Error Analysis in Calculating the Internal Force of Plane Statically Determinate Truss by the Original Size Principle

2012 ◽  
Vol 268-270 ◽  
pp. 1168-1171
Author(s):  
Dan Ma ◽  
Yan Dong Qu ◽  
Xiang Qing Kong
Keyword(s):  
Internal Force ◽  
Calculation Error ◽  
Size Principle ◽  
Tensile Stiffness ◽  
Mechanics Of Materials ◽  
Internal Forces ◽  
Original Size ◽  
External Forces ◽  
The Given ◽  
Small Deformations

Ignoring the deformation effect, the original size principle is normally used to calculate the internal force and deformations of the bars in Mechanics of Materials, the calculation error is not discussed in the textbooks, however. In order to show the adaptability of the original size principle to calculate the internal force of plane statically determinate truss, a case of the two-bar statically determinate truss was also given. The calculation error of the internal force and the angle deformations are quantitatively studied to make a comparison between the actual internal force and that calculated by the original size principle. The research showed that the relative error of angle deformations and the internal forces of the two rods are nonlinear dependent on the external forces (the given force), tensile stiffness and the initial angle of the plane truss. If the strength and tensile stiffness of the bars can meet the requirements of engineering, the original size principle can be used to calculate the internal force of metallic bar truss under the conditions of small deformations.

Sensor-Based Estimation and Control of Forces and Moments in Multiple Cooperative Robots

2004 ◽  
Vol 126 (2) ◽  
pp. 276-283 ◽  
Author(s):  
Manish Kumar ◽  
Devendra P. Garg
Keyword(s):  
Fuzzy Logic ◽  
Fuzzy Logic Controller ◽  
Internal Force ◽  
End Effector ◽  
Use Of Data ◽  
Intelligent Behavior ◽  
Internal Forces ◽  
Estimation And Control ◽  
External Forces ◽  
And Control

Control of multiple robots presents numerous challenges, some of which include synchronization in terms of position, motion, force, load sharing and internal force minimization. This paper presents formulation and application of a fuzzy logic based strategy for control of two 6 degree-of-freedom robots carrying an object in a cooperative mode. The paper focuses on control of internal forces that get generated when two or more robots carry an object in coordination. Force/torque (F/T) sensors mounted on wrist of each robot provide the force and torque data in six dimensions. A fuzzy logic controller has been designed to use these force/torque (F/T) data to achieve a cooperating movement in which one robot acts as leader and the other robot follows. The paper also deals with estimation of external forces acting on end effector with the use of data provided by F/T sensors. These external forces and moments are not directly measured by F/T sensor since the quantities measured by F/T sensor are corrupted by the dynamics of the end effector and manipulator (a F/T sensor is usually mounted between wrist and end effector of the robot). This paper investigates the use of Kalman filtering technique to extract the external forces acting on robot end effector utilizing the underlying dynamics of the end effector. Matlab’s Fuzzy logic, Simulink, and State Flow toolboxes are used for achieving real-time, autonomous and intelligent behavior of the two robots. Simulation results from two separate experiments show that the above strategy was able to constrain the internal forces and provide a smooth movement of the manipulators.

scholarly journals Strength of eccentrically tensioned reinforced concrete structures with small eccentricities by normal sections

2021 ◽  
Vol 30 (3) ◽  
pp. 424-438
Author(s):  
Yevhen Dmytrenko ◽  
Oleg Fesenko ◽  
Ihor Yakovenko
Keyword(s):  
Reinforced Concrete ◽  
Complete Disappearance ◽  
Gradual Change ◽  
Software Complex ◽  
Internal Forces ◽  
External Forces ◽  
The Given ◽  
Concrete Elements ◽  
Considerable Loss ◽  
Central Tension

