Force Of Rod Research Articles

Study on Design and Deformation Law of Pile-Anchor Support System in Deep Foundation Pit

In this study, a deep foundation pit project of Nanlishi Road in the Xicheng District of Beijing was taken as the engineering background. Based on the monitoring method of that project and referring to its design scheme principle, this study applied advanced monitoring technology methods such as anchor axial force and deep horizontal displacement monitoring. The mechanism of pile–soil interaction, the stress change and deformation law of the three-pile and two-anchor support systems of deep foundation pits, and the stability of deep foundation pit support in an anhydrous sandy pebble stratum, were studied in depth. Results show: The axial force of the anchor rod had great loss in the early stage of prestressed tension locking; with the deepening of foundation pit excavation, the lateral pressure of stratum increased gradually, and the prestress of the anchor increased until the end of excavation, where it tended to be stable; the maximum horizontal displacement of the pile was smaller than the design value, and the maximum horizontal displacement was not at the top of the pile; the axial force of the prestressed anchor varied with the formation pressure and surrounding load; the tension of the lower anchor had a certain influence on the axial force of the upper anchor. Except for the east side of the foundation pit, the anchors of the first layer were all stabilized at about 140 kN, and the anchors of the second layer were stabilized at about 150 kN. The third row of anchors on the north side was stable at around 170 kN. By analyzing the variation law of stress and deformation of the supporting structure of the foundation pit, the timeliness of the data during the construction process was improved, and a reference is provided for the informatization construction of related working conditions.

Analysis of Deep Foundation Pit Pile-Anchor Supporting System Based on FLAC3D

Relying on a deep foundation pit project in Beijing, using FLAC3D three-dimensional finite-difference software simulation combined with displacement monitoring data verification method, the deep foundation pit excavation and three-pile and two-anchor rod support system in anhydrous sand pebble stratum are systematically analyzed, and summed up the variation law of formation stress, internal force of soil nail, axial force of bolt, stress and displacement of pile in the process of excavation and support of deep foundation pit. The results show that during the excavation of the foundation pit, the maximum horizontal displacement of the sidewall is not at the top of the pile and the top of the slope but at a certain distance below the top of the pile. The axial force of the anchor rod is unevenly distributed along the length direction, the axial force of the free section is equal, the axial force of the anchoring section decreases in turn, and the prestress of the anchor rod spreads to the anchoring section after tensioning and locking. The soil-nailed wall is a passive force-bearing system, the force is small during the excavation and support process, and the axial force distribution along the length direction is large in the middle and small at the two ends. By analyzing the variation law of stress and deformation, the timeliness of the data in the construction process is improved, and an effective and reasonable case reference is provided for the informatization construction of simulated relevant working conditions.

Model test study on static performance of rib-patterned small rise-span ratio suspend-dome structure

To investigate the distribution characteristics of prestressing force and static characteristics of the rib-patterned small rise-span ratio suspend-dome structure, a 1:20 scaled model of the Lanzhou Olympic Gymnasium roof structure was established. During to the small-scale ratio model with dense nodes, according to the principle of constant structural stiffness, a multi-node synchronous loading device was designed. The construction tensile loading test and multi-stage static loading test were carried out. The axial force of rods, vertical displacement of nodes, and radial displacement of supports for the model with initial geometric imperfection under 11 load cases were tested. Test results were used to validate and then refine the numerical simulation using ABAQUS. The study shows that a multi-node synchronous loading device dramatically improved the loading efficiency and satisfied the accuracy requirement of the test. The test results were in good agreement with the simulated results, which verified the correctness of the finite element modelling method, the accuracy of the test method, and the rationality of the measuring point arrangement. The small rise-span ratio suspend-dome structure with a rib-patterned has good elasticity at a low load level. The full-span arrangement of the live load is the most unfavorable load case of the structure. The outer loop cable bearing capacity exhibited a higher proportion. The third ring rod was found to sustain the highest load, the outer ring rod is more sensitive to load, and the fourth circle node was found to have the largest vertical displacement in the model. The change of support displacement in practical engineering should not be neglected.

