. In addition, the encroachment probability is found highly sensitive to vegetation clearance and wind intensity, which highlights the need of high resolution data for these quantities. The proposed methodology offers a potential avenue for accurate and efficient ignition probability prediction, which is an important step in wildfire risk analysis.

Seismic Reduction Performance of Wrap Rope Connection Devices for Continuous Girder Bridges

In this article, wrap rope connection device (WRCD), which considers the relative acceleration of piers and beam as a control variable, is proposed for improving the current situation of continuous girder bridges whose bearing force of a single pier is along the longitudinal direction and based on the synergy principle. The WRCD device, which meets the slow displacement requirements of temperature and vehicle load under normal operation, is implemented and used to improve the performance of the sliding bearing pier. During earthquakes, because of the amplification effect of the wrap rope, the instantaneous large stiffness state in the longitudinal force can be achieved. Based on the shaking table test of a typical continuous girder bridge for examining the performance of the WRCD during earthquakes, the dynamic characteristics, structural acceleration, displacement, and strain responses of the structure under different frequency spectra, and seismic input intensities are analyzed and the seismic reduction performance of the WRCD is demonstrated. This analysis demonstrated that, by activating WRCD, the ratio of the acceleration response of the fixed bearing pier to the sliding bearing pier increased from 10% to 57%; moreover, the force on each pier appeared more uniform. Furthermore, with an increase in the input intensity of the earthquake, the displacement of the primary beam and the seismic response of the fixed pier bottom considerably decreased and the synergy effect of each pier was more prominent. Under certain site conditions, the WRCD can effectively improve the synergy effect between the sliding bearing piers and fixed bearing pier; however, the improvement in the obtained result is directly associated with the seismic input characteristics. The design parameters of the WRCD should be determined as per different site conditions and the optimum application range of the WRCD.

Nonlinear vortex-induced vibrations of fluid-conveying tensioned pipes in super-critical regimes

Nonlinear vortex-induced vibration (VIV) properties of the fluid-conveying pipes in super-critical regimes subjected to the combined action of external fluid and axial tension are investigated. A new nonlinear dynamic model taking into account the variation of axial tension and the action of external flow is proposed. According to the van der Pol equation, the interaction between the pipe and external flow is evaluated. More specifically, the nonlinear governing equations are established based on Hamilton's principle, and they are then discretized via the Galerkin method and solved by the fourth-order Runge-Kutta method. The VIV amplitudes obtained from the present theoretical model are compared with the published experimental results, which validates the effectiveness and accuracy of the proposed nonlinear dynamic model. It is found that keeping the external fluid velocity constant, with the increase of internal fluid velocity, the growth rates of the maximum response amplitudes in different directions of the buckled pipe are the same under different tensions. When the internal fluid velocity is kept constant, for the pipe in post-buckling state, increasing the tension will be accompanied by decreasing the dynamic stiffness of the pipe, which leads to the increase of the dynamic displacement response. When the pipe in super-critical regime is subjected to variable tension, the increase of the time-varying tension amplitude can either enhance the maximum response amplitude in the cross-flow (CF) direction of the pipe or suppress it.

An Uncertain Vibration Analysis Method for Nonlinear Systems Under Interval Process Excitations

This paper proposes an interval vibration analysis method for nonlinear systems subjected to uncertain excitations, through which its dynamic displacement response bounds can be calculated effectively. In the proposed method, the uncertain excitations are described using the interval process model developed by the authors in recent years. Firstly, the displacement response of a certain degree of freedom for a nonlinear system at an arbitrary time point is expressed as a function of several standard uncorrelated interval variables by using the interval K–L expansion. Secondly, two constrained optimization models are established for the lower and upper bounds of the displacement response of the nonlinear system at the time point. Thirdly, the efficient global optimization (EGO) method is used to solve the above optimization models, and the dynamic displacement response bounds of the nonlinear system can be further obtained. Finally, the effectiveness of the proposed method is verified by investigating two numerical examples.

Vibration attenuation characteristics of finite locally resonant meta beam: Theory and experiments

Dynamic vibration absorbers are of utmost importance in civil and mechanical engineering applications; however, their intricate mechanisms are always challenging for practical realization. This paper investigates the vibration suppression characteristics of a base-excited cantilever beam having a series of lumped masses and spring–mass resonator systems. Both analytical and experimental investigations are carried out to compare the transmittance of the dynamic displacement response of the entire system. In the analytical method, a single unit cell comprises an Euler Bernoulli beam attached by a lumped mass and a spring–mass resonator (SMR) system. The transfer matrix method establishes the force–displacement relationship between each unit cell. Furthermore, experiments were conducted by applying a monochromatic frequency to the beam and detecting transmitted vibrations at the beam and SMR systems. The experimental results are validated with the analytical results, providing essential confidence in our proposed methodology. Moreover, several parametric studies were also conducted to obtain the rationale for the variation in the number and location of SMR systems in the vibration characteristics of the entire system.

