Effective Cross-sectional Area Research Articles

Modification in airfoil’s tonal noise using periodic suction-blowing excitation

This paper examines the modifications in the flow and sound fields due to the application of a periodic suction-blowing excitation strip on the top and bottom surfaces of a NACA0012 airfoil. The flow and sound fields have been directly computed (DNS approach) by solving unsteady, two-dimensional compressible Navier–Stokes equations using physical dispersion relation preserving schemes. The flow approaches the airfoil at a Reynolds number of 5000 and 5o angle of attack. In the no-excitation case, the sound is mainly created by the lift and drag dipole equivalent sources associated with vortex shedding. However, the application of suction-blowing excitation results in two additional sound sources: monopole-equivalent sound sources due to fluid movement in and out of the airfoil surface and the drag dipole-equivalent sound sources due to periodic change in the airfoil’s effective cross-sectional area. The combined effects of these sound sources result in significant mitigation of sound on the suction side of the airfoil. The excitation amplitude and forcing frequency effects on sound field modifications have been studied in depth. Beats of sound have been observed when the forcing frequency is close to the excitation frequency.

Ultimate strength and design of CFDST columns with intermittent welded plate stiffeners

This study conducts an experimental investigation and formulates a finite element model and design equation to determine the ultimate strength of concrete-filled double-skin tubular (CFDST) short columns. These columns are equipped with intermittent welded plate stiffeners, and the welding is performed on the inner surface of the outer tube through pre-drilled holes at intervals of 10 t, 20 t, 30 t, and 40 t, where “t” represents the thickness of the outer tube. The study investigates the behaviour of the CFDST column influenced by the presence of plate stiffeners, determines the axial strength of eighteen CFDST specimens and discusses the load-displacement curve, deformation and ultimate strength. The findings demonstrated that the ultimate load of the plate-stiffened CFDST columns is between 24% and 42% higher than the unstiffened CFDST columns. The plate-stiffened CFDST columns also exhibited higher ultimate strength at the smallest weld spacing of 10 t. The experimental results showed that the plate stiffeners influenced the distribution of the internal forces, which changed the effective confinement area of the concrete. The investigated force distribution provides a fundamental theoretical basis for computing the confinement area for the finite element model (FEM) and design model. This study developed a verified nonlinear FEM that employed ABAQUS to replicate the behaviour of the plate-stiffened CFDST columns. Finally, this study proposes a new design model that considers the effective cross-sectional area of the concrete confined in CFDST columns with intermittent welded plate stiffeners. The strength predictions of the plate-stiffened CFDST columns were accurate compared to the experimental results.

Confinement-based design and behaviour of concrete-filled stiffened steel tubular square slender columns

This paper presents the details, analysis and results of an investigation into the compressive behaviour of concrete-filled stiffened steel tubular (CFSST) slender columns. These are members comprising an outer steel section with longitudinal stiffeners welded to the interior surface. A finite element (FE) model was developed and validated. An improvement in ultimate strength compared to conventional concrete-filled steel tubular column has been found due to the presence of stiffeners that reduce the width-to-thickness ratio of the steel tube, which in turn increases the effective cross-sectional area of the steel tube. Moreover, it was found that stiffeners increase the lateral confining pressure on the concrete. FE modelling was then employed to conduct a thorough parametric study to investigate the influence of a wide range of parameters. These included the slenderness ratio, concrete compressive strength, as well as the geometry and details of the stiffeners. Both medium-length and long CFSST columns, classified on the basis of slenderness ratio, were carefully studied and discussed, as well as their inherent differences. The strengths predicted from the FE simulations were compared with the design strengths obtained from various international design codes, and it was shown that the design expressions provide very conservative capacity predictions. Accordingly, a new three-stage confinement-based design model was proposed, which takes into account different confining mechanisms of columns based on their slenderness ratio. It is illustrated that this model provides a very accurate prediction of the square CFSST slender columns, and captures the key behavioural characteristics.

Unveiling Invariant Optical Properties of Dielectric Meta-Atoms.

