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A time−space porosity computational model for concrete under sulfate attack

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0985-7

摘要： The deterioration of the microscopic pore structure of concrete under external sulfate attack (ESA) is a primary cause of degradation. Nevertheless, little effort has been invested in exploring the temporal and spatial development of the porosity of concrete under ESA. This study proposes a mechanical–chemical model to simulate the spatiotemporal distribution of the porosity. A relationship between the corrosion damage and amount of ettringite is proposed based on the theory of volume expansion. In addition, the expansion strain at the macro-scale is obtained using a stress analysis model of composite concentric sphere elements and the micromechanical mean-field approach. Finally, considering the influence of corrosion damage and cement hydration on the diffusion of sulfate ions, the expansion deformation and porosity space−time distribution are obtained using the finite difference method. The results demonstrate that the expansion strains calculated using the suggested model agree well with previously reported experimental results. Moreover, the tricalcium aluminate concentration, initial elastic modulus of cement paste, corrosion damage, and continuous hydration of cement significantly affect concrete under ESA. The proposed model can forecast and assess the porosity of concrete covers and provide a credible approach for determining the residual life of concrete structures under ESA.

关键词： expansion deformation     porosity     internal expansion stress     external sulfate attack     mechanical–chemical coupling model    

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单缝桥梁在温度作用下的结构受力计算

赵怡彬,邵旭东

《中国工程科学》 2012年 第14卷 第10期   页码 103-112

摘要：

桥台处伸缩缝问题是长期困扰工程界的难题，它会带来跳车、桥梁局部损坏、伸缩缝装置经常更换等各种问题。为有效解决这一问题，提出了一种适用于大中型桥梁的新型结构体系——单伸缩缝桥梁（单缝桥）。在考虑接线路面裂缝开展的情况下，建立了温度作用下单缝桥的简化计算模型，推导了单缝桥受力、变形的理论公式，用Fortran90编制程序，进行计算。以一座总长280 m的单缝梁桥为例，温度降低20 ℃时，接线路面钢筋最大应力为148 MPa，最大裂缝宽度为0.185 mm，符合规范要求；台后结构对主梁产生的附加应力仅为0.105 MPa，影响很小。通过对影响单缝桥性能的因素：支座类型、配筋率、接线路面长度、摩擦系数、土体刚度、桥长、温差等进行分析，绘制图表，得到以下主要结论：温降时，接线路面受拉，混凝土开裂，是较不利的状况；30 m长的接线路面可以满足结构受力和变形的需要；选择摩擦系数较小的支座和减少接线路面与垫层的摩擦力可以减少结构内力，在接线路面与垫层间推荐加铺土工格栅。

关键词： 单缝桥梁     温度作用     受力与变形     理论公式     参数分析    

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A MATLAB code for the material-field series-expansion topology optimization method

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 607-622 doi: 10.1007/s11465-021-0637-3

摘要： This paper presents a MATLAB implementation of the material-field series-expansion (MFSE) topo-logy optimization method. The MFSE method uses a bounded material field with specified spatial correlation to represent the structural topology. With the series-expansion method for bounded fields, this material field is described with the characteristic base functions and the corresponding coefficients. Compared with the conventional density-based method, the MFSE method decouples the topological description and the finite element discretization, and greatly reduces the number of design variables after dimensionality reduction. Other features of this method include inherent control on structural topological complexity, crisp structural boundary description, mesh independence, and being free from the checkerboard pattern. With the focus on the implementation of the MFSE method, the present MATLAB code uses the maximum stiffness optimization problems solved with a gradient-based optimizer as examples. The MATLAB code consists of three parts, namely, the main program and two subroutines (one for aggregating the optimization constraints and the other about the method of moving asymptotes optimizer). The implementation of the code and its extensions to topology optimization problems with multiple load cases and passive elements are discussed in detail. The code is intended for researchers who are interested in this method and want to get started with it quickly. It can also be used as a basis for handling complex engineering optimization problems by combining the MFSE topology optimization method with non-gradient optimization algorithms without sensitivity information because only a few design variables are required to describe relatively complex structural topology and smooth structural boundaries using the MFSE method.

