With rapid development of physical testing technology,structural model testing can more correctly obtain dynamic response of structure under action of environmental load.However,in studying model testing problems of soil-structure interaction,regional group structures as well as wind tunnel,pseudo static and dynamic tests of large and complex structures,simple,practical,and correct structural test simplified models are still the study focus.Here,aiming at problems of complex calibration of nonlinear mechanical parameters and insufficient test feasibility in existing model simplification methods,a simplified design method for dynamic test model of high-rise structure was proposed.High-rise structure's bending and shear recovery force models were decomposed into a combination of linear and nonlinear behaviors,structural nonlinear behavior was simulated using Coulomb friction model,because of its parameters being simple and having certain physical meanings,it could be directly applied in dynamic test study for scaled models.Based on the above theoretical methods,effectively combining bending-shear coupled model and translational and torsional friction devices,physical model design method and calculation methods for parameters of equivalent stiffness,post yield stiffness and load-bearing capacity applies in scaled dynamic tests were proposed.The corresponding mechanical calculation model of"interlayer double-shear and double-bending spring"was established.It was shown that the proposed methods can effectively predict dynamic responses of prototype structure in elastic and nonlinear stages with model test results.Taking a certain high-rise structure as an example,the correctness and feasibility of the proposed methods were verified with numerical simulation and shaking table tests.
Blast loading is characterized as an impact loading with exponential attenuation, while damping serves as an intrinsic parameter that affects the vibration effect of beam members. The linear attenuation for simplified blast loading and undamped situation for beam members is often adopted by most scholars or codes for the calculation of dynamic factors. These assumptions that do not conform to the actual situation can lead to deviations in the results of the dynamic factor. In this study, the implicit solutions for the dynamic factors of both flexible and rigid beam members were derived by the exponential attenuation loading and damping of beam members. The dynamic response verification of an H-shaped steel beam blast test was completed using LS-DYNA software. The comparison calculation of the theoretical solutions of dynamic factors in this paper with the Chinese blast-resistant design code and finite element simulation was carried out. The results show that the dynamic factor will be higher when the blast loading is simplified to linear attenuation loading for undamped beams. The shape parameter of the exponential attenuation loading and the damping ratio of beam members both reduce the effect of the dynamic factor, with the damping ratio having a more significant effect.
Ship-mounted cranes are becoming increasingly essential to modern ocean shipping. However, due to the continuous influence of waves, currents, and winds, achieving accurate and fast lifting is difficult because of the large payload swing during the lifting operation. Therefore, this study proposes a Four Anti-swing Cable System (FASCS) for ship-mounted cranes. Firstly, a dynamic model of the FASCS was established by using Robotics and Newton method, and a tension control method (TCM) is designed to reduce the swing angle of the payload. Concurrently, a sliding mode variable structure controller with improved reaching law (SMVSC-IRL) is designed to control the cooperative movement of the anti-swing cables and prevent the occurrence of snap. The dynamic characteristic analysis by MATLAB/Simulink shows that the swing angle suppression effect reaches 89.3% on average, and the projected area of the payload trajectory was reduced by 60%, which can significantly improve the efficiency of ship-mounted cranes lifting operations. In addition, the length and speed of cables in errors can approach 0 within 7 s, and the strong robustness of the designed SMVSC to control the cooperative motion of the anti-swing cables is proved. The results of this study contribute to the in-depth optimization and engineering verification of the FASCS for ship-mounted cranes.
Earthquake damage to engineering structures often occur in near-fault areas. Near-fault ground motion is characterized by high-energy velocity pulses, long action period, and strong destructiveness. This paper forces on the seismic analysis of a multi-tower super high-rise building that subjected to near-fault ground motions. The interactions between each tower makes the internal forces and dynamic responses much complex and totally different from single-tower super high-rise buildings. However, currently, multi-tower buildings in China are usually regarded as multiple single-tower buildings, and then separately designed based on the relevant provisions in seismic code for single-tower buildings. The mutual influence between the towers is almost not taken into account. Seismic response history analysis was carried on a three-tower super high-rise building using finite element method. Various near-fault and far-fault ground motions and high-energy velocity pulses were used as inputs. Through calculation of inter-story drift ratio and maximum displacement, the quantitative seismic fragility analysis was conducted for the main tower and sub-tower structures. The results show that the responses from near-fault ground motions to the structure are much greater than those from far-fault ground motions. The damage probabilities of various damage levels for near-fault ground motions are 12.5% higher than far-fault ground motions averagely. A further analysis reveals that the velocity pulses are the main factor causing structural damage in near-fault ground motions.
