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Effectiveness of external prestressing in enhancing the non-ductile hanger failure mechanism in reinforced

《结构与土木工程前沿（英文）》 2024年 第18卷 第7期   页码 1050-1065 doi: 10.1007/s11709-024-1026-x

摘要： Recently, inverted T-beams have been used in reinforced concrete (RC) bridges to support transverse precast stringers. Inverted T-beams, contrary to practice with conventional beams, are loaded on the flanges upper surface. This loading configuration causes hanger failure due to the generation of vertical tensile stresses near the bottom of the web. The key purpose of this study is to investigate the efficiency of vertical external prestressing stainless-steel bars in mitigating non-ductile hanger failure in reinforced concrete inverted T-beams. An experimental study on six inverted-T beams, including two un-strengthened specimens, was carried out. The study showed that the value of the prestressing level had a considerable impact on the performance of hanger mechanism in relation to crack pattern, ultimate loads, cracking behavior, load–deflection, strains, and ductility. The experimental results indicated that the suggested method for strengthening inverted T-beams had efficacy in reducing the seriousness of the non-ductile hanger failure and resulted in a strength increase of up to 53% when compared to that of the un-strengthened specimen. Additionally, two analytical models for estimating the hanger capacity and the average crack width of the strengthened RC inverted T-beams were proposed. The models that were proposed exhibited a high degree of agreement with the experimental results.

关键词： RC bridges     inverted T-beams     strengthening     hanger failure     external prestressing    

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Numerical analysis on seismic response and failure mechanism of articulated pile−structure system in

《结构与土木工程前沿（英文）》 2024年 第18卷 第7期   页码 1117-1133 doi: 10.1007/s11709-024-0958-5

摘要： This study investigates the seismic response and failure mode of a pile−structure system in a liquefiable site by employing a numerical simulation model combined with the shaking-table results of a soil−pile−structure dynamic system. The pile and soil responses obtained from the numerical simulations agreed well with the experimental results. The slopes of the dynamic shear-stress–shear-strain hysteretic curves at different positions also exhibited a decreasing trend, indicating that the shear strength of the soil in all parts of the foundation decreased. The peak acceleration of the soil and pile was not clearly amplified in the saturated sand layer but appeared to be amplified in the top part. The maximum bending moments appeared in the middle and lower parts of the pile shaft; however, the shear forces at the corresponding positions were not large. It can be observed from the deformation mode of the pile-group foundation that a typical bending failure is caused by an excessive bending moment in the middle of the pile shaft if the link between the pile top and cap is articulated, and sufficient attention should be paid to the bending failure in the middle of the pile shaft.

关键词： numerical simulation     soil liquefaction     pile foundation     shaking-table experiment     seismic responses     failure model    

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A study on bearing characteristic and failure mechanism of thin-walled structure of a prefabricated subway

Lianjin TAO; Cheng SHI; Peng DING; Sicheng LI; Shang WU; Yan BAO

《结构与土木工程前沿（英文）》 2022年 第16卷 第3期   页码 359-377 doi: 10.1007/s11709-022-0816-2

摘要： In order to study the bearing performance of a new type of prefabricated subway station structure (PSSS), firstly, a three-dimensional finite element model of the PSSS was established to study the nonlinear mechanics and deformation performance. Secondly, the bearing mechanism of a PSSS was investigated in detail. Finally, the development law of damages to a thin-walled prefabricated component and the failure evolution mechanism of a PSSS were discussed. The results showed that this new type of the PSSS had good bearing capacity. The top arch structure was a three-hinged arch bearing system, and the enclosure structure and the substructure were respectively used as the horizontal and vertical support systems of the three-hinged arch structure to ensure the integrity and stability of the overall structure. Moreover, the tongue-and-groove joints could effectively transmit the internal force between the components and keep the components deformed in harmony. The rigidity degradation of the PSSS caused by the accumulation of damages to the spandrel, hance, arch foot, and enclosure structure was the main reason of its loss of bearing capacity. The existing thin-walled components design had significant advantages in weight reduction, concrete temperature control, components hoisting, transportation and assembly construction, which achieved a good balance between safety, usability and economy.