Формулы для расчета прогиба плоской распорной фермы моста с произвольным числом панелей

The problem of finding an analytical solution to the problem of deflection of a planar model of a bridge truss with two fixed hinged supports is posed. Formulas are derived for the dependence of deflection, reactions of supports and forces in characteristic rods on the number of panels in the structure. Maple computer mathematics operators are used. The deflection is sought by the Maxwell-Mohr formula. A series of individual solutions obtained for trusses with a successively increasing number of panels are generalized to an arbitrary number of panels. A picture of the distribution of forces on the truss rods is obtained. It is shown that the change of force signs in the truss chords does not depend on its geometrical parameters, but depends only on the number of panels.

Interactions of Foundation Pit on the Underlying Adjacent Existing Underground Structures

The influence of foundation pit excavation on deformation and stability of the supporting structure of underlying adjacent existing tunnel is a comprehensive geotechnical engineering problem, including unloading effect of foundation pit excavation and the coupling effect of deformation of the tunnel surrounding rock and supporting structure. Using numerical calculation methods, this paper changes the different excavation depths and widths of foundation pit and discusses the evolution law about force and deformation of tunnel supporting structure, and the changing relationship of the axial force of tunnel anchor with the distance between foundation pit and tunnel is obtained and compares the influence of different excavation way of foundation pit on the axial force of anchor rod near the existing tunnel. It is found that with the increase of distance between foundation pit and tunnel, the axial force of anchor rod at the top of tunnel under the foundation pit entirely symbolizes a trend of increases first and then decreases, the axial force of the leftmost anchor rod changes from pressure to tension, then decreases gradually. When the foundation pit depth increases, the axial force of the anchor rod at the top of the tunnel increases, the axial force of the leftmost anchor rod decreases, and the width of foundation pit absolutely has little effect on the axial force of the leftmost and the top tunnel.

Pulling actuation enabled by harnessing the torsional instability of hyperelastic soft rods

Torsion applied to a slender soft rod can cause the rod to lose its stability and knot — a phenomenon widely referred to as the torsional instability of elastic rods. Previous studies mainly focus on predicting the critical load, at which the torsional instability occurs, and investigating the post-instability deformation of the rod. Thus far, little attention, if any, has been paid to exploiting the torsional instability of hyperelastic soft rods to realize functions such as actuation. In this work, we study the twisting process of hyperelastic soft rods through dimensional analysis and explicit finite element method, and find that the axial pulling force of the soft rod suddenly rises drastically immediately after the torsional instability occurs. Further simulations demonstrate that the sharply increased pulling force can be utilized to achieve a large-stroke pulling actuation. The influence of the rod geometry and material properties of the rod on the actuation forces/strains is also discussed. The results of this work are expected to guide the design of novel actuators based on the torsional instability of hyperelastic soft rods.

ON THE OPTIMAL POSITION OF THE INTERMEDIATE SUPPORT OF THE COMPRESSED THREE-SPAN ROD AND ITS QUALITATIVE FEATURES

The optimization problem is considered, which consists in maximizing the main critical force of a three-span longitudinally compressed rod supported at the ends on absolutely rigid hinge supports due to the optimal choice of the position of one of the intermediate supports. It is known that in many cases this position is a node of the buckling form, which corresponds to the second critical force in the spectrum of the two-span rod formed by removing the moving support. A range of recent studies have described cases where the maximum critical force is reached at other positions. This, in particular, occurs at a finite stiffness of one or both end supports of the rod. The proposed work seeks the optimal position of the rigid intermediate support, provided that the second intermediate support has a finite stiffness and a fixed position. The compressive force is assumed to be constant along the length of the rod, bending stiffness can vary according to the length of the rod according to arbitrary way. It is established that under certain conditions the solution of this problem can be reduced to the solution of another, previously studied problem, which seeks the maximum critical force of a two-span rod by changing its length, at which some segment of the rod adds or removes at one end of the rod with the transfer of the corresponding hinged support at the end of the newly created rod. The paper founds and describes the characteristic qualitative features of the buckling forms, which correspond to the maximum of the main critical force, in particular the absence of deformation of the bending of the end span adjacent to the moving support. The limitations in which the approach proposed in the paper leads to the determination of the desired optimal position of the movable support are studied. The results are obtained mainly on the basis of the systematic use of qualitative methods and allow to obtain qualitative estimates for the localization of the moving support and the value of the corresponding critical force. An example illustrating the proposed approach and the reliability of the results of its application are considered.

