Stability Analysis Of Structures Research Articles

Stability analysis of shear deformable cross-ply laminated composite beam-type structures

This paper presents a shear deformable beam model for the nonlinear stability analysis of composite beam-type structures. Each wall of the cross-section is stacked in the cross-ply scheme. The incremental equilibrium equations are derived in the framework of an updated Lagrangian formulation. Hooke’s law is assumed to be valid. The nonlinear displacement field of the composite cross-section accounts for the restrained warping and the large rotation effects. The shear deformation effects are included through Timoshenko’s bending theory and modified Vlasov’s torsion theory. Additional shear correction factors due to the bending-torsion coupling occurring at asymmetric cross-sections are introduced in the analysis. The accuracy and reliability of proposed numerical mode are verified on benchmark examples, and the obtained results confirm that it can be classified as a shear locking-free model.

Research on Construction Technology of Tunnel Face Slump in Soft Rock Tunnel of China-Laos Railway

<p><strong><em> </em></strong>In Taos barrow of jade grinding rail tunnel engineering ii, of rich water karst region slipped in weak rock tunnel collapse mechanism and treatment technology for research, slipped through the establishment of the tunnel surrounding rock collapse mechanics analysis model, the theoretical calculation and finite element calculation software simulation method of combining the, constraints of the tunnel to slip down position at the beginning of surrounding rock and the structural stability analysis, According to the analysis results, the corresponding treatment measures are put forward. The results show that the settlement value of surrounding rock vault is 84.7mm, and the horizontal convergence value of arch waist is 167.4mm. The deformation value of surrounding rock is large, and it is easy to collapse. The plastic zone of surrounding rock mainly occurs at the junction of upper and lower steps on the face of the face, and the maximum plastic strain is 6.63×10<sup>-2</sup>. The arch waist of the primary support structure is prone to stress concentration, which should be reinforced during construction to prevent instability failure. According to the actual situation of tunnel construction site, combined with the finite element calculation results, the treatment structure of concrete filling combined with small pipe reinforcement was used to treat the tunnel slide collapse section. The treatment effect of tunnel slide collapse section was better, which provided a reference for the treatment of the same situation in the subsequent construction section.</p>

Relations between Structure and Zn(II) Binding Affinity Shed Light on the Mechanisms of Rad50 Hook Domain Functioning and Its Phosphorylation.

The metal binding at protein–protein interfaces is still uncharted territory in intermolecular interactions. To date, only a few protein complexes binding Zn(II) in an intermolecular manner have been deeply investigated. The most notable example of such interfaces is located in the highly conserved Rad50 protein, part of the Mre11-Rad50-Nbs1 (MRN) complex, where Zn(II) is required for homodimerization (Zn(Rad50)2). The high stability of Zn(Rad50)2 is conserved not only for the protein derived from the thermophilic archaeon Pyrococcus furiosus (logK12 = 20.95 for 130-amino-acid-long fragment), which was the first one studied, but also for the human paralog studied here (logK12 = 19.52 for a 183-amino-acid-long fragment). As we reported previously, the extremely high stability results from the metal-coupled folding process where particular Rad50 protein fragments play a critical role. The sequence–structure–stability analysis based on human Rad50 presented here separates the individual structural components that increase the stability of the complex, pointing to amino acid residues far away from the Zn(II) binding site as being largely responsible for the complex stabilization. The influence of the individual components is very well reflected by the previously published crystal structure of the human Rad50 zinc hook (PDB: 5GOX). In addition, we hereby report the effect of phosphorylation of the zinc hook domain, which exerts a destabilizing effect on the domain. This study identifies factors governing the stability of metal-mediated protein–protein interactions and illuminates their molecular basis.

A new stochastic residual error based homotopy approach for stability analysis of structures with large fluctuation of random parameters

AbstractThe large fluctuation of uncertain parameters introduces a great challenge in the stability analysis of structures. To address this problem, a novel stochastic residual error based homotopy method is proposed in this article. This new method used the concept of homotopy to reconstruct a new governing equation for stochastic elastic buckling analysis, and the closed‐form solutions of the isolated buckling eigenvalues and eigenvectors are obtained by the stochastic homotopy analysis method. On this basis, apth order origin moment of the stochastic residual error with respect to the elastic buckling equation is defined. Then, the optimal form of the homotopy series can be determined automatically by minimizing thepth order origin moment, which overcomes the disadvantage of highly relying on sample values of the existing homotopy stochastic finite element method. Moreover, the proposed method is developed to deal with the stochastic closely spaced buckling eigenvalue problem. Three mathematical examples and three buckling eigenvalue examples, including a variable cross‐section column, a 7‐story frame, and a Kiewitt single‐layer latticed spherical shell, are performed to illustrate the accuracy and effectiveness of the proposed method by comparing with the existing methods when dealing with large fluctuation of random parameters.

