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Damage identification, both in terms of size and location, in bridges is important for timely maintenance and to avoid any catastrophic failure. An earlier experimental study showed that damage in a steel box girder orthotropic plate can be successfully detected using the measured vibration acceleration data. In this study, the wavelet packet decomposition (WPD) method is used to analyze the measured vibration acceleration responses and then the estimation of the permutation entropy (PE) on the re-constructed signals. A damage index is then defined based on the permutation entropy difference (PED) between the damaged and the healthy conditions to detect the location and size of the damage. The method is further validated through the finite element (FE) model of a steel box girder and the computed vibration acceleration responses when subjected to the sinusoidal excitations at different frequencies. In addition, the robustness of the methodology under different white noise interference conditions is also verified. The results show that the proposed methodology can effectively identify the location of human-made damage and accurately estimate the degree of damage under different frequencies of sinusoidal excitation. The method has shown a strong anti-noise property. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Near-field (NF) earthquakes have distinct ground motions, forward directivity pulses, and fling-step motions, causing structural responses to differ from far-field (FF) earthquakes. Seismic isolation is regarded as a developed and successful technology that may be applied to enhance a structure’s functionality and safeguard it against catastrophic earthquake effects. The variation in mechanical properties of seismic isolation also significantly influences bridge seismic response. The study investigates the influence of lead rubber (LRB) isolators and the characteristics of ground motions on seismically isolated bridges, aiming to determine optimal parameters for minimal earthquake response. Key parameters include ground motion characteristics, characteristic strength (Q), and isolator flexibility. The study modeled the force-deformation behavior of isolators using bilinear behavior, reflecting the Bouc-Wen hysteric model. CSI Bridge was used to model seismically isolated steel box girder bridges, with eight natural accelerograms assessing a 2% probability of exceedance in 50 years. The peak responses of pier displacement (MPD), isolator hysteric energy (HED), base shear, and deck acceleration are chosen as the response parameters for the comparison. To evaluate the response parameters, the earthquake data are scaled to the three studied peak ground acceleration (PGA) levels of design level (0.2 g), extreme level (0.4 g), and rare-extreme level (0.8 g). The findings offer insight on the relevance of isolator stiffness and its influences on the seismic performance of isolated bridges. The study identifies minimum values for pier displacement, hysteric energy, deck acceleration, and base shear at specific Q/weight sustained by isolator (W) and time period (T) values. Recommendations are made for the preliminary seismic isolation design of bridges with LRB isolators, highlighting the importance of PGV to PGA ratio in earthquake damage assessment.

Due to the significant weight of the steel box girder and the substantial gap between temporary piers, the stress concentration and localized deformation of the girder's bottom plate are pronounced during the incremental launching construction process. In this study, the multi-scale finite element method was employed to simulate the incremental launching process of the steel box girder, analyze the pattern of localized deformation in the bottom plate contact area, and propose corresponding optimization control measures. Additionally, the entire incremental launching process was monitored, and the improvement in localized deformation before and after the optimization of the incremental launching scheme was analyzed. The results illustrate that the original incremental launching scheme led to substantial localized deformation in the bottom plate contact area of the steel box girder. Optimal control measures were implemented for the four incremental launching construction schemes. The optimal scheme significantly mitigated the localized deformation of the steel box girder's bottom plate, with an average decrease in deformation of 48.32%. These findings can provide robust technical guidance and data support for the control of localized deformation in large-span steel box girders during the incremental launching construction process. [ABSTRACT FROM AUTHOR]

Near-field (NF) earthquakes have distinct ground motions, forward directivity pulses, and fling-step motions, causing structural responses to differ from far-field (FF) earthquakes. Seismic isolation is regarded as a developed and successful technology that may be applied to enhance a structure's functionality and safeguard it against catastrophic earthquake effects. The variation in mechanical properties of seismic isolation also significantly influences bridge seismic response. The study investigates the influence of lead rubber (LRB) isolators and the characteristics of ground motions on seismically isolated bridges, aiming to determine optimal parameters for minimal earthquake response. Key parameters include ground motion characteristics, characteristic strength (Q), and isolator flexibility. The study modeled the force-deformation behavior of isolators using bilinear behavior, reflecting the Bouc-Wen hysteric model. CSI Bridge was used to model seismically isolated steel box girder bridges, with eight natural accelerograms assessing a 2% probability of exceedance in 50 years. The peak responses of pier displacement (MPD), isolator hysteric energy (HED), base shear, and deck acceleration are chosen as the response parameters for the comparison. To evaluate the response parameters, the earthquake data are scaled to the three studied peak ground acceleration (PGA) levels of design level (0.2 g), extreme level (0.4 g), and rare-extreme level (0.8 g). The findings offer insight on the relevance of isolator stiffness and its influences on the seismic performance of isolated bridges. The study identifies minimum values for pier displacement, hysteric energy, deck acceleration, and base shear at specific Q/weight sustained by isolator (W) and time period (T) values. Recommendations are made for the preliminary seismic isolation design of bridges with LRB isolators, highlighting the importance of PGV to PGA ratio in earthquake damage assessment. [ABSTRACT FROM AUTHOR]

Abstract The time-varying temperature distributions on bridge structures may remarkably change structural performance, which may result in differential strain/stress responses on structural members compared with the design conditions. Therefore, it is crucial to have a comprehensive understanding of temperature distributions and its effects on bridges. In this study, taking advantage of structural health monitoring technology, 1-year field monitoring data collected from a long-span suspension bridge were used to investigate the temperature distributions and their effects on the steel box girder. Specifically, the distributions and probability statistics of temperatures on the top and bottom plates were firstly analyzed. Based on which, the transverse and vertical temperature differences on the box girder were further examined, moreover, the representative values of temperature differences for various return periods were calculated by exceedance probability method. At end, a temperature prediction method was proposed to simulated the temperature field distributions during bridge life cycle, to provide substantial temperature data for estimating future operation condition. The results of this study were beneficial to structural evaluation of in-service bridges to ensure their serviceability and integrity in the life cycle.

The time-varying temperature distributions on bridge structures may remarkably change structural performance, which may result in differential strain/stress responses on structural members compared with the design conditions. Therefore, it is crucial to have a comprehensive understanding of temperature distributions and its effects on bridges. In this study, taking advantage of structural health monitoring technology, 1-year field monitoring data collected from a long-span suspension bridge were used to investigate the temperature distributions and their effects on the steel box girder. Specifically, the distributions and probability statistics of temperatures on the top and bottom plates were firstly analyzed. Based on which, the transverse and vertical temperature differences on the box girder were further examined, moreover, the representative values of temperature differences for various return periods were calculated by exceedance probability method. At end, a temperature prediction method was proposed to simulated the temperature field distributions during bridge life cycle, to provide substantial temperature data for estimating future operation condition. The results of this study were beneficial to structural evaluation of in-service bridges to ensure their serviceability and integrity in the life cycle. [ABSTRACT FROM AUTHOR]

This study analyzes the Unibridge system, a modular steel box girder employing two pins for longitudinal connections, thereby expediting construction compared to traditional girders. A finite element model was developed to analyze the stress on these pins in a single-box girder with five segments and a reinforced concrete floor slab. Various loads were applied following the Indonesian bridge loading standard, SNI 1725:2016. The model considers operational load analysis and assumes full composite behaviour between the top flanges of the girder and the concrete floor slab. The results indicate that the Von-Mises stress on the pins reaches a maximum of 490.95 MPa under combined service loads, consistently remaining below the specified material yield stress limit of 1200 MPa. Consequently, the Demand Capacity Ratio (DCR) is 0.41. As a result, the Unibridge girder connection pins do not experience plastic deformation under the applied loads. [ABSTRACT FROM AUTHOR]

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Damage identification, both in terms of size and location, in bridges is important for timely maintenance and to avoid any catastrophic failure. An earlier experimental study showed that damage in a steel box girder orthotropic plate can be successfully detected using the measured vibration acceleration data. In this study, the wavelet packet decomposition (WPD) method is used to analyze the measured vibration acceleration responses and then the estimation of the permutation entropy (PE) on the re-constructed signals. A damage index is then defined based on the permutation entropy difference (PED) between the damaged and the healthy conditions to detect the location and size of the damage. The method is further validated through the finite element (FE) model of a steel box girder and the computed vibration acceleration responses when subjected to the sinusoidal excitations at different frequencies. In addition, the robustness of the methodology under different white noise interference conditions is also verified. The results show that the proposed methodology can effectively identify the location of human-made damage and accurately estimate the degree of damage under different frequencies of sinusoidal excitation. The method has shown a strong anti-noise property.

Fatigue cracks commonly occur on the steel box girders of long-span bridges, while are barely summarized and analyzed in a statistic way due to the non-standard records on reports. This paper proposes to establish a standardized database of cracks on steel box girders from multiple data sources. The data are collected from 7 bridges, while 4 of them provide the inspection reports for 28 years in accumulation. By conducting the data specification and standardization, a tuple containing 15 parameters is proposed to store the information of each crack. The crack categorization is then carried out, resulting in 6 series and 34 types. In addition, the analysis module is proposed for the database to show the crack properties in various aspects, including the longitudinal and transverse distribution of the cracks, and the growing process of the crack length. It can be concluded that the database in its current form can benefit bridge management and maintenance in practice. Moreover, it lays the foundation for building the knowledge graph of cracks on steel box girders in the future, which can be helpful in predicting the crack behavior in both data-driven and mechanical ways. [ABSTRACT FROM AUTHOR]

