Load Moment Research Articles

Terminal Voltage Prediction of Distribution and Substation Based on Spatial-Temporal Distribution Characteristics of the Station Load

A terminal voltage prediction method based on the spatial-temporal distribution characteristics of the load in the substation area is proposed. Considering that the power flow and load belong to the influence factors of the terminal voltage, the power flow analysis method based on the parameters and power distribution of the low-voltage line is used. After the general model of the low-voltage line is built according to the spatial distribution characteristics of the load in the substation area. Combined with the injected power of the parent node of the terminal node in the constructed line model, the terminal node voltage is obtained; After the load information of different time periods in the station area is predicted by the distribution and substation load prediction method based on wavelet-clustering, the voltage analysis results under the change of power flow and load moment are taken as the prediction samples of the terminal voltage prediction method in the station area based on the fusion of power flow calculation and load forecasting. Based on the low-voltage limit, the deep residual network is used to realize the state prediction of whether the terminal voltage is normal or not. The test shows that the prediction result of this method for the terminal voltage of distribution and substation in a certain area is in line with the actual situation and has the ability to predict the terminal voltage of distribution and substation.

Innovative bolted-steel box for seismic-resistant dry-precast concrete beam-column connection

Currently, many buildings are constructed with precast concrete methods. However, they still use the cast in-situ method, especially for the beam and column connection system where there are some obstacles in the casting process and the possibility of installing the reinforcement bars on site not following the design. Hence, there is potential for structural failure in that part of the connection. To reduce the connection constraints, it is proposed that the method of connecting precast concrete with an innovative connection system that is simple, lightweight, fast in the manufacturing process, can be constructed quickly and effectively on-site, and easily meets the specifications of connection quality. This proposed type of connection is a dry joint type that only uses bolts for the connection system with steel box components. This study will prove that the dry joint system can receive the moment and shear load due to earthquakes still in the elastic phase, not experiencing plasticity. The concept of connection planning does not change the concept of the Special Moment Frame System which applies the concept of Strong Column Weak Beam and Plastic Hinges. The connection is ensured in strong conditions, there is no yielding and damage at the time of a large earthquake, so the failure is not in the connection but occurs in the precast concrete block element that is at the end of the beam outside the planned connection in flexural failure with ductile behavior, not shear failure.

Predicting equation of quasi-static and dynamic failures of steel columns under fire

Steel columns may fail in dynamic or quasi-static types under fire. The quasi-static failure of steel column could be considered as gradual column removal in the collapse assessment of structures, while the dynamic failure cannot. Hence, it is meaningful if the failure type of the column could be predicted. To identify the failure types of box-section steel columns under fire simply, this paper adopted a validated numerical model to conduct a systematic parametric analysis. The critical axial restraint stiffness ratio (βl,cr), which is used to predict the failure type of columns under fire conditions, is the main focus. Firstly, the values of βl,cr of columns with a representative section were studied, with various slenderness ratios and load ratios being considered. Then, the effects of width-thickness ratio, length–width ratio, sectional size, and bending moment load ratio on βl,cr were studied. The results indicate that βl,cr of columns with the representative section increases with the rise of the load ratio, and increases sharply after the load ratio exceeds a certain level. Besides, the dynamic effect during column buckling and βl,cr both increase with the rise of either the width-thickness ratio, length–width ratio, or sectional size. Moreover, based on the results, a predicting equation for βl,cr of box-section steel columns was proposed. The failure type of a steel column under fire can be easily predicted by the proposed equation. Finally, the proposed equation was verified by an additional series of case studies, and good agreement was achieved.

Enhancing the Life Cycle of the Jack up Structure by Applying Alternative Foundation Methodologies in Geotechnical Engineering

A jack-up structure is a bottom-mounted floating unit having an adjustable hull and movable legs. Particular jack-up structures are more susceptible to hazards under environmental loads during their operation and life cycle in the ocean. Authors' attempts here to enhance its life cycle and sustainability in shallow to deep waters by correctly accessing soil behaviour and predicting its load carrying capacity. Here the numerical analysis of the substructure has been attempted. Simulation of load-deformation behavior under axial compression has been carried out for advancing research. The entire study has been carried out using three-dimensional finite element-based software Plaxis 3D A.E. 2017. The geometrical variation of substructure spud can have an inverted spud at the centre bottom from 120 0 to 180 0 has been studied for knowing behaviour under axial compression, axial tension, and lateral forces. The simulated numerical model is used to develop empirical expressions for axial capacities estimation. The numerical analysis results indicate that spud can have an inverted angle of cone 130 0 is most beneficial under the static combined vertical, moment, and horizontal loading (3D loading) in marine clay. The axial load carrying capacities in compression, tension, and lateral loading follow the same sequence in ascending order from 180 0 ,175 0 , 150 0 , 130 0 and highest in 120 0 . Stiffness and undrained shear strength of soft clay contribute more than the diameter of the spud and embedment depth in compression and tension.

Finite Element Analysis and Validation of Segments C2-C7 of the Cervical Spine

As an important part of the human spine, the cervical spine has a complex structure and easily suffers from diseases. Analysis of the biomechanical mechanism of cervical spine structure using the finite element model is not only helpful for the diagnosis, treatment and prevention of cervical spine diseases but also has positive significance for the performance evaluation of cervical spine implants. In this paper, a method of establishing a cervical C2-C7 finite element model based on CT image data is studied. Through the preprocessing of cervical CT images, the C2-C7 three-dimensional finite element model of the cervical spine was established. The pure moment loads of 0.33 Nm, 0.5 Nm, 1 Nm, 1.5 Nm and 2 Nm were applied to simulate flexion/extension, and the moment of 1 Nm was used to simulate the left and right lateral bending and axial rotation of the cervical spine. The relative range of motion (ROM) between each vertebral body was calculated. At the same time, the stress on some segments under axial load was analyzed. The results were basically consistent with the experimental data of in vitro studies, which verified the validity of the model.

Numerical Study on Pile Group Effect and Carrying Capacity of Four-Barreled Suction Pile Foundation under V-H-M Combined Loading Conditions

Multi-barreled composite foundations are generally used in offshore oil platform structure. However, there is still a lack of theoretical analyses and experimental research. This paper presents the results of a three-dimensional finite element analysis of a four-barreled suction pile foundation in heterogeneous clay foundation. The pile group effect and carrying capacity are numerically simulated. The effects of different pile embedment depths, pile spacings and non-uniformity coefficients of clay on the pile group effect are studied. Considering the changes in the foundation carrying capacity under vertical, horizontal and bending moment coupling loads, the foundation carrying capacity envelopes under horizontal and moment (H-M) and vertical, horizontal and moment (V-H-M) loading modes are drawn. The results show that pile spacing and embedment depth have great influence on the pile group effect. The bearing capacity envelope of foundations under V-H-M loading mode is greatly affected by vertical load V. This can provide a reference for the selection of pile spacing and embedded depth in practical engineering design. Furthermore, the stability of foundations can be evaluated according to the relative relationship between design load and failure envelope.

Biomechanical analysis of single- and double-level cervical disc arthroplasty using finite element modeling.