The phase-shift, transmittance, and polarization properties of meta-atoms are investigated, motivated by their use as building blocks of metasurfaces used in metalenses, holograms, and beam shaping. We studied dielectric nanorod meta-atoms of several geometries, which included cylinders, triangles, squares, hexagons, octagons, and truncated cones. By analyzing light propagation through these meta-atoms for three different wavelengths (632.8, 545, and 50 nm), we show that the phase-shift introduced is independent of their cross-section shape, contrary to the expected behavior. Additionally, we show that the polarization response is independent of the shape and that the transmittance is partially shape-independent. We identify a novel dependence of phase-shift on the effective cross-sectional area of meta-atoms. These meta-atom optical properties are independent of its shape if its geometry has a C3 or larger rotational symmetry. This optical invariance has significant implications for the topological optimization of flat optics.

Delayed Detached-Eddy Simulations of Rough-Wall Turbulent Reactive Flows in a Supersonic Combustor

Reactive delayed detached-eddy simulations (DDESs) of hydrogen injection into a confined transverse supersonic flow of vitiated air are conducted. The corresponding conditions were studied in the LAPCAT-II combustor, which—due to thermal coating—exhibits non-negligible wall roughness. Its effects are taken into account with the equivalent sand-grain roughness model, and, to the best of the authors’ knowledge, it is the first time that this modeling framework is considered within the DDES framework to simulate turbulent reactive flows. Two operating conditions are considered, which differ in the value of the momentum ratio between the hydrogen and vitiated air inlet streams, thus leading to two distinct values of the operating equivalence ratio (ER). For its smallest value, smooth combustion is subject to a preliminary thermal runaway period, while for its largest value, combustion is more strongly intertwined with shock wave dynamics and boundary-layer separation. Since it features large subsonic regions, which are characteristic of situations close to thermal choking, the latter is referred to as the sudden or partially choked combustion mode. Computational results are assessed through comparisons with available experimental data for both operating conditions. The main mechanism through which wall roughness alters the combustion development lies in the reduction of the effective cross-sectional area that is induced by boundary-layer thickening. For the largest ER value, DDES conducted with the sand-grain roughness model does recover the partially choked combustion mode, while smooth wall (i.e., standard) DDES does not.

High-temperature oxidation degradation mechanism of novel Zr-containing SiC fibers

The application of ceramics matrix composites (CMCs) in extreme environments is often dictated by the oxidation resistance of SiC fibers, which are frequently utilized as the reinforcement of CMCs. Introducing heterogeneous elements into SiC fibers is one effective way to enhance their oxidation resistance. In this work, the chemical composition, microstructural evolution, phase evolutions, and tensile strength of the newly developed Zr-containing Zeralon 200™ SiC fiber oxidation-treated at elevated temperatures in an air atmosphere for 5 h was investigated in depth, using transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscope (EDS), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and Raman spectroscopy (Raman). Results indicate that the Zeralon 200™ SiC fiber has a significantly better oxidation resistance than some typical non-heterogeneous element SiC fibers. ZrSiO4 was found to generate in the fiber after oxidation treatment at 1100 °C for 5 h. The specific generation mechanism of ZrSiO4 and its oxidation resistance mechanism in the Zeralon 200™ SiC fiber were revealed. Meanwhile, the degradation mechanism of the tensile strength of Zeralon 200™ SiC fiber was discussed in detail. In short, the decline in the tensile strength of Zeralon 200™ SiC fiber can be ascribed to the decomposition of the amorphous phase SiCxOy, the enlargement of defects within the fiber bulk, and the decrease in the effective load-bearing cross-sectional area of the fiber caused by extensive oxidation, sequentially occurring at various elevated temperatures.

Influence of Narrow Titanium Dental Implant Diameter on Fatigue Behavior: A Comparison between Unitary and Splinted Implants.

