Arrangement Of Bars Research Articles

The shear performance of DSCW-RC joints with lap-spliced steel bars

The double steel plate concrete composite shear wall (DSCW) structure combines the advantages of steel and concrete, offering high strength, stiffness, and durability. The joint formed by the DSCW and reinforced concrete foundation (RC foundation) was often unavoidable in engineering practice. Research related to the mechanical behavior of the DSCW-RC foundation is limited. This paper investigated the shear performance of DSCW-RC joints with lap-spliced steel bars. A total of seven specimens were designed and tested. The influences of steel plate thickness, steel bar arrangement, and stud spacing on the shear behavior of the joints are elucidated. The test results indicate that the predominant failure mode of the specimens occurred in the upper part of the local steel plate, with reinforcement yielding. While steel bar diameter and stud spacing minimally affected the shear strength, they significantly influenced the failure displacement at the joint interface. The failure deformation increased with increasing steel bar diameter and decreased with increasing stud spacing. Moreover, the thickness of the steel plate profoundly impacted structural shear strength and deformation, with both deformation and bearing capacity increasing with plate thickness. In addition, this study explores the force-transferring mechanism of such joints under shear load, offering a crucial reference for subsequent analyses of the composite force mechanism of DSCW - RC foundation joints.

Anthropogenic noise and impact on marine species : Acoustic metamaterials as a reduction solution

Anthropogenic underwater noise generated by offshore maritime activities poses a significant threat to nearby ecosystems due to elevated sound levels. Efforts have to be undertaken on noise reduction solutions, depending both on the offshore activities and on the marine species. In this context, leveraging the recent advances in underwater acoustic metamaterials seems crucial, due to their special properties in terms of scattering and absorption. This endeavor aligns with advancing Marine Renewable Energies while minimizing environmental impact. In this communication, a synthetic review is first proposed to define the various maritime works targeted, as well as their associated sound levels and frequency ranges of emission. In a second part, a cartography is outlined by classifying different marine species according to their hearing type, depth of immersion and auditory threshold. Then, in relation with the two previous analyses, solutions based on metamaterials for deep sea immersions are proposed. In particular, a multi-periodic arrangement of bars is proposed that exhibits several band gaps (i.e. frequency ranges in which propagation is forbidden), in order to limit the transmission of sound waves in a large frequency range. The concept can be easily extended depending on the targeted offshore activities and marine species.

Rest length controlled tunable band structure in periodic tensegrity metastructure – a numerical study using a novel consistent stiffness and mass formulation

Elastic wave propagation in various periodic metastructures and its application to wave filtering, vibration isolation, acoustic cloaking, etc., have gained significant attention among researchers in recent years. Despite the presence of band gaps, traditional lattice structures lack dynamic tunability. The solution lies in using tensegrity as unit cells. This article presents analysis of tunable wave propagation through a metastructure formed by tessellation of a 2D tensegrity unit cell in one dimension. Equations of motion of the unit cell are derived with consideration of flexibility and distributed mass of the bars, which is often neglected in the literature. The formulation is extended for wave dispersion analysis using the Floquet–Bloch theory. Next, the order of the formulation is reduced for decoupled analysis of symmetric and antisymmetric modes. The dispersion relations for different modes have been validated with nonlinear as well as linearized frequency response analysis under impulse load. Next, the effect of rest length of strings and alternating arrangement of bars on band gaps is studied in detail.

Analytical model of penetration depth and energy dissipation considering impact position

In the research of projectile penetration into reinforced concrete, the discreteness of penetration depth widely exists in the experiments and empirical formulas, and different impact positions are one of the main reasons for this discreteness. However, the existing theoretical models considering impact position require self-programming methods to solve, and analytical solutions for penetration depth have not been provided. Moreover, existing penetration depth formulas have not dealt with the influence of impact position on penetration depth. To incorporate the influence of the impact position in the penetration depth formulas, this study has investigated different impact positions of the projectile penetration. Herein, the Young formula is used as an example, the projectile penetration process is regarded as a uniformly variable motion based on the constant resistance assumption, two methods are used to obtain the penetration constant resistance, and the energy dissipation of the steel bar at three typical impact positions is theoretically modeled. Finally, analytical solutions for the penetration depth at the three positions are proposed and the mechanism of differences at the three typical impact positions is revealed. In addition, finite element models are established for the three impact positions based on published penetration tests. The penetration depth and steel bar energy consumption of the three impact positions are compared and analyzed, and the analytical model is verified. The results suggest that different impact positions can cause different energy consumption of the steel bar, ultimately leading to varying penetration depth. This analytical model, which fully considers the impact positions of the projectile and the arrangement of the steel bars, can be generalized to any penetration resistance theoretical model or penetration depth calculation formula. It can play an important role in further improving and developing the penetration depth calculation formula, and guiding the design of reinforced concrete protection engineering.

Experimental study on seismic performance of squat precast concrete sandwich shear walls under low axial load ratio

To improve the thermal performance and seismic resistance of structures, precast concrete sandwich shear wall (PCSSW) emerges as a promising option due to its low thermal conductivity and favorable structural performance. This study aims to examine the effectiveness of a new type of vertical connection between the PCSSW and foundation under reversed cyclic loading. The proposed vertical connection is achieved by embedding steel bars in the precast wall and foundation, respectively, followed by casting fresh concrete in place. Considering pre-embedded steel bar arrangements (single-row or double-row) and cast-in-place (CIP) concrete strength as variables, three precast specimens were designed. Seismic performance was investigated through low reversed cyclic loading tests, with a comparison made against two CIP control specimens. The results showed that the behavior of all the tested walls was governed by shear, with the ultimate bearing capacity of the PCSSW determined by the horizontal shear capacity at the weak position. Under low axial compression ratios, the specimens with double-row steel bar arrangement had higher load-carrying capacity and ductility than single-row steel bar arrangement and could be equivalent to the CIP shear walls. Results from this study were compared with the predicted values from different codes to provide some reference value for the engineering design of the proposed structure.

Design optimization of obstacle avoidance of intelligent building the steel bar by integrating reinforcement learning and BIM technology

In promoting the construction of prefabricated residential buildings in Yunnan villages and towns, the use of precast concrete elements is unstoppable. Due to the dense arrangement of steel bars at the joints of precast concrete elements, collisions are prone to occur, which can affect the stress of the components and even pose certain safety hazards for the entire construction project. Because the commonly used the steel bar obstacle avoidance method based on building information modeling has low adaptation rate and cannot change the trajectory of the steel bar to avoid collision, a multi-agent reinforcement learning-based model integrating building information modeling is proposed to solve the steel bar collision in reinforced concrete frame. The experimental results show that the probability of obstacle avoidance of the proposed model in three typical beam-column joints is 98.45%, 98.62% and 98.39% respectively, which is 5.16%, 12.81% and 17.50% higher than that of the building information modeling. In the collision-free path design of the same object, the research on the path design of different types of precast concrete elements takes about 3–4 minutes, which is far less than the time spent by experienced structural engineers on collision-free path modeling. The experimental results indicate that the model constructed by the research institute has good performance and has certain reference significance.

Experimental Study on the Mechanical Performance of Column Underpinning Joints with Prestressed U-Shaped Steel Bars

To meet the requirements of highly efficient force transmission, easy operation and low damage in RC column underpinning engineering, a new underpinning joint with prestressed U-shaped steel bars was proposed. Static testing of seven specimens was carried out, and the number of the U-shaped steel bars, their arrangement and the pre-pressure acting on the joint were considered as the main parameters. The results demonstrated that the U-shaped steel bars might greatly increase the load-bearing capacity of the underpinning joint, and the more the number, the higher the capacity; the arrangement of the U-shaped steel bars also had a significant effect on the load-bearing capacity. Two pairs of the U-shaped steel bars arranged on the opposite sides of the column was better than that arranged on four sides. And the horizontal part of the UsSBs embedded in the column grooves was better than in the underpinning beams; the pre-pressure could effectively improve the sliding stiffness of the underpinning joint, while the effects on the load-bearing capacity was not obvious. Based on the curve of load-displacement, force process of the underpinning joint was divided into four phases: no slip, initial slip, interfacial slip expansion and punch slip, consequently a constitutive force-slip model was constructed. As a result, a simple mechanical model of the underpinning joint was established, and the calculation formula for the load-bearing capacity of the new joint was proposed. Finally, the engineering design expression was prepared according to the characteristics of the real underpinning project.

