Transverse Bars Research Articles

Axial compression performance of steel/bamboo composite column

Abstract A new type of thin-walled steel tube/bamboo plywood hollow composite column with binding bars (SBCCB) that used transverse binding bars to reinforce the composite column was developed. The compression performance of 4 specimens with larger slenderness ratio was tested to examine the failure mode of the SBCCBs. The results indicated that the compression failure modes are mainly crushing failure of the bamboo plywood material, partial debonding failure of the adhesion interface and buckling instability failure; the ultimate bearing capacity of the specimens is not only related to net cross-sectional area and slenderness ratio, but also greatly affected due to binding bars. Transverse binding bars can ensure the integrity of the composite column, effectively reduce the debonding failure of the adhesion interface and significantly improve the load-bearing capacity of the SBCCBs.

Redescription of Cichlidogyrus philander (Monogenea, Ancyrocephalidae) using scanning electron microscopy (SEM) and molecular analysis.

The sclerotized structures of monogeneans have traditionally been studied by light microscopy and different staining techniques. Recently, enzymatic digestion followed by scanning electron microscopy (SEM) has enabled the examination of structural details not visible with light microscopy. In order to obtain better, and more accurate, morphological information on sclerotized structures not affected by mounting medium or cover slip pressure, the sclerites of Cichlidogyrus philander Douëllou, 1993 (Monogenea, Ancyrocephalidae), collected from Pseudocrenilabrus philander (Weber, 1897), were redescribed using SEM. Parasites were collected from Padda Dam, Gauteng, South Africa and soft tissue was digested to release the sclerotized structures. The digested tissue also provided sufficient genetic material for molecular characterization of this species. Cichlidogyrus philander is characterised by a penis with a sharp, curved, lateral termination, an accessory piece with a hook-like extremity that may appear forked terminally, and lack of a visible vagina. The transverse bars have concave and convex surfaces with ribs on the concave surface. The dorsal bar bears fenestrations at the base of the auricles and the ventral and dorsal gripi are dissimilar. Furthermore, the large first pair of uncinuli shows lateral wings on the left side of the base. On top of this wing, a ball-like structure with a small fenestration is visible. Genetic characters derived from the 28S rDNA, the COI mitochondrial DNA and ITS1 rDNA regions distinguish C. philander from all other Cichlidogyrus sequenced species.

Beach Morphodynamics of an Atlantic Coast Embayment: Runkerry Strand, County Antrim

Runkerry Strand is exposed to high energy Atlantic wind and wave processes. Rhythmic topography found on the beach and in the nearshore zone includes beach cusps, rip current channels, longshore rip feeder channels, rip current embayments (giant cusps), transverse and crescentic bars. Changes in beach/nearshore zone morphology are cyclic and although no link with incident wave power was demonstrated, it is suggested that the Australian beach state model is applicable. Sand is moved seawards by rip currents which scour the sea bed. exposing an underlying gravel frame, and returns landwards on migrating crescentic bars which become welded to the upper beach.

Bond behaviour of straight, hooked, U‐shaped and headed bars in cracked concrete

AbstractMost classic investigations on bonding properties in reinforced concrete have been performed on the basis of pull‐out tests, where a reinforcement bar is pulled out from an uncracked concrete cylinder, prism or cube. In these tests, the bond is governed by the concrete strength and bar surface properties of the reinforcement (bond index, rib geometry) or by the splitting strength of the concrete (concrete cover). In the latter case, bond failure occurs due to uncontrolled cracking of the concrete specimen. In contrast to these fundamental tests, bond in many structural members is activated within already cracked concrete. This is particularly relevant for the reinforcement in beams and slabs (both for flexural and transverse reinforcement), as the reinforcing bars might be located at planes where flexural cracks develop. The opening of these cracks along the reinforcement is nevertheless not uncontrolled (as opposed to splitting failures), but it is governed by the bending deformations. The bond properties and strength of the reinforcement in actual members are therefore influenced by the opening of these cracks and are potentially different from those observed in classic pull‐out tests.The present paper aims to address this topic by presenting the results of an experimental investigation with 89 monotonic pull‐out tests performed on cracked ties. The opening of the cracks was controlled while transverse bars – located in the plane of these cracks – were pulled out from the specimens. The tests were performed for crack openings ranging from 0.2 mm to 2.0 mm in order to cover conditions both at the serviceability and ultimate limit states. The results show a very significant influence of in‐plane cracking on both strength and bond‐slip stiffness, with decreasing mechanical performance for increasing crack openings. The performance of different actual anchorage types (straight, hooked, U‐shaped and headed bars) – generally characterized through force‐slip relationships – is finally analytically investigated and compared to the test results.