Background: Scientific literature lacks strong support for using narrow diameter implants (NDI) in high masticatory force areas, especially in molars. Implant splinting in cases of multiple missing teeth reduces lateral forces, improves force distribution, and minimizes stress on implants. However, no studies have evaluated the fatigue load resistance of unitary or splinted implants. Methods: This in vitro study compares five groups of new metal alloy implants, including unitary and splinted implants with varying diameters. Mechanical characterization was assessed using a BIONIX 370 testing machine (MTS, Minneapolis, MN, USA) according to ISO 14801. For each of the five study sample groups, (n = 5) specimens underwent monotonic uniaxial compression at break testing and (n = 15) cyclic loading to determine the maximum force (Fmax) and the fatigue life (LF) values. Scanning electron microscopy (SEM) was employed for the fractographic analysis of the fractured samples. Results: The Fmax values for unitary samples ranged from 196 N to 246 N, whereas the two-splinted samples displayed significantly higher values, ranging from 2439 N to 3796 N. Similarly, the LF values for unitary samples ranged from 118 N to 230 N, while the two-splinted samples exhibited notably higher values, ranging from 488 N to 759 N. Conclusions: The observed resistance difference between sample groups in terms of Fmax and LF may be due to variations in effective cross-sectional area, determined by implant diameter and number. Additionally, this disparity may indicate a potential stiffening effect resulting from the splinting process. These findings have significant implications for dental clinical practice, suggesting the potential use of splinted sets of small-sized NDI as replacements for posterior dentition (premolars and molars) in cases of alveolar bone ridge deficiencies.

Effect of glycerol incorporation on the liquid crystal structure of sucrose fatty acid ester in aqueous solution

A series of homogeneous samples with high sugar-surfactant content (sucrose fatty acid ester/water and sucrose fatty acid ester/glycerol/water systems) were prepared with well-controlled processes and investigated by DSC, polarized microscopy, X-ray scattering and rheology. Meanwhile the accuracy of the preparation process is confirmed gas chromatography. The polarized microscopy indicates that the ordering degree of the network structure composed of the liquid crystals may be reduced by the glycerol addition. The results of DSC revealed that 50% glycerol solution could significantly inhibit the crystallization of sucrose fatty acid ester and resulted in a significant widening of the temperature interval for the transformation of the liquid crystal phase into the gel phase. In order to further evaluate the effect of glycerol molecules versus water molecules on the liquid crystal structure of sucrose fatty acid ester, we comparatively analyzed the X-ray scattering data from two perspectives: the mass fraction and molar fraction. It was found that 50% glycerol solution could inhibit the crystallization of sucrose fatty acid ester through changing the water-head group interaction of surfactant, facilitates the integration of sucrose fatty acid ester with different alkyl chain length and may reduce the regularity of liquid crystal, both from the perspective of surfactant mass and molar fraction. Furthermore, the addition of 50% glycerol (w/w) does not significantly impede the liquid crystal formation of sucrose fatty acid ester in aqueous solution. However, from the perspective of surfactant mass fraction, glycerol incorporation could reduce the effective cross-sectional areas of the hydrophilic part of sucrose fatty acid ester in aqueous solution and induce the phase transition of hexagonal liquid crystals to aggregates with less positive curvature, while an opposite tendency could be obtained from the perspective of surfactant molar fraction. The conclusions are also confirmed by subsequent rheological test. Moreover, the results of rheological measurements reveals that the interactions among cylindrical units of the hexagonal liquid crystalline phase become weaker and the surfactant molecules aggregate more loosely in the cylindrical unit with the glycerol incorporation. Moreover, the above-mentioned influence of glycerol on the liquid crystal structure of sucrose fatty acid ester in aqueous solution would be similar but more prominent from the perspective of the molar fraction.

Study on Cracking Causes of One 500 kV SSY Type Equipment Clamp

One SSY type equipment clamp serviced in a 500 kV station was found to be cracked. In this paper, the crcaked cause and mechanism is investigated by means of macroscopic morphology observation, fracture surface morphology observation, X-ray digital detection, metallographic observation. The results indicated that the main reason for the fracture of the equipment clamp this time is that the terminal board is a cast part, which contains a large number of casting defects such as porosity and shrinkage, resulting in a decrease in its effective cross-sectional area and load-bearing capacity. In addition, insufficient modification treatment of the terminal board led to insufficient toughness due to needle or rod-shaped eutectic silicon in the organization. Finally, under the combined action of dynamic load and self weight caused by the swinging of the wire in the wind, the terminal board was brittle fractured along the bolt hole with obvious stress concentration effect.