Due to friction vibration dampers’ inability to effectively dampen low loads during high-frequency dewatering, drum washing machines vibrated intensively. In order to address this problem, in this paper, a novel type of low-cost non-Newtonian fluid damper is proposed and investigated based on the non-Newtonian fluid shear thinning properties’ effect on vibration suppression during the high-frequency dewatering process of the washing machine. In contrast to other commonly used dampers, the homemade non-Newtonian fluid damper significantly suppresses the growth trend of the apparent elastic coefficient at high frequencies. A systematic investigation of damper structural parameters reveals that smaller gap height, higher piston head number, and more viscous fluid viscosity are adequate for vibration suppression and noise reduction. These results demonstrate that the non-Newtonian fluid damper can produce an excellent vibration-damping effect for the entire washing process of the washing machine, especially for the high-frequency dewatering process. The acceleration attenuation ratio can reach up to 83.49%, the energy attenuation is up to 98.44%, and the noise reduction is up to 10.38 dB.
The evaluation and prediction of the sound quality (SQ) of electric vehicle (EV) powertrains are critical to the overall SQ of EVs. Firstly, a grouping method for noise samples is proposed to achieve rational grouping when SQ evaluations are performed using the grouped paired comparison method and its improvements. Secondly, aiming at the limitations of psychoacoustic parameters in predicting SQ under nonstationary conditions, a SQ prediction model based on the energy features of intrinsic mode functions (IMF) of signals is proposed. Finally, SQ evaluations are conducted, comparing the prediction performance of two SQ models based on energy features and psychoacoustic parameters. The prediction results show that the mean absolute percentage error (MAPE) of the model with energy features is 4.18%, while the MAPE of the model with psychoacoustic parameters is 8.88%, which demonstrates that energy features are superior in predicting the SQ of EV powertrains under acceleration conditions.
Glulam beams connected with steel splints and bolts (GBSBs) are subjected to cyclic reciprocating dynamic loads in practice, which eventually leads to damage accumulation and structure failure. In order to promote the development of GBSBs, an experimental study was carried out, and theoretical analysis of the fatigue behavior of GBSBs was conducted. Three static load test beams and six fatigue test beams were designed and fabricated, taking into account the different stress levels and fatigue limit loads. Theoretical analysis of the data, linear regression analysis, and electron microscopy analysis of the material were carried out. The test results show that the GBSBs have good fatigue properties and that fatigue damage mainly occurs near the loading point. As the number of load cycles increases, the mid-span deflection and strain of the beam increase by a significant amount, and linear degradation of the stiffness occurs. In addition, a linear regression analysis of the amplitude of the fatigue load and the fatigue life was carried out, resulting in a fatigue limit load of 0.5435 Fu.
Aiming at the problem that the crack extension law of deep high-gas coal seams is not clear during blasting and permeability enhancement under the action of ground stress, firstly, according to the propagation and superposition of blasting stress wave, the stress distribution law around the blast hole under the coupling effect of ground stress and blasting was theoretically analyzed. Then, the crack extension characteristics of single-hole blasting under different ground stress conditions were investigated through laboratory tests, on the basis, the numerical simulation was carried out to investigate the crack extension mechanism and the penetration process of double-hole blasting under different lateral stress coefficients, and combined with the ImageJ image recognition software and LS-PrePost software, the effect of ground stress on the degree of crack development was characterized using crack density and extension length as a quantitative index. Finally, based on the results of laboratory test and numerical simulation, the layout scheme of coal seam blasting holes for cracking and permeability enhancement considering the influence of ground stress was proposed. The results of single-hole blasting laboratory test shown that, the ground stress can reduce the tensile stress induced by the blasting load and thus inhibit crack extension. Under the condition of non-hydrostatic ground stress, the tensile stresses orthogonal to the direction of the larger principal stresses were weakened, resulting in the inhibition of crack extension in this direction, causing the cracks to preferentially extend in the direction of higher stresses. The numerical simulation results of double-hole blasting shown that, when the lateral stress coefficient was not 1, the blasting crack expansion was directionality, and the main crack tended to expand in the direction of higher ground stress, resulting in an elliptical shape of the blast crack area, and the direction of the long axis and the larger in-situ stress were consistent. According to the results of laboratory tests and numerical calculations, it was advisable to drill holes along the direction of large ground stress to improve the effect of fracturing and permeability when blasting in deep coal seams. The research results are of great significance for understanding the crack expansion mechanism and optimizing the blast hole layout scheme when blasting for permeability enhancement in deep high-gas coal seams.
