Internal Forces

Headline An understanding of the cause and magnitude of impacts experienced during elite rugby union match play is an important consideration for practitioners. The development of Global Positioning Systems (GPS) and video analysis technology provides detailed objective data relating to specific movement demands of players [1, 2]. Many studies have attempted to assess the influence of match variables upon restoration of performance [3, 4], yet few studies have incorporated inertial sensor impact variables when evaluating match demands and associated post-match fatigue.

It is proposed to conduct stress analysis of thick walled cylinder and composite tubes (Shrink fits) subjected to internal and external pressure. Many problems of practical importance are concerned with solids of revolution which are deformed symmetrically with respect to the axis of revolution. The examples of such solids are: circular cylinders subjected to uniform external and internal pressure. The stress analysis of thick walled cylinders with variable internal and external pressure is predicted from lame's formulae.Different case in lame's formula arethick walled cylinder having both (a) External and Internal pressure (b) Only Internal Pressure (c) Only External Pressure. In case of Composite tubes (Shrink Fit) the contact pressure between the two cylinders is determined then stress analysis is done by applying external and internal pressure in tube by lame's formulae.Theoretical formulae based results are obtained from MATLAB programs. The results are represented in form of graphs.

Penerapan peraturan terbaru mengenai ketahanan gempa bangunan, SNI 1726:2019 terhadap struktur beton bertulang bangunan Gedung Islamic Center menunjukkan bahwa terdapat beberapa elemen kolom dan balok yang memerlukan perkuatan, yakni balok B1, kolom K-Bordes, dan kolom K3. Penelitian studi kasus ini bertujuan menentukan metode perkuatan yang tepat, tebal penambahan dimensi kolom dengan metode concrete jacketing, serta jumlah lapisan FRP untuk kolom dan balok. Langkah langkah sistimatis dalam proses studi mulai dari pengumpulan data eksisting, investigasi lapangan, evaluasi struktur berdasarkan ASCE 41-17, pemodelan struktur dengan SAP2000, dan analisis data. Hasil analisis menunjukkan bahwa Kolom KBordes diperkuat dengan concrete jacketing setebal 100 mm, Kolom K3 diperkuat dengan satu lapis GFRP pada sendi plastis, dan Balok B1 diperkuat dua lapis FRP di daerah tumpuan. Uji kuat lekat (pull-off test) menunjukkan nilai kekuatan lekat GFRP terhadap beton sebesar 3,80 MPa (Balok B1) dan 2,50 MPa (Kolom K3). Pendekatan ini membuktikan efektivitas kombinasi metode perkuatan dalam meningkatkan kapasitas struktur sesuai ketentuan gempa terbaru.

Construction of twin tunnels in crowded urban cities compels the designer to select a suitable configuration and the associated railway alignment. Therefore, the estimation of optimum clear distance between tunnels, then vertical and horizontal curves of rails is significant for twin tunnel projects to obtain the optimum design of tunnels, safety and passenger comfort. A case study is the Greater Cairo metro line No. 4, Phase 1. The configuration of twin tunnels includes vertical, horizontal and diagonal alignment. Two cases for diagonal alignment, one of them tunnels pass under the River Nile. Also, two cases for horizontal alignment, one of them tunnels running above bottom clayey soil. Proper clear distance between twin tunnels has been identified according to internal forces and displacement in tunnels. Vertical and horizontal displacements have been presented for twin tunnels and for the surrounding soil. Moreover, induced internal forces in tunnel lining have been computed. Twodimensional numerical models are employed by using PLAXIS program to perform the analysis. Also, the procedures of construction of the twin tunnels have been discussed. Based on the calculated result, the clear distance between tunnels has a major effect on soil movement and internal forces in tunnel lining. It shows that the construction procedure affects the soil displacement and internal forces. Construction of the bottom tunnel at first reduces bending moment in top tunnel lining and results in small changes in bending moment in the bottom tunnel lining after the construction of top tunnel. On the other hand, the results have also shown the influence of twin tunnel configuration on railway track alignment.