关键词： prefabricated subway station     thin-walled components     finite element analysis     bearing characteristic     failure mechanism    

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Bending failure performance of a shield tunnel segment based on full-scale test and numerical analysis

《结构与土木工程前沿（英文）》 2023年 第17卷 第7期   页码 1033-1046 doi: 10.1007/s11709-023-0973-y

摘要： This study focuses on the bending failure performance of a shield tunnel segment. A full-scale test was conducted to investigate deformation and failure characteristics. During the loading, the bending failure process can be divided into four stages: the elastic stage, working stage with cracks, failure stage, and ultimate stage. The characteristic loads between contiguous stages are the cracking, failure, and ultimate loads. A numerical model corresponding to the test was established using the elastoplastic damage constitutive model of concrete. After a comparative analysis of the simulation and test results, parametric studies were performed to discuss the influence of the reinforcement ratio and proportion of tensile longitudinal reinforcement on the bearing capacity. The results indicated that the change in the reinforcement ratio and the proportion of tensile longitudinal reinforcement had little effect on the cracking load but significantly influenced the failure and ultimate loads of the segment. It is suggested that in the reinforcement design of the subway segment, the reinforcement ratio and the proportion of tensile longitudinal reinforcement can be chosen in the range of 0.7%–1.2% and 49%–55%, respectively, allowing the segment to effectively use the reinforcement and exert the design strength, thereby improving the bearing capacity of the segment.

关键词： shield tunnel     bearing capacity     failure mechanism     segment reinforcement    

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Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield tunnels

《结构与土木工程前沿（英文）》 2023年 第17卷 第6期   页码 901-914 doi: 10.1007/s11709-023-0915-8

摘要： The integrity and bearing capacity of segment joints in shield tunnels are associated closely with the mechanical properties of the joints. This study focuses on the mechanical characteristics and mechanism of a bolted circumferential joint during the entire bearing process. Simplified analytical algorithms for four stress stages are established to describe the bearing behaviors of the joint under a compressive bending load. A height adjustment coefficient, α, for the outer concrete compression zone is introduced into a simplified analytical model. Factors affecting α are determined, and the degree of influence of these factors is investigated via orthogonal numerical simulations. The numerical results show that α can be specified as approximately 0.2 for most metro shield tunnels in China. Subsequently, a case study is performed to verify the rationality of the simplified theoretical analysis for the segment joint via numerical simulations and experiments. Using the proposed simplified analytical algorithms, a parametric investigation is conducted to discuss the factors affecting the ultimate compressive bending capacity of the joint. The method for optimizing the joint flexural stiffness is clarified. The results of this study can provide a theoretical basis for optimizing the design and prediciting the damage of bolted segment joints in shield tunnels.

关键词： shield tunnel     segment joint     joint structural model     failure mechanism    

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Integrated management of cardiac failure: the cardiac failure clinic

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《医学前沿（英文）》 2011年 第5卷 第1期   页码 20-25 doi: 10.1007/s11684-011-0106-1

摘要：

The prevalence of the risk factors and the risk of cardiac failure are both increasing in China. This might be the consequence of the changes of the life conditions (emigration to the urban areas, changes in the diet and life style, lack of physical exercise, etc.). The wide range of clinical presentations of cardiac failure (acute or chronic) and of therapeutic approaches (medical or surgical) makes necessary the integration within the same structure of the various experts involved in the diagnosis and the treatment of cardiac diseases. Technologic and human resources required to offer all the options represent a multifaceted commitment which should be focused optimally in dedicated centers. In these centers, collaboration should replace competition between the medical and the surgical cardiac specialists. Development of team work should permit to optimize the cost efficacy of the treatments. Most of all, such a structure will facilitate the translation of innovative therapies between the research centers and clinical facilities.

关键词： cardiac failure     cardiac transplantation     mechanical circulatory support    

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Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 623-642 doi: 10.1007/s11709-021-0726-8

摘要： In this study, gradual and sudden reduction methods were combined to simulate a progressive failure in notched composite plates using a macro mechanics approach. Using the presented method, a progressive failure is simulated based on a linear softening law prior to a catastrophic failure, and thereafter, sudden reduction methods are employed for modeling a progressive failure. This combination method significantly reduces the computational cost and is also capable of simultaneously predicting the first and last ply failures (LPFs) in composite plates. The proposed method is intended to predict the first ply failure (FPF), LPF, and dominant failure modes of carbon/epoxy and glass/epoxy notched composite plates. In addition, the effects of mechanical properties and different stacking sequences on the propagation of damage in notched composite plates were studied. The results of the presented method were compared with experimental data previously reported in the literature. By comparing the numerical and experimental data, it is revealed that the proposed method can accurately simulate the failure propagation in notched composite plates at a low computational cost.