Numerical simulation of pressure force for control rod guide tube in PWR

In nuclear power plants (PWR), the rod cluster control assemblies (RCCAs) can be damaged by impacted-sliding wear due to flow induced vibrations, which leads to specific wear of the contact surface. A detailed numerical simulation of the flow field and pressure force in the control rod (CR) guide tube was carried out based on the CFD method in this paper. Then a new method was proposed to transfer the surface pressure filed to the pressure force on the control rods. The results show that the pressure force on the inner rods that located at the height of second guide card are higher than the others. At different positions of the guide cards, the pressure force of internal control rod CR1 is higher than CR2. The pressure force of the external control rod CR5 is lower than CR3 and CR4. For the same control rods, the pressure force at the height of guide card 2 is higher than guide card 1 and guide card 3. At the same time, the pressure force of control rod 1 is the highest than other rods that means the control rod 1 may result in larger potential displacement, on the contrary, the control rod 5 is likely to have a smaller potential displacement.

Viscoelastic Representation of the Operation of Sucker Rod Pumps

The issues of leakage with respect to the clearance between the pump plunger outer surface and the pump barrel inner surface and other operational conditions have been revisited in this paper. Both Poiseuille flow rate due to the pressure difference and Couette flow rate due to the plunger motion have been considered. The purpose of this study is to explore the possibility of representing the entire downhole pump system with a simple viscoelastic model. We have explored both Kelvin and Maxwell viscoelastic models along with the dynamic behaviors of a mass point attached to the viscoelastic model. By using the time-dependent polished rod force measured with a dynamometer as the input to the viscoelastic models, we have obtained the displacement responses, which match closely with the actual measurements in experiments and operations. Further study and experiments have been planned and partially implemented in the McCoy School of Engineering at Midwestern State University, a member of the Texas Tech University System.

Determination of Forces in the Meridional Rods of the Mesh Dome

Currently, the construction of residential domed houses in Russia is gaining popularity. It is possible to use dome structures for the formation and reconstruction of an expressive urban environment, as pavilions, awnings, cover public spaces. The use of domes in urban development solves the problem of maintaining the landscape in optimal condition, improves its aesthetic and functional properties.This paper discusses a technique for determining the forces in the rods of a mesh dome to simplify the search for these forces, and a study of design solutions for wooden mesh shells using the example of a dome for a pool. Also, the developed model is tied to the terrain, which makes it possible to solve part of the practical problem.The main design parameters for the method and the algorithm for working with it are given, in the general case, taking into account different values of the coefficients of the design models.

Investigating the Effect of the Rock‐Socketed Depth of the Hinged Cable‐Anchored Pile on the Earthquake Response Characteristics of Supporting Structures

In order to meet the design requirements of the anti‐slide pile, the form of the anchor‐pull pile is often adopted in engineering applications. In the present study, the seismic response characteristics of hinged cable‐anchored piles with different rock‐socketed depths are analyzed using a large‐scale seismic model test platform and numerical simulations. The obtained results show that the rock‐socketed depth significantly affects the seismic response of the pile‐anchor system. It is found that, as the rock‐socketed depth increases under the same seismic conditions, the peak acceleration at the top of the anchored pile, the peak dynamic Earth pressure behind the pile, the axial force of the anchor rod, and the bending moment of the pile body decrease and the seismic stability of the anti‐slide pile improves. It is concluded that, in the seismic design of anchor‐pulled piles, increasing the rock‐socketed depth of the anchor is an appropriate scheme to improve the seismic performance of anchor‐pulled piles. The research results have a certain significance for improving the understanding of the seismic response law of hinged cable‐anchored piles and improving the seismic design.