Non-invert tunnels are often chosen to reduce initial construction costs compared to circular tunnels, but they frequently require expensive maintenance. Despite their widespread use, limited research has quantified the differences in material requirements (steel and concrete) between these two designs. This study compares the internal forces and material demands of circular and non-invert tunnels using centrifuge model tests and numerical analysis. A combined approach using 40g centrifuge testing and parametric analysis in OPTUM G2 assesses bending moments, lining shear forces, and shear stress distributions. Three tunnel diameters (9 m, 12 m, and 16 m) are analyzed across depth ratios (H/D = 10, 7, 5, and 1), covering eight reinforced concrete lining designs. Results show that circular tunnels have more uniform stress distributions in the lining and surrounding soil, leading to lower bending moments and shear forces. In contrast, non-invert tunnels exhibit stress concentrations near the lower fulcrum corners and spring line. Due to their uniform stress distribution, circular tunnels become more material-efficient than non-invert at greater depths and larger diameters, reducing steel use by up to 36% despite requiring up to 19% more concrete. Non-invert tunnels, however, use less material at shallow depths, saving up to 14% in steel and 23% in concrete.

In this paper, we present an iterative steering algorithm for nonholonomic systems (also called driftless control-affine systems) and we prove its global convergence under the sole assumption that the Lie Algebraic Rank Condition (LARC) holds true everywhere. That algorithm is an extension of the one introduced in [21] for regular systems. The first novelty here consists in the explicit algebraic construction, starting from the original control system, of a lifted control system which is regular. The second contribution of the paper is an exact motion planning method for nilpotent systems, which makes use of sinusoidal control laws and which is a generalization of the algorithm described in for chained-form systems.

Wooden structures are the oldest building elements accompanying man since time immemorial. The Czech Republic is strict in its legal and normative regulations relating to the use of wooden building components. In spite of that the Czech construction market is increasingly returning to wooden houses; not only for dwelling purposes, but also for public amenities. However, the structures made of wood as combustible material have to be carefully assessed especially from the viewpoint of fire safety of the building. This paper deals with the fire safety of wooden structures with special regard to the suspended type of ceiling, as it fulfils the role of insulation against the effects of fire. In particular, the thermal stress caused by fire and its impact upon the safety of the building elements has been investigated.

Pre-design static load testing of tentative piles is an important means to provide the basis for the pile foundation design before construction. This paper focuses on the tests performed on 12 instrumented super-long piles with a large diameter and high loading, intended for use in the comprehensive transportation hub project at Beijing urban sub-central station. The influences of pile construction techniques, such as base expansion and pile shaft and base grouting, on the bearing characteristics are discussed. Strains imparted in the reinforcement are measured by the vibrating wire gauge installed along with the longitudinal reinforcement in these piles. Furthermore, the axial force against the depth of each test section is derived and the shaft friction resistance at the pile-soil interface is calculated. The results obtained for each pile indicate that the axial force at each test section increases as the load increases, but its magnitude gradually decreases from top to bottom under the same level of the load. In addition, the shaft friction resistance increases with the increasing of the load, and the pile bearing capacity is significantly improved by applying relevant techniques such as base expansion and shaft grouting.

The method of Scaled Quantum Mechanical (SQM) force fields has been reviewed briefly and recent developments to make its use more automatic discussed. Essential features are the definition of internal coordinates by a computer program and also a first version of assigning scale factors automatically. SQM calculations have been applied on three tautomers of the title molecule. Completely optimized geometries include results also with a large basis set, 6-31 lG(d, p). We find no convincing evidence for the presence of any other tautomer than the N,H imino form.

Ah&met--The torsion and shear load problems of elastic beam cross-sections of moderate wall thickness are formulated in terms of finite elements with the warping function as primary variable. By introduction of suitable internal degrees of freedom in the shear problem the stiffness matrices of both problems become identical, The method makes no distinction between open and closed cross-sections. An efficient PC implementation is discussed and illustrated by examples.

The internal space for a molecule, atom, or other n-body system can be conveniently parameterised by 3n -9 kinematic angles and three kinematic invariants. For a fixed set of kinematic invariants, the kinematic angles parameterise a subspace, called a kinematic orbit, of the n-body internal space. Building on an earlier analysis of the three-and four-body problems, we derive the form of these kinematic orbits (that is, their topology) for the general nbody problem. The case n = 5 is studied in detail, along with the previously studied cases n = 3, 4.

The article presents a new didactic tool helping in teaching the structures of students of the Faculty of Architecture. It is an attempt to solve the problem related to the difficulties in teaching structural systems among students of architecture. In the beginning, examples of Graphic-Statics tools supporting an intuitive understanding of the construction work are presented. Then a physical model of the truss was implemented, which responsively presents the values of internal forces using the colors of the luminous bars. The main part of the article describes the design elements of the truss model and presents how it works. Then, the influence of the model on the education of architecture students was checked by means of a questionnaire study. The results showed the great educational usefulness of the proposed solution.

A continuum model of the orthotropic tensegrity plate-like structures with self-stress included is proposed within the six-parameter flat shell theory. This approach allows to simplify calculations, that is, it is not necessary to describe the whole complex tensegrity cable-strut structure with the use of computational methods. Average displacements, strains and internal forces for orthotropic tensegrity plate-like structures can be determined within the model. The closed form solutions for selected tensegrity plate strips and simply supported rectangular plate with sinusoidal load are presented in the paper. Tensegrity modules, which are based on the four-strut expanded octahedron modules with additional connecting cables are proposed as the examples. Self-stress and some geometrical parameters are introduced for parametric analysis.

A continuum model of the orthotropic tensegrity plate-like structures with self-stress included is proposed within the six-parameter flat shell theory. This approach allows to simplify calculations, that is, it is not necessary to describe the whole complex tensegrity cable-strut structure with the use of computational methods. Average displacements, strains and internal forces for orthotropic tensegrity plate-like structures can be determined within the model. The closed form solutions for selected tensegrity plate strips and simply supported rectangular plate with sinusoidal load are presented in the paper. Tensegrity modules, which are based on the four-strut expanded octahedron modules with additional connecting cables are proposed as the examples. Self-stress and some geometrical parameters are introduced for parametric analysis.

This study has a main problem regarding the internal and external impacts of anxiety that affect students in carrying out English language learning due to the earthquake that hit West Sulawesi. The subjects of this study were students at SMAN 2 Tapalang. The method used is descriptive qualitative research that analyzed internal and external impact of anxiety faced by the students in learning due to the earthquake in West Sulawesi. This study used observation and interview as data collection instruments. In data analysis, the researcher used three steps, the first step is data reduction, the second step is data display and the last step is data verification.The results showed that there are two impacts that are felt by the students during the learning process due to the earthquake in Tapalang District, namely internal and external impacts. Internal impacts felt by the students included psychological conditions and psychological conditions. External impacts felt by the students namely...

Pre-design static load testing of tentative piles is an important means to provide the basis for the pile foundation design before construction. This paper focuses on the tests performed on 12 instrumented super-long piles with a large diameter and high loading, intended for use in the comprehensive transportation hub project at Beijing urban sub-central station. The influences of pile construction techniques, such as base expansion and pile shaft and base grouting, on the bearing characteristics are discussed. Strains imparted in the reinforcement are measured by the vibrating wire gauge installed along with the longitudinal reinforcement in these piles. Furthermore, the axial force against the depth of each test section is derived and the shaft friction resistance at the pile-soil interface is calculated. The results obtained for each pile indicate that the axial force at each test section increases as the load increases, but its magnitude gradually decreases from top to bottom under the same level of the load. In addition, the shaft friction resistance increases with the increasing of the load, and the pile bearing capacity is significantly improved by applying relevant techniques such as base expansion and shaft grouting.

