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Investigation of mechanical performance of prestressed steel arch in tunnel

Yaqiong WANG, Yunxiao XIN, Yongli XIE, Jie LI, Zhifeng WANG

《结构与土木工程前沿（英文）》 2017年第11卷第3期页码 360-367 doi: 10.1007/s11709-017-0429-3

摘要： In the traditional tunneling method, the steel arch are often adopted to support surrounding rock to ensure the structural stability. If the steel arch is prestressed in time, tunnel support can effectively prevent the development of rock crack, thereby increasing the overall strength of tunnel support and suppress the deformation of the surrounding rock. Based on the mechanical model of steel arch established in this paper, the stress distribution of steel arch is investigated via the numerical simulation method, and the impact on surrounding rock is also analyzed. Through a field test, the rules of the arch strain distribution are observed and discussed. The results show that the prestressed steel arch structure can provide effective support and the stress gradually decreases from stress point to another arch springing. Furthermore, the stress distribution applied by the prestressed steel arch on the surrounding rock is uniform in a certain extent, and it is suggested that this construction method utilizing the prestressed steel arch to squeeze surrounding rock is feasible from a theoretical view.

关键词： tunnel support prestressing force steel arch numerical analysis

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体外预应力凸块锚固区配筋设计研究

洪浩,童育强,贺志启,刘钊

《中国工程科学》 2013年第15卷第8期页码 95-98

摘要：

混凝土凸块锚固区是体外预应力的一种常见锚固形式，目前尚没有成熟的设计方法。本文通过有限元数值分析，揭示了产生局部拉应力集中的3种作用效应；在此基础上，提出了这3种局部作用效应合拉力的解析计算公式，作为凸块锚固区定量化配筋设计的依据。通过南京长江第四大桥引桥凸块锚固区的设计实践，表明该方法具有良好的实用性。

关键词：凸块锚固区体外预应力配筋设计锚下劈裂悬臂效应锚后牵拉

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Experimental research on the mechanical property of prestressing steel wire during and after heating

ZHENG Wenzhong, HU Qiong, ZHANG Haoyu

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 247-254 doi: 10.1007/s11709-007-0031-1

摘要： The mechanical property of prestressing steel wire during and after heating is the key factor in the design of fire resistance and after-fire damage evaluation of prestressed structures. Tensile experiment of 16 prestressing steel wires ( = 1770 N/mm, = 5 mm, low relaxation of stress) at high temperature and tensile experiment of 14 prestressed steel wires after heating are carried out. According to the experiment, the shapes of stress-strain curves of steel wire at high temperature go smooth and the mechanical property indexes of the steel wire such as strength, modulus of elasticity, etc., degenerate continuously as temperature increased. According to the experiment after heating, the mechanical property of steel wire varies little when the highest temperature that the steel wire has ever been heated to is lower than 300vH; while the stress-strain curves of steel wire become more ductile and the mechanical property indexes of the steel wire degenerate gradually when the highest temperature is higher than 300vH. By applying the theory of viscoelastic mechanics, stress-strain curves of steel wire at high temperatures without loading rate influence are obtained. The law of mechanical property indexes of the wire is presented. The mathematical models of the stress-strain relationship of the pre-stressed steel wire are established. All can serve as basic data for the analysis of fire resistance and after-fire damage evaluation of pre-stressed structures.

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Modeling limit force capacities of high force to volume lead extrusion dampers

《结构与土木工程前沿（英文）》 2021年第15卷第3期页码 609-622 doi: 10.1007/s11709-021-0724-x

摘要： Lead extrusion dampers are supplemental energy-dissipation devices that are used to mitigate seismic structural damage. Small volumetric sizes and high force capacities define high-force-to-volume (HF2V) devices, which can absorb significant response energy without sacrificial damage. However, the design of such devices for specific force capacities has proven difficult based on the complexities of their internal reaction mechanisms, leading to the adoption of empirical approaches. This study developed upper- and lower-bound force capacity estimates from analytical mechanics based on direct and indirect metal extrusion for guiding design. The derived equations are strictly functions of HF2V device geometric parameters, lead material properties, and extrusion mechanics. The upper-bound estimates from direct and indirect extrusion are denoted as (F_UB,1, F_UB,2) and (F_UB,3, F_UB,4), respectively, and the lower-bound estimates are denoted as (F_LB, F_LB,1) based on the combination of extrusion and friction forces. The proposed models were validated by comparing the predicted bounds to experimental force capacity data from 15 experimental HF2V device tests. The experimental device forces all lie above the lower-bound estimates (F_LB, F_LB,1) and below the upper-bound estimates (F_UB,1, F_UB,2, F_UB,4). Overall, the (F_LB, F_UB,2) pair provides wider bounds and the (F_LB,1, F_UB,4/F_UB,1) pair provides narrower bounds. The (F_LB,1, F_UB,1) pair has a mean lower-bound gap of 36%, meaning the lower bound was 74% of the actual device force on average. The mean upper-bound gap was 33%. The bulge area and cylinder diameter of HF2V devices are key parameters affecting device forces. These relatively tight bounds provide useful mechanics-based predictive design guides for ensuring that device forces are within the targeted design range after manufacturing.

