High Strength Bridge Research Articles

A stochastic modeling method for three-dimensional corrosion pits of bridge cable wires and its application

ABSTRACT Cables have usually served as critical and vulnerable structural components in long span cable-supported bridges. Cable inspections revealed that corrosion, fatigue or coupled corrosion-fatigue were the ones of the main failure mechanisms. This paper proposed a stochastic modelling method for three-dimensional (3-D) corrosion pits of high-strength bridge wires, which can be applied to rapid fatigue life evaluation according to mass loss caused by surface corrosion pits of bridge wires nondestructively. High-strength steel wire specimens dismantled from the cable-stayed bridge served for 15 years were scanned to obtain the original surface corrosion data. The spatial position coordinate of corrosion pits were considered as random variable and can be well fitted by uniform distribution. While the number of corrosion pits can be fitted with generalized extreme value (GEV) distribution. The uniform corrosion depth du, which can be equivalent to mass loss rate, was calculated as the input corrosion parameter for 3-D corrosion pit modelling. The maximum pitting depth dmax for the steel wire was found to be associated with du. The geometric parameters for individual corrosion pits were recognized as pit depth d, depth-to-width ratio d/b, and aspect ratio b/a, which were fitted with different probability distributions. What follows is 3-D spatial corrosion pits simulation based on the individual corrosion parameter that were sampled and combined from the corresponding probabilistic distributions. Hereafter, fatigue life evaluation of corroded wires was conducted based on equivalent surface defect method and compared with the experimental results, verifying the effectiveness of the proposed modelling approaches.

Fatigue Behavior and Fracture Surface Analysis of Corroded High-Strength Bridge Cable Wires.

Bridge cable wires suffer from alternating stress and environmental erosion, leading to premature failure prior to its design life. This paper investigates the fatigue and mechanical behaviors of corroded bridge cable wires with a zinc-aluminum (Zn-Al) alloy coating. Based on the salt spray corrosion test and microstructure analysis, the anti-corrosion resistance and corrosion appearance characteristics of the Zn-Al alloy coating and galvanized coating were investigated. The Zn-Al alloy coating was superior in resistance to corrosion fatigue for the improvement in toughness and the generation of anti-corrosion Zn-Al and Fe-Zn-Al phases. Equations of the accelerated corrosion depth of the steel wires had been regressed to roughly estimate the corrosion life of the Zn-Al alloy coating, which can reach 29.1 years with a thickness of 70 μm. The fatigue and mechanical properties of the bare wires after the salt spray test were further studied based on tensile tests and fatigue tests. The fatigue properties of the bridge cable wire would decrease with the corrosion degree due to the deterioration and embrittlement of materials, where ductility characterized by the elongation rate was the most affected. Fracture surfaces of the wires were captured and analyzed based on a method for recognizing graphical contours. Insufficient fatigue life may occur in the steel wires after corrosion and increase with the degree of corrosion. The pit depth logarithmically weakened the fatigue life of steel wires for the weakening of fatigue toughness and the bearing area. The flat fracture was more common with a single fatigue source, while multiple fatigue sources led to step-like fractures for the generation of multiple dispersed crack propagation regions. Corrosion fatigue was more sensitive to the existence of fatigue sources than the reduction. Multiple initiation sources significantly reduced the fatigue life due to the cracking facilitation of the joint effect of multiple pits. The electrochemical reactions of corrosion can lead to material embrittlement and a reducing effect on the fracture toughness of the steel wires.