The stability of stiffened plates has always been an important research issue in bridge engineering. The application of stiffened curved plates (SCPs) in the field of bridge engineering is gradually increasing, but the corresponding research needs to be more comprehensive. Guidelines have yet to be established in bridge design codes for the stability design of SCPs. To study the failure mode and ultimate resistance of SCPs with trapezoidal longitudinal stiffeners under uniaxial compression, six test specimens with a scale ratio of 1:2 were designed in this work, and static loading tests were conducted on three kinds of SCPs with different curvatures. The influence of curvature on the ultimate resistance and failure mode of SCPs was analyzed, and a calculation method for the ultimate resistance of SCPs was discussed. Results showed that the SCPs with trapezoidal longitudinal stiffeners have sufficient overall and local stability. The failure of the SCPs occurred locally in the subpanels between stiffeners, and the ultimate resistance of specimens with different bending radii was insignificantly different. The ultimate compressive resistance calculated following the effective section of the main plate was close to the test results. When the subpanels are locally buckled, the stiffened flat plate calculation method can be used to analyze the ultimate resistance of SCPs, and the calculated results deviate conservatively. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study analyzes the Unibridge system, a modular steel box girder employing two pins for longitudinal connections, thereby expediting construction compared to traditional girders. A finite element model was developed to analyze the stress on these pins in a single-box girder with five segments and a reinforced concrete floor slab. Various loads were applied following the Indonesian bridge loading standard, SNI 1725:2016. The model considers operational load analysis and assumes full composite behaviour between the top flanges of the girder and the concrete floor slab. The results indicate that the Von-Mises stress on the pins reaches a maximum of 490.95 MPa under combined service loads, consistently remaining below the specified material yield stress limit of 1200 MPa. Consequently, the Demand Capacity Ratio (DCR) is 0.41. As a result, the Unibridge girder connection pins do not experience plastic deformation under the applied loads.

Due to the significant weight of the steel box girder and the substantial gap between temporary piers, the stress concentration and localized deformation of the girder’s bottom plate are pronounced during the incremental launching construction process. In this study, the multi-scale finite element method was employed to simulate the incremental launching process of the steel box girder, analyze the pattern of localized deformation in the bottom plate contact area, and propose corresponding optimization control measures. Additionally, the entire incremental launching process was monitored, and the improvement in localized deformation before and after the optimization of the incremental launching scheme was analyzed. The results illustrate that the original incremental launching scheme led to substantial localized deformation in the bottom plate contact area of the steel box girder. Optimal control measures were implemented for the four incremental launching construction schemes. The optimal scheme significantly mitigated the localized deformation of the steel box girder’s bottom plate, with an average decrease in deformation of 48.32%. These findings can provide robust technical guidance and data support for the control of localized deformation in large-span steel box girders during the incremental launching construction process.

Steel box girders are widely used in cable-stayed bridges, while they are prone to severe damage under explosions. This paper investigates the deformation and energy dissipation of steel box girder of cable-stayed bridges under blast impact, caused by the accidental explosions of tanker trucks and vehicles. In this study, Hypermesh and LS-DYNA are employed to simulate the dynamic responses of a real steel box girder cable-stayed bridge under explosions. The deformation response and energy absorption of the box girder under explosions are investigated. Several failure modes and failure processes are analyzed and summarized. The findings indicate that the failure mode of an orthotropic steel bridge panel under blast impact is primarily local damage, with the damage process being divided into three stages: local plate deformation, fragment formation, and petal formation. For bridge deck explosions, the main energy dissipation components of steel girders are the bridge panel, web, diaphragm and rib stiffeners. The research results can provide the basis for the follow-up study on the anti-explosion safety of bridge structures.

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal magnetic memory testing (MMMT) is a nondestructive testing method for the early diagnosis and prevention of ferromagnetic metal components. Many scholars have studied the effect of uniform stress on the self-magnetic-leakage field (SMLF) strength of ferromagnetic materials. However, there are still insufficient studies on stress concentration caused by uneven force under the combined action of bending and shear. In this study, MMMT applied to bridge steel structures and its applicability in monitoring damage to steel structures under complex stresses was explored, and a static loading test was carried out on a steel box girder model. We studied the distribution law of the SMLF on the surface of the top flange, bottom flange, and web of the steel box girder and the force-magnetic relationship of magnetic signal measuring points that were symmetrical with the strain measuring points. Furthermore, we analyzed the magnetic parameters from the statistical point of view to characterize the critical yield state at different force parts of the steel box girder. The results indicated that the stress concentration position at different force parts of the steel box girder could be determined by the peak value of the distribution curve of the normal component H p (y) of the SMLF intensity. Thereafter, the yield strength of different stressed parts could be accurately determined by the peak value of the force-magnetic relationship curve to identify the safety state limit of the steel box girder structure and issue an early warning before the steel box girder was damaged. Finally, the reliability of the force-magnetic relationship between different force parts of the steel box girder and the imposed load F was further verified by the SMLF strength average Δ H p (y) a . This study can provide an experimental reference for the application of MMMT in the early warning of the state of damage of steel box girder. [ABSTRACT FROM AUTHOR]

