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Causes and statistical characteristics of bridge failures:A review

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Journal of Traffic and Transportation Engineering(English Edition) 2022年第3期9卷 388-406页

作者： Guojing Zhang yongjian liu Jiang liu Shiyong Lan Jian Yang School of Highway Chang'an UniversityXian 710064China Research Center of Highway Large Structure Engineering on Safety of Ministry of Education Chang'an UniversityXi'an 710064China AECOM New YorkNY 10158USA

Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than70% of the bridge failures. Causes of bridge failures are closely related to regional economy,structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications.

关键词： Bridge engineering Bridge failure Statistical characteristic Failure cause Case study

Mechanical behavior of concrete-filled rectangular steel tubular composite truss bridge in the negative moment region

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第5期8卷 795-814页

作者： Beichen Pu Xuhong Zhou yongjian liu Bin liu Lei Jiang School of Highway Chang'an UniversityXi'an 710064China CSCEC AECOM Consultants Co. Ltd.Lanzhou 730000China School of Civil Engineering Chongqing UniversityChongqing 400045China

Concrete-filled rectangular steel tubular(CFRST)composite truss bridge is a new type of structure composed of a CFRST truss and concrete deck *** new type of bridge has the advantages of high structural force-transferring efficiency,rapid assembly construction speed and excellent total life cycle,which meets the construction concept of green,recyclable and sustainable *** to the broad application prospects,experiment on the flexural behavior of CFRST composite truss bridge in the negative moment region was reported by authors *** paper thus presents a finite element analysis(FEA)modelling verified by the reported test data to further investigate the detailed analytical behavior of this *** structural response and failure mechanism of CFRST composite truss beam in the negative moment region are *** addition,the important structural design parameters on the flexural performance of the CFRST composite truss beam are also investigated,including the height to span ratio,the brace-to-chord wall thickness ratio,the reinforcement ratio of steel reinforcements and prestressed tendons and the strength grade of concrete infill in ***,the reasonable structural design parameters range are proposed for the optimum design of the CFRST composite truss bridge.

关键词： Bridge engineering CFRST composite truss bridge Concrete deck slab Recyclable Failure mechanism Design parameters

Slope stability analysis based on big data and convolutional neural network

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Frontiers of Structural and Civil Engineering 2022年第7期16卷 882-895页

作者： Yangpan FU Mansheng LIN You ZHANG Gongfa CHEN yongjian liu School of Civil and Transportation Engineering Guangdong University of TechnologyGuangzhou 510006China

The Limit Equilibrium Method(LEM)is commonly used in traditional slope stability analyses,but it is time-consuming and *** to its complexity and nonlinearity involved in the evaluation process,it cannot provide a quick stability estimation when facing a large number of *** this case,the convolutional neural network(CNN)provides a better alternative.A CNN model can process data quickly and complete a large amount of data analysis in a specific situation,while it needs a large number of training *** is difficult to get enough slope data samples in practical *** study proposes a slope database generation method based on the *** were amplified from 40 typical slopes,and a sample database consisting of 20000 slope samples was *** sample database for slopes covered a wide range of slope geometries and soil layers’physical and mechanical *** CNN trained with this sample database was then applied to the stability prediction of 15 real slopes to test the accuracy of the CNN *** results show that the slope stability prediction method based on the CNN does not need complex calculation but only needs to provide the slope coordinate information and physical and mechanical parameters of the soil layers,and it can quickly obtain the safety factor and stability state of the ***,the prediction accuracy of the CNN trained by the sample database for slope stability analysis reaches more than 99%,and the comparisons with the BP neural network show that the CNN has significant superiority in slope stability ***,the CNN can predict the safety factor of real *** particular,the combination of typical actual slopes and generated slope data provides enough training and testing samples for the CNN,which improves the prediction speed and practicability of the CNN-based evaluation method in engineering practice.

关键词： slope stability limit equilibrium method convolutional neural network database for slopes big data

Investigate of in situ sludge reduction in sequencing batch biofilm reactor:Performances,mechanisms and comparison of different carriers

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Frontiers of Environmental Science & Engineering 2018年第5期12卷 131-145页

作者： Yonglei Wang Baozhen liu Kefeng Zhang yongjian liu Xuexin Xu Junqi Jia School of Municipal and Environmental Engineering Shandong Jianzhu UniversityJinan 250101China Co-Innovation Center of Green Building Jinan 250101China Shandong Province City Water Supply and Drainage Water Quality Monitoring Center Jinan 250101China Shandong Huaihe River Basin Water Conservancy Administration Planning and Design Institute Jinan 250101China