Functional interaction of aortic valve and ascending aorta in patients after valve-sparing procedures

Pressure recovery (PR) is essential part of the post stenotic fluid mechanics and depends on the ratio of EOA/AA, the effective aortic valve orifice area (EOA) and aortic cross-sectional area (AA). In patients with advanced ascending aortic aneurysm and mildly diseased aortic valves, the effect of AA on pressure recovery and corresponding functional aortic valve opening area (ELCO) was evaluated before and after valve-sparing surgery (Dacron graft implantation). 66 Patients with ascending aortic aneurysm (mean aortic diameter 57 +/− 10 mm) and aortic valve-sparing surgery (32 reimplantation technique (David), 34 remodeling technique (Yacoub)) were routinely investigated by Doppler echocardiography. Dacron graft with a diameter between 26 and 34 mm were implanted. EOA was significantly declined after surgery (3.4 +/− 0.8 vs. 2.6 +/− 0.9cm2; p < 0.001). Insertion of Dacron prosthesis resulted in a significant reduction of AA (26.7 +/− 10.2 vs. 6.8 +/− 1.1cm2; p < 0.001) with increased ratio of EOA/AA (0.14 +/− 0.05 vs. 0.40 +/− 0.1; p < 0.001) and pressure recovery index (PRI; 0.24 +/− 0.08 vs. 0.44 +/− 0.06; p < 0.0001). Despite reduction of EOA, ELCO (= EOA corrected for PR) increased from 4.0 +/− 1.1 to 5.0 +/− 3.1cm2 (p < 0.01) with reduction in transvalvular LV stroke work (1005 +/− 814 to 351 +/− 407 mmHg × ml, p < 0.001) after surgery. These effects were significantly better in patients with Yacoub technique than with the David operation. The hemodynamic findings demonstrate a valve-vessel interaction almost entirely caused by a marked reduction in the ascending AA with significant PR gain. The greater hemodynamic benefit of the Yacoub technique due to higher EOA values compared to the David technique was evident and may be of clinical relevance.

Dynamic modeling and optimization for powertrain shake characteristics of electric powertrain system with hydraulic engine mounts

Poor designed powertrain mounting system can lead to severe resonance when road excitation frequency is consistent with the natural frequency of the powertrain mounting system, which results in vertical vibration of the vehicle. In addition, double-layer vibration isolation and hydraulic engine mount (HEM) are widely used for vibration attenuation of electric powertrain. This paper focuses on the vertical vibration of electric vehicles under road excitation. An analytic model of powertrain shake characteristics considering the amplitude-frequency dependent nonlinearity of HEMs is established. Furthermore, the proposed nonlinear model is experimentally validated through rigid body modal test of the powertrain. Numerical simulation is carried out to investigate the influence of HEM parameters on powertrain shake characteristics. Simulation results demonstrate that the effective pumping area, upper chamber stiffness and inertia track effective cross-sectional area, and length of HEM have obvious impact on powertrain shake characteristics. Under the premise of ensuring vibration isolation performance under other conditions, optimization of the above HEM parameters can reduce peak value of car body vibration under road excitation and thus improve ride comfort.

Judd-Ofelt analysis and luminescence properties of newly fabricated Dy3+ infused calcium sulfo-phospho-borate glasses for photonics applications

In this paper, a new series Dy3+ doped calcium sulfo-phospho-borate (CSPB:xDy) glass system was fabricated via melt quenching approach. The non-crystalline state of the fabricated glass was verified by XRD measurements. Besides, the optical band gaps, refractive indices alongside Judd-Ofelt quantities of the CSPB:xDy glass host were computed to ascertain their radiative potentials. The glasses, under 348 nm excitation light disclosed two prominent emission bands at 480 nm (4F9/2→6H15/2) and 574 nm (4F9/2→6H13/2) wherein the peaks intensity increases up to 0.8 mol% of Dy3+ and thereafter, diminish due to dipole–dipole interaction. Moreover, the potential usage of these glasses were shown through radiative and colorimetric analyses. The effective quantum efficiency (85.81 %), branching ratio (71 %) and emission cross-sectional area (12.78 × 10−22 cm2) attained for CSBP0.8Dy glass endorsed it practicability in solid state light emitting device applications such as w-LEDs and display devices.

