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Crack detection for wading-concrete structures using water irrigation and electric heating

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 368-377 doi: 10.1007/s11709-022-0926-x

摘要: Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures. The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering. The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack. Based on this, a novel crack-identification method for underwater concrete structures is presented. This method uses water irrigation to generate seepage at the interface of a crack; then, the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack. Crack information can be identified by monitoring the cooling law and leakage flow near cracks. The proposed mobile crack-monitoring system consists of a heating system, temperature-measurement system, and irrigation system. A series of tests was conducted on a reinforced-concrete beam using this system. The crack-discrimination index ψ was defined, according to the subsection characteristics of the heat-source cooling curve. The effects of the crack width, leakage flow, and relative positions of the heat source and crack on ψ were studied. The results showed that the distribution characteristics of ψ along the monitoring line could accurately locate the crack, but not quantify the crack width. However, the leakage flow is sensitive to the crack width and can be used to identify it.

关键词: structural health monitoring     underwater concrete structure     fiber Bragg grating     crack detection     temperature tracer method    

Performance of steel bridge deck pavement structure with ultra high performance concrete based on resin

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 895-904 doi: 10.1007/s11709-021-0759-z

摘要: This research investigated a pavement system on steel bridge decks that use epoxy resin (EP) bonded ultra-high performance concrete (UHPC). Through FEM analysis and static and dynamic bending fatigue tests of the composite structure, the influences of the interface of the pavement layer, reinforcement, and different paving materials on the structural performance were compared and analyzed. The results show that the resin bonded UHPC pavement structure can reduce the weld strain in the steel plate by about 32% and the relative deflection between ribs by about 52% under standard axial load conditions compared to traditional pavements. The EP bonding layer can nearly double the drawing strength of the pavement interface from 1.3 MPa, and improve the bending resistance of the UHPC structure on steel bridge decks by about 50%; the bending resistance of reinforced UHPC structures is twice that of unreinforced UHPC structure, and the dynamic deflection of the UHPC pavement structure increases exponentially with increasing fatigue load. The fatigue life is about 1.2 × 107 cycles under a fixed force of 9 kN and a dynamic deflection of 0.35 mm, which meets the requirements for fatigue performance of pavements on steel bridge decks under traffic conditions of large flow and heavy load.

关键词: steel bridge deck pavement     ultra-high-performance concrete     epoxy resin     composite structure     bending fatigue performance    

Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

《结构与土木工程前沿(英文)》 2023年 第17卷 第5期   页码 669-685 doi: 10.1007/s11709-023-0963-0

摘要: Owing to advancement in advanced manufacturing technology, the reinforcement design of concrete structures has become an important topic in structural engineering. Based on bi-directional evolutionary structural optimization (BESO), a new approach is developed in this study to optimize the reinforcement layout in steel-reinforced concrete (SRC) structures. This approach combines a minimum compliance objective function with a hybrid truss-continuum model. Furthermore, a modified bi-directional evolutionary structural optimization (M-BESO) method is proposed to control the level of tensile stress in concrete. To fully utilize the tensile strength of steel and the compressive strength of concrete, the optimization sensitivity of steel in a concrete–steel composite is integrated with the average normal stress of a neighboring concrete. To demonstrate the effectiveness of the proposed procedures, reinforcement layout optimizations of a simply supported beam, a corbel, and a wall with a window are conducted. Clear steel trajectories of SRC structures can be obtained using both methods. The area of ​​critical tensile stress in concrete yielded by the M-BESO is more than 40% lower than that yielded by the uniform design and BESO. Hence, the M-BESO facilitates a fully digital workflow that can be extremely effective for improving the design of steel reinforcements in concrete structures.

关键词: bi-directional evolutionary structural optimization     steel-reinforced concrete     concrete stress     reinforcement method     hybrid model    

水下盾构法铁路隧道管片衬砌结构的原型加载试验研究

何川,封坤,晏启祥,齐春

《中国工程科学》 2012年 第14卷 第10期   页码 65-72

摘要:

针对我国第一条水下铁路盾构法隧道——狮子洋隧道,采用“多功能盾构隧道结构体试验系统”装置原型管片衬砌结构,在通缝和错缝不同的拼装方式下进行了原型结构加载试验,对其结构力学性能进行深入探讨。试验结果表明,不同水压条件下管片衬砌结构力学特征不同,尤其是当结构开裂后,高水压对于结构内力与形变的发展有明显的减缓作用。狮子洋隧道采用的榫式接头管片结构在通缝与错缝拼装下的破坏特征不同,通缝拼装时结构在高水压条件下纵缝附近区域易发生局部剪切破坏,该研究成果可为同类工程的设计提供有价值的参考。

