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3D fracture modelling and limit state analysis of prestressed composite concrete pipes

Pengfei HE, Yang SHEN, Yun GU, Pangyong SHEN

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 165-175 doi: 10.1007/s11709-018-0484-4

摘要： In this manuscript, we study fracture of prestressed cylindrical concrete pipes. Such concrete pipes play a major role in tunneling and underground engineering. The structure is modelled fully in 3D using three-dimensional continuum elements for the concrete structure which beam elements are employed to model the reinforcement. This allows the method to capture important phenomena compared to a pure shell model of concrete. A continuous approach to fracture is chosen when concrete is subjected to compressive loading while a combined continuous-discrete fracture method is employed in tension. The model is validated through comparisons with experimental data.

关键词： cylindrical concrete structures     limit state analysis     3D fracture modelling     prestressed composite pipes     reinforced concrete     three-point bending test    

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砼非标准三点弯曲梁试件双K断裂参数

吴智敏,徐世烺,丁一宁,卢喜经,刘佳毅,丁生根

《中国工程科学》 2001年 第3卷 第4期   页码 76-81

摘要：

采用跨高比为2.5的非标准三点弯曲梁试件，利用在试验中测得的最大荷载Pmax及对应的裂缝口张开位移CMODc，根据渐近线性叠加假设，求得了砼裂缝亚临界扩展量∆ac。在此基础上，采用虚拟裂缝模型计算了不同初始缝长、不同试件髙度的砼非标准三点弯曲梁试件的起裂断裂韧度KiniIC、失稳断裂韧度KunIC及临界裂 缝尖端张开位移CTODc。计算结果表明，砼KunIC：与试件高度及初始缝高比无关；而KiniIC在初始缝髙比a0/h = 0.3〜0.5内，也是一稳定的常数且与试件高度无关。这说明砼双K断裂参数可以作为砼的材料常数。

关键词： 砼     三点弯曲梁     断裂参数    

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黏聚裂纹阻抗的弯曲梁承载力

王利民,徐世,任传波

《中国工程科学》 2007年 第9卷 第2期   页码 30-35

摘要：

在混凝土类软化材料断裂研究中，裂纹端部损伤区被简化为具有黏聚应力分布的非线性裂纹，该黏 聚力对裂纹扩展有阻抗作用。裂纹体的应力强度因子是断裂力学标志载荷作用与几何构型因素的量化表达指标； 黏聚力形成的阻抗强度因子数值，与黏聚裂纹长度和材料极值拉伸应力存在数量关系。通过双K断裂判据，以 带切口的三点弯曲梁为断裂力学模型，分析了裂纹黏聚阻力对断裂过程的影响规律，计算该弯曲梁结构断裂试 样的最大承担载荷；其结果比较符合实验数据。

关键词： 黏聚裂纹     三点弯曲梁     混凝土     双K断裂参数     结构承载力    

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Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0968-8

摘要： Fiber-reinforced polymers (FRPs) have received considerable research attention because of their high strength, corrosion resistance, and low weight. However, owing to the lack of ductility in this material and the quasi-brittle behavior of concrete, FRP-reinforced concrete (FRP-RC) beams, even with flexural failure, do not fail in a ductile manner. Because the limited deformation capacity of FRP-RC beams depends on the ductility of their compression zones, the present study proposes using a precast confined concrete block (PCCB) in the compression zone to improve the ductility of the beams. A control beam and four beams with different PCCBs were cast and tested under four-point bending conditions. The control beam failed due to shear, and the PCCBs exhibited different confinements and perforations. The goal was to find an appropriate PCCB for use in the compression zone of the beams, which not only improved the ductility but also changed the failure mode of the beams from shear to flexural. Among the employed blocks, a ductile PCCB with low equivalent compressive strength increased the ductility ratio of the beam to twice that of the control beam. The beam failed in pure flexure with considerable deformation capacity and without significant stiffness reduction.

