Time History Curves Research Articles

Influence of bedrock on viscoelastic responses and parametric back-calculation results for asphalt pavements and prediction of bedrock depth under FWD tests

Structural evaluation with a falling weight deflectometer (FWD) plays an essential role in the maintenance and rehabilitation of highways. Research on the influence of bedrock on the results of FWD tests and dynamic back-calculations for asphalt pavements has been a hot topic. In this study, the viscoelastic characteristics of the asphalt surface layer were described by the modified Havriliak-Negami (MHN) model rather than the layered elastic theory computing framework. The effects of bedrock on the deflection time history curves of viscoelastic asphalt pavement under the FWD test were investigated and analyzed by the spectral element method with fixed-end boundary conditions (B-SEM). The effects of bedrock on parametric back-calculation results for the viscoelastic asphalt surface layer and other elastic layers were explored by dynamic back-calculations. To exclude the impact of bedrock and improve the back-calculation accuracy, support vector regression optimized by the gravitational search algorithm (GSA-SVR) was adopted to predict bedrock depth. The viscoelastic responses and dynamic parametric back-calculation results were significantly influenced by bedrock beneath asphalt pavements, and the influence decreased (but was not eliminated) with increasing depth of bedrock. The GSA-SVR model provided excellent predictions of bedrock depth, and it can be applied for pavement performance assessment in road projects.

Behavior and modeling of large-scale concrete-filled FRP tubes with longitudinal steel rebars under lateral impact loading

Fiber-reinforced polymer (FRP) has been utilized extensively as a confining material for concrete in civil engineering. Concrete-filled FRP tubes (CFFTs), consisting of a FRP tube, a concrete core and optional longitudinal rebars, are particularly attractive to be used as bridge piers in harsh environments. Most studies on CFFTs have been focused on their behaviors under static loading conditions. To extend existing studies, three identical large-scale CFFTs with longitudinal steel rebars (SR-CFFTs) were investigated experimentally, two of which were tested under lateral impact loading and one was under lateral static loading. To compare the confining behavior between FRP tube and steel stirrups, three identical large-scale reinforced concrete (RC) columns with approximately the same hoop confinement stiffness as SR-CFFTs (i.e., steel stirrups for RC columns, FRP tube for SR-CFFTs) were tested as companion specimens. The test results indicated that, (1) under lateral static loading, the RC column failed with a shear-failure manner, while the SR-CFFT specimen failed with combined bending and shear failure characteristics; (2) under lateral impact loading, the shear-dominant failure mechanism was evident for RC columns, while the failure mechanism of SR-CFFTs was flexural-dominant owing to the effective hoop confinement provided by FRP; (3) under the same impacting velocity, the SR-CFFT specimen had much less damage and much less lateral displacement than the corresponding RC column. The established FE models could provide reasonably accurate predictions for the dynamic behaviors, the impact force–time history curves and the column deformations for both RC columns and SR-CFFTs. Parameter studies were conducted to analyze the effects of the concrete strength, the longitudinal steel ratio, the impact velocity and the impact mass.

Analytical and numerical study of a vibrating magnetic inverted pendulum

The current study investigates the stability structure of the base periodic motion of an inverted pendulum (IP). A uniform magnetic field affects the motion in the direction of the plane configuration. Furthermore, a non-conservative force as one that dampens air is considered. Its underlying equation of motion is derived from traditional analytical mechanics. The mathematical analysis is made simpler by substituting the Taylor theory in order to expand the restoring forces. The modified Homotopy perturbation method (HPM) is employed to achieve a roughly adequate regular result. To support the prior result, a numerical method based on the fourth-order Runge-Kutta method (RK4) is employed. The graphs for both the analytic and numerical solutions are highly consistent with one another, which indicates that the perturbation strategy is accurate. The solution time history curve exhibits a decaying performance and indicates that it is steady and without chaos. The resonance and non-resonance cases are found through the stability study by using the time scale method. In all perturbation approaches, the methodology of multiple time scales is actually regarded as a further standard approach. The time history is used to create a collection of graphs. Some graphical representations are used to illustrate how the typical physical values affect the behavior of the discovered solution. It has been discovered that the statically unstable IP can have its instability reduced by raising the spring torsional constant stiffness as well as the damped coefficient. Moreover, the magnetic field has a significant role in the stability configuration, which explains that at higher values of this field, the decaying waves take much more time than the smaller values of this field. Accordingly, it can be employed in various engineering devices that need a certain period of time to be more stable.

A combined method to identify the rail irregularity at welded region

The track irregularities affect the safety and comfort of running vehicle and increase the dynamic responses of vehicle and track. There is the rail irregularity at the welded region, and the irregularity can be regarded as the superposition of two cosine waves with the long wavelength about 1 m and the short wavelength of 0.1–0.2 m. The welded location has both short-wavelength irregularity and long-wavelength irregularity. A combined method is presented to identify the rail irregularity at the welded region using the acceleration time history curve of wheelset. Firstly, the accelerations of wheelset are transformed into the different frequencies domain signals by wavelet transformation, and the rail irregularity with the short wavelength and high-frequency is determined. Secondly, the rail irregularity with the long wavelength and low-frequency is identified by the Wigner–Ville distribution or the short-time energy method. Finally, the rail irregularity at the welded region is determined by both of the above two steps met. The correctness of the proposed method is validated by numerical example. The proposed method can accurately and efficiently identify the high-frequency and low-frequency characteristics of the rail irregularity at the welded region.

Energy Measurement in Standard Penetration Tests

The standard penetration test (SPT) is a widely used in situ test method worldwide that can evaluate soil properties based on the blow counts (N-value). The N-value depends on soil properties, and the energy transferred to the drill pipe during hammering. Currently, European and American scholars generally believe that variation in the amount of hammer energy transmitted to the drill pipe due to different types of drop hammer systems is the primary factor that leads to variations in N-value. In China, there is a lack of research on the quantitative energy transfer efficiency of the drop hammer system based on test data from a penetration test instrument. In this study, an in-situ test in Jiangsu Province was performed at a test site using standard penetration test instruments that are commonly used in China. Corresponding time history curves and strain, acceleration, force, velocity, energy and penetration degree data were obtained through the stress wave test. The propagation law of the stress wave and energy in a drill pipe was analyzed, and the energy transfer efficiency of the domestic SPT system was measured. In the stress wave test, most of the measured hammer energy efficiency was between 74.5 and 84.5%, and the measured average energy was 0.3723 kJ; the average energy efficiency was 78.7%; the standard deviation (SD) of the energy efficiency was 3.82, and the coefficient of variation (CV) of energy transfer efficiency(ER) was 4.9%. The average energy efficiency of 78.7% can be considered to be the energy efficiency of the domestic SPT system. The calculated results reported in this article can be used to improve the quantitative level of domestic investigation. Based on the calculated Er, the results obtained from different SPT systems at home and abroad can be corrected.

Numerical and Analytical Investigations of the Impact Resistance of Partially Precast Concrete Beams Strengthened with Bonded Steel Plates

