Variable Axial Force Research Articles

Dynamic Analysis on Unbuckling Process of Helically Buckled Coiled Tubing While Milling Plugs

In down-hole interventions, the thin elastic coiled tubing (CT) extended for thousands of meters underground would typically undergo helical buckling as a result of axial compressive force. This paper builds an analytical model to describe the unbuckling behavior of a helically buckled CT with a new view to the stretching process in the plug milling operations. The new dynamic unbuckling equation is built on the basis of the general bending and twisting theory of rods. Under the continuous contact assumption, the helical angle is only subject to time; thus, the dynamic equations can be simplified and the analytical solutions can be obtained. By using the new governing equations, the angular velocity, axial force, and contact force relative to CT are analyzed in the unbuckling process. The calculation results indicate that the parameters including CT diameters and wellbore diameters have a strong influence on the variation of axial force and wellbore contact force. Moreover, the wellbore contact force is greater than zero during the whole unbuckling process which confirms the continuous contact assumption. These new results provide important guidance for accurate job design for the plug milling operations during the well completion stage.

Quasi-static tests of RC columns under variable axial forces and rotations

The behaviour of reinforced-concrete (RC) elements subjected to axial force and rotation variations in conjunction with lateral displacement variation is considered a highly important topic, but only a few experimental studies investigating this topic have been performed. In this paper, five full-scale RC rectangular columns were tested by quasi-static testing (QST) to investigate the effects of large variation axial forces and rotations on the seismic behaviour of columns. Furthermore, the effects of variable axial forces and rotations on the seismic performance of RC columns in terms of the failure modes, hysteretic loops, skeleton curves, ductility factors, stiffness degradations and energy dissipations are presented and analysed. Based on the QST results, the axial force and rotation variations have significant effect on the seismic behaviour of RC columns. Generally, the variable axial forces and rotations may cause a distinct asymmetrical failure phenomenon in the specimens and reduce the lateral strength and ductility factor. Thus, RC columns should be well designed to account for the adverse effects of variable axial forces and rotations.

A new and simple analytical approach to determining the natural frequencies of framed tube structures

This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.

Analytical Assessment of the Effect of Vertical Ground Motion on RC Frames Designed for Gravity Loads with Various Geometric Configurations

The paper presents an analytical investigation of the effect of vertical ground motion on the selected 13 reinforced concrete (RC) frames with different geometric configurations. For this purpose, earthquake ground motions with various vertical‐to‐horizontal peak acceleration ratios are selected to which a suitable scale factor is applied to match with seismic hazards of Korea. The methodology involves the evaluation of the structural responses of RC frames subjected to the selected records by means of nonlinear time history analyses. The results from the analysis are compared with results from studies of the case of horizontal‐only excitation. The effect of the vertical earthquake component on damage of RC frames is considered at both the global and the local levels. The effect of vertical ground motion on axial force, shear demand, and shear capacity of RC columns is investigated to assess failure on a local level. In particular, the shear capacity is evaluated by using both the conservative method of a design code and more realistic predictive approaches. The results of the extensive analyses indicate that vertical ground motion can significantly affect the response of RC members in terms of axial force variation and shear capacity. These results point to the conclusion that vertical ground motion needs to be included in analysis for assessment and design.

The FEM Simulation on End Mill of Plastic Doors and Windows Corner Cleaning Based on Deform-3D

In the plastic doors and windows corner cleaning process, the rotating speed, the feed rate and the milling cutter diameter are the main factors that affect the efficiency and quality of the of corner cleaning. In this paper, SolidWorks will be used to establish the 3D model of end mills, and use Deform-3D to research the end mill milling process. And using orthogonal experiment design method to analyze the effect of rotating speed, the feed rate and the milling cutter diameter on the axial force variation, and to get the overall trend of axial force and the selection of various parameters according to the influence of axial force change. Finally, simulate milling experiment used to get the actual axial force data to verify the reliability of the FEM simulation model. And the conclusion obtained in this paper has important theoretical value in improving the plastic doors and windows corner cleaning efficiency and quality.