关键词： extrusion lead dampers upper and lower bound analytical modelling limit force

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monitoring of the strengthening construction of a segmental box girder bridge and field testing of external prestressing

Ali Fadhil NASER, Zonglin WANG

《结构与土木工程前沿（英文）》 2012年第6卷第3期页码 308-320 doi: 10.1007/s11709-012-0140-3

摘要： Prestressed concrete segmental box girder bridges are composed of short concrete segments that are either precast or cast in situ and then joined together by longitudinally post-tensioning internal, external, or mixed tendons. The objectives of this study are to monitor the construction process of the external prestressing tendons to strengthen the bridge structure and perform a field load test to measure the strain and the deflection of the anchorage devices of the external prestressing tendons to determine the state of these devices after tension forces are applied. The monitoring process of the external prestressing tendons construction includes inspecting the cracks in the diaphragm anchorage and the deviation block devices before the tension forces are applied to the external tendons; measuring the deformation of the steel deviation cross beam during the tension process; measuring the deformation of the box girder after different levels of tension forces are applied; measuring the elongation of the external tendons in each level of the tension; and measuring the natural frequency of the external tendons after the tension process is complete. The results of the monitoring process show that the measured values of the deformation, the elongation, and the natural frequency meet the requirements. Therefore, there is no damage during the construction and the tensioning of the external prestressing tendons. A field load test is performed to the anchorage beam, the steel deviation block devices, and the steel deviation cross beam. The field load test results of the anchorage devices show that the values of the strains, the stresses, and the deflection are less than the respective allowable limit values in the requirements. Therefore, the anchorage devices have sufficient strength, and the working state is good after the tension forces are applied to the external prestressing tendons.

关键词： prestressed concrete box girder monitoring external tendons strain deflection

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武广客运专线32 m箱梁预应力效果监测及徐变上拱的控制措施

宋津喜

《中国工程科学》 2009年第11卷第1期页码 60-66

摘要：

采用现场实测的方法对武广客运专线工程32 m预应力混凝土箱梁应力效果进行监测，并采用Midas/Civil结构分析程序进行了弹性上拱的理论分析，提出箱梁徐变上拱的控制措施，为同类工程提供借鉴及经验。

关键词：武广客运专线 32 m箱梁预应力效果监测徐变上拱控制

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Quality control based on electrode displacement and force in resistance spot welding

Chuntao JI, Lipeng DENG

《机械工程前沿（英文）》 2010年第5卷第4期页码 412-417 doi: 10.1007/s11465-010-0114-x

摘要： The behaviors of electrode displacement and force during spot welding under various conditions, such as different weld currents, electrode forces, and welding times, were studied. Tests were conducted on a 170?kVA MFDC spot welder. Data were collected via a multichannel high-speed data acquisition system and were analyzed with MATLAB. Behaviors of 5182 aluminum and mild steel in spot welding were compared. Results show that nugget expansion rate does not reach zero for aluminium as it does for mild steel as nugget grew to a certain size. A linear relationship is found between the nugget size and maximum expansion that facilitates online weld quality evaluation. An electrode force peak is observed and believed relevant to the sufficient nugget size.

关键词： aluminum electrode displacement electrode force nugget size data acquisition

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Visualization of force networks in 2D dense granular materials

Jianguo LIU, Qicheng SUN, Feng JIN,

《结构与土木工程前沿（英文）》 2010年第4卷第1期页码 109-115 doi: 10.1007/s11709-010-0003-8

摘要： Dense granular matter is a conglomeration of discrete solid and closely packed particles. As subjected to external loadings, the stress is largely transmitted by heavily stressed chains of particles forming a sparse network of larger contact forces. To understand the structure and evolution of force chains, a photoelastic technique was improved for determining stresses and strains in the assemblies of photoelastic granular disks in this paper. A two-dimensional vertical slab was designed. It contains 7200 polydispersed photoelastic disks and is subjected to a localized probe penetrating at the top of the slab to mimic the cone penetration test. The interparticle contact force distribution was found a peak around the mean value, a roughly exponential tail for greater force and a dip toward zero for smaller force. The force chain network around the probe tip was depicted, and the contact angle distribution of particles in force chains was found to be well aligned in the directions of major principal stress.

关键词： granular matter force chain multiscale modeling

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Motion/force transmission indices of parallel manipulators

Xinjun LIU, Chao WU, Fugui XIE

《机械工程前沿（英文）》 2011年第6卷第1期页码 89-91 doi: 10.1007/s11465-011-0215-1

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Applications of atomic force microscopy in immunology

Jiping Li, Yuying Liu, Yidong Yuan, Bo Huang

《医学前沿（英文）》 2021年第15卷第1期页码 43-52 doi: 10.1007/s11684-020-0769-6

摘要： Cellular mechanics, a major regulating factor of cellular architecture and biological functions, responds to intrinsic stresses and extrinsic forces exerted by other cells and the extracellular matrix in the microenvironment. Cellular mechanics also acts as a fundamental mediator in complicated immune responses, such as cell migration, immune cell activation, and pathogen clearance. The principle of atomic force microscopy (AFM) and its three running modes are introduced for the mechanical characterization of living cells. The peak force tapping mode provides the most delicate and desirable virtues to collect high-resolution images of morphology and force curves. For a concrete description of AFM capabilities, three AFM applications are discussed. These applications include the dynamic progress of a neutrophil-extracellular-trap release by neutrophils, the immunological functions of macrophages, and the membrane pore formation mediated by perforin, streptolysