Plain Cylinder Research Articles

Computational Study of Overtopping Phenomenon over Cylindrical Structures Including Mitigation Structures

Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known.

Micro-electricity generation from wind-induced vibration with magnetostrictive material-based energy harvester

This study aimed to experimentally investigate flow-induced vibration of modified circular cylinders for wind-receiving mast of Vibration-Based Power Generator (VBPG). Specifically, it focused on vibration characteristics of tapered and stepped circular cylinders in VBPG mechanism. Tapering and inverting cylinder model proved effective in reducing Vortex-Induced Vibration (VIV) onset and peak amplitude concerning flow stream velocity. Some tapered cylinder models showed a broadening peak response (upper branch region), showing an extensive power harvesting range for VBPG device. The result showed that the maximum power harvesting of the model with a plain bluff cylinder was 8.45 mW, reduced by tapering bluff cylinder. The power coefficient of VBPG with a normal bluff cylinder was 4 %, but inversing stepped bluff cylinder yielded 5.45 %. It is related to VIV-onset parameter, which was lower than that the plain cylinder. In addition, it was discovered that there was an interdependency between frequency response and power generation capacity for VIV-type resonance. The generated power proved sufficient to illuminate a board with 54 LED lamps in a laboratory-scale test. Meanwhile, an outdoor performance test of harvester, conducted with variable wind speed (0 – 3.2 m/s), showcased the reliability of VBPG mechanism for independent power supply to wireless, remote sensor networks, or moderate scale of power supply. The field test model worked not only in variable wind speed, but also in chaotic wind direction.

Improving the performance of CFRP-reinforced concrete cylinders in sulfate-laden environment through nanoclay modification of epoxy resin

The durability of epoxy-concrete interface is a crucial factor for practical application of externally bonded fiber-reinforced polymer (FRP) retrofit systems, particularly when the strengthened structure is subjected to severe environmental conditions. Given the demonstrated potential of nanoclays in enhancing engineering performance of polymers, this work assesses the beneficial effect of organic montmorillonite (OMMT) nano-modification of epoxy resin on the axial compressive properties of FRP-reinforced concrete under a 10 wt% sodium sulfate wet/dry (W/D) cycling environment. Three types of concrete samples were fabricated and tested: plain concrete cylinders, CFRP-reinforced concrete cylinders using unmodified vs. OMMT-modified epoxy resin as the adhesive, respectively. The optimal dosage of OMMT was determined to be 2 wt% through tensile and lap shear tests, as well as microscopic characterization of the fractured cross-section of the molded resin samples. This optimal dosage of OMMT allows the epoxy adhesive to achieve the highest values in the tensile strength (90.4 MPa), lap shear strength (80.0 MPa), Tg (280.5°C) and water contact angle (115.1°). In the fracture section of epoxy resin with a 2 wt% OMMT, multiple microcracks developed and the OMMT nanoplatelets were well dispersed in the epoxy matrix. The laboratory testing program explored various W/D cycle periods. The experimental results indicate that the OMMT-modified epoxy resin significantly improved the mechanical properties and deformation resistance, altered the failure mode, and effectively delayed the strength degradation of the protected concrete. After 150 W/D cycling days, the OMMT-modified CFRP-confined concrete samples maintained their ductility coefficient and axial compressive strength at 3.58 and 123.5 MPa, respectively, 12.6 % and 9.1 % better than the common CFRP-confined samples. Combining these results with the residual axial compressive strength ratio, we propose an improved design model for calculating the axial compressive strength of CFRP-retrofitted concrete structures in sulfate-laden environments. This study demonstrates the beneficial role of OMMT in enhancing the epoxy adhesive and provides insights into the reinforcement of concrete structures by externally bonded CFRP in sulfate-rich environments.

Aerodynamic drag improvements on a circular cylinder using passive Venturi actuators

Scale-adaptive simulations (SAS) of three-dimensional flow around a circular cylinder fitted with a passive version of a novel flow control method (passive Venturi actuator, PVA) are performed at a diameter-based Reynolds number of Re = 28 000. The PVA consists of one or more narrow slits located at the top and/or bottom sides of the cylinder that connected to the throat of the axial Venturi slit in this cylinder. The main purpose of the study is to investigate the influence of divergence angle and narrow slit location relative to the axial Venturi slit on the aerodynamic performance of the cylinder. To this end, four models were designed with various PVAs. Additional models, a plain cylinder (unmodified model) and a cylinder fitted with an axial Venturi slit (model without a narrow slit), were also used for quantitative comparison. SAS predicts that an additional 5% reduction in the time-averaged drag coefficient, ⟨CD⟩, was observed when two narrow slits located on the surface at an angle of ±80° from the front stagnation line were fitted to the cylinder with an axial Venturi slit. Reducing the divergence angle of the PVA leads to improvements in ⟨CD⟩ and root mean square of fluctuating force coefficients, CD−rms and CL−rms. It is found that a cylinder with a PVA that has two narrow slits and a divergence angle of 6° can produce a 28.6% reduction in ⟨CD⟩, a 58.5% reduction in CD−rms, and an 81.2% reduction in CL−rms, when compared to the plain cylinder.

Experimental investigation of Carbon FRCM confinement effect on concrete cylinders under monotonic loading

In recent years, fabric reinforced cementitious matrix (FRCM) became a desirable material in the rehabilitation of concrete structures. The FRCM system features some advantages such as compatibility with the substrate, easier and non-expensive installation on a wet concrete, and ultraviolet degradation resistance. As FRCM is a new material, the existing literature provides limited knowledge on the effectiveness of FRCM in confining concrete. This paper incorporated an experimental program where plain concrete cylinders were confined with FRCM and were tested under uniaxial compressive loading. The experimental testing parameters included concrete grade, number of FRCM layers and the fibres direction. The test results showed that FRCM was effective in confining plain concrete as the compressive strength increased and a ductile behaviour was developed. Providing more FRCM layers did not enhance the confining action. The application of longitudinally oriented fibres had an insignificant effect on the concrete compression behaviour.

Minero‐chemical and provenance analysis of Achaemenian lapis lazuli cylinders from Persepolis

AbstractFive archaeological plain cylinders made of lapis lazuli found in excavations at the Persepolis World Heritage Site (c.550–330 BCE) were analysed using wavelength‐dispersive X‐ray fluorescence spectroscopy, inductively coupled plasma‐mass spectroscopy, X‐ray powder diffraction, and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy techniques with the goal of characterizing the chemical–mineralogical composition and identifying the possible provenance of raw materials. Results show that these objects are made of identical resources or mines. A comparison with available data from archaeological sites and ancient quarry sites shows that these finds may have been produced from lapis lazuli from east of the Iranian Plateau (Badakhshan in Afghanistan), as they resemble several ancient objects of Iran. The results of this study suggest that Persian artists also used the ancient East‐to‐West trade route for supplying raw material to produce decorative objects made of lapis lazuli.

Thermal and vibratory response of sprung square cylinder with four nature-inspired fin-shaped bumps

Nature provides man with various interesting structures, offering him a constant source of manufacturing tools and invention. The main purpose of the present paper is to investigate the effect of shark-inspired fins, which are installed on the top and bottom plates of a sprung cylinder on the vibration response and heat transfer of square cylinder. Two fin sizes, i.e. small and big, are used. Three configurations for the fins on the top and bottom plates of the square cylinder are considered: at the corners of the square cylinder, spaced from the corners, and in the middle of the plates. The results indicate that adding fins increases the amplitude of vortex-induced vibrations and extends the lock-in region which is both intensified as the size of fins increases. In particular, for the cylinder equipped with small fins in configurations 1–3, the maximum VIV amplitude increases by, respectively, 36 %, 57 % and 52 % compared with the plain cylinder. In contrast, shark fins can lower the galloping amplitude by as much as 87 % and shrink the galloping zone such that for big fin size in the second and third configurations, the galloping zone and its corresponding vortex-shedding mode are not observed. Adding fins to the cylinder augments heat transfer. The increase in mean Nusselt number depends on vortex-shedding mode, and the rise in Nusselt number is higher in the 2P + 2S mode.