In the design scheme of a bridge with external prestressing tendons and hybrid internal and external tendons, the internal tendons can bear the load in cantilever casting construction, the external tendons can bear the superimposed dead load and the service load, and the external prestressing tendons are easy to inspect and replace in the service stage. However, in the design of prestressing tendons and hybrid tendons, different tendon arrangement schemes will lead to differences in the layout and number of internal and external prestressing tendons and determine the stress state of the bridge. This paper optimized different tendons in an engineering project during the construction process based on the principle that the internal tendons bear the load in the construction stage while the external tendons bear the superimposed dead load and the service load, highlighted the arrangement schemes of different internal prestressing tendons and the corresponding design of external prestressing tendons, and determined the final bridge design scheme and bridge stress state. The relevant design process can provide references for similar prestressed continuous girder or continuous rigid-frame bridges with hybrid tendons.

Pre-design static load testing of tentative piles is an important means to provide the basis for the pile foundation design before construction. This paper focuses on the tests performed on 12 instrumented super-long piles with a large diameter and high loading, intended for use in the comprehensive transportation hub project at Beijing urban sub-central station. The influences of pile construction techniques, such as base expansion and pile shaft and base grouting, on the bearing characteristics are discussed. Strains imparted in the reinforcement are measured by the vibrating wire gauge installed along with the longitudinal reinforcement in these piles. Furthermore, the axial force against the depth of each test section is derived and the shaft friction resistance at the pile-soil interface is calculated. The results obtained for each pile indicate that the axial force at each test section increases as the load increases, but its magnitude gradually decreases from top to bottom under the same level of the load. In addition, the shaft friction resistance increases with the increasing of the load, and the pile bearing capacity is significantly improved by applying relevant techniques such as base expansion and shaft grouting.

Tensile membrane structures are part of a unique technology that gives designers the capability to experiment new forms and new solutions to conventional design problems. These structures are extremely efficient for long span application and allows considerable savings in the foundations and supporting structure costs. Cable stayed masts are integral part of this structure typology and consists of a inclined elements supported by several layers of pre-tensioned cables. Generally their dynamic loading is not a concern in the design of tensile structures, nevertheless in case of massive shafts, their dynamics can play a fundamental role for global behaviour of the structure. Therefore pre-tensioning force on supporting cables system is an important issue since the internal force distribution, significantly affects their structural dynamic behaviour. A non-linear cable model, combined with the taut-cable theory has been employed to simulate the non-linearity conditions in the stays and cables, by using a restoring-force equivalent spring model to replicate the behaviour of each cable. In the present paper a simplified based displacement technique is utilized to examine the non-linear dynamics of the system. The proposed approach, based on energetic method Equivalent Linearization method (ELM), shows a robust simplified technique capable to linearize the non-linear system, taking into account of slackening effects of pre-tensioned stays. It is concluded that performance coefficient and linearized frequency, may possibly be used as useful indicators for designing pre-tensioned cable stayed masts where a suitable selection of the initial pre-tensioning force can effectively improve dynamic performance of the system.

A new method to compute internal forces in a multi-bodies system is presented in the paper. Lagrange equations are used to study the motion of a system under the action of known external forces. If an internal force has to be found, a supplementary mobility is considered in the system and the corresponding internal force for the new mobility is found for null value of the mobility, as well as its first and second orders of derivatives. The method is a general one, but a particular case of mechanism used in the dynamics of the airplane elevator is analyzed to verify the validity of the proposed method.

The paper presents the Finite element method (FEM) that calculates the internal force and the displacement of beams on elastic foundation in the case of the uncertainty input parameters described in terms of the number intervals. Using the interval function optimization algorithm combined with the FEM to determine the internal force values of the span reinforced concrete beam structure. This study applies the hybrid differential evolutionary optimization algorithm combined with FEM interval functions to determine the required internal force results of reinforced concrete beams placed on an elastic foundation. The calculation process is programmed using Maple.17 software to determine the displacement output and the resulting internal force in the beam. To check the correctness of the program calculated on Maple.17, the input declared dataset corresponds to the central values of the interval numbers and is recalculated by SAP2000v21 software, then evaluates the results error of intern...

