Time History Curves Research Articles

Dynamic Analysis of Seventh-Class ColumnFrame with Cushion

In accordance with the relevant regulations of Building Method, this paper uses the finite element model to establish a two-column seven-grade dovetail column frame model. 4 kinds of thin cushions are designed with different elasticity and shear modulus at the bottom of the column. The elastic modulus of the cushion is 1/5, 1/10, 1/15, 1/30 of the column frame modulus. A simple harmonic wave with an amplitude of 50 gal and a frequency of 1Hz-2.5Hz was applied to the wooden frame model with cushion and without cushion. There are a total of 20 models and their natural vibration period is obtained and the relative displacement time history curve of the top of the column was extracted to obtain the displacement angle between each model. The results show that: the natural vibration period of the wooden frame with cushion is greater than that without cushion, and the period increases with the decrease of the elastic modulus of the cushion. As the harmonic frequency increases, the layer displacement angle of each wood frame model decreases, and as the cushion modulus decreases, the decreasing amplitude becomes more gentle, indicating that the cushioned wood structure has better resistance to deformation.

Axial impact behavior of confined concrete filled square steel tubes using fiber reinforced polymer

Existing research on confined concrete filled steel tubular (CCFT) columns has been mainly focused on static or cyclic loading. In this paper, square section CCFT and CFT columns were tested under both static and impact loading, using a 10,000 kN capacity compression test machine and a drop weight testing equipment. Research parameters included bonded and unbonded fiber reinforced polymer (FRP) wraps, with carbon, basalt and glass FRPs (or CFRP, BFRP, and GFRP), respectively. Time history curves for impact force and steel strain observed are discussed in detail. Experimental results show that the failure modes of specimens under impact testing were characterized by local buckling of the steel tube and cracking at the corners, for both CCFT and CFT columns, similar to those under static loading. For both static and impact loading, the FRP wraps could improve the behavior and increase the loading capacity. To analyze the dynamic behavior of the composite columns, a finite element, FE, model was established in LS-DYNA. A simplified method that is compared favorably with test results is also proposed to predict the impact load capacity of square CCFT columns.

Vibration Characteristics of Rolling Mill System under Constraints of the Nonlinear Spring Force and Friction Force from Hydraulic Cylinder

Considering the two kinds of nonlinear constraints of rolling mill hydraulic cylinder, spring force and friction force, the vibration model of rolling mill system is established. The amplitude frequency response equations are obtained by using the average method. Comparing the time history curves of vertical vibration displacement of rolling mill system under the nonlinear spring force and friction force, the amplitude frequency characteristic curves are simulated. The external excitation amplitude is viewed as the bifurcation parameter, and the system bifurcation response changing with the external excitation amplitude is analyzed. The influence of the external excitation amplitude on the system stability is studied. The results indicate that the increase of the nonlinear spring force makes the rolling mill system’s unstable area to become wider, and the influence on the rolling mill system of nonlinear friction force behaves as the damping characteristics; the vibration of rolling mill system is alternating between the periodic, period-doubling, and the chaotic motion. The research results provide a theoretical support for restraining the vibration of the rolling mill system in the actual production process.

Time-dependent load transfer behavior of grouted anchors in laterite

The load transfer behavior of grouted anchors is time-dependent under long-term (creep) load. This study aims at investigating the time-dependent behavior of grouted anchors in laterite by both physical model test and theoretical simulation. A laboratory creep pullout model test of full-length-bond grouted anchor in laterite was carried out using a special developed apparatus. The creep pullout load–displacement response at anchor head and time history curves of axial strain were tested and presented. The creep behavior on the grout - soil interface was simulated using Merchant rheological model in theoretical simulation. By comparing the experimental data with predictions, the applicability of the proposed theoretical method was validated, and the time-dependent load transfer behavior of grouted anchors was discussed. The impacts of five model parameters on the time-dependent pullout response were further analyzed by parametric studies. It revealed that the tensile force distribution tends to be linear, and the shear stress distribution towards uniformity as time elapsed. Additionally, the time-dependent load transfer behavior for grouted anchors is influenced by the above parameters in various levels. This work provides insights into understandings of time-dependent behavior, and facilitates the service life design practice for grouted anchors embedded in laterite.