Biofilm is an effective simultaneous denitrification and in situ sludge reduction system,and the characteristics of different biofilm carrier have important implications for biofilm growth and in situ sludge *** this study,the performance and mechanism of in situ sludge reduction were compared between FSC-SBBR and SC-SBBR with constructed by composite floating spherical carriers(FSC)and multi-faceted polyethylene suspension carriers(SC),*** variation of EPS concentration indicated that the biofilm formation of FSC was faster than *** with SCSBBR,the FSC-SBBR yielded 0.16 g MLSS/g COD,almost 27.27%less *** average removal rates of COD and NH_(4)^(+)-N were 93.39% and 96.66%,respectively,which were 5.21% and 1.43% higher than the average removal rate of *** of the mechanisms of sludge reduction revealed that,energy uncoupling metabolism and sludge decay were the main factors for sludge reduction inducing 43.13%and 49.65%less sludge,respectively,in *** fluorescence spectroscopy and SUVA analysis showed that the hydrolytic capacity of biofilm attached in FSC was stronger than those of SC,and the hydrolysis of EPS released more DOM contributed to lysis-cryptic growth *** additional,Bacteroidetes and Mizugakiibacter associated with sludge reduction were the dominant phylum and genus in ***,the effect of simultaneous in situ sludge reduction and pollutant removal in FSC-SBBR was better.

关键词： In situ sludge reduction Biofilm Composite floating spherical carriers Microbial community SBBR

Adaptive ANCF method and its application in planar flexible cables

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Acta Mechanica Sinica 2018年第1期34卷 199-213页

作者： Yue Zhang Cheng Wei Yang Zhao Chunlin Tan yongjian liu Department of Aerospace Engineering Harbin Institute of Technology Institute of Spacecraft System Engineering CAST

In the conventional absolute nodal coordinate formulation(ANCF), the model is pre-meshed, the number,distribution and type of elements are unchangeable during the simulation. In addition, the deformations of a flexible body are space-varying and time-varying, one cannot predict when, where, and how the deformations will occur. Therefore, in order to obtain a satisfactory accuracy during the whole simulation, the model is usually densely meshed, but it will result in a loss of computational efficiency. In this study,an adaptive absolute nodal coordinate formulation(AANCF)is proposed to optimize the accuracy and efficiency of flexible dynamics. The movement features of flexible bodies are analyzed, and the conventional and adaptive ANCF methods are compared. Then the adaptive computation strategy is presented. The discretization errors come from the inability of interpolation functions of individual elements to capture the complexity of the exact solution, so the mesh can be adaptively optimized by changing the element sizes or the orders of interpolation functions during dynamic computation. Important issues of AANCF, including error estimation,mesh updating, and performance of the AANCF model, are analyzed and discussed in detail. A theoretical model of a planar AANCF cable is presented, where the strategies of dividing and merging elements are discussed. Moreover, the continuity of dynamic variables is deduced, and the mean factors that affect the continuity are obtained, which is very important for the subsequent continuity optimization. Thesimulation results indicate that the distribution of elements varies with time and space, and the elements are denser in large-deformed domains. The AANCF model improved the computational accuracy and efficiency, but the system energy is discontinuous when the elements are merged. Therefore,a continuity-optimized AANCF model is given based on the previous continuity analysis, the results show that the accuracy and continuity of

关键词： Absolute nodal coordinate formulation Adaptive computation Continuity Accuracy Efficiency

Numerical simulation investigation on hydration heat temperature and early cracking risk of concrete box girder in cold regions

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Journal of Traffic and Transportation Engineering(English Edition) 2023年第4期10卷 697-720页

作者： Shi Han yongjian liu Yi Lyu Jiang liu Ning Zhang School of Highway Chang'an UniversityXian 710064China Qinghai Transportation Engineering Technical Service Center Xining 810008China School of Civil Engineering Chongqing UniversityChongqing 400045China College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China

The temperature change caused by hydration leads to early-age cracking in concrete box *** early-age cracking risk is further improved with low air temperature and large daily temperature difference,especially in Northwest *** fill this gap,a temperature experiment and numerical simulation were performed on an actual concrete box girder segment in Northwest *** temperature field,thermal stress and cracking risk were analyzed using evolution curves,distribution curves and *** key parameters that influence the hydration heat temperature,including the cement hydration heat release,cement content,height-width ratio of web,initial temperature,convective coefficient of top plate surface,were *** anti-cracking case based on parameters analysis was put *** results indicated that the temperature evolution can be divided into three stages:warming,cooling and environment significantly *** the thickness of each plate,temperature distributed is single peak in the *** the width or height,temperature distributed is double peaks at axillary position for the top and bottom plates,and single peak in center for the *** axillary position and web have high thermal stress and significant cracking *** temperature difference of each plate,and the early-age cracking risk can be reduced by effectively adjusting the key *** these,the former two parameters are the most significant *** maximum cracking risk can be decreased by 15.7%for every 50 kJ/kg hydration heat *** maximum cracking risk can be decreased by 13.1%for every 50 kg/m^(3)cement content reduction.