Recently, many different types of artificial discs have been introduced to persevere the biomechanical behavior of the cervical spine. This study compares the biomechanical behavior of single- and double-level cervical disc arthroplasty, that is "Prestige LP and Mobi-C" on the index and adjacent segment. A three-dimension finite element model of C2-C7 was developed and validated. In single-level prostheses, the Prestige LP or Mobi-C was implanted in the segment C5-C6, while the double-level arthroplasty was integrated at both segments C4-C5 and C5-C6 in the FE model. The intact FE and prosthesis-modified models were constrained from the inferior endplate of the vertebra C7 and applied a compressive load of 73.6 N with a moment load of 1 Nm on the odontoid process of the vertebra C2 to produce flexion/extension, lateral bending, and axial rotation. The prosthesis-modified model's range of motion and intradiscal pressure were determined and compared to the intact model. Also examined the impact of the prostheses on the stress at the bone-implant interface. The range of motion of the implanted segments in both single- and double-levels arthroplasty was increased while that of the adjacent segment of implanted segments decreased. The intradiscal pressure in both levels of arthroplasty was greater than in the intact model. In conclusion, Mobi-C's cervical prostheses could better preserve the normal range of motion and maintain intradiscal pressure than the Prestige LP.

Capacity of spudcan foundation on dense sand overlying clay under combined loading

The evaluation of spudcan foundation capacity under combined vertical, horizontal and moment loading is critical for the site-specific assessment of jack-up rigs. However, the investigation on the behavior of a spudcan on the surface of a sand layer overlying clay under combined loading is limited. This paper reports the results from a series of finite element analyses conducted to explore the failure envelope of spudcan on dense sand overlying clay before punch-through, considering the effects of the preload level on spudcan, the thickness ratio and the relative density of sand, and the underlying clay strength through parametric study. The numerical results provide insights that when the sand layer is sufficiently thick, the failure envelope expands with the increase of vertical load level, leading to higher horizontal and moment capacities; however, for the spudcan on a relatively thin sand layer, the horizontal and moment capacity may decline with rising vertical load level, resulting in eccentricity and shrinkage of the failure envelope. New design formulas for the failure envelope are proposed covering a comprehensive range of soil parameters and layer geometries of practical interest, which facilitates their general application in the site-specific assessment of the jack-up platforms.

Exact Winkler Solution for Laterally Loaded Piles in Inhomogeneous Soil

A novel exact analytical solution is derived for the equation y(4)+xny=0 in the region x≥0, which is important for the analysis of piles in soil with stiffness varying with depth. To date, exact solutions for long piles are available only for the cases where n=−4, 0, and 1. For other values of the exponent n, solutions have formerly been obtained numerically, mainly by the finite-difference method or approximate analytical solutions. An inherent difficulty in obtaining solutions for long beams (which are used to model flexible piles) lies in the inability to isolate the regular, converging part of the solution over the singular part that diverges with increasing x. In this paper, an exact solution is derived for n>−4, focusing on the important case of semi-infinite beams. Key aspects of the problem such as the stiffness and flexibility matrices at the pile head, and the peak bending moments due to eccentrically acting lateral loads, are discussed. A novel approach for deriving Winkler spring moduli for combined force and moment loading is proposed and shown to provide good agreement with rigorous numerical continuum results.

Design of steel transmission pole base plates using yield line method

Steel transmission poles are widely used for their strength, ease of construction, small footprint, and aesthetic appearance. These poles can be either directly embedded into their foundations or supported on based plates which are connected to the reinforced concrete footings via group of anchor bolts.There are few available published methods for the analysis and design of this type of base plate connection. These methods are not widely used in the industry as they are either complex, lack solid theoretical background, or yield results that are not consistent with manufacturer's time-tested proprietary design methods. Therefore, there is a need for an accurate method suitable for technical or design office for designing these connections when subjected to axial loads, bending moments or the combined effect of both.This paper presents a numerical study performed on the base plates of polygonal steel poles that are supported directly on anchor bolts with levelling nuts and subjected to bending moment and axial load. The Finite Element (FE) analysis part of the work is carried out using ADINA software and the results obtained from the analyses are compared with published experimental results from which it is concluded that the finite element model can accurately predict the behaviour of these connections.Parametric investigation is then conducted to gain more insight into the behaviour of these base plate connections and to use the obtained data the validation of the proposed design method. The parametric investigation covered the behaviour of these connections under pure axial load and pure bending moment while the varying parameters considered included number of shaft sides, base plate thickness, number of anchor bolts and anchor bolt diameter.Design formulae based on the yield line theory are then proposed and a comparison between the yield loads calculated using the proposed expressions and finite element results is presented. The yield loads resulting from using the proposed design method agreed with the finite element results with a maximum calculated difference of 13%.

Effect of relative phase of periodic loading on frictionally constrained joints

This paper considers a two-dimensional frictionally constrained joint to investigate the interfacial characteristics under periodic loadings with phase variations. Joints are pressed in contact by normal pressure, subjecting to tangential loading and bending moment. The tendency of contact behavior at the steady-state is investigated, subjected to various phase differences between the bending moment and the tangential loading. Total energy dissipation per cycle is obtained at steady-state to examine the overall frictional damping from the joint interface. It is found that friction damping is dominant during tensile loading, and the energy dissipates the most when the phase difference is near π / 2.

Simultaneous measurement of the moment of inertia and braking torque of electric motors applying additional inertia

This paper presents a method for the simultaneous measurement of the moment of inertia and braking torque of the rotor of electric motors. The procedure is based on retardation tests on the motor applying additional loads on its rotor with different moments of inertia but equal masses. The equal masses provide equal braking torques in the supporting bearings. Besides the detailed description of the experimental setup and method – a procedure for determining the optimal values of the loading moments of inertia is also presented. At these optimal values, the errors of the experimentally determined moment of inertia and braking torques are minimal. Additionally, the effect of the temperature change of the bearings on the accuracy and precision of the method is also analyzed and discussed. Finally, the method's experimentally validated accuracy and precision are reported, and measurement results on an induction motor are presented as an example.

A comparative analysis of existing models and a new pushover analysis model of reinforced concrete sections

Pushover analysis is mainly carried out using the concentrated plasticity model whereby when a point reaches yield, a hinge is placed at that point. The other is the yielded block spread plasticity model, whereby when a point reaches yield, an elastic sub-element of the beam is replaced by a yielded sub-element having a reduced cross-section and second moment of area. Both of these models ignore cracking. This study aims at giving an insight into the effects of considering cracking during modelling on the accuracy of estimating deformations in reinforced concrete (RC) structures during pushover analysis by proposing a spread cracking and yielding block model. The proposed model introduces a cracked sub-element to account for the gradual spread of cracking in the beam. A single-storey RC frame is used because it doesn’t pose the challenge of lateral load distribution. A comparison between the proposed model and the existing models shows an increment in the accuracy of the rotational, displacement, moment and lateral load capacities of 63.64%, 56.86%, 64.33% and 55.56% respectively.Experimental results show that all theoretical models underestimate the ultimate floor displacements and lateral load capacities. The proposed model, however, has better accuracy on both fronts than both existing theoretical models.

Biomechanical evaluation of a novel repair strategy for intervertebral disc herniation in an ovine lumbar spine model.

Following herniation of the intervertebral disc, there is a need for advanced surgical strategies to protect the diseased tissue from further herniation and to minimize further degeneration. Accordingly, a novel tissue engineered implant for annulus fibrosus (AF) repair was fabricated via three-dimensional fiber deposition and evaluated in a large animal model. Specifically, lumbar spine kinetics were assessed for eight (n = 8) cadaveric ovine lumbar spines in three pure moment loading settings (flexion-extension, lateral bending, and axial rotation) and three clinical conditions (intact, with a defect in the AF, and with the defect treated using the AF repair implant). In ex vivo testing, seven of the fifteen evaluated biomechanical measures were significantly altered by the defect. In each of these cases, the treated spine more closely approximated the intact biomechanics and four of these cases were also significantly different to the defect. The same spinal kinetics were also assessed in a preliminary in vivo study of three (n = 3) ovine lumbar spines 12weeks post-implantation. Similar to the ex vivo results, functional efficacy of the treatment was demonstrated as compared to the defect model at 12weeks post-implantation. These promising results motivate a future large animal study cohort which will establish statistical power of these results further elucidate the observed outcomes, and provide a platform for clinical translation of this novel AF repair patch strategy. Ultimately, the developed approach to AF repair holds the potential to maintain the long-term biomechanical function of the spine and prevent symptomatic re-herniation.

