Global Structural Analysis Research Articles

A Component-based Approach to Modelling Beam Bottom Flange Buckling at Elevated Temperatures

In this study, an analytical model of the combination of beam-web shear buckling and bottom-flange buckling at elevated temperatures has been created. This analytical model is able to track the force-deflection path in the post-buckling stage. A range of 3D finite element models has been created using the ABAQUS software. Comparisons have been carried out between the proposed analytical model, finite element modelling and the existing Dharma’s theoretical model. Comparisons indicate that the proposed method is able to provide with accurate predictions for Class 1 and Class 2 beams, and performs better than the existing model, especially for slender beams. A component-based model has been created based on the analytical model, and in due course to be implemented into the software Vulcan for global structural fire analysis.

Nonlinear stability analysis of the frame structures

In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3) and national (JUS) standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.

Staatsbürgerschaft, Gender und globale Ungleichheiten

The category gender has marked the institution of citizenship from the modern / colonial outset, and both citizenship and gender have been providing crucial factors for extreme inequalities between countries. In order to elaborate on this thesis, the article introduces a global and postcolonial perspective on citizenship and gender. In a second step, the article discusses »acts of citizenship« such as marriage, motherhood and sex tourism to subvert, reinscribe and appropriate engendered colonial-racialized structures. Finally, the article advocates a stronger focus on persistent colonial intersectional gender relations for the analysis of global power structures.

Steel Structure Apartment Extensions for Existing Large Prefabricated Panel Collective Dwellings

The Romanian existing building stock of collective dwellings is in a vast majority composed of reinforced concrete large prefabricated panel blocks of flats, erected during Communism. According to the 1992 Census, these standardized and widespread buildings housed almost 60 percent of the urban population of the country.Due to the small, inflexible apartments on one hand and the changing living conditions of the contemporary Romanian society on the other, a need for extending the inner surface of the existing flats has been identified. This situation led to the adoption of technically restrictive ground-floor spatial additions and other vernacular solutions that are being applied to upper stories, some of them not being able to provide, in many cases, any forms of long term structural guarantee to their users.The present paper describes a prefabricated steel structure solution for cantilevered apartment extensions that can be independently attached to the façade, as well as some technical connecting details to the existing building. A global structural analysis performed on a virtual model depicting a widespread type of block of flats (Model 770) proves the non-intrusive influence the cantilevered apartment extensions have over the existing buildings, in multiple different scenarios of attachments. Moreover, a FEM analysis of the proposed details further shows the reliability of the examined solution.

Component-based model of buckling panels of steel beams at elevated temperatures

Both bottom-flange buckling and beam-web shear buckling have been observed in many full-scale fire tests in the vicinity of beam-to-column connections. These phenomena can influence the load redistribution within the adjacent connections and the global structural behaviour, detrimentally affecting the structural overall fire resistance. However, existing models for bottom-flange buckling overestimate the structural resistance when the beam is slender. In this work, a new analytical model has been created to predict both of these types of buckling behaviour in steel beams in the vicinity of beam-to-column connections at elevated temperatures. The model considers the individual effects of both buckling modes, as well as their interaction. It is capable of predicting the force–deflection relationship of the buckling zone from the initial elastic loading stage to run-away failure. The new analytical model has been compared with the existing Dharma's model and a range of 3D finite element simulations created using the ABAQUS software. Comparisons have shown that the proposed method gives better predictions than Dharma's model. A component-based model of the buckling zone has been created on the basis of this new analysis. The component-based model can provide sufficient accuracy, and will be implemented in the software Vulcan for performance-based global structural fire analysis.

Development of a General Component-Based Connection Element for Structural Fire Engineering Analysis

This paper reports on the development of a general-purpose Eurocode-compliant component-based connection finite element for steel-to-steel joints in fire. The development begins by utilising the temperature-dependent connection component characteristics previously developed at the University of Sheffield to create a component-based connection finite element to model flush endplate connections. Subsequently the element was extended to a new connection type with high ductility, the reverse channel. The component models have been developed for the reverse channel under tension and compression. The element has been incorporated into the nonlinear global structural analysis program Vulcan, in which it has been used along with a static-dynamic formulation. The use of the element is illustrated by modelling a fire test at the University of Manchester in which reverse channel connections were used.

Global response sensitivity analysis of uncertain structures

The problem of characterizing global sensitivity indices of structural response when system uncertainties are represented using probabilistic and (or) non-probabilistic modeling frameworks (which include intervals, convex functions, and fuzzy variables) is considered. These indices are characterized in terms of distance measures between a fiducial model in which uncertainties in all the pertinent variables are taken into account and a family of hypothetical models in which uncertainty in one or more selected variables are suppressed. The distance measures considered include various probability distance measures (Hellinger, l2, and the Kantorovich metrics, and the Kullback–Leibler divergence) and Hausdorff distance measure as applied to intervals and fuzzy variables. Illustrations include studies on an uncertainly parametered building frame carrying uncertain loads.

Reconstructing the invasion history ofHeracleum persicum(Apiaceae) into Europe

Sparse, incomplete and inappropriate historical records of invasive species often hamper invasive species management interventions. Population genetic analyses of invaders might provide a suitable context for the identification of their source populations and possible introduction routes. Here, we describe the population genetics of Heracleum persicum Desf. ex Fisch and trace its route of introduction into Europe. Microsatellite markers revealed a significantly higher genetic diversity of H. persicum in its native range, and the loss of diversity in the introduced range may be attributed to a recent genetic bottleneck. Bayesian cluster analysis on regional levels identified three and two genetic clusters in the native and the introduced ranges, respectively. A global structure analysis revealed two worldwide distinct genetic groups: one primarily in Iran and Denmark, the other primarily in Norway. There were also varying degrees of admixture in England, Sweden, Finland and Latvia. Approximate Bayesian computation indicated two independent introductions of H. persicum from Iran to Europe: the first one in Denmark and the second one in England. Finland was subsequently colonized by English populations. In contrast to the contemporary hypothesis of English origin of Norwegian populations, we found Finland to be a more likely source for Norwegian populations, a scenario supported by higher estimated historical migration from Finland to Norway. Genetic diversity per se is not a primary determinant of invasiveness in H. persicum. Our results indicate that, due to either pre-adaptations or rapid local adaptations, introduced populations may have acquired invasiveness after subsequent introductions, once a suitable environment was encountered.

Fatigue Reliability Analysis for Brace–Column Connection Details in a Semisubmersible Hull1

Semisubmersible floating platforms used in offshore deep or ultradeep water environments have hull structures that are comprised of vertical cylinders (columns) connected by braces, pontoons, etc. Several of the connections between these various members are susceptible to fatigue damage. In fatigue damage assessment or fatigue reliability analysis, a global structural response analysis is typically carried out using a finite element (FE) model where internal forces or stresses in the various members are evaluated for specified sea states measured at the site. Of specific interest in the present study is the fatigue reliability analysis of brace-column connection details in a semisubmersible hull unit for selected Brazilian environmental conditions. Stress concentration factors (SCFs) for the selected critical hot spots are applied to the nominal component stresses due to axial forces and biaxial bending. The hot-spot stress response spectra are used with various spectral methods—referred to as Rayleigh, modified Rayleigh (with bandwidth correction), and Dirlik—to estimate fatigue damage using Miner's rule. Uncertainties in some parameters used in the fatigue life assessment are considered and the probability of fatigue failure in the last operational year of the structure is estimated.

Rethinking "energy nationalism": a study of the relationship between nation states and companies in the oil industry

ABSTRACTThe term "energy nationalism" is frequently used by academic literature and media, but usually without adequate conceptual accuracy. Despite this, a set of papers deepens the discussion on the relationship between nation states and the energy industry, especially the oil sector. These papers allow identifying fundamental elements to understand the energy nationalism, either complementary or divergent between each other. Thus, this study aims at presenting an interpretation of the concept that fills the gaps left by the above mentioned literature based on a global analysis of the oil industry structure and its historical evolution since the mid-19thcentury.