Comparative analysis on various components of heave damping for sandglass-type floating body

For the new sandglass-type floating body with special shape, this paper mainly analyzes the characteristic of the heave damping and its corresponding components by computational fluid dynamics (CFD) method. Firstly, the convergence and accuracy of the CFD method to simulate the heave motion of sandglass-type floating body were validated along with the experimental data. Secondly, the numerical model of the floating body with forced heave motion was created, and then hydrodynamic forces versus different motion amplitudes were calculated and compared to discuss its nonlinear characteristics. Afterwards, based on time-history curves of the hydrodynamic force, heaving added mass and damping of the floating body versus various frequencies were achieved and found to be different from the potential results. In order to analyze the reasons that cause difference, numerical simulations using inviscid and k-ε turbulent models were performed respectively, and the results indicate that the effect of fluid viscosity on the hydrodynamic coefficients is small and not decisive. Then equivalent radiation damping based on CFD wave elevation was deduced to explore the relation between the inviscid CFD and potential models. Finally, local wave field and vorticity field near the body were mainly discussed, and quantitative analysis based on mechanical energy was performed to verify that the vortex due to the body shape is the essential cause of the heave damping for the sandglass-type floating body.

Simulation Study on Blast Resistance Test of Blast Wall Based on LS-DYNA Coupling Method

In order to study the pressure change with time at the blast face of the blast resistant wall when the shock wave acts on the blast resistant wall after the explosion of TNT explosive, the equivalent model of the blast resistant wall is designed based on the similarity theory, and the TNT near ground explosion test is carried out. During the test, the pressure change data of the design measuring point on the blast resistant wall with time are collected by high-speed data acquisition instrument and pressure sensor, The time history curve of shock wave overpressure was obtained by processing the data. Then, LS-DYNA finite element analysis software is used to establish a separate finite element model of the blast wall. At the same time, the relevant parameters of air, explosive, concrete and ground in the explosion field are set. The numerical simulation of the explosion field is carried out, and the overpressure time history curve at the measuring point is extracted by the finite element analysis post-processing software. Compared with the numerical simulation results, it is found that the numerical simulation results are in good agreement with the experimental data, which indicates that the selection and setting of parameters in the simulation calculation are reasonable. The model and algorithm provide an effective means for the numerical simulation of blast wall in the explosion field.

Simulation of subway tunnel construction process based on fi-nite element analysis

Simulation of subway tunnel construction process based on fi-nite element analysis

Optimum gas tank locating in van vehicle – front and side crash analysis consideration for passenger safety

In this research, crash test results from CNG locating method optimization approach for crashworthiness and testing its safety are presented. The locating process is based on principal energy considerations inspired from the current design process in passenger vehicle design development. The potential of the vehicle concept to absorb kinetic energy can be estimated at the very beginning of the design process by the free crash lengths in the different areas of the vehicle and estimates of average forces required in the specific segment and parts of the car body at particular crash phases. Based on the basic principle of vehicle crash analysis using the finite element method, a passenger VAN finite element model was selected to simulate the front and side rear collision test of the VAN, therefore the LS-DYNA software is adopted to calculate the deformation of the car and the acceleration time history curves during the crashing process; the anti-impact capability of the vehicle is evaluated from this simulation. It is important to determine appropriate force distributions and the corresponding loads paths through the whole structure for all relevant crash load in dedicated crash test cases. The results demonstrate that the improvement of local structure and location for the required CNG tanks in safe locations in vehicle chassis can promote the crashworthiness of the car, but the further improvement needs a major change of the vehicle structure. The outcomes are interpreted by using LS-PREPOST to analyze the energy absorption characteristics during crash for different cases at a velocity of 50km/h the duration of 12ms. The result analysis was necessary to derive distinct deformation phases characteristic and following that, the essential crash elements are compared with and without CNG tanks installation in each crash case. At last, the conclusion determines the proposed tank locating model in the selected passenger VAN is within the safe range of crash analysis standards.