This article deals with the kinematics of serial manipulators. The serial manipulators are assumed to be rigid and are modeled using the well-known Denavit-Hartenberg parameters. Two well-known problems in serial manipulator kinematics, namely the direct and inverse problems, are discussed and several examples are presented. The important concept of the workspace of a serial manipulator and the approaches to determine the workspace are also discussed.

The ultimate bearing capacity of ring footings for different conditions such as internal to external diameter ratio and angle of internal friction for sand is determined using the finite element program ELPLA Professional Edition, Version 9.0. A semi-empirical relation for determining the bearing capacity of ring footings that developed by other researchers is also described and used in compared. The value of ultimate bearing capacity is found to decrease significantly with an increase in (r =d i /d e ), where d i and d e are the internal and external diameter of the ring, respectively. For larger values of internal friction angle of soil (), the magnitude of ultimate bearing capacity is seen to be higher than smaller values. The obtained results are compared with those available in the literature.

Computing joint commands in real time by solving an inverse kinematic (IK) problem is an important manipulation task that is commonly encountered in agricultural operations such as fruit harvesting, disease detection and leaf sampling. To date, different numerical and analytical approaches have been proposed, and many of them are able to take constraints into account. In this study, a set of analytical algorithms is investigated to quickly solve the constrained five-degree-of-freedom inverse kinematic problem. The constraints due to actuator limitations and mechanical design of the mechanism are utilised in generating the solution sets for joint variables. Also a suboptimal solution for the inverse kinematic problem within this set is derived. The proposed methods are compared with a typical numerical solution based on non-linear constrained optimisation. It is shown that the proposed analytical and suboptimal semi-analytical solutions can be found in a much quicker fashion as compared to the non-linear constrained optimisation approach. The algorithms are validated by the handling mechanism in a ground robot platform specifically designed to operate in strawberry orchards.

This paper presents a path planning technique for a mobile manipulator whose end-effector path is imposed by a given task. The planning is done decoupling the kinematics of the mobile platform and the manipulator, and planning for the former as a normal mobile robot. Two criteria for planning the path were implemented, one minimizing the need to turn the mobile robot and the other minimizing the gravity induced torque components of the manipulator. The linear velocity for following the path is also calculated, as a function of the given endeffector speed. Several results are presented in some typical applications of this planning.

In Sweden, a substantial amount of railway bridges is approaching their intended lifespans and are planned to be replaced. However, it is not sustainable neither from a financial nor an environmental perspective to replace these bridges if they are still sound and safe. Thus, an evaluation of their actual capacity is required with the aim of extending their lifespans. A way to obtain a more accurate capacity is to determine the loads that are acting on them. Available literature points out the lack of experimental investigations on sleeper-ballast contact pressure, as well as on the stress distribution along and across the ballast. Consequently, railway bridge design has been based on traditional rather than rational assumptions, which can be quite conservative. In this paper, a review of models is carried out for evaluating stress patterns on the surface of the slab on ballasted concrete bridges. Then, a simplified finite element model of a concrete trough bridge, a common type of structure in Sweden, is used in a parametric analysis aimed to understand how the identified pressure distribution patterns affect the performance of this type of structure. Finally, with the purpose of studying how some parameters influence the bridge safety, a probabilistic reliability analysis is used. The reliability index beta () is obtained using the polynomial response surface method and its value is compared for different boundary condition scenarios. Also, the sensitivity factors for the considered random variables are compared and analyzed. Results show that the assumption of support condition and pressure pattern has a significant impact on the capacity, failure mode and probability of failure of this type of structure.

