Rigid Displacement Research Articles

Numerical analysis of contact pressure between rolls of Sendzimir mill based on double influence function method and conjugate gradient techniques

This paper established a model for calculating the contact pressure between the rolls of the Sendzimir 20-high mill based on the influence function method with considering the dispersion distribution characteristics of backup rolls. Stone's and Hirschcock's formula are used to calculate the rolling force between the work rolls and the rolling stock. The force balance equations and the moment balance equations of the roll system are established to determine the relationship between the contact pressure of rolls and the rolling force. The deformation-compatibility equation is established by combining the flattening deformation, deflection deformation, and rigid displacement of the rolls and roll crown. The influence function method is used to solve the flattening deformation and deflection deformation between the rolls. The conjugate gradient method is used to solve the contact pressure between the rolls by combining the force balance equation group, the moment balance equation group, and the deformation compatibility equation group of the roll system. The contact pressure between rolls obtained by the model established is compared to that by the finite element method. The results show that the calculation accuracy of the model established in this paper is consistent with that of the finite element method. Significantly, the contact pressure between the backup roll and the second intermediate roll can be accurately calculated by considering the dispersion distribution characteristics of the backup roll, and the computation time can be greatly reduced.

Video extensometer for structural steel using silhouette image from telecentric illumination system

Steel structures experience plastic deformation and damage during large earthquakes. The stress–strain (S–S) curve of structural steel can be used to develop a constitutive model to simulate its structural behavior. The S–S curve can be obtained by video extensometers, the efficiency of which with a telecentric lens and telecentric illumination remains unclear. The applicability of a telecentric lens and telecentric illumination system to video extensometers were investigated. Rigid-body motion and tensile testing were performed and the carrier of displacement of six gauge lengths was traced. Further, N images were obtained under a constant displacement/force and averaged to reduce the pseudo strain. Experimental results showed that the pseudo strain increases with the out-of-plane rigid displacement but remains unaffected by the in-plane rigid-body displacement. Tensile testing results showed an error difference of <10 % for the Young’s modulus obtained from the video extensometer and strain gauge.

Effect of Considering Wave Angles on the Motion Response of Oversized Floating Bodies in Offshore Airports under Irregular Wind and Wave Loads

Most existing studies are based on the hydroelastic response of oversized floating bodies under regular waves, ignoring the effect of wave conditions and incident wave angle on the vibration response of oversized floating bodies in real sea conditions. In this paper, the stability performance of a single module of a mega-floating body at an offshore airport was investigated by using STAR-CCM + numerical simulations based on a specific model, with the introduction of parameters under extreme random wind and wave combined sea conditions. By comparing and analyzing the distribution characteristics of the single module floating body under the action of regular waves and irregular waves, wind, and wave load, and by considering the wave angle along the flow direction, as well as the spreading direction and vertical displacement value under the action of mooring, the overall displacement amplitude of rigid displacement, elastic deformation displacement and considering the influence of both, and the distribution law of motion response along the length of the floating body, we summarize the influence of the wave angle on the dynamic response of an oversized floating body of an offshore airport. The results show that the maximum value of the hydro-elastic response tends to appear at the head and tail of the floating body, the rigid body vertical displacement dominates the role, the amplitude of all displacements of the floating body under the action of the cross wave is larger, and the stress area along the floating body is larger when the wave angle is between 15–30°. The floating body stress value is smaller with angles of 30–65°, and the ability to bear the load is stronger. The hydroelastic response under irregular wave conditions is more sensitive to the wave direction angle, and the elastic deformation has less influence.