A bi-directional flow-energy harvester

Due to a rapid decrease in fossil fuel resources and ever-growing carbon emissions, clean energy is urgently needed as a vital solution. In the past two decades, harvesting clean energy from ambient environment has attracted much attention. Flow induced vibration and energy harvesting performance of a cylinder with fins attached were investigated. Four configurations were studied: a plain cylinder, a cylinder with two windward fins, a cylinder with two leeward fins, and a cylinder with four fins. These four cylinders were tested in a water channel with a reduced velocity ranging between 2 and 25 and a Reynolds number ranging between 1500 and 11 400. It was found that the two-windward-fin cylinder underwent galloping, exhibiting much larger vibration amplitudes and a much broader operational velocity range, whereas the two-leeward-fin cylinder only underwent weak vortex-induced vibrations. By attaching both two windward and two leeward fins to the cylinder, a bi-directional flow-energy harvester was implemented, which outperformed the plain cylinder with much larger vibration amplitudes and a much broader velocity range. More importantly, due to the geometric symmetry, it is able to harvest flow energy from two opposite directions. A tuned-mass-damper system was then attached to the four-fin cylinder for the purpose of demonstration. Within the current flow speed range, the maximal voltage and power outputs are about 7.37 V and 1.81 μW, respectively, about 2.7 and 7.2 times the plain cylinder's peak values. The effects of flow incident angle and fin length were also studied. Numerical simulations were also conducted to provide a detailed information of flow and pressure to uncover the underlying physics. This bi-directional flow-energy harvester is a suitable candidate to operate at sites where the flow periodically switches its directions, such as in tidal flows.

Numerical analysis of heat transfer enhancement in grooved vertical Multi-Cylinders at various groove geometries

In this study, the natural convection enhancement in grooved vertical multi-cylinders at various groove geometries is investigated. The effects of several grooves ranging from 3 to 7, groove thickness ranging from 0.25 to 1 mm, and cylinder surface temperature ranging from 350 to 500 K at different Rayleigh numbers are examined. The current study was simulated using the finite volume method using CFD with a laminar steady-state condition. The SIMPLE scheme is used for the pressure–velocity coupling discretization and the second-order upwind method is utilized to discretize the momentum and energy equations. The results obtained from the present research show that the presence of grooves on the cylinders will increase the heat transfer surface, create and intensify the secondary flow and mixing, and ultimately increase the heat transfer. Moreover, by increasing the number of grooves and its thickness, the amount of heat transfer increases dramatically. It’s also found that the groove thickness parameter's effectiveness on heat transfer is more than the groove number parameter. Ultimately, it’s demonstrated that using grooved cylinders leads to a 14 % augmentation in Nusselt number in comparison with employing plain cylinders.

KARAKTERISTIK PEMANEN DAYA LISTRIK BERBASIS GETARAN STRUKTUR

Mechanical vibration is a potential source of micro-electrical energy harvesting mechanisms for micro electrical power supply for IoT system networks, wireless and sensors where the power requirements are relatively lower and available independently. In this study, the characteristics of the cylinder vibration response as a trigger for energy harvesting from flow-induced vibrations at various air velocities were investigated experimentally in a wind tunnel test section. Harvesting of micro power from cylinder’s motion by using galfenol (Fe-Ga) material was also investigated simultaneously. The maximum cylinder’s vibration response was obtained by using the plain cylinder model. Cylinder taper variation reduce the maximum vibration response. The position of the major (D) and minor (d) (or inverse position) diameters also affects the vibration response. However, tapering the cylinder reduces the onset vibration with respect to the flow velocity. The frequency of the vortex (Strouhal, St) ranges from 0.25 to 0.12. The minor diameter of the tapered cylinder has the effect on decreasing the vibration response and tends to be stationary. Minor diameter reduction reduces the potential for vibration to the structure. The maximum power generated by the test model is about 8.5 mW with the power RMS value of 2.3 mW and power coefficient about 4%.

STUDY OF FLOW CHARACTERISTICS OVER HEATED PLAIN AND DUAL-STEP CYLINDERS

This work investigated flow past a dual-step cylinder at different wall temperatures, numerically and experimentally. The numerical work was carried out with the help of the computational fluid dynamics solver, Ansys Fluent. For validation, experiments were performed on a wind tunnel for the circular cylinder with step down (<i>D/d</i> < 1), step up (<i>D/d</i> > 1), and plane cylinder (<i>D/d</i> = 1). The drag coefficient was calculated based on the pressure measurements on peripheral points around all three cylinder cases. The results illustrate that the plain cylinder shows a maximum negative magnitude of pressure coefficient, whereas the step-down cylinder shows a minimum. The primary vortices interact with step-induced vortices clockwise and counterclockwise, producing different wake flow characteristics compared to the plane cylinder. Further, the results suggest that the ability to transfer heat from the cylinder wall to the fluid medium is higher for the cylinder with a diameter ratio of <i>D/d</i> < 1.

Passive control of vortex-shedding past finite cylinders under the effect of a free surface

Passive technologies for the control of the flow past bluff bodies have been widely studied. Most of these works have focused on high-aspect-ratio, wall-mounted, or infinitely long cylinders, leaving a gap for low-aspect-ratio bodies fully submerged or under the effect of a free water surface. This is the object of the present work. Detached-eddy simulations at a Reynolds number of 1000 have been carried out for infinitely long (case i) and low-aspect-ratio bodies. For the finite case, two configurations were investigated: bodies fully submerged in the flow, away from surface effects (case ii) and that involving a free surface, here represented by a fixed slip-allowing plane (case iii). These computations were conducted for the bare cylinder and the system is comprised of the same main body fitted with eight wake-control rods uniformly distributed around its perimeter. Results showed that the low-aspect-ratio cases relative to infinitely long structures (1) lowered mean drag and root mean square lift, (2) presented a less coherent wake topology, (3) had frontal rods that concentrated most of the hydrodynamic loads, (4) extended the formation length, and (5) although all cases developed larger hydrodynamic loads when the rods were fitted to the main body compared to the plain cylinder, the finite cases produced a lower increase. We show that these results are intrinsically related to end effects and associated with a less correlated wake lacking coherent vortical structures. Furthermore, we analyze the more accentuated streamwise vortices produced by the presence of the free surface in case iii compared with case ii.

On accurate measurement of non-uniform displacement gradient

Commonly, the displacement gradient is measured, assuming its variation to be uniform. Systematic error arising due to local uniform approximation of non-uniform displacement gradient is investigated for in-plane periodical varying displacement gradient through the Taylor method. The Taylor method’s calculated bound is loose and at variance with the experimental observations. Consequently, an alternate error bound, based on Fourier representation, is proposed, which yields a tighter bound and provides the explanation for the experimental observations. The analytical results are verified through experimental investigation on a plain concrete cylinder subjected to uniaxial compression. The most significant findings are (1) for a body exhibiting periodically varying displacement gradient, the strain measurement would be repeatable for gauge length at least twice the displacement gradient periodicity but would have significant error, and (2) orthogonal gauge orientation (0–45–90 rosette) renders more accurate strain measurement than skewed arrangement (0–60–120 rosette).

Entropy generation analysis and simulation of turbulent forced convection around tube with integral wake splitter using artificial neural network approach

This paper deals with the investigations on entropy generation around a circular plain tube with integral downstream splitter plates with cross flow of air in a rectangular duct. This study is carried out in the Reynolds number range 49 × 103 to 227 × 103 on single plain cylinder and single cylinder of various splitter length-to-tube diameter ratios, L/D = 0, 1/3, 2/3, 1, 3/2, 2 and 5/2. Entropy generation characteristics are studied under constant heat flux and temperature conditions and simulated using the artificial neural network (ANN) algorithm. The analysis of the second law of thermodynamics, which considers both the heat transfer and pressure drop effects, indicated the addition of the plate decreases the entropy generation with increased plate length, the entropy generation number being more sensitive to the Reynolds number as plate length increases. entropy generation reduction was, in general, also evident with increased plate length. Results point towards tube with wake splitter being more efficient than plain tube based on entropy generation. The predicted values of the entropy generation number of augmented design, NS,a, using the ANN algorithm are compared with the calculated results. The results showed that the ANN model has good expectation performances with error approaches zero without conducting extra experiments consuming time, money and effort or solving nonlinear mathematical models. Owing to its performance, ANN is a good choice for modeling the entropy generation around a circular plain tube with integral downstream splitter plates.

