Stringer System Research Articles

Elastic riveted perforated plate with cracks

The paper proposes the problem solution for interaction of two following factors: perforated plate reinforcement by a stringer system and its loosening by a number of circular holes and two cracks along the x-axis near each hole. The hole and crack edges are free from external loads. The riveted plate is subjected to tension by strengthening ribs via constant stresses. The action of riveted reinforcing strengthening ribs is modeled by unknown concentrated forces applied to anchor points.An effective solution is proposed for the reinforcement by transverse strengthening ribs of plates weakened by stress concentrators (holes, cracks) under loading. The stress intensity and ultimate loads are found depending on geometrical and physical parameters of the problem.

Modeling of partial closure of slots system in perforated isotropic medium reinforced by stringers

On the basis of the methods of the theory of elasticity, a mathematical description of the model of partial closure of a system of slits in a perforated isotropic medium with foreign transverse inclusions is given. Such a medium can be considered as a perforated unrestricted plate, reinforced by a system of stringers of a very narrow cross section. It is believed that the medium is weakened by a periodic system of circular holes and rectilinear variable width slits. The variable width of the slits is comparable to elastic deformations. A method of solving the periodic elastic problem and an explicit method of constructing complex potentials corresponding to the unknown normal displacements along rectilinear slits are applied. General representations of solutions are constructed, that describe a class of problems with a periodic distribution of stresses outside circular holes and slits with contact zones. To determine the unknown contact stresses and sizes of contact zones, a singular integral equation is obtained, that reduces to a system of nonlinear algebraic equations. The system of algebraic equations can be solved by the method of successive approximations. As a result, the contact stresses and sizes of contact zones have been found.

Innovative System for Curved Precast Posttensioned Concrete I-Girder and U-Girder Bridges

AbstractA new system for framing curved bridges using precast prestressed concrete girders is introduced. The main feature of the new system is the use of relatively short [6–12 m (20–40 ft)] straight girder segments that are joined and posttensioned to form a full-length curved girder. The visual impact of the deviation of these chords from a true curve is indistinguishable by a casual observer. However, it greatly simplifies production of precast curved girders, which are currently produced in full-span piece lengths. Another feature of the new system is utilization of two of the most commonly used precast concrete girder shapes: I-girder and U-girder. The straight-line bridge girder forms and prestressing bed can be used for the proposed curved girder system, saving considerable initial capital and allowing more precasters to compete for this type of bridge. The result is a better value of the cost-effective precast concrete stringer system compared to curved steel, cast-in-place concrete, and segmenta...

Methods of integrated computer-aided design of structural elements of the aircraft

Previously applied methods of designing aircraft based on two-dimensional geometric models that made it impossible to take into account all the necessary design and technological features. It was a prerequisite for the development of an integrated methodology that includes design and computer simulation of three-dimensional parametric design of the aircraft as a whole and its individual parts [2-5]. In this paper, the method of computer-aided design stringer at the master model geometry and space allocation wing aircraft.In article approaches to integrated computer-aided design. These types of problems preliminary design and the method of calculation of typical aircraft structural elements for example longitudinal force element sets as stringer. Also, the algorithm constructs a fully stringer system aided design of integrated Siemens NX. What can shorten the design time and use it as a reference for the calculation and further change just values for other dimensions stringers.Methods integrated design ensure the application of standard parametric analytical stringers in the calculation of aerodynamics and strength, life and vitality, weight of the aircraft and its alignment, safety of structures, as well as technological preparation of production and quality control, maintenance and repair.Considered aided design techniques can be extended to other than the stringers typical elements airframe.

О передаче нагрузок от системы разнородных стрингеров к упругому полупространству или слою при антиплоской деформации.

О передаче нагрузок от системы разнородных стрингеров к упругому полупространству или слою при антиплоской деформации.

Divergence of a plate discretely supported by the stringer system

An approximate solution of the divergence problem, that is, of the static instability of a plate discretely supported by a system of stiffening ribs (stringers) in the gas flow. The critical velocity of divergence is determined in one-term approximation and the influence of stringers on it is analyzed.