Theoretical derivation and experimental investigation of dynamic displacement reconstruction based on data fusion for beam structures

Accurately obtaining the dynamic displacement response of the beam structure is of great significance. However, it is difficult to directly measure the dynamic displacement for large structures due to the low measurement accuracy or the installation difficulty of the sensor. Therefore, it is urgent to develop an indirect measurement method for displacement based on measurable physical quantities. Since acceleration and strain contain high and low frequency displacement information respectively, this paper proposes a displacement reconstruction algorithm that can realize the data fusion of the two, which is very helpful for the research of structural health monitoring. Firstly, the stochastic subspace identification (SSI) method is adopted to calculate the strain mode, and then the displacement is derived via the mode shape superposition method. Afterwards, the strain-derived displacement and acceleration are combined by the proposed algorithm to reconstruct the dynamic displacement. Both the numerical simulation and model experiment are conducted to verify the effectiveness of the proposed algorithm. Furthermore, the influences of noise, sampling rate ratio and measurement point position are analyzed. The results show that the proposed algorithm can accurately reconstruct both high-frequency and pseudo-static displacements, and the displacement reconstructed error in the model experiment is within 5%.

Dynamic Coupling Analysis on Thermo–Chemo–Mechanical Field and Fluid–Structure Interaction for Aero-Engine Turbine Blade with Functional Gradient Thermal Barrier Coatings

In this study, an extended layerwise/solid-element (XLW/SE) method is developed for the thermo–chemo–mechanical (TCM) coupling problem of an aero-engine turbine blade with thermal barrier coatings (TBCs). The method consists of two parts, the extended layerwise (XLW) method and the three-dimensional (3D) solid-element (SE) method, which are adopted to formulate the governing equations of TBCs and substrate, respectively. Then, according to the compatibility conditions of displacement, temperature, concentration and internal force equilibrium at the TBCs/substrate interface, the governing equation of the final blade structure is assembled. Through a time integration, the dynamic responses of displacement, temperature and concentration can be calculated. In addition, the fluid–structure coupling analysis is conducted by using COMSOL. The nonuniform thermal load is imported into the XLW/SE method to calculate the mechanical response of blade structure. Finally, the corresponding computing program is compiled with C++. In numerical examples, the TCM coupling analysis is conducted on the blade structure with and without interfacial debonding and delamination damages. To validate the effectiveness of the proposed method, the dynamic TCM responses of the XLW/SE model is compared with those of a 3D elastic model generated by COMSOL, which shows that the two models are in good agreement.

GFRP bar RC columns under lateral low-velocity impact: an experimental investigation

The performance of GFRP (Glass Fiber polymer) bar RC (Reinforced Concrete) circular columns subjected to lateral impact was experimentally investigated. Sixteen GFRP bar RC column specimens representing offshore bridges were constructed and tested. Laboratory tests were performed considering two types of loading conditions (static monotonic and lateral impact) and two different boundary conditions (cantilever and propped cantilever). For the static tests, the displacement and loading performances were estimated by applying lateral monotonic static load through a hydraulic actuator. For the dynamic impact tests, a steel-made truck with a rigid nose was used to simulate the typical vehicle or vessel collision scenarios. The dynamic lateral impact and displacement responses were detailed evaluated under three different impact velocities (2.25, 3.00, and 4.50 m/s). Moreover, a semi-empirical model based on experimental results was proposed for a performance displacement-based structural assessment and maximum displacement prediction. It is found that GFRP bar RC columns have similar performance compared to traditional steel RC columns under lateral impact loads given the same static capacity.

Research on the excavation stability evaluation method of Chaqishan ancient landslide in China

It is well known that the deformation and failure during the slope excavation often depends on the excavation height and slope rate. Based on the theory of loading and unloading response ratio, the present study established an evaluation model of the excavation dynamic load-increasing displacement response ratio and created the instability criterion. During the excavation, the stability law of the Chaqishan ancient landslide was analyzed using the Midas GTS NX finite element software, and four slope excavation schemes were redesigned. The results show that, the variation law of the excavation dynamic load-increasing displacement response ratio was consistent with the evolution law of stability coefficient, and there was an obvious negative correlation between them. Therefore, the stability variation law in the slope excavation could be evaluated using the evaluation model of excavation dynamic load-increasing displacement response ratio.

Study of the Dynamic Response of a Rigid Runway with Different Void States during Aircraft Taxiing

In this study, a set of numerical simulation analysis methods for studying the dynamic response of runway under the action of aircraft taxiing load are presented. An aircraft-runway coupled vibration model was established, and the runway pavement roughness was taken as the vibration excitation source; then, the aircraft taxiing dynamic load was obtained. A three-dimensional finite element model of the runway was established, and the vertical dynamic displacement (VDD) response and its variation law of the runway under different void conditions were studied under the action of the dynamic load of a taxiing aircraft. In addition, using wavelet packet transform, the acceleration signals at different positions of the pavement slab under the sliding load were decomposed into three layers. The relationship among the wavelet packet energy ratio (WPER), the wavelet packet energy entropy (WPEE) of each frequency band, and the void under the pavement slab was obtained. The results show that the established model could quickly and accurately solve the aircraft taxiing dynamic load. In the case of a slight void, the VDDs in the runway center and under the main landing gears had negative exponential and logarithmic relationships with the reduction coefficient of the dynamic elastic modulus of the base layer, respectively. When there was a severe void, the pavement slab was separated from the base layer. The VDDs in the runway center and under the main landing gears were exponentially and linearly related to the slab’s void area, respectively. The vibration signals were extracted at three measuring points, and the wavelet packet energy characteristics of the signals were compared and analyzed. It was found that the WPER and WPEE of the vibration signals in the void area of the slab corner could better reflect the void state of the slab bottom.