Linear Structural Analysis Research Articles

Linear Structural Analysis of Media Management Administration, Innovation and Early Childhood Creative Technology Under the Office of the Basic Education Commission in Thailand

Abstract The promotion of technological prowess in children at an early age is integral to their creative development and future success. This research studied the relationship between media management administration, innovation, and early childhood creative technology in schools under the Office of the Basic Education Commission in Thailand to validate and confirm the linear relationship between flexibility, motivation, imagination, use of new approaches to problem solving, and vision. Questionnaires from respondents showed that the consistency was between 0.60-1.00, with a reliability of 0.890. Data were analyzed using mean standard deviation, and linear structural analysis and compliance with empirical data was checked based on the harmony index which was then compared to applicable criteria. The major findings show that the composition is in line with the empirical data and demonstrated linear structural relationships between the components of media management administration, innovation and early childhood creative technology.

Trip stage satisfaction of public transport users: A reference-based model incorporating trip attributes, perceived service quality, psychological disposition and difference tolerance

The concept of satisfaction reflects the extent by which a consumed product or service meets the expectations of an individual consumer. Generally, a smaller discrepancy between expectation and service delivery is associated with a higher satisfaction. Satisfaction ratings do, however, not purely reflect the mapping of experienced attributes on some (reference-based) satisfaction scale. The expressed satisfaction rating may also vary as a function of attitudes, personality traits and moods of the respondent at the time of measurement. Thus, in order to estimate unbiased satisfaction with the attributes of a choice alternative, one needs to control for attitudes, moods and personality traits. In contrast with the state of the art in travel behaviour research, which is almost invariantly based on linear regression and structural equations analysis, this study explores the performance of non-linear models of trip satisfaction for public transportation. Focusing on public transportation, we assume that trip stage satisfaction systematically varies in a non-linear fashion with the discrepancy between expectations and actual experienced attributes of the trip stage, controlling for perceived service quality, attitudes, moods and personality traits. In contributing to the rapidly growing literature on travel satisfaction in general and in the context of public transportation in particular, the aim of this study is to develop a reference-based model of trip stage satisfaction that takes perceived service quality, attitudes, moods, personality traits and difference tolerance into account. Difference tolerance refers to the notion that within some tolerance level, differences between service delivery and expectations do not have a major effect on satisfaction ratings. The data used to estimate the model were collected in January 2015 in Xian, China among a random sample of respondents. Results support the contentions underlying the study: several relationships between attributes and satisfaction appear non-linear. There is also evidence of difference tolerance, but results differ between attributes.

Using polynomial chaos expansion for uncertainty and sensitivity analysis of bridge structures

Abstract The quantification of the uncertainty effect of random system parameters, such as the loading conditions, material and geometric properties, on the system output response has gained significant attention in recent years. One of the well-known methods is the first-order second-moment (FOSM) method, which can be used to determine the mean value and variance of the system output. However, this method needs to derive the formulas for calculating the local sensitivity and it can only be used for systems with low-level uncertainties. Polynomial Chaos (PC) expansion is a new non-sampling-based method to evaluate the uncertainty evolution and quantification of a dynamical system. In this paper, PC expansion is used to represent the stochastic system output responses of civil bridge structures, which could be the natural frequencies, linear and nonlinear dynamic responses. The PC coefficients are obtained from the non-intrusive regression based method, and the statistical characteristic can be evaluated from these coefficients. The results from the proposed approach are compared with those calculated with commonly used methods, such as Monte Carlo Simulation (MCS) and FOSM. The accuracy and efficiency of the presented PC based method for uncertainty quantification and global sensitivity analysis are investigated. Global sensitivity analysis is performed to quantify the effect of uncertainty in each random system parameter on the variance of the stochastic system output response, which can be obtained directly from the PC coefficients. The results demonstrate that PC expansion can be a powerful and efficient tool for uncertainty quantification and sensitivity analysis in linear and nonlinear structure analysis.

Vibration test method of nonlinear normal mode

Experimental modal analysis is an important tool in dynamic testing. Experimental modal analysis of linear engineering structures is now mature. However, nonlinear behavior of engineering structure is a challenge. In this paper, a vibration test method of nonlinear normal mode (NNM) is studied. First, a 3-DOF test device with nonlinear stiffness is designed. Then, based on methodology of force appropriation, an approach to nonlinear modal testing is studied. Specifically, multi-harmonic sine force excitation is applied on the device and velocity response of the device is measured by laser vibrometer. According to the area in force-velocity response plot, the excitation is adjusted to stimulate nonlinearity of the device. Work of this paper explores vibration test method of NNM and can be used for identification of NNM and response prediction of the system, which lays the foundation for application in engineering structure of aero-engine.

Highly precise time integration method for linear structural dynamic analysis

SummaryTo achieve high accuracy, conventional time integration methods require small time steps, especially when applied to large‐scale finite element systems. The use of small time steps calls for a large number of computations. In this paper, a strategy is proposed to construct an efficient and highly precise time integration method for linear time‐invariant systems. Adopting the multi‐substep notion, the highly precise time integration method creates an integrated amplification matrix prior to recursive calculations by multiplying the amplification matrices of N equal substeps, where a 2m algorithm and the method of storing incremental matrix are respectively employed to reduce computational cost and rounding error. On the basis of the Newmark method, two highly precise symplectic schemes and one highly precise dissipative scheme are developed. In addition, the consistent stability of the used Newmark schemes is presented. The free vibration of a three‐dimensional truss, the impact of a particle against a rod, and the forced vibrations of a rectangular thin plate and a stiff system are investigated to validate the performance of the proposed method.

Numerical studies on vibration propagation and damping test V1

Earthquakes and aircraft impacts induce vibrations that propagate throughout the entire building and they need to be considered in designing SSCs (Structures, Systems and Components). Mainly linear calculation methods have been in use in design practice and the codes and standards consider damping ratios only for linear structural analyses. Induced vibrations, especially in damaged concrete structures, have not been studied extensively enough for optimization of structural frameworks and/or qualified systems and components. Experimental data on damping properties of damaged reinforced concrete are needed also for benchmarking analysis programs and methods.
 Recently, within IMPACT project, a new type of test series considering vibration propagation has been carried out at VTT. The test target is a reinforced concrete structure with two parallel walls connected to a floor slab. The front wall is additionally supported by triangular shaped side walls which are connected to the floor slab too. The test structure is supported on elastomeric bearing pads, with back pipes effective mainly in compression and with bars effective in tension. In order to obtain information on vibration propagation in damaged concrete structure at different levels of damage grades the same structure was tested six times. At each time the mass of the deformable stainless steel missile was 50 kg. The hit point located in the middle of the front wall. The impact velocity was about 110 m/s in the first four tests (V1A-D) and about 60 m/s in the remaining two tests (V1E and F). In this paper, numerical results on tests V1A and V1F are compared with the corresponding experimental ones.
 The calculated results, such as accelerations, displacements, their response spectra and strains, are compared with experimental measurements. Five finite element (FE) programs are used in computations: Abaqus, Europlexus, LS-DYNA, SOFiSTiK and an in-house code (IHC).
 Most of the FE-codes in the present study use shell elements. In Abaqus and SOFiSTiK non-linear behaviour of shell section is modelled by dividing the cross section into layers. Reinforcements are also modelled as layers. In Europlexus and IHC, an alternative approach is adopted in which the non-linear behaviour of concrete and reinforcement is homogenized beforehand in the shell thickness direction obtaining relations between stress resultants and generalized strains valid for the shell section. In LS-DYNA, 3D solid elements for modelling concrete and beam elements for modelling reinforcements are used.
 Equations of motion are integrated with explicit central difference time integration method, except in SOFiSTiK implicit integration method is used. Modelling and computations with the mentioned FE-programs are made independently of each other. Computations with LS-DYNA are carried out as blind exercises.
 Consideration of the results from benchmarking point of view is still on-going. However it is evident that analysed results follow reasonable well test results in main design parameter level such as maximum displacements, accelerations and strains. Also frequency spectra are estimated reasonably well.