Numerical Simulation Study of Anti-Large Deformation Bolt Structure

In order to study the mechanics of the anti-deformation hemp anchor rod, and numerical simulation was carried out with ANSYS finitengen software, the mechanics characteristics of a single spiral anchor and a hemp anchor rod under different spiral rings were compared and analyzed. The results show that for a single screw anchor, the number of spiral turns has a greater effect on the stretch elongation rate of the anchor test piece, and the more spiral turns, the greater the elongation when the anchor is destroyed, and the structural deformation of the anchor rod force is greater, which is the main reason for the increase of the elongation with the increase of the number of spiral rings. The hemp anchor is affected by the number and spacing of spiral rings, and does not produce yield stage and destruction stage when stretching, which indicates that the hemp anchor has better ability to resist shearing and deformation. In engineering applications, the ability of hemp anchor rod to resist large deformation of surrounding rock can be effectively improved, the effect of roadway support can be ensured, and the research results provide theoretical basis for the application and parameter design of hemp anchor.

SPATIAL PROBLEMS OF DYNAMIC STABILITY OF FRAME STRUCTURES

Periodic longitudinal forces in structural elements caused by operational or seismic influences, at certain values of the parameters of these forces can cause the occurrence and growing of transverse oscillations of these elements. This phenomenon is called parametric resonance or loss of dynamic stability. In the works of N. M. Belyaev, N. M. Krylov, М. М. Bogolyubov, E. Mettler, V. N. Chelomey, V. V. Bolotin flat problems of dynamic stability of frame structures were investigated. In this paper the modified Bolotin’s method, proposed to solve flat problems of dynamic stability of frames, is used. Instead of the deformation method used by V. V. Bolotin to construct analytical expressions of deflections of frame rods, in the modified method the numerical-analytical method of boundary elements is used. The article proposes a method for constructing domains of dynamic instability of frames in the space of parameters (frequency and amplitude) of seismic and operational dynamic influences that cause longitudinal forces in the rods, which periodically change over time and lead to unlimited growth of transverse oscillations amplitudes in the domains of instability. The proposed method is demonstrated in example, which considers the spatial problem of dynamic stability of a П-shaped frame with two concentrated masses located on it, which are under the action of vertical periodic forces. These forces create periodic longitudinal forces in the vertical rods of the frame. Areas of dynamic instability of the frame were constructed. Taking into account the destructive effect of oscillations is important for practical application. The most dangerous destructive effect of oscillations is observed in earthquakes and explosions. The study of this action makes it possible to avoid undesirable consequences of oscillations by limiting their level and to solve important practical problems of the dynamics of structures. Solving dynamics problems is a difficult problem. Dynamic calculation of structures provides their bearing capacity under the combined action of static and dynamic loads.

STUDY OF SPATIAL PROBLEMS OF DYNAMIC STABILITY OF REINFORCED CONCRETE FRAMES

Abstract. The article proposes a method for constructing areas of dynamic instability of reinforced concrete frames in the space of parameters (frequency and amplitude) of seismic and operational dynamic impacts that cause the appearance of longitudinal forces in the bars of structures, which periodically change in time and lead to an unlimited increase in amplitudes of transverse vibrations when the values of these parameters are in the areas of instability. The proposed method is demonstrated by a specific example, which considers the spatial problem of dynamic stability of a П-shaped frame with two concentrated masses located on it, which are under the action of vertical periodic forces. These forces create periodic longitudinal forces in the vertical rods of the frame. Areas of dynamic instability of the frame are constructed. From the point of view of human activity, fluctuations can be both beneficial and harmful. We can observe vibrations of various buildings, structures, bridges, which cause additional stresses and deformations of these structures, have a harmful effect on their safe functioning. Too intense fluctuations lead to serious consequences. This leads to the destruction of individual elements of the structure and, as a result, to accidents. The most destructive effect of vibrations is observed during earthquakes and explosions. The study of vibrations is of great practical importance. This avoids the unwanted effects of fluctuations by limiting their level. Only on the basis of a deep study of various types of vibrations can important practical problems of the dynamics of structures be solved. Solving dynamics problems is a complex problem. In contrast to static calculation, when studying oscillations, one has to take into account an additional factor – time. The dynamic design of structures provides them with bearing capacity under the combined action of static and dynamic loads. A construction will be considered as a system with an infinite number of elementary masses distributed over it with an infinitely large number of dynamic degrees of freedom.