关键词： progressive failure     notched composite plate     Hashin failure criterion     macro mechanics approach     finite element method    

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Experimental study of face passive failure features of a shallow shield tunnel in coastal backfill sand

《结构与土木工程前沿（英文）》 2024年 第18卷 第2期   页码 252-271 doi: 10.1007/s11709-024-1059-1

摘要： Face passive failure can severely damage existing structures and underground utilities during shallow shield tunneling, especially in coastal backfill sand. In this work, a series of laboratory model tests were developed and conducted to investigate such failure, for tunnels located at burial depth ratios for which C/D = 0.5, 0.8, 1, and 1.3. Support pressures, the evolution of failure processes, the failure modes, and the distribution of velocity fields were examined through model tests and numerical analyses. The support pressure in the tests first rose rapidly to the elastic limit and then gradually increased to the maximum value in all cases. The maximum support pressure decreased slightly in cases where C/D = 0.8, 1, and 1.3, but the rebound was insignificant where C/D = 0.5. In addition, the configuration of the failure mode with C/D = 0.5 showed a wedge-shaped arch, which was determined by the outcropping shear failure. The configuration of failure modes was composed of an arch and the inverted trapezoid when C/D = 0.8, 1, and 1.3, in which the mode was divided into lower and upper failure zones.

关键词： tunnel face stability     passive failure     model test     support pressure     failure mode    

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Overview on acute-on-chronic liver failure

null

《医学前沿（英文）》 2016年 第10卷 第1期   页码 1-17 doi: 10.1007/s11684-016-0439-x

摘要：

Liver failure (LF) is defined as severe dysfunction in hepatic synthesis, detoxification, and metabolism induced by various etiologies. Clinical presentation of LF typically includes severe jaundice, coagulation disorder, hepatic encephalopathy, and ascites. LF can be classified into acute LF, acute-on-chronic LF (ACLF), and chronic LF. ACLF has been demonstrated as a distinct syndrome with unique clinical presentation and outcomes. The severity, curability, and reversibility of ACLF have attracted considerable attention. Remarkable developments in ACLF-related conception, diagnostic criteria, pathogenesis, and therapy have been achieved. However, this disease, especially its diagnostic criteria, remains controversial. In this paper, we systemically reviewed the current understanding of ACLF from its definition, etiology, pathophysiology, pathology, and clinical presentation to management by thoroughly comparing important findings between east and west countries, as well as those from other regions. We also discussed the controversies, challenges, and needs for future studies to promote the standardization and optimization of the diagnosis and treatment for ACLF.

关键词： liver failure     chronic liver failure     acute-on-chronic liver failure     diagnosis     prognosis     treatment    

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Dynamic performance of submerged floating tunnel with different mooring styles subjected to anchor cable failure

《结构与土木工程前沿（英文）》 2023年 第17卷 第10期   页码 1443-1464 doi: 10.1007/s11709-023-0932-7

摘要： Submerged floating tunnels (SFTs) are novel structures for transportation across long- and deep-strait regions. Owing to severe wave and current excitation as well as the effects of underwater structures and corrosion, the risk of local anchor cable failure is high, which can result in the progressive failure of the entire structure. In this study, experimental and numerical investigations are conducted to analyze the dynamic behavior of an SFT with different mooring styles under local cable failure. A custom-designed cable failure device and the birth-and-death element method are used to simulate cable failure (i.e., progressive failure) via experiments and numerical simulation, respectively. A physical-scale segmental model of an SFT with different mooring styles under anchor cable failure is developed in this study. A segmental and entire-length mathematical model is developed using the ANSYS program to perform the numerical simulation. The results of the segmental numerical and experimental models indicate good agreement. The dynamic response of an SFT with different mooring styles under cable failure is comprehensively investigated by investigating the effects of key parameters (wave period, buoyant weight ratio, and cable failure mechanism). Moreover, the progressive failure of the SFT under cable failure is investigated via a segment model test and a numerical simulation of its entire length. The present study can serve as a reference for the safer designs of the SFT mooring style.

