Transverse Bars Research Articles

The description of the first rock-dwelling species of butterfly lizard Leiolepis Cuvier, 1829 (Squamata, Agamidae) from the Khorat Plateau in northeastern Thailand.

A new species of rock-dwelling Leiolepis is described from the Khorat Plateau in northeastern Thailand. Leiolepisglaurung sp. nov. can be differentiated from all other sexual species of Leiolepis by a combination of having a black gular region with a wide medial yellow stripe, a yellow ventrum with black mottling, bright red to orange subcaudal coloration, having reduced to no expandable flanks, and having only one black transverse bar on the flanks. This is the first rocky habitat-adapted Leiolepis. Leiolepisglaurung sp. nov. demonstrates numerous ecological adaptations to survive in these rocky habitats. Leiolepis are known for their expandable flanks with bright display colors, however Leiolepisglaurung sp. nov. has reduced or no ability to expand its flanks. We hypothesize this is an adaptation to reduce their body diameter to better fit into smaller rocky burrows unlike the larger and deeper burrows constructed in looser soils by other Leiolepis species. This discovery increases the number of Leiolepis species in Thailand to six, and worldwide to 11.

Limit analysis and design recommendations for fiber‐reinforced concrete subjected to shear

AbstractIt is widely recognized in both research and practice that fibers have great potential to partially, or completely, substitute conventional transverse reinforcement in webs of girders subjected to moderate shear forces. However, despite extensive research in recent years, there is still no consensus in the research community on the mechanically sound modeling of the shear strength of fiber‐reinforced concrete (FRC). Accordingly, current code provisions for the design of FRC to resist shear rely on (semi‐)empirical approaches and are thus justifiably restrictive. This article addresses this knowledge gap by proposing the application of the theory of plasticity to the design of FRC webs. Limit analysis methods for conventionally reinforced concrete are extended to FRC by incorporating the residual crack‐bridging stress offered by the fibers in a consistent manner. This stress, as well as the limits of applicability of the theory of plasticity, are derived through a sensitivity analysis using the recently developed Cracked Membrane Model for FRC considering fixed, interlocking cracks. Based on these investigations, a straightforward and efficient mechanically based shear design model suitable for the design of FRC webs with and without conventional transverse bar reinforcement is proposed. The model is validated against a large database of panel and beam experiments, providing valuable insights into its reliability.

An Investigation into the Variables Influencing the Structural Bamboo Architecture Using Filled Concrete and Cement Mortar

Bamboo, as a green building material, plays a vital role in construction. Bamboo has good properties and appearance, making it highly attractive for building structures and designs. Since the compressive capacity of bamboo is considerably lower than its tensile capacity, with the ratio typically ranging between 300% to 900%, this limits its application dimensions in construction. Therefore, filling the original bamboo structural members with specific materials or applying different connection methods can not only maintain the appearance of the bamboo structure but also improve its compressive capacity and overall durability, thus expanding the application range of bamboo structural members and enhancing the performance of the architectural design process. Two hollow bamboo specimens were among the eight BFC specimens tested for this paper. Key components such as transverse stiffeners, steel bars, filler materials, and bamboo nodes were examined for their influence on the specimens’ ductility, peak strain, ultimate bearing capacity, and failure mechanisms. The test results showed that the ratio of the ultimate bearing capacity of BFC specimens to hollow bamboo samples could reach up to 538%, while the peak strain differences were minimal. A non-linear finite element model was developed and its accuracy confirmed based on the test results. This work proposes a new approach to determine the final axial compressive capacity of BFC columns by creating an elastic model of transversely isotropic cylinders. As a result, the primary goal of this study is to establish a foundation for more scientific building design techniques and procedures by examining the axial compression mechanics of structural bamboo filled with cement and concrete (BFC) and how it influences building design.

The Morphodynamics of a Double-Crescent Bar System under a Mediterranean Wave Climate: Leucate Beach

The morphodynamics of the Leucate double-crescent bar system was studied over twenty years using bathymetric data supplemented by satellite images and video monitoring. Eleven different bar typologies were identified, mostly based on existing beach state classifications (Low-Tide Terrace, Transverse Bar and Rip, Rhythmic Bar and Beach), also including new heterogeneous typologies (TBR/LTT, RBB HP/RBB, TBR/RBB). The inner bar shows greater variability, with 10 different typologies observed, while the outer bar shows only three different typologies. Summer low-energy periods are dominated by TBR/LTT and TBR typologies, while RBB, although common throughout the year, dominates winter periods along with disrupted bar configurations. The return to less energetic periods in spring is associated with the establishment of heterogeneous typologies. The outer bar has a fairly stable position, although breaches at the embayments and slight movements of its horns can occur following particularly energetic episodes. The inner bar, on the other hand, is much more dynamic, with more common breaches at the embayments and significant cross-shore movement of the horns. Seasonal changes in bar typology do not lead to bar renewal through destruction/reconstruction. Overall, the morphological and typological characteristics of the bar system described here seem somewhat unique compared to the existing literature.

Investigation of Flexural Strength of African Copalwood (Daniella Oliveri) as Reinforcement in Concrete Slab

This study investigates the potential of African Copalwood as a reinforcing material in concrete slabs. The timber rods were randomly selected from the timber market because there is always variation in timber properties with position in stem, location and soil condition. Various test specimen were prepared according to the Code of practices BS EN 408:2003 using structural size specimens. Thirty (30) slabs of size 75 mm x 300 mm x 700 mm were cast in five sets (1 to 4%) for Timber-reinforced concrete slab (TRCS) and Steel-reinforced slab (SRS) with a mix ratio of 0.5:1:2:4 denoting water-cement ratio, cement, fine and coarse aggregate respectively. Longitudinal bars were varied in 1% to 4% slab cross-sectional area in different TRCS samples while the transverse bar was restricted to be 3% by standard and made constant in all the slab samples specimen. A 10 mm diameter steel bar is used as reinforcement in the SRS. Findings revealed that the mean failure stress for Tensile strength parallel to grain was 41.80 N/mm2, Bending strength parallel to grain was 37.05 N/mm2, Compression parallel to grain was 13.48 N/mm2, Compression perpendicular to grain was 8.88 N/mm2, Local Modulus of Elasticity (MOE) was 3800.17 N/mm2, Apparent MOE was 59.42 N/mm2. Also, with regards to TRCS, the flexural strength test at 28 days for 1% to 4% reinforcement in concrete slabs is 3.61, 5.29, 5.49 and 7.22 N/mm2 respectively. The SRS has a flexural strength of 11.54 N/mm2 at 87.5% composition in slabs. These findings indicate enhancement in the strength properties of the concrete slabs with the incorporation of the African Copalwood reinforcement.

Flexible composite structure with customizable in-plane Poisson’s ratio under large deformation

Regulating the inherent Poisson's ratio of soft elastic materials under large deformation is important for their application in emerging fields, such as morphing structures and stretchable electronics. In this study, we selected a composite in which an auxetic honeycomb was embedded in a soft material to regulate the in-plane Poisson's ratio. Based on a cantilever beam model, a theoretical model was established to guide the design optimization of composite structures. The macroscopic constitutive relation and in-plane Poisson's ratio of the composite structures with different configurations were predicted by the theoretical model, which were consistent with the finite element analysis results. In the 30% strain range, the slope of the Poisson's ratio–strain curve decreases with an increase in the length of the inclined bar, and the in-plane Poisson's ratio increases with an increase in the angle between the transverse bar and the inclined bar. In addition, we propose an optimization design method with the in-plane Poisson's ratio as the objective function and then optimize and fabricate a skin structure with an in-plane Poisson's ratio of approximately zero for the morphing wings. The achievements of this study provide theoretical guidance for regulating the in-plane Poisson's ratio of thin flexible layers.

A Comparative Study of the Structural Behavior of Concrete Beams Reinforced with Different Configurations of GFRP and Steel Bars

This study examined experimentally and numerically the performance of five concrete beams reinforced with longitudinal and transverse bars made of Glass Fiber Reinforced Polymer (GFRP) or steel. All beams had the same dimensions of 2700 mm in length, 180 mm in width, and 260 mm in depth. The beams were classified into two groups with different variables and compared with a reference beam reinforced with longitudinal and transverse steel bars. The first group consisted of two beams with longitudinal GFRP bars and no stirrups, varying the main reinforcement ratio. The second group comprised two beams with longitudinal GFRP bars and transverse GFRP or steel stirrups, varying the stirrup type. The results indicated that the beams with GFRP bars improved their flexural strength for different ratios but had limited shear resistance when using GFRP stirrups because increased deflection causes the number and width of cracks to grow, reducing the shear strength. All the tested beams exhibited linear elastic behavior until failure, with GFRP being more brittle than steel due to no yield point or plastic behavior in GFRP. The numerical simulation of the five beams using ABAQUS software showed good agreement with the experimental data obtained in the laboratory.