Nonlinear Excitations in Ultracold Atoms Trapped in Triple Optical Lattices

Various solitary wave excitations are found for a Bose-Einstein condensate in presence of two hybrid potentials in the form of triple mixtures of optical lattices. One of these potentials comprises of a combination of two important lattice profiles, such as frustrated optical lattice and double-well super-lattice, within one. Another represents a composite lattice combination, resulting in a wider and deeper frustrated optical lattice. The dynamical equation for such a system is solved by the exact analytical method to obtain a bright solitary wave, periodic wave and cnoidal wave excitations. We also report Anderson localization, bifurcation of condensate at the center and a competition between two different types of localizations upon trap engineering. Dynamical and structural stability analyses are also carried out, which reveal the obtained solutions as extremely stable for structural noise incorporation and sufficiently stable for dynamical stability. These triple mixtures of optical lattices impart better tunability on the condensate profile, which has made this system a true quantum simulator.

Direct FE numerical simulation for dynamic instability of frame structures

Dynamic instability analysis of structures has been a critical issue in the application of engineering and mechanical designs. Can we directly simulate the dynamic stability of structures like buckling analysis in finite element software? To address this question, in this study, we explore the dynamic instability of frame structures, discretized into finite element structures, through developing a direct FE numerical simulation procedure. Benefiting from the advances of eigenvalue analysis of partial differential equations and finite element technology, a direct numerical simulation procedure is developed by using Floquet theorem, harmonic balance methods and finite element method. Dynamic instability characteristics of frame structures, concerning fundamental vibration, multi-mode coupling vibration and flexural-torsional vibration deformation due to their spatial characteristics, are thoroughly investigated. The results reveal that, the developed procedure can achieve dynamic stability analysis of damped and non-damped structures. Frame's flexural-torsional vibration deformation can significantly enlarge the size and instability intensity of unstable regions, threatening dynamic stability of frame structures. Moreover, damping ratio has a slight impact on instability mitigation of the frame induced by flexural-torsional vibration. Unstable regions of mode-coupling vibration of frame have a hidden attribute. No existing approximate formula can be available to estimate instability regions of frame's flexural-torsional vibration and mode-coupling vibration. The dynamic instability index presented here can characterize unstable regions intuitively. The proposed insights can provide design guidelines for frame structures, the developed direct FE simulation procedure may be insightful for extending to explore instability mechanisms of generalized structures with complex forms owing to parametric resonance.

Structural Characterization, Thermal Stability and Non-Isothermal Kinetic Analysis of Decomposition of Poly(methylmethacrylate) and Titanium Dioxide Nanocomposites

In this study poly(methylmethacrylate) (PMMA) and the corresponding nanocomposites loaded with titanium dioxide (TiO2) films were prepared by a solution casting method. All materials were characterized by Fourier transform infrared spectroscopy, UV-visible spectroscopy, X-ray diffraction and scanning electron microscopy. The thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. The results showed that the incorporation of TiO2 nanoparticles in PMMA decreased the thermal stability of the polymer. Moreover, the kinetic study of the thermal degradation showed that the apparent activation energies of the nanocomposites PMMA/TiO2 were lower compared to the pure PMMA, confirming the catalytic effect of TiO2 nanoparticles on the PMMA thermal decomposition. Furthermore, g(α), which is the integral form of the reaction mechanism function, showed that the degradation mechanism of the PMMA nanocomposites was strongly dependent on the TiO2 amount introduced into their matrices. Finally, the degradation mechanism of the pure PMMA obeyed the R3 model corresponding to a phase boundary reaction (n = 3), whereas in the case of the PMMA/TiO2 nanocomposites, they obeyed the R2 model, corresponding to a phase boundary reaction (n = 2), for PMMA/TiO2 (3%) and an A1.5 model, corresponding to an Avrami-Erofeev correlation (m = 1.5), was obtained for the remaining nanocomposites PMMA/TiO2 (5, 7 and 10%).