关键词： MATLAB implementation     topology optimization     material-field series-expansion method     bounded material field     dimensionality reduction    

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Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 374-380 doi: 10.1007/s11709-011-0122-x

摘要： This paper addresses the problem of condition assessment of bridge expansion joints using long-term measurement data under changing environmental conditions. The effects of temperature, traffic loading and wind on the expansion joint displacements are analyzed and interpreted, which reveal that measured displacements are observed to increase with an increase in temperature and to decrease with increased traffic loading, while the correlation between displacement and wind speed is very weak. Two regression models are developed to simulate the varying displacements under the changes in temperature and traffic loadings. Based on these models, the effects of the environmental conditions are removed to obtain the normalized displacement. Statistical process control using mean value control charts is further used to detect damage to the bridge expansion joints. The results reveal that the proposed method had a good capability for detecting the damage-induced 1.0% variances of the annual changes in the expansion joint displacements.

关键词： structural health monitoring     displacement     expansion joint     temperature effect     wind effect     traffic loading     statistical process control     suspension bridge    

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An approach for evaluating the impact of an intermittent renewable energy source on transmission expansion

Rongrit CHATTHAWORN,Surachai CHAITUSANEY

《信息与电子工程前沿（英文）》 2015年 第16卷 第10期   页码 871-882 doi: 10.1631/FITEE.1500049

摘要： We propose a new robust optimization approach to evaluate the impact of an intermittent renewable energy source on transmission expansion planning (TEP). The objective function of TEP is composed of the investment cost of the transmission line and the operating cost of conventional generators. A method to select suitable scenarios representing the intermittent renewable energy generation and loads is proposed to obtain robust expansion planning for all possible scenarios. A meta-heuristic algorithm called adaptive tabu search (ATS) is employed in the proposed TEP. ATS iterates between the main problem, which minimizes the investment and operating costs, and the subproblem, which minimizes the cost of power generation from conventional generators and curtailments of renewable energy generation and loads. The subproblem is solved by nonlinear programming (NLP) based on an interior point method. Moreover, the impact of an intermittent renewable energy source on TEP was evaluated by comparing expansion planning with and without consideration of a renewable energy source. The IEEE Reliability Test System 79 (RTS 79) was used for testing the proposed method and evaluating the impact of an intermittent renewable energy source on TEP. The results show that the proposed robust optimization approach provides a more robust solution than other methods and that the impact of an intermittent renewable energy source on TEP should be considered.

关键词： Adaptive tabu search     Renewable energy generation     Robust optimization     Transmission expansion planning    

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Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0758-y

摘要： Accurately controlling the nodal lines of vibrating structures with topology optimization is a highly challenging task. The major difficulties in this type of problem include a large number of design variables, the highly nonlinear and multi-peak characteristics of iteration, and the changeable orders of eigenmodes. In this study, an effective material-field series-expansion (MFSE)-based topology optimization design strategy for precisely controlling nodal lines is proposed. Here, two typical optimization targets are established: (1) minimizing the difference between structural nodal lines and their desired positions, and (2) keeping the position of nodal lines within the specified range while optimizing certain dynamic performance. To solve this complex optimization problem, the structural topology of structures is first represented by a few design variables on the basis of the MFSE model. Then, the problems are effectively solved using a sequence Kriging-based optimization algorithm without requiring design sensitivity analysis. The proposed design strategy inherently circumvents various numerical difficulties and can effectively obtain the desired vibration modes and nodal lines. Numerical examples are provided to validate the proposed topology optimization models and the corresponding solution strategy.

关键词： nodal line     topology optimization     structural dynamics design     material-field series-expansion    

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Resistance of large deformation of the Wushaoling Tunnel F7 soft fault

ZHAO Xufeng, CHEN Haiming, WANG Chunmiao

《结构与土木工程前沿（英文）》 2007年 第1卷 第1期   页码 123-127 doi: 10.1007/s11709-007-0013-3

摘要： In this article, the mechanical characteristics of the squeeze of the F7 fault of the Wushaoling Tunnel are analyzed. The measurements and techniques are proposed to resist the deformation. The result indicates that the method of construction to control the further squeeze deflection is appropriate.