The tensioning process of ellipsoidal suspen-dome structures with considering the friction of cable-strut joints

The friction between cable and cable-strut joints is a high nonlinear behavior which can cause the loss of cable force and then affect the mechanical behavior of integral structure during the construction and service phase. The ellipsoidal suspen-dome structures have been commonly utilized in practical engineering. Compared to the suspen-dome structures in spherical shape, the prestress loss of hoop cable is very different from the suspen-dome structures in ellipsoidal shape. To quantify the influence of friction force on the cable-strut joints of ellipsoidal suspen-dome structures, an iterative program for quantifying the friction force proposed by authors is integrated with tension compensation method. The influence of form coefficient and the connection stiffness, including axial stiffness and bending stiffness, are systematically investigated. The results indicated that the shape of upper grid structures has significantly influence on the loss of cable force. The friction can reduce the displacement of the whole structure and semi-rigid connection can increase the displacement of the whole structure, and the increase of both will lead to the increase of cable force loss. The friction will reduce the stress of radial rod, while semi-rigid connection will increase the internal force of radial rod. Both of them have little effect on the stress distribution of struts.

Center Impedance Method for Estimating Complex Modulus with Wide Frequency Range and Large Loss Factors

A simple method for determining viscoelasticity over a wide frequency range using the frequency response function (FRF) mobility obtained by the center impedance method is presented. As user data comprise the FRF between the velocity of the excitation rod and excitation force, it is challenging to separate the signal and noise. Our proposed method is based on the FRF obtained from the analytical solution of the equation of motion of the viscoelastic beam and relationship between the complex wavenumber (real wavenumber and attenuation constant) of flexural wave and viscoelasticity. Furthermore, a large loss factor can be handled over a wide frequency range without using the half-power bandwidth. In this study, actual FRF mobility data containing noise were processed using preprocessing, inverse calculation, and postprocessing. Preprocessing removed low-coherence data, compensates for the effects of instrument gain, and transformed the FRF into its dimensionless equivalent. Then, inverse calculations were used to solve the mobility equation and determine the complex wavenumber. In postprocessing, the complex wavenumber obtained by the inverse calculation was curve fitted using functions with mechanical significance. Consequently, the storage modulus based on the curve-fitted complex wavenumber was a monotonically increasing frequency function. The loss factor had a smooth frequency dependence such that it has the maximum value at a single frequency. The proposed method can be applied to composite materials, where the application of time-temperature superposition is challenging. We utilized the measured FRF mobility data obtained over a duration of several seconds, and this method can also be applied to materials with large loss factors of 1 or more.

Influence of different ultrasonic transducers on the precision of fastening force measurement

In the assembly process of aero-engines, the accurate measurement of bolt fastening force is particularly important, which is related to the normal operation of the entire system. Ultrasonic non-destructive testing has been applied to bolt fastening force measurement and has a broad application background. The core device of the ultrasonic transducer is a piezoelectric ceramic wafer, and the normal operation of the wafer is affected by the power frequency and external stress. For the same type of bolt with the same nominal diameter, the ultrasonic transducer wafers of different diameters will cause the transducer wafers to be subjected to different external stresses. According to the acoustoelastic effect, the relationship between the variation of time of flight (TOF) and bolt fastening force of different types of ultrasonic transducers is established. Then the measurement errors of various models are calculated and analyzed. The experimental results show that when the nominal diameter of the bolt is close to the diameter of the wafer of the ultrasonic transducer, the fastening force measurement accuracy of the bolt is the highest. When small or large size transducer is used, the measurement accuracy will be reduced due to energy and external stress. When a transducer with a higher center frequency is used to measure the fastening force of the bolt rod, the accuracy of the model established due to the faster attenuation of the sound wave is reduced, and the accuracy of the measurement result is reduced. Therefore, in order to ensure the accuracy of the fastening force measurement in the aerospace field, when selecting an ultrasonic transducer, the impact of the transducer size and center frequency should be fully considered.