A building may be subjected to a variety of accidental loads during its service life. Partially precast concrete (PC) beams are a primary structural component. Their impact resistance can have a substantial impact on the overall safety of a structure when it is subjected to an impact load. In this study, numerical analyses were performed on the dynamic response of PC beams strengthened with bonded steel plates subjected to impact loading. The model was verified from four aspects: energy conversion, failure form, impact force–time history curve, and midspan displacement–time history curve. The dynamic response eigenvalues of the peak impact force, peak midspan displacement, and residual midspan displacement were compared between the numerical simulations and experimental tests. The relative inaccuracy of the peak impact force ranged from 9.51% to 14.0%, with an average value of 11.9%. The average relative error for the midspan displacement was −0.09%, with the greatest relative errors varying between −0.64% and 0.3%. The residual value errors of the midspan displacement ranged from −0.95% to 2.38%, with an average relative error of 0.94%. On this basis, the effects of the impact mass, impact height, width, and length of the bonded steel plate on the impact resistance of the components were evaluated. Furthermore, the differences in the equivalent plastic strain contours, impact force–time history curves, and midspan displacement–time history curves under different parameters were compared. The results demonstrated that the failure modes and flexural deformations of the test beams were influenced by the impact mass and impact height. The increase in the length and width of the steel plate had no effect on the impact force response, but the peak and residual values of the midspan displacement decreased, which could significantly increase the impact resistance of the beams. Lastly, the impact mass m, the impact height h, the thickness t of the bonded steel plate, the length of the bonded steel plate hs, and the width of the bonded steel plate bs were all taken into account in the fitting formula. These five parameters were used to predict the peak impact force response, the peak value of the midspan displacement, and the residual value of the midspan displacement. The results demonstrated that the fitting formula had small errors and could accurately reflect the dynamic responses of the PC beams strengthened with bonded steel plates under impact loading.

Analysis of Dynamic Response and Current-Carrying Capacity of Bridge-along Cable under Typhoon Load

In order to study the structural dynamic response and dynamic load capacity of bridge-along cable under typhoon load, in this paper, the cable under two laying environments, including the steel box girder and steel platform, are taken as the research object. Shiyuan typhoon spectrum and harmonic superposition method are adopted to obtain the wind speed time history curves corresponding to different scales of typhoon wind force, then the wind-induced pulsating displacement of steel box girder and steel platform is calculated by using the wind speed time history curve. The electromagnetic-thermal-structure coupling model is established, and the obtained pulsating displacement under typhoon load is applied to the cable as a boundary condition to obtain its dynamic response characteristics. The eccentricity of XLPE insulation is used as the evaluation index of the current-carrying capacity of cable under different scales of typhoon wind force and different laying environments. The simulation results show that the maximum stress amplitude on the metal layer occurs near the clamp during cables are forced to move under typhoon load. The higher the typhoon wind force, the lower the allowable current-carrying capacity. Under wind force 10, the current-carrying capacity is not affected by the typhoon weather; under wind force 11, the current-carrying capacity dropped by 17.2%; under wind force 12, the current-carrying capacity dropped by 47.7%; under wind force 13, the cables are not recommended to work. The research results provide theoretical guidance for assessing the power supply reliability of bridge-along cables under typhoon disasters.

Dynamic modeling and analysis of compound pendulum motion of projectile

The influence of air lift on the stability of inaccurate precision strike ammunition is studied, and the mechanical analysis of projectile and its flight stage is carried out. The dynamic equation of projectile under the action of air lift is established and simulated. The angular velocity and angular time-history curve of the compound pendulum motion of the projectile are obtained, and the correctness of the mechanical analysis of compound pendulum motion during flight is verified.

Experimental study on the impact resistance of hollow thin-walled aluminum alloy tubes and foam-filled aluminum tubes (6063-T5)

This paper presents a study on the axial impact resistance of hollow thin-walled aluminum alloy tubes and aluminum foam-filled thin-walled tubes. 15 hollow thin-walled aluminum alloy tubes and 15 thin-walled aluminum alloy tubes filled with aluminum foam were tested under drop hammer impacts. The process of the impact, the failure modes of the specimens, the time history curves of impact forces, and the vertical deflections were recorded in the test. The effects of impact velocity, aluminum alloy wall thickness, cross-sectional width, and aluminum foam on the performance of the hollow and aluminum foam-filled thin-walled aluminum alloy tubes were discussed. In addition, a finite element model was established to simulate the test considering the strain rate effect of aluminum alloy and aluminum foam. The results showed that both hollow and foam-filled thin-walled aluminum alloy tubes were damaged to different degrees. Under the same impact energy, the damage of the foam-filled thin-walled aluminum alloy tube was less severe than that of the hollow thin-walled aluminum alloy tube; under the axial impact load of the drop hammer, the most effective way to improve the impact resistance of the hollow and foam-filled thin-walled aluminum alloy tubes was to increase the wall thickness of the outer thin-walled aluminum alloy tube, while the effect of increasing the cross-sectional size of the outer thin-walled aluminum alloy tube on the impact resistance of the specimen is less significant. The peak impact force, vertical deflection and the duration of impact forces are most sensitive to the impact velocity.