This study employs the smoothed particle hydrodynamics-finite element method (SPH-FEM) coupling numerical method to investigate the impact of debris flow on reinforced concrete (RC)-frame buildings. The methodology considers the variables of debris flow depth and velocity and introduces the intensity index IDV (IDV = DV) to evaluate three different levels of debris flow impact intensity. The primary focus of this study is to investigate the dynamic response and failure mechanism of RC-frame buildings under debris flow impact, including structural failure patterns, impact force and column displacement. The results show that under a high-intensity impact, a gradual collapse process of the RC-frame building can be observed, and the damage mode of the frame column reflects shear failure or plastic hinge failure mechanism. First, the longitudinal infill walls are damaged owing to their low out-of-plane flexural capacity; the critical failure intensity index IDV value is approximately 7.5 m2/s. The structure cannot withstand debris flows with an intensity index IDV greater than 16 m2/s, and it is recommended that the peak impact force should not exceed 2100 kN. The impact damage ability of debris flow on buildings mostly originates from the impact force of the frontal debris flow, with the impact force of the debris flow body being approximately 42% lower than that of the debris flow head. Finally, a five-level classification system for evaluating the damage status of buildings is proposed based on the numerical simulation and investigation results of the disaster site.
In real industrial environment,various compound faults may coexist in rolling bearings,and it is usually difficult to acquire sufficient sample data for training.To address this issue,a zero-shot compound fault diagnosis approach was proposed based on envelope spectrum semantic construction.During the training phase,a semantic space and a feature space were established using single fault data.Subsequently,during the recognition phase,compound fault recognition in zero-shot scenarios was realized through the combination of the semantic and feature spaces.Furthermore,recognizing the envelope spectrum's capability in effectively characterizing rolling bearing fault features,the fault signals were preprocessed using envelope spectrum to enhance the bearing fault characteristics.The physical significance of the signal envelope spectrum was leveraged to construct the semantics for both single and compound bearing faults.The experimental results reveal that the proposed model achieves an accuracy of 87.83％in compound fault recognition,outperforming the compared models.
In this paper, the double-lap bolted plate is used to simulate the fully unfolded state of solar panels, and the method of vibration suppression by attaching constrained layer damping (CLD) is studied. Firstly, based on the principle of interlaminar shear deformation, the semi-analytical dynamic model of the double-lap bolted thin plate with partial CLD is established by using Hamilton’s principle. The stress–strain relationship of the CLD is derived. Then, complex spring elements and modified mass are proposed to simulate the interface mechanical behavior and mass effect of the double-lap joint. Moreover, the orthogonal polynomial is introduced as the displacement admissible function. Based on the Evolutionary Structural Optimization (ESO) method, the topology optimization model of the bolted thin plate with CLD is established by taking the maximum sum of the modal loss factors as the optimization objective and the attachment volume as the constraint condition, and processing the optimized results in a convolutional way. After that, a case study is carried out, and the experimental system is established to prove the rationality of the semi-analytical model and attaching CLD to vibration reduction. Finally, the topology optimization is conducted, which verifies that the topology configuration has a better vibration reduction effect.
This research is concentrated on the longitudinal vibration of a tapered pipe pile considering the vertical support of the surrounding soil and construction disturbance. First, the the pile–soil system is partitioned into finite segments in the vertical direction and the Voigt model is applied to simulate the vertical support of the surrounding soil acting on the pile segment. The surrounding soil is divided into finite ring-shaped zones in the radial direction to consider the construction disturbance. Then, the shear complex stiffness at the the pile–soil interface is derived by solving the dynamic equilibrium equation for the soil from the outermost to innermost zone. The displacement impedance at the top of an arbitrary pile segment is obtained by solving the dynamic equilibrium equation for the pile and is combined with the vertical support of the surrounding soil to derive the displacement impedance at the bottom of the upper adjacent segment. Further, the displacement impedance at the pile head is obtained based on the impedance function transfer technique. Finally, the reliability of the proposed solution is verified, followed by a sensitivity analysis concerning the coupling effect of the pile parameters, construction disturbance and the vertical support of the surrounding soil on the displacement impedance of the pile.