关键词: 水下盾构法铁路隧道     管片衬砌结构     原型试验     榫式接头     破坏特征    

Seismic performance of prestressed concrete stand structure supporting retractable steel roof

Yiyi CHEN, Dazhao ZHANG, Weichen XUE, Wensheng LU

《结构与土木工程前沿(英文)》 2009年 第3卷 第2期   页码 117-124 doi: 10.1007/s11709-009-0024-3

摘要: The seismic behavior of a structural system composed of pre-stressed concrete stand supporting a retractable steel roof was studied, which is typically based on the prototype of engineering project of Shanghai Qizhong Tennis Center. By elasto-plastic finite element analysis and shaking table test, the following were investigated: the effects of roof configurations in opening and closing, the effect of pre-stress on the structural seismic response, and the failure mechanism of the spatial stand frame systems featured with circularly arranged columns and inverse-cone type stands. It was found that the roof status has great effect on the natural period, vibration modes, and seismic response of the whole structure, the stand response to horizontal seismic excitation is stronger in roof opening configuration than in closing state, and the response mode is dominantly translational rather than rotational, though the stand is characterized by its fundamentally torsional vibration mode. The study indicated that the pre-stressed inverse-cone stands can keep the system from global side-sway collapse under gravity loads, even in the case that most columns loose moment capacity.

关键词: retractable steel roof     prestressed concrete     seismic performance     failure mode     inelastic response     shaking table test    

Nonlinear elastic model for compacted clay concrete interface

R. R. SHAKIR, Jungao ZHU

《结构与土木工程前沿(英文)》 2009年 第3卷 第2期   页码 187-194 doi: 10.1007/s11709-009-0033-2

摘要: In this paper, a nonlinear elastic model was developed to simulate the behavior of compacted clay concrete interface (CCCI) based on the principle of transition mechanism failure (TMF). A number of simple shear tests were conducted on CCCI to demonstrate different failure mechanisms; i.e., sliding failure and deformation failure. The clay soil used in the test was collected from the “Shuang Jang Kou” earth rockfill dam project. It was found that the behavior of the interface depends on the critical water contents by which two failure mechanisms can be recognized. Mathematical relations were proposed between the shear at failure and water content in addition to the transition mechanism indicator. The mathematical relations were then incorporated into the interface model. The performance of the model is verified with the experimental results. The verification shows that the proposed model is capable of predicting the interface shear stress versus the total shear displacement very well.

关键词: interface modeling     friction     soil structure interface     soil structure interaction     simple shear test    

Automated classification of civil structure defects based on convolutional neural network

Pierclaudio SAVINO, Francesco TONDOLO

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 305-317 doi: 10.1007/s11709-021-0725-9

摘要: Today, the most commonly used civil infrastructure inspection method is based on a visual assessment conducted by certified inspectors following prescribed protocols. However, the increase in aggressive environmental and load conditions, coupled with the achievement of many structures of the life-cycle end, has highlighted the need to automate damage identification and satisfy the number of structures that need to be inspected. To overcome this challenge, this paper presents a method for automating concrete damage classification using a deep convolutional neural network. The convolutional neural network was designed after an experimental investigation of a wide number of pretrained networks, applying the transfer-learning technique. Training and validation were conducted using a database built with 1352 images balanced between “undamaged”, “cracked”, and “delaminated” concrete surfaces. To increase the network robustness compared to images in real-world situations, different image configurations have been collected from the Internet and on-field bridge inspections. The GoogLeNet model, with the highest validation accuracy of approximately 94%, was selected as the most suitable network for concrete damage classification. The results confirm that the proposed model can correctly classify images from real concrete surfaces of bridges, tunnels, and pavement, resulting in an effective alternative to the current visual inspection techniques.

关键词: concrete structure     infrastructures     visual inspection     convolutional neural network     artificial intelligence    

Turbidity-adaptive underwater image enhancement method using image fusion

《机械工程前沿(英文)》 2022年 第17卷 第3期 doi: 10.1007/s11465-021-0669-8

摘要: Clear, correct imaging is a prerequisite for underwater operations. In real freshwater environment including rivers and lakes, the water bodies are usually turbid and dynamic, which brings extra troubles to quality of imaging due to color deviation and suspended particulate. Most of the existing underwater imaging methods focus on relatively clear underwater environment, it is uncertain that if those methods can work well in turbid and dynamic underwater environments. In this paper, we propose a turbidity-adaptive underwater image enhancement method. To deal with attenuation and scattering of varying degree, the turbidity is detected by the histogram of images. Based on the detection result, different image enhancement strategies are designed to deal with the problem of color deviation and blurring. The proposed method is verified by an underwater image dataset captured in real underwater environment. The result is evaluated by image metrics including structure similarity index measure, underwater color image quality evaluation metric, and speeded-up robust features. Test results exhibit that the method can correct the color deviation and improve the quality of underwater images.

关键词: turbidity     underwater image enhancement     image fusion     underwater robots     visibility    

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    

中国钢筋混凝土空间网格结构新体系的开拓与发展(下)

马克俭,张华刚,肖建春,卢亚琴

《中国工程科学》 2008年 第10卷 第8期   页码 22-34

摘要:

钢筋混凝土空间网格结构包括平板型的空腹网架结构、空腹夹层板结构、空腹双重网格结构、现浇混凝土空心大板楼盖结构。这些新型结构体系从20世纪80年代至今在跨度18~32 m公共建筑的屋盖和楼盖应用达100多万平方米,取得很好的社会与经济效益。有的已编制了相应的技术规程。我们研制了将钢筋混凝土空腹夹层板单向弯曲形成的钢筋混凝土空腹夹层网壳和网拱结构,双向弯曲形成的钢筋混凝土空腹夹层双曲扁网壳结构。这些拥有我国自主知识产权的空间网格结构新体系,均具有自身的特点和对建筑物的适应性,文章将按研制时间先后逐一介绍。其结构的“安全、合理、经济、先进”性,则通过工程实例予以剖析。

关键词: 钢筋混凝土     空腹夹层板     现浇混凝土空心大板     网架结构     网壳结构    

Research on recycled concrete and its utilization in building structures in China

Jianzhuang XIAO, Tao DING

《结构与土木工程前沿(英文)》 2013年 第7卷 第3期   页码 215-226 doi: 10.1007/s11709-013-0212-z

摘要: Large quantities of construction and demolition (C&D) building waste are being generated as a result of rapid urbanization and natural disasters in China. An increasing awareness of environmental protection is escalating C&D waste disposal concerns. This paper presents a brief introduction to current shaking table test research in China on structures built with recycled aggregate concrete (RAC). Test structures include a cast-in situ frame model, a precast frame model and a block masonry building. The test results prove that it is feasible to use RAC as a structural material in seismic areas, with recommended modifications and proper design, especially in low-rise structures. This paper also presents several successful applications of RAC in civil and structural engineering projects in China, which will serve to promote RAC as a global ecological structural material.

关键词: recycled aggregate concrete (RAC)     structural material     shaking table tests     building structure    

Behavior of compacted clay-concrete interface

R. R .SHAKIR, Jungao ZHU

《结构与土木工程前沿(英文)》 2009年 第3卷 第1期   页码 85-92 doi: 10.1007/s11709-009-0013-6

摘要: Tests of interface between compacted clay and concrete were conducted systematically using interface simple shear test apparatus. The samples, having same dry density with different water content ratio, were prepared. Two types of concrete with different surface roughness, i.e., relatively smooth and relatively rough surface roughness, were also prepared. The main objectives of this paper are to show the effect of water content, normal stress and rough surface on the shear stress-shear displacement relationship of clay-concrete interface. The following were concluded in this study: 1) the interface shear sliding dominates the interface shear displacement behavior for both cases of relatively rough and smooth concrete surface except when the clay water content is greater than 16% for the case of rough concrete surface where the shear failure occurs in the body of the clay sample; 2) the results of interface shear strength obtained by direct shear test were different from that of simple shear test for the case of rough concrete surface; 3) two types of interface failure mechanism may change each other with different water content ratio; 4) the interface shear strength increases with increasing water content ratio especially for the case of clay-rough concrete surface interface.

关键词: soil structure interaction     simple shear test     interface     friction     compacted clay     interface modeling    

Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

《结构与土木工程前沿(英文)》 2009年 第3卷 第2期   页码 234-239 doi: 10.1007/s11709-009-0020-7

摘要: This paper aims to study the different vertical displacements in tall hybrid-structures and the corresponding engineering measures. First, the method to calculate the different vertical displacements in tall hybrid-structures is presented. This method takes into account the effects of construction process by applying loads sequentially story by story. Based on the concrete creep and shrinkage calculation formula in American Concrete Institute (ACI) code, with the assumption that loads are increased linearly in members, the creep and shrinkage effects of members are analyzed by adopting two parameters named average load-aged coefficient and average age-last coefficient. The effects of steel ratio on members creep are analyzed by age-adjusted module method (AEMM). The effects that core-tube were constructed in advance to outer steel frame were also considered. Then, based on the sample calculation, the measures to effectively reduce the different vertical displacements in hybrid-structures are proposed. This method is simple and practical in the calculation of different vertical displacements in tall and super-tall hybrid-structures.

关键词: creep     shrinkage     construction process     hybrid-structure    

Development of combined transitional pavement structure for urban tram track-road grade crossings

《结构与土木工程前沿(英文)》   页码 1199-1210 doi: 10.1007/s11709-023-0949-y

摘要: The grade crossings and adjacent pavements of urban trams are generally subjected to complex load conditions and are susceptible to damage. Therefore, in this study, a novel pavement structure between tram tracks and roads constructed using polyurethane (PU) elastic concrete and ultra-high-performance concrete (UHPC), referred to as a track-road transitional pavement (TRTP), is proposed. Subsequently, its performance and feasibility are evaluated using experimental and numerical methods. First, the mechanical properties of the PU elastic concrete are evaluated. The performance of the proposed structure is investigated using a three-dimensional finite element model, where vehicle-induced dynamic and static loads are considered. The results show that PU elastic concrete and the proposed combined TRTP are applicable and functioned as intended. Additionally, the PU elastic concrete achieved sufficient performance. The recommended width of the TRTP is approximately 50 mm. Meanwhile, the application of UHPC under a PU elastic concrete layer significantly reduces vertical deformation. Results of numerical calculations confirmed the high structural performance and feasibility of the proposed TRTP. Finally, material performance standards are recommended to provide guidance for pavement design and the construction of tram-grade crossings in the future.

关键词: urban tram track     grade crossing     combined track-road transitional pavement     polyurethane elastic concrete     finite element method    

Damage assessment and diagnosis of hydraulic concrete structures using optimization-based machine learning

《结构与土木工程前沿(英文)》   页码 1281-1294 doi: 10.1007/s11709-023-0975-9

摘要: Concrete is widely used in various large construction projects owing to its high durability, compressive strength, and plasticity. However, the tensile strength of concrete is low, and concrete cracks easily. Changes in the concrete structure will result in changes in parameters such as the frequency mode and curvature mode, which allows one to effectively locate and evaluate structural damages. In this study, the characteristics of the curvature modes in concrete structures are analyzed and a method to obtain the curvature modes based on the strain and displacement modes is proposed. Subsequently, various indices for the damage diagnosis of concrete structures based on the curvature mode are introduced. A damage assessment method for concrete structures is established using an artificial bee colony backpropagation neural network algorithm. The proposed damage assessment method for dam concrete structures comprises various modal parameters, such as curvature and frequency. The feasibility and accuracy of the model are evaluated based on a case study of a concrete gravity dam. The results show that the damage assessment model can accurately evaluate the damage degree of concrete structures with a maximum error of less than 2%, which is within the required accuracy range of damage identification and assessment for most concrete structures.

关键词: hydraulic structure     curvature mode     damage detection     artifical neural network     artificial bee colony    

标题 作者 时间 类型 操作

Crack detection for wading-concrete structures using water irrigation and electric heating

期刊论文

Performance of steel bridge deck pavement structure with ultra high performance concrete based on resin

期刊论文

Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

期刊论文

水下盾构法铁路隧道管片衬砌结构的原型加载试验研究

何川,封坤,晏启祥,齐春

期刊论文

Seismic performance of prestressed concrete stand structure supporting retractable steel roof

Yiyi CHEN, Dazhao ZHANG, Weichen XUE, Wensheng LU

期刊论文

Nonlinear elastic model for compacted clay concrete interface

R. R. SHAKIR, Jungao ZHU

期刊论文

Automated classification of civil structure defects based on convolutional neural network

Pierclaudio SAVINO, Francesco TONDOLO

期刊论文

Turbidity-adaptive underwater image enhancement method using image fusion

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

中国钢筋混凝土空间网格结构新体系的开拓与发展(下)

马克俭,张华刚,肖建春,卢亚琴

期刊论文

Research on recycled concrete and its utilization in building structures in China

Jianzhuang XIAO, Tao DING

期刊论文

Behavior of compacted clay-concrete interface

R. R .SHAKIR, Jungao ZHU

期刊论文

Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

期刊论文

Development of combined transitional pavement structure for urban tram track-road grade crossings

期刊论文

Damage assessment and diagnosis of hydraulic concrete structures using optimization-based machine learning

期刊论文