Hierarchical anatomical structure-aware based thoracic CT images registration

Accurate thoracic CT image registration remains challenging due to complex joint deformations and different motion patterns in multiple organs/tissues during breathing. To combat this, we devise a hierarchical anatomical structure-aware based registration framework. It affords a coordination scheme necessary for constraining a general free-form deformation (FFD) during thoracic CT registration. The key is to integrate the deformations of different anatomical structures in a divide-and-conquer way. Specifically, a deformation ability-aware dissimilarity metric is proposed for complex joint deformations containing large-scale flexible deformation of the lung region, rigid displacement of the bone region, and small-scale flexible deformation of the rest region. Furthermore, a motion pattern-aware regularization is devised to handle different motion patterns, which contain sliding motion along the lung surface, almost no displacement of the spine and smooth deformation of other regions. Moreover, to accommodate large-scale deformation, a novel hierarchical strategy, wherein different anatomical structures are fused on the same control lattice, registers images from coarse to fine via elaborate Gaussian pyramids. Extensive experiments and comprehensive evaluations have been executed on the 4D-CT DIR and 3D DIR COPD datasets. It confirms that this newly proposed method is locally comparable to state-of-the-art registration methods specializing in local deformations, while guaranteeing overall accuracy. Additionally, in contrast to the current popular learning-based methods that typically require dozens of hours or more pre-training with powerful graphics cards, our method only takes an average of 63 s to register a case with an ordinary graphics card of RTX2080 SUPER, making our method still worth promoting. Our code is available at https://github.com/heluxixue/Structure_Aware_Registration/tree/master.

Higher-Order Relative Kinematics of Rigid Body and Multibody Systems. A Novel Approach with Real and Dual Lie Algebras

In this paper, a computing method for the higher-order acceleration vector field properties in general rigid body motion and multibody system is proposed using algebraic properties of dual number algebras. The higher-order accelerations field of a rigid body in a general motion is uniquely determined of higher- order time derivative of a spatial twist. For the relative kinematics in multibody systems, equations that allow the determination of the higher-order order acceleration vector field are given, using an exponential Brockett-like formula in these algebras. This is obtained with no need for further differentiation of the body pose with respect to time variable. The properties for the fields of velocity, acceleration, jerk, and jounce are presented, as well as cases of the general theory. This approach uses the isomorphism between the Lie algebra of the rigid displacements ▪, of the Special Euclidean group, SE3, and the Lie algebra of dual vectors. The results are coordinate-free and in a closed-form.

To the calculation of steel structures from thin-walled rods

The article contains a brief historical essay on the main ideas for calculating systems composed of thin-walled rods of open profile. The main approaches to the calculation of these systems taking into account the inequality of nodal deplanations are analyzed.&#x0D; It is proposed to use the finite element method using thin finite rods and specially constructed superelements as finite elements, which take into account the participation of nodal joints. The stiffness matrix of a thin-walled rod of the 14th order, built on the basis of the classical Vlasov's non-slip theory for open-profile rods, when the cross-sectional displacement is taken into account. Nodal superelements consist of shell finite elements and have m deplanation degrees of freedom according to the number of rods that approach the node.&#x0D; With the help of the matrix of stiffness of the nodal superelement, the connection between the deplanai, which affect the node, and the reactive forces, which have the form of bimoments realized. The method of construction of the node stiffness matrix is ​​indicated, which is based on the use of infinitely rigid bodies, displacements and rotations of which allow to simulate the influence of deplanations on the node. The peculiarities of the assembly operation in the presence of nodal superelements are indicated.&#x0D; Possible variants of inclusion of the considered technique in software complexes for calculation of building designs are specified.

DEM-Based Numerical Investigation of Seismic Stability of Rock Slope in Terms of Rigid Block Displacement

Abstract For the seismic behavior of a rock slope or more specifically a rock wedge, the limit equilibrium method is frequently utilized to determine the static and pseudo-static safety factor, and the Newmark method is usually applied to estimate the permanent dynamic displacement. However, the two methods are relatively complex, which negatively affects their usage in engineering practice. A new idea to analyze the static and dynamic stability of a complex rock slope was provided in this paper by combing the rigid discrete element method (DEM), shear strength reduction (SSR) method, and Newmark method. The research results show that (1) by setting the joint contact stiffness to a very large magnitude, the joint displacement caused by the reduction of joint contact stiffness during the SSR calculation process can be considered ignorable, making the contact behavior between the respective two joints approximately satisfy the rigid-plastic assumption. In this manner, it is feasible to calculate the static and pseudo-static safety factor (SF) and the permanent dynamic displacement of a rock wedge with the rigid DEM. (2) The SF and sliding forces of wedges can be directly calculated by this new method without any auxiliary assumption of motion direction or sliding type. Additionally, the new method is suitable for complex wedges, which is important to practical design. (3) The rigid DEM can be realized in 3DEC, which is testified in this paper by 5 classic static examples and 3 typical dynamic examples. (4) The effect of some important parameters, such as the excitation acceleration amplitude and dip of intersection line between two joints, on the dynamic displacement and SF under dynamic excitation was analyzed. The parameter analysis revealed that evaluating the seismic performance of a rock slope only with the pseudo-static SF would potentially underestimate the seismic displacement, under some special conditions. (5) An example case was presented in this paper that the seismic stability assessment of a block was performed with the proposed approach in terms of seismic displacement. And the slope reinforcement scheme was suggested with respect to exceedance probability. It is noted that the reinforcement scheme obtained from the rigid DEM has a better cost-saving benefit under the same SF. Overall, the knowledge gained in this paper may offer a new idea for the static and dynamic analysis to the rock slope stability.

THE EFFECT OF SLAB DISCONTINUITIES ON STRUCTURAL PERFORMANCE CAUSED BY MEZZANINE

Slabs may contain discontinuity due to various reasons such as mezzanine. Mezzanine are widely used in our country. In this study, eigen value and static pushover analyses were made for mezzanine formed by one and two direction. Totally six different structural models were analysed separately for both X and Y direction. The periods, effective mass participation ratios, base shear force, elastic and effective rigidity and target displacement for different performance level were obtained for all structural models. Suggestions were made after comparison of all values and the interpretation of the results. The slab discontinuities and the differentiation of story heights in the building due to the mezzanine appear as risks that weaken the building defence mechanism. The study is important on behalf of asserting the interaction of two different negativity variables and revealing the effect of commonly used mezzanine levels on the structural earthquake behaviour.

Dynamic Response of a Vehicle-Bridge Expansion Joint Coupled System

The paper investigates the dynamic vibration property of the vehicle-bridge expansion joint coupled system with the proposed model. The dynamic response of the expansion joint under the action of the vehicle is the key factor affecting the life of the expansion joint. The changes of contact state and tire geometric characteristics were frequently left aside in the past to simplify the tire model. This is because the contact between tire and expansion joint is a very complex process. But this will seriously underestimate the impact effect of the vehicle on the expansion joint. In this paper, a dynamic mathematical model of the 2-axle vehicle-modular bridge expansion joint (MBEJ) coupled system is established by introducing a flexible roller tire model. The influence of tread rigid displacement and change in the tire contact patch length are considered in the dynamic model. Based on this model, the characteristics of the dynamic tire load and the center beam vibration displacement in the coupled system are obtained by simulation. The results show that the maximum dynamic tire load of the vehicle occurs at the end of the bridge deck behind the MBEJ, so local structure reinforcement needs to be considered. The interaction between the front and rear wheels of the 2-axle vehicle can be ignored. The vehicle position, vehicle velocity, gap width, and spring stiffness of the center beam bearing have significant effects on the impact factors of tire load and center beam vibration displacement. The impact factor of tire load may exceed the recommended values of Chinese and European bridge codes. These should be taken seriously.

When cracks are (not) a structural concern: the case of 'Giovanni Vinciguerra' School in Anagni

This paper presents the structural assessment of a portion of 'Giovanni Vinciguerra' School, located in the municipality of Anagni, Italy. In 2009, the presence of some cracks in the vaults of the basement led the authorities to close the building and declare it not usable. In this work, firstly a proper knowledge of the history, geometry and structural configuration of the school was achieved by means of bibliographic research, laser-scanner survey and visual inspections. During onsite inspections, the damage observed was also surveyed and mapped in detail. Then, structural analysis applying graphic statics and inverse piecewise rigid displacement (PRD) analysis was carried out with the aim to identify the causes of damage and evaluate the residual structural safety of the building. The results obtained allowed to prove that the structure is safe despite the occurrence of some damage in the basement.

A comparative study of the structural, vibrational, electronic and thermoelastic properties of α−SiO2 and α−Si(NH)2 from first principles

We present a systematic comparison of the fundamental ground state structural, vibrational, and electronic properties of α-SiO2 (quartz) with those of the isoelectronic imide analog α-Si(NH)2 using first principles quantum-based simulations. Potential synthesis routes for crystalline α-Si(NH)2 are proposed using a thermochemistry approach that combines solid-state and molecular methods to treat heterogeneous reactions consistently. The α-quartz phase of Si(NH)2 is predicted to be thermodynamically stable with ΔGfo,298= -251 kJ/mol which is approximately a third of the value obtained for α-SiO2 (ΔGfo,298= -753 kJ/mol). The substitution of NH for O leads to a 7% increase in Si-X bond lengths, and an 8° reduction in Si-X-Si angle, and an overall molar volume increase of about 12% in the static lattice approximation. A detailed analysis of the compression behavior of the NH analog yields a 70% increase in bulk modulus and a systematic alignment of the NH groups parallel to the c-axis with increasing pressure. The electronic properties of the oxide and imide were obtained using the TB09 meta-GGA functional which predicts an indirect band gap of 8.2 eV for SiO2, in good agreement with observed values, and an indirect band gap of 5.5 eV in the NH analog. We also calculate the excitonic contributions to the dielectric function and show that the imide analog has an enhanced reflectivity in the 0–10 eV range compared to the oxide. Simulated Raman and infrared spectra of the oxide and imide indicate that symmetric Si-X vibrations involving rigid NH displacements have similar frequencies in the two systems while asymmetric modes that couple NH groups lead to splittings of key features in the imide.

Bearing Characteristics of Diaphragm Wall Foundation under Vertical and Combined Load

To investigate the bearing characteristics of diaphragm wall foundation under combined load, the results from elasto-plastic analyses of 3D finite element models (FEM) were presented in this study. The vertical load of the diaphragm wall foundation is borne by inner and outer side resistance, resistance of soil core and the end of wall, respectively. Moreover, the sum of end resistance and soil core resistance accounts for about 75% of the vertical load. The mobilization mechanism and distribution of side resistance of the foundation were also analyzed. It is clarified that the mobilization characteristics of inner and outer side resistance of the wall are completely opposite. Due to the combined load, the horizontal load has an amplification effect on the settlement of the foundation. Additionally, the calculation methods of the Eight-component Winkler spring model and rigid pile displacement were used for determining the vertical load-bearing capacity and the overturning stability. A comparison between results from the FEM and the theoretical calculation methods showed that the results of the numerical simulation properly coincided with that of the displacement solution of theoretical model. The conclusions obtained by the above methods all indicate that the foundation has the characteristics of overall overturning failure under the combined load.

Single and double null equilibria in the SMART Tokamak

The SMall Aspect Ratio Tokamak (SMART) device is a novel, compact (R geo = 0.42 m, a = 0.22 m, A ≥ 1.70) spherical tokamak, currently under development at the University of Seville. The SMART device is being developed over 3 phases, with target on-axis toroidal magnetic fields between 0.1 ≤ B ϕ ≤ 1.0 T, and target plasma currents of between 35 ≤ I p ≤ 400 kA; with phases 2 and 3 enabling access to a wide range of elongations (κ ≤ 2.30) and triangularities ( − 0.50 ≤ δ ≤ 0.50). SMART employs four internal divertor coils with two internal and two external poloidal field coils, enabling operation in lower-single, upper-single and double-null configurations. This work examines phase 3 of the SMART device, presenting a prospective L-mode discharge scenario without external heating, before examining five highly-shaped equilibria, including: two double null triangular configurations, two single null triangular configurations and a baseline double null configuration. All equilibria are obtained via an axisymmetric Grad-Shafranov force balance solver (Fiesta), in combination with a circuit equation rigid current displacement model (RZIp) to obtain time-resolved vessel and plasma currents.

Method and Parameter Reliability of In-situ Direct Shear Test on Vibroflotation Gravel Piles