A Correction Method for the Measurement of Frequency-Dependent Attenuation Coefficient With Curved Surface Specimens Using Normal Contact Transducer

The ultrasonic pulse-echo technique has been widely employed for the measurement of the frequency-dependent attenuation coefficient in polycrystalline metals. However, the nonuniform thickness of the coupling layer between the transducer piston and the curved surface is inevitable for curved specimens, resulting in a significant overestimation. In addition, the curved surface also affects the diffraction loss caused by the divergence and convergence of ultrasonic beams during the propagation path. In this study, a correction method is proposed for the experimental calculation of the frequency-dependent attenuation with the curved surface components using a contact transducer. First, with the analysis of the nonuniform coupling layer created by the curved surface and transducer piston, the integral over the effective cross-sectional area is introduced to determine the reflection coefficient. Second, an equivalent rectangular transducer sound field model is proposed to calculate the diffraction loss for different curvatures and propagation distances based on the multi-Gaussian beam (MGB) theory. Then, a correction model is established to compensate for the deviation caused by the curved surfaces. To verify the feasibility of the proposed method, two cylindrical bars and five blanks with different curvatures were designed. The experimental results show that the proposed correction method can effectively eliminate the deviation caused by the curved surface and improve the stability of measurement. With the correction, the variation of the attenuation spectrum for the curved specimens is reduced by approximately 5%. This facilitates researchers to better develop and use frequency-dependent attenuation coefficients of materials for further applications.

Concrete-filled cold-formed steel (CF-CFS) built-up columns subjected to elevated temperatures: Test and design

This paper evaluates the behaviour of an innovative type of lightweight concrete-filled cold-formed steel (CF-CFS) built-up composite long column in the fire. Twelve fire resistance tests were performed on CF-CFS columns. The experimental results were discussed, including test observations, buckling modes characterization, vertical and horizontal deformations, temperature evolution, and fire resistance in terms of load-bearing capacity. A finite element modelling approach was developed and validated against the test results. Then, the experimental data were compared against analytical predictions following EN1994-1-2, assessing the suitability of existing design methodologies. For this purpose, two analytical approaches available in EN1994-1-2 were used, including Annex-H and the general method (Clause 4.3.5.1). The results showed that the fire resistance prediction according to EN1994-1-2, Annex H, was remarkably conservative. However, the general method of EN1994-1-2 (Clause 4.3.5.1) provided unsafe predictions. Therefore, a modification to the analytical prediction of EN1994-1-2 (Clause 4.3.5.1) was applied to account for the CFS effective cross-sectional area, buckling curve d, and experimental degradation of CFS mechanical properties at elevated temperatures, resulting in an excellent agreement with the test results. Reliability analysis and safety evaluation criteria proposed by Kruppa were also carried out to assess the suitability of the design methodologies.

Experimental and theoretical research on the debrining process in sediments for a gas storage salt cavern