关键词： dynamic behaviors     submerged floating tunnel     cable failure     mooring style     progressive failure    

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淀粉基API胶合木胶接结构破坏模式及失效机理

时君友,徐文彪,王淑敏

《中国工程科学》 2014年 第16卷 第4期   页码 40-44

摘要：

以淀粉基水性高分子异氰酸酯（API）胶合木胶接结构为研究对象，以胶接的压缩剪切强度为评估指标，通过加速湿热老化试验对胶接结构的破坏模式和失效机理进行了研究。结果表明：胶接结构的断裂性质为韧性断裂，且随着老化时间的增加，其破坏模式为由内聚破坏向内聚破坏+界面破坏转变。在湿热老化试验前期温度对压缩剪切试样性能起主要作用，在老化后期湿度起主要作用。

关键词： 胶接结构     加速湿热老化     断裂性质     破坏模式    

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Durability of plasma-sprayed Cr3C2-NiCr coatings under rolling contact conditions

Xiancheng ZHANG, Fuzhen XUAN, Shantung TU, Binshi XU, Yixiong WU

《机械工程前沿（英文）》 2011年 第6卷 第1期   页码 118-135 doi: 10.1007/s11465-011-0127-0

摘要：

The aim of this paper was to address the rolling contact fatigue (RCF) failure mechanisms of plasma-sprayed Cr3C2-NiCr coatings under different tribological conditions of contact stress. Weibull distribution plots of fatigue lives of the coated specimens at different contact stresses were obtained. The failure modes of coatings were identified on the basis of wore surface observations of the failed coatings. Results showed that the RCF failure modes can be classified into four main categories, i.e., surface abrasion, spalling, cohesive delamination, and interfacial delamination. The probabilities of the surface abrasion and spalling type failures were relatively high at low contact stress. When the coatings were subjected to abrasion and spalling type failures, the failure of the coating was depended on the microstrcture of the coating. The stress concentration near the micro-defects in the coating may be the may reason for the formation of spall. The coatings were prone to fail in delamination under higher contact stresses. However, the delamination of coating may be related to distribution of shear stress amplitude within coating. The location of maximum shear stress amplitude can be used as a key parameter to predict the initiation of subsurface cracks within coating in rolling contact.

关键词： rolling contact fatigue     coating     Weibull distribution     failure mode     mechanism    

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Unified method for typical gear failure modeling and stiffness calculation based on the matrix equation

《机械工程前沿（英文）》 2024年 第19卷 第3期 doi: 10.1007/s11465-024-0794-2

摘要： The failure types in gear systems vary, with typical ones mainly including pitting, cracking, wear, and broken teeth. Different modeling and stiffness calculation methods have been developed for various gear failure types. A unified method for typical gear failure modeling and stiffness calculation is introduced in this study by considering the deviations in the time-varying meshing stiffness (TVMS) of faulty gears resulting from the use of different methods. Specifically, a gear tooth is discretized into a large number of microelements expressed with a matrix, and unified models of typical gear failures are built by adjusting the values of the matrix microelements. The values and positions of the microelements in the tooth failure model matrix have the same physical meaning as the parameter variables in the potential energy method (PEM), so the matrix-based failure model can be perfectly matched with PEM. Afterward, a unified method for TVMS is established. Modeling of healthy and faulty gears with pitting, wear, crack, and broken tooth is performed with the matrix equation, and the corresponding TVMS values are calculated by incorporating the matrix models with PEM. On the basis of the results, the mechanism of typical fault types that affect TVMS is analyzed, and the conclusions are verified through the finite element method. The developed unified method is a promising technique for studying the dynamic response characteristics of gear systems with different failure types because of its superiority in eliminating stiffness deviations.