Investigation of the possible applications for microtextured rolling bearings

The application of microdimple-textured surfaces for rolling bearings is not very common but can be beneficial for various usage scenarios. In contrast to the applications for plain bearings or cylinder running surfaces, however, surface patterns for rolling bearings only offer advantages under certain conditions. For example, for use with start-stop cycles, in mixed lubrication conditions, or under sliding conditions in a bearing as well as on a roller—bearing flange contact, friction can be reduced with the targeted use of microtextures. The geometry of the microtextures must be chosen so that individual dimples fit in the contact area between the ball or roll and the bearing surface in order to act as a reservoir for the lubricant. First applications for microtextured angular contact ball bearings under oscillating movement conditions proved friction reducing effects under reciprocating motion. In this case the microtextures served as lubricant reservoirs. The idea is transferred to the sliding contact for tapered roller bearings; it is investigated whether the measured reductions in friction are due to the microtextures serving as lubricant reservoirs or whether there is even a positive hydrodynamic effect caused by the microtextures. By means of a calculation approach as well as some exemplary test rig measurements, the behavior for microtextured tapered roller bearings is investigated.

Acoustic emission characteristics of concrete cylinders reinforced with steel-fiber-reinforced composite bars under uniaxial compression

An experimental study of the acoustic emission characteristics of concrete cylinders reinforced with steel fiber-reinforced composite bars (SFCB) under uniaxial compression was performed. SFCB-reinforced concrete cylinders, plain concrete cylinders, and fiber-reinforced polymer (FRP) bar-reinforced concrete cylinders were tested under uniaxial compression. The entire failure process of different concrete cylinders was monitored in real time using acoustic emissions (AE). Damage characteristics of the cylinders were analyzed using the AE hit number distribution, Ib value analysis method, and AE event location and energy. The Ib value characteristics were closely correlated with the microcracks and their extension inside the concrete cylinders. For the reinforced concrete cylinders, the damages were predominantly microcracks of the concrete observed before the first turning point of the load-displacement curve. Subsequently, damage to the longitudinal SFCBs and FRP bars occurred. The AE characteristic of FRP reinforcement damage was similar to that of the macroscopic crack damage in concrete, that is, with a small Ib value. According to the AE event location analysis, the plain concrete cylinder demonstrated obvious shear failure, which was primarily suppressed in the reinforced concrete cylinders owing to the confinement effect of the spiral. The AE energy released by the compression damage of the longitudinal FRP bar was higher than that released by the tensile damage of the FRP spiral. This could trigger a distinguishable high AE location source amplitude for detecting the compression damage to the FRP bar. The analysis of the AE event distribution characteristics proves that the SFCB has a stable post-yield stage, and the compressive damage process of the SFCB is relatively stable and mild compared with the FRP bars in concrete cylinders.

Compressive Behavior of Predamaged Concrete Cylinders Repaired with Jute and Basalt FRP Composites: A Comparative Study

Natural fibers have become a research hotspot in composite materials recently. This study investigated the axial compressive behavior of predamaged concrete repaired by jute fiber–reinforced polymer (JFRP) composites. Basalt FRP (BFRP) was also utilized to repair the predamaged concrete for comparison. Thirty FRP-jacketed concrete cylinders with a diameter of 150 mm and a height of 300 mm were designed and fabricated. Plain concrete cylinders were axially preloaded to three predamage levels, then repaired by JFRP and BFRP composites, and reloaded to evaluate the compressive behavior after repair. The results showed that the predamage of concrete had a noticeable adverse effect on the compressive behavior of JFRP- and BFRP-repaired concrete. Compared with the JFRP-jacketed intact concrete, the compressive strength and initial elastic modulus of the JFRP-repaired predamaged concrete decreased by 6%–18% and 16%–54%, respectively. However, the compressive strength and ultimate strain of the predamaged concrete were still improved by 5%–41% and 82%–291% after JFRP repair, respectively, when compared with those of the plain concrete. On the contrary, the ultimate axial strain and lateral strain capacities of JFRP- and BFRP-repaired concrete were insignificantly affected by the concrete predamage. Under similar confinement ratios, the compressive strengths of JFRP- and BFRP-jacketed intact concrete were close to each other, whereas the axial strain–lateral strain relationship and the variations of the Poisson’s ratios were highly dependent on the FRP types and the number of FRP layers. Based on the test results and data collected from the open literature, an ultimate strength model, an ultimate axial strain model, and a stress–strain relationship model were newly developed for JFRP-repaired predamaged concrete.