Vibroflotation gravel piles can improve the antisliding stability of soft soil foundations. However, in-situ direct shear tests have rarely been conducted on vibroflotation gravel piles, and the understanding of the test methods and the reliability of the derived parameters varies. Three groups of in-situ direct shear tests on vibroflotation gravel piles for a reservoir bank treatment project are conducted. The design diameter of the piles is 100 cm, and the pile filler is artificial sandstone gravel with a maximum particle size of 15 cm. The specimens are formed by applying a steel square frame to encase the top section of the piles. For the specimens of groups S1 and S2, only the section above the shear plane is encased with the frame. The shear surface of S1 contains a small amount of soft soil while that of S2 contains no soft soil. For group S3, two pile sections above and below the shear plane are encased with the frame, and a steel support is set upon the lower frame in the opposite direction of the shear force. The shear failure of the piles is a type of plastic shear contraction failure mode with more than 4.5% shear strain and no peak shear stress. The internal friction angles and cohesion values are 20.8° and 20 kPa for S1, 30.5° and 21 kPa for S2, and 35.0° and 30 kPa for S3. Test results show that the restraint of the steel frame enhances the bite force between the gravel particles in the shear process. Moreover, the rigid shear displacement constraint set upon the lower frame makes the test pile cut along the control shear surface, thereby increasing the shear strength. Therefore, the test parameters are higher than those under working conditions. To ensure consistency between the test conditions and the working conditions of the piles, this work proposes the following suggestions for improving test measures: 1) the pile section should not be encased below the shear plane and should be kept buried in soil; 2) some soil should be retained around the pile in the steel frame above the shear plane.

Analyze Instructional Materials for Physics Modul Integrated Natural Disasters and Mitigation

Today natural disasters are a global issue. Several countries have made strategies in natural disaster mitigation. Natural disasters of land forest fires, smog, floods, and landslides are common disasters in Riau province. Environment and natural disaster phenomena are closely related to physics. Integrated Physics materials of natural disasters can be applied in secondary schools. The teaching materials in general consist of knowledge, skills, and attitudes that students must learn to achieve a standard competence. The purpose of the research is analyze the physics instructional material of natural disasters to build physics modules integrated with natural disasters and mitigation in secondary schools. The method used ADDIE model (Analyza, Design, Development, Implementation and Evaluation). This research in analyze. The define (analyze) stage is done through field study and literature study to collect the kinds of material hat occur in the concept. The scope of the study analyzed the material physics curriculum 2013 high school integrated natural disasters namely particle dynamics, rotation dynamics and equilibrium rigid body, static fluids, dynamic fluids, heat and displacement. This research was conducted at SMAN 15 Pekanbaru City. The school used a revised 2013 curriculum. This research includes qualitative approach research and descriptive research type. The physics that can be integrated are the rotational dynamics and equilibrium of rigid objects, the weight points of objects, static and dynamic fluids and heat and displacement. The material is integrated into the material of natural disasters that often occur in Riau province, namely landslides, forest fires, smog and floods.

A Multilevel Model for Calculating the Motion of Rocks

The presence of a large number of loose rocks, often accompanied by giant rocks, which are highly destructive to the surface are an important factor in geological hazard risk assessment. In rocks moving along a slope, the scale of movement and the scale of deformation differ substantially in magnitude owing to their movement characteristics of large moving distance, fast rotation speed, and small deformation. A multilevel model for rock motion calculation is established to separate the rigid displacement and deformation displacement of the rock. The total rock movement displacement comprises translational displacement, rotational displacement, and deformation displacement. Three corresponding coordinate systems are set up. These include the translational coordinate system, which is used to describe the translational displacement of the rock, the rotational coordinate system, which is used to describe the rotational displacement of the rock, and the co-rotational coordinate system, which is used to describe the deformation displacement of the rock. The origin and the direction of the coordinate axis of the co-rotational coordinate system change with the movement of the rock. Lagrange’s principle establishes the equations of motion, which is solved by an explicit approach in the framework of the Continuum-discontiuum element method. Several numerical cases verify that this method can accurately calculate the rotational movement of the rock.

Structural irregularity quantification in buildings using vital signs

The complexity of structural irregularity guidelines in seismic design codes is increasing with revised versions of the code to cater to increased construction of iconic shaped buildings coupled with lessons learnt from building failures during past earthquakes. This short communication paper intends to present a medical approach to check the irregularity of a building based on common parameters which are indicators of its deviance from a regular configuration. Similar to the “vital signs” in medical profession, namely, body temperature, pulse rate, respiratory rate and blood pressure which are indicators of health of a human body or its disease-free state, the extend of irregularity of building structures is quantified by four parameters considered as “vital signs” in buildings, namely, time period, average support reaction per bay, distance between center of mass and center of rigidity and lateral displacement of diaphragm center of mass with increasing storeys. An implementation of the approach is demonstrated based on the analysis and result interpretation carried out on five storied building models. The outcomes of regular and irregular buildings differed significantly, which shows that there exists a similar relationship between the seismic response of buildings with various types of irregularities and can be represented using common parameters that need to be incorporated in future revisions of sesmic design codes.

