Parallel Steel Research Articles

Study on Multi-Crack Damage Evolution and Fatigue Life of Corroded Steel Wires Inside In-Service Bridge Suspenders

The parallel steel wires used in arch bridge suspenders experience random corrosion damage on their surfaces during service. Corrosion damage, including micro-cracks, pitting, and a combination of both, leads to significant stress concentration under axial loading, which affects the performance of the steel wires. The change in the stress field caused by surface damage alters the stress intensity factor at the crack tip, and the presence of adjacent crack tips significantly amplifies the stress intensity factor, thereby accelerating crack propagation. The development of small surface damages in the steel wires is difficult to control and observe through experiments. By utilizing finite element methods for simulation, it is possible to intuitively analyze the crack propagation process, the trend of stress changes at the crack tip, and the interaction between damages. Numerical simulation results based on Paris’ law indicate that corrosion pits have a certain impact on the stress intensity factor at the crack tip. The propagation process of coplanar double cracks is highly sensitive to the initial crack size and the distance between adjacent crack tips. When the crack spacing is less than the crack depth, the stress intensity factor at the adjacent crack tips exhibits significant amplification. Based on this phenomenon, the coplanar double-crack system can be simplified to a complete single crack for analysis. By comparing the fatigue life of the double-crack system with that of the equivalent single crack, the effectiveness of the simplification rule has been validated.

Orientation effect of chopped steel fiber on tribological performance of very low metallic brake pads: An interface study

The orientation effect of chopped tiny steel fibres (length < 3 mm; diameter < 200 µm) in brake pads parallel (NAPA) to the sliding direction is studied using two different methods. Inverting the specimen during testing yields fibre perpendicular (NAPE) to the sliding direction, which is compared to commercial random-oriented fibre pads (NARA). The orientation coefficient value of near unity is achieved only in NAPA. NAPA and NAPE have a lower density than NARA by 13.2% due to less than 54.55% of steel fibres in the formulation. More and larger plateaus stabilized friction in NARA, utilising the elongation properties of parallel steel fibres, than in NAPE, which produced only tiny plateaus. However, the wear resistance decreases when the sliding path or direction changes from parallel to perpendicular. The measurement of thickness loss is misleading during wear because of the swelling effect, and hence energy requirements are considered. The energy required to wear 1 cc of specimen in the NAPE is 23.78% greater than that in the NAPA, and hence wear resistance is better. Adhesion followed by delamination at elevated temperatures are the dominant wear mechanisms in NAPA, whereas abrasion is dominant in NAPE. Thus, semi-metallic performance can be obtained in a very low metallic pad by orienting these fibres.

Development of a pressure-, velocity-, and acceleration-dependent phenomenological friction model using experimental data of sliding tests between 11 polymers and stainless steel

This paper experimentally investigates the frictional behavior between stainless steel and 11 polymers. Particularly, the dependence of the friction coefficient on the sliding velocity, pressure, and acceleration is quantified. The novelty of this work lies in quantifying the acceleration-dependent nature of friction, correlating it to the well-documented Stick-Slip effect. The experimental setup consisted of two parallel stiff steel beams, one above the other, with a separation of 95 mm, and steel surfaces welded at the inner sides for sliding the polymers. Cylindrical polymer pads were placed between the stainless-steel surfaces and connected to a dynamic actuator to apply the displacement protocol. The protocol consisted of consecutive nominally constant-velocity ramp cycles covering velocities from 1 mm/s to 300 mm/s (with 20 mm/s increments). An additional vertical force was applied with a hydraulic actuator to reach nominal pressures in the polymers between 5 and 80 MPa. The results showed that the friction coefficient depends on the velocity, pressure, and acceleration of the motion, and a phenomenological model on these three variables is proposed. The velocity dependence can be represented through a logarithmic relationship, while the pressure dependence is through an exponential decay relationship. The acceleration dependence was represented through a linear relationship, which could capture the stick-slip effect. Overall, this work contributes to a better understanding of friction for seismic isolation systems. Since friction is the main source of energy dissipation in such structures, the proposed model will allow a higher accuracy in predicting variables of interest during the dynamic analyses of seismically isolated structures with frictional systems.