In general, a web of the steel box girder is designed as an independent. However, in actual behaviour, since the web and the flange behave in couple, the web is considered to have a higher bending buckling strength than the designed standard due to the restraint by the flanges. Therefore, horizontal stiffeners for the web of the steel box girder might be omitted. In this study, focusing on the effect of the coupled behaviour of the web and flange on the bending buckling strength of the web of a box girder, FE analyses were carried out of steel box girder model with different structural configuration and of a panel model under identical boundary conditions as the design. From these results, it was found that the web of box girders without horizontal stiffeners have a higher bending buckling strength than the panel model due to restraint by the top of end of the web by the flange. In the case that buckling parameters of the flange are smaller than those critical buckling parameters, the influence of the bending buckling of the web of the box girder on the buckling strength of the flange is slight. [ABSTRACT FROM AUTHOR]

As a necessary temporary facility of port engineering, the prefabrication yard is designed with a single ship type for the supporting components of the shipping wharf bottom resting foundation. After the transformation from the prefabrication yard to the factory, the selection range of ships corresponding to the shipping wharf is small, and the shipping capacity of the components is limited. Taking the shipment of 3 500 t caissons and 5 000 t caissons as examples, the bottom resting foundation design of the shipping wharf was carried out based on two ship types: berthing semi -submersible barge9and semi-submersible barge 11. An adjustable bottom resting foundation was designed based on the concept of assembly. A comprehensive evaluation was constructed from the aspects of foundation design, construction, and other aspects combined with on-site application. It is found that the multipurpose semi-submersible barge bottom resting foundation meets the matching requirements of the same shipping wharf for different ship types, and is a type of bottom resting foundation structure suitable for large-scale port engineering prefabrication yard components for factory production. It has broad application prospects for the construction of large component prefabrication yards such as caissons in other port engineering at home and abroad. [ABSTRACT FROM AUTHOR]

Orthotropic anisotropic steel bridge panels are widely used in civil engineering due to their advantages of light deadweight, high ultimate bearing capacity, and wide range of applications. However, their fatigue problem is serious, and the fatigue-resistant design of the steel box girder diaphragm curved cutout is still difficult. In order to effectively predict the fatigue life of this typical fatigue-susceptible detail, a fatigue test of the specimen with curved notched segments of the diaphragm was carried out. ABAQUS 2016 version finite element analysis software was used to establish three kinds of finite element simplified models of the fatigue specimens with curved notches, and the laws of the influence of different notch radii on the fatigue life of the specimens were studied. Through the finite element solution of the three arc notch specimen models with different radii under the tensile load of 50 kN their respective principal stress distributions were obtained. The critical distance theory was introduced to analyze the characteristic stresses in the stress concentration area of the arc notch, and the point method and line method were used to calculate the characteristic stresses. The fatigue life prediction models of three kinds of notched components were established by combining the material fatigue limit and FE-safe life results. The results show that the point method is more conservative than the line method; no matter if the point method or the line method is used, the characteristic stress and the notch radius are inversely proportional to each other, and it is beneficial for the fatigue life of the structure to appropriately increase the notch radius. The fatigue prediction model of steel box girder diaphragms with curved notches based on the critical distance theory is of high accuracy, which is basically consistent with the test results, verifying the feasibility of the critical distance theory in the fatigue life prediction of notched specimens, and providing a reference for the fatigue life assessment of similar steel structures. [ABSTRACT FROM AUTHOR]

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Jiyang Yellow River highway-railway combined bridge is the key control project of Jinan-Binzhou Railway. Combined with the control factors along the line, the three bridge sites in this section are compared comprehensively and selected in terms of technology and economy, and finally the scheme of highway-railway combined bridge site crossing the yellow river with the planned G308 is selected due to the fact that it saves channel resources, has a small flow angle with the main river channel, enjoys good flood discharge conditions and is in line with the conditions of Jiyang station. On this bridge site, subject to flood control, navigation and structural restrictions, the unequal span scheme of (228+240+300) m in the main channel is determined. According to the requirements of the span and height limit of the airport, three types of bridge schemes of the main bridge of the highway-railway combined super-large bridge are put forward, including steel truss low-pylon cable-stayed bridge, continuous steel truss bridge with upper stiffening and steel box low-pylon cable-stayed bridge. The three schemes share the same span arrangement of (72 + 144 + 228 + 240 + 300+132 + 84) m. Through comparison and analysis of multiple factors such as structural stress, construction scheme, connection conditions and technical economy, it is found that all the three bridge schemes could meet the functional requirements of the structure. The steel box low-pylon cable-stayed bridge with highway and railway on the same deck could reduce the elevation of highway bridge, but the highway connection conditions are poor. The stiffness of the continuous steel truss bridge with upper stiffening is the largest, but the steel consumption is also the largest and uneconomic. Finally, the steel truss girder low-pylon cable-stayed bridge type with highway and railway on different decks is recommended. [ABSTRACT FROM AUTHOR]

