Computer-aided Structural Analysis Research Articles

Failure analysis of multi-span masonry arch bridges using combination of point cloud data and three-dimensional numerical modeling

Historical structures, including historical bridges, are part of cultural heritage, conveying the traces and characteristic features of past civilizations. To protect historical structures, it is necessary to prepare their 3D photogrammetric documentation, determine detailed geometric and material properties and perform computer-aided structural analysis using appropriate modeling techniques. The aim of this study is to present an effective, reliable and fast multidisciplinary approach for the analysis of historical masonry bridges. The aforementioned approach was illustrated with an example of the historical Halilviran masonry arch bridge and its behavior under possible loadings. Terrestrial laser scanning (TLS) was used to determine the bridge geometry with high accuracy. Point cloud data obtained from TLS was simplified and a three-dimensional CAD-based solid model of the structure was created. The Halilviran Bridge case study summarized in this report was conducted to examine the technical feasibility of using la¬ser scanning technologies for obtaining as-built records for similar historic bridges. A secondary objective was to identify other applications of this technology, notably for other transportation structures, and use numerical methods to assess the seismic behavior and failure model of the bridge. The seismic behavior of the bridge was examined using a finite-element- based macromodeling technique. Nonlinear dynamic analyses were carried out subsequently to identify the most susceptible regions of the bridge. Interpretation of the results, presented in the form of contour plots illustrating tensile damage and maximum displacements, offered a comprehensive depiction of the seismic response across the entire bridge. The methodology employed in this investigation can be viewed as a robust framework for evaluating the seismic response and potential failure of historical structures.

Identification and characterization of a rare variant in apolipoprotein A-IV, p.(V336M), and evaluation of HDL functionality in a Greek cohort with extreme HDL cholesterol levels

High-Density Lipoprotein cholesterol (HDL-C) levels do not correlate well with Coronary Artery Disease (CAD) risk, while HDL functionality affects atherogenesis and is a better prognostic marker for CAD. Often, the extreme HDL-C levels have a multigenic origin. Here, we searched for single-nucleotide polymorphisms (SNPs) in ten genes of HDL metabolism in a Greek cohort with very low (<10th percentile, n = 13) or very high (>90th percentile, n = 21) HDL-C. We also evaluated the association between HDL-C levels, HDL functionality (anti-oxidant capacity) and CAD in the subjects of this cohort. Individuals with low HDL-C levels had higher triglyceride levels, lower apoA-I levels, decreased HDL anti-oxidant capacity and higher incidence of CAD compared with individuals with control or high HDL-C levels. With next generation sequencing we identified 18 exonic SNPs in 6 genes of HDL metabolism and for selected amino acid changes we performed computer-aided structural analysis and modeling. A previously uncharacterized rare apolipoprotein A-IV variant, apoA-IV [V336M], present in a subject with low HDL-C (14 mg/dL) and CAD, was expressed in recombinant form and structurally and functionally characterized. ApoA-IV [V336M] had similar α-helical content to WT apoA-IV but displayed a small thermodynamic stabilization by chemical unfolding analysis. ApoA-IV [V336M] was able to associate with phospholipids but presented reduced kinetics compared to WT apoA-IV. Overall, we identified a rare apoA-IV variant in a subject with low HDL levels and CAD with altered biophysical and phospholipid binding properties and showed that subjects with very low HDL-C presented with HDL dysfunction and higher incidence of CAD in a Greek cohort.

THE FORMATION AND DEVELOPMENT OF CONCEPTS ABOUT THE DESIGN SCHEME OF STRUCTURES

The history of the formation and development of design model concept of a structure accompanied structural mechanics at all stages have is analyzed in the paper. The main principles used at constructing design models are considered. New problems arisen in the process of computer-aided structural analysis also are specified

The Molecular Chaperone TRiC/CCT Binds to the Trp-Asp 40 (WD40) Repeat Protein WDR68 and Promotes Its Folding, Protein Kinase DYRK1A Binding, and Nuclear Accumulation