The sediments account for a large part of the total mined volume of the cavern in high impurity salt mines. This paper was aimed at the scientific problem of gas storage in the pore space of the sediments, and expanded the storage capacity of salt cavern in high impurity salt mines. Debrining in the mined space of salt caverns (contained sediments) is a vital step to complete the gas storage. To experimentally observe the debrining process, debrining experiments are carried out using a self-developed experimental device. The debrining process can be divided into four typical stages, e.g., rapid increase of injection gas pressure, discharging the upper brine, i.e. the brine free of sediments, discharging the brine in sediments, and rapid decrease of injection gas pressure. A mathematical model is proposed for calculating debrining parameters of a salt cavern including sediments based on the pressure equilibrium principle at the gas-brine interface. A numerical method is established for calculating the total debrining time of irregular salt caverns including sediments. The effective cross-sectional area of debrining process is calculated by using the porosity of the sediments. A linear function of the porosity of the transition zone of the sediment surface is put forward. Therefore, the porosity of the upper brine space can gradually transition to the sediments, avoiding the error of sudden increase of the gas-brine interface and debrining rate, which is consistent with the practical debrining process. The porosity of sediments is considered to be a decaying exponential function of depth based on the accumulation of sediment particles. The cross-sectional area at any depth can be obtained through the interpolation of the sonar scanning data. The Jianghan salt cavern is selected for the applications of the proposed model, and the descending speed and depth of the gas-brine interface, and injection gas pressure with debrining time are analyzed. Results show that the greater the debrining rate, the shorter the time to reach the final sediment surface. The descending speed of the gas-brine interface shows a U-shaped curve, which is significantly affected by the cavern shape and porosity of sediments. The increment of the debrining rate has little effect on the ultimate injection gas pressure but has a significant effect on the increasing rate of injection gas pressure. These results can provide a reference for enhancing gas storage by using the sediment pore space of the mined volume and thereby expanding the effective gas storage volume of salt caverns.

Experimental Study on Denitration Transformation of CFB Boiler Burning Fujian Anthracite

Two 75 t/h medium-temperature separated circulating fluidized bed boilers burning Fujian anthracite were upgraded with low NOx combustion (LNC). By reducing the effective cross-sectional area of the air distributor (from 13.43 m2 to 11.38 m2), improving the secondary air rate (from 40% to 45%), adjusting the secondary air supply method (adding a layer of upper secondary air, raising the height of the lower secondary air nozzle (0.4 m), and increasing the secondary air speed (from 48 m/s to 54 m/s), the reform of low nitrogen combustion was carried out. The transformation achieved remarkable results, i.e., the original NOx emission concentration can be controlled between 140–160 mg/m3 after the transformation, and the lowest value is below 120 mg/m3.

Scalability of U-Shape Magnetic Nanoparticles-Based Microreactor–Lipase-Catalyzed Preparative Scale Kinetic Resolutions of Drug-like Fragments

The production of active pharmaceutical ingredients (APIs) and fine chemicals is accelerating due to the advent of novel microreactors and new materials for immobilizing customized biocatalysts that permit long-term use in continuous-flow reactors. This work studied the scalability of a tunable U-shape magnetic nanoparticles (MNPs)-based microreactor. The reactor consisted of a polytetrafluoroethylene tube (PTFE) of various inner diameters (ID = 0.75 mm, 1.50 mm, or 2.15 mm) and six movable permanent magnets positioned under the tube to create reaction chambers allowing the fluid reaction mixture to flow through and above the enzyme-loaded MNPs anchored by permanent magnets. The microreactors with various tube sizes and MNP capacities were tested with the preparative scale kinetic resolution of the drug-like alcohols 4-(3,4-dihydroisoquinolin-2(1H)-yl)butan-2-ol (±)-1a and 4-(3,4-dihydroquinolin-1(2H)-yl)butan-2-ol (±)-1b, utilizing Lipase B from Candida antarctica immobilized covalently onto MNPs, leading to highly enantioenriched products [(R)-2a,b and (S)-1a,b]. The results in the U-shape MNP flow reactor were compared with reactions in the batch mode with CaLB-MNPs using similar conditions. Of the three different systems, the one with ID = 1.50 mm showed the best balance between the maximum loading capacity of biocatalysts in the reactor and the most effective cross-section area. The results showed that this U-shaped tubular microreactor might be a simple and flexible instrument for many processes in biocatalysis, providing an easy-to-set-up alternative to existing techniques.