Modeling of partial closure of cracks in a perforated isotropic medium reinforced by a regular system of stringers

A mathematical model of partial closure of a crack in a perforated isotropic medium with a system of rectilinear foreign inclusions is constructed. Such a medium can be interpreted as an unbounded plate reinforced by a regular system of ribs whose cross sections are shaped as narrow rectangles. The medium is assumed to be attenuated by a periodic system of circular holes and straight-line cracks. Determination of unknown contact stresses and contact zone sizes is reduced to solving a singular integral equation, which is transformed by an algebraization procedure to a system of nonlinear algebraic equations solved by the method of consecutive approximations.

Interaction of cracks with bonds between their faces in an isotropic medium reinforced by a regular system of stringers

A problem of an elastic isotropic medium with a system of foreign (transverse with respect to crack alignment) rectilinear inclusions is considered. The medium is assumed to be attenuated by a periodic system of rectilinear cracks with zones where the crack faces interact with each other. These zones are assumed to be adjacent to the crack tips, and their sizes can be commensurable with the crack size. Interaction between the crack faces in the tip zone is modeled by introducing bonds (adhesion forces) between the cracks with a specified strain diagram. The boundary-value problem of the equilibrium of a periodic system of cracks with bonds between their faces under the action of external tensile loads and forces in the bonds is reduced to a nonlinear singular integrodifferential equation with a kernel of the Cauchy kernel type. The condition of critical equilibrium of the cracks with the tip zones is formulated with allowance for the criterion of critical tension of the bonds. A case of a stress state of the medium containing zones where the crack faces interact with each other is considered.

Framework for evaluating clustering algorithms in duplicate detection

The presence of duplicate records is a major data quality concern in large databases. To detect duplicates, entity resolution also known as duplication detection or record linkage is used as a part of the data cleaning process to identify records that potentially refer to the same real-world entity. We present the Stringer system that provides an evaluation framework for understanding what barriers remain towards the goal of truly scalable and general purpose duplication detection algorithms. In this paper, we use Stringer to evaluate the quality of the clusters (groups of potential duplicates) obtained from several unconstrained clustering algorithms used in concert with approximate join techniques. Our work is motivated by the recent significant advancements that have made approximate join algorithms highly scalable. Our extensive evaluation reveals that some clustering algorithms that have never been considered for duplicate detection, perform extremely well in terms of both accuracy and scalability.

Ultimate state of a plate with a regular system of stringers and cracks issuing from a circular hole

A fracture mechanics problem on crack development in a stiffened plate with a round hole is considered. A crack model with domains in which crack borders interact is used. This interaction in the end domain is simulated by introducing bonds (cohesive forces) between the crack borders. A boundary problem on the equilibrium of cracks issuing from the surface around the circular hole and exposed to external tensile loads is reduced to a nonlinear singular integral equation. From solving this equation, stresses in bonds are found. The condition of crack development is formulated taking into account a criterion of ultimate opening of interparticle bonds of material.

Stability and natural frequencies of functionally graded stringer-reinforced panels

The paper presents an analysis of stability and free vibrations of rectangular functionally graded panels reinforced by a system of parallel stringers. The exact solution of the problem is illustrated for large aspect ratio panels with simply supported long edges and arbitrary boundary conditions along the short edges (hereafter the reference to an “exact solution” implies a closed-form solution in the content of the theory of plates). The spacing between the stringers and the cross sections of individual stringers can be arbitrary. In the particular case where identical stringers are equally spaced, the solution is simplified using the smeared stiffeners technique. The optimization problem concerned with the choice of stringers and their spacing in the situations where the buckling loads or fundamental frequencies are prescribed is also considered. The closed-form solution of the optimization problem is shown in the case of blade stringers.

Fracture of an isotropic medium strengthened with a regular system of stringers

An isotropic medium containing a system of foreign transverse rectilinear inclusions is considered. Such a medium can be interpreted as an infinite plate strengthened with a regular system of ribs (stringers) whose cross section is a very narrow rectangle. The medium is weakened by a periodic system of rectilinear cracks. The action of the stringers is re placed by unknown equivalent concentrated forces at the points of their connection with the medium. The boundary-value problem on equilibrium of the periodic system of cracks under the action of external tensile forces is reduced to a singular integral equation, from the solution of which the stress in tensity factors are found. The condition of limiting state of equilibrium of the cracks is formulated based on a criterion of brittle fracture. The stress state in the case where crack faces come into a partial contact is also considered.

Theoretical and experimental analysis of FRP bridge deck under cold temperatures

The large temperature difference (~120°F) between the top and bottom of a fiber-reinforced polymer (FRP) bridge deck is attributed to low thermal conductivity of FRP materials and low thermal mass because of hollow core FRP decks. In this study, laboratory tests were conducted on glass FRP deck modules under low temperature gradient. A theoretical beam model was used to analyse the FRP deck-steel stringer system while closed form solutions (based on Macro Approach and Navier– Levy method) were derived using the plate bending theory for FRP deck modules. In addition, thermal stress evaluations from field test data were evaluated using theoretical models. The laboratory test data indicated that the FRP decks sag when they were subjected to negative temperature difference. Deflections and expansion of the deck top increased as the difference between the Ttop and Tbottom increased. Partial deck restraint, provided by steel stringers, resulted in partially induced stresses.

A Crack with Interfacial Bonds in an Isotropic Medium Strengthened with a Regular System of Stringers

An isotropic medium containing a system of foreign transverse rectilinear inclusions is considered. Such a medium can be interpreted as an infinite plate strengthened with a regular system of ribs (stringers) whose cross section is a very narrow rectangle. The medium is weakened by a rectilinear crack. The action of the stringers is replaced with unknown equivalent concentrated forces at the points of their connection with the medium. A model of a crack with areas where its faces interact with each other is investigated. This interaction is modeled by introducing bonds (adhesion forces) between faces in the crack tip zone. The boundary-value problem on equilibrium of the crack under the action of external tensile forces is reduced to a nonlinear singular integral equation, from the solution of which the tractions in the bonds are found.

The Stringer System — A Truss Model of Membrane Shells for Analysis and Design of Boundary Conditions

This paper deals with the problem: What sort of boundary conditions are to be prescribed on the edge of a shell that is to be in a statically determinate membrane state? Triangulated single layer trusses have been suggested as a model for membrane shells by (Calladine 1983) and have been investigated by (Szabo and Tarnai 1992). However, these efforts have not solved the problem completely. The paper presents a triangular single layer truss system – the stringer system – which differs from the above mentioned models in two ways: the systematic topology makes it relatively simple to control whether or not the system is statically and geometrically/kinematically determinate, the geometry corresponds to the curvature of the considered surface and ensures that the system can be applied as a valid static and geometric model for the membrane shell. In most cases, the stringer system regarded as a static model of membrane shells leads to the same results as the theory of partial differential equations, as investigated by (Tarnai 1980a, 1981, 1983). However, some new boundary conditions for shells with positive and zero Gaussian curvature have been found and the types of supports and the connection between statical and geometrical determinacy have been further generalised. The paper is based on parts of the Ph.D. Thesis by (Almegaard 2003).

Evolution and source of ore fluids in the stringer system, Hellyer VHMS deposit, Tasmania, Australia: evidence from fluid inclusion microthermometry and geochemistry