Friction stir processing of Al6061-SiC-graphite hybrid surface composites

ABSTRACTFriction stir processing (FSP) of Al6061-SiC-Graphite hybrid composites is studied in detail via force analysis, spectroscopic, microstructural and indentation studies. Effect of various tool rotational speeds was assessed, and the axial force variation was monitored. The presence of graphite as a reinforcement influences the axial force fluctuations due to its flaky nature and high thermal conductivity. Variation in microstructure at different tool rotational speed is studied using scanning electron microscope. The tool rotational speed has a significant influence on the area of FSP zone, fragmentation and depth of penetration of particles, dispersion of agglomerates and grain refinement of the matrix material. Spectroscopic characterization of the processed samples was done using Raman analysis and X-Ray diffraction studies. A noticeable change in intensity and shift in the respective Raman peak positions were observed, indicating residual stresses and various disorders in the crystal structure of the reinforced particles. Influence of tool rotational speed and existence of SiC and Graphite particles on the mechanical properties were further evaluated using nano indentation testing. The hybrid composite shows the combination of best and uniform mechanical properties at an optimum set of processing parameters.

Simulation of the vibrations of a non-uniform beam loaded with both a transversely and axially eccentric tip mass

The main purpose of this work is to employ the Adomian modified decomposition method (AMDM) to calculate free transverse vibrations of non-uniform cantilever beams carrying a transversely and axially eccentric tip mass. The effects of the variable axial force are taken into account here, and Hamilton’s principle and Timoshenko beam theory are used to obtain a single governing non-linear partial differential equation of the system as well as the appropriate boundary conditions. Two product non-linearities result from the analysis and the respective Cauchy products are computed using Adomian polynomials. The use of AMDM to make calculations for such a cantilever beam/tip mass arrangement has not, to the authors’ knowledge, been used before. The obtained analytical results are compared with numerical calculations reported in the literature and good agreement is observed. The qualitative and quantitative knowledge gained from this research is expected to enable the study of the effects of an eccentric tip mass and beam non-uniformity on the vibration of beams for improved dynamic performance.

Investigation of coupled instability for shear flexible FG sandwich I-beams subjected to variable axial force

The general thin-walled beam model is presented to study the flexural-torsional coupled buckling behavior of shear flexible sandwich I-beams made of functionally graded materials based on an orthogonal Cartesian coordinate system. The derived beam model includes the transverse shear, the restrained warping induced shear deformations, the structural coupling coming from the material anisotropy, and the variable axial force effect. Material properties of the beam such as Young’s and shear moduli are assumed to be graded across the wall thickness. The strain energy and the potential energy due to the variable axial force are introduced. The seven coupled instability equations are derived from the energy principle. To solve the instability problem, three types of finite beam elements, namely, linear, quadratic, and cubic elements are employed with the scope to discretize the governing equations. In order to verify the accuracy and efficiency of the beam model presented by this study, numerical results are presented and compared with results from other researchers. By numerical examples, the bisymmetric and mono-symmetric I-beams with two types of material distributions are considered to investigate the effects of shear deformation, variable axial force, gradient index, thickness ratio of ceramic, boundary conditions, material ratio, and span-to-height ratio on the buckling behavior of FG sandwich I-beams. Particularly, the crossover phenomenon in buckling modes with changes in gradient index and thickness ratio of ceramic in flanges is investigated.

Second-order torsional warping theory considering the secondary torsion-moment deformation-effect

Abstract In this paper, the influence of the variable axial force and of the Secondary Torsion-Moment Deformation-Effect (STMDE) on the deformations of beams due to torsional warping is investigated. The investigation is based on the second-order torsional warping theory of doubly symmetric beams with thin-walled open or closed cross-sections. The effect of the axial force on the torsional stiffness of thin-walled beams is considered according to the second-order torsional warping theory. The solutions of the underlying differential equations are used for setting up the relations, needed for application of the transfer matrix method. They are derived, considering both static and dynamic action. This enables stablishing the local element matrix of the twisted beam in the framework of the Finite Element Method (FEM). The numerical investigation comprises static and modal analyses of thin-walled beams with I cross-sections and rectangular hollow cross-sections. The results are compared with results obtained by the FEM, using solid and beam elements available in standard software.