Evaluation of a novel steel box-soft body combination for bridge protection against ship collision

Abstract Ship–bridge collision is a common type of accident in bridge engineering which could cause heavy casualties and economic losses. To ensure the safety of both the ships and bridges during collision, a novel steel box-soft body combination was proposed in this work. The time history curves of the impact force of three downscaled facility specimens were obtained through the horizontal impact test. The influence of the steel box web spacing and the existence of the anti-collision facilities on the ship collision force reduction rate was investigated. The collision failure modes of ship bow and the anti-collision facilities, as well as the energy absorption behavior of the facility were analyzed. Based on ANSYS/LS-DYNA finite element (FE) analysis software, the nonlinear numerical models of the anti-collision facilities were generated. The analysis results show that the proposed anti-collision facility can not only greatly reduce the ship impact force, but the bow damage as well. The densified steel box web can improve the anti-collision performance of the whole anti-collision facilities to a certain extent. Compared with the direct impact on the steel plate, the maximum reduction rate of peak force of the proposed facility can be achieved to be 31.07%. The anti-collision facilities deformation energy absorption accounts for more than 70% of the total energy, which shows that the facility is able to absorb most of the energy and protect the bow. The FE simulation results coincide with the experimental outcomes, indicating the acceptable accuracy of the FE models.

Dynamic behaviors and equivalent static force of double-column pier under horizontal impact

The booms in transportation and bridge engineering are accompanied by the increasing threat of vehicular collisions with bridge piers. This study experimentally and numerically examines the dynamic behaviors of double-column reinforced concrete (RC) pier subjected to horizontal impact. Firstly, a series of reduced-scale horizontal impact test on five double-column RC pier specimens (containing the impacted pier, adjacent pier, and bent cap) is conducted considering different impact velocities and mass. Then, based on the previously-validated material models and finite element (FE) analysis algorithms, the five present and twelve additional impact cases are numerically simulated. The test and simulated results indicate that, (i) the whole impact process can be divided into cracking, resiling, and oscillating stages, and the impact force–time history and impact force-lateral displacement curve can be simply characterized by six critical points; (ii) the impact velocity dominates the development of impact force–time history, while the effect of impact mass becomes more significant with impact process progressing; (iii), the damage levels of impacted and adjacent piers as well as bent cap, and the maximal lateral displacement of impacted pier are positively related to the impact kinetic energy rather than the impact momentum. Finally, based on the pier shear resistance and the energy conversion, the novel equivalent static force (ESF) and corresponding ESF-based performance design are proposed for double-column RC pier against horizontal impact. The present work can provide the benchmark test data for validating the FE models, and the determination approach for the ESF-based performance design of bridge piers under vehicular collisions.

Research on Low-Velocity Impact Response of Novel Short-Fiber-Reinforced Composite Laminates

