Movable Supports Research Articles

Parametric study for modified couple stress theory on postbuckling of size-dependent FG saturated porous mindlin microplates

Using modified couple stress and Mindlin plate theory, the present study is a parametric study for revealing the effect of length scale parameter on postbuckling of saturated poroelastic rectangular microplates with pore distribution being functionally graded across thickness. The microplate postbuckling is a nonlinear eigenvalue problem with coupled partial differential equations of equilibrium. In order to find the mode shapes, the eigenfunctions have been approximated by some complete polynomial series expansions in accordance with the conventional Ritz approximation technique. After discretizing the governing equations throughout the microplate grid points, the assembled difference equations construct a nonlinear eigenvalue problem with coupled algebraic equations. The nontrivial coefficients of the expansions were calculated such that the eigenfunctions extremize the microplate potential energy for satisfying the equilibrium homogeneous equations. Variation of the potential energy have been derived with respect to the expansions coefficients from the vantage of using Maple software. By gradual reduction in the initial end shortening of the movable supports and solving the assembled difference equations via Newton-Raphson iterations, the critical postbuckling displacement imposed to the movable supports are found along with the nontrivial coefficients regarding eigenfunctions. The results of the parametric study have revealed how geometric parameters, pore distribution, the Skempton’s coefficient, porosity, and different Supports modify the influence of length scale parameter on the microplate postbuckling.

A dynamic analysis on the effect of support excitations on vibrations behavior of symmetrical on-board rotor

In this article, we study the influence of the excitations created by the support movement, on the vibratory behavior of the rotor. The modeling of the rotor system is done by the hierarchical polynomial (h-p) version of the finite element method, on an on-board rotor with movable non-deformable supports. The disk is supposed to be rigid; the shaft is deformable and it is treated with the theory of beams of Euler Bernoulli. The 3D beam element has two nodes and is used for the discretization of the rotor. The shape functions used are the cubic Hermit type which respect the boundary conditions in all directions and represent the h-version of the finite element method and are modified so that it can be combined with the K-orthogonal polynomial form functions for the use of the h-p version of the finite element method. The energy method is used to determine the kinetic energies, and deformation of rotor system. The equations of motion of the rotor system are determined by the Lagrange method. The analysis of the dynamic behavior of the orbits of the on-board rotor systems is studied using the implicit method of Newmark and Newton-Raphson. In this article, we make some examples to study the influence of the excitations of the mobile support on the rotor behavior.

Estimation of the Parameters of Free Space Quantum Key Distribution System Depending on the Insertion Losses

A telescopic system consisting of two modules is used to organize the quantum channel. The accuracy of the adjustment of these modules relative to each other ensures a reduction in losses in the channel, therefore, an important step before conducting the next experiments is the alignment of the system. Both modules of the system are mounted on movable supports that allow the modules to rotate around two axes. Using these supports, we managed to reduce the losses in the atmospheric channel with a length of 1 meter to 10 dB when the radiation is introduced into a single-mode fiber.

Оптимальное применение опор при вводе трубопровода в скважину подводного перехода. Часть 2

The paper considers the problem of supports optimal arrangement in pulling a pipeline through the well during construction of the submerged crossing by the directional drilling method. Part 1 of this work presented results of using the pipeline rod model with positioning the transition section on the fixed supports with the variable lift height. Part 2 simulates the use of a group of the movable supports. Initially, the group working stroke is carried out accompanied by the supports positioning towards the well with a decrease in the pipeline height. After a stop in the final position, the group is being restructured taking the initial position for the next motion cycle. When the supports are moved, optimality conditions are met in the form of the missing contact load behind the well inlet and minimum stresses in the transition section, or the minimum supports reaction. The supports are brought to their initial state by taking the first support behind the last support, or by moving each of the supports in turn to the required position. The presented solution allows pulling through at the technologically determined minimum impact of the mounting loads on the pipeline.

Vibration Control of Cable Net Façade by Smart Supports

A lack of curvature reduces the out-of-plane stiffness of cable net façades. Therefore, they may experience large deformations and severe damage under heavy vertical loads such as earthquakes and wind. Axially movable smart supports are proposed for controlling structural vibrations by controlling tension of the cables. The equation of motion of the cable net, controlled by the smart support, is developed following a finite element method based program to solve the equation. The linear quadratic regulator control strategy is utilized to find the optimal control gain. The results show that smart supports, especially when connected to the central cables, can significantly control the vibrational amplitude of the structure.