Assessment of the reliability of bent reinforced concrete elements under corrosive effects

The main problem of reducing the reliability and durability of reinforced concrete structures is the corrosion of concrete and reinforcement of operated buildings and structures. Calculation of structures made of reinforced concrete, taking into account environmental influences, is complicated by the stochastic nature of the parameters of corrosion processes. The conducted studies are aimed at solving the problem of improving the methodology of the probabilistic approach to the calculation of corrosion-damaged reinforced concrete elements. The article considers a probabilistic assessment of reliability for the most common bent reinforced concrete elements, taking into account corrosive wear and the time factor. The modeling of the effect of corrosion processes on the stress-strain state of a reinforced concrete element was carried out using the concrete deformation diagram, which takes into account the decrease in strength characteristics with an increase in the concentration of an aggressive medium in concrete. The scheme of propagation of an aggressive environment in concrete is adopted according to the diffuse front method. Corrosion processes in reinforcement were taken into account by reducing the effective cross-sectional area of reinforcing bars. The change in the properties of steel (its embrittlement) with an increase in the concentration of an aggressive medium was not taken into account. Reinforcement corrosion was simulated after the incubation period, after the concentration of the aggressive medium on the surface of the reinforcing bars reached a critical value. The determination of the moment of the onset of the limit state in the element was carried out on the basis of a nonlinear deformation model at each point of the section of the element to achieve the maximum possible tensile or compression strains in concrete and reinforcement. To solve the problem of reliability assessment, the method of statistical modeling implemented in a specialized software package was used. To apply this method, according to previous studies, the probabilistic parameters of all random variables were taken: mathematical expectation and standard deviation. Based on the results of the reliability assessment, graphs of the decrease in the reliability of a bent reinforced concrete element from the time of exposure to an aggressive environment were obtained.

Finite element analysis of bond behavior in corroded reinforced concrete beams: State-of-the-art

The article conducts a comprehensive examination of various aspects related to rebar corrosion, encompassing the corrosion mechanism, its implications on design criteria, the modeling of bond interfaces under both corroded and non-corroded conditions, and the modeling of reinforced concrete (RC) beams affected by corrosion, employing both empirical and analytical methodologies. The initial stages of corrosion instigate a gradual transformation of rebar into rust. One notable consequence of reinforcement corrosion is the generation of expansive pressure, leading to concrete cracking, spalling, and detachment of the concrete cover. Additionally, it diminishes the effective cross sectional area of the rebar, ultimately resulting in a decline in the concrete's bond strength and gradual structural deterioration. Ultimately, continuous corrosion can lead to a complete loss of bond between the concrete and rebar, representing the most severe form of damage attributable to corrosion. This poses a critical threat, particularly in cases where the beam functions as an unreinforced structure, potentially culminating in sudden structural failure. This paper primarily underscores the utilization of the Finite Element Method (FEM) for evaluating the impact of bond deterioration between concrete and reinforcement caused by corrosion. The paper effectively employs this technique to predict and analyze the structural damage in corroded RC beam specimens.

Gradual Deterioration Behavior of the Load-Bearing Strength of Main Cable Wires in a Suspension Bridge

The main cable is the primary load-bearing component of a long-span multi-tower suspension bridge. The interaction between a dead load, vehicle load, wind load, and the corrosion environment leads the main cable wire to exhibit tribo-corrosion-fatigue behaviors. This behavior causes wire wear and deterioration, as well as a reduction in the effective cross-sectional area. This leads to the gradual deterioration of the wire’s load-bearing strength and seriously affects the load-bearing safety of the main cable. In order to ensure the safety of suspension bridges, it is critical to investigate the gradual deterioration behavior of the main cable wire’s load-bearing strength. A wire tribo-corrosion-fatigue test rig was established to test the wire under different friction pairs (saddle groove or parallel wires). The cross-sectional failure area of the wire with different pairs was obtained by super-depth electron microscopy and calculation. The damage degree evolution model and the deterioration model of the wire load-bearing strength were established by combining the theory of damage mechanics and the finite element method. The results show that, as contact and fatigue loads increase, so does the cross-sectional failure area of the fatigue steel wire. The fatigue wire’s damage degree has a good quadratic function relationship with fatigue cycles. The damage degree of the wire increases and the load-bearing strength decreases with increasing contact load and fatigue load. The load-bearing strength of the wire changes little at the beginning and decreases with increasing fatigue cycles. The results have fundamental significance for the life prediction of the main cable wires of suspension bridges.