关键词： ductility     four-point bending test     glass fiber-reinforced polymer     precast confined concrete block    

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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）》   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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Effect of asphalt thin beams mixed with three nominal maximum aggregate sizes in the bending beam rheometer

Chun-Hsing HO,María Francisca Martínez GONZÁLEZ,Cristina Pilar Martín LINARES

《结构与土木工程前沿（英文）》 2017年 第11卷 第1期   页码 1-7 doi: 10.1007/s11709-016-0367-5

摘要： The objective of this research is to evaluate an impact of asphalt mixture beams with varying sizes of aggregate in the Bending Beam Rheometer (BBR) for testing/predicting thermal cracking properties of asphalt pavements. The BBR test has following benefits: the equipment is cheaper, it uses smaller specimens, faster conditioning, easier availability for quality control, easier to manage, etc. However some concerns have been raised: some consider that the size of the aggregate may affect the test’s results; the other concern is that such small beams cannot represent the whole properties of the asphalt pavement. To address these criticisms, imaging techniques, statistical analysis, and viscoelastic modeling are used. Asphalt thin beams prepared with three different nominal maximum aggregate size (NMAS) (12.5mm, 9.5 mm, and 4.75 mm) were tested at three different temperatures (-18°C, -24°C, and -30°C). Based on results from statistical analyses and viscoelasticity, the ratio of asphalt binders and voids and stiffness differences among the three NMAS specimens are not significant, meaning that the impact of asphalt thin beams prepared with the three NMAS on the prediction of thermal cracking is minimal and can be neglected.

关键词： bending beam rheometer     thin beams     thermal cracking    

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Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement system

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 378-389 doi: 10.1007/s11709-021-0706-z

摘要： In this study, we conducted experimental tests on two specimens of reinforced concrete beams using a three-point bending test to optimize the flexure and stiffness designs. The first specimen is a reinforced concrete beam with an ordinary reinforcement, and the second specimen has an invented reinforcement system that consists of an ordinary reinforcement in addition to three additional bracings using steel bars and steel plates. The results of the flexure test were collected and analyzed, and the flexural strength, the rate of damage during bending, and the stiffness were determined. Finite element modeling was applied for both specimens using the LS-DYNA program, and the simulation results of the flexure test for the same outputs were determined. The results of the experimental tests showed that the flexural strength of the invented reinforcement system was significantly enhanced by 15.5% compared to the ordinary system. Moreover, the flexural cracks decreased to a significant extent, manifesting extremely small and narrow cracks in the flexure spread along the bottom face of the concrete. In addition, the maximum deflection for the invented reinforced concrete beam decreased to 1/3 compared to that of an ordinary reinforced concrete beam. The results were verified through numerical simulations, which demonstrated excellent similarities between the flexural failure and the stiffness of the beam. The invented reinforcement system exhibited a high capability in boosting the flexure design and stiffness.

关键词： three-point flexure test     softening stage     flexural crack     flexural strain    

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Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 411-428 doi: 10.1007/s11709-023-0928-3

摘要： In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.

关键词： pre-stressed concrete sleeper     ultrahigh performance fiber-reinforced concrete     pull-out test     static bending test     steel fiber     aspect ratio     volume fraction    

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Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 350-367 doi: 10.1007/s11709-022-0923-0

摘要： A new rocking constraint device (RCD) is developed for three-dimensional (3D) base-isolated frame structures by connecting a custom-designed cylinder pair to provide vertical damping with replaceable damping components installed outside the cylinders when the superstructure undergoes translational motion, and rocking constraint capacity when the superstructure is susceptible to rocking. Theoretical formulas for calculating the damping and rocking constraint stiffness of the RCD are proposed. Two series of sinusoidal loading tests are conducted at different loading frequencies and amplitudes to verify the damping and rocking constraint performance of the RCD. The test results show that the cylinder without orifices on its piston can provide the desired damping with a replaceable damping component, and that the RCD can effectively suppress rocking. Although the vertical stiffness of an individual cylinder is affected by the location of the replaceable damping component and loading frequency, the average vertical stiffness of the two cylinders, which determines the rocking constraint stiffness of the RCD, is independent of the two factors. Comparisons of the test and theoretical results indicate that the errors of the proposed formulas for calculating the damping and rocking constraint stiffness of the RCD do not exceed 12.9% and 11.0%, respectively.