Probabilistic curvature-and-drift limit states predictive models of high-strength bridge columns

This study presents the derivation of closed-form component limit state expressions for high-strength concrete columns reinforced with high-strength steel bars (HSC-HSSB) from an extensive database through the moment–curvature analysis approach. Initially, sensitivity analysis was conducted to investigate the regularity of the parameters (section size, axial-load ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio, concrete compressive strength, and yield strength of longitudinal reinforcement) on the curvature limit state. The approach being convenient, massive samples were obtained in a short time, therefore, 6^7(279936) levels were generated to derive the predictive expressions of curvature and moment limit states by using the logarithm linearity model. Subsequently, based on the cross-section expressions, the drift displacement and shear force limit states predictive expressions were derived and verified by experimental studies, and these limit states were predicted with high precision. Moreover, after considering the uncertainty of material and section size, the curvature and drift displacement of the HSC-HSSB column exhibited a lognormal distribution, and the useful suggested standard deviations (βc) in different limit states were proposed for practical application of fragility curves to assess the vulnerability of bridge columns to earthquakes.

Field corrosion study of 690 MPa grade Sb-containing high strength bridge steel in tropical oceanic environment

Bridge steel is developing towards high strength, lightweight and high corrosion resistance. Sb element is reported to be able to improve the corrosion resistance of steel in marine environments. However, current research focuses on the corrosion behavior of low-strength or Cu/Ni/Cr-added bridge steel and pays little attention to Sb-containing high strength bridge steel. Thus, this paper examined the corrosion behavior of a new 690 MPa grade Sb-containing high strength bridge steel through field exposure in a tropical marine atmosphere. The corrosion rate of the steel was calculated by the weight loss method, and the corrosion characteristic and product properties were investigated by SEM, LSCM, EDS and XRD. Results showed that the corrosion rate decreased from 68.69 to 54.88 µm/y as the exposure time increased from 6 to 24 months. The decrease was due to the improvement of corrosion products and the weakening of acidification process. Specifically, the corrosion products became compact and electrochemically stable, and the γ-FeOOH was transformed into Fe3O4 and α-FeOOH with the extension of exposure time. This paper reported for the first time the corrosion evolution process of the 690 MPa grade Sb-added high strength bridge steel in a real marine atmosphere, which is of great significance for the material selection and anti-corrosion design of bridges in the future.

Effect of micro-galvanic corrosion on corrosion fatigue cracking of the weld joint of high strength bridge steel

The local electrochemical and corrosion fatigue cracking behavior of the weld joint of Q690qE high-strength bridge steel was investigated in simulated marine environment. It reveals the weld joint was vulnerable to corrosion fatigue failure in polluted marine atmosphere with the corrosion fatigue life considerably lower than that of parent metal. The micro-galvanic corrosion effect between CGHAZ and WM played a dominant role in the corrosion fatigue failure of the weld joint, leading to the final fracture mostly at CGHAZ. The micro-galvanic corrosion was caused by Volta potential variation among various subzones, which was evidenced by local electrochemical techniques.

Comparative study on mechanical and corrosion fatigue properties of high-strength bridge steels produced by TMCP and intercritical quenching & tempering process

The mechanical and corrosion fatigue properties of Q690 bridge steels produced by two different process were comparatively investigated. The steel produced by thermal-mechanical controlled processing (TMCP) and tempering had a slightly superior corrosion fatigue property to that produced by intercritical quenching & tempering (IQT). However, the TMCP + T prepared steel had a poor ductility and corrosion fatigue microcracks were prone to initiate due to high density of dislocations and M/A constituents. On the contrary, the steel produced by IQT had a good combination of mechanical and corrosion fatigue property. The corrosion fatigue initiation and propagation mechanism for both steels was proposed.

Thermomechanical rolling of heavy plates with 100 mm thickness, from highstrength bridge steels S460K2W and S460J5W with improved atmospheric corrosion resistance

The article describes the results of industrial production on NLMK DanSteel reversing rolling mill 4200 of heavy plates with thickness of up to 100 mm made of low-carbon micro-alloyed high-strength steels of categories S460K2W and S460J5W. This are copper-alloyed and chromealloyed steel grades, which provides increased atmospheric corrosion resistance. Steels of categories S460K2W and S460J5W are manufactured in accordance with new edition of standard EN 10025-5:2019 and are used primarily in the construction sector for bridge and overpass constructions. The required level of mechanical and operational properties is ensured by optimal combination of the designed chemical composition and technological modes of thermomechanical processing with final accelerated cooling. According to the findings presented in the article, NLMK DanSteel has received TUV NORD approval for the manufacturing of these steels in the thickness range up to 100 mm as per supplement dated 18.05.2021 to certificate 0045-CPR-0554 dated 12.06.2020 in accordance with regulations 305/2011/EU: System 2+.