New structural joint by rebar looping applied to staged box girder bridge construction. Static tests

AbstractThe paper describes the design, development and experimental checking of a modified type of structural joint with limited length between concrete segments cast in‐situ. The design concept is based on the developed length of an anchorage hook stiffened by transverse reinforcement bars and is particularly suited for the case of in‐situ construction of staged box girder bridges, with the intention of possibly using lighter scaffolding.The studies concentrated on the strength, stiffness and serviceability of the proposed joint are presented. The research work comprises the bending behaviour of reinforced concrete slabs with loop joints with regard to the diameter of the loop bar, loop joint width and ultimate and fatigue load. The results are compared to the behaviour of reinforced concrete slabs without joints. A total of 16 slabs were tested with static and fatigue loading tests. The present paper evaluates the flexural behaviour in static loading tests. The results of fatigue tests have also shown excellent performance.In the static tests, crack widths and cracking pattern were observed at service load levels, and the ultimate behaviour was evaluated by means of tests to failure.From the test results, the service performance of the loop joints was confirmed to be similar to slabs without joints. The static loading tests confirm the good performance and effectiveness of this loop joint type under static loading. Details of the loop joint design criteria are also proposed.

Contribution of Transverse Tie Bars to Load Transfer in Adjacent Prestressed Box-Girder Bridges with Partial Depth Shear Key

AbstractAdjacent box-girder bridges have become a popular choice as they can be constructed quickly, easily, and economically. In spite of their good performance during many years of service, one major problem has been recurrent longitudinal cracking of the grout material in the shear key. A combination of shear keys and transverse posttensioning (TPT) ties in such kind of bridges is typically used to connect the bridge girders together so that they would behave as a single integrated unit. However, information regarding the contribution of the TPT tie bars on load transfer between adjacent box girders is limited. In this study, a single-span precast prestressed concrete adjacent box-girder bridge was instrumented and monitored to study the effect of TPT tie bars on load transfer mechanism and overall bridge behavior under static and dynamic truck loads. Two sets of instruments were installed in the girders and tie bars during and after the construction of the bridge. A good correlation was achieved betwe...

Thismia claviformis (Thismiaceae), a new species from the Thai-Malay Peninsula

Thismia claviformis Chantanaorr. & J. Wai, is described and illustrated as a new species from the Thai-Malay Peninsula. The new species is characterized by 1) vermiform underground parts, 2) equal perianth lobes with slender claviform appendages, 3) a perianth tube without transverse bars inside, and 4) the apex of stamen bearing two triangular lobes. A taxonomic description, illustrations of the new species and a comparison with the related species are presented.

Experimental investigation into the development length of carbon-fiber-reinforced polymer grids in concrete

Carbon-fiber-reinforced polymer grids have received much attention lately because of many advantages. The force transfer behavior and development length of carbon-fiber-reinforced polymer grid reinforcement were evaluated using a pull-out test method. A total of 18 pull-out specimens of carbon-fiber-reinforced polymer grid reinforcement were tested under monotonic static loading, and the investigated parameters included the concrete compressive strength, the number of embedded transverse bars, with or without transverse bars, and the number of adjacent longitudinal bars. The slips between the reinforcing carbon-fiber-reinforced polymer grids and the concrete were measured at both the free end and the loaded end during the whole loading process. The test results indicated that first, the concrete compressive strength and the adjacent longitudinal bars had little influence on the force transfer behavior, second, the wedge action of the transverse bars was very important for transferring force; thus, increase in number of embedded transverse bars increased the force transfer stiffness and reduced the slippage. In the case of tested carbon-fiber-reinforced polymer grids, three embedded transverse bars equal to embedment length of 150 mm were sufficient to develop full tensile strength. Based on this experimental investigation, the preliminary design principles were also discussed.

속채움 콘크리트와 철근으로 보강된 대구경 합성 PHC말뚝의 휨성능 평가

최근 구조물의 대형화에 따른 큰 지지력의 말뚝에 대한 수요가 증가하는 추세이다. 이에 따라 기성 PHC말뚝의 경우에도 700~1,200 mm 범위의 대구경 말뚝에 대한 활용이 증가하고 있고 최근 국내 현장에 적용되고 있다. 이 연구에서는 대구경 PHC말뚝의 휨성능을 향상시키기 위해 철근과 콘크리트로 보강하여 합성 PHC말뚝을 제작하였다. 휨강도 평가는 4등분점 제하실험을 통해 변위제어 방법으로 수행되었다. 휨실험을 통해 LICPT 실험체 횡방향 철근의 변형률 분포를 분석한 결과 횡방향 철근의 배근은 전단균열의 진전과 균열폭 제어에 효과적인 것으로 나타났고, 복부전단균열 발생을 억제할 수 있었다. LICPT 실험체는 LICP 실험체 보다 휨강도가 약 1.08배, 중앙부 변위가 약 1.19배 증가하였고, 횡방향 철근의 배근은 말뚝의 연성적인 휨거동 확보에 유리한 것으로 나타났다. 말뚝 제작시 사용되는 각각의 재료가 휨강도에 기여하는 수준을 층상화 단면 해석으로 계산된 축강도-휨모멘트 상관도를 통해 평가하였다. 기성 PHC말뚝과 LICP 실험체의 실제 휨강도를 1.13배, 1.16배의 안전율로 예측할 수 있었다. A demand of high bearing capacity of piles to resist heavy static loads has been increased. For this reason, the utilization of large diameter PHC piles including a range from 700 mm to 1,200 mm have been increased and applied to the construction sites in Korea recently. In this study, in order to increase the flexural strength capacity of the PHC pile, the large diameter composite PHC pile reinforced by in-filled concrete and reinforcement was developed and manufactured. All the specimens were tested under four-point bending setup and displacement control. From the strain behavior of transverse bar, it was found that the presence of transverse bar was effective against crack propagation and controlling crack width as well as prevented the web shear cracks. The flexural strength and mid-span deflection of LICPT specimens were increased by a maximum of 1.08 times and 1.19 times compared to the LICP specimens. This results indicated that the installed transverse bar is in an advantageous ductility performance of the PHC piles. A conventional layered sectional analysis for the pile specimens was performed to investigate the flexural strength according to the each used material. The calculated bending moment of conventional PHC pile and composite PHC pile, which was determined by P-M interaction curve, showed a safety factor 1.13 and 1.16 compared to the test results.

Seismic performance of square, thin-walled steel tube/bamboo plywood composite hollow columns with binding bars

A thin-walled steel tube/bamboo plywood composite hollow column with binding bars (SBCCB) was developed using transverse binding bars to reinforce a thin-walled steel tube and bamboo plywood composite hollow column. Low reversed cyclic loading tests were performed on 9 SBCCB specimens to observe the damage process and morphology in the SBCCBs. The effects of the slenderness ratio, the net cross-sectional area of the bamboo plywood, the assembly patterns of the cross sections, and the binding bars on the stress and seismic performance were investigated. The results show that the main failure modes of the SBCCBs were cracking of different adhesion interfaces at the base of the column and fracturing of the bamboo plywood. The cross-sectional assembly pattern has a significant effect on the failure modes; increasing the cross-sectional area and the slenderness ratio of the composite column will dramatically improve the seismic performance of the SBCCBs. SBCCBs have excellent elastic deformation and seismic energy consumption characteristics. The binding bars ensure the integrity of the specimen and inhibit the failure of the adhesion interface at the base of the column. Finally, based on the measurement of the axial pressure and the stress-strain curve within elastic range of the composite columns, a simplified mechanical model and a calculation method for bearing capacity was formulated. The calculation values of bearing capacity agree well with the experimental ones, and calculation method can be used to provide guidance for engineering applications of a SBCCB.