Trp-Asp (WD) repeat protein 68 (WDR68) is an evolutionarily conserved WD40 repeat protein that binds to several proteins, including dual specificity tyrosine phosphorylation-regulated protein kinase (DYRK1A), MAPK/ERK kinase kinase 1 (MEKK1), and Cullin4-damage-specific DNA-binding protein 1 (CUL4-DDB1). WDR68 affects multiple and diverse physiological functions, such as controlling anthocyanin synthesis in plants, tissue growth in insects, and craniofacial development in vertebrates. However, the biochemical basis and the regulatory mechanism of WDR68 activity remain largely unknown. To better understand the cellular function of WDR68, here we have isolated and identified cellular WDR68 binding partners using a phosphoproteomic approach. More than 200 cellular proteins with wide varieties of biochemical functions were identified as WDR68-binding protein candidates. Eight T-complex protein 1 (TCP1) subunits comprising the molecular chaperone TCP1 ring complex/chaperonin-containing TCP1 (TRiC/CCT) were identified as major WDR68-binding proteins, and phosphorylation sites in both WDR68 and TRiC/CCT were identified. Co-immunoprecipitation experiments confirmed the binding between TRiC/CCT and WDR68. Computer-aided structural analysis suggested that WDR68 forms a seven-bladed β-propeller ring. Experiments with a series of deletion mutants in combination with the structural modeling showed that three of the seven β-propeller blades of WDR68 are essential and sufficient for TRiC/CCT binding. Knockdown of cellular TRiC/CCT by siRNA caused an abnormal WDR68 structure and led to reduction of its DYRK1A-binding activity. Concomitantly, nuclear accumulation of WDR68 was suppressed by the knockdown of TRiC/CCT, and WDR68 formed cellular aggregates when overexpressed in the TRiC/CCT-deficient cells. Altogether, our results demonstrate that the molecular chaperone TRiC/CCT is essential for correct protein folding, DYRK1A binding, and nuclear accumulation of WDR68.

FEM modeling of spatial structural systems in evaluation of the real structural performances

The paper is a review of enhanced concept of CASA (Computer Aided Structural Analysis) software application in FEM modeling of spatial structural systems of bridges, buildings, industrial facilities, machine devices, etc. in evaluation procedures of real structural performances. Contrary to everyday engineering design circumstances, which comprehend, primarily, respect of technical regulations, FEM modeling in case of structural evaluation, needs, in some sense, alternative type of creativity. Chosen examples could be illustrative for this attitude.

Computer-aided structure analysis of an epimerized dehydroepiandrosterone derivative and its biological effect in a model of reactive gliosis

The naturally occurring steroid dehydroepiandrosterone (DHEA) is reported to reduce glial fibrillary acidic protein (GFAP) overexpression in a model of reactive gliosis due to its conversion to estradiol by the enzyme aromatase. In the present study we examined the biological effect of a new epimerized derivative of DHEA, 16α-iodomethyl-13α-dehydroepiandrosterone derivative (16α-iodomethyl-13α-DHEAd, 16α-iodomethyl-13α -androst-5-en-3β,17β-diol), using the same model system, and compared the 3D structure of this molecule with that of DHEA and two steroidal type aromatase inhibitors, formestane and exemestane. The synthetic compound, in contrast to the reported effect of DHEA, was able to reduce GFAP overexpression only if the enzyme aromatase was inhibited. Data obtained from computational calculations fortified by X-ray crystallography revealed that contrary to the nearly planar sterane framework of DHEA, the synthetic derivative 16α-iodomethyl-13α-DHEAd has a bent sterane skeleton, resulting in a 3D structure that is similar to that of formestane or exemestane. Moreover, 16α-iodomethyl-13α-DHEAd resulted to be metabolically more stable than DHEA. The results suggest that epimerization of the sterane skeleton of DHEA inclines the plane of the D ring, leading to a significantly altered biological activity. The synthetic molecule has a DHEA-like effect on GFAP overexpression when the enzyme aromatase is inhibited and the naturally occurring DHEA is ineffective in this respect. On the other hand, based on their structural similarity it can be hypothesized that 16α-iodomethyl-13α-DHEAd applied alone might have a biological effect similar to that of formestane or exemestane.

Helicase-attached novel hybrid ribozymes.

Ribozymes have potential as therapeutic agents and in functional studies of genes of interest. The activities of ribozymes in vivo depend on the accessibility of ribozymes to a cleavage site in the target RNA. At present, the selection of a target site for ribozymes is often based on a computer-aided structural analysis of the target RNA or trial-and-error experiments in which vast numbers of ribozymes are tested systematically. To overcome this problem, we have engineered intracellularly produced ribozymes with unwinding activity in vivo. We found that attachment to ribozymes (hybrid ribozymes) of an RNA motif with the ability to interact with intracellular RNA helicases, which create hybrid ribozymes, enhances ribozyme activity significantly in vivo. Thus, hybrid ribozymes can catalyze cleavage at the specified target site within an RNA in vivo almost independently of the secondary or tertiary structure of the target RNA around the cleavage site.

Object-Oriented Modeling of Structural Analysis and Design with Application to Damping Device Configuration

This paper presents an object-oriented (OO) software framework for computer-aided structural analysis and design research, where different structural analysis methods and design procedures need to be implemented and investigated. The framework is designed with four basic modules: structure, load, analysis, and design. Each module includes a set of cooperating interfaces and classes. Through the predefined interfaces, the framework provides architecture for many structural design applications. A variety of similar entities, such as different design applications, design procedures, and analysis methods, can be built on this architecture by implementing the necessary interfaces. The clearly defined interactions between the modules accommodate the future extensions within the modules. The final OO design of the framework can be communicated by many well-known design patterns, and it is described by unified modeling language. The framework is then customized to the application for optimizing the configuration ...

Kerr-McGee suffers losses

High-Density Lipoprotein cholesterol (HDL-C) levels do not correlate well with Coronary Artery Disease (CAD) risk, while HDL functionality affects atherogenesis and is a better prognostic marker for CAD. Often, the extreme HDL-C levels have a multigenic origin. Here, we searched for single-nucleotide polymorphisms (SNPs) in ten genes of HDL metabolism in a Greek cohort with very low (<10th percentile, n = 13) or very high (>90th percentile, n = 21) HDL-C. We also evaluated the association between HDL-C levels, HDL functionality (anti-oxidant capacity) and CAD in the subjects of this cohort. Individuals with low HDL-C levels had higher triglyceride levels, lower apoA-I levels, decreased HDL anti-oxidant capacity and higher incidence of CAD compared with individuals with control or high HDL-C levels. With next generation sequencing we identified 18 exonic SNPs in 6 genes of HDL metabolism and for selected amino acid changes we performed computer-aided structural analysis and modeling. A previously uncharacterized rare apolipoprotein A-IV variant, apoA-IV [V336M], present in a subject with low HDL-C (14 mg/dL) and CAD, was expressed in recombinant form and structurally and functionally characterized. ApoA-IV [V336M] had similar α-helical content to WT apoA-IV but displayed a small thermodynamic stabilization by chemical unfolding analysis. ApoA-IV [V336M] was able to associate with phospholipids but presented reduced kinetics compared to WT apoA-IV. Overall, we identified a rare apoA-IV variant in a subject with low HDL levels and CAD with altered biophysical and phospholipid binding properties and showed that subjects with very low HDL-C presented with HDL dysfunction and higher incidence of CAD in a Greek cohort.

Initial investigation of mathematical morphology for the digital extraction of the skeletal characteristics of trabecular bone.

To develop a filter utilizing mathematical theory to extract the skeletal patterns of trabecular bone. Studies of morphology in the extraction of patterns of calcification in mammograms provided the theoretical framework. Using these studies as a basis, a morphological filter was applied to extract skeletal patterns from digital images of trabecular bone. Sequential images (subset) were combined in a structured fashion to create an aggregate (sumset) which compared with the original images, skeleton and line skeleton images. Binary images of the skeletal patterns in continuous, round and mesh-like forms were obtained from the original images by processing with the skeleton operation using a disc-shaped single structuring element. The line skeleton operation using line structuring elements with constant directions allowed the extraction of linear and discontinuous patterns. Both the skeleton and line skeleton operations extracted binary subset images which depicted skeletal patterns correlating with the operation sequence. Modification of the morphological filter enhanced the extraction of skeletal characteristics of trabecular bone. A morphological filter may be a useful adjunct in computer-aided structural analysis of bone.

Three-dimensional finite-element computer-aided structural analysis of centrifugal-peening equipment

As part of an extensive computer-aided engineering investigation, a comprehensive three-dimensional finite-element study is made of the critical components of a proposed design of the wheel-assembly of a centrifugal-peening machine. Throughout the investigation, the solid modelling facility of SDRC (GEOMOD) was utilised interactively to create the different geometries of the critical components of the wheel-assembly. Prior to the analysis, these geometries were transferred to the pre-processor (SUPERTAB) for model creation, mesh definition and model checking aspects. The appropriateloads and imposed restraints were also applied interactively. Both structural stress analysis and dynamic response studies were performed using a general purpose finite-element suite of programs known as SUPERB. The results of the structural stress-analysis investigations reveal that the current designs are mostly under-stressed and that a large saving in material can be achieved by reducing the thicknesses of the critical components, without compromising their structural integrity. The resulting modified geometries of the wheel-assembly were also subjected to dynamic response studies. The results indicate that no vibration problems will be experienced by the assembly either at or near to the proposed running speed of the machine of 3000 rev/min.

Three-dimensional finite-element computer-aided structural analysis of centrifugal-peening equipment

As part of an extensive computer-aided engineering investigation, a comprehensive three-dimensional finite-element study is made of the critical components of a proposed design of the wheel-assembly of a centrifugal-peening machine. Throughout the investigation, the solid modelling facility of SDRC (GEOMOD) was utilised interactively to create the different geometries of the critical components of the wheel-assembly. Prior to the analysis, these geometries were transferred to the pre-processor (SUPERTAB) for model creation, mesh definition and model checking aspects. The appropriateloads and imposed restraints were also applied interactively. Both structural stress analysis and dynamic response studies were performed using a general purpose finite-element suite of programs known as SUPERB. The results of the structural stress-analysis investigations reveal that the current designs are mostly under-stressed and that a large saving in material can be achieved by reducing the thicknesses of the critical components, without compromising their structural integrity. The resulting modified geometries of the wheel-assembly were also subjected to dynamic response studies. The results indicate that no vibration problems will be experienced by the assembly either at or near to the proposed running speed of the machine of 3000 rev/min.

SADDLE: A computer-aided structural analysis and dynamic design language—Part I. design system

The SADDLE system is a tool for computer-aided optimal design of structural and mechanical systems. The system is divided into four parts—the preprocessor, the ‘analyzer’, the ‘synthesizer’, and the postprocessor. The structural model and the design data are generated by the preprocessor. The analyzer uses the finite-element method to compute deflections and stresses in the structure. The synthesizer solves the design problem that is cast into a nonlinear programming format. The postprocessor is used to examine the analysis and design results. Different parts of the system interact via a global database. This study presents the design system configuration. In a companion study, the data management part is presented in detail. The user-interface for design is examined first. The design problem formulation, in the nonlinear programming problem context, is presented. The use of utility libraries to achieve this objective with a minimum programming effort is also explained. The article concludes with two numerical examples that belong to two different classes of design problems—a minimum weight design problem and a min-max problem.

SADDLE: A computer-aided structural analysis and dynamic design language—part II. database management system

The SADDLE program is a tool for computer-aided optimal design of structural and mechanical systems. The system is divided into four parts; the pre-processor, the “analyzer”, the “synthesizer” and the post-processor. The structural model and the design data are generated by the preprocessor. The analyzer used the finite-element method to compute deflections and stresses in the structure. The synthesizer solves the design problem that is cast into a nonlinear programming format. The post-processor is used to examine the analysis and design results. Different parts of the system interact via a global database. The database management system is presented in detail, in this part of a two part paper. The data manager has three distinct parts: the data model processor, the resource manager and the I/O manager. Both the relational and hierarchical data models are supported. Tuning parameters are provided to enhance computational efficiency on different computers. The emphasis is on friendlier user-system interaction; free-format input, error recoveries, and easy means to create, edit, and update information.

Computer-aided structural analysis of organic compounds by an artificial intelligence system

The computer program SEAC is designed to elucidate the structure of organic compounds comprising C (up to 40 C atoms in a molecule), H, N, O, S, Cl, Br and/or I atoms. Artificial intelligence techniques are exploited for empirical interpretation of spectralstructural correlations obtained directly from i.r., 1H-n.m.r. and u.v. spectra. SEAC works on five levels depending on the entropy of the information input on tested molecules. The computer prints out a set of alternative substructures (levels I–IV) or a set of complete structures which are consonant with the input data.

Computer-aided structural analysis and design of the 37-storey Los Angeles Bonaventure Hotel

The paper briefly describes and summarizes the computed-aided analyses and design for a complex convention hotel structure in Los Angeles. Seismic analyses, upon which structural steel sizing was based, were both static and dynamic. The latter were carried out for two postulated levels of seismic ground motion, and included both response-spectrum and time-history methods.&#x0D; Columns, column splices and joint details at beam to column connections were designed using a computer program.