In this paper results obtained from monotonic nonlinear static analyses performed on Reinforced Concrete (RC) internal beam-column sub-assembly are shown. Bond-slip phenomenon between steel longitudinal bars and surrounding concrete is also taken into account in order to predict the numerical response under lateral actions of the RC internal beam-column sub-assembly investigated. The study is addressed, through parametric models and Monte Carlo simulations, to propose preliminary fragility curves for different damage states of the RC internal beam-column sub-assembly, including materials inherent uncertainties.

Рассмотрена задача о действии на трансверсально-изотропную пластину локальной силовой нагрузки. Нагрузка распределена равномерно и действует в нормальном к срединной плоскости пластины направлении. Рассмотрены выражения для внутренних силовых факторов, полученные на базе уточненной теории {1,2}-аппроксимации. Проанализировано влияние упругих постоянных трансверсальноизотропного материала на внутренние силовые факторы Ключевые слова: теория {m,n}-аппроксимации, напряженно-деформированное состояние, трансверсально-изотропные пластины, локальные нагрузки, внутренние силовые факторы Дата надходження рукопису 27.07.2017

The following text shows the state of research in developing a method for structural analysis of planar and curved lattice systems, whereby the methodological approach refers to the structural behaviour of Reciprocal Frame Systems. The method is based on the consideration of equilibrium for the bar elements and their interacting forces in the joints, and thus it develops, according to plasticity theory, a possible equilibrium solution for the internal forces of the overall structure. Because of the independence of material properties, the analysis method will show the relationship between force and form, even of complex structures, in a simple and direct way.

Nove konstrukcije velikih montažnih lučnih mostova Opisani su konstrukcijski i tehnološki aspekti gradnje velikih lučnih mostova s montažnim odsječcima primjenom betona od reaktivnog praha. Odsječci se izrađuju betoniranjem sukladnih sljubnica, spajaju epoksidnim smolama i potom prednapinju vanjskim čeličnim šipkama samo na dijelu spojnica. Lukovi se izvode zrakastim ovješenjem konzola preko petnih stupova, a grede obostranim potiskivanjem bez klasičnog kljuna s istodobnim postavljanjem stupova s grede i reguliranjem visine nivelete.

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 N x internal force component on the buckling loads and load-carrying capacity of the LC-beams.

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.

During an earthquake, the better performance of segmental tunnel lining, compared to the continuous in-cast concrete lining, is generally related to the joints between segments. In order to better understand the influence of the segment joints, their effect on the internal forces induced in tunnel lining simultaneously with the effects of the other influential parameters should be considered. In this work, the segmental joints were simulated by the representative stiffnesses and effects of these characteristics in relation to the other parameters such as the soil-liner interface behavior, number of segments in each ring and thickness of segments on the internal forces induced in structure were investigated. For this purpose, 2D numerical analyses were performed and the results obtained were discussed. Results showed that under the seismic condition, the components that had the most significant role on the internal axial forces induced in the segmental lining were rotational stiffness and axial stiffness of joints. Also the bending moments were more affected by the rotational stiffness. Generally, the radial joint stiffness had a less effect on the induced internal forces. With increase in the number of segments and their thickness, the effect of joint stiffness on the internal forces increases and the design of joints should be given more attention; however, the effects of joint stiffness and frictional behavior at the soil-liner interface on the maximum induced forces are almost independent from each other. Also in a specified joint behavior, by variation in each one of the other parameters including the soil-liner interface condition, number of segments and their thickness, the absolute magnitude of the maximum induced internal forces sometimes change significantly.

The dream of a bionic replacement appendage is becoming reality through the use of mechatronic prostheses that utilize the body's myoelectric signals. This paper presents a process to accurately capture the motion of the human hand joints; the obtained information is to be used in conjunction with myoelectric signal identification for motion control. In this work, the human hand is modeled as a set of links connected by joints, which are approximated to standard revolute joints. Using the methods of robotics, the motion of each finger is described as a serial robot, and expressed as Clifford algebra exponentials. This representation allows us to use the model to perform kinematic synthesis, that is, to adapt the model to the dimensions of real hands and to obtain the angles at each joint, using visual data from real motion captured with several cameras. The goal is to obtain an adaptable motion tracking system that can follow as many different motions as possible with sufficient accuracy, in order to relate the individual motions to myoelectric signals in future work.