A new long-snouted species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin.

A new species of Corydoras is described from the rio Aripuanã, rio Madeira basin, Mato Grosso State, Brazil. The new species can be distinguished from its congeners by the presence of the following features: long mesethmoid, with anterior tip well developed, conspicuously larger than 50% of bone length; posterior margin of dorsal-fin spine with serrations directed towards tip of spine; one to two longitudinal black stripes on flanks; absence of a black blotch across the eyes (mask); absence of a large black blotch on dorsal fin; and transversal black bars on caudal fin. Comments on endemism in interfluvial region between Madeira and Tapajós rivers are briefly discussed.

Seismic Performance of Full-Scale FRP Retrofitted Substandard RC Columns Loaded in the Weak Direction

FRP confinement of sub-standard columns with low quality concrete, light transverse reinforcement and improper reinforcement detailing is widely accepted as an efficient retrofitting strategy. This paper introduces an improved method using carbon fiber reinforced polymers (CFRP) and external steel ties for seismic retrofitting of full-scale rectangular reinforced concrete columns loaded in their weak directions. Three cantilever columns with a cross-sectional aspect ratio of two (600 mm x 300 mm) are tested under constant axial load and reversed cyclic lateral loads. The columns are representative of existing substandard members with characteristics such as low concrete quality, low transverse reinforcement ratio, plain bars and high axial load level. The test results indicate that columns retrofitted with FRP jacketing and external steel ties significantly benefit from the applied retrofit scheme particularly in terms of ductility and energy dissipation. Additionally, the experimental results are compared with the performance predictions of seismic assessment and design documents.

Closure to “Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars” by C. Di Stefano and V. Ferro

Closure to “Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars” by C. Di Stefano and V. Ferro

Discussion of “Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars” by C. Di Stefano, and V. Ferro

Discussion of “Stage–Discharge Relationship for an Upstream Inclined Grid with Transversal Bars” by C. Di Stefano, and V. Ferro

Structural behavior of partially encased composite columns under axial loads

This paper presents the results of experimental and numerical model analyses on partially encased composite columns under concentric loads. The main objective of this study is to evaluate the influence of replacing the conventional longitudinal and transverse steel bars by welded wire mesh on the structural behavior of these members under concentric loads. To achieve these goals experimental tests on four specimens of partially encased composite columns submitted to axial loading were performed and the results were promising in terms of replacing the traditional reinforcement by steel meshes. In addition, a numerical FE model was developed using the software DIANA® with FX+. The experimental results were used to validate the numerical model. Satisfactory agreement between experimental and numerical results was observed in both capacity and deformability of the composite columns. Despite of the simplifying assumptions of perfect bond between steel and concrete, the numerical model adequately represented the columns behavior. A finite element parametric study was performed and parameters including thickness of the steel profile and the concrete and steel strengths were evaluated. The parametrical study results found no significant changes in the partially encased columns behavior due to variations of the steel profile thickness or yield strength. However, significant changes in the post peak behavior were observed when using high strength concrete and these results suggest a change in the failure mode.

Irregular stone masonries: Analysis and strengthening with glass fibre reinforced composites

Abstract Two masonry types with irregular texture are analysed to evaluate mechanical properties, sources of vulnerability and to design proper strengthening interventions. Direct surveying, laboratory and in situ tests were performed to evaluate morphological characteristics and mechanical properties. Experimental values were compared with results obtained from analytical and FEM homogenizations, which exploited automated image segmentation process to determine volume fractions and description of the Reference Volume Element. Strips of Glass Fabric-Reinforced Cementitious Matrix and transversal bars were considered and tested as strengthening solutions to overcome irregular masonries limits derived from multi-leaf structure highlighting levels of capacity improvement.