To study the influence of maintenance track on the vortex-induced vibration (VIV) performance of main girder, the VIV response and time history of surface pressure data of a section model were obtained by wind tunnel vibration and pressure measurements for a large-span steel box girder suspension bridge. The VIV performance of the main girder was tested at ±5° attack angles of various maintenance track positions, including 1, 2.5, and 5 m away from the outer edge of the girder bottom plate. The mean values, root variances and amplitude spectra of vortex-induced force and the correlation and contribution coefficients of local aerodynamic force to overall aerodynamic force were analyzed. The results show that when the maintenance track is 1 m away from the outer edge of the bottom plate, the main girder exhibits the worst VIV performance with a maximum amplitude of 0.457 m, far beyond the allowable value of the specification. The VIV performance of the main girder was greatly improved by moving the maintenance track inward. The pressure analysis indicates that the large pressure fluctuation at the front and rear parts of the upper surface is attributed to the strong VIV of the main girder. In this sense, the improved VIV performance is mainly contributed by the weakening of pressure fluctuation in these two areas and the reduced local aerodynamic force. When the distance between the maintenance track and bottom plate is adjusted to 2.5 m, a 3.5 m wind barrier with a ventilation rate of 30% effectively inhibits the VIV of the box girder. The main reason for the suppression is that the elimination of pressure fluctuation on the upper surface of the girder disturbs the correlation between local aerodynamic force and overall aerodynamic force, consequently diminishing the contribution of local aerodynamic force to the vortex-induced force.

It is valuable to conduct non-destructive testing of steel box girders in order to evaluate their working status. The metal magnetic memory inspection method can effectively identify early damage and the stress state of ferromagnetic materials. However, applying this technique in the inspection of steel components is difficult due to insufficient research on magnetic memory signals under complex stress states. This study analyses the magnetic memory effect for a steel box girder under four-point bending. It is shown that the normal component Hp(y) of the magnetic signal can effectively locate the stress concentration area. The average absolute value Hm of Hp(y) can identify the yielding state and predict the occurrence of failure. Hm changes roughly quadratically with the average strain εm in the elastic stage of the specimen, which is consistent with the theoretical result. The ratio D of Hm to the equivalent stress σeqv changes continuously with the applied load, which can be used to estimate the stress state of the steel box girder. [ABSTRACT FROM AUTHOR]

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With the development of the economy and transportation, more and more cross-sea bridges are appearing in people's view. However, cross-sea bridges are not only subjected to repeated traffic loads but also to corrosion from the marine environment. In addition, the steel box girder deck plate is directly subjected to repeated vehicle loads, and its welded details are highly susceptible to fatigue damage and destruction, resulting in fatigue or corrosion damage to the welded top plate-U rib of the cross-sea steel box girder. This paper is based on fracture mechanics analysis methods and finite element simulation analysis, in order to establish the numerical analysis method of the welded top plate-U rib of the steel box girder deck plate fatigue, which is to take into account the coupling of the marine corrosive environment and fatigue cyclic loading, explore the welded top plate-U rib of the stress intensity factor, crack expansion, crack expansion life and total fatigue life of the welded details. Furthermore, the establishment of the welded top plate-U rib corrosion fatigue life assessment model is to explore the fatigue life of different top plate thicknesses. The results show that: the stress intensity factor along the crack front is symmetrically distributed, and with the increase in the crack expansion step, the corresponding stress intensity factor amplitude is also increasing; in addition, with the increase in the top plate thickness, fatigue crack expansion rate significantly reduced. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Management / Gongcheng Guanli Xuebao is the property of Journal of Engineering Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The frequently conventional assumption that bridge temperature is uniformly distributed on long-span bridges could lead to uncertainty when analyzing temperature effects. This study investigated the surface temperature of steel box girders on a long-span suspension bridge, emphasizing the distribution characteristics in the longitudinal (spanwise) direction. The girder surface temperature distribution was monitored using the long-term structural health monitoring system (SHMS). First, the probability density functions (PDF) of the girder surface temperature were analyzed. The results showed that the PDFs had bimodal characteristics and could be well-fitted using the weighted superposition of two normal distributions. Meanwhile, there was an obvious difference between the PDFs of the measuring points at different longitudinal sections of the bridge, which is inconsistent with the assumption that the temperature was uniformly distributed in the longitudinal direction. Subsequently, the longitudinal distributions of the girder surface temperature were statistically analyzed, and polynomial functions were introduced to fit the distribution curves along the left and right sides of the mid-span. A correlation analysis was then performed, highlighting the variability in temperature in the longitudinal direction. Additionally, the longitudinal temperature distribution pattern could be summarized as (i) the highest in the mid-span, the lowest in the tower, and increasing along the side span; (ii) there were also significant differences between the left and right sides of the mid-span. Finally, the time- and space- distributions of the temperature were studied, and a contour map was displayed. The results showed that the girder surface temperature had significant three-dimensional spatial characteristics and was not only non-uniformly distributed in space but also in time. This work is useful for a more accurate analysis of temperature effects on long-span bridges. [ABSTRACT FROM AUTHOR]