关键词： gears     matrix equation     failure modeling     TVMS calculation     unified method    

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Progressive collapse of 2D reinforced concrete structures under sudden column removal

El Houcine MOURID, Said MAMOURI, Adnan IBRAHIMBEGOVIC

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1387-1402 doi: 10.1007/s11709-020-0645-0

摘要： Once a column in building is removed due to gas explosion, vehicle impact, terrorist attack, earthquake or any natural disaster, the loading supported by removed column transfers to neighboring structural elements. If these elements are unable to resist the supplementary loading, they continue to fail, which leads to progressive collapse of building. In this paper, an efficient strategy to model and simulate the progressive collapse of multi-story reinforced concrete structure under sudden column removal is presented. The strategy is subdivided into several connected steps including failure mechanism creation, MBS dynamic analysis and dynamic contact simulation, the latter is solved by using conserving/decaying scheme to handle the stiff nonlinear dynamic equations. The effect of gravity loads, structure-ground contact, and structure-structure contact are accounted for as well. The main novelty in this study consists in the introduction of failure function, and the proper manner to control the mechanism creation of a frame until its total failure. Moreover, this contribution pertains to a very thorough investigation of progressive collapse of the structure under sudden column removal. The proposed methodology is applied to a six-story frame, and many different progressive collapse scenarios are investigated. The results illustrate the efficiency of the proposed strategy.

关键词： failure mechanism     MBS dynamic analysis     gravity loads     structure-ground contact     structure-structure contact     energy conserving/decaying scheme    

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LSSVM-based approach for refining soil failure criteria and calculating safety factor of slopes

Shiguo XIAO; Shaohong LI

《结构与土木工程前沿（英文）》 2022年 第16卷 第7期   页码 871-881 doi: 10.1007/s11709-022-0863-8

摘要： The failure criteria of practical soil mass are very complex, and have significant influence on the safety factor of slope stability. The Coulomb strength criterion and the power-law failure criterion are classically simplified. Each one has limited applicability owing to the noticeable difference between calculated predictions and actual results in some cases. In the work reported here, an analysis method based on the least square support vector machine (LSSVM), a machine learning model, is purposefully provided to establish a complex nonlinear failure criterion via iteration computation based on strength test data of the soil, which is of more extensive applicability to many problems of slope stability. In particular, three evaluation indexes including coefficient of determination, mean absolute percentage error, and mean square error indicate that fitting precision of the machine learning-based failure criterion is better than those of the linear Coulomb criterion and nonlinear power-law criterion. Based on the proposed LSSVM approach to determine the failure criterion, the limit equilibrium method can be used to calculate the safety factor of three-dimensional slope stability. Analysis of results of the safety factor of two three-dimensional homogeneous slopes shows that the maximum relative errors between the proposed approach and the linear failure criterion-based method and the power-law failure criterion-based method are about 12% and 7%, respectively.

关键词： slope stability     safety factor     failure criterion     least square support vector machine    

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标题 作者 时间 类型 操作

Effectiveness of external prestressing in enhancing the non-ductile hanger failure mechanism in reinforced

期刊论文

Numerical analysis on seismic response and failure mechanism of articulated pile−structure system in

期刊论文

A study on bearing characteristic and failure mechanism of thin-walled structure of a prefabricated subway

Lianjin TAO; Cheng SHI; Peng DING; Sicheng LI; Shang WU; Yan BAO

期刊论文

Bending failure performance of a shield tunnel segment based on full-scale test and numerical analysis

期刊论文

Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield tunnels

期刊论文

Integrated management of cardiac failure: the cardiac failure clinic

null

期刊论文

Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

期刊论文

Experimental study of face passive failure features of a shallow shield tunnel in coastal backfill sand

期刊论文

Overview on acute-on-chronic liver failure

null

期刊论文

Dynamic performance of submerged floating tunnel with different mooring styles subjected to anchor cable failure

期刊论文

淀粉基API胶合木胶接结构破坏模式及失效机理

时君友,徐文彪,王淑敏

期刊论文

Durability of plasma-sprayed Cr3C2-NiCr coatings under rolling contact conditions

Xiancheng ZHANG, Fuzhen XUAN, Shantung TU, Binshi XU, Yixiong WU

期刊论文

Unified method for typical gear failure modeling and stiffness calculation based on the matrix equation

期刊论文

Progressive collapse of 2D reinforced concrete structures under sudden column removal

El Houcine MOURID, Said MAMOURI, Adnan IBRAHIMBEGOVIC

期刊论文

LSSVM-based approach for refining soil failure criteria and calculating safety factor of slopes

Shiguo XIAO; Shaohong LI

期刊论文