Effect of interface layout design of a public library website on information-seeking experience for elderly people

PurposeTargeting the common functions of the Zhejiang Library website, elderly individuals were invited to complete six experimental tasks on the improved website interfaces, and subjective data (PAD emotion scale and usability evaluation) and objective data (eye movement data) were recorded to verify the effects of graphic layout and navigation position on the information-seeking experience of elderly individuals.Design/methodology/approachThis study analyzes the effect of the graphic layout and navigation position of the Zhejiang Library’s website interface on the emotional state, perceived usability and information-seeking time of elderly individuals, with the aim of providing guidance and suggestions for the elderly-oriented reform of the public library website.FindingsThe experimental results show that the graphic layout has a significant effect on the emotional state and perceived usability of elderly individuals, and the navigation position has a significant effect on the information-seeking time; the interaction between graphic layout and navigation position exerts a significant effect on the information-seeking time of elderly individuals. The eye movement data show that elderly individuals have a better information-seeking experience when the top navigation bar and image-text matched arrangement are used for the interface layout.Originality/valueThis study adopts a new approach combining subjective data and eye movement data to evaluate the effect of the public library website’s interface layout on the information-seeking experience for older people. The findings can provide a theoretical basis and methodological support for the elderly-oriented reform of public library websites. They can also provide scientific design suggestions for age-friendly interface layouts of other Internet products and service applications.

Flexural behavior of high-strength RCFST column-to-column connections

This paper investigates the flexural behavior of high-strength rectangular concrete-filled steel tubular (RCFST) column-to-column connections with different configurations. Based on the tests, 35 additional finite element analysis (FEA) models were developed to perform the parametric analysis varying with the cross-sectional size effect of (D), the width-to-thickness ratio of steel tube (D/t), steel tube strength (fs,y), steel bars strength (fr,y), concrete strength (fc,r), length of steel bars (L), arrangement and quantity of steel bars, respectively. The current code underestimated the yield and plastic bending moment compared with the calculated results from GB 50010–2010, ACI 318–19, EN 1992–1-1:2004, and JSCE-SSCS-2007. Finally, the strain coordination method and the full plastic section method were proposed to calculate the yield and plastic bending moment of the connection.

Evaluation of Errors Associated with Crosstalk Magnetic Field using Finite Element Method in High Electrical Curretn Measurement

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Monitoring of fracture processes in reinforced concrete beams with DFOS: feasibility study

In this paper, we present the application of distributed fibre optic sensors (DFOS) for the detection of bending and shear cracks in reinforced concrete beam specimens loaded in three- and four-point bending in lab conditions. The main goal of this study is to prove the feasibility for future application of DFOS for monitoring of existing concrete structures such as bridges or tunnels. Each specimen was equipped with more optical fibres: most of them were externally attached in the grooves at the outer surface of the specimens and some of them were inside the specimens. Specimen geometries, arrangement of reinforcement bars and loading schemes of the specimens were determined by non-linear FEM before the tests, so that either dominant bending or dominant shear cracks appear during the loading. Some specimens were loaded step-by-step and some of them by continuous loading and the results were compared afterwards. The results showed, that DFOS can ensure exact crack monitoring in all loading stages of the reinforced concrete specimens, which is a good basis for future applications for monitoring of structures in the engineering practice.