ANALYTICAL CALCULATION OF DEFORMATIONS OF A PLANAR SINGLE-SPAN BEAM GIRDER WITH FOUR SUPPORTS IN THE MAPLE SYSTEM

A schema of a statically determinate beam girder with a regular structure, which has two supports at the ends, is considered. The descending and ascending braces have different inclination angles. In the system of symbolic mathematics Maple, the analytical dependence of the deflection of the structure and displacement of one of the three movable supports on the number of panels is derived by induction. In the procedure for generalizing several solutions to the general case, the operators rgf_findrecur and rsolve are used to compose and solve recurrent equations, which are satisfied by the coefficients of the sought formula. Cases of kinematic degeneration of the structure are found for a certain number of panels, the corresponding schemes of possible speeds are given, and a static interpretation of this phenomenon is given.

Modeling and assessment of the stress-strain state of above-ground pipelines at different types of compensation sections

The development of Russian fuel and energy complex in the short term is connected with the development of new hydrocarbon field in the permafrost zone and the need to build Arctic pipelines north of the 60th parallel. The ground-based structural scheme of pipeline laying is the most optimal while constructing trunk pipelines in permafrost areas in the Arctic and subarctic latitudes. The actual operating conditions of these systems are insufficiently studied. The above-ground pipeline in permafrost is in an complex stress-strain state. This study presents the results of the assessment of the stress-strain state of linearly extended above-ground pipelines at different compensation sections (triangular compensator; trapezoidal compensator; U-shaped compensator) under actual operating conditions. Using the finite element method on mathematical models, the dependences of the transverse displacements of the pipeline on movable supports and stresses arising in dangerous sections of the typical pipeline section during self-compensation of deformations on the variable design parameters of the system for various load combinations were established (the simulation was carried out in the ANSYS software package).

Snap-through of a pinned-clamped elastica with arbitrarily movable support at the clamped end

This paper studies the snap-through of a pinned-clamped elastica when the support of the clamped end can be moved arbitrarily in plane. The universal snap curve, which describes the critical boundary conditions of the pinned-clamped elasticas, is firstly obtained by determining the saddle-node bifurcation points of the moment-rotation response curves. Based on the universal snap curve, the stability of the pinned-clamped elastica can be determined when the support at the clamped end is moved. The critical boundary can also be directly obtained, where the elastica loses stability and the snap-through occurs between the non-inverted shape and the inverted shape. This study can be useful to reveal the snap-through behavior for some other complex systems where movable supports exist.

Welding supports of fine-grained steel mobile platforms

The article presents the process of welding of steel movable platform supports. There is a growing demand for the welding of difficult-to-weld fine grain steels used in civil engineering and transport. An example of this could be the use of high-strength movable platform supports. The recently used material in the production of movable platform supports are fine-grained steels due to their high tensile strength of 1000 MPa. The joints formed using them, however, are characterized by much lower strength than the native material. In this article, the most appropriate parameters were selected for welding the movable platform supports made of difficult-to-weld fine-grained steel S960 MC.

To The Assessment Of Seismic Resistance Of Buildings Made Using The Volume-Modular Technology Of The Company "KNAUF"

The results of experimental studies on the assessment of seismic stability of modular buildings under the action of dynamic loads that simulate seismic effects in earthquakes of 7-9 points on the scale of MSK-64 are presented. Design solutions for modular buildings were developed by "Novy Dom" LLC on the basis of the use of factory-made structures using KNAUF technology. Dynamic tests were carried out on an experimental setup developed at the Research Institute of Experimental Mechanics of the Moscow State University of Civil Engineering. The pilot plant included special movable supports, hydraulic cylinders, and modern measuring equipment that make it possible to evaluating the force effects, acceleration, displacement, and deformation in any element of the stand during testing. The factors that influence the seismic stability of the combined modular structure under the action of dynamic loads and exclude its destruction and the appearance of cracks in it are established. During the tests, data were obtained on the values of accelerations and deformations of the structures of the two-story experimental fragment at the specified points. Recommendations are given for increasing the strength and rigidity of the module connections in the height of the building, which will increase the reliability of volume-modular structures in case of seismic impacts.