Fatigue life prediction of corroded hangers with parallel steel wire in a network arch bridge under vehicle-bridge interaction based on a novel noniterative simplified method

Fatigue damage is a main concern during the life-cycle maintenance of bridges with corroded hangers under vehicle-bridge interaction (VBI). In this study, a novel noniterative simplified method for VBI is proposed to analyze the responses of hangers in a network arch bridge, considering the effects of vehicle types, driving lanes, and road surface roughness. Furthermore, the fatigue life of corroded hangers is investigated, considering the actual traffic flow and uneven distribution of stress in the hanger’s cross-section. The results show that longitudinal and transverse bending moments of the hanger significantly affect the stress of steel wires in one hanger but have limited influence on stress amplitudes. The fatigue lives of steel wires are considerably reduced when subjected to both uniform and pitting corrosion. The fatigue life of steel wires is reduced under deteriorating road surface conditions. Moreover, as the fatigue life of steel wires in the hangers declines, the variations in fatigue life among individual steel wires within a single hanger gradually decrease. Consequently, this trend leads to a heightened likelihood of continuous wire breakage.

Reliability assessment of bridge hangers based on fault tree with response surface

Bridge hangers play a crucial role in transmitting forces and supporting bridge structures. The condition of these hangers directly impacts the overall safety of the bridge. However, they are susceptible to fatigue failure due to cyclic loads like wind and vehicle traffic. Therefore, evaluating the fatigue performance of bridge hangers is vital. Typically made up of multiple parallel steel wires, the failure of even one wire can affect the fatigue performance of the entire hanger. This underscores the importance of considering the individual components’ impact on the system as a whole. This study presents a time-dependent reliability assessment model for bridge hangers based on the S-N curve of steel wire. Additionally, a system-level reliability assessment model is developed using fault tree analysis, taking into account the influence of broken wires and stress redistribution on the hanger system. The model is solved using response surface methodology, and through five numerical simulations, the study examines the effect of key parameters, including the number of broken wires, equivalent structural stress, and total cycles on the system’s reliability.

Tribo-corrosion-fatigue behaviors of the parallel wires of main cable in the suspension bridge

The suspension bridge in service is subjected to the coupling effects of dead load, vehicle load, wind load and corrosive environment. These factors cause the tribo-corrosion-fatigue behaviors of parallel steel wires of main cable, which seriously affect the load-bearing safety of the main cable. Therefore, it is of great significance to investigate tribo-corrosion-fatigue behaviors of steel wires and the saddle materials. The self-made test rig was developed to carry out tribo-corrosion-fatigue tests between the parallel steel wires, and between the steel wire and saddle groove. Tribo-corrosion-fatigue behaviors (friction coefficient, wear profile, failure area, wear mechanism and wear coefficient) of main cable wires was revealed by high speed digital microscope and scanning electron microscope. The results show that the friction coefficient shows a trend of rapid increase – decrease – increase – stabilization. It decreases with increasing contact load as compared to an increase with increasing fatigue load. The wear width and depth both increase nearly linearly with increasing cycles, while the failure area increases nearly parabolically. As the contact load and fatigue load increase, the wear width and depth increase, and the corrosion of wear area is more obvious. The wear coefficient decreases first and then increases with the increase of cycles. The wear mechanisms are mainly adhesive wear, abrasive wear, fatigue wear and corrosion wear. The increase of contact load and fatigue load promotes the wear deterioration behaviors of cable wires. The results have fundamental significance to ensure the load-bearing safety of the main cable and improve the service safety of the suspension bridge.

The uncorroded-part fallacy

This paper deals with the collapse load of corroded parallel steel units, such as sets of corroded strands alone, or embedded in a concrete core. It is shown that what is relevant is the distribution of the damage between the units, and not the total area loss due to corrosion. The paper also shows that assuming that the area loss is related to the limit load loss is misleading, and potentially dangerous.