关键词： three-dimensional isolation     rocking behavior     rocking constraint device     replaceable damping component     sinusoidal test    

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基于双目立体匹配和B样条的三维人脸点云孔洞修补算法 Research Articles

黄源1,2,达飞鹏1,2

《信息与电子工程前沿（英文）》 2022年 第23卷 第3期   页码 398-408 doi: 10.1631/FITEE.2000508

摘要： 在基于结构光的三维人脸点云数据采集过程中，由于环境、遮挡以及光照强度等因素影响，采集到的数据往往会出现孔洞区域，从而影响后续识别效果。本文提出一种采用立体匹配技术结合B样条的孔洞修补方法。算法首先利用光栅投影过程中获取的相位信息定位点云中的孔洞区域，同时提取边界点集。然后将立体匹配算法获取的人脸点云数据同光栅投影法采集的数据进行配准，在孔洞处选取初始修补控制点。再利用B样条曲线形状可由少数关键点大致描述这一特性，将控制点作为关键点放入孔洞区域进行曲面重建迭代计算。仿真使用光滑陶瓷杯和人脸模型进行，结果表明，该算法能够准确再现被测物体表面的细节和复杂形状。同时也说明所提方法具有强鲁棒性，能够在完全无先验信息的情况下对物体复杂区域实现孔洞修补，并且修补后的点云更加接近原始数据。该方法可广泛应用于需要精确人脸识别的领域。

关键词： 三维点云；孔洞修补；立体匹配；B样条    

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A new meshless approach for bending analysis of thin plates with arbitrary shapes and boundary conditions

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 75-85 doi: 10.1007/s11709-021-0798-5

摘要： An efficient and meshfree approach is proposed for the bending analysis of thin plates. The approach is based on the choice of a set of interior points, for each of which a basis function can be defined. Plate deflection is then approximated as the linear combination of those basis functions. Unlike traditional meshless methods, present basis functions are defined in the whole domain and satisfy the governing differential equation for plate. Therefore, no domain integration is needed, while the unknown coefficients of deflection expression could be determined through boundary conditions by using a collocation point method. Both efficiency and accuracy of the approach are shown through numerical results of plates with arbitrary shapes and boundary conditions under various loads.

关键词： plate     bending     meshless method     collocation    

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深层搅拌桩墙围护结构裂缝成因探讨

高文华,王祥秋,陈秋南,张志敏

《中国工程科学》 2005年 第7卷 第12期   页码 88-91

摘要：

针对基坑支护中深层搅拌桩墙围护结构出现的开裂，采用Mindlin厚板理论对其受力与变形性状进行弹塑性分析，建立了墙体的厚板力学模型和三维有限元分析模型，并编制了有限元分析程序；基于墙体受到纵向弯矩、横向弯矩和扭矩的综合作用，提出采用等效弯矩法评价墙体的综合抗弯性能；利用所编制的程序，获得了某基坑深层搅拌桩墙围护结构墙体水平位移和等效弯矩的空间分布规律；计算结果表明，墙体东侧环球广场横向支撑附加力的作用是使墙体形成破裂面的主要原因。

关键词： 裂缝     深层搅拌桩墙     厚板     等效弯矩     三维有限元    

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Improved prediction of pile bending moment and deflection due to adjacent braced excavation

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0961-2

摘要： Deep excavations in dense urban areas have caused damage to nearby existing structures in numerous past construction cases. Proper assessment is crucial in the initial design stages. This study develops equations to predict the existing pile bending moment and deflection produced by adjacent braced excavations. Influential parameters (i.e., the excavation geometry, diaphragm wall thickness, pile geometry, strength and small-strain stiffness of the soil, and soft clay thickness) were considered and employed in the developed equations. It is practically unfeasible to obtain measurement data; hence, artificial data for the bending moment and deflection of existing piles were produced from well-calibrated numerical analyses of hypothetical cases, using the three-dimensional finite element method. The developed equations were established through a multiple linear regression analysis of the artificial data, using the transformation technique. In addition, the three-dimensional nature of the excavation work was characterized by considering the excavation corner effect, using the plane strain ratio parameter. The estimation results of the developed equations can provide satisfactory pile bending moment and deflection data and are more accurate than those found in previous studies.

