Evaluation of the Crack Model of V Type Longitudinal Ribs on Orthotropic Deck Using Finite Element Analysis

The long span orthotropic bridge decks applied around the world are used with open or closed cross-sectional longitudinal ribs placed below the steel deck to increase the strength of the deck. Fatigue cracks are developed in the longitudinal ribs due to traffic loadings. In this study, v type of longitudinal rib cross-sections are modelled and the stresses for the rib are evaluated under tire load loading using finite element analysis. Longitudinal ribs are used for long span steel bridges. The aim of this study is to compare the fatigue crack path of the longitudinal rib on a real bridge with the stress pattern in the finite element model.

Composition of the genus Connexochiton Kaas, 1979 (Mollusca: Polyplacophora: Ischnochitonidae)

The species composition of the genus Connexochiton is revised. So far, six Recent species of the genus Connexochiton have been known: C. platynomenus, C. kaasi, C. crassus, C. bromleyi, C. moreirai and C. discernibilis After the present revision, the genus consists of Connexochiton platynomenus, C. kaasi, C. crassus, as well as three new species, C. costatus n. sp. from the Philippines, C. kermadeci n. sp. from New Zealand and C. solomonicus n. sp. from the Solomon Islands. Connexochiton discernibilis was assigned to the ischnochitonid genus Stenosemus (now Stenosemus discernibilis). Connexochiton bromleyi and C. moreirai are transferred back to the genus Ischnochiton. Principle features of the genus Connexochiton include: a distinctive shape of the valves with the hind edge of the intermediate valves noticeably turned down, which makes the lateral areas narrow and appearing strongly raised; tegmentum delicately sculptured by quincuncially arranged triangular granules that form an alveolate pattern; each granule has 9 to 11 aesthete pores; apophyses are connected medially by a short jugal plate, dorsal scales of the girdle are strongly bent, with short longitudinal ribs or spherules or both; head of the major lateral teeth of radula is unicuspid and sickle-shaped. An identification key for the species of the genus Connexochiton is provided.

Transformative nototchaetae: larval development and metamorphosis in Chrysopetalum spp. (Chrysopetalinae: Chrysopetalidae: Annelida)

The morphology of an early nectochaete larva belonging to Chrysopetalum sp. is aligned with that of a planktotrophic larva at a crucial stage of benthic settlement: an entire provisional spinose notochaetal scleritome, large episphere with prostomial nascent sensory structures and larval podia and cirri of the anterior two segments in transition. Morphological sequences of post-larvae and juveniles, common to a number of Chrysopetalum species, indicate that long, slender, provisional, camerate notochaetal spines are replaced during metamorphosis and growth with an entire adult, camerate notochaetal scleritome consisting of broad paleae with internal, longitudinal ribs. The Chrysopetalum sp. six segment larva supports achaetous notopodia I and chaetous notopodia II, each with a pair of dorsal cirri, ie. 4 cirri in total; segment II has acirrose neuropodia. Individuals of post-larvae and juvenile Chrysopetalum species, 8–15 segments, possess a total of 6 cirri on segments I and II: segment I with a pair of tentacular dorsal cirri and the formation of a pair of tentacular ventral cirri, and segment II comprising a pair of dorsal cirri, spinous notochaetae and acirrose neuropodia. During metamorphosis the acirrous neuropodia of segment II are reabsorbed and replaced in stages with a pair of ventral tentacular cirri until the adult state is achieved: achaetous segment 1 with two pairs of tentacular cirri and segment II similar, ie. total of 8 cirri. The cirri arrangement of segments I and II before final metamorphosis in post-larval stages of Chrysopetalum species is, interestingly, that described for adults in the majority of other Chrysopetalinae taxa. Ontogenetic developmental processes of formation and loss of acirrose neuropodia and replacement of spinose larval notochaetae with adult paleae observed in Chrysopetalum species are compared with species of other taxa of the Chrysopetalinae.

VIBRATIONS REINFORCED BY LONGITUDINAL RIBS OF AN INHOMOGENEOUS ORTHOTROPIC CYLINDRICAL PANEL CONTACTING WITH A VISCOUS-ELASTIC MEDIUM

Vibrations of an orthotropic cylindrical panel, non-uniform in thickness, supported by longitudinal ribs, lying on a linearly viscoelastic foundation, were investigated. The Hamilton – Ostrogradsky variational principle was used to find the vibration frequencies of the panel. A frequency equation is constructed, its roots are found, and the influence of physical and geometric parameters characterizing the system is studied.

Frustulia tunariensis sp. nov. (Bacillariophyceae) from the Andes of Bolivia, South America

Frustulia tunariensis sp. nov. is originated from a high-altitude peatland in the Tunari Cordillera, a branch of the Andean range in Bolivia. The new taxon is distinguished by the thick longitudinal ribs, the globose polar nodule with faint helictoglossa that does not produce an apical extension, and by the high areola and stria density, not found in any of the morphologically closely related taxa. Features of the folded valvocopula, such as the presence of a siliceous membrane as pars interior, and poroids present in the tube-like portion opening as slits to the valve interior and as a single row of poroids to the exterior, are also unique characters in the new taxon. Based on a literature review, a comparison of the newly proposed species with morphologically similar taxa was made. Also, published information shows the potential of girdle bands to distinguish groups of species and species themselves within Frustulia. Likewise, remarks on the ecological and distribution aspects of Frustulia in the Bolivian Altiplano are included, focusing on taxonomic quality, geographic coverage and sampling, and potential to represent the genus in the high Bolivian Andean plateau.