Rapid design for large-scale parallel CFRP cable with multi-source experimental data

With advancements in material properties and reduced costs, carbon fibre reinforced polymer (CFRP) cables are gaining popularity in engineering applications due to their superior strength-to-mass ratio and durability. However, the tensile strength of large-scale parallel CFRP cables remains a critical issue, warranting further research and engineering expertise. To address this issue, this paper proposes a method to rapidly predict and adaptively correct the tensile strength of large-scale parallel CFRP cables using multi-source experimental data and an integrated approach that incorporates Monte Carlo simulations, Neural Network algorithms, and Genetic algorithms. This comprehensive method takes into account the influence of various factors including small-scale material strength and its coefficient of variation, cable length, the number of parallel wires, installation errors, and anchorage errors. Validated by reported experimental data, the method demonstrates its effectiveness in accurately predicting the tensile strength of parallel CFRP cables. Moreover, a design method for large-scale parallel CFRP cables is proposed based on the reliability theory. Lastly, the efficiency and effectiveness of the proposed method are validated through the design and optimization of a cable-stayed bridge featuring a main span of 1984 m, utilising both parallel steel and CFRP cables.

Tensile–Bending–Corrosion Fatigue Analysis of the Parallel Steel Wire Cable in Suspension Bridges

Tensile–Bending–Corrosion Fatigue Analysis of the Parallel Steel Wire Cable in Suspension Bridges

Research on self-leakage flux magnetic identification method of the most dangerous section of parallel wire cable under multi-point broken wire condition

The self-leakage magnetic signal of 37 parallel steel wires was detected by using magnetic signal detection technology and equipment. Based on the theoretical and experimental data, the relationship between the magnetic signal characteristics and the influencing factors was analyzed. The magnetic signal characteristics of multi-point interleaved broken wires are explored. The results show that the characteristics of the self-magnetic flux leakage signal of parallel wires broken are related to the defect parameters of the broken wires. The influence of lifting height on the magnetic signal is less than 3.8 %. The influence rate of the detection angle path is under 8.3 %. By analyzing the measured magnetic signals, a method for identifying the most dangerous cross section is proposed, and this is modified and improved. The maximum identification error of the recognition error is only 5.6 %.

Spatial propagation characteristics of acoustic emission signals in parallel steel wire cables

Accurate spatial propagation characteristics facilitate damage spatial localization, which is crucial for assessing the condition of parallel steel wire cables (PSWC). Existing studies have focused on the longitudinal propagation of acoustic emission (AE) signals, limiting accurate spatial damage assessment. This study comprehensively explored the spatial propagation characteristics of AE signals in PSWC using finite elements and attenuation tests. AE signals propagate hexagonally on the transverse section, with different amplitude attenuation rates at different angles—8% at 0° and 60°, 5 % at 30° and 45°. Additionally, AE signals exhibit oscillatory propagation between different wires in the longitudinal direction. The longitudinal speed (5706 m/s) is approximately 4.2 times faster than the transverse speed (1371 m/s), and the propagation path can be simplified as longitudinal and then transverse, offering valuable guidance for damage localization. The optimum frequency is 150 kHz in the transverse direction and 30 kHz in the longitudinal direction.

Breakage behavior of corn kernels subjected to repeated loadings

Studying the breakage behavior of corn kernels subjected to repeated compressive events, including at low frequency and low strain rate, are important for the development of breakage models for prediction of kernel breakage in handling and processing machines. The main purpose of this study was to identify the breakage behavior and mechanism of weakening of corn kernels under repeated loadings as affected by their moisture content and kernel thickness. Corn kernels at four moisture content levels (8.20%, 11.95%, 16.00%, 20.02%) and in four thickness ranges were subjected to repeated compressive loading between two parallel steel plates in quasi-static regime at a constant loading rate of 2 mm/min (strain rates from 4.7 × 10−3 to 1.0 × 10−2). Conducted experiments allow to observe the different grain breakage patterns, identify the crack initiation and its development, describe the weakening of kernels by changes in the total specific energy, plastic and elastic deformation energies, and the number of loading cycles to break (breakage probability) the kernels. The results indicate that the breakage models describing the damage and weakening of grains in terms of changes in the total and strain energy or changes in the stiffness can be used for understanding the effect of moisture content and thickness on breakage of corn kernels.

Seismic strengthening of existing structures by external steel exoskeletons

The evaluation of the structural safety of existing schools and the planning of their retrofit measures are vital and top priority tasks. This research intends (i) to assess the structural safety of a steel school building in Italy and (ii) to suggest retrofitting measures to improve its seismic resilience. The first section describes and discusses the data collection and the numerical model developed, representative of the existing building. Pushover analyses are then conducted to evaluate the seismic performance of the completed structure. Based on the identified shortcomings, a novel strengthening intervention using 2D parallel steel exoskeletons was developed following a displacement-based step-by-step method. The exoskeleton systems were designed considering the architectural and functional needs of the school building, with the goal of maintaining structural safety while preserving the building’s aesthetics and usability. Lastly, the efficacy of the chosen retrofitting method was verified through non-linear static analysis conducted on the reinforced structure.

Force-Chain Superposition Method for Interface Force Conditions on the Cross Section of Parallel Steel Wire Strands

Force-Chain Superposition Method for Interface Force Conditions on the Cross Section of Parallel Steel Wire Strands

TIME DEPENDENT DEFORMATIONS OF A COUPLED BRIDGE: A CASE STUDY

<p>The bridge's span structure comprises a connected beam designed to support a concrete slab poured over parallel steel supports. Simultaneously, segmental construction, shrinkage, and the flow of concrete play a significant role in stress redistribution over time. The span construction is statically indeterminate due to its connections with the abutments, and temporal deformations occur under additional complex conditions. In this analysis, we employed a calculation model based on the layered finite elements method developed by the authors. This model can be utilized to analyse both statically indeterminate supports and the predicted phased construction method. It accounts for changes in the static system and loading, as well as variations in the layers within the coupled section and the viscous properties of the concrete over time. The calculation analysis results reveal that viscous concrete deformations, combined with different moments of activation of individual segments, have a significant impact on stress redistribution over time. Such intricate analyses are indispensable for ensuring the required safety and cost-effectiveness of the bridge span construction.</p>

Optimization of the Monitoring of Coal Spontaneous Combustion Degree Using a Distributed Fiber Optic Temperature Measurement System: Field Application and Evaluation

Coal spontaneous combustion (CSC) in gob not only leads to wasted resources and casualties, but also produces a lot of waste gas that pollutes the underground environment. Mastering the degree of CSC helps ensure that timely and effective control measures are taken. The real-time and accurate monitoring of temperature, as the primary indicator of the extent of CSC, is difficult due to the harsh and hidden environment of gob, resulting in a reduced ability to anticipate and prevent CSC. In this work, a complete distributed optical fiber temperature sensing system (DTSS) set with strong anti-damage ability was developed. The optical cable is protected by internal parallel steel cables and external protective pipes, which greatly improve the system’s reliability and integrity when used in gob. During its application in the Wangyun Coal Mine, an abnormal temperature rise in gob was discovered in time, and the effect of inhibitor spraying was monitored and evaluated. The degree of CSC in the gob was accurately identified, which shows that the work of coal mining can be targeted. This work is expected to improve early warning capability to prevent the risk of CSC in gob, and has promising applications.

Deep reference autoencoder convolutional neural network for damage identification in parallel steel wire cables

This paper addresses the challenge of overcoming the limited availability of training samples for the damage state of parallel steel wire cables in practical engineering and the difficulty of detecting minor damages. To tackle this issue, we propose an unsupervised deep learning damage identification technique called Deep Reference Autoencoder Convolutional Neural Network (DRACNN) for analyzing the damage state of parallel steel wire cables in bridge engineering. The DRACNN method utilizes multi-dimensional cross-correlation function (CCF) derived from acceleration signals at various health stages as input to train the network structure and obtain optimal parameters. Subsequently, we analyze the layer decomposition to identify neurons in the lowest hidden layer indicating damage. The neuronal change information is then extracted using an Exponentially Weighted Moving Average (EWMA) Control Chart to determine the damage state of the structure. Finally, we present a comprehensive numerical analysis describing the method's flow and network architecture and demonstrate the feasibility of this approach through experiments.