Hinged Brick Facade Systems for Seismic Regions of Russia

The results of experimental studies on the assessment of seismic resistance of various structural solutions of hinged facade systems with a facing layer of brickwork under the action of dynamic loads on the structure, simulating seismic effects in earthquakes of 7-9 points on the scale of MSK-64 are presented. Dynamic tests were carried out with the use of an installation developed at Moscow State University of Civil Engineering, which included a metal stand with special movable supports, hydraulic cylinders (Actuator) and modern measuring equipment. This equipment made it possible to evaluate during testing the force effects on the stand, accelerations, displacements and deformations in any element of the stand and the hinged facade system. Two design variants of the hinged facade system, in which different types of masonry fastening to the supporting substructures are applied, are considered. The factors affecting the seismic stability of the facing layer under the action of dynamic loads and excluding its destruction and the appearance of cracks in it are established. During the tests, accelerations and deformations of the structures of the hinged facade system at the specified points were obtained. On the example of the analysis of the results of experimental dynamic studies of the system of the ATS-450 type of "U-kon" Company of, the effectiveness of the use of special measures that ensure the monolithic masonry and, accordingly, its reliability under seismic influences is shown.

TO THE QUESTION OF INSTALLING FREON PIPELINES IN VRF SYSTEM

This article provides recommendations on the design of VRF freon pipelines for air conditioning systems, calculation of copper pipe extensions and methods for their compensation. Examples of practical solutions of movable and fixed supports of freon pipelines, their interaction with thermal insulation are given. The question of the optimal choice of mounting units for freon pipelines VRF air conditioning systems is considered. The calculation scheme of freon pipelines in the air conditioning and heating modes with their horizontal arrangement is considered. Schemes are proposed for installing supports of various types, depending on the thickness of the pipes, as well as the design of the movable supports, the manufacture of which is carried out during installation, and their comparison with existing samples. Also considered the installation of fastenings of supports for vertical sections of freon pipelines and their design. Some recommendations for thermal insulation of freon pipelines are given.

Optimisation of Longitudinal Seismic Energy Dissipation System for Straddle‐type Monorail‐Cum‐Road Long‐Span Cable‐Stayed Bridge

To investigate the optimal longitudinal seismic energy dissipation system of straddle‐type monorail‐cum‐road long‐span cable‐stayed bridges, the Niutianyang Bridge was selected as the engineering background, and the explicit time‐domain dimension‐reduced iteration method was adopted to carry out nonlinear time‐history analysis. To consider the dynamic characteristics of longitudinal movable supports, the static and dynamic responses of four kinds of energy dissipation systems were studied, including longitudinal unconstrained, elastic cable, viscous damper, and speed lock‐up devices. The damping effect of four types of schemes in which viscous dampers were installed at piers or towers was analysed, and the parameters of the viscous dampers were optimised. The influences of the straddle‐type monorail train braking force and the running vibration of the straddle‐type monorail traffic on the parameters of the viscous dampers were analysed. This study shows that the viscous damper system had the lowest bending moment at the bottom of the tower and a smaller displacement response, and the energy dissipation was the best. Each viscous damper had the highest energy dissipation efficiency when they are installed only at the main tower. The damping effect was better when the damping coefficient c ranged from 3500 to 5000 kN · (m/s)−α and the velocity exponent α ranged from 0.35 to 0.5. The static friction of the straddle‐type monorail‐cum‐road long‐span cable‐stayed bridge support can resist the trains’ braking force, and the parameters of the viscous damper can be selected regardless of train braking. A suitably large value of velocity exponent α may be required to increase the working velocity of the viscous damper to reduce the damper’s participation in the process of the train crossing the bridge.

Critical examination of midplane and neutral plane formulations for vibration analysis of FGM beams

There has been a controversial claim that the beam model formulation for functionally graded materials (FGM) beams must be based on the neutral plane for correct solutions. This claim cuts across well accepted mid-plane formulation for FGM beams. Presented herein is a critical examination of the mid-plane and neutral plane formulations for the vibration analysis of FGM beams. It will be shown herein that the problem arises from a misconception that the immovable supporting points are located at the mid-plane when the supporting points are actually at the neutral plane when basing the formulation on the neutral plane. The positioning of the immovable simple supports at two different planes leads to the difference in results. However, in the case of movable simple supports, the mid-plane formulation furnishes the same vibration solutions as the neutral plane formulation, even though the supports are located on different planes. Both formulations furnish the same frequency results for clamped ends. The conclusion is that there is nothing wrong with using the mid-plane formulation for FGM beams. In fact, by using the neutral plane formulation, it would be difficult to solve FGM beams with a constraint on the longitudinal displacement at the midplane.