The vertical temperature gradient of steel box girders in cold regions is not stipulated in the relevant specifications of China. Therefore, a systematic and comprehensive study was necessary. The vertical temperature distribution characteristics of the web were analyzed on the basis of steel box girder temperature monitoring data for 1 year in a cold region to obtain a vertical temperature gradient model corresponding to the actual situations of cold regions, which was compared with the specification. The temperature field numerical model was verified using the measured data. The parameter sensitivity of the vertical temperature gradient was analyzed. Results show that the daily variation of the web temperature of a steel box girder in cold regions is similar to a sinusoidal curve. The temperature fluctuation range in summer is larger than that in winter. Moreover, the positive and negative temperature differences occur in summer and winter, respectively. The vertical positive and negative temperature gradients are in the forms of an exponential function and a broken line, respectively. The fitted vertical temperature gradient in this paper was basically greater than the specification. The span of boundary conditions of the numerical model was reasonable. The influence of parameters on the vertical temperature gradient ranks ranked as follows: bridge deck pavement thickness > radiation absorption rate > wind speed > coefficient of heat conductivity > specific heat capacity. [ABSTRACT FROM AUTHOR]

Metal magnetic memory testing (MMMT) is a nondestructive testing technique that can detect early signs of damage in components. Many scholars have studied the effect of uniform stress on the self-leakage magnetic field (SLMF) strength of ferromagnetic materials. However, there is still insufficient research on the stress concentration caused by uneven stress, under the combined action of bending and shear. In this study, we studied the law of distribution of the magnetic signal, HP(y) and magnetic gradient, K, on a part of the surface of a steel box girder damaged by buckling, using a four-point bending pattern. The results showed that combining the three peak positions, namely, the magnetic signal, its newly added comparing initial magnetic signal, and magnetic gradient distribution curves, could accurately determine all stress concentration positions on the flange of the steel box girder, and reduce the interference of the initial complex residual magnetic field. Furthermore, we studied the quantitative relationship between normal stress, shear stress, and a magnetic signal. It was found that the stress-magnetic relationship conformed to the Jiles–Atherton model. The peak value of HP(y) – , |HP(y)|a – , and Kmax – relationship curves could be used as the characteristic point of the critical yield stress at the action of normal and shear stress. The degree of stress concentration of the flange and web could be quantitatively evaluated by fitting the Kmax – relationship. This study can provide an experimental reference for the application of MMMT in the evaluation and early warning of the state of damage to a steel box girder. [ABSTRACT FROM AUTHOR]

Aiming at the relative deviation error of designed location for the bearing in the steel box girder, a full bridge model of the steel box girder was established. The local deformation and stress under different bearing deviations were studied. The influence of bearing deviation on roof displacement was analyzed by extracting the vertical deformation of the roof over the middle span and bearing. Based on the stress at the junction of diaphragm, stiffener and bottom plate, the variation law of peak stress under different bearing deviations was studied. The results showed that the displacement of the beam relative to the bearing had little influence on the deformation and stress of the roof and diaphragm of the steel box girder. When the vertical stiffener and bottom plate were shifted 50 mm, the peak stress and local stress of components increased sharply, which should be mainly monitored in incremental launching construction. Considering that the vertical stiffener was the most unfavorable component of the steel box girder under the bearing deviation, it was suggested to set 50 mm as the offset limit of the bearing to ensure the safety of the incremental launching construction, but the specific offset limit should refer to the actual construction. [ABSTRACT FROM AUTHOR]

Based on a three-tower self-anchored suspension bridge, the pushing scheme for a ultra-wide and long-span steel box girder is studied. In view of the problems such as great difficulty in control of large transverse deformation, strong sensitivity to temperature, great difficulty in control of pushing accuracy and synchronization and high safety risk in the pushing process of the ultra-wide and long-span steel box girder, the pushing mode, reasonable arrangement of temporary piers and structural form of temporary piers are systematically optimized and analyzed, and a two-way walking pushing scheme with a spacing of 60mbetween temporary pier and a 45 m long steel guide beam is determined. By studying the stress and deformation of temporary piers, steel box girder and guide beams under the key calculation conditions of pushing and analyzing the local stress of the steel box girder under the maximum reaction force, it is indicated that the structural strength and stiffness of temporary piers, steel box girder and guide beams meet the requirements, and the structure is in a state of reasonable stress, safe and controllable. After the pushing scheme and the intelligent monitoring platform are used to push the steel box girder into place, the measured linear of the steel box girder is basically consistent with the theoretical linear, and the maximum difference is 10mm, which realizes the high-precision pushing of the ultra-wide and long-span steel box girder [ABSTRACT FROM AUTHOR]