Design, Development, and Application of a Compact Flexure-Based Decoupler With High Motion Transmission Efficiency and Excellent Input Decoupling Performance

Here, we present the design, development, and application of a compact flexure-based decoupler, which is commonly utilized in compliant parallel mechanisms (CPMs) to transmit the motion of an actuator and protect the actuator from suffering transverse loads. The kinematic structure selection of the decoupler is first introduced. Then, several specific design requirements are proposed to guarantee its key performances. On this basis, the detailed structures of each part of the decoupler are discussed and the geometric parameters are optimized to obtain an ideal decoupler. The performances of the optimized decoupler are verified with finite element analysis (FEA). According to the optimized results, a prototype is fabricated and experimental tests on the input axial stiffness and natural frequency are presented. Both FEA and the experimental results demonstrate the excellent performance of the decoupler. Finally, the proposed decoupler is applied in the development of a 2-DOF CPM. The definition and calculation expression for the input coupling degree (ICD) of the CPM are given, and its geometric parameters are optimized to reduce the ICD. A prototype of the CPM is fabricated for the performance evaluation. A new method is proposed to test the ICD of the CPM by detecting the variations of axial forces along the two axes. Contouring properties of 2-D trajectories are also provided. The experimental results not only demonstrate the excellent decoupling performance of the CPM but also verify the effectiveness of the adoption of the decoupler.

Seismic Performance Evaluation of a Reinforced Concrete Arch Bridge

The entire Himalayan belt including Nepal area, because of its active tectonic movement, is seismically active causing high risk of earthquake in this region. It is important to evaluate the seismic performance of the structures including bridges to identify to what extent they would survive during earthquake. A reinforced concrete two hinged arch bridge located in Chobhar, Nepal has been selected for the research purpose. This paper presents the determination of seismic performance of a reinforced concrete arch bridge under different ground motions. The seismic input was taken as five different earthquake ground motion histories having different V/H peak ground acceleration ratio for time history analysis. Displacement capacity of the bridge was determined from pushover analysis. Time history analysis was conducted in two different steps: first only horizontal acceleration was applied and next vertical acceleration was applied in addition to horizontal ground motion. Comparisons were made between the responses of the bridge for these two cases. It was found that inclusion of vertical component of ground motion has negligible effect in variation of longitudinal displacement. However, there was remarkable effect in axial force variation. Significant effect in axial force variation in arch rib was observed as V/H ratio increased although the effect in longitudinal displacement with increase in V/H ratio was negligible. Moment demand also increased due to high axial force variation because of vertical ground motion.Journal of the Institute of Engineering, 2016, 12(1): 120-126

해상 운송 플랜트 구조물의 고장력 볼트 피로성능 평가

해양플랜트 구조물은 현장에서의 제작이 어려워 작업장에서 중 소단위의 모듈로 제작한 뒤 바지선을 이용해 현장으로 운송 후 설치 제작하는 방식이 사용되고 있다. 이 때 운송 시 발생하는 반복적인 환경하중으로 인해 구조물의 접합부에 피로하중이 작용하게 된다. 따라서 본 연구에서는 플랜트구조물의 운송과정에서 발생하는 피로하중을 적용한 고장력 볼트 접합부의 피로강도에 대한 구조적 신뢰성을 확인하고자 도입축력, 마찰계수, 볼트종류를 변수로 한 실험연구를 수행하였다. 다양한 변수를 고려한 고장력 볼트의 축력변화에 따른 볼트 풀림 현상 규명 연구결과, 고장력 볼트의 축력변화가 1% 내외에서 나타나 구조적 안전성에는 영향을 미치지 않는 것으로 판단된다. The offshore plant structure has been transported to the site by barge because it is hard to manufacture in site. When the structure was transported on the sea, offshore plant structures and connection were experienced repetitive submarine load. For this reason, it was known for that the axial force of high-strength bolted connection was declined. Therefore, in this study, high-strength bolted connection was evaluated the shear fatigue performance under longtime fatigue load during marine transport. The experimental variables were selected intial axial force, surface type, and bolt type because they ar important factors in the change of axial force of bolts. As a experimental results of considering various variables, the variation of axial force showed within 1%. Therefore, the high-strength bolted connection was verified structural safety under longtime fatigue load.