Short-fiber-reinforced polymers (SFRPs) based on unidirectionally arrayed chopped strands (UACSs) have excellent formability and outstanding mechanical response. The low-velocity impact response, such as the delamination, damage tolerance and energy absorption of UACS composites, are essential to guarantee the stability and safety of composite components in service. The current study investigates the low-velocity impact response of continuous carbon-fiber-reinforced polymer (CFRP) and UACS laminates with vertical slits under drop-weight impact with various impact energies (4, 7 and 11 J). The in-plane size of the studied samples is 100 mm × 100 mm, and the stacking sequence is [0/90]4s. The time-history curves of load and energy are examined during low-velocity impact experiments, as well as the nonvisible damages are obtained by ultrasound C-scan imaging technique. A user-defined subroutine VUMAT, including the Johnson-Cook material and failure model, which is used to simulate the elastic-plastic property of the slits filled with resin, is coded in ABAQUS/Explicit. According to C-scan inspections of the impact-damaged laminates, UACS specimens show more severe delamination as impact energy increases. The damaged area of continuous CFRP laminates under impact energy of 11 J is 311 mm2, while that of UACS laminates is 1230 mm2. The slits have a negative effect on the load-bearing capacity but increase the energy absorption of UACS laminates by approximately 80% compared to the continuous CFRP laminates at 7 J. According to the variables of different damage modes in numerical simulation, cracks appear at the slits and then expand along the direction perpendicular to the slits, leading to the fracture of fiber. Nevertheless, as the damage expands to the slits, the delamination confines the damage propagation. The existence of slits could guide the path of damage propagation.

A comprehensive numerical study on flow-induced vibrations with various groove structures: Suppression or enhancing energy scavenging

This paper focuses on the enhancement or suppression effect of flow-induced vibration (FIV) caused by symmetrically installed groove structures with different shapes under high Reynolds numbers. The fluid flow field is simulated using the non-constant two-dimensional Reynolds-averaged Navier-Stokes (2D-RANS) equation and the SST k-ω turbulence model. A cylinder attached to four different groove shapes (square, triangular, semicircular, and two quarter-circle splices) is simulated for each shape of the groove with five mounting angles. The oscillatory amplitude, frequency response, displacement time history curve, vortex shedding mode, and energy harvesting characteristics are analyzed for each working condition at 2 < U* < 14 and 2.02 × 104 <Re < 1.44 × 105. The results show that the cylinder with different groove shapes and installation angles have different dynamic responses. The oscillatory amplitude of the square groove bluff body with α = 30°, 60°, and 150° is basically enhanced compared to the smooth cylinder, and the working bandwidth is increased as well. For the square groove placed at α = 60°, the oscillatory amplitude increases by 100% compared to the smooth cylinder, and the working bandwidth of the square groove at α = 90° is reduced by 50%. For the square groove body with α = 120°, the amplitude is enhanced, but the working bandwidth is reduced. The working bandwidth of the triangular groove is widened at all five angles, with the α = 60° groove being optimal, widening by 75%. Except for the triangular groove with α = 90°, the amplitude is improved to some extent compared with the smooth cylinder. The working bandwidths of the semicircular grooves are widened, and the improvement effect of α = 150° is the smallest of the five angles. For the two quarter-circle splices grooves, the grooves arranged at α = 30°, 90°, 120°, and 150° have a decrease in amplitude when U* = 6, and more pronounced at 90° and 120°. Two quarter-circle spliced groove cylinders with α = 120° have the best amplitude enhancement effect.

Failure mechanism and static bearing capacity on circular RC members under asymmetrical lateral impact train collision

This paper aims to validate circular reinforcement concrete (RC) members' responses to the effect of an asymmetrical lateral impact span train collision. It was determined that the RC members' failure mechanism and dynamic response characteristics were important. Numerical analyses were conducted on four specimens. The specimen's crack development pattern, failure mode, impact force, and deflection time history curves are verified. Due to the difference in impact velocity, longitudinal reinforcement, and stirrups ratios, shear cracks indicate two types. A finite element (FE) modeling method has been proposed and successfully demonstrated. Using the control variables to study the failure process and mode, which were affected by reinforcement ratio, impact velocity, and slenderness ratio, by analyzing impact response characteristics. It is found that parameters greatly influence shear cracks' type and development range. Simultaneously, the changes in impact velocity and slenderness ratio affect the failure mode of the members. RC members' mechanical properties and failure mechanisms are studied using test and FE analysis. Members' failure modes, bending moment distribution and development, shear forces, reinforcement strain, and energy consumption are also investigated. The development of type I and type II shear cracks is discussed. A method to determine the shear cracks was proposed through regression analysis by supplementing other scholars' test data and combining it with the study test data.