This study has a main problem regarding the internal and external impacts of anxiety that affect students in carrying out English language learning due to the earthquake that hit West Sulawesi. The subjects of this study were students at SMAN 2 Tapalang. The method used is descriptive qualitative research that analyzed internal and external impact of anxiety faced by the students in learning due to the earthquake in West Sulawesi. This study used observation and interview as data collection instruments. In data analysis, the researcher used three steps, the first step is data reduction, the second step is data display and the last step is data verification.The results showed that there are two impacts that are felt by the students during the learning process due to the earthquake in Tapalang District, namely internal and external impacts. Internal impacts felt by the students included psychological conditions and psychological conditions. External impacts felt by the students namely...

In the paper, it is introduced a method to determine joint reaction forces, constraint forces and internal forces at the cross section of linkages. Based on the principle of compatibility and the ideality of constraints, the methodology is presented to analyze and determine reaction forces in planar mechanisms.

Seismic vulnerability of reinforced concrete (RC) buildings is strongly influenced by beam-column joints. Horizontal and vertical structural members converge in beam-column joints, as extremely delimited areas where the internal forces in concrete core and reinforcing bars have elevated stress gradients. In order to fully understand the seismic behavior of RC buildings and the related failures of T- and X-shaped beam-column joints (external corner and internal-positioned), an analytical model of RC joint behavior is proposed in a unified and simplified way. The equilibrium equations of cracked joint portions allow the assessment of internal stresses’ evolution at increasing values of column shear forces. In this way, the strength hierarchy is evaluated in terms of capacity for the different potential failure modes. This can drive, as a useful tool for designers, the design of new efficient structures or the assessment of existing ones to occur, with subsequent interventions to move ...

An algorithm using the step function (x-a) from the MATHCAD professional calculation program was used to calculate the bending deformations of an elastic beam suspended by means of tie rods (cables). It allowed the writing of analytical relations of shear and bending internal forces in the beam subjected to bending and the drawing of the corresponding diagrams. Also, the algorithm allowed the writing of the analytical relations of the deformations of the beam (arrows and rotations) with the help of the loading function (x), respectively its derivative d(x). The numerical simulation presented in this paper allowed finding the practical solution for the proposed problem.

This paper describes an experimental investigation on the lateral force-resisting mechanism of concrete block infilled R/C frames through measuring internal forces. A series of structural tests was conducted using several types of specimens: one bare and two infilled specimens. In particular, a new force-measuring system was developed and applied to one of the infilled specimens to obtain experimental data on internal forces. The results of force measurements revealed not only stress concentrations at the column bottom but also their mechanism. The seismic performance of R/C columns in this kind of structure was significantly affected by nonstructural block walls.

This paper describes an experimental investigation on the lateral force-resisting mechanism of concrete block infilled R/C frames through measuring internal forces. A series of structural tests was conducted using several types of specimens: one bare and two infilled specimens. In particular, a new force-measuring system was developed and applied to one of the infilled specimens to obtain experimental data on internal forces. The results of force measurements revealed not only stress concentrations at the column bottom but also their mechanism. The seismic performance of R/C columns in this kind of structure was significantly affected by nonstructural block walls.

The brachistochrone problem gave rise to the calculus of variations. Although its solution is wellknown, it is difficult to find a complete and rigourous handling of the problem. The aim of this article is to give a thorough and detailed approach to the brachistochrone problem. Classification: 49J05.