关键词： F7     deformation     appropriate     construction     mechanical    

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Numerical modeling of nonlinear deformation of polymer composites based on hyperelastic constitutive

Qingsheng YANG, Fang XU

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 284-288 doi: 10.1007/s11465-009-0067-0

摘要： Fiber reinforced polymer (FRP) composites exhibit nonlinear and hyperelastic characteristics under finite deformation. This paper investigates the macroscopic hyperelastic behavior of fiber reinforced polymer composites using a micromechanical model and finite deformation theory based on the hyperelastic constitutive law. The local stress and deformation of a representative volume element are calculated by the nonlinear finite element method. Then, an averaging procedure is used to find the homogenized stress and strain, and the macroscopic stress-strain curves are obtained. Numerical examples are given to demonstrate hyperelastic behavior and deformation of the composites, and the effects of the distribution pattern of fibers are also investigated to model the mechanical behavior of FRP composites.

关键词： composites     hyperelastic     finite deformation     homogenization     micromechanics    

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Numerical simulation of sudden-expansion two-phase flows with two-scale second-order moment particle

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

《能源前沿（英文）》 2007年 第1卷 第2期   页码 202-206 doi: 10.1007/s11708-007-0026-6

摘要： A two-scale second-order moment particle turbulence model is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The model is employed to simulate gas-particle flows in a sudden-expansion chamber. Simulation results are compared with the experimental results and with those obtained by the single-scale second-order moment two-phase turbulence model. It is shown that the two-scale model is with higher calculating accuracy than the single-scale model.

关键词： gas-particle     single-scale second-order     large-scale fluctuation     second-order     sudden-expansion    

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硝酸铵膨化理论研究

吕春绪

《中国工程科学》 2001年 第3卷 第9期   页码 58-63

摘要：

描述了硝酸铵膨化过程，计算与测定了其物理化学参数，研究了膨化过程的影响因素，并给出了膨化过程可能的机理。

关键词： 膨化硝酸铵     膨化理论     物理化学参数     影响因素    

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A continuous/discontinuous deformation analysis (CDDA) method based on deformable blocks for fracture

Yongchang CAI, Hehua ZHU, Xiaoying ZHUANG

《结构与土木工程前沿（英文）》 2013年 第7卷 第4期   页码 369-378 doi: 10.1007/s11709-013-0222-x

摘要： In the framework of finite element meshes, a novel continuous/discontinuous deformation analysis (CDDA) method is proposed in this paper for modeling of crack problems. In the present CDDA, simple polynomial interpolations are defined at the deformable block elements, and a link element is employed to connect the adjacent block elements. The CDDA is particularly suitable for modeling the fracture propagation because the switch from continuous deformation analysis to discontinuous deformation analysis is natural and convenient without additional procedures. The SIFs (stress intensity factors) for various types of cracks, such as kinked cracks or curved cracks, can be easily computed in the CDDA by using the virtual crack extension technique (VCET). Both the formulation and implementation of the VCET in CDDA are simple and straightforward. Numerical examples indicate that the present CDDA can obtain high accuracy in SIF results with simple polynomial interpolations and insensitive to mesh sizes, and can automatically simulate the crack propagation without degrading accuracy.

关键词： fracture     crack     propagation     deformable block     continuous/discontinuous deformation analysis (CDDA)    

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Calculation methods of the crack width and deformation for concrete beams with high-strength steel bars

Jianmin ZHOU, Shuo CHEN, Yang CHEN

《结构与土木工程前沿（英文）》 2013年 第7卷 第3期   页码 316-324 doi: 10.1007/s11709-013-0211-0

摘要： Three groups of concrete beams reinforced with high-strength steel bars were tested, and the crack width and deformation of the specimens were observed and studied. To facilitate the predictions, two simplified formulations according to a theory developed by the first author were proposed. The advantages of the formulations were verified by the test data and compared with several formulas in different codes.