Design and Performance Study of a Six-Leg Lattice Tower for Wind Turbines

A new type of spherical node was used to design a laboratory-scale prototype of a six-leg lattice of steel tubes and concrete for application as a wind turbine tower. Repeated load tests were performed on the prototype tower for several weeks to evaluate its load-carrying capacity, deformation, energy consumption, stress distribution based on damage patterns, hysteresis curves, skeleton curves, strength, and stiffness degradation curves. The findings indicated that the prototype tower underwent thread damage to the high-strength bolts of the inclined web and weld damage between the inclined web and sealing plate. Although the stress differences between different measurement points were significant, the stress values were small at most of the measurement points. The maximum equivalent stress value was 294 MPa, which appeared in the middle layer of the BC surface. The P-Δ hysteresis curve had an inverse “S”-shape, and the bearing capacity was high. The maximum energy dissipation appeared in the 1.75 Δy loading stage. The peak load of the specimen can reach 376.2 kN, and the corresponding peak displacement is 37 mm. However, the average ductility coefficient was only 2.33, indicating little plastic deformation. The maximum strain of the tower column foot is 1800 με, and the force of the inclined web member in the middle layer is the largest. The strain of the transverse web bar increased significantly after the tower yielded, which contributed to maintaining the integrity of the structure.

Refinement in the understanding of confinement of concrete

The compressive axial load-deformation curve of a reinforced concrete (RC) member reflects the contributions of the concrete in compression and tension, the longitudinal and transverse reinforcement bars in compression and bending, and the aggregate interlocking in concrete in its dilated state. Together these factors enhance the axial response of RC compared to its plain counterpart. Even though expressions proposed in the past capture the composite response of this confining effect in an empirical sense, none of them separate the said individual contributions. This study provides a mechanics-based method to obtain the axial-load deformation response of a RC member, and thereby the stress-strain curve of confined concrete, by assembling the combined effect from each contributing parameter. The governing contributions are fundamental and physically intuitive; they include contributions of unconfined concrete, transverse reinforcement, longitudinal reinforcement (including buckling), and aggregate interlocking. The stress-strain curves from the proposed method compare well with those obtained from many tests on confined concrete available in the literature, and seem to better estimate the response than two popularly used confinement expressions. Similar comparisons are made with the axial load-deformation curves. A parametric study is undertaken to capture the effects of section geometry, high-strength materials, and area ratio on the confinement of concrete. Finally, a refined understanding is presented of the estimation of strength of confined of concrete.

Mechanical performances of thin-walled high-strength concrete-filled steel tube square columns with high-strength reinforced cages under biaxial eccentric compression

In the current research that both steel tube and concrete use high-strength materials, there are few studies on the small wall thickness of steel tube exceeding the standard. In order to make full use of the mechanical properties of high-strength steel and enhance its restraint ability on concrete, this paper designs a steel cage dominated by transverse steel bars. A total of 15 square high-strength steel tube high-strength concrete medium-long column test pieces are tested and studied. The main parameters of the specimens are slenderness ratio, loading eccentricity and the form of internal steel reinforcement cage. After the loading test, according to the test results, the failure mode of the specimen is obtained and the mechanical properties of middle-long concrete-filled steel tubular columns are analyzed. The research results show that the ultra-thin high-strength steel pipe can restrain concrete well, but with the increase of eccentricity, its restraint capacity is slightly insufficient; the built-in steel cage can slow down the bulging of the specimen and help the steel pipe to further strengthen the restraint on concrete, but the steel cage as an indirect constraint cannot avoid the final bulging damage. Due to the existing formula overestimating the effect of ultra-thin steel tubes, this paper proposes a calculation formula for the axial compression of thin-walled high-strength concrete-filled steel tubes with steel cage short columns. Based on this method, the bearing capacity of medium-long columns under biaxial eccentric compression is calculated with good accuracy.

On Generalized Sehgal–Guseman-Like Contractions and Their Fixed-Point Results with Applications to Nonlinear Fractional Differential Equations and Boundary Value Problems for Homogeneous Transverse Bars

The goal of this study is to describe the class of modified Sehgal–Guseman-like contraction mappings and set up some fixed-point results in S-metric spaces. The class of generalized Sehgal–Guseman-like contraction mappings contains enhancements of Banach contractions, Kannan contractions, Chatterjee contractions, Chatterjee-type contractions, quasi-contractions, Ćirić–Reich–Rus-type contractions, Hardy–Rogers-type contractions, Reich-type contractions, interpolative Kannan contractions, interpolative Chatterjee contractions, among others, with their generalizations in S-metric spaces. We offer significant examples to substantiate the reliability of our results. This study also establishes consequential fixed-point results and applies them to nonlinear fractional differential equations and the boundary value problem for homogeneous transverse bars. At the end of the manuscript, we present an important open problem.

Post-Earthquake Serviceability Assessment Using the Convolutional Neural Networks and Deep Neural Networks

There have been studies using image processing techniques to assess damage of structure especially columns without sending individual to onsite. Convolutional neural networks (CNNs) and the entire Deep neural network (DNN) have shown state-of-art results in object detection and image classification tasks. This study proposed cascaded deep learning network for post-earthquake structural serviceability assessment. Major target deficiency components (crack, spalled area, transverse bar, and longitudinal bar) were used to determine the proposed damage states to assess serviceability of structure. Concrete surface cracks are major defect in civil structures. Structural Inspection which is done for the evaluation of rigidity and tensile strength of the building. Crack detection plays a major role in the building inspection, finding the cracks and determining the Structural health in the case of post-earthquake. The research paper is all about finding the serviceability results of the structure.

Localized Blowing for Near-Wake Flow and Vortical Structure Control in Turbulent Boundary Layers Over Periodic Two-Dimensional Roughness

Abstract Volumetric three-component flow measurements were made to investigate localized blowing (injection) as a control strategy for turbulent boundary layers over k-type two-dimensional (2D) roughness. The flow measurements were made using particle tracking velocimetry at a Reynolds number of 100,000, based on the freestream velocity and boundary layer thickness. The roughness occupied ∼13% of the boundary layer thickness and consisted of transverse square bars positioned periodically at a pitch-to-height ratio of 11. Two cases were considered: a baseline case without blowing and a case with blowing through five spanwise jets issuing from the downstream face of the 11th bar. The results highlight the effectiveness of blowing in reducing the size of the recirculation zone and turbulence past the bar. Specifically, the spanwise-averaged flow field for the blowing case shows a 40% reduction in the reattachment length and ∼25% reduction in the maximum Reynolds shear stress relative to the baseline case. Moreover, visualizations of the vortical structures past the bars for the baseline case display coherent spanwise vortices similar to those observed past isolated 2D bars and backward-facing steps; however, the spanwise vortices observed here exhibit more three-dimensionality likely due to the turbulence enhanced by upstream bars. Blowing disrupts these spanwise vortices and produces new vortical structures with a wall-normal sense of rotation, although significantly weaker than the spanwise vortices. As such, blowing results in a reduction in the spanwise-averaged spanwise vorticity characteristic of the flow over k-type 2D roughness. The disruption of the spanwise vortices and the reduction in the size of the recirculation zone are likely responsible for the reduction in the Reynolds shear stress and turbulent kinetic energy in the near wake.

Fire resistance of axially loaded semi-precast composite columns

Recently, semi-precast composite (SPC) columns have been newly developed using steel angles and internal molds. Although the manufacturability, constructability, and seismic performance of SPC columns have been proven to meet design requirements, their structural responses under fire conditions (or fire resistance) have not yet been reasonably examined. Thus, in the present study, an experimental study was conducted for five full-scale SPC columns under standard fire conditions. The test parameters included the joint detail, axial load ratio, thickness of the precast section, and slenderness ratio. The test results show that the fire resistance rating was relatively low due to the high moisture contents and relatively high axial load ratio, and concrete spalling controlled the fire resistance of the columns. The concrete spalling was affected by the concrete moisture contents and permeability, the consequent moisture clog phenomenon, the relatively high axial load ratio, and the longitudinal weak planes between the concrete cover and confined concrete created by longitudinal and transverse bars. Addressing these effects, a finite element analysis (FEA) model was developed for SPC columns using ABAQUS. Although there were some discrepancies between the test and analysis results, the FEA model gave a conservative prediction, which is reasonable for design purpose considering the complexity of nonlinear thermal-stress analysis.

Experimental study on longitudinal shear behavior of prefabricated steel-concrete composite beams with notched connections

To address the fit-up issues caused by the interference between shear connectors and extended transverse bars, a novel deck-to-girder connection detail, notched connection, is applied to steel-concrete composite bridges with partial-depth deck panel (PDDP) systems. In the novel joint detail, protruding transverse reinforcement is replaced by evenly distributed notches at the ends of precast panels, and tie bars inserted in the notches are anticipated to resist longitudinal shear stress, achieving shear connection between steel girders and precast deck slabs. Considering the discontinuity of bottom transverse reinforcement, a four-point bending test was performed to investigate the longitudinal shear behavior of composite beams incorporating notched connections. Experimental findings indicate that the configuration of transverse reinforcement critically influences the failure modes of composite specimens, which involve crushing of concrete slabs, longitudinal shear cracking and splitting. Notably, tie bars sufficiently anchored in notches function equivalently to extended bars spliced by welding, and the specifically designed U-shaped notches enhance the anchorage performance of tie bars. Transverse reinforcing bars placed in the concrete topping prove more effective in resisting longitudinal shear than those in the bottom layer, and therefore asymmetrically reinforced concrete slabs experience reduced longitudinal shear cracking and splitting. Moreover, interface shear reinforcement effectively ensures the full composite action, while concentrated point loads can induce excessive local longitudinal shear stress. The study also provides design recommendations for notched connections.

Behavior of large-scale concrete columns reinforced with high-strength and high-toughness steel bars under axial and eccentric compression

In this paper, combined with the current era background of energy saving and emission reduction, low carbon and environmental protection, the mechanical performance of new high-strength and high-toughness steel bars (HSHTSB) in concrete structural members is studied, and HSHTSB is expected to be popularized. To investigate the compression behavior of large-scale concrete columns reinforced with HSHTSB under axial and eccentric compression, thirteen reinforced concrete (RC) columns were designed in this paper, including the five columns under axial compression and the eight columns under eccentric compression. The effects of different types of steel bars, transverse steel bar spacing, the configuration of transverse steel bars, and eccentricity on failure modes, load-deformation curves, load-strain curves, ultimate bearing capacity, deformation capacity, and energy absorption capacity were studied in detail. The results show that the cracks are more uniform for concrete columns reinforced with HSHTSB. When the transverse steel bar spacing is less than 80 mm, concrete columns reinforced with HSHTSB with eccentricity ≤200 mm (including eccentricity = 0) have obvious secondary bearing phenomenon, and significantly improve ductility and energy absorption capacity; HSHTSB as longitudinal steel bars can reach yield strength for RC columns under axial compression. For RC columns under eccentric compression, HSHTSB could not reach yield strength on both the tensile and compression side. For the RC columns of Group II, III, and IV, when the eccentricity increases from 100 mm to 400 mm, the ultimate bearing capacity decreases by 76.1%, 75.2%, and 75.1%, respectively. Different from the ordinary RC columns, the ductility decreases with the increase of eccentricity for concrete columns reinforced with HSHTSB. Compared with ordinary RC columns, the energy absorption capacity and deformation capacity of concrete columns reinforced with HSHTSB under axial compression are increased by 120.9% and 116.9%, respectively. Compared with RC columns using transverse steel bars with single-leg, the energy absorption capacity and ductility for multiple-leg can be increased by 111.5% and 103.2%, respectively. When the eccentricity increases from 100 mm to 400 mm, the ductility for columns of Group II and III decreases by 73.5% and 65.9%, respectively. The use of HSHTSB can save the number of longitudinal steel bars and the transverse steel bar spacing while maintaining the bearing capacity, and further improve the deformation capacity. Based on the section strain analysis, the analytical models of the ultimate bearing capacity for the concrete columns reinforced with HSHTSB were established with high accuracy.

Using woven recycled plastic fibers in reinforced concrete beams

The modern lifestyle, along with the advancement of new technologies has produced plastic waste and the recycling of these waste materials has become an important challenge for human societies. Polyethylene terephthalate (PET) is one of the most consuming waste materials. A solution to repel these materials is to use them in the civil engineering industry and buried them in concrete. PET layers and strips were used in reinforced concrete beams instead of steel reinforcements by some researchers. But, in this study, the longitudinal and transverse steel bars were replaced by woven recycled plastic fibers and tested experimentally. These woven PET bars are produced by the authors and used as a structural element. Six beams with different combinations of steel and woven PET bars are tested under two-point loading and the experimental and analytical results are presented. The results show that using these fibers concludes to increases the ductility of reinforced concrete beams. By replacing PET ropes instead of one, two and three tensile steel reinforcements, the ductility ratios of the beams are about 1.73, 1.76 and 4.12 times of the reference reinforced concrete beam. Moreover, some theoretical formulation is presented and compared with experimental data.

Direct numerical simulation of turbulent convection in a channel roughened with circular-arc ribs

Turbulent flows through a channel roughened with circular-arc ribs of different pitch-to-height ratios (P/H=3.0, 5.0 and 7.5) at a fixed Reynolds number are studied using direct numerical simulations (DNS). It is interesting to observe that in contrast to the classical channel flow over transverse square bars, the flow separation point in a channel roughened with circular-arc ribs is sensitive to the testing conditions and varies along the rib arc. The influences of the pitch-to-height ratio on the flow separation, statistical moments of the velocity field, and the anisotropy of turbulence stresses are investigated. The dynamics of coherent structures are studied by examining the skewness of the flow field, characteristics of the joint probability density functions (JPDF) of velocity fluctuations, quadrant analysis of Reynolds stresses, instantaneous velocity field, swirling strength, and temporal–spatial two-point auto-correlations. It is found that the flow anisotropy becomes suppressed as the value of P/H increases due to significant enhancement of the spanwise Reynolds normal stress 〈w′w′〉. It is also interesting to observe that the lifespan of turbulence structures becomes increasingly shortened at the midspan between two adjacent ribs as the pitch-to-height ratio increases.

Experimental and finite element analysis of reinforced concrete multi-cell box girders retrofitted with carbon fiber reinforced polymer strips under torsion

This study expands the state of the art in studies that assess torsional retrofit of reinforced concrete (RC) multi-cell box girders with carbon fiber reinforced polymer (CFRP) strips. The torsional behavior of non-damaged and pre-damaged RC multi-cell box girder specimens externally retrofitted by CFRP strips was investigated through a series of laboratory experiments. It was found that retrofitting the pre-damaged specimens with CFRP strips increased the ultimate torsional capacity by more than 50% as compared to the un-damaged specimens subjected to equivalent retrofitting. This indicated that the retrofit has been less effective for the girder specimen that did not develop distortion beforehand as a result of pre-loading. From experimental observations, when the girder specimen was cracked and the transverse steel reinforcement bars started straining, the CFRP strips started to work more effectively and contributed together with the transverse steel reinforcement to resist torsion load. Additionally, Finite Element (FE) simulations were developed using Abaqus to model the torsional behavior of the retrofitted girders, the results of which were validated with the experimental data. With the numerical model, the effect of concrete compressive strength, transverse reinforcement spacing, and CFRP strip spacing were examined. The effectiveness of the CFRP strips in enhancing the torsional strength of the girder was found to increase with increasing the spacing between the transverse reinforcement.

Description of a new species of Schizodon (Characiformes: Anostomidae) from the upper rio Tapajs basin, Brazil.

A new species of Schizodon with five dark transverse blotches on the body and a large black blotch at the end of the caudal peduncle is described from the rio Arinos, upper rio Tapajs basin, in the Brazilian Amazon. The new species shares a color pattern composed by transverse brown bars and a caudal fin blotch with Schizodon fasciatus and S. trivittatus but possess twelve rows of scales around the caudal peduncle, a unique character among the species of genus.