Experimental and Numerical Investigation of the Seismic Performance of Bridge Columns with High-Strength Reinforcement and Concrete

Despite the numerous advantages high-strength reinforcement (HSR) and high-strength concrete (HSC) offer over conventional materials, the practical use of these materials for bridge column design in seismic zones has somewhat been limited. This is due to the insufficient research data and guidelines for the seismic design of bridges using HSC and HSR and the lack of a reliable analytical model. Therefore, to address this issue and promote the application of HSR and HSC, this paper investigates high-strength bridge columns’ seismic performance experimentally and numerically. Six large-scale reinforced concrete (RC) bridge columns and one multi-column bent frame were tested under a quasi-static cyclic loading with constant axial compression. The primary design parameters were axial load ratio, longitudinal and transverse reinforcement yield strength, and transverse reinforcement spacing. The failure pattern of high-strength columns was similar to conventional RC columns and satisfied the requirements for seismic design in terms of failure mode, hysteresis behavior, ductility, and energy dissipation capacity. The experimental ductility values of the high-strength columns were satisfactory and capable of meeting the ductility demand of most codes. Furthermore, a numerical model was built using the OpenSees program to predict the seismic performance of the specimens and then verified by comparing them with the test results of 12 columns. The numerical model’s results were in good agreement with the experimental results. The results suggested that numerical modeling techniques commonly used for normal strength concrete (NSC) columns can be used for HSC bridge columns by incorporating a proper material model.

Corrosion characteristics of Q690qE high-strength bridge steel in simulated coastal–industrial environment and its influence on mechanical and corrosion fatigue behaviors

The corrosion behavior of Q690qE high-strength bridge steel in simulated coastal–industrial environment was investigated through accelerated corrosion, and the corrosion features under different corrosion times were characterized. The effect of pre-corrosion level on mechanical and corrosion fatigue behaviors was also studied by using pre-corroded fatigue samples. Results show that corrosion pits were more likely to form in this environment, with chloride ions concentrating at the bottom of the pits, resulting in significant loss of the mechanical property and corrosion fatigue life. The corrosion fatigue initiation mechanism was proposed, and a prediction model for the residual corrosion fatigue life of corroded Q690qE steel was developed.

Effect of silicon on the corrosion behaviour of 690 MPa weathering bridge steel in simulated industrial atmosphere

690 MPa weathering bridge steel is a new generation of high strength bridge steel developed in China, and its corrosion resistance is the focus of attention. Wet/dry cyclic tests、electrochemical tests in conjunction with surface analysis techniques have been performed to study the role of silicon on the corrosion behaviour of 690 MPa weathering bridge steel in simulated industrial atmosphere. The results indicate that with the increase of Si content, the corrosion rate of the tested steel increases, the protection index α/γ* decreases, and the corrosion resistance decreases gradually. Si mainly exists in the rust layer in the form of Fe2SiO4, and the content of Fe2SiO4 in the rust layer depends on the Si content. The loose and porous Fe2SiO4 in the rust layer cannot prevent the entry of corrosive media such as O2 and HSO3-, would hinder the formation of the Fe3O4 phase, and eventually leads to a lower content of dense and stable α-FeOOH phase in the rust layer, which is very important for the rust layer protection. The above factors should be responsible for the poor corrosion resistance with high Si content.