Modelling and simulation of deflection mechanism in rock drilling processing

With the development of social economy, hydraulic drilling machine has been widely used in the tunnel bridge, water conservancy projects and mining. In the process of construction, the drill rod of the hydraulic rock borer in drilling perforating process will produce deviation. It is often caused by the drilling efficiency and reduces the drilling hole scrap, seriously hindered the development of construction technology of drilling and blasting. Through the hydraulic drilling machine drill rod in the drilling cutting process of force analysis, drill rod in horizontal and vertical direction of the mechanical model are established. The relationship between the drill rod force and deflection of drilling in the drilling process is derived. At the same time, build ADAMS mechanical model, and the drilling process is simulated to find the relationship between the depth of drilling and the offset and offset angle. On this basis, the mechanical mechanism of borehole deviation of hydraulic rock drill is clarified, which provides a theoretical basis for the hydraulic rock drill hole deviations.

Optimization of the rod forces in the reticular support structure of JUNO central detector

The structure of Jiangmen Underground Neutrino Observatory (JUNO) central detector is a complex structure subjected to a complex environment. The inner continuous acrylic spherical shell is connected to the outer reticulated stainless-steel (SS) shell through SS rods, and all these structural components are supported by an SS supporting frame. The inner shell is subjected to considerable buoyancy since the detection liquid inside the inner shell has less density than the outside water. Optimization of load path of such an underground structure subjected to buoyancy and pressure loads is difficult due to these complex situations, and in this paper, we tackle the problem of finding the optimal load path to minimize the rod forces. We adopt three types of design variables relevant to the load path, i.e., rod locations, chimney liquid level, and disc spring stiffness. Specifically, B-spline function is adopted to map the rod locations so as to significantly reduce the number of variables, and the chimney liquid level that influences the pressure distribution is taken as a new type of design variable. Subsequently, a numerical method combining the finite element analysis and a derivative-free optimization algorithm is proposed. Based on the optimization results, influences of the design variables, including their types, number, and initial values, on the optimal solutions are discussed in depth. The results suggest that the chimney liquid level and disc spring stiffness have a global effect of shifting rod force distribution, while distribution of rod forces strongly depends on the rod locations. The proposed method is shown to be effective to find an optimal load path of a complex spherical shell structure under various nonlinear constraints.

Strength characterization of exposed column base plates subjected to axial force and biaxial bending

Exposed Column Base Plate (ECBP) connections are commonly used to connect columns in steel moment frames to concrete footings. Although their response under uniaxial bending and axial force is well established, only limited research and design guidance exists for their response under biaxial bending. A new method is presented to characterize the internal stress distribution and anchor rod forces in ECBP connections subjected to biaxial bending and axial compression. The method is based on (and validated against) finite element simulations on ECBP connections; these simulations are, in turn, validated against experimental data. The proposed method extends the American Institute of Steel Construction’s Design Guide One approach (for uniaxially loaded ECBP connections) to biaxial loading. This involves addressing indeterminacies that arise due to the engagement of additional anchor rods (as compared to the uniaxial case). The proposed method accomplishes this through the enforcement of a predetermined pattern of tensile forces in the anchor rods, in conjunction with a stress block on the compression side. The method is demonstrated to predict anchor forces with good accuracy across a range of configurations (including column and base plate size) and loadings (level of axial force and bending angle). Implications for the design of ECBP connections are outlined along with limitations of the proposed approach.