Experimental Study on the Damage Characteristics of Polymer Slabs Subjected to Air Contact and Close‐In Explosions

As a new antiseepage reinforcement material, polyurethane grouting material has been widely studied in terms of its static mechanical properties. However, research on its dynamic mechanical properties is relatively rare. In this research, considering the influence of the explosive charge weight, the air contact and close‐in explosion experiments of polymer slabs were carried out. The failure mode and damage spatial distribution characteristics of polymer slabs were explored. Pressure time history curve of air shock wave was obtained using an air shock wave tester. The influence of polymer slabs on the propagation of air explosion shock wave was compared and analyzed. The results show that, under the air contact explosion, the polymer slab mainly suffers local damage, while under close‐in explosion, overall damage is the main damage mode. With the increase of the explosive charge weight, the failure mode of the polymer slab transits from surface crack and slight spalling to local and whole crushing.

LOW-VELOCITY IMPACT RESPONSES OF FG-GRC SANDWICH BEAMS WITH VISCOELASTIC CORES

The dynamic snap-through and oscillation behaviors are studied of a post-buckled functionally graded graphene reinforced composite (FG-GRC) beam with a viscoelastic core under low-velocity impact. The modified Halpin Tsai meso-mechanical model is used to predict the material properties of FG-GRC. The Hertz point contact model is used to calculate the contact force between the impactor and the post-buckled beam. Considering the axial prestress, the constitutive relations of the composite layer and the Kelvin type viscoelastic constitutive model of the damping layer are proposed. A generalized higher-order shear deformation zig-zag beam theory is utilized to model the nonlinear displacement fields. Based on the Hamilton energy variational principle, the governing equations of dynamics are derived. Through two-step analysis, the post-buckling equilibrium paths are obtained as the initial state condition for the impact problem analysis. Further, combined with the fourth-order Runge Kutta method, the two-step perturbation-Galerkin method is extended to simulate the time history curves of the contact force and the dynamic response curves of the post-buckled beams. Compared with the results based on other beam models, the correctness of the material model, theoretical model and computation method is validated. The dynamic characteristics of bi-stable large amplitude vibration of the post-buckled beams under single and two collisions are studied. The effects of axial load, impact velocity, viscoelastic damping characteristics and impactor materials on the contact force and the deflection time history curves of the post-buckled beams are discussed. The results suggest that the contact force is only sensitive to the impact velocity. A certain structural collision parameter design can change the response of the post-buckled beam from single potential energy trap motion to double trap large oscillation, and the contact force is approximately unchanged. The results of this work can be of reference significance for the design of bi-stable energy capture system with collision.

Study of shaking table substructure test loading by inertial mass

It is hardly to carry out large-scale shaking table test of entire structure for the high cost of model construction and the capability limited of shaking table in the field of civil seismic research. In this paper, a shaking table substructure test method loading by inertial mass was studied, and the inertial mass parameter was designed based on the principle of frequency equivalence. Numerical simulation was performed and the applicability of the test method was analysed. A shaking table test model of 5-stories steel frame model and the substructure test loading by inertial mass have been carried out. Result shows that the phase of the time history curves could in good agreement, but the peak responses of the substructure model were larger than the entire structure tests. So, the shaking table substructure test loading by inertial mass based on the principle of frequency equivalence is not suitable for the structure with uniform distribution of mass and stiffness. Finally, it has been verified that the substructure test based on the principle of frequency equivalence is suitable for the structures with large rigidity and concentrated mass by analysing of another example. The research of this paper could be referred for substructure test of large and complex structure.

Research on the Health Detection of Spatial Grid Structures Based on Deep Learning

With the popularization of space grid structure, the health detection of structure is an urgent problem to be solved. According to the distribution law of members and the characteristics of clear force transmission, a grid model with 29 nodes and 76 members is designed. For the model, the response time history curves of nodes are collected when the model is in good condition and some members are damaged, and the curve time history information is taken as the input vector to construct the damage information matrix. The deep learning network is established step by step by using the deep learning algorithm and trained. Through the establishment of a simplified network, the damage location and damage degree of single bar are identified. The results show that the established network can identify the health state of the structure well, and it has reference value for application.

Simple Rational Model for Discharge of Batteries with Aqueous Electrolytes, Based on Nernst Equation

A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length Δt, is presented, for proposed model. The model is first applied to Daniel cell, in order to clarify concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage E-t, is due to initial under-concentration of product ion. Then, model is applied to a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.