Cyclic behavior of T-stub connection to hollow section steel column using TSOBs

The One-side bolts are widely used in the connection of the closed section members in the prefabricated buildings. As a novel type of one-side bolt, T-head Square-neck One-side Bolt has the advantages of the simple structure, the convenient installation, and no need for special installation tools. In this paper, the sub-model for the tension region of the T-stub bolted beam-column connection was selected as the research object, and the cyclic test was conducted on four T-head Square-neck One-side Bolted Connections (TSOBCs) for T-stub to Hollow Section Steel Column (HSSC) and two Traditional High-strength Bolted Connections (THBCs) for comparison. The results of the test including the failure modes, the applied force-displacement hysteretic curves, the applied force-displacement envelope curves, the deformation capacity and ductility, the strength degradation, the stiffness degradation, the energy dissipation, and the strain evolution are discussed and analyzed in this paper. The experimental results denote that: (1) There are two failure modes in the test, mode i, HSSC wall yielding and mode ii, T-stub flange yielding; (2) The initial stiffness and peak bearing capacity of the TSOBCs decreased by 2.5% ~ 35.6% and 21.7% ~ 39.4%, respectively, compared with those of the THBCs; (3) When the failure mode ii occurred, the ductility and the equivalent damping coefficient of the TSOBC with vertical mounting holes are 42.5% and 5.4% higher than those of the THBC, respectively. Besides, the plastic deformation, rigid displacement, and bolt offset in the TSOBCs are analyzed using finite element models.

Arch bridges subject to pier settlements: continuous vs. piecewise rigid displacement methods

Settlements severely affect historic masonry arch bridges worldwide. There are countless examples of structural dislocations and ruins in recent years due to severe settlements at the base of pier foundations, often caused by shipworm infestation of wooden foundations or scouring and riverbed erosion phenomena. The present paper proposes an original way to approach the failure analysis of settled masonry arch bridges. The proposed method combines two different 2D numerical models for the prediction of masonry arch bridge capacity against settlements and for safety assessment. The first one is the Piecewise Rigid Displacement method, i.e. a block-based limit analysis approach using the well known Heyman's hypotheses; the second one is a continuous Finite Element approach. The case study of the four-span Deba Bridge (Spain, 2018) failure is presented with the aim to illustrate how the methods work. The failure analysis produced satisfactory results by applying both methods separately, in confirmation of their reliability. Their combination also allowed to obtain a significantly reduction in computational cost and an improvement of prediction accuracy. A sensitivity and a path-following analysis were also performed with the aim to demonstrate the robustness of the presented method. The obtained simulations highlighted that the results do not depend on the friction angle and that a proper prediction of the evolution of the structural behavior can be obtained only taking into account geometric nonlinearities. Such results demonstrate once again that in settled masonry arches geometry prevails over the mechanical parameters. The current study paves the way for the fruitful use of the proposed approaches for a wider range of applications, as, for example, the mechanism identification or the displacement capacity assessment of masonry structures under overloading as seismic loads.

Hybrid Dynamic Modeling and Analysis of High-Speed Thin-Rimmed Gears

Abstract In this study, a hybrid dynamic model of high-speed thin-rimmed gears is developed. In this model, the translational and angular displacements (including the rigid and vibration displacements) with a total of six degrees-of-freedom (DOFs) are selected as the generalized coordinates for each gear, and the meshing force distributions along the contact line and between the teeth are considered. Thus, the model can be implemented under stationary and nonstationary conditions. The condensed finite element models (FEMs) are developed with the centrifugal and inertia forces for gear bodies. This paper proposes a novel method to couple the lumped-parameter model and condensed finite element model for the hybrid dynamic model system, which considers the variation of the meshing tooth during the gear operation, namely, the variations of the acting point of meshing force. Based on the model, the dynamic analysis of high-speed thin-rimmed gears is conducted under stationary speed and acceleration processes. The effects of the flexible gear body, high speed, and tooth errors on the system dynamics and tooth load distribution are investigated. The analysis results are also compared with the current reference and pure finite element method to validate the proposed model.