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To detect corrosion-related damages inside dim steel box girders, an improved U-net, Fusion-Attention-U-net (FAU-net), is proposed in this paper. A fusion module and a bottleneck-attention module are embedded in FAU-net for aggregating multi-level features and learning representative information, respectively. To realize this, a database of 300 damage images is built after data augmentation. Then, the proposed FAU-net is modified, trained, and validated. Based on the selected best training, the network achieves 98.61% pixel accuracy (PA), 92.73% mean pixel accuracy (MPA), 77.57% mean intersection over union (MIoU), and 97.52% frequency weighted intersection over union (FWIoU) on the validation set. Subsequently, the robustness and adaptability of the trained FAU-net are tested and compared with state-of-the-art networks. For a deep understanding, an ablation study is conducted to learn the contribution of main components in FAU-net. To establish the relationship between the detected damage pixel area and its actual physical area, photography experiments, and theoretical analyses are conducted to study the effect of three critical shooting variables: shooting distance, focal length, and shooting angle. Finally, a theoretical equation linking the pixel and physical areas is derived and further validated using the field-taken damage images under different shooting cases. The results show that the proposed method substantiates excellent performance to detect damage at the pixel level and measure damage areas accurately for the current samples. [ABSTRACT FROM AUTHOR]

A local finite element model was established for fatigue cracks to analyze the steel plate reinforcement mechanism. The steel plate reinforcement effect of damaged components was evaluated by extracting the stress of weld toe. The failure mode of steel plate reinforcement was analyzed for the adhesive layer stress. The stress intensity factor at the crack tip was extracted to study the steel plate reinforcement effect. By setting a variety of working conditions, the influence of reinforcement area, shape, thickness and other parameters on the reinforcement effect is studied. The research shows that the steel plate reinforcement can improve the stress level for the details of the arc notch-U rib weld of the diaphragm. The steel plate can be directly bonded to the reinforcement crack, and the reinforcement effect is reflected in replacing the damaged section to participate in the collaborative force of the component. The reinforcement range of steel plate has a great influence on the reinforcement effect. The reinforcement effect can be improved by extending the reinforcement parts along the direction of the connection weld. When short cracks are reinforced, the thickness of the plate is appropriately increased, and the reinforcement effect of setting cross stiffeners is inferior to that of equivalently increasing the thickness of the plate. [ABSTRACT FROM AUTHOR]

Metal magnetic memory testing (MMMT) is a nondestructive testing technique that can detect early signs of damage in components. Many scholars have studied the effect of uniaxial stress on the self-magnetic-leakage field (SMLF)'s strength. Nevertheless, there is still insufficient research on the combined action of bending and shear. We studied the law of distribution of the magnetic signal,   Δ H SF (y) , at different stress parts of a steel box girder and the quantitative relationship between the magnetic characteristic parameters and the external load. The results showed that the MMMT could accurately detect the early stress concentration zone (SCZ) and predict the final buckling zone of steel box girders. It could be judged that the corresponding parts of the steel box girder had entered the elastic-plastic working stage by the reverse change of the   Δ H SF (y) -F and   | H SF (y) | a   -F curve trends, this feature could be used as an early warning sign before the steel box girder was deformed or destroyed. The fitted   | H SF (y) | a v e   -F linear expression could be used as the expression between the magnetic signal and the shear capacity. All the evaluation methods were expected to provide a basis for effectively evaluating the stress state of steel box girders with the MMMT method. [ABSTRACT FROM AUTHOR]

Orthotropic anisotropic steel bridge panels are widely used in civil engineering due to their advantages of light deadweight, high ultimate bearing capacity, and wide range of applications. However, their fatigue problem is serious, and the fatigue-resistant design of the steel box girder diaphragm curved cutout is still difficult. In order to effectively predict the fatigue life of this typical fatigue-susceptible detail, a fatigue test of the specimen with curved notched segments of the diaphragm was carried out. ABAQUS 2016 version finite element analysis software was used to establish three kinds of finite element simplified models of the fatigue specimens with curved notches, and the laws of the influence of different notch radii on the fatigue life of the specimens were studied. Through the finite element solution of the three arc notch specimen models with different radii under the tensile load of 50 kN their respective principal stress distributions were obtained. The critical distance theory was introduced to analyze the characteristic stresses in the stress concentration area of the arc notch, and the point method and line method were used to calculate the characteristic stresses. The fatigue life prediction models of three kinds of notched components were established by combining the material fatigue limit and FE-safe life results. The results show that the point method is more conservative than the line method; no matter if the point method or the line method is used, the characteristic stress and the notch radius are inversely proportional to each other, and it is beneficial for the fatigue life of the structure to appropriately increase the notch radius. The fatigue prediction model of steel box girder diaphragms with curved notches based on the critical distance theory is of high accuracy, which is basically consistent with the test results, verifying the feasibility of the critical distance theory in the fatigue life prediction of notched specimens, and providing a reference for the fatigue life assessment of similar steel structures.

To improve the quality of the Hong Kong–Zhuhai–Macao Bridge paving project, a new paving layer material, Guss-mastic asphalt (GMA), was proposed in this paper by combining the advantages of two types of cast asphalt mixtures: mastic asphalt (MA) and Guss asphalt (GA). Based on the characteristics of GMA, to simulate its actual production process, this study developed a small-simulated cooker mixing equipment. Moreover, the flow degree, 60 ​°C dynamic stability, and impact toughness were proposed to be used to evaluate the construction and ease, high temperature stability, and fatigue resistance of GMA cast asphalt mixtures, respectively. Moreover, the quality control standards for GMA paving materials by indoor tests, field trial mix GMA material performance tests, and accelerated loading tests were finalized. The study showed that the developed simulated cooker yielded consistent mixing results in the same working environment as the engineering cooker device. Increasing the coarse aggregate incorporation rate, coarsening the mastic epure (ME) gradation composition, and using a smaller oil to stone ratio can reduce the flowability of the GMA materials to varying degrees. The four-point bending fatigue life and impact toughness of the different GMA materials are correlated well. A mobility of

Tuned mass dampers (TMDs) are widely used to control excessive wind-induced vibration in the box girders of long-span bridges. Although the optimal design of TMDs has been investigated abundantly in the last few years, the effectiveness of TMDs in use has not been thoroughly studied. In this paper, a method combining a machine learning (ML)–based approach is developed to evaluate the TMD effectiveness. The theoretical formulation and the flowchart of the method are firstly presented, which utilizes characteristics of TMD vibration amplitude, phase shift between TMDs and the bridge, and the mode resonant frequency component. Seven commonly used ML techniques, i.e., artificial neural network (ANN), decision tree (DT), k -nearest neighbors (KNN), random forest (RF), adaptive boosting (AdaBoost), gradient boosting regression tree (GBRT), and extreme gradient boosting (XGB), were adopted to generate the predictive models, and the structural health monitoring (SHM) data of the bridge were used as the training data. The wind properties and temperature were set as the input, and the TMD accelerations are set as the output. Meanwhile, the Shapley Additive Explanations (SHAP) was adopted to identify the influences of the input variables on the TMD's performance. The result indicated that the proposed method is reliable to evaluate the effectiveness of the TMDs, and it was shown that wind velocity is the most important parameter. BecauseTMDs are often widely used to control vibration in bridges, the proposed ML-based method can be used as an effective tool to assess and/or cross-check the effectiveness of TMDs. [ABSTRACT FROM AUTHOR]

In order to study the effect of cable damage on the self-vibration characteristics of steel box girder cable-stayed bridges with a single-cable plane and large cantilevers, a finite element model of the bridge was elaborated using the finite element software Midas/Civil to find out self-vibration characteristics of the cable-stayed bridge. The self-vibration characteristics of the bridge were also analysed for different damages to the cables and for different degrees of the damages to the cables. The structural health of a bridge can be diagnosed and assessed based on self-vibration characteristics of the studied structure. [ABSTRACT FROM AUTHOR]

To understand the actual vertical temperature gradient mode of steel box girder webs in cold regions, nearly 1.5 million data measured for over a year by a comprehensive temperature collection system of a steel box girder bridge in a cold region were used to verify the typicality of the temperature screening samples, and a cluster analysis was performed to verify the statistical symmetry of temperature at the symmetry points of webs on both sides of the bridge. One years' worth of daily temperature difference data were used to investigate the vertical temperature difference distribution on the web and to determine the probability distribution curve form. After selecting the extreme temperature difference samples, the standard vertical temperature difference of the web was calculated, and the actual vertical temperature gradient model of the steel box girder web was established. Results show that the probability distribution model of temperature at the symmetrical points of webs on both sides of the steel box girder was symmetric. The vertical temperature differences of the web demonstrated significant seasonal changes. The probability distribution of the positive and negative temperature differences can be described based on the sum of two Weibull distribution functions. The temperature gradients at all levels in the proposed vertical temperature gradient model were generally greater than the values indicated in the relevant specifications. [ABSTRACT FROM AUTHOR]

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With the development of the economy and transportation, more and more cross-sea bridges are appearing in people’s view. However, cross-sea bridges are not only subjected to repeated traffic loads but also to corrosion from the marine environment. In addition, the steel box girder deck plate is directly subjected to repeated vehicle loads, and its welded details are highly susceptible to fatigue damage and destruction, resulting in fatigue or corrosion damage to the welded top plate-U rib of the cross-sea steel box girder. This paper is based on fracture mechanics analysis methods and finite element simulation analysis, in order to establish the numerical analysis method of the welded top plate-U rib of the steel box girder deck plate fatigue, which is to take into account the coupling of the marine corrosive environment and fatigue cyclic loading, explore the welded top plate-U rib of the stress intensity factor, crack expansion, crack expansion life and total fatigue life of the welded details. Furthermore, the establishment of the welded top plate-U rib corrosion fatigue life assessment model is to explore the fatigue life of different top plate thicknesses. The results show that: the stress intensity factor along the crack front is symmetrically distributed, and with the increase in the crack expansion step, the corresponding stress intensity factor amplitude is also increasing; in addition, with the increase in the top plate thickness, fatigue crack expansion rate significantly reduced.