Evaluation of the effects of protective measures implemented in high-rockfill slope engineering based on the discrete element model

There has to date been no quantitative analysis of the anti-sliding effects of protective measures implemented in high steep rockfill slope engineering under conditions of instability, despite the importance of this analysis for engineering design, improvement to engineering measures, and promotion of hazard warning and management. This study established a discrete element model (DEM) of a high steep rockfill slope based on an engineering project. Numerical simulation was used to investigate the anti-sliding effect of concrete retaining wall height on the high rockfill slope under conditions of instability, with a focus on the distributions of rock before and after slope instability, rock displacement, the quantity of rock crossing the concrete retaining wall, and the quantity of rock reaching the riverbed. The trajectory of rolling rock changes in velocity under different concrete retaining wall heights, and the resistance to rolling rock by the retaining wall were analyzed. Movement trajectories and velocity time-history curves of rolling rock suggested that a higher concrete retaining wall could enhance slope stability under long-term operation. Quantitative analyses determined the optimum height of the concrete retaining wall. The method proposed in this study could provide guidance for effective protective measures in high steep rockfill slope engineering.

Research on Bridge Structure Reliability Evaluation due to Vessels Collison Based on a Statistical Moment Method

Damage to bridge structures caused by vessel collision is a risk for bridges crossing water traffic routes. Therefore, safety around vessel collision of existing and planned bridges is one of the key technical problems that must be solved by engineering technicians and bridge managers. In the evaluation of the reliability of the bridge structure, the two aspects of vessel‐bridge collision force and structural resistance need to be considered. As there are many influencing parameters, the performance function is difficult to express by explicit function. This paper combines the moment method theory of structural reliability with finite element analysis and proposes a statistical moment method based on finite element analysis for the calculation of vessel‐bridge collision reliability, which solves the structural reliability problem with a nonlinear implicit performance function. According to the probability model based on current velocity, vessel velocity, and vessel collision tonnage, the estimate points in the standard normal space are converted into estimate points in the original state space through the Rosenblatt reverse transform. According to the estimate points in the original state space and the simplified dynamic load model of vessel‐bridge collision, the sample time‐history curve of random vessel‐bridge collision force is generated, the dynamic response of the bridge structure and the structural resistance of the bridge are calculated by establishing a finite element model, and the failure probability and reliability index of the bridge structure is calculated according to the fourth‐moment method. The statistical moment based on the finite element analysis is based on the finite element analysis and the moment method theory of structural reliability. The statistical moment of the limited performance function is calculated through a quite small amount of confirmatory finite element analysis, and the structural reliability index and failure probability are obtained. The method can be widely used in existing finite element analysis programs, greatly reducing the number of finite element analyses needed and improving the efficiency of structural reliability analysis.

Dynamic Response Analysis of Retaining Dam under the Impact of Solid-Liquid Two-Phase Debris Flow Based on the Coupled SPH-DEM-FEM Method

Based on the coupled SPH-DEM-FEM numerical method, this paper analyzes the dynamic interaction of solid debris flow particle-liquid debris flow slurry-retaining dam in order to explore the dynamic response of retaining dam under the impact of the solid-liquid two-phase debris flow and delves into the process of the debris flow impact on the dam, the impact force of debris flow, and the elastic-plastic time-history characteristics of the dam under different slopes of trapezoidal grooves. The calculation results show that the coupled SPH-DEM-FEM method can vividly simulate the impact behavior of the solid-liquid two-phase debris flow on the dam, reproduce the impact, climbing, and siltation in the process of the debris flow impact; the dynamic time-history curve of the retaining dam is consistent with the law of the literature, and the result of the debris flow impact force obtained is close to that of the empirical formula. Moreover, this paper studies the impact force distribution of the debris flow impact process. The results have a certain reference value for the study of the dynamic response of the retaining dam under the impact of the solid-liquid two-phase debris flow and the engineering design of the debris flow-retaining dam.