Equivalent design wave approach for structural analysis of floating pendulum wave energy converter

Offshore structures are installed in a variety of water depths, under harsh environments, for long stretches of time, and waves are the most interrelated factor directly affecting their structural integrity. Thus, such structures should be designed to satisfy the demands of wave characteristics. In the preliminary structural design phase, a method for predicting non-linear random wave characteristics and extreme wave conditions must be determined. A structural response is not a linear value corresponding to maximum wave height, due to the related periods; that is, certain waves of less than maximum height may have greater effects on a structure depending on the wave period. This study focuses on selecting design conditions that generate a significant hydrodynamic load on a floating pendulum wave energy converter (FPWEC). For this purpose, it finds an equivalent regular wave height capable of generating the same hydrodynamic load, critical wave period and wave direction by conducting a response analysis. Generally, the subsequent equivalent design wave conditions are used to investigate an FPWEC's global strength. This study also applies a global structural analysis for the FPWEC using the determined equivalent design wave. The obtained results should be useful for understanding the global structural responses of FPWECs.

Fatigue life estimation of tubular joints – a comparative study

AbstractIn fatigue analysis, the structural detail of tubular joint has taken great attention among engineers. The DNV/GL‐RP‐0005 is covering this topic quite well for simple and clear joint cases. For complex joint and geometry, where joint classification is not available and there is limitation on validity range of non‐dimensional geometric parameters, the challenges become a fact among engineers. The classification of joint is an important factor to consider in fatigue analysis. These joint configurations are identified by the connectivity and the load distribution of tubular joints. To overcome these problems to some extent, this paper compares the fatigue life of tubular joints in offshore jacket according to the stress concentration factors (SCF) in DNV/GL‐RP‐0005 and finite element method employed in Abaqus/CAE. The paper presents the geometric details, material properties and load history of the considered jacket structure. It then describes the global structural analysis and identification of critical tubular joints for fatigue life estimation. Hence, fatigue life is determined based on the guidelines provided in design codes. Fatigue analysis of tubular joints is conducted using the finite element employed in Abaqus/CAE as the next major step. Finally, predicted SCFs and fatigue lives are compared, and these observations tend to conclude that even though the fatigue life, which is calculated based on code given SCFs, provides more realistic prediction to the simple uniplanar joints, there is a doubt for complex joints and geometry, where joint classification is not available. Also, the study emphasized that it is very important to preciously investigate SCFs by considering accurate geometry of complex tubular joints for a good judgement of fatigue life.

Single-spin asymmetries inWboson production at next-to-leading order

We present an analytic next-to-leading order QCD calculation of the partonic cross sections for single-inclusive lepton production in hadronic collisions, when the lepton originates from the decay of an intermediate electroweak boson and is produced at high transverse momentum. In particular, we consider the case of incoming longitudinally polarized protons for which parity-violating single-spin asymmetries arise that are exploited in the $W$ boson program at RHIC to constrain the proton's helicity parton distributions. Our calculation enables a very fast and efficient numerical computation of the relevant spin asymmetries at RHIC, which is an important ingredient for the inclusion of RHIC data in a global analysis of nucleon helicity structure. We confirm the validity of our calculation by comparing with an existing code that treats the next-to-leading order cross sections entirely numerically by Monte-Carlo integration techniques. We also provide new comparisons of the present RHIC data with results for some of the sets of polarized parton distributions available in the literature.

Frequency-Domain Substructure Isolation for Local Damage Identification

This paper proposes a frequency-domain method of substructure identification for local health monitoring using substructure isolation method (SIM). The first key step of SIM is the numerical construction of the isolated substructure, which is a virtual and independent structure that has the same physical parameters as the real substructure. Damage identification and local monitoring can be then performed using the responses of the simple isolated substructure and any of the classical methods aimed originally at global structural analysis. This paper extends the SIM to frequency domain, which allows the computational efficiency of the method to be significantly increased in comparison to time domain. The mass-spring numerical model is used to introduce the method. Two aluminum beams with the same substructure are then used in experimental verification. In both cases the method performs efficiently and accurately.

Meta-Analysis of Retrograde Signaling in Arabidopsis thaliana Reveals a Core Module of Genes Embedded in Complex Cellular Signaling Networks

Plastid-to-nucleus signaling is essential for the coordination and adjustment of cellular metabolism in response to environmental and developmental cues of plant cells. A variety of operational retrograde signaling pathways have been described that are thought to be triggered by reactive oxygen species, photosynthesis redox imbalance, tetrapyrrole intermediates, and other metabolic traits. Here we report a meta-analysis based on transcriptome and protein interaction data. Comparing the output of these pathways reveals the commonalities and peculiarities stimulated by six different sources impinging on operational retrograde signaling. Our study provides novel insights into the interplay of these pathways, supporting the existence of an as-yet unknown core response module of genes being regulated under all conditions tested. Our analysis further highlights affiliated regulatory cis-elements and classifies abscisic acid and auxin-based signaling as secondary components involved in the response cascades following a plastidial signal. Our study provides a global analysis of structure and interfaces of different pathways involved in plastid-to-nucleus signaling and a new view on this complex cellular communication network.

Global analysis of population structure, spatial and temporal dynamics of genetic diversity, and evolutionary lineages of Iris yellow spot virus (Tospovirus: Bunyaviridae).

Thrips-transmitted Iris yellow spot virus is an economically important viral pathogen of Allium crops worldwide. A global analysis of known IYSV nucleocapsid gene (N gene) sequences was carried out to determine the comparative population structure, spatial and temporal dynamics with reference to its genetic diversity and evolution. A total of 98 complete N gene sequences (including 8 sequences reported in this study) available in GenBank and reported from 23 countries were characterized by in-silico RFLP analysis. Based on RFLP, 94% of the isolates could be grouped into NL or BR types while the rest belonged to neither group. The relative proportion of NL and BR types was 46% and 48%, respectively. A temporal shift in the IYSV genotypes with a greater incremental incidence of IYSVBR was found over IYSVNL before 2005 compared to after 2005. The virus population had at least one evolutionarily significant recombination event, involving IYSVBR and IYSVNL. Codon substitution studies did not identify any significant differences among the genotypes of IYSV. However, N gene codons were minimally positively selected, moderately negatively selected denoting the action of purifying selection, thus rejecting the theory of neutral mutation in IYSV population. However, one codon position (139) was found to be positively selected in all the genotypes. Population selection statistics in the IYSVBR, IYSVNL genotypes and in the population as a whole also revealed the action of purifying selection or population expansion, whereas IYSVother displayed a decrease in population size. Genetic differentiation studies showed inherent differentiation and infrequent gene flow between IYSVBR and IYSVNL genotypes corroborating the geographical confinement of these genotypes. Taken together the study suggests that the observed diversity in IYSV population and temporal shift in IYSVBR genotype is attributable to genetic recombination, abundance of purifying selection, insignificant positive selection and population expansion. Restricted gene flow between the two major IYSV genotypes further emphasizes the role of genetic drift in modeling the population architecture, evolutionary lineage and epidemiology of IYSV.

Global static and stability analysis of thin-walled structures with open cross-section using FE shell-beam models

The finite shell-beam models for static and global stability analysis of thin-walled structures with open cross-section are proposed. The discretization using thin-walled beam elements is connected with the space discretization of some parts of the frame. The space joint element, formulated using only translational degrees of freedom on cross-sections connecting the joint with the thin-walled beams and the so-called transition elements, defined between the beam and the shell nodes are used for consistent coupling beams and shell parts.