A performance based strategy for design of steel moment frames under blast loading

Design of structures subjected to blast loads are usually carried out through nonlinear inelastic dynamic analysis followed by imposing acceptance criteria specified in design codes. In addition to comprehensive aspects of inelastic dynamic analyses, particularly in analysis and design of structures subjected to transient loads, they inherently suffer from convergence and computational cost problems. In this research, a strategy is proposed for design of steel moment resisting frames under far range blast loads. This strategy is inspired from performance based seismic design concepts, which is here developed to blast design. For this purpose, an algorithm is presented to calculate the capacity modification factors of frame members in order to simplify design of these structures subjected to blast loading. The present method provides a simplified design procedure in which the linear dynamic analysis is preformed, instead of the time-consuming nonlinear dynamic analysis. Nonlinear and linear analyses are accomplished in order to establish this design procedure, and consequently the final design procedure is proposed as a strategy requiring only linear structural analysis, while acceptance criteria of nonlinear analysis is implicitly satisfied.

Enhancing the teaching of elastic buckling using additive manufacturing

This is the third part in a trilogy of papers examining ways in which additive manufacturing can be used to facilitate the introduction of basic principles in structural analysis. Each paper uses 3D-printing and simple, but non-trivial, slender geometric forms, to provide a hands-on aspect to structural behavior in which flexure plays a dominant role. The first part dealt with linear structural analysis (Virgin, 2017), extended to dynamics and vibration in the second part (Virgin, 2017). The current paper focuses on slender structures in which compressive axial loading is the new ingredient and hence buckling becomes a central issue. This has similarities and differences with the two previous papers, but in all instances the role played by relatively high-precision 3D-printing opens the door to versatile and effective illustration, and the development of a deeper appreciation of structural phenomena.

Wind resistant size optimization of geometrically nonlinear lattice structures using a modified optimality criterion method

Lattice structures normally have slender members and light weight, high flexibility and small damping ratios. Hence, their structural behavior may be affected by the geometric nonlinearity and they are prone to large displacements and safety issues due to wind loads. Optimal design of such nonlinear and flexible structures is difficult and complicated. This paper presents an automatic optimizing flow for the integrated wind-induced response analysis and wind-resistant optimal design of linear and non-linear lattice structures based on the modified Optimality Criterion (OC) algorithm. The method for structural dynamic analysis and wind-induced response of lattice structure is developed by combining Proper Orthogonal Decomposition (POD) with Load Dependent Ritz (LDR) vector method, together with the Harmonic Excitation Method (HEM) and Load Response Correlation (LRC) method. Meanwhile the quadratic programming method is used to evaluate the Lagrange multipliers in the modified optimality criterion method. Based on the derived design sensitivity analysis results for the nodal displacements, element stresses and nonlinear critical load factor of linear and nonlinear space frame structures in a companion paper, an automatic optimizing flow is then established by adopting the Application Programming Interface (API) of SAP2000 to integrate the wind-induced response, design sensitivity analysis and wind-resistant optimal design of space frame structural system. The proposed automatic optimizing flow is then applied to the optimized process of a lattice structure under dynamic wind loading. It is found that for the lattice structure, the geometric non-linear analysis and the constraint of nonlinear critical load factor need to be considered in their optimization, meanwhile updating on the time-history of wind loads and Equivalent Static Wind Loads (ESWL) is necessary as result of the variations in the design member size during the optimization process. It is also found that the maximum displacement constraint is the most important factor in the optimization of the lattice structure and maximum stress of structural elements are normally found to be inactive constraints during the optimization procedure. In the case that a low limit for the maximum displacement is pre-set, the nonlinear critical load factor becomes the important constraint. Optimized results from this study would be helpful to those involved in wind resistant analysis and optimization design research for such lattice structures.

A projection-based model reduction strategy for the wave and vibration analysis of rotating periodic structures

The wave finite element method has proved to be an efficient and accurate numerical tool to perform the free and forced vibration analysis of linear reciprocal periodic structures, i.e. those conforming to symmetrical wave fields. In this paper, its use is extended to the analysis of rotating periodic structures, which, due to the gyroscopic effect, exhibit asymmetric wave propagation. A projection-based strategy which uses reduced symplectic wave basis is employed, which provides a well-conditioned eigenproblem for computing waves in rotating periodic structures. The proposed formulation is applied to the free and forced response analysis of homogeneous, multi-layered and phononic ring structures. In all test cases, the following features are highlighted: well-conditioned dispersion diagrams, good accuracy, and low computational time. The proposed strategy is particularly convenient in the simulation of rotating structures when parametric analysis for several rotational speeds is usually required, e.g. for calculating Campbell diagrams. This provides an efficient and flexible framework for the analysis of rotordynamic problems.

Recent developments in probabilistic pushover models for the reliability re-assessment of fixed offshore structures

Re-assessment of existing fixed offshore structures in mature basins, to demonstrate they remain safe and reliable whilst optimising returns on the considerable investment, is a constant challenge for operators. This often requires the use of a probabilistic framework employing statistical techniques for environmental load predictions and nonlinear material/geometry models to determine the structural resistance. Stepping out, from code-based strength and loading recipes based on linear structural analysis and prescribed 100-year load events, to a probabilistic framework employing nonlinear structural models and a target annual failure probability, is not a straightforward task. This article explores the following aspects that engineers face when undertaking fixed platform re-assessments: (1) how to progress with an analysis when the capacity is limited by the initiation of tubular joint cracking and therefore susceptible to low cycle fatigue degradation; (2) how to determine system strength uncertainty for a given failure mode when each component has a varying contribution to the overall resistance; and (3) how to quantify the influence of gravity loading on system strength uncertainty.

Dynamic Response of Three-Dimensional Multi-Domain Piezoelectric Structures via BEM

In this paper, a Laplace domain boundary element method is applied for transient dynamic analysis of three-dimensional multi-domain linear piezoelectric structures. Piezoelectric materials of homogeneous sub-domains may have arbitrary degree of anisotropy. The boundary element formulation is based on a weakly singular representation of the piezoelectric boundary integral equations in the Laplace domain. To compute the time-domain solutions a convolution quadrature formula is applied for the numerical inversion of Laplace transform. Presented multi-domain boundary element method is tested on a three-dimensional problem of nonhomogeneous column which is made of two dissimilar piezoelectric materials and subjected to dynamic impact loading.

Linear and nonlinear soil-structure interaction analysis of buildings and safety-related nuclear structures

Soil-structure interaction (SSI) analysis is generally a required step in the calculation of seismic demands in nuclear structures, and is currently performed using linear methods in the frequency domain. Such methods should result in accurate predictions of response for low-intensity shaking, but their adequacy for extreme shaking that results in highly nonlinear soil, structure or foundation response is unproven. Nonlinear (time-domain) SSI analysis can be employed for these cases, but is rarely performed due to a lack of experience on the part of analysts, engineers and regulators. A nonlinear, time-domain SSI analysis procedure using a commercial finite-element code is described in the paper. It is benchmarked against the frequency-domain code, SASSI, for linear SSI analysis and low intensity earthquake shaking. Nonlinear analysis using the time-domain finite-element code, LS-DYNA, is described and results are compared with those from equivalent-linear analysis in SASSI for high intensity shaking. The equivalent-linear and nonlinear responses are significantly different. For intense shaking, the nonlinear effects, including gapping, sliding and uplift, are greatest in the immediate vicinity of the soil-structure boundary, and these cannot be captured using equivalent-linear techniques.