Thermo-electro-mechanical dynamical response and the failure of an electro-active polymer cylindrical shell

Electro-active polymers are often subjected to periodic loading when used as actuators or resonators, thus the dynamical response and the failure of the material subjected to electro-mechanical coupling loading with the effect of temperature are important. The nonlinear thermo-electro-mechanical dynamical response and the failure of an incompressible electro-active polymer cylindrical shell subjected to a suddenly applied constant load or a periodic internal load are analyzed within the framework of finite elasto-dynamics in this paper. The time history curves, phase portraits, Poincare maps of the shell in terms of different pressures, voltages, temperatures or wall thicknesses are presented through numerical computation. The attention is focused on the parameter effect on the motion of the shell and the corresponding critical values. Results indicate that the shell will undergo nonlinear periodic oscillation or quasi-periodic oscillation, and maybe a failure with time if one of the parameters for load, voltage, temperature or wall thickness exceeds its critical value. It is hoped that the results of this paper may provide a numerical reference for the related application and design of diverse electro-active polymers.

The support load analysis of deep-buried composite lining tunnel in rheological rock mass

The loads on primary support and secondary lining in composite lining tunnel are one of the key problems in support design. The primary support and secondary lining which as the main bearing structure determines the long-term operation safety of tunnels. In this study, three kinds of tunnel support conditions are established and the rheological model, stress releasing coefficient and additional radial body force of bolts are considered. Also, the analytical formulas of displacement on the primary support and secondary lining are derived. According to the relationship between displacement difference and support stiffness, the support loads are obtained. The calculated displacements and loads of the support structure are basically consistent with the field measurement, which verifies the reliability of the theoretical method. In addition, the influences of support parameters on the support load and bearing ratio are studied. Finally, the variation of the time-history curves of the measured support loads are discussed. The results show that the installation time of primary support, installation time of secondary lining, bolt length, thickness of the secondary lining, cohesion and rheology all may influence the support load. Meanwhile, the thickness of the secondary lining and the installation time of secondary lining have greater impact to the load bearing ratio. The combination of the weak rock mass, the early installation of the secondary lining, and the insufficient thickness of the secondary lining will make the load ratio of the secondary lining significantly higher. The stress paths of support loads are different depending on whether the support structure is in tension or in compression.

Seismic Performance of Substrate for Vegetation Concrete from Large-Scale Shaking Table Test

The substrate for vegetation concrete is a new type of plant substrate used for slope protection. While it has demonstrated good performance in slope protection and a greening effect, the sustainability of ecological restoration projects is difficult and there are significant construction risks in areas with frequent earthquakes. In this study, a new type of substrate for vegetation concrete was developed for areas with frequent earthquakes, and a shaking table test was performed to evaluate the seismic performance. The test results indicated that the proposed substrate of the vegetation concrete displayed good stability under seismic excitation at earthquake intensities of V, VI, VII, and VIII. A comparison of several different reinforcement methods under seismic conditions indicated that wavy laying of a flexible net was the best reinforcement method. Through observation of the displacement time history curve and macroscopic phenomenon, the failure process of the substrate layer was obtained and consisted of the following three stages: cracking between substrate layer and bedrock, internal cracking of the substrate layer, and vibration crushing. Ultimately, the research results have significant reference value for ecological restoration projects using substrates for vegetation concrete in areas with frequent earthquakes.

Calculation Method of Bonding Section of Joint Surface of Dangerous Rock Mass Based on Amplitude Ratio

In this study, through an analysis of vibration response characteristics of joint surface stiffness on dangerous rock mass, the relationship formula between amplitude ratio of the dangerous rock mass to the bedrock and the length of the bonding section of the joint surface is determined. The stability of the rock mass can be evaluated by combining the formula with the existing rock-mass limit equilibrium theory. This study proposes the existence of a resonance bonding length for the dangerous rock mass. When the length of the bonding section reaches the resonance bonding length, the dangerous rock mass has the largest response to the bedrock vibration. The study found that when the length of the bonding section of the dangerous rock mass is longer than the resonance bonding length, the amplitude ratio increases with the decrease of the bonding section and increases with the increase of the vibration frequency of the bedrock. When the length of the bonding section of the dangerous rock body is shorter than the resonance bonding length, the amplitude ratio decreases with the decrease of the bonding section and decreases with the increase of the vibration frequency of the bedrock. Indoor experiments were conducted by collecting the vibration time-history curves of rock blocks and stone piers and performing analysis and calculation, which proved the accuracy of the analytical results. Through the amplitude ratio of the dangerous rock mass and the bedrock, the bonding length can be calculated. This method can improve the calculation accuracy of the stability coefficient K of the dangerous rock mass.