关键词： concrete beam     high-strength steel bar     crack width     deformation    

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Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

《结构与土木工程前沿（英文）》 2008年 第2卷 第3期   页码 211-218 doi: 10.1007/s11709-008-0025-7

摘要： Magnesia Concrete is a kind of expansive concrete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expansion on the stresses of arch dams, a simple model of autogenous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expansion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogenous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite element arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.

关键词： field-measured     irreversibility     temperature     irreversible     element arch    

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Calculation method of radial stress and deformation on conic threaded connections with interference fit

Shoujun CHEN, Qiang LI, Qi AN,

《机械工程前沿（英文）》 2010年 第5卷 第3期   页码 302-307 doi: 10.1007/s11465-010-0018-9

摘要： This paper presents a calculation method for radial stress distribution and deformation on conic threaded connections with interference fit. Based on elastic mechanics, a new calculation model is established using the thick-walled-cylindrical theory. A sample calculation for API 88.9 mm conic threaded connection indicates that the method proposed in this paper is reasonable, and the finite element analysis (FEA) method is used to validate the proposed method. The results obtained by the proposed method and FEA method are identical. The model offers a new way of calculating the radial stress and deformation on conic thread connections with interference fit.

关键词： conic threaded connections     interference fit     radial stress     deformation     finite element analysis (FEA)    

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燕山石化公司乙烯装置66×104t/a扩能改造方案的研究与决策

曹湘洪

《中国工程科学》 2003年 第5卷 第11期   页码 34-46

摘要：

燕山石化公司30×104t/a乙烯装置1994年完成第一次扩能至45×104t/a的改造后，仍存在原料灵活性差、能耗高、与同期建设的乙烯装置比规模偏小等问题。以全面提高技术水平、降低能耗、增加原料灵活性、尽可能扩大生产能力为目标，充分考虑方案的可实施性、实施时的安全性、实施后的可操作性及方案的先进性和经济性，对装置技术改造的方案进行了比选研究。经改造，实现了生产能力扩大到66×104t/a的目标，实际可达71×104t/a，装置能耗明显下降，石脑油、轻柴油、重柴油、加氢裂化尾油均可作为乙烯原料。在世界上，首次在乙烯装置中采用混合冷剂制冷技术和碳三催化精馏加氢技术并获得成功，对世界乙烯工业技术进步有推动作用。

关键词： 乙烯     装置     扩能     方案     研究    

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标题 作者 时间 类型 操作

A time−space porosity computational model for concrete under sulfate attack

期刊论文

单缝桥梁在温度作用下的结构受力计算

赵怡彬,邵旭东

期刊论文

A MATLAB code for the material-field series-expansion topology optimization method

期刊论文

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental

Youliang DING, Aiqun LI

期刊论文

An approach for evaluating the impact of an intermittent renewable energy source on transmission expansion

Rongrit CHATTHAWORN,Surachai CHAITUSANEY

期刊论文

Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

期刊论文

Resistance of large deformation of the Wushaoling Tunnel F7 soft fault

ZHAO Xufeng, CHEN Haiming, WANG Chunmiao

期刊论文

Numerical modeling of nonlinear deformation of polymer composites based on hyperelastic constitutive

Qingsheng YANG, Fang XU

期刊论文

Numerical simulation of sudden-expansion two-phase flows with two-scale second-order moment particle

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

期刊论文

硝酸铵膨化理论研究

吕春绪

期刊论文

A continuous/discontinuous deformation analysis (CDDA) method based on deformable blocks for fracture

Yongchang CAI, Hehua ZHU, Xiaoying ZHUANG

期刊论文

Calculation methods of the crack width and deformation for concrete beams with high-strength steel bars

Jianmin ZHOU, Shuo CHEN, Yang CHEN

期刊论文

Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

期刊论文

Calculation method of radial stress and deformation on conic threaded connections with interference fit

Shoujun CHEN, Qiang LI, Qi AN,

期刊论文

燕山石化公司乙烯装置66×104t/a扩能改造方案的研究与决策

曹湘洪

期刊论文