Effect of Variable Axial Force on the Deflection of Thick Beam Under Distributed Moving Load

Effect of Variable Axial Force on the Deflection of Thick Beam Under Distributed Moving Load

地震時の外力分布を考慮した外柱－基礎梁－場所打ち杭接合部の部分架構実験

Damage to foundation structures which cause inclination/settlement of buildings resulting in prohibition of the usage has been reported after recent earthquakes in Japan. Such damage was often observed to boundaries between superstructure and foundation structure with piles. In order to make judgement of availability of earthquake-damaged buildings with pile foundation, assessment of piles is indispensable; however, there are very few experimental researches clarifying the behavior of column-foundation beam-pile joints which are subjected to complicated seismic loads. Therefore, a series of experimental tests for the column, foundation beam and cast-in-place pile joints under realistic seismic loads was conducted to obtain the fundamental data, which is likely to provide key behavior to detect damage to the pile foundations after seismic events. In this study, a SRC building damaged to the foundation beams, piles, and pile caps in the 1995 Kobe earthquake was focused (Figs. 1 to 3). In particular, an exterior column-foundation beam-pile joint with severe damage was targeted. Shear forces applied to the exterior pile are affected by complicated seismic actions, namely, inertial forces at the foundation slab and beam as well as shear and variable axial forces to the exterior column. Therefore, numerical analyses using several models considering superstructure-pile interactions (Fig. 4, Tables1-4) were conducted to evaluate the seismic loads applied to the target joint. As a result, the inertial force at foundation was approximately 0.5 times the column shear force (Figs. 5 to 8). Based on the analytical findings, an experimental method for exterior column-foundation beam-pile joints simulating the realistic seismic behavior was proposed and applied to the structural tests. Four 1/3-scale specimens were prepared considering two parameters which were the existence of a superstructure wall on the foundation beam and the volume of the pilecap (Figs. 9-10, Tables5-7). The specimens were supported with a pin at the inflection points of the column and pile, respectively, and a roller at that of the beam. Horizontal cyclic loads were applied to the ends of column and foundation beam with a ratio of 1:0.5 simulating realistic shear distributions to the column and pile (Figs. 11-12). Variable axial loading was also applied to the column (pile) proportional to the applied shear force. In the cases of the specimens without the wall, the stiffness significantly decreased with flexural yielding at the end of foundation beam and the top of pile during the loading cycle to 0.5 ×10-2rad in the positive and negative directions, respectively (Fig. 13). On the other hands, in the cases of the specimens with the wall, the strengths rapidly dropped by concrete crushing at the top of pile during the loading cycle to 1.5 ×10-2rad. In particular, shear cracks on the pilecap were observed in the specimen with smaller pilecap representing the target building; however, the damage was less severe than that observed in the building. Typical bending analyses considering the post-peak strength deterioration for concrete well simulated the test results (Figs. 14-15). Furthermore, strain decreases of the beam longitudinal rebar were observed with the concrete of pile crushing (Fig. 16), which may provide a scheme to detect damage to pile foundations. Consequently, the fundamental behavior/performance of the exterior column-foundation beam-pile joints were experimental evaluated, which contributes to assess damage to piles as well as to improve the seismic design.

Linear dynamic response of nanobeams accounting for higher gradient effects

Linear dynamic response of simply supported nanobeams subjected to a variable axial force is assessed by Galerkin numerical approach. Constitutive behavior is described by three functional forms of elastic energy densities enclosing nonlocal and strain gradient effects and their combination. Linear stationary dynamics of nanobeams is modulated by an axial force which controls the global stiffness of nanostrucure and hence its angular frequencies. Influence of the considered elastic energy densities on dynamical response is investigated and thoroughly commented.

Analysis of weak solution of Euler–Bernoulli beam with axial force

In this paper, we discuss about the existence and uniqueness of the weak form of the non-uniform cantilever Euler–Bernoulli beam equation with variable axial (tensile and compressive) force. We investigate the reason of the buckling from the coercivity analysis. The frequencies of the beam with tensile force are found by the Galerkin method in the Sobolev space H2 with proper norm. Using this method, a system of ordinary differential equations in time variable is formed and the corresponding mass and stiffness matrices are constructed. A very general form of these matrices, which is very simple and suitable for calculations, is derived here with a standard basis. Numerical results for rotating beams with polynomial stiffness and mass variation, typical of wind turbine and helicopter rotor blades, are obtained. These results match well with the published literature. A new polynomial generating set is found. Using two elements of this set, a formula to find the eigenfrequencies is derived. The proposed approach is easy to implement in symbolic computing software.