关键词： pile responses     excavation     prediction     deflection     bending moments    

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Measurement of dynamic fracture toughness and failure behavior for explosive mock materials

Pengwan CHEN, Zhongbin ZHOU, Shaopeng MA, Qinwei MA, Fenglei HUANG

《机械工程前沿（英文）》 2011年 第6卷 第3期   页码 292-295 doi: 10.1007/s11465-011-0237-8

摘要：

In this work, a pre-cracked semi-circular shaped explosive simulant was loaded using a split Hopkinson pressure bar (SHPB). A high-speed camera was used to capture the deformation and fracture process of the specimen in situ. The digital images were processed using the digital image correlation (DIC) method. Next, full displacement and strain fields were obtained. The displacement vector field shows that the specimen fractured under tensile stress action. The strain field can be used to predict the crack propagation. Results show that the method of combined DIC and SHPB is effective to study the dynamic deformation and fracture behavior of explosive simulants. In addition, the specimen was loaded using a drop weight. The fracture toughness of the specimen was preliminary measured.

关键词： digital image correlation     polymer bonded explosive simulant     split Hopkinson pressure bar (SHPB)     semicircular bending test     deformation     fracture toughness    

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Centrifuge model test on dynamic behavior of group-pile foundation with inclined piles and its numerical

ZHANG Feng, OKAWA Katsunori, KIMURA Makoto

《结构与土木工程前沿（英文）》 2008年 第2卷 第3期   页码 233-241 doi: 10.1007/s11709-008-0033-7

摘要： In this paper, dynamic behavior of a group-pile foundation with inclined piles in loose sand has been investigated with centrifuge model tests. The test results are also simulated with elastoplastic dynamic finite element method, in which, not only sectional force of piles, stress of ground, but also deformation of piles are calculated using a three-dimensional elastoplastic dynamic finite element analysis (Code name: DGPILE-3D). The numerical analyses are conducted with a full system in which a superstructure, a pile foundation and surrounding ground are considered together so that interaction between pile foundation and soils can be properly simulated because the nonlinearities of both the pile and the ground are described with suitable constitutive models. Different types of piles, vertical pile or inclined pile, are considered in order to verify the different characteristics of a group pile foundation with inclined piles. The validity of the calculation is verified by the model tests.

关键词： centrifuge     Different     three-dimensional elastoplastic     calculation     inclined    

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标题 作者 时间 类型 操作

3D fracture modelling and limit state analysis of prestressed composite concrete pipes

Pengfei HE, Yang SHEN, Yun GU, Pangyong SHEN

期刊论文

砼非标准三点弯曲梁试件双K断裂参数

吴智敏,徐世烺,丁一宁,卢喜经,刘佳毅,丁生根

期刊论文

黏聚裂纹阻抗的弯曲梁承载力

王利民,徐世,任传波

期刊论文

Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

期刊论文

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

期刊论文

Effect of asphalt thin beams mixed with three nominal maximum aggregate sizes in the bending beam rheometer

Chun-Hsing HO,María Francisca Martínez GONZÁLEZ,Cristina Pilar Martín LINARES

期刊论文

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement system

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

期刊论文

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

期刊论文

Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated

期刊论文

基于双目立体匹配和B样条的三维人脸点云孔洞修补算法

黄源1,2,达飞鹏1,2

期刊论文

A new meshless approach for bending analysis of thin plates with arbitrary shapes and boundary conditions

期刊论文

深层搅拌桩墙围护结构裂缝成因探讨

高文华,王祥秋,陈秋南,张志敏

期刊论文

Improved prediction of pile bending moment and deflection due to adjacent braced excavation

期刊论文

Measurement of dynamic fracture toughness and failure behavior for explosive mock materials

Pengwan CHEN, Zhongbin ZHOU, Shaopeng MA, Qinwei MA, Fenglei HUANG

期刊论文

Centrifuge model test on dynamic behavior of group-pile foundation with inclined piles and its numerical

ZHANG Feng, OKAWA Katsunori, KIMURA Makoto

期刊论文