It is implemented the method of normal rectangular sections slab (shell) reinforced concrete elements strength calculating with flat eccentric tensile strength using the deformation m ethod. The results of the calculation are analyzed for the case of eccentric tension with small eccentricities with varying next parameters: the height of the cross section and the reinforcement coefficient. It is investigated the character of diagrams condition change of section “N – εc(1)” at gradual change of the stress-strain state from eccentric to the central tension. It is revealed that when the eccentricity of external forces decreases, the compressed zone of concrete decreases until its complete disappearance, and at rather small values of eccentricities of force application the balance between external and internal forces cannot be found by the method of current norms. An equilibrium is found between internal and external forces only at a two-digit diagram of the distribution of relative longitudinal deformations (in the case of a compressed zone). Variants of the given problem decision without considerable loss of calculations accuracy are offered, the most expedient of which is transition to algorithm of calculation by a method of limiting efforts. It was accepted as the basic in the previous building norms. The results of numerical calculations performed in the software complex “Lira-CAD” and the corresponding mathematical modeling confirmed the rationality and allowable accuracy of further calculations by this method.

scholarly journals Internal and External Forces Measurement of Planar 3-DOF Redundantly Actuated Parallel Mechanism by Axial Force Sensors

ISRN Robotics ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Takashi Harada ◽  
Podi Liu
Keyword(s):  
Parallel Mechanism ◽  
Force Sensor ◽  
Internal Force ◽  
Time System ◽  
Constraint Force ◽  
Real Time System ◽  
Axial Forces ◽  
Redundantly Actuated ◽  
Internal Forces ◽  
External Forces

This paper proposes a method for measuring the internal and external forces of a planar 3-DOF (degree of freedom) redundantly actuated parallel mechanism. The internal forces, force acts inside the endplate and mechanism constraint force, and the external forces, forces act on the endplate and thrusts by actuators, were measured simultaneously using the axial forces of the rods. Kinetostatic equations of the parallel mechanism were used to derive algorithms for measuring the internal and external forces. A link axis force sensor was developed using a strain gauge sensor. To verify the actual internal force of the endplate, a force sensor was also installed on the endplate. A real-time system for measuring the forces of the parallel mechanism was developed using RT-Linux. The external and internal forces were measured accurately.

Structural Analysis and Internal Force Calculation of Variable Cross-Section Silo

2012 ◽  
Vol 446-449 ◽  
pp. 429-434
Author(s):  
Rui Ting Ma
Keyword(s):  
Cross Section ◽  
Variable Cross Section ◽  
Internal Force ◽  
Variable Cross ◽  
Axially Symmetric ◽  
Internal Forces ◽  
Differential Element ◽  
Symmetric Load ◽  
Force Calculation ◽  
Constant Section

In this paper, the differential element of constant-section silo wall suffering from axially symmetric load is analyzed. From the results of constant-section silo, the author derives the displacements and internal forces of variable cross-section silo. Through a specific example, this paper compares the displacements , internal forces and concrete consumption of variable cross-section silo with those of constant-section silo, and discusses the merits of variable cross-section silo.

scholarly journals DETERMINATION OF DEFORMABILITY PARAMETERS OF CONCRETE SAMPLES BY THE FORMULAS OF FRACTURE MECHANICS

2020 ◽  
Vol 11 (2) ◽  
pp. 88-98
Author(s):  
B. A Bondarev ◽  
N. N Chernousov ◽  
V. A Sturova
Keyword(s):  
Fracture Mechanics ◽  
Lower Surface ◽  
Local Deformation ◽  
Concrete Sample ◽  
Test Scheme ◽  
Limit Value ◽  
Bending Load ◽  
Internal Forces ◽  
The Moment ◽  
External Forces