Vibration Response of the Interfaces in Multi-Layer Combined Coal and Rock Mass under Impact Load

The stress wave generated by impact or dynamic load will produce significant reflection and transmission at the rock coal or rock interface during the propagation process. This will produce dynamic effects such as dynamic tensile, stress superposition and mutation. These dynamic effects will lead to obvious vibration at the interfaces, which is a key factor leading to dynamic damage and the failure of coal and rock mass. In the process of underground engineering excavation, the dynamic damage of a series of layered rock masses is one of the important factors causing geological disasters. Based on the two–dimensional similar material simulation experiment, the coal and rock mass combined of five layers of fine sandstone, medium sandstone, coal, coarse sandstone and mudstone was taken as the research object, and single and multi-point excitation (synchronous/step-by-step) were used to test the time–history vibration curves of rock–coal and rock–rock interfaces under impact load. It was concluded that the change of extreme value of vibration amplitude presented two stages: first increase, and then attenuation. Most of them required 2.25 cycles to reach the peak value, and the dynamic attenuation of amplitude conformed to the law of exponential. Based on Fast Fourier transform (FFT), the spectrum structures of the amplitude–frequency of interface vibration were studied, and the two predominant frequencies were 48.9~53.7 Hz and 92.4 Hz, respectively. Based on the Hilbert-Huang transform and energy equation, 5~7 vibration modes (IMF) were obtained by decomposing the time–history curves. The three modes, IMF1, IMF2, and IMF3, contained high energy and were effective vibration modes. IMF2 accounted for the highest proportion and was the main vibration mode whose predominant frequencies were concentrated in 45.6~50.2 Hz. Therefore, IMF2 played a decisive role in the whole vibration process and had an important impact on the dynamic response, damage and failure of coal and rock mass. In real conditions, the actual predominant frequencies can be converted according to the size and mechanical properties of the coal and rock mass, and the vibration response characteristics of the interfaces between coal and rock mass under impact load were preliminarily revealed. This study can provide reference for monitoring and early warning of coal and rock dynamic disasters, prevention and control of coal and gas outburst and technical development.

Experimental and analytical study on the double steel plates-UHPC sandwich slabs under low-velocity impact

The upgrading of protective structures can be realized through the application of new materials or the innovation of structural forms. A novel double steel plates–concrete (DSC) sandwich structure constructed with an ultra-high-performance concrete (UHPC) core forming a DSUHPC sandwich structure could be applied in Arctic offshore platforms as protective layers. This structure can withstand dynamic pressure derived from impacting ice sheets and vehicles in serve cold regions. This paper presents the dynamic behavior of these DSUHPC sandwich slabs subjected to drop-weight impact load. The superiority of protective performance of DSUHPC sandwich structure was revealed in contrast with the perforation failure mode of reinforced concrete (RC) slabs subjected to the same impact energy. Moreover, the brittleness of concrete material under dynamic load was alleviated by adding steel fibers compared with double steel plates–normal strength concrete (DSNC) sandwich slabs, showing effectiveness in the improvement of material utilization and energy dissipation. Further, the diverse dynamic response of DSUHPC sandwich slabs with different steel plate thicknesses and under different impact velocities was also studied. Finally, a two-degree-of-freedom model was established to predict the time–history curves of impact force and displacement. The acceptable accuracy of the proposed analytical model was demonstrated.