Effect of nonlinearity of restrainer and supports on the elasto-plastic seismic response of continuous girder bridge

During an earthquake, the nonlinearity of the bridge structure mainly occurs at the supports, bridge piers and restrainers. When entering nonlinear stage, members of the bridge structure affect the elasto-plastic seismic response of the whole structure to a certain extent; for multi-span continuous bridges, longitudinal restrainers can be installed on the movable piers to optimise the distribution of seismic force and enable the movable piers to bear a certain amount of seismic effect. In order to evaluate the effect of nonlinearity of restrainer and supports on the elasto-plastic seismic response of continuous girder bridge, analytical models of continuous girder bridge structure considering the nonlinearity of movable supports, restrainers and bridge piers were built and the nonlinear time history analysis was conducted to evaluate the effect of nonlinearity of restraining devices and supports on the elasto-plastic seismic response of continuous girder bridge. Relevant structural measures and recommendation were made to reduce the seismic response of the fixed piers of the continuous girder bridge.

A Novel Variable Stiffness Mechanism Capable of an Infinite Stiffness Range and Unlimited Decoupled Output Motion

In this paper, a novel variable stiffness mechanism is presented, which is capable of achieving an output stiffness with infinite range and an unlimited output motion, i.e., the mechanism output is completely decoupled from the rotor motion, in the zero stiffness configuration. The mechanism makes use of leaf springs, which are engaged at different positions by means of two movable supports, to realize the variable output stiffness. The Euler–Bernoulli leaf spring model is derived and validated through experimental data. By shaping the leaf springs, it is shown that the stiffness characteristic of the mechanism can be changed to fulfill different application requirements. Alternative designs can achieve the same behavior with only one leaf spring and one movable support pin.

Method of plastics endurance testing

The authors propose a method for testing plastics endurance under plane transverse bending with a given cyclic deformation. The paper describes the relations for the calculation of the amount of deflection, rotation angles of the end parts of a sample and the technological gap d between the pins in movable supports and a model for the transverse bending of a sample, the properties of which are given by linear-elastic and nonlinear elastic (according to power law) models. To determine the dependence of stresses on the number of cycles before sample failure, the authors propose the method for estimating stress with the use of the dependence of stresses on the number of cycles before failure and stress-deformation dependence, obtained in quasi-static tests under "instantaneous" loading.

Effects of Friction at Movable Supports on Elasto-Plastic Seismic Responses of Continuous Girder Bridges

The effect of friction on movable supports on the elasto-plastic seismic responses of continuous girder bridges was analyzed on the basis of three aspects including stiffness contribution, friction energy dissipation of the movable supports, and kinetic interaction between the girders and movable piers. Finite element models were established, which considered the friction non-linearity of the movable supports and the material nonlinearity of the reinforced concrete piers. In addition, nonlinear time history analysis was performed to analyze the effects of friction at the movable supports on the pier bottom curvature, girder displacement, velocity, and acceleration. The results indicated that the frictional effect at movable supports is not always favorable. In some cases, the friction at these points must be considered. For the nonlinear time history analysis, the effect of natural vibration characteristics of the bridge and the response spectrum of the ground should also be considered. For some complicated continuous bridges, particularly those with the heights and stiffness of the fixed and movable piers, the friction at movable supports should be considered in seismic analysis.

Effects of Friction Force at Movable Supports on Seismic Performance of a Continuous Beam Bridge

The friction force at movable supports has a certain influence on the seismic performance of the continuous beam bridge, so, the friction force should be taken into account in the seismic design of the bridges. The analytic model of the continuous bridge which including the effects of friction force at movable supports was put forward, and the analysis was done with the application of friction element. Through the analysis of a certain continuous beam bridge, the results indicate that the friction force can greatly decrease the earthquake action of this continuous beam bridge. And some suggestion on the bearing selection and the anti-seismic measure were also put forward according to the analysis.

Pipeline Support under the Loads of Comparative Analysis

This article mainly analyzed the load of fixed and movable pipe supports in the catalyst factory,then classified the load. A calculation was made using MIDAS/CIVIL software modeling. The results show that the bending moment and displacement are all the same in axial of movable and fixed pipe supports, and the axial displacement is influenced heavily by load. Fixed pipe supports are less affected by lateral load, but movable pipe supports are more affected by lateral load. The results can help us to design the pipe supports reasonably.