To determine the deformability parameters of concrete samples by the formulas of fracture mechanics, equilibrium tests were carried out at the stage of local deformation of the sample, which showed the correspondence of the change in external forces to the internal forces of the material resistance with the corresponding static development of the main crack. For the same purpose, the samples are tested for bending with an initial notch and the “load-deflection” diagram is recorded. In this work, we presented a test scheme for a specimen with a notch (crack) and constructed a diagram of the deformation of a specimen under bending “load-deflection”. Based on it, it is possible to predict the destruction of the material, that is, to determine the value of the load at which the limit value of deflection or the displacement of the outer edges of the notch (opening the throat of the crack on the lower surface of the specimen) can be taken as the moment of loss of the resource of the material. Also, we examined the deformation of a concrete sample during three-point bending and presented a diagram of the deformation of a concrete sample within the plastic zone. Dependencies were derived for determining the ultimate relative strains under tension and bending. Based on the results obtained, the state diagrams of the stretched concrete and the deformation scheme of the normal section of the concrete sample were constructed. As a result, the conclusion and convergence of the results.

scholarly journals Job Opening for Nucleosome Mechanic: Flexibility Required

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 580 ◽  
Author(s):  
Mary Pitman ◽  
Daniël P. Melters ◽  
Yamini Dalal
Keyword(s):  
Mechanical Properties ◽  
Computational Modeling ◽  
Chromatin Fiber ◽  
Interdisciplinary Approaches ◽  
External Cues ◽  
Internal Forces ◽  
Innovative Work ◽  
External Forces ◽  
Chromatin Biology

The nucleus has been studied for well over 100 years, and chromatin has been the intense focus of experiments for decades. In this review, we focus on an understudied aspect of chromatin biology, namely the chromatin fiber polymer’s mechanical properties. In recent years, innovative work deploying interdisciplinary approaches including computational modeling, in vitro manipulations of purified and native chromatin have resulted in deep mechanistic insights into how the mechanics of chromatin might contribute to its function. The picture that emerges is one of a nucleus that is shaped as much by external forces pressing down upon it, as internal forces pushing outwards from the chromatin. These properties may have evolved to afford the cell a dynamic and reversible force-induced communication highway which allows rapid coordination between external cues and internal genomic function.

scholarly journals The Influence of the Internal Forces of the Buckling Modes on the Load-Carrying Capacity of Composite Medium-Length Beams under Bending

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 455 ◽  
Author(s):  
Monika Zaczynska ◽  
Zbigniew Kolakowski
Keyword(s):  
Carrying Capacity ◽  
Internal Force ◽  
Load Carrying Capacity ◽  
Buckling Modes ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Load Carrying ◽  
Internal Forces ◽  
The Individual ◽  
Interactive Buckling

The distribution of the internal forces corresponding to the individual buckling modes of lip-channel (LC) beams is investigated using the Semi Analytical Method (SAM) and the Finite Element Method (FEM). Channel section beams made of 8-layered GFRP (Glass Fiber Reinforced Polymer) laminate with three different layer arrangements were considered. The effect of the internal forces on the non-linear first-order coefficients corresponding to the interactive buckling was also studied. Moreover, distributions of the internal forces corresponded to the loading, leading to structure failure for which the load-carrying capacity was determined. The results indicated a high influence of the Nx internal force component on the buckling loads and load-carrying capacity of the LC-beams.

scholarly journals Effect of Voids behind Lining on the Failure Behavior of Symmetrical Double-Arch Tunnels

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1321 ◽  
Author(s):  
Zhang ◽  
Ye ◽  
Min ◽  
Xu
Keyword(s):  
Service Life ◽  
Earth Pressure ◽  
Internal Force ◽  
Failure Behavior ◽  
Large Section ◽  
Failure Patterns ◽  
Internal Forces ◽  
Tunnel Safety ◽  
Increasing Demand ◽  
The Impact

The presence of voids behind lining seriously affects the safety of the symmetrical double-arch tunnels during service life. It is essential to find out the impact of voids on tunnel safety due to the increasing demand for the construction and maintenance of symmetrical double-arch tunnels. Model tests and numerical analyses were conducted in this research. The results attained were explored including earth pressure, internal force, and lining failure. Results reveal that the presence of voids has a large influence on the internal force in the lining of symmetrical double-arch tunnels, generally in the form of asymmetrical failure patterns of the lining. The failure patterns of the lining are greatly influenced by the size and location of voids with respect to the symmetrical double-arch tunnel circumference. Significant changes in the lining internal forces were found at the areas in the close vicinity of the void whereas a few changes were found at the bottom of the sidewall, the invert, and the central wall far away from the void. The propagation laws of lining cracks of asymmetrical double-arch tunnels are more complicated than symmetrical tunnels with a void behind the central wall. The location of the initial cracking of symmetrical and asymmetrical double-arch tunnels is the same, while the lining failure of the large-section tunnel is the most complicated.

Full-Scale Test and Numerical Simulation of Guided Flexible Protection System under a Blasting Load

2020 ◽  
Vol 26 (2) ◽  
pp. 243-256
Author(s):  
Xin Qi ◽  
Hu Xu ◽  
Zhixiang Yu ◽  
Keqin Sun ◽  
Shichun Zhao
Keyword(s):  
Element Model ◽  
Internal Force ◽  
Full Scale ◽  
Protection System ◽  
Dissipated Energy ◽  
Full Scale Test ◽  
Internal Forces ◽  
Scale Test ◽  
Stage Process ◽  
Blasting Load

ABSTRACT Both active and passive flexible protection methods are effective against rockfalls, but they can result in a secondary hazard due to cumulate rocks inside the structure. To solve this problem, guided flexible protection systems are receiving increased attention in the engineering community. In this study, a full-scale test of a guided flexible protection system was carried out, where the bottom of the mesh was anchored under a blasting load, which can be considered as an extreme loading event related to rockfall hazards. The fluid-solid coupling method was employed in a finite element model to simulate the entire process from the blast to the accumulation of rocks at the bottom of the slope. Based on the experimental and numerical results, a two-stage process was revealed, the internal force and the dissipated energy of each component were compared and analyzed, and the load-transferring path within the system was obtained. The internal forces of the support ropes reached their maximum values in the intercept stage. The posts experienced two peak values, the first of which, in the guide stage, was twice that in the intercept stage. The brake rings were the main energy-dissipating components, and the energy dissipation in the intercept stage was much greater than that in the guide stage. Furthermore, the interaction in terms of collision and friction between the rocks, the slope, and the system was not insignificant, particularly in the guide stage, which can account for more than 40 percent of the consumed energy of the rockfall.

scholarly journals Theoretical Study on Internal Forces of Primary Support of Tunnel by considering Time Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Zhuangzhi Yang ◽  
Yuqing Wang ◽  
Lin Song ◽  
Xinyu Wang
Keyword(s):  
Analytical Solution ◽  
Rock Pressure ◽  
Internal Force ◽  
Parameter Method ◽  
Tunnel Construction ◽  
Construction Technology ◽  
Supporting Structure ◽  
Internal Forces ◽  
Primary Support ◽  
Over Time

Understanding the internal force distribution and prejudging the weak part of tunnel supporting structure under complicated construction surroundings have become one of the important measures to ensure the safety of tunnel construction. Based on the initial parameter method and field-monitoring results of surrounding rock pressure, the theory of beam on elastic foundation is employed to derive the analytical solution of primary support internal forces. By combining the monitored data of rock pressure in one tunnel, solution of primary support internal force of a section is back analyzed and weak parts of the primary support are analyzed and evaluated. The results show that, after the tunnel excavation is completed, the internal forces of the primary support of the tunnel arch grow larger over time. When θ > 1.0, the internal forces change greatly. The internal force of the primary support decreased to different extents within 2 days after the primary support was applied and then gradually increased over time. Considering the situationality and changeability of the tunnel construction process, the analytical solution for the primary support internal forces of a multicenter arch tunnel proposed in this paper has a strong feasibility in tunnel construction. The conclusions obtained here could provide theoretical support for the design of supporting structure and the optimization of tunnel construction technology.

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