Deformation Law of Cold Drawing Process of High Strength Bridge Cable Steel

High-strength cable-steel bridge is the “lifeline” of steel structure bridges, which requires high comprehensive mechanical properties, and cold-drawing is the most important process to produce high-strength cable-steel bridge. Therefore, through the ABAQUS platform, a bridge wire drawing model was established, and the simulation analysis on the process of stress strain law and strain path trends for high-strength bridge steel wire from Φ 12.65 mm by seven cold-drawing to Φ 6.90 mm was conducted. The simulation results show that the wire drawing the heart of the main axial deformation, surface and sub-surface of the main axial and radial deformation occurred, with the increase in the number of drawing the road, the overall deformation of the wire was also more obvious non-uniformity. In the single-pass drawing process, the change in the potential relationship of each layer of material was small, and multiple inflection points appeared in the strain path diagram; the change in the seven-pass potential relationship was more drastic, which can basically be regarded as a simple superposition of multiple single-pass pulls.

Effect of Welding Peak Temperature on Microstructure and Impact Toughness of Heat-Affected Zone of Q690 High Strength Bridge Steel.

The effect of peak temperature (TP) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble-3500 thermal simulation testing machine. The results show that the microstructure of the inter critical heat-affected zone (ICHAZ) was ferrite and bainite. The microstructure of fine grain heat-affected zone (FGHAZ) and coarse grain heat-affected zone (CGHAZ) was lath bainite (LB), lath martensite (LM), and granular bainite (GB), but the microstructure of FGHAZ was finer. With the increase in peak temperature, the content of LB and GB decreased, the content of LM increased, and the lath bundles of LM and LB gradually became coarser. With the increase in peak temperature, the grain size of the original austenite increased significantly, and the impact toughness decreased significantly. When the peak temperature was 800 °C, the toughness was the best. For CGHAZ, the peak temperature should be less than 1200 °C to avoid excessive growth of grain and reduction of mechanical property.

The measurement of SH-CCT curve and analysis on microstructure and performance of heat-affected zone of Q690 high-strength bridge steel

The heat-affected zone continuous cooling transition curve (SH-CCT) of the experimental steel is drawn by using the Gleeble-3500 thermal simulation testing machine. The influences of different cooling rates and peak temperatures on the microstructure and mechanical properties of HAZ were studied. The results show as the cooling rate increases, the experimental steel undergoes LB + GB and LM + LB + GB phase transformations successively, and the micro-hardness gradually increases. When the heat input is 20kJ/cm, the microstructure of inter-critical heat-affected zone (ICHAZ) is F + B, the microstructure of fine grain heat-affected zone (FGHAZ) and the coarse grain heat-affected zone (CGHAZ) is LM + LB + GB. As the peak temperature increases, the micro-hardness first increases and then decreases, the -40°C impact absorbing energy gradually decreases. This conclusion can provide a reference for further study on the microstructure and mechanical properties of HAZ of Q690 bridge steel.

The measurement of SH-CCT curve and analysis on microstructure and performance of heat-affected zone of Q690 high-strength bridge steel

The measurement of SH-CCT curve and analysis on microstructure and performance of heat-affected zone of Q690 high-strength bridge steel

A multi-scale corrosion fatigue damage model of high-strength bridge wires

Cables are the most sensitive components in cable-supported bridges, and the failure of cables is usually caused by the degradation of mechanical properties of internal wires. Based on Faraday's law and the rates of microcrack initiation and propagation, a multi-scale corrosion fatigue damage model was developed to describe the damage evolution in the stages of pit growth and microcrack propagation. The accuracy and effectiveness of this damage model were also verified through the experimental data of corrosive fatigue life of high-strength bridge wires. The result shows that this damage model can describe the multi-scale corrosion fatigue damage evolution process of high-strength bridge wires reasonably and effectively, which provides a new way to better understand the trans-scale damage evolution mechanism during the corrosion fatigue process of high-strength bridge wires.