Component-wise analysis of laminated structures by hierarchical refined models with mapping features and enhanced accuracy at layer to fiber-matrix scales

ABSTRACTModern methodologies for the analysis of composite structures are demanded to satisfy the accuracy requirements at different scales, from micro to macro and possibly in a global/local sense. In this domain, the present paper proposes a hierarchical, component-wise approach for the linear static analysis of layered structures. By employing the Carrera Unified Formulation and a variational statement, finite element arrays of refined beam models are expressed in terms of fundamental nuclei. Legendre-based polynomials are utilized to implement, in a hierarchical form, higher-order beam kinematics. Also, curved cross-section geometries are formulated in a correct and consistent manner through mapping blending functions. Mapping and refined kinematics beam models are, thus, inherently combined to give the component-wise method, according to which each component of the structure (e.g., layer, fibers, and matrix) is modeled independently and with its geometric and mechanical characteristics. This approach is demonstrated to provide enhanced accuracy for the analysis of composite structures, from layer scale to fiber-matrix level, but still with low computational costs.

Деформаційний аналіз групи порід басейну Пур, Індія

Precambrian rocks exposed around Pur are a part of Pur-Banera belt that is stratigraphically placed within Aravalli Quartzite, Calc Silicate Gneiss, Quartzite and Garnetiferous Mica Supergroup. The different lithological units exposed in the area are Banded Magnetite Schist. These rocks have been subjected to multi-deformational episodes. In accordance with the modern system of multi-level deformation analysis proposed by Fedor Yakovlev in 2012, the results of the The work belongs to the scientific direction of tectonophysics, which was called “strain analysis of linear folding structures”. The present study involves analysis of strain in the rocks around Pur, Bhilwara District, Rajasthan (India). The deformation analysis at the level of folds (level three of seven) are presented in this work. The outcrop pattern is an isoclinal fold of D2 generation, whose axis plunges steeply NE’ly with an axial plane trending NNE-SSW. The quartzite band in this Pur Synform was sampled for the purpose of strain analysis. This section parallel to the YZ plane of finite strain ellipsoid was prepared (perpendicular to both Schistosity and the lineation). The accepted methods used to estimate strain are a) Fry method and b) “Isogon Rosette” method. The axial ratio of the strain ellipse and the orientation of the long axis of the strain ellipse were computed for every location. It was seen that the strain ratio is nearly uniform in magnitude. The orientation of the long axis of the strain ellipse (Y direction of the finite strain ellipsoid) is also constant in space and parallel to the axial trace of D2 Synform. From the analysis it was suggested a strong flattening following the buckling. The amount of this flattening strain was computed using the”Isogon rosette” method. We calculated reflects the flattening strain recorded in the rock with the very high constancy of the strain ratio and the orientation of the long axis of the strain ellipse irrespective of the methodology adopted. The results of performed researches bring tectonophysics database up-to-date providing an excellent opportunity for provenance analysis of the Pur-basin using the different types of undulose extinction of the quartzite for development of prospective mining projects around the area including iron deposits.

An intelligent method for generating artificial earthquake records based on hybrid PSO–parallel brain emotional learning inspired model

Simplicity and high speed of brain emotional model made it an effective computational method, which is used in various applications. In this study, a modified model of brain emotional learning is used for generating artificial earthquake records. In fact, in earthquake engineering, strong ground motions are valuable information, which are recorded in each earthquake. These records could be used for linear and nonlinear time-history analysis of structures. Unfortunately, the numbers of recorded strong ground motions are not enough for most areas of the world. Therefore, many seismic codes permit to use artificial records, which contain specific characteristics. Because of the advantages of emotional models, a hybrid PSO–parallel brain emotional learning model is used for generating artificial records based on a dataset of real records in this research. PSO algorithm is combined with the model for finding the best values of learning parameters. In addition, wavelet packet transform is used for decomposing the earthquake signal to use as the suitable output of network. Despite of original brain emotional model, the proposed modified parallel model is applicable on multiinput–output data. Numerical examples show that the proposed model in this research could be successfully used for generating artificial records with acceptable error for statistical properties of the required pseudo spectral acceleration.