Stability of the aneurysm-type solution in a membrane tube with localized wall thinning filled with a fluid with a non-constant velocity profile

We perform the stability analysis of bulging localized structures on the wall of a fluid-filled axisymmetric membrane elastic tube. The wall of the tube is assumed to be subjected to localized thinning. The problem has no translational invariance anymore, hence the stability of a bulging wave centered in the point of the localization of imperfection is usual, and not orbital stability up to a shift as in the case of translationally invariant governing equations. Motionless wave solutions of the governing equations having the form of a localized bulging are called throughout the paper aneurysm solutions. We assume that the fluid is subjected to the power law for viscous friction of a non-Newtonian fluid, and also that the viscosity of the fluid does not play a significant role and it can be neglected. The velocity profile remains not constant along the cross section of the tube (even in the absence of the viscosity) because no-slip boundary conditions are performed on the tube walls. Stability is established by demonstrating the non-existence of the unstable eigenvalues with a positive real part of the linearized problem. This is achieved by constructing the Evans function depending only on the spectral parameter, analytic in the right half of the complex plane Ω+ and which zeroes in Ω+ coincide with the unstable eigenvalues of the problem. The non-existence of zeroes of the Evans function is performed using the argument principle from the analysis of complex variable. Finally, we discuss the possibility of applying of the results of the present analysis to the aneurysm formation in damaged human vessels under the action of the internal pressure.

Modal Analysis of a Steel Truss Girder Cable-Stayed Bridge with Single Tower and Single Cable Plane

The dynamic characteristics of bridge structures are important in wind stability analysis, seismic design, fatigue assessment, health inspection, and maintenance of bridge structures; however, the mechanical and dynamic properties of different bridge types are different. A long-span cable-stayed bridge has the advantages of large flexibility, long natural vibration period, low natural frequency, dense spectrum, and denser modal than those of general structures. In this paper, the dynamic characteristics of a cable-stayed bridge with single pylon and single cable plane in the maximum cantilever stage and the complete bridge are analyzed. The single-tower cable-stayed bridge has some unique characteristics, such as lower cost, and a more beautiful appearance, but its torsional rigidity is lower, which increases the risk of wind damage and earthquake damage. Therefore, a finite element analysis of this bridge in the maximum cantilever state is carried out, and the influences of the main components’ rigidity, the inclination angles of the stayed cables, the supporting conditions, and the locations of the auxiliary piers are analyzed for the sustainability of this type of cable-stayed bridge. The analysis results show that a cable-stayed bridge with single pylon and single cable plane has more flexibility, and that the lateral rigidity and torsional rigidity are smaller. Structure rigidity, dip angles of the stayed cables, and positions of the auxiliary piers all have significant influences on the dynamic characteristics of cable-stayed bridges.

A novel discrete coordinate approach to modelling nonlinear structural instability problems with material damage

A novel analytical framework for the inclusion of active damaging processes in a structural stability analysis is presented. The framework considers quasi-static deformation processes and is formulated in terms of a discrete coordinate approach, employing an extended total potential energy functional, where the current damage state is expressed in terms of geometric configuration and applied loading. Within the current framework, an efficient analysis of structures prone to buckling instability and material damage is enabled particularly where damage initiates once structural instability has been triggered. Composite panels with multiple damage mechanisms (e.g. delaminations, matrix cracks) are studied to showcase its application.

Mechanical Model and Engineering Measurement Analysis of Structural Stability of Key Aquiclude Strata

Mechanical Model and Engineering Measurement Analysis of Structural Stability of Key Aquiclude Strata

Full-Scale Interface Friction Testing of Geotextile-Based Flood Defence Structures

Open-topped woven polypropylene cellular containers filled with dense granular ballasts are often used as emergency flood defence structures. The effectiveness of these systems is highly dependent on the interaction with their bedding surface. The characteristics of the foundation will often govern the system’s overall resistance to applied loading imposed by retained floodwater. However, the frictional relationship between polypropylene bulk bag flood defences and common bedding surfaces has not been extensively investigated. This study aims to reduce the reliance on arbitrary static friction coefficients by measuring and presenting actual data obtained through quantitative testing. This study presents the results of full-scale field testing to quantify the frictional resistance generated between filled polypropylene bulk bags and seven common bedding surfaces. Findings resulting from testing each interface scenario are expressed as coefficients of static friction. Test interfaces affording high frictional resistance comprised an unmade gravel road (µ = 0.74) and grass (µ = 0.64). Contrastingly, interfaces generating significantly lower frictional resistance were steel floated concrete (µ = 0.40) and polypropylene plastic (µ = 0.40). Test interfaces involving asphalt (µ = 0.54) and tamped concrete (µ = 0.56–0.58) were also investigated. This study recommends new friction coefficients necessary to characterise the structural stability analysis of bulk bag flood defences with greater accuracy. Practical advice based on experimental observation and field design experience is also given.

Evaluation of weak interactions of proteins and organic cations with DNA duplex structures

Molecular interactions and reactions in living cells occur with high background concentrations of organic compounds including proteins. Uncharged water-soluble polymers are commonly used cosolutes in studies on molecular crowding, and most studies argue about the effects of intracellular crowding based on results obtained using polymer cosolutes. Further investigations using protein crowders and organic cations are important in understanding the effects of cellular environments on nucleic acids with negatively charged surfaces. We assessed the effects of using model globular proteins, serum proteins, histone proteins, structurally flexible polypeptides, di- and polyamines, and uncharged polymers. Thermal stability analysis of DNA oligonucleotide structures revealed that unlike conventional polymer cosolutes, basic globular proteins (lysozyme and cytochrome c) at high concentrations stabilized long internal and bulge loop structures but not fully matched duplexes. The selective stabilization of long loop structures suggests preferential binding to unpaired nucleotides in loops through weak electrostatic interactions. Furthermore, the ability of the proteins to stabilize the loop structures was enhanced under macromolecular crowding conditions. Remarkably, the effects of basic proteins on the stability of fully matched duplexes were dissimilar to those of basic amino-acid-rich polypeptides and polyamines. This study provides new insights into the interaction of nucleic acid structures with organic cations.

Structural Stability Analysis of Eye of the Yellow Sea, a Large-Span Arched Pedestrian Bridge

To date, scholars’ research on the stability behavior of the arch structure mainly focuses on solid–web section arches, steel tubular truss arches and concrete-filled steel tubular arches, but the stability behavior of the novel spatial grid arch structure, which integrates the characteristics of grid structure and arch structure, is not yet clear. Based on the Eye of the Yellow Sea pedestrian bridge project in Rizhao, China, the stability behavior of this large-span spatial grid arch structure was studied, in this paper, by the project’s structure design team. The project is a glass covered steel arch pedestrian bridge with a span of 177 m, a height of 63.5 m, an elliptical section with a long axis of 18 m, and a short axis of 13.5 m. The elastic and the nonlinear elasto-plastic stability behavior considering different initial geometric imperfections, was analyzed by the ABAQUS finite element model. The buckling modes and the full-range load-displacement curve of the structure were analyzed, and the stress distribution, deformation mode and overall structural performance during the whole loading process were analyzed. The effects of initial imperfections, geometric nonlinearity and material nonlinearity on the ultimate load-carrying capacity of the structure were studied. The stability behavior of large-span spatial grid arch structure was studied in this paper, which provides an important reference for the design and analysis of such structures.

Electroviscoelstic Stability Analysis of Cylindrical Structures in Walters B Conducting Fluids Streaming through Porous Medium

In this research, the linear stability of a cylindrical interface between two viscoelstic Walters B conducting fluids moving through a porous medium is investigated theoretically and numerically. The fluids are influenced by a uniform axial electric field. The cylindrical structure preserves heat and mass transfer across the interface. The governing equations of motion and continuity are linearized, as are Maxwell’s equations in quasi-static approximation and the suitable boundary conditions at the interface. The method of normal modes has been used to obtain a quadratic characteristic equation in frequency with complex coefficients describing the interaction between viscoelstic Walters B conducting fluids and the electric field. In light of linear stability theory, the Routh–Hurwitz criteria are used to govern the structure’s stability. Several special cases are recoverd under suitable data choices. The stability analysis is conferred in detail via the behaviors of the applied electric field and the imaginary growth rate part with the wavenumbers. The effects of various parameters on the interfacial stability are theoretically presented and illustrated graphically through two sets of figures. Our results demonstrate that kinematic viscosities, kinematic viscoelasticities, and medium porosity improve stability, whereas medium permeability, heat and mass transfer coefficients, and fluid velocities decrease it. Finally, electrical conductivity has a critical influence on the structure’s stability.