Speed-Sensorless DTC of BLDC Motor with EKF-based Estimator Capable of Load Torque Estimation for Electric Vehicle

This study presents the simulation of brushless DC (BLDC) motor control in MATLAB/Simulink simulation environment with model-based and direct torque control (DTC) method with extended kalman filter (EKF). In this study, a control method based on DTC method is tested to control a nonlinear BLDC motor with extended kalman filter. In this method, an accurate control can be made thanks to the load moment estimation, which is not found in the literature. As a result of the tests have carried out at low and high speeds, it is concluded that the system can lead to real-time systems.

Finite element analysis of gear of full-rotating propeller steering assembly

In order to ensure that the gear of the steering component of the full-rotation propeller meets the limit of bearing capacity and normal use under the action of moment load, this paper takes a steering propeller device as the research object, establishes the finite element model of the gear of the steering component under normal and braking conditions, carries out stress bending strength analysis, and carries out modal analysis. It is verified that the gear of the steering assembly meets the safety requirements, which provides a reference for the design of the steering device.

Selecting a Cervical Disc Arthroplasty: Biomechanical Considerations

Introduction: Cervical disc arthroplasty (CDA) is for motion preservation, and may replace anterior cervical discectomy and fusion (ACDF) for treatment of radiculopathy. Biomaterials/designs of CDA’s are evolving. ROM, Return-To-Duty, CDA’s risks in military personnel has not been addressed. This finite element (FEM) study of 5 CDA’s and ACDF was to optimize treatment for cervical spondylosis in military populations. Methods: Validated C2-T1 FEM, spine simulated. Intact spine modified at C5-C6 to simulate the ACDF and 5 types of CDA’s: 1 metal-on-metal (MOM) and 3 metal-on-polymer (MOP). Models fixed T1, load applied at C2. Follower load 75 N, bending moment 2 Nm under flexion, extension applied. Hybrid loading protocol using variable moment loading applied. Bending moment varied until ACDF, MOM and MOP models responded with same total C3-C7 ROM. The facet force (FF) and ROM were obtained at index and adjacent levels under each loading mode, and intradiscal pressures (IDP) determined. Results: Difference in CDA behavior of MOP and MOM was noted. The MOP had highest ROM in flexion, extension and highest FF in extension at index level. Conversely, MOM demonstrated highest adjacent IDP. Conclusion: ACDF demonstrate increased ROM all levels. ACDF minimizes ROM and FF at index but increases ROM, and IDP at adjacent levels. CDA’s kinematic behavior was reflective more on material type than design. For military pilots with CDA exposed to higher forces, slightly stiffer CDA - MOP may be preferable to minimize potential anterior extrusion. Military with “normal” activities, more mobile MOP CDA implants may be preferred.

A formula for estimating the buckling capacity of corroded tubular members

PurposeSeveral experimental and numerical studies were performed in the past to estimate buckling capacity of corroded tubular members. However, the effect of initial imperfections has not been properly considered in most of these earlier proposed formulas. Therefore, the main objective of this paper is to propose an accurate analytical formula to determine the buckling capacity of patched corroded tubular members.Design/methodology/approachTubular members with initial geometrical imperfections can be regarded as beam-columns because of the combination of axial load and bending moment. The proposed formula is derived for a rectangular corrosion patch. The proposed formula is verified with results from finite element analysis of corroded tubular members and experimental results. The formula is also applied to an existing offshore jacket structure to highlight its significance and applicability. It is found that the buckling capacity of jacket members in splash zone reduces significantly with ageing. This reduction is around 29 and 14% for the selected brace and leg member respectively, during the design life. Finally, it is concluded that corrosion reduces the buckling capacity significantly and the proposed formula can be easily applied by practicing engineers to give an accurate and slightly conservative estimate the remaining buckling capacity.FindingsThe main finding is the new formula which accurately and conservatively estimate the buckling capacity of corroded tubular members. The proposed formula considers the secondary effect of both initial geometrical imperfections and shifting of centroid because of corrosion.Originality/valueThe proposed new formula is unique and original in that it considers both secondary effects from geometrical imperfections, reduction of cross-section from corrosion wastage and shifting of centroid because of corrosion. Finally, it is concluded that corrosion reduces the buckling capacity significantly and the proposed formula can be easily applied by practicing engineers to conservatively estimate the remaining buckling capacity and verify if further, more advanced estimations are needed.

STUDY INTO THE SIGNIFICANCE OF INDIVIDUAL ELEMENTS IN A PILED-RAFT FOUNDATION

Introduction . The prospects of using piled-raft foundations to support the columns of frame buildings and civil engineering works are examined. Aim . To determine the significance and role of individual elements in a piled-raft foundation and its underlying soil to achieve the maximum load capacity. Materials and methods . In order to achieve the stated aim, a series of theoretical numerical studies into horizontally loaded piled-raft foundations was conducted. Here, three-level numerical studies were used to determine the effect of various factors on the load capacity of piled-raft foundations under horizontal and moment loading. The following factors were considered in this work: coefficient of soil reaction around the column pedestal k u ; coefficient of near-pile soil reaction k p ; transverse dimension of the column pedestal d u ; pedestal height l u ; inclination angle of the pile to the vertical α P . The significance of each factor was assessed in terms of the column pedestal displacement at the soil surface level, which is described by a quadratic polynomial in five variables. Results . The impact on foundation resistance to horizontal loading can be determined by analyzing the absolute values of polynomial coefficients and the extent to which the considered factors affect the horizontal pedestal displacement in piled-raft foundations under horizontal and moment loading at the soil surface level. It is established that the most significant factors contributing to the foundation resistance to horizontal loading include the coefficient of soil reaction around the column pedestal k u and the transverse dimension of the column pedestal d u (increasing the foundation resistance to horizontal loading by 60% and 35%, respectively). The other factors have a significantly lower impact. Conclusions . It is shown that numerical theoretical studies into horizontally loaded piled-raft foundations reveal the significance and role of its individual elements and underlying soil, as well as justifying the values of factors affecting the load capacity of foundations.

A combined experimental and numerical study on aerodynamic load reduction for a swept wing by using jets

This paper presents a combined experimental and numerical investigation on aerodynamic load reduction through steady blowing on the suction surface of a swept wing. In the experiment, a swept wing with an array of jet exit holes near the wing tip was studied in a low-speed wind tunnel. Numerical studies based on solving the Reynolds-averaged Navier-Stokes equations provide further insight into aerodynamic load and bending moment reduction and the associated flow physics caused by the surface jets with various jet parameters, including blowing direction, blowing strength and jet velocity distribution. It is found that the upstream blowing causes a much larger reduction in both lift and bending moment than that caused by the normal blowing. Both the experiment and numerical simulations confirm that the aerodynamic load reduction increases as the jet momentum increases. It is also found that the linear jet velocity distribution, with the lowest blowing velocity at the outer end (y/b=0.98) of jets region and the highest blowing velocity at the inner end (y/b=0.755), achieves the maximum aerodynamic load reduction among the six different distributions studied. In addition, three key flow mechanisms associated with aerodynamic load reduction are identified, including the pressure rise on the suction surface caused by the flow separation, the wingspan shortening effect caused by the large drop in lift in the tip region of a three-dimensional swept wing as well as the jet reaction force.