The tension cable-supported power transmission structure (TC-PTS) is a new type of power transmission structure suitable for mountainous terrain, and is sensitive to wind load. In this regard, a nonlinear finite element analysis model of wind-induced vibration is proposed for the TC-PTS, and the wind-induced vibration response of the structure is analyzed. Firstly, the tangent stiffness matrix of the three-dimensional truss element for the supporting suspension cable and transmission line, considering the geometric nonlinearity of structures, is derived through the relationship between the element elastic energy and its displacement. Subsequently, the element mass matrix and damping matrix of the supporting suspension cable and transmission line, as well as the element nodal load vector obtained from wind load equivalence, are given. Then, based on the nonlinear finite element theory, the nonlinear dynamic equation of wind-induced vibration is established for the TC-PTS and solved using the Newmark-β method combined with the Newton–Raphson iterative method. Furthermore, the rain-flow counting method and Miner’s linear fatigue cumulative damage theory were used for wind-induced fatigue damage assessment. Finally, a two-span TC-PTS was selected as an example, and the wind-induced nonlinear vibration and fatigue damage assessment were analyzed through the proposed model. The results show that the proposed model has high computational accuracy and efficiency. The first three order vibration modes of the supporting-conductor part of the two-span TC-PTS were antisymmetric vertical bending, symmetric side bending, and antisymmetric side bending. With the increase in wind speed and wind direction angle, the maximum lateral displacement and tension of the supporting suspension cable and transmission line increased, and their degree of increase showed a nonlinear trend. In terms of the wind-induced fatigue analysis results of TC-PTS, the fatigue damage at the end of the supporting-conductor suspension cable was greater than the fatigue damage at its midpoint. Compared to the fatigue damage at the midpoint of the conductor, the fatigue damage at the end of the conductor was less affected by the wind direction angle, and both were more significantly affected by the wind speed.
In order to solve the problems of complex fault feature extraction and fault information representation in single channel, a multi-channel complex fault diagnosis method based on random forest and evidence theory is proposed. Firstly, the complex fault signals are decomposed by wavelet packet transform (WPT) to get the feature vectors, and then the feature data sets of different faults are constructed to divide the single classification model by the random forest algorithm, the integrated classifiers under each channel are synthesized, and an iterative self-updating strategy is proposed to improve the performance of the classifiers. The algorithm is verified by the gearbox experimental platform, and the results show that the method can effectively identify each type of fault contained in the composite fault, and can fully integrate the fault redundancy information of different channels, the accurate diagnosis of gearbox compound fault is realized.
The dynamic response of the hybrid honeycomb sandwich panel under low-speed impact is studied. According to Hamilton's principle and first-order shear deformation theory, the motion equation of the hybrid honeycomb sandwich panel is deduced. Then the Navier method and Duhamel's integral are used to solve the vibration displacement of panels. Besides, the massspring (MS) model is used to calculate the contact force between the honeycomb sandwich panel and the impactor. The results of this model are compared with those of Abaqus and published studies, which verifies the feasibility of the theoretical model in this paper. Based on the developed theoretical model, the influences of the unit cell angle, cell wall length, cell wall thickness, core layer height and impact speed on the dynamic response of sandwich panels have been studied. The results show that under the same low-speed impact, the maximum lateral displacement of hybrid sandwich panels was 11.65% smaller than that of conventional sandwich panels when honeycomb parameter theta = 60 degrees, and was 15.45% when honeycomb parameter beta = 0:3: The energy absorption character of the hybrid honeycomb sandwich panel are better than those of the traditional hexagonal honeycomb sandwich panel and the concave hexagonal honeycomb sandwich panel.
A multiscale modeling framework including microscale, mesoscale and macroscale models, is developed to investigate the low-velocity impact (LVI) and compression after impact (CAI) behaviors of plain woven carbon -fiber-reinforced-polymer (CFRP) composites. Representative volume elements (RVEs) are selected to construct the microscale and mesoscale models, which are further used to compute the effective properties of the carbon -fiber yarn and CFRP composites. An equivalent cross-ply laminate (ECPL) model is used to simplify the woven architecture via a local homogenization approach. The macroscale model of plain woven CFRP composites is established by extending the ECPL model. The LVI and CAI behaviors of CFRP composites are predicted for various impact energy cases. Finally, the corresponding LVI and CAI tests have been performed on plain woven CFRP composites, and the experimental measurements agree well with the numerical simulations, indicating the reliability of the multiscale modeling framework. Importantly, both the experimental and numerical results reveal that the impact damages, especially the intralaminar damages, are prone to cause the decrease of the residual compressive strength of impacted plain woven composites.
The hybrid simulation (HS) is a cost-effective and promising method for investigating the seismic performance of structures. This paper proposes a model updating method for HS to improve incomplete boundary conditions and model error, and develops criteria to select the updated parameters. First, an actual HS model updating is conducted to verify the effectiveness of uniform design as a parameter estimation method. This experiment shows that parameter sensitivity has a significant relationship with the update effect. Then, the Sobol global sensitivity analysis (GSA) method is applied to the HS model updating to obtain the sensitivity indices of parameters that change with time, which provides a sound basis for parameter selection and the determination of the search range. Following this, a whole-structure module for dynamic time history analysis is proposed to improve the boundary conditions, simplify the implementation, and refine the numerical models. The errors in six boundary conditions of the traditional HS are then analyzed. The proposed method of model updating based on GSA is then obtained by integrating the above ideas. In the case of multiple inputs of ground motion, four strategies are developed to verify the effectiveness of the method. The results of a total of 216 numerical cases under different working conditions show that the proposed method can improve the accuracy of HSs and the identified parameters.