Corrosion Fatigue Assessment of Bridge Cables Based on Equivalent Initial Flaw Size Model

Bridge cables under traffic loads are more prone to failure during the service life due to the corrosion–fatigue coupling effect. In this study, a novel lifespan model based on the equivalent initial flaw size (EIFS) theory is established to analyze the various stages of the lifespan of steel wires. Additionally, a comprehensive corrosion-fatigue lifespan calculation method for parallel steel wire cable is established based on the series–parallel model. A case study of the Runyang Suspension Bridge is conducted to evaluate the evolution of corrosion-fatigue damage in bridge cables during the service life. The results indicate that under the action of corrosion-fatigue, steel wires are more prone to crack initiation, and their fracture toughness is further reduced. In cases where the corrosion level is relatively low, the steel wires of the bridge cables experience no corrosion-fatigue fracture. When the steel wires have initial defects and are subject to corrosion-fatigue conditions, their fracture lifespan is dependent on the severity of the corrosive medium. The reduction in the service life of the cables under the corrosion environment is much greater than that under heavy loads. This research may contribute to the understanding of corrosion-fatigue damage in bridge cables, involving assessment, maintenance, and replacement for bridge cables.

A framework of cable wire failure mode deduction based on Bayesian network

Because of the cable structure comprises many parallel steel wires, the service performance of the cable structure is determined by the performance change of the parallel steel wires. The parallel steel wire will be subjected to cyclic load during the service period, which will reduce its fatigue life and even lead to the parallel steel wire broken. In addition, the corrosion pits may appear on the cable steel wire in corrosion environments, which will affect the fatigue life of parallel steel wires. In other words, the cable steel wire may be corroded and broken during its service life, which will decrease in the reliability of the cable system. In this paper, a component level to system-level fatigue reliability assessment model is proposed with considering parallel steel wire broken, corroded, and broken-corroded coupling based on the Bayesian network. Specially, the S-N curve considering the broken parallel steel wire is established based on the traditional S-N curve. In addition, the S-N curve for parallel steel wire corrosion is established with the influence of the corrosive environment in mind. Furthermore, the service state of each parallel steel wire, i.e., the failure probability of each parallel steel wire, can be calculated by using a Bayesian network. Finally, the five numerical simulation studies are used to validate the proposed model’s effectiveness and the effects of the number of broken parallel steel wires and the number of corrosion parallel steel wires on the fatigue reliability of cable systems is investigated.

SPECTROSCOPIC INVESTIGATION OF ARGON DC GLOW DISCHARGE IN PLASMA MEDIUM

In this study, UV-VIS-NIR (Ultraviolet Visible Near-Infrared) spectra emitted from Argon Glow discharge plasma in a low vacuum were recorded with a high-resolution Czerny-Turner type spectrometer. Argon plasma was produced at a pressure of 5mTorr and with a voltage of 584 V. Argon plasma was produced between two parallel stainless steel plates anode and cathode with a diameter of 15 cm, a thickness of 0.8 cm, and a distance of 13 cm between them. The radiative and collisional processes of the Argon plasma medium were modeled by the PrismSPECT atomic physics software (Software). The distributions of ion densities were calculated using the Saha-Boltzmann equation. The intensity of the excited energy levels of Ar(I) and Ar (II) ions were calculated in the electron temperature range of (0.4-3.5eV) and the mass density of (10-4-10-1gr/cm3). The UV-Visible-NIR spectra were simulated and compared with experimental spectra. The ratios of the intensities of the ArII/ArI (1s22s22p63s23p44f1/1s22s22p63s23p54p1) spectral lines were obtained for different plasma temperatures and densities. The temperature of the argon plasma was obtained from the spectral line intensity ratios.