关键词： Bridge engineering Concrete boxgirder Hydration heat Cold region Temperature action Thermal stress

Genetic diversity and its seasonal variation of Jiaozhou Bay phytoplankton determined by rbcL gene sequencing

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Acta Oceanologica Sinica 2006年第2期25卷 125-134页

作者： liu yongjian YANG Guanpin* GUAN Xiaojing MEN Rongxin College of Marine Life Sciences Ocean University of ChinaQingdao 266003China

Ribulose-1, 5-bisphosphate carboxynase/oxygenase large subunit gene (rbcL) of Jiaozhou Bay phytoplankton was amplified from spring, summer and autumn surface seawater DNAs and cloned respectively. About 50 clones were randomly selected from each library and sequenced. If identical amino acid sequences are considered as the same operational taxonomy unit (OTU), 61 OTUs are identified according to inferred amino acid sequences, among them, 21 from spring seawater, 15 from summer seawater and 25 from autumn seawater. Shannon index calculated from OTU abundances reflects the genetic diversity of a community. The indexes of spring, summer and autumn surface seawater phytoplankton are 2.69, 2.44 and 2.76 respectively, indicating that phytoplankton genetic diversity of autumn seawater is the richest. Seasonal variation ofphytoplankton community is significant; the community compositions of three seasons are almost completely different except for the two OTUs shared by summer and autumn. Surface seawater phytoplankton communities are possibly metacommunities different spatially and temporally.

关键词： phytoplankton ribulose-1, 5-bisphosphate carboxynase/oxygenase large subunit gene (rbcL) community structure seasonal variation

Temperature action and effect of concrete-filled steel tubular bridges:A review

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第2期7卷 174-191页

作者： Jiang liu yongjian liu Chenyu Zhang Qiuhong Zhao Yi Lyu Lei Jiang School of Highway Chang'an UniversityXi'an 710064China Department of Civil Engineering Tianjin UniversityTianjin 300072China Department of Civil Engineering Queen's UniversityKingstonON K7L 3N6Canada

Concrete-filled steel tube(CFST)has been widely applied in bridges due to its excellent structural and constructional *** CFST bridges,temperature action is not only an important but also a special load that must be considered in bridge design,construction and structural *** paper presents an overview on current researches of the temperature action and effect of CFST *** historical and spatial characteristics as well as corresponding influencing factors of temperature distributions are summarized,and classifications of temperature actions are also *** show that in-depth investigations of the contributions of temperature influencing factors can help to effectively reduce the adverse temperature effects on CFST bridges in the design *** to the lack of long-term measurements and insufficient use of historical meteorological data,research on the representative value along with correlation analysis of CFST temperature actions and meteorological parameters have to be further carried *** the meanwhile,a decomposition method of temperature distribution is proposed based on structural effects of CFST bridges in this *** decomposed temperature actions can be used for more accurate effect calculation than traditional temperature action classification method,especially for CFST truss *** last,specific temperature action patterns still need to be investigated in some of the special problems,such as longitudinal temperature differences along the CFST arch rib and thermal debonding in the CFST *** investigations are required on the accurate simulation of temperature distribution of CFST bridges considering the shading effects of components and terrain.

关键词： Bridge engineering CFST bridge Temperature action Temperature effect Thermal debonding

Degree of bending of concrete-filled rectangular hollow section K-joints under balanced-axial loadings

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Frontiers of Structural and Civil Engineering 2022年第4期16卷 461-477页

作者： Rui ZHAO yongjian liu Lei JIANG Yisheng FU Yadong ZHAO Xindong ZHAO School of Highway Chang’an UniversityXi’an 710064China Research Center of Highway Large Structure Engineering on Safety of Ministry of Education Xi’an 710064China

It has been found that the fatigue life of tubular joints is not only determined by the hot spot stress,but also by the stress distribution through the tube thickness represented as the degree of bending(DoB).Consequently,the DoB value should be determined to improve the accuracy of fatigue assessment for both stress-life curve and fracture mechanics ***,no DoB parametric formula is available for concrete-filled rectangular hollow section(CFRHS)K-joints,despite their wide use in bridge ***,a robust finite element(FE)analysis was carried out to calculate the DoB of CFRHS K-joints under balanced-axial *** FE model was developed and verified against a test result to ensure accuracy.A comprehensive parametric study including 190 models,was conducted to establish the relationships between the DoBs and four specific *** on the numerical results,design equations to predict DoBs for CFRHS K-joints were proposed through multiple regression analysis.A reduction of 37.17%was discovered in the DoB,resulting in a decrease of 66.85%in the fatigue ***,the CFRHS K-joints with same hot spot stresses,may have completely different fatigue lives due to the different DoBs.

关键词： fatigue assessment K-joint design equations degree of bending fracture mechanics