Investigation on the behaviour of a thermo-active diaphragm wall by thermo-mechanical analyses

The thermo-active diaphragm walls are traditional retaining structures that embed heat exchangers for the exploitation of the near surface geothermal energy, used in the thermal conditioning of buildings and infrastructures. The coupled energetic and structural function of these so called energy walls requires some investigation in order to optimize the embedded circuit and assess the possible occurrence of significant consequences, in terms of temperature variations within the soils mass and thermal effects on the stress/strain state of the structure. In this contribution, the behaviour of an energy wall is assessed by finite element thermal analyses, that allow to investigate the energy performance and the short and long term influence on the soil temperatures, and by finite element thermo-mechanical analyses, to highlight the wall geotechnical and structural response. A one year cycle of heating/cooling operating mode of the geothermal system has been considered and the effects have been discussed in terms of soil–structure interaction and structural internal actions. The results show that the thermally induced mechanical effects are not negligible, especially as variations of the internal axial forces and bending moments. Although they seem to be not detrimental to the geotechnical and structural safety, they require a careful evaluation in order to predict possible situations of unexpected overstress conditions.

Research on the Bearing Capacity of Double Row Steel Sheet Pile Reinforcement Depth of the Based on Soil between Piles

With the complex force characteristics of double row steel sheet pile retaining structure. Through the PLAXIS 3D finite element model is established, the soil with HS-Small constitutive model, the cement soil reinforcement of double row steel sheet pile support retaining structure of pile soil, the simulation and analysis of the soil between piles reinforcement depth of double row steel sheet piles by the force and displacement. Analysis shows that with the increase of reinforcement depth:1） before and after the peak displacement of two rows of steel sheet pile becomes smaller; 2）outside row of pile axial force variation trend of different;3） outside row of steel sheet pile peak shear force and bending moment increases first and then decreases; 4）the peak reached maximum value when the reinforcement depth have different; 5）internal row pile internal force of absolute value was significantly larger than that of the outer row of piles, should according to the actual needs of the project using the appropriate reinforcement depth.

Strengthening of moment-resisting frame using cable–cylinder bracing

Cable–cylinder bracing (cable bracing system with central cylinder) is one of the modern bracing systems in which a pair of cables passes through a cylinder at their point of intersection. This research focuses on the seismic behaviour of moment-resisting frames which have been strengthened using cable–cylinder bracing. For this purpose, steel moment-resisting frames, with different numbers of storeys, were strengthened with two different types of cable bracing: cable cross-bracing and cable–cylinder bracing, and their seismic performances were compared. After performing verification, the original moment-resisting frames and those strengthened with cable–cylinder bracings and cable cross-bracings were subjected to the scaled records of six well-known earthquakes. The hysteresis, drift distribution and column axial force variation curves were plotted for the storeys at the height of the strengthened frames and compared to those of moment-resisting frames. Moreover, the energy dissipation values were also derived from the mentioned records. Based on the obtained results, the moment-resisting frames strengthened with cable–cylinder bracings performed much better compared to those strengthened by cable cross-bracing.

The influence of coupled horizontal–vertical ground excitations on the collapse margins of modern RC-MRFs

With the increasing interest in vertical ground motions, the focus of this study is to investigate the effect of concurrent horizontal–vertical excitations on the seismic response and collapse fragilities of RC buildings designed according to modern seismic codes and located near active faults. It must be stressed that only mid- to high-rise buildings are of significant concern in the context of this research. The considered structures are categorized as intermediate and special RC-MRFs and have been remodeled using distributed and lumped plasticity computational approaches in nonlinear simulation platforms, so that the utilized NL models can simulate all possible modes of deterioration. For better comparison, not only was the combined vertical and horizontal motion applied, but also a single horizontal component was considered for direct evaluation of the effect of the vertical ground motions (VGMs). At the member level, axial force variation and shear failure as the most critical brittle failure mechanisms were studied, while on the global level, adjusted collapse margin ratios (ACMRs) and mean annual frequency of collapse (λ Collapse) using a new vector-valued intensity measure were investigated. Findings from the study indicate that VGMs have significant effects on both local and global structural performance and cannot be neglected.