Using co-rotational method for cracked frame analysis

A cracked element is formulated using the two-filed Hellinger–Reissner functional. Due to utilization of the linear elastic fracture mechanics, only geometrical nonlinearities can be considered for the cracked element. A clear step-by-step algorithm for the element state determination is also presented. The element flexibility matrix is derived in a basic coordinate system. Co-rotational approach is used to transform the element stiffness matrix and the resisting force vector from the basic system to the global one. The suggested element is applicable for static and dynamic analysis, as well as, the stress intensity factor calculation, and also inverse crack detection. Various numerical problems verify accuracy of the proposed element for linear and nonlinear structural analysis.

Spatial Analysis of Linear Structures in the Exploration of Groundwater

The analysis of linear structures on major geological formations plays a crucial role in resource exploration in the Inner Niger Delta. Highlighting and mapping of the large lithological units were carried out using image fusion, spectral bands (RGB coding), Principal Component Analysis (PCA), and band ratio methods. The automatic extraction method of linear structures has permitted the obtaining of a structural map with 82,659 linear structures, distributed on different stratigraphic stages. The intensity study shows an accentuation in density over 12.52% of the total area, containing 22.02% of the linear structures. The density and nodes (intersections of fractures) formed by the linear structures on the different lithologies allowed to observe the behavior of the region’s aquifers in the exploration of subsoil resources. The central density, in relation to the hydrographic network of the lowlands, shows the conditioning of the flow and retention of groundwater in the region, and in-depth fluids. The node areas and high-density linear structures, have shown an ability to have rejections in deep (pores) that favor the formation of structural traps for oil resources.

APPLICATION OF AEM IN PROGRESSIVE COLLAPSE DYNAMICS ANALYSIS OF R.C. STRUCTURES

The Finite Element Method (FEM) and the other numerical strategies are viably actualized in linear and non-linear analysis of structures. Recently, a new displacement based on Applied Element Method (AEM) has been developed. It is applicable for static and dynamic for both linear and non-linear analysis of framed and continuum structures. In AEM, the structural member is partitioned into virtual elements connected through normal and shear springs representing stresses and strains of certain portion of structure. FEM assumes the material as continuous and can indicate highly stressed region of structure, however it is difficult to model separation of element unless crack location is known. The main advantage of AEM is that it can track the structural collapse behavior going through all phases of the application of loads.In the current research, the application of AEM is illustrated through a non-linear dynamic analysis. Progressive collapse simulation is conducted using Extreme Loading for Structures software (ELS), which follows the AEM. The experimental and analytical works carried by Park et al. [17 and 28] for 1/5 scaled 3 and 5 stories reinforced concrete structures are used for verification. Good matching between the experimental and numerical results has been obtained using ELS. Therefore, it can be confirmed that ELS is capable in simulating the structures’ behavior up to collapse.Furthermore, a study has been made to investigate the effect of considering the floor slabs on progressive collapse. The results show that considering slab in progressive collapse analysis of multistory buildings is important as neglecting the slabs’ contribution leads to incorrect simulation and uneconomic design.

Time discontinuous finite element method for transient response analysis of linear time-varying structures

In this paper, a mixed form of Hamilton’s law of variable mass system is proposed, and then a time discontinuous finite element method for transient response analysis of linear time-varying structures is developed based on the law. As these time-varying parameters are degraded into time-invariant ones, the time discontinuous finite element method for linear time-varying structures is degraded into an unconditionally stable higher-order accurate time integration method for linear time-invariant structures. The performance of the proposed time integration method has been verified and assessed extensively through many numerical examples, including the single-degree-of-freedom system with a time-varying mass and the string and beam structure with a moving mass. Numerical results demonstrate that the proposed time finite element method for linear time-varying structures performs extremely well compare with the Newmark method, the existing time continuous finite element method for linear time-varying structures as well as the combination of linear time-invariant time integration method and time frozen technique.