A new species of nurse-frog (Aromobatidae, Allobates) from the Madeira River basin with a small geographic range.

I describe the seventh species of nurse-frog (Allobates) from the Madeira River basin in Brazilian Amazonia. The new species is distinguished from similar congeneric species by its small body size (snout-to-vent length ranging between 14.0-14.7 mm in adult males and between 14.7-14.9 mm in adult females), by the absence of dark brown regular shapes (e.g. hourglass, "X" or polygon-like marks) on the dorsum, by the absence of transverse dark bars on the dorsal surface of the thigh, and by the light gray to white ventral surfaces, light to dark gray only on throat in live male and female specimens. Males have a distinctive advertisement call characterized by the emission of long (7-11 s) trills of short notes (0.04 s in average) with dominant frequency at 5.9-6.3 kHz and emission rate ranging between 6.7-8.7 notes/s. DNA barcode analyses based on a fragment of the 16S rDNA mitochondrial gene provides additional support to the recognition of the new taxon, which is probably distributed on the east riverbank of the Madeira River, in the interfluve between the Aripuanã and Ji-Paraná rivers.

Axial Load and Cyclic Lateral Load Tests for Composite Columns with Steel Angles

AbstractTo enhance the structural capacity and constructability of composite columns, a prefabricated steel-reinforced concrete (PSRC) column was developed. By using the prefabricated steel cage, field rebar work is unnecessary, and the self-erectable steel cage can provide sufficient strength and rigidity to support the construction loads of beams and slabs. In the present study, various steel angle ratios, transverse bar spacings, and prefabrication details were considered for better structural capacity and constructability. To investigate the performance of the proposed method, axial loading tests and cyclic lateral loading tests were performed. In the axial loading test, the structural performance of the PSRC columns was comparable to, or even better than, that of the conventional composite column using the wide flange steel section, when early spalling of the cover concrete was restrained by closely spaced hoops. Under cyclic lateral loading, on the other hand, the PSRC columns were more susceptible ...

Revisionary study of the armored catfish Corydoras paleatus (Jenyns, 1842) (Siluriformes: Callichthyidae) over 180 years after its discovery by Darwin, with description of a new species

ABSTRACT The taxon known as Corydoras paleatus carries one of the most complex taxonomic histories among Corydoradinae catfishes. A comprehensive review of specimens attributed to that species from several localities was carried out, allowing the clear recognition of C. paleatus and also of a new species previously misidentified as C. paleatus , described herein. Corydoras paleatus can be distinguished from its congeners by presenting the following unique combination of features: perpendicularly directed serrations along entire posterior margin of the pectoral spine; three large black blotches along midline of flank; hyaline or black pectoral fin; and transversal black bars on caudal-fin lobes. Corydoras paleatus is known from the lower rio Paraná basin, coastal rivers from Southern Brazil and Uruguay and rio Uruguai basin. The new species can be distinguished from its congeners by having the following unique combination of features: three large black blotches along midline of flank; three nasal pores; mesethmoid short; infraorbital 2 not in contact with compound pterotic; striated black spots from the snout tip to nuchal plate region; markedly rounded snout; and anterior portion of dorsal fin spotted. The new species is known from the upper rio Uruguai basin, from the rivers Canoas, do Peixe and Pelotas.

Two new species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin, Brazil

Abstract Two new species of Corydoras are described from the rio Madeira basin, Brazil. The intermediate long-snouted new species can be distinguished from its congeners by presenting the following combination of features: posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the spine; presence of two longitudinal black stripes on flanks; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; absence of a conspicuous black marbled coloration pattern on head; black spots on caudal fin, some spots arranged, forming transversal bars; and brownish dorsal-fin spine. The short-snouted new speciescan be distinguished from its congeners by the following combination of features: short mesethmoid; posterior laminar expansion of infraorbital 2 very reduced, not in contact with compound pterotic; two or three longitudinal black stripes on flanks; absence of an oblique or vertical black blotch across the eye; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; and ventral surface of trunk naked or covered by sparse platelets.