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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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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P_max及对应的裂缝口张开位移CMOD_c，根据渐近线性叠加假设，求得了砼裂缝亚临界扩展量∆a_c。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Kⁱⁿⁱ_IC、失稳断裂韧度K^un_IC及临界裂缝尖端张开位移CTOD_c。计算结果表明，砼K^un_IC：与试件高度及初始缝高比无关；而Kⁱⁿⁱ_IC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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Robust control of

Xueyan TANG, I-Ming CHEN

《机械工程前沿（英文）》 2009年第4卷第1期页码 25-34 doi: 10.1007/s11465-009-0004-2

摘要： This article describes the development of an flexure-based micromanipulator, with the features of decoupled kinematic structure, large motion range, high positioning precision, and fast response. The large motion range of flexure mechanisms is quantified by a given definition. Based on the given definition, large motion is achieved in the mechanical design of the -flexure parallel mechanism (FPM). To ensure high positioning precision and fast dynamic response, a hybrid control algorithm with both position control and vibration control are designed, using the H -theory. The controller strongly solves the three common problems of flexure mechanisms simultaneously, including unmodeled uncertainties, the external disturbances and vibration caused by inherent low damping.

关键词： robust control flexure mechanisms flexure-based micromanipulator

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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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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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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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Unified power quality conditioner based on a three-level NPC inverter using fuzzy control techniques

Salim CHENNAI,M-T BENCHOUIA

《能源前沿（英文）》 2014年第8卷第2期页码 221-239 doi: 10.1007/s11708-014-0317-7

摘要： This paper presents a novel and efficient control scheme for unified power quality conditioner (UPQC) based on three-level neutral point clamped (NPC) inverter using fuzzy logic techniques. The proposed UPQC is capable of mitigating source current harmonics and compensate all voltage disturbances such as voltage sags, swells, unbalances and harmonics. It is designed by the integration of series and shunt active filters (AFs) sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt active power filters (APFs) and the power reactive theory (p-q theory) for series APFs. The shunt and series APF reference signals derived from the control algorithm and sensed signals are injected in two controllers to generate switching signals. To improve the UPQC capability, fuzzy logic techniques are introduced to control the series APF. The performances of the proposed UPQC system are evaluated in terms of power factor correction, mitigation of voltage or current harmonics and all other voltage disturbances compensation using Matlab-Simulink software and SimPowerSystem toolbox. The simulation results illustrate the performance of the proposed UPQC at the common connection point of the nonlinear load to improve the power energy quality.

关键词： three-level neutral point clamped (NPC) inverter unified power quality conditioner (UPQC) current harmonics mitigation fuzzy logic controller voltage disturbance compensation shunt active filter series active filter power quality energy improvement

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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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面向精密增材制造的大范围柔性伺服系统

Zhen Zhang, Peng Yan, Guangbo Hao

《工程（英文）》 2017年第3卷第5期页码 708-715 doi: 10.1016/J.ENG.2017.05.020

摘要：

本文主要介绍可用于微立体光固化（MSL）工艺的基于分布柔度簧片的大范围柔性纳米伺服系统的设计、开发和控制。作为这一高精度工艺的使能技术，本文设计了一种兼具毫米级运动行程和纳米级运动精度的紧凑型台式柔性纳米运动系统。由于在运行中无需装配和维护，这种柔性运动系统非常适合苛刻的操作条件。从机械设计的角度来看，镜像对称布局和适当的冗余约束对于抑制寄生运动至关重要。本文对此系统进行了详细的有限元分析（FEA），分析结果表面系统具有满意的机械特征。通过纳米运动系统的动力学模型辨识，本文设计了实时控制策略，并将其应用在一体加工的原型系统中。实验验证了面向MSL 工艺过程的轨迹跟踪性能。所提出的纳米伺服运动系统具有毫米级的工作范围，圆轨迹跟踪误差约为80 nm（均方根值）。

关键词：精密增材制造微立体光固化纳米定位分布柔度簧片

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三峡升船机横梁贝雷架支撑系统荷载试验

汪文亮,肖传勇,张俊霞

《中国工程科学》 2013年第15卷第9期页码 50-54

摘要：

在三峡升船机续建工程中，针对塔柱横梁施工支撑体系复杂的特点，在横梁混凝土浇筑前进行荷载试验。试验选取轴1、轴2横梁及其相应的基础梁贝雷架作为模型，按照1∶1进行荷载原型试验，通过布置监测点以及采用合理的检测频率，完成试验数据的采集与分析。本次试验取得以下成果：得出了各类型杆件在加载过程中的最大应力值；随着加载量的增加，横梁、基础梁贝雷架的挠度变化量慢慢增大，模板及排架立杆高程在下降；随着加载量的增加，横梁、基础梁贝雷架都发生了较小的侧向位移，轴2横梁模板左右方向变化量和排架立杆垂直度左右方向变化量均很小；试验监测数据表明，经加强后的贝雷架杆件加载后的各项参数满足安全要求，技术方案可应用于塔柱横梁施工，保证升船机塔柱横梁施工安全。

关键词：横梁贝雷架试验三峡升船机

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三峡升船机齿条及螺母柱间隙灌浆工艺试验

詹剑霞,李纪虎

《中国工程科学》 2013年第15卷第9期页码 45-49

摘要：

为了选择出合适的灌浆材料和灌浆工艺并模拟升船机齿条、螺母柱间隙灌浆的实际情况，分别进行了灌浆工艺试验与原型灌浆试验。灌浆工艺试验对比了3种国产灌浆材料和德国PAGEL灌浆材料，试验结果表明德国PAGEL灌浆材料物理性能指标和力学性能指标优于国产灌浆材料。在原型灌浆试验中，对灌浆设备选型、搅拌时间、模板密封、灌浆方式、灌浆流速参数控制等方面进行了试验研究，优选出适用于三峡升船机齿条、螺母柱接缝灌浆的材料和合适的灌浆工艺。以上试验效果明显，解决了灌浆密封难度大、易堵管等施工难题。

关键词：齿条螺母柱灌浆升船机三峡工程

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Comparative genotoxicity of water processed by three drinking water treatment plants with different water

Ting Zhang, Heze Liu, Yiyuan Zhang, Wenjun Sun, Xiuwei Ao

《环境科学与工程前沿（英文）》 2020年第14卷第3期 doi: 10.1007/s11783-020-1214-4

摘要： Genotoxicity of substances is unknown in the water after treatment processes. Genotoxicity decreased by activated carbon treatment but increased by chlorination. Halogenated hydrocarbons and aromatic compounds contribute to genotoxicity. Genotoxicity was assessed by umu test; acute and chronic toxicity by ECOSAR. Inconsistent results confirmed that genotoxicity cannot be assessed by ECOSAR. Advanced water treatment is commonly used to remove micropollutants such as pesticides, endocrine disrupting chemicals, and disinfection byproducts in modern drinking water treatment plants. However, little attention has been paid to the changes in the genotoxicity of substances remaining in the water following the different water treatment processes. In this study, samples were collected from three drinking water treatment plants with different treatment processes. The treated water from each process was analyzed and compared for genotoxicity and the formation of organic compounds. The genotoxicity was evaluated by an umu test, and the acute and chronic toxicity was analyzed through Ecological Structure- Activity Relationship (ECOSAR). The results of the umu test indicated that biological activated carbon reduced the genotoxicity by 38%, 77%, and 46% in the three drinking water treatment plants, respectively, while chlorination increased the genotoxicity. Gas chromatograph-mass spectrometry analysis revealed that halogenated hydrocarbons and aromatic compounds were major contributors to genotoxicity. The results of ECOSAR were not consistent with those of the umu test. Therefore, we conclude that genotoxicity cannot be determined using ECOSAR .

关键词： Drinking water Treatment process Genotoxicity Umu test Ecological Structure-Activity Relationship

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三峡升船机塔柱混凝土施工测量技术

罗琛,晏春波

《中国工程科学》 2013年第15卷第9期页码 97-101

摘要：

针对三峡垂直升船机高薄壁塔柱结构混凝土形体及内置埋件施工精度指标要求，对三峡升船机塔柱混凝土及内置埋件施工测量中的平面、高程基准传递及埋件定位测量方法进行了研究。分别将天顶仪投点、电磁波测距及中心带照准标志的圆柱螺帽型定位装置施工测量技术运用于混凝土结构尺寸控制测量以及内置埋件定位测量。通过对实测数据的统计与分析，证明三峡升船机塔柱混凝土施工测量技术方案具有可靠性和可行性。

关键词：施工测量天顶仪投点电磁波测距套管空间定位测量三峡升船机