The improved giant magnetostrictive actuator oscillations via positive position feedback damper

&lt;abstract&gt;&lt;p&gt;This article contemplates the demeanor of the giant magnetostrictive actuator (GMA) when a positive position feedback (PPF) damper is used to enable tight control over its vibration. The methodology followed here mathematically searches for the approximate solution for the motion equations of the GMA with the PPF damper, which has been accomplished by using one of the most famous perturbation methods. The multiple scale perturbation technique (MSPT) of the second-order approximation is our strategy to obtain the analytical results. The stability of the system has also been investigated and observed by implementing frequency response equations to close the concurrent primary and internal resonance cases. By utilizing Matlab and Maple programs, all numerical discussions have been accomplished and explained. The resulting influence on the amplitude due to changes in the parameters' values has been studied by the frequency response curves. Finally, a comparison between both the analytical and numerical solutions using time history and response curves is made. In addition to the comparison between our PPF damper's effect on the GMA, previous works are presented. To get our target in this article, we have mentioned some important applications utilized in the GMA system just to imagine the importance of controlling the GMA vibration.&lt;/p&gt;&lt;/abstract&gt;

Simulation analysis of structural nonlinear seismic response

Faced with the difficulty of analyzing structural nonlinear seismic response, this study focuses on the reinforced concrete frame structure and designs a frame that meets the specifications. Artificial synthetic seismic records and natural seismic records were selected, and the acceleration response of the first story of the structure was used as the output sample for the study. On the basis of a nonlinear autoregressive moving average model with external inputs, a neural network model was constructed and nonlinear seismic response simulation analysis was conducted. These results confirm that the research method has good predictive performance and can effectively predict structural nonlinear seismic response. Under the action of artificial earthquake records, there is a small difference between them and the acceleration time history curve and acceleration response peak obtained from time history analysis. Under the action of artificial seismic record ACC12, when the time is 25 s, the calculation results of time history analysis and research methods are 1.715 m/s2 and 1.403 m/s2, respectively, with the former being 0.312 m/s2 smaller than the latter. In natural earthquake records, with a characteristic period of 0.30 s, under the action of natural earthquake record USA00668, the relative energy of time history analysis is 4.997 m2/s when the time is 30 s, which is 0.938 m2/s higher than the research method. The research method can accurately analyze the nonlinear seismic response of the results.

Research on transverse impact performance of pipe-in-pipe structure

Pipe-in-pipe structure are widely used in offshore oil and gas transportation. The structure is subjected to various dynamic loads such as earthquakes and vortex-induced vibrations during service, of which transverse impact is the main cause of structure damage. At present, the whole process analysis and parameter analysis of the pipe-in-pipe structure under the action of impact are not systematic and complete. Based on the explicit dynamic software LS-DYNA, the finite element model of the pipe-in-pipe structure was established, and a systematic parametric analysis was carried out on the parameters of the pipe-in-pipe structure. Based on the three aspects of force, displacement and energy absorption, the influence of the three parameters of span, diameter ratio and thickness ratio on the impact resistance of the tube-in-tube structure is revealed. The research results show that the impact force time-history curve of the pipe-in-pipe structure can be divided into five stages. The resistance of the tube-in-tube structure to impact is significantly influenced by the ratio of thickness and span.

Theoretical analysis and simulation calculation of hydrodynamic pressure pulsation effect and flow induced vibration response of radial gate structure

This work aims to explore the characteristics of stochastic fluctuant water pressure acted on the surface of large radial gate, and to investigate the flow-induced vibration response of the whole radial gate structure. The finite element calculation model structure of the radial gate is established by taking a large-scale radial gate as prototype to discuss the hydrodynamic pressure acting on the gate leaf with different opening, analyze the dynamic pressure time curves, and achieve the flow-induced vibration response by deeming hydrodynamic pressure as dynamic load. When taking 10% opening of the radial gate, the results indicate that the hydrodynamic pressure distributed on the arc surface of the radial gate changes with the flow conditions, with the maximum pressure occurred at the center of the lower edge of the gate leaf. One point in the time history curve of fluctuating water pressure can be taken as the dynamic load for the flow-induced vibration analysis. The flow-induced vibration responses at the monitoring point of the radial gate structure show periodic changes in the X, Y, and Z directions. The finite element simulation results agree well with the theoretical calculation results, so reference can be provided for the hydrodynamic pressure testing and the flow-induced vibration response calculations.