Strengthening of plain concrete cylinders with hybrid composites based on basalt and sisal fiber systems

Strengthening and rehabilitation of concrete structures are becoming popular in the construction industry using synthetic fiber reinforced polymers (FRP). However, it has a major drawback due to their economic and environmental impacts. The study focuses on investigation of strength and ductile behavior of concentrically loaded hybrid sisal basalt FRP (HSBFRP) confined concrete structures. A combination of natural sisal and basalt fibers were proposed as the hybrid system. Confined concrete cylinders with different layers of hybrid FRP systems were subjected to various strength tests and test results proved that hybrid FRP confinement intensify the axial load-carrying capacity compared to unconfined specimens. A relative performance analysis of hybrid sisal-basalt FRP confinement with basalt and sisal individual FRP confinements was performed. From the test results it was noticed that the ultimate load carrying capacity increased by 63% along with a fracture energy of 23.17 MPa when the cylinders were confined with 5 layers of hybrid confinement. When compared with unconfined specimens the ductility index attained a maximum value of 4.31 when confined with multiple layers of sisal and basalt FRP wraps. It was proved that with the concept of hybridization in confinement, there was a significant enhancement in fracture energy and ductility index for concrete, thus preventing catastrophic failure.

The Saliency of Snake Scales and Leopard Rosettes to Infants: Its Relevance to Graphical Patterns Portrayed in Prehistoric Art.

Geometrically arranged spots and crosshatched incised lines are frequently portrayed in prehistoric cave and mobiliary art. Two experiments examined the saliency of snake scales and leopard rosettes to infants that are perceptually analogous to these patterns. Experiment 1 examined the investigative behavior of 23 infants at three daycare facilities. Four plastic jars (15×14.5cm) with snake scales, leopard rosettes, geometric plaid, and plain patterns printed on yellowish-orange paper inside were placed individually on the floor on separate days during playtime. Fourteen 7–15-month-old infants approached each jar hesitantly and poked it before handling it for five times, the criterion selected for statistical analyses of poking frequency. The jars with snake scales and leopard rosettes yielded reliably higher poking frequencies than the geometric plaid and plain jars. The second experiment examined the gaze and grasping behavior of 15 infants (spanning 5months of age) seated on the laps of their mothers in front of a table. For paired comparisons, the experimenter pushed two of four upright plastic cylinders (13.5×5.5cm) with virtually the same colored patterns simultaneously toward each infant for 6s. Video recordings indicated that infants gazed significantly longer at the cylinders with snake scales and leopard rosettes than the geometric plaid and plain cylinders prior to grasping them. Logistic regression of gaze duration predicting cylinder choice for grasping indicated that seven of 24 paired comparisons were not significant, all of which involved choices of cylinders with snake scales and leopard rosettes that diverted attention before reaching. Evidence that these biological patterns are salient to infants during an early period of brain development might characterize the integration of subcortical and neocortical visual processes known to be involved in snake recognition. In older individuals, memorable encounters with snakes and leopards coupled with the saliency of snake scales and leopard rosettes possibly biased artistic renditions of similar patterns during prehistoric times.

Tensile Performance, Lap-Splice Length and Behavior of Concretes Confined by Prefabricated C-FRCM System

Results of an experimental study aimed to evaluate tensile performance, lap-splice length of carbon fabric-reinforced cementitious matrix system (C-FRCM), and performance of concretes confined by C-FRCM are presented. Green high-strength mortar was used in this study which actively utilized recycled fine aggregate and fine waste glass powder to partially substitute cementitious binder. Test plans were developed in due consideration of prefabricated C-FRCM for strengthening concrete columns: 14 tensile tests, 12 lap-splice tests, and 6 uniaxial compression tests of plain concrete specimens confined by C-FRCM were performed. Test variable for the tensile test was number of fabric layers (one or two layers). Nominal strength of the C-FRCM with two fabric layers was 11.0 MPa while it was 7.4 MPa with one fabric layer in tension. Full strength of the carbon fabric was developed in all tensile tests while the C-FRCM with two fabric layers (with axial fiber amount = 0.59% by vol.) showed pseudo-ductile behavior. From the lap-splice tests in direct tension, an increased lap-splice length was required for the double fabrics over that for the single fabrics. The required splice length was about 170 mm for the single fabrics and it was about 310 mm for the double fabrics. Plain concrete cylinders and prismatic specimens were laterally confined by C-FRCM and subjected to uniaxial compression. All test results showed strain-softening behavior. Compressive strength increased by 10–41% while ductility also increased by 6–45% indicating applicability of the prefabricated type C-FRCM in the future.