The structural behavior of T-frame bridges is particularly complicated and it is difficult using a general analytical method to directly acquire the internal forces in the structure. This paper presents a spatial grillage model for analysis of such bridges. The proposed model is validated by comparison with results obtained from field testing. It is shown that analysis of T-frame bridges may be conveniently performed using the spatial grillage model.

Seismic vulnerability of reinforced concrete (RC) buildings is strongly influenced by beam-column joints. Horizontal and vertical structural members converge in beam-column joints, as extremely delimited areas where the internal forces in concrete core and reinforcing bars have elevated stress gradients. In order to fully understand the seismic behavior of RC buildings and the related failures of T- and X-shaped beam-column joints (external corner and internal-positioned), an analytical model of RC joint behavior is proposed in a unified and simplified way. The equilibrium equations of cracked joint portions allow the assessment of internal stresses’ evolution at increasing values of column shear forces. In this way, the strength hierarchy is evaluated in terms of capacity for the different potential failure modes. This can drive, as a useful tool for designers, the design of new efficient structures or the assessment of existing ones to occur, with subsequent interventions to move ...

The beam–column connection is a fundamental element in frame structures and requires special attention in the calculation of the forces passing through it and the corresponding modeling. For the study of the moment-resisting frame in the leading countries in seismic research, uniform procedures have been introduced. However, in their seismic codes, there is still a discrepancy in how the shear force is determined in the beam–column connection. In the present paper, a new mathematical model is proposed for the analytical determination of the forces passing through the joint in the beam–beam and column–column direction. The occurring large deformations in the beam and column, which are determined during an earthquake, are considered. The material is elastic. The obtained values are compared with results determined by mathematical procedures proposed in other literature sources. The results show that the values of the shear force determined by the new model are about 20% greater than those available in the literature.

The motor system adapts to novel dynamic environments by forming internal models that predict the muscle forces needed to move skillfully. The goal of this study was to determine how muscle fatigue affects internal model formation during arm movement and whether an internal model acquired while fatigued could be recalled accurately after rest. Twelve subjects adapted to a viscous force field applied by a lightweight robot as they reached to a target. They then reached while being resisted by elastic bands until they could no longer touch the target. This protocol reduced the strength of the muscles used to resist the force field by ∼20%. The bands were removed, and subjects adapted again to the viscous force field. Their adaptive ability, quantified by the amount and time constant of adaptation, was not significantly impaired following fatigue. The subjects then rested, recovering ∼70% of their lost force-generation ability. When they reached in the force field again, their predicti...

This paper studies the dual-arm manipulation of an object by means of two collaborative robots. The latter hold the object through limited contact areas, thus applying unilateral contact constraints. This manipulation strategy increases versatility, since it does not require specific grippers depending on the object shape and size. However, to ensure grasping stability (i.e. no slipping of the object), a suitable internal force must be prescribed to ensure the fulfillment of the static-friction condition. In this work, the trend of the internal force is included among the inputs of a time-optimal trajectory planning, in order to find the minimal internal prestress that is able to both satisfy the static-friction condition and manipulate the object in minimal time. Admittance control is used to modulate the forces exerted by the robot end-effectors on the object. An extensive experimentation, on different 6-dimensional trajectories reaching linear and angular accelerations up to 4.5m/s 2 and 7.4rad/s 2 , is presented and discussed.

Despite the fact that the main advantage of robot manipulators was always meant to be their flexibility, they have not been applied widely to the assembly of industrial components in situations other than those where hard automation might be used. We identify the two main reasons for this as the 'fragility' of robot operation during tasks that involve contact, and the lack of an appropriate user interface. This thesis describes an attempt to address these problems. We survey the techniques that have been proposed to bring the performance of cur¬ rent industrial robot manipulators in line with expectations, and conclude that the main obstacle in realising a flexible assembly robot that exhibits robust and reliable behaviour is the problem of spatial uncertainty. Based on observations of the performance of position-controlled robot manipulators and what is involved during rigid-body part mating, we propose a model of assembly tasks that exploits the shape invariance of the par...