The strict and high-standard requirements for the safety and stability of major engineering systems make it a tough challenge for large-scale finite element modal analysis. At the same time, realizing the systematic analysis of the entire large structure of these engineering systems is extremely meaningful in practice. This article proposes a multilevel hierarchical parallel algorithm for large-scale finite element modal analysis to reduce the parallel computational efficiency loss when using heterogeneous multicore distributed storage computers in solving large-scale finite element modal analysis. Based on two-level partitioning and four-transformation strategies, the proposed algorithm not only improves the memory access rate through the sparsely distributed storage of a large amount of data but also reduces the solution time by reducing the scale of the generalized characteristic equation (GCEs). Moreover, a multilevel hierarchical parallelization approach is introduced during the computational procedure to enable the separation of the communication of inter-nodes, intra-nodes, heterogeneous core groups (HCGs), and inside HCGs through mapping computing tasks to various hardware layers. This method can efficiently achieve load balancing at different layers and significantly improve the communication rate through hierarchical communication. Therefore, it can enhance the efficiency of parallel computing of large-scale finite element modal analysis by fully exploiting the architecture characteristics of heterogeneous multicore clusters. Finally, typical numerical experiments were used to validate the correctness and efficiency of the proposed method. Then a parallel modal analysis example of the cross-river tunnel with over ten million degrees of freedom (DOFs) was performed, and ten-thousand core processors were applied to verify the feasibility of the algorithm.
To address the impact of rivet arrangement on the strengths of riveted lap joints, the failure modes and failure mechanisms of riveted lap joints were first studied using finite element analysis software. Next, the effects of the number of rivets, rivet rows, rivet arrangement, and row spacing on the lap joint strength were studied using the peak load as the evaluation index. Then, we proposed the concept of line load density to solve the problem that a varying rivet spacing and rivet edge distance will change the width of the sheet and thus the maximum load capacity, which is used as an index to study the effect of rivet spacing and rivet edge distance on the lap strength. Finally, a spring–mass model was developed to study the forces present in multi-row riveting. The model could accurately calculate the force–displacement curves during tensioning. The results show that when multiple rivet rows are used, higher stress concentrations cause the plate to first fracture at an outer rivet row with more rivets; therefore, the rivets should be arranged such that there are more rivets in the middle and fewer rivets on both sides. When the total rivet strength is greater than the remaining strength of the plate, the numbers of rivets and rivet rows have limited effects on the lap joint strength; however, this primarily affects the damaged form of the lap joint member. When the rivet spacing is less than 5d, the lap strength increases with increases in the rivet spacing, and when the rivet spacing is greater than 5d, the lap strength does not change significantly with increases in the rivet spacing. When the rivet edge distance is less than 3d, the lap joint strength increases with increases in the rivet edge distance, and when the rivet edge distance is greater than 3d, it has a limited effect on the lap joint strength. The rivet row spacing has no significant effect on the lap joint strength. The results of this study are valuable for improving the strengths of riveted structures in aircraft.
通过引入多轴有效硬化函数和S型率相关强度准则,改进了混凝土损伤塑性(concrete damage plasticity,CDP)模型,称为S-CDP模型,能够更加合理地反映混凝土材料的应变率效应和三维塑性变形行为.基于S-CDP模型建立了大岗山拱坝的率相关数值模型.利用所建的率相关数值模型,分析了地震作用下坝体混凝土的应变率分布规律、动态增长因子的变化规律以及混凝土应变率效应对坝体动力响应的影响.结果表明,S-CDP模型能够合理反映受拉区混凝土材料的率效应,在地面峰值加速度为0.557g,0.663g,0.836g的地震动荷载作用下,拱坝坝体混凝土的动强度增长最多能达到23％,然而并不能保证坝体混凝土的动强度始终提高20％及以上.在水工建筑物抗震设计时,若将混凝土的动强度提高固定的20％,可能会造成计算的损伤结果与实际的损伤有所偏差,动强度提高固定的20％计算得到的损伤结果相较于该文中采用S-CDP模型计算得到的损伤结果偏大.因此在水工建筑物抗震设计时,推荐选用合适的混凝土率相关本构模型进行计算,以尽可能的保证计算的精确度.