The Hellyer deposit is a classic, large tonnage, high-grade, mound style volcanic-hosted massive sulphide (VHMS) deposit in the Cambrian Mt Read Volcanic belt of western Tasmania. In the footwall directly underlying the deposit, there is an extensively altered pipe which contains a well developed and preserved stringer zone. The vein paragenesis at Hellyer indicates that premineralization Stage 1 veins consist entirely of quartz, and occur throughout the alteration pipe. The synmineralization Stage 2 veins are the most abundant veins in the stringer zone and consist of three sub-stages: Stage 2A veins of crustiform quartz, pyrite, andc arbonate with minor amounts of chalcopyrite, sphalerite and galena, Stage 2B veins with abundant base metal sulphides, minor quartz, carbonate and barite gangue and Stage 2C veins of coarsely crystalline barite with variable amounts of pyrite, sphalerite, galena and carbonate. Stages 3–6 veins are postmineralization veins and are related to the Devonian Tabberabberan Orogeny. Textural, petrographic and microthermometric investigations of fluid inclusions in the Hellyer stringer system indicate that Type I, primary, liquid-vapour inclusions occur along growth planes of crustiform quartz crystals or within colour banding of zoned sphalerite. These inclusions are 10–15 μm in size, and yielded homogenisation temperatures of 170–220°C in early 2A veins, 165–322°C in main-stage 2B veins and 190–256°C in late-stage 2C veins. These data suggest a waxing and waning thermal history. However, the average salinity remained between 8–11 NaCl equiv. wt% in all Stage 2 veins. Chalcopyrite-bearing primary fluid inclusions have been recognised in the base metal-rich Stage 2B veins. No evidence for presence of CO 2 (e.g. formation of clathrates) was recorded by microthermometry. However, Laser Raman spectroscopic (LRS) analysis indicates the presence of CO 2 (< 1 mole%) in the Stage 2B veins, and no detectable CO 2 in 2A and 2C vein stages. Semi-quantitative SEM/WDS microprobe analyses of fluid inclusion decrepitates indicate that the Hellyer ore fluid was enriched in potassium and calcium but depleted in magnesium relative to seawater. PIXE microanalysis of fluid inclusions in quartz indicates that the Stage 2B ore fluids have a significantly higher base metal concentration compared to the Stage 2A veins. The postmineralization Stage 4 veins have a variable but lower base metal content. In this study, there was no fluid inclusion evidence of boiling. Cation composition, higher salinities relative to seawater and the presence of CO 2, suggest that recycled seawater alone cannot be the sole source of the ore fluids. This interpretation is in agreement with previous isotopic studies in the Hellyer stringer system. Although direct input of bulk ore constituents from a magma chamber cannot be demonstrated from the present fluid inclusion data, such a contribution of ore fluids from a magmatic source cannot be ruled out. The possible input from the magmatic source may have occurred during the base metal-rich Stage 2B vein formation characterised by the intensifying temperature of deposition, higher base metals and CO 2 contents.

Primary and tectonic features of the Currawong Zn-Cu-Pb(-Au) massive sulfide deposit, Benambra, Victoria; implications for ore genesis

The Late Silurian Currawong Zn-Cu-Pb(-Au) massive sulfide deposit is located in the northeastern highlands of Victoria, southeastern Australia. The Currawong deposit forms two strata-bound concordant massive sulfide lenses which have been dissected by late subvertical faulting. Each massive sulfide lens possesses a concordant stringer system in the footwall to the massive sulfides, which presumably represent major hydrothermal fluid pathways to the mineralization. Host rocks are comprised of subaqueous rhyodacitic to andesitic breccias and coherent volcanic rocks, and equivalent (temporally and spatially) epiclastic rocks that are contained in, and interfinger, with a monotonous succession of turbidites. The geometry and distribution of ore types in the Currawong deposit are characteristic of both sheet- and layered-type deposits as described in Australia. Mineralization is divided into six types: Pb-Zn, pyrite Zn, massive pyrite, pyrite-magnetite, footwall stringer, and overprinting veins and breccias related to local remobilization of base metal sulfides during deformation. Three generations of deformation are recognized in the host stratigraphy. These can be correlated to deformation textures observed within the ore based on consistent structural geometries; unequivocal evidence that mineralization predates the earliest deformation. The internal stratigraphy of the deposit is erratic, with ore facies changing laterally over tens of meters; however, a general vertical zonation of ore types exists within both lenses. From hanging wall to footwall, the zonation is exemplified by: Pb-Zn ore, pyrite Zn ore, intermixed pyrite Zn and massive pyrite ores, and Pb-Zn and pyrite Zn ore associated with sporadic occurrences of hydrothermally altered volcanic rocks. This zonation can be repeated up to three times in lens 1, forming a cyclic distribution. Pyrite-magnetite ore occurs at the base of the deposit located immediately above footwall stringer mineralization. Metal zonation..

Reinforcement of a thin cracked plate by a system of parallel stringers

The stress-strain state of an infinite plate with curvilinear cracks reinforced by a system of parallel stringers is investigated. The stringers are attached to the plate by riveting. It is assumed that the cracked plate with the system of stringers is in a generalized plane stress state. The boundary-value problem is reduced to a system of singular integral equations, which is solved by the method of mechanical quadratures. Numerical results are presented for a reinforced plate with a rectilinear or curvilinear crack (along a parabolic arc).

Stringer system and alteration zones underlying the Hellyer volcanogenic massive sulfide deposit, Tasmania, Australia

Underlying the 17 million metric ton, high-grade, polymetallic Hellyer volcanic-hosted massive sulfide deposit is a well-developed and preserved alteration zone and stringer vein system. Mineralogical zoning exists within a footwall alteration pipe, with a central siliceous core giving way to zones of chlorite, chlorite-carbonate, sericite, and finally sericite-quartz (stringer envelope zone) on the margins. Pervasive alteration started with development of sericite-quartz that was subsequently overprinted by sericite, then chlorite, and finally quartz as hydrothermal activity intensified in the center of the alteration zone.Compared to unaltered footwall andesite, the siliceous core is enriched in SiO 2 , K 2 O, MnO, Y, Fe 2 O 3 , and S but depleted in Na 2 O and CaO. Additions of MgO, MnO, Fe 2 O 3 , S, and Y and losses of Na 2 O and CaO occur in the chlorite zone. In the sericite zone SiO 2 , MgO, K 2 O, MnO, Fe 2 O 3 , and S are gained but Na 2 O and CaO are depleted. Only Na 2 O is depleted whereas MnO, K 2 O, P 2 O 5 , S, Y, and SiO 2 are gained in the stringer envelope zone. The alteration index (AI) value [(K 2 O + MgO)/(K 2 O + Na 2 O + CaO + MgO)] X 100 becomes progressively larger, with increasing intensity of alteration, from the unaltered andesite (AI = 36) to the siliceous core (AI = 91).The Hellyer stringer zone contains distinct thick synmineralization veins that represent the channelways for hydrothermal solutions passing up through the alteration zone to the sea floor. Eight stages of veining are distinguished in the stringer zone: one stage ofpremineralization (stage 1), three stages of synmineralization (stages 2A, 2B, 2C), and four stages of postmineralization veining (stages 3-6). Synmineralization veining closely follows the formation of the pervasive footwall alteration and is most intense in the siliceous core.Metal zoning indicates the presence, and alignment, of several feeder systems underlying the deposit. The main feeder is located under the middle of the deposit with secondary feeder systems underlying the southern and northern portions of the deposit. Iron and copper are concentrated in the cores of the feeders with zinc and lead, silver, gold and arsenic, and barium becoming increasingly dispersed away from the centers of hydrothermal activity.Distinct delta 34 S variations exist between vein stages within the stringer and stringer envelope zones. The main base metal-rich stage 2B veins display lower sulfur isotope values (3.8-8.9ppm, mean = 6.9ppm) than the earlier stage 2A veins (5.7-11.1ppm, mean = 9.9ppm). The delta 34 S values for stage 2A veins in the stringer envelope zone are significantly higher delta 34 S values (11.9-40.7ppm, mean = 25.0ppm) than those from the stringer zone. Variations in delta 34 S can be explained by a model where the hydrothermal fluid initially consists of totally to partially reduced seawater sulfate that evolves into a fluid dominated by igneous sulfur (ore-forming fluid) as the convection system intensified and penetrated deeper into the footwall. At the end of the hydrothermal system's life sulfate becomes more abundant in the fluid, and eventually dominant.

Development of Economical Low‐Volume Road Bridges

Low‐volume road bridges are currently designed according to the same specifications as urban highway bridges. Thus, many of the low‐volume bridge designs are overly conservative and uneconomical. This paper addresses this issue and proposes modifications of the existing specifications in the area of fatigue, deflection, allowable stress, composite action of timber decks, bridge width, lane loading, and the use of guardrails. All of the systems selected were combinations of prefabricated components. Jointless bridges received very high rankings and are strongly recommended for the 60‐ft and 100‐ft span ranges. A precast voided slab system and a timber deck and steel stringer system received the highest ranking on the 30‐ft span range. This study proposed a method of selecting the type of bridge system to be built in a particular area and a priority scheme to select which bridges must be replaced first. The scheme models the Federal Highway Administration (FHWA) sufficiency ranking with some of the ranking ...