Biaxial bending of RC rectangular column sections: Improved ‘load contour’ formulation

AbstractIn design practice, the safety of any given rectangular reinforced concrete column section is checked by ensuring that all possible combinations of axial compression (Pu) and biaxial moments (Mux, Muy) at the ultimate limit state lie within its three‐dimensional load–moment interaction failure surface. Although such a check is facilitated by commercial software packages, it is traditionally carried out with the help of an approximate formulation of the ‘load contour’ at any given axial load level, first proposed by Bresler. The present study proposes an efficient algorithm, using a ‘modified thick layer integration’ approach and a ‘nested bisection’ method, to generate the ‘exact’ load contour (and thereby, the complete interaction surface) for any symmetrically reinforced column section, complying with the strength design requirements of ACI 318 (or EC2 or IS 456). The algorithm also generates a measure of the safety margin, called ‘demand‐to‐capacity ratio’ (DCR), defined as the ratio of the resultant design moment (Mu) to the moment capacity (Muθ) at a given axial load level (Pu). For an optimal code‐compliant design, the peak value of DCR generated from various factored load combinations (obtained from frame analyses) must be close to 1.0. The extent to which the peak DCR is less (or greater) than 1.0 provides a measure of over‐design (or under‐design) in a given context. After validating the algorithm, a parametric study was carried out on a spectrum of 36 different cross‐sections having different aspect ratios, bar arrangements and reinforcement percentages. The study reveals that the exponent in the approximate load contour formulation depends not only on the axial load (as currently assumed in ACI: SP17, EC2 and IS 456), but also on the percentage of longitudinal reinforcement. Accordingly, modifications have been suggested to improve the accuracy in these code‐prescribed approximate formulations of the load contour, for more economical and safe design.

A Split Hopkinson Pressure Bar Investigation of Impact-Induced Reaction of HMX, RDX and PETN

We have used a split Hopkinson pressure bar arrangement to investigate impact-induced reaction of the secondary explosives HMX, RDX and PETN in granular form. Sentencing of the experiments was performed by detecting reaction light emission, the spectral analysis of which can also provide information about the temperature of reaction. We measure the fraction of the mechanical energy that passes through the specimens that is absorbed in the run up to reaction, which we refer to as the efficiency factor, and for these experiments is of order 5–10%. We postulate that the efficiency factor is a function of the microstructure. The measured amounts of energy that were absorbed are comparable to those amounts required to bulk heat the samples to their melt points. A critical absorbed energy for reaction implies a minimum duration of loading for a given mechanical power and efficiency factor, and this idea is supported by the observation that the more intense the loading, the shorter the time to reaction. Additionally, we postulate a critical minimum mechanical power below which heat is redistributed faster than it can be accumulated. A minimum mechanical power threshold in turn dictates a minimum pressure threshold; but the idea of a stand-alone critical pressure is not experimentally supported.

Cutting Stock Problem (CSP) applied to Structural Optimization for the minimum waste cost

AbstractIn this study, an optimization method to design simple truss structures for the evaluation of the optimal stock of existing elements is introduced. To achieve this goal, the well‐known Bin Packing Problem (BPP) will be implemented within the structural optimization procedure. Specifically, among all the BPP variants, one of the most common applications in real‐world cases is the Cutting Stock Problem (CSP) in which the objective is to produce dj copies of each item type j by employing the minimum number of bins. In the civil engineering field, structural optimization is often employed aiming to improve the load‐bearing capacity of the structure itself, i.e. maximization of the performance ratio through the minimization of the structure weight. However, this goal doesn't guarantee maximum efficiency in terms of minimization of waste during the industrial production phase. To overcome these limits, authors propose a stock‐constrained structural optimization in which a heuristic search technique is adopted and the best arrangement of bars whit the lowest cut‐off waste is obtained for a 10‐bar‐truss case study. For completeness reasons, a comparison between the solution obtained by the classic minimum weight optimization problem and the stock‐constrained one is discussed.

Impact performance of fire-damaged hybrid steel-BFRP reinforcement concrete beams: Influence of area ratio and arrangement of BFRP bars

Hybrid steel-BFRP reinforced concrete (HRC) beams have demonstrated their ability to meet the rigorous demands for both strength and serviceability. However, the mechanical properties of HRC beams under fire accompanied by impact loadings are not yet clear. In order to delve into the impact resistance of HRC beams under high temperatures, a three-dimensional numerical model was crafted to account for both the effects of strain rate and temperature degradation. The study aimed to examine how the impact resistance of HRC beams is influenced by varying area ratios and arrangements of BFRP bars. The model's reliability was ascertained through a comparison between its simulation outcomes and the results of physical tests. The results show that HRC beams exhibit a significant reduction in stiffness, impact and internal force under fire conditions (39 %, 38 % and 72 % for a fire duration of 45 min, respectively). Furthermore, the damage is concentrated in the mid-span. The impact performance of HRC beams at room and high temperatures is between those of pure steel-RC beams and pure-BFRP beams. The variations under the same fire conditions in the displacement and internal force of beams with different BFRP bars area ratios reach 70 %, while with different arrangements of BFRP bars do not differ much (within 20 %). The dynamic to static stiffness ratio and ultimate load ratio is reduced following the growth of BFRP bars area ratio (max. gap up to 56 % and 25 %) and fire time (max. gap up to 15 % and 20 %). Therefore, specimen design prioritizes the bar arrangement with better corrosion resistance. Additionally, the residual bearing capacity of HRC beams is only 10–40 % of the original under 45 min fire duration. The association of residual load capacity and displacement with fire time shifted from linear to nonlinear with rising temperature.

Experimental Study on the Wear Characteristics of Textured Joint Surfaces under Bionic Lubrication

Ti15Mo7Zr15Ta1.00Si titanium alloy contained higher concentration of silicon and better elastic properties, excellent biocompatibility and lower processing cost. To investigate the influence of texture shapes and parameters of joint surfaces on the friction and wear properties under bionic lubrication conditions, three types of texture morphologies (circular, elliptical, and equal-width grating) with the same pit depth and surface coating rate were processed on a Ti15Mo7Zr15Ta1.00Si titanium alloy using a picosecond laser processing system in this study. Then, the "ceramic–metal" friction and wear tests of textured and smooth samples under lubrication with bovine serum protein were performed using a UMT-3 multifunctional friction and wear testing machine. The results showed that the surface micro-texture morphology could improve the anti-friction properties of titanium alloy artificial joint materials. The wear resistance of the circular micro-dimples improved with an increase in the circular diameter. In the elliptical micro-dimple texture morphology, the vertical arrangement of the ellipses could provide the maximum bearing capacity and best friction reduction effect, followed by the elliptical morphology and the transverse ellipse arrangement. The denser the arrangement of the equal-width bars, the better the friction reduction effect was.

Experimental and analytical investigation on the compressive behavior of double-skin steel-concrete composite tube walls

An innovative structural wall named double-skin steel-concrete composite tube(DSCCT) wall is proposed in this paper. The proposed wall is composed of rectangular steel composite tube, in-filled concrete, external concrete and stud-tie bar connectors. Sixteen full-scaled DSCCT wall specimens and two reinforced concrete walls (RCW) specimens were tested under axial monotonic compression to investigate their load bearing capacity. Parameters included are the double-skin steel plates thickness, steel plate slenderness ratio (the distance to thickness ratio of the stud-tie bars), stud-tie bar arrangement etc. The vertical load-displacement responses of the test specimens are discussed along with their stiffness, strength, and deformation capacity. Experimental results indicate that the DSCCT specimens exhibited a fairly good bearing capacity, the external concrete, steel composite tube and in-filled concrete could work together well. The greater the thickness of the double-skin steel plate, the greater the buckling wavelength; The smaller steel plate slenderness ratio, the later the local buckling of the double-skin steel plate occurred, and the higher the bearing capacity of the DSCCT wall specimens. The displacement ductility coefficient of the DSCCT wall specimens was higher than that of RCW specimen. Considering the local buckling of the double-skin steel plates and the confinement effect of the steel composite tube on the internal concrete, a theoretical calculation formula of the axial compression bearing capacity of DSCCT wall was proposed. The proposed calculation values were in good agreement with the test values, and had higher calculation accuracy and stability in predicting the axial compression bearing capacity of DSCCT walls.