A continuum model for damage evolution simulation of the high strength bridge wires due to corrosion fatigue

Continuum damage model and simulation algorithm are developed to simulate the corrosion fatigue process of high strength bridge cable steel wires. The developed model can be used to predict the damage curves during the corrosion fatigue process based on the concept of continuum damage mechanics (CDM). The algorithm can be used to simulate the corrosion fatigue damage evolution process of bridge wires from local damage to failure. As case study, the developed model and algorithm have been applied to simulate corrosion fatigue damage evolution of bridge wires under cyclic tensile in 3.5 wt% NaCl solution at 6 Hz, and the numerical prediction results are compared with experimental results. It shows that the developed model and algorithm are reasonable and can be used to study and describe corrosion fatigue damage evolution of bridge wires.

Effective microstructure unit in control of impact toughness in CGHAZ for high strength bridge steel

The high strength bridge steel was processed with the simulated coarse grain heat affected zone (CGHAZ) thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope (OM), scanning electron microscope (SEM), electron backscattering diffraction (EBSD) and transmission electron microscope (TEM), and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. With decreasing heat input, both bainite packet and block are significantly refined, and the toughness has an increasing tendency due to the grain refinement. The fracture surfaces all present cleavage or fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of high strength bridge steel.

Experimental investigation and numerical simulation on fatigue crack behavior of bridge steel WNQ570 base metal and butt weld

The experimental study on the fatigue crack growth rate and the threshold of high strength bridge steel WNQ570 base metal and butt weld has been performed. Two data processing methods are conducted to derive fatigue crack growth parameters of 95% survival probability. It turns out that the fatigue crack growth rate based on each specimen data is larger than that based on group method of data processing in terms of normal stress intensity range (10–70MPam0.5). The fatigue crack growth rates increase and the fatigue crack growth thresholds decrease with increasing stress ratios. For WNQ570 of the batch utilized in this research, the fatigue crack growth rate of base metal is lower than butt weld. The fatigue crack performance of WNQ570 base metal is also better than other common bridge steels including HPS485W, 14MnNbq, Q345qD and the universal steel performance provided by BS7910 and IIW-1823-07. Based on the measured FCGR parameters, numerical simulation by Franc3D and ABAQUS can precisely predict the fatigue life of compact tension specimens, which demonstrates that simulation method is appropriate to be applied to fatigue assessment practice of whole steel bridges based on linear elastic fracture mechanics (LEFM).

Comparison of Measured and AASHTO LRFD-Predicted Residual Prestress Forces, Shear and Flexural Capacities of High-Strength Prestressed-Concrete Bridge Girders

AbstractThis paper describes a case study to quantify the behavior of precast, prestressed-concrete bridge girders made with high-strength concrete. As part of the case study, four bridge girders made with 77.2-MPa (11.2-ksi) concrete were salvaged from a decommissioned bridge in Orem, Utah. Each girder was subjected to a flexural cracking test to determine a prestress loss of 22% after approximately 7 years of service life. Once the prestress losses were quantified, a flexural capacity test was performed on one girder. Shear capacity tests were performed at various distances from the support on the remaining three girders. The measured prestress losses and various capacities were compared with estimated values calculated according to procedures in current bridge specifications. The predicted flexural capacity was found to be 7.3% conservative compared with the measured capacity. The measured shear capacities were all within 12% conservative compared with the AASHTO shear procedures. In addition to the ph...

Uniform and Pitting Corrosion Modeling for High-Strength Bridge Wires

AbstractCable inspections revealed that severe corrosion of steel wires is one of the main failure mechanisms of cables. Accelerated corrosion experiments were conducted to evaluate the variation in the uniform and pitting corrosion depths of high-strength steel wires over time. The measured uniform corrosion depth followed a lognormal distribution with time-dependent corrosion variables at both the zinc coating corrosion stage and the steel corrosion stage. The block’s maximum pitting factors from a different exposure time were proven to be drawn from the same underlying continuous population and followed Gumbel distribution. The regression models of the scale and location parameter with increased surface area were obtained based on the experimental block’s maximum pitting factors. The extreme value distribution of the pit depth of corroding steel wires could be predicted by the developed statistical uniform and pitting factor models.