Experimental study on triaxial creep behavior of red sandstone under different pore pressures based on ultrasonic measurement

AbstractCreep behavior of red sandstone under different pore pressures with a high temperature and confining pressure condition is studied in this paper. Ultrasonic detection method is used to monitor the variation of S wave in the creep test. The attenuation coefficient and S‐wave velocity in the creep process are analyzed. Fast Fourier transform is used to analyze the variation of amplitude in peak frequency and four main frequencies. The experimental results show that the creep deformation increases with increasing pore pressure for a given deviatoric stress, and the S‐wave velocity and attenuation coefficient decrease with increasing pore pressure. The relationship between creep strain and damage of the sample is established. It is found that the increase of pore pressure accelerates the increased rate of sample damage. Frequency spectrum analysis shows that the generation and development rate of microcracks increases with increasing pore pressure. The research can provide a theoretical basis for mining of deep mineral resources and the structural stability analysis of deep underground engineering.

Stress Optimization of F1 Car Chassis Using FEA Technique

Abstract: Chassis is the primary structural component of an automobile. It is the main supporting structure of a vehicle to which all other systems like braking, suspension and differential are attached. In this project, a methodology for F1 Car chassis design and structural stability analysis is presented. A literature study is carried out to review various existing designs of vehicle chassis, latest innovations and advanced materials used to manufacture the same. The various types of forces and stresses commonly acting on chassis structures are analyzed and their effects on the vehicle are understood. After completing literature study, several findings are listed in a systematic manner, by providing ample arguments to justify each of them. The pro-con analysis is conducted to evaluate merits and demerits of each alternative type of chassis and the material to manufacture it. In this research work, the material are Aluminum Alloy and AISI1144 Carbon steel. Analysis both material in different parameters which are essential for any ideal chasiss such as various types of forces and stresses commonly acting on chassis structures are analyzed and their effects on the vehicle. The most essential design criteria are derived by selecting different materials which then acts as important guidelines during the actual design process. Structural chassis frame is designed as per the design criteria, using the CAD software CATIAV5R19 and the structural stability of the same is tested and analyzed using ANSYS Workbench 19.0 software. From the results of these analysis tests the static structural stability of the design is confirmed. Keywords: Ansys Workbench, Design for Material, Chassis and Carbon Steel.

The base force element method based on the arc-length method for stability analysis

The Base Force Element Method (BFEM) is a simple and effective method for calculating large elastic deformation problems. In this paper, BFEM is further developed to make it useful for structural stability analysis. The generalized unbalanced displacement vector and composite tangent compliance matrix of the four-mid-node element and rod element of BFEM are proposed. BFEM can be combined with the Arc-Length Method (ALM) to analyze the stability of frame and truss structures. Through the calculation of several typical cases, the solution of this paper agrees well with the theoretical solution and the reference solution given by other methods. It is proved that the four-mid-node element and rod element of BFEM have high calculation accuracy in case of structural instability or post-buckling. In the calculation of the Lee frame, the calculation results of the four-mid-node element of BFEM are closer to the reference solutions than those of the CPS4 and CPS4R elements of general finite element software.

Self-Excitation Thresholds in RF Structures

A theory and general method for calculating self-excitation thresholds for a large class of standing and traveling-wave structures used in amplifiers, klystrons, traveling-wave tubes, and other vacuum electronic devices (VED) is presented. One determines the circuit parameters of RF structures that are changed due to the presence of electron beam and analyze the stability of the obtained matrices. New determinant equations defined by such stability matrices are derived in a general form applicable to any RF structure and as an important special case for RF structures with electron beams. The theory and computational methods described here are essential for stability analysis of RF structures and VED.

Floquet solitons in square lattices: Existence, stability, and dynamics.

In the present work, we revisit a recently proposed and experimentally realized topological two-dimensional lattice with periodically time-dependent interactions. We identify the fundamental solitons, previously observed in experiments and direct numerical simulations, as exact, exponentially localized, periodic in time solutions. This is done for a variety of phase-shift angles of the central nodes upon an oscillation period of the coupling strength. Subsequently, we perform a systematic Floquet stability analysis of the relevant structures. We analyze both their point and their continuous spectrum and find that the solutions are generically stable, aside from the possible emergence of complex quartets due to the collision of bands of continuous spectrum. The relevant instabilities become weaker as the lattice size gets larger. Finally, we also consider multisoliton analogs of these Floquet states, inspired by the corresponding discrete nonlinear Schrödinger (DNLS) lattice. When exciting initially multiple sites in phase, we find that the solutions reflect the instability of their DNLS multi-soliton counterparts, while for configurations with multiple excited sites in alternating phases, the Floquet states are spectrally stable, again analogously to their DNLS counterparts.