Quasi-static experimental study on precast concrete columns reinforced with bundled rebars

Bundled reinforcement is an alternative approach to improve the installation efficiency and structural integrity of precast concrete structures. With higher strength and lighter weight compared with steel bars, basalt fiber reinforced polymer (BFRP) bar is an attractive candidate material for concrete structures. Low-cyclic reversed loading tests on four precast concrete columns reinforced with different arrangements of longitudinal bars were conducted in this paper. The test specimens included singly arranged steel bars (S12-1P, S20-1P), three-bar bundled steel bars (S12-3P), and three-bar bundled hybrid BFRP bars/steel bars (S10/B13-3P). The test results showed that using bundled reinforcement in precast concrete columns could delay the yielding of longitudinal steel bars. Specimens S12-3P and S20-1P not only maintained the inherent bearing capacity and stiffness, but also demonstrated improved deformability of 18.1% and 6.9%, respectively, compared to the conventional precast column S12-1P. S10/B13-3P showed a 5.5% increase in peak load and a 9.1% increase in displacement ductility, which is expected to result in better seismic performance compared to that of the conventional columns. The corresponding repairable limits (based on the drift ratios) for S12-1P, S20-1P, and S10/B13-3P were 2.6%, 2.9% and 4.5%, respectively. In addition, the use of bundled bars could result in a wider curvature concentrated distribution zone, thereby increasing the plastic hinge length and providing a larger deformation capacity with the same peak curvature.

Experimental and analytical study of RC beams strengthened with prestressed near-surface mounted 7075 aluminum alloy bars

Recently developed high-strength aluminum alloys (AA) have great potentials for strengthening and repairing RC structures because of their merits in high strength-to-weight ratio, high ductility, and inherently corrosion-resistant behaviors. However, few studies have been conducted on taking advantage of AA bars for rehabilitation. This study was therefore carried out to reveal the feasibility of 7075 AA bars on near-surface mounted (NSM) applications for flexural strengthening of reinforced concrete (RC) beams. Experiments of four-point flexural tests were presented to assess the performance of NSM AA bar strengthened beams through eight concrete beams, including a control specimen without strengthening, a specimen strengthened by conventional basalt fiber reinforced polymer (BFRP) bars served as reference, and other six ones using NSM AA strengthening technique with various prestress level and bar arrangement. Results indicate that the application of the strengthening system was able to prevent premature debonding failure and increase the load-bearing capacity by up to 102.1%, but reduced the deformability. In addition, an analytical model for capturing the load–deflection behavior of various strengthening schemes was developed. Good agreements between the results from observations and predictions validated the proposed model, suggesting its potential for guiding the design of the AA strengthening schemes.

Effect of crack control approaches around opening on out-of-plane flexural response of walls

ABSTRACT This study aimed to investigate the effect of different crack-control devices at the re-entrant corners of openings on the out-of-plane flexural performance of reinforced concrete walls. The conventional diagonal bar arrangement, stress dispersion shell plate, and crack-control strip were arranged at each corner of the opening to control the localized diagonal tension cracks at the re-entrants. Four wall specimens with window openings were tested under constant axial loads and cyclic out-of-plane lateral loads. The actual cover thickness was considered in the prediction of the flexural strength of the walls. The out-of-plane flexural lateral load – lateral displacement response of the walls was not dependent on the crack-control devices but was appreciably affected by the cover thickness. An increase in the cover thickness leads to a decrease in the lateral load capacity and ductility. The out-of-plane moment capacity of walls could be conservatively assessed by a conventional flexural analysis procedure, such as the equivalent stress block for reinforced concrete structures, regardless of the consideration of crack-control devices.