The WEST project mechanical analysis of the divertor structure according to the nuclear construction code

The Tore Supra tokamak is being transformed in an x-point divertor fusion device in the frame of the WEST project, launched in support to the ITER tungsten divertor strategy. The installation of coils inside the vacuum vessel led to the design of a divertor supporting platform able to meet the project requirements and the associated electromagnetic loads. This paper illustrates the design, the method and the results of the thermomechanical elastic stress analyses performed in 2012. The validation of the integrity of the structure is based on the compliance with RCCMR design criteria (even though these Design and Construction rules for Mechanical Components of nuclear installations are not required for such experimental fusion device).Several 3D analyses are performed with the ANSYS code. The major one is a global analysis of half structure which determinates the stresses in the main part of the components. It gives an idea of the areas which needs local analyses. It also provides the interface loads for junction studies or simplified local model.

Insights into the genetic structure and diversity of 38 South Asian Indians from deep whole-genome sequencing.

South Asia possesses a significant amount of genetic diversity due to considerable intergroup differences in culture and language. There have been numerous reports on the genetic structure of Asian Indians, although these have mostly relied on genotyping microarrays or targeted sequencing of the mitochondria and Y chromosomes. Asian Indians in Singapore are primarily descendants of immigrants from Dravidian-language–speaking states in south India, and 38 individuals from the general population underwent deep whole-genome sequencing with a target coverage of 30X as part of the Singapore Sequencing Indian Project (SSIP). The genetic structure and diversity of these samples were compared against samples from the Singapore Sequencing Malay Project and populations in Phase 1 of the 1,000 Genomes Project (1 KGP). SSIP samples exhibited greater intra-population genetic diversity and possessed higher heterozygous-to-homozygous genotype ratio than other Asian populations. When compared against a panel of well-defined Asian Indians, the genetic makeup of the SSIP samples was closely related to South Indians. However, even though the SSIP samples clustered distinctly from the Europeans in the global population structure analysis with autosomal SNPs, eight samples were assigned to mitochondrial haplogroups that were predominantly present in Europeans and possessed higher European admixture than the remaining samples. An analysis of the relative relatedness between SSIP with two archaic hominins (Denisovan, Neanderthal) identified higher ancient admixture in East Asian populations than in SSIP. The data resource for these samples is publicly available and is expected to serve as a valuable complement to the South Asian samples in Phase 3 of 1 KGP.

Avoidable errors in deposited macromolecular structures: an impediment to efficient data mining.

Whereas the vast majority of the more than 85 000 crystal structures of macromolecules currently deposited in the Protein Data Bank are of high quality, some suffer from a variety of imperfections. Although this fact has been pointed out in the past, it is still worth periodic updates so that the metadata obtained by global analysis of the available crystal structures, as well as the utilization of the individual structures for tasks such as drug design, should be based on only the most reliable data. Here, selected abnormal deposited structures have been analysed based on the Bayesian reasoning that the correctness of a model must be judged against both the primary evidence as well as prior knowledge. These structures, as well as information gained from the corresponding publications (if available), have emphasized some of the most prevalent types of common problems. The errors are often perfect illustrations of the nature of human cognition, which is frequently influenced by preconceptions that may lead to fanciful results in the absence of proper validation. Common errors can be traced to negligence and a lack of rigorous verification of the models against electron density, creation of non-parsimonious models, generation of improbable numbers, application of incorrect symmetry, illogical presentation of the results, or violation of the rules of chemistry and physics. Paying more attention to such problems, not only in the final validation stages but during the structure-determination process as well, is necessary not only in order to maintain the highest possible quality of the structural repositories and databases but most of all to provide a solid basis for subsequent studies, including large-scale data-mining projects. For many scientists PDB deposition is a rather infrequent event, so the need for proper training and supervision is emphasized, as well as the need for constant alertness of reason and critical judgment as absolutely necessary safeguarding measures against such problems. Ways of identifying more problematic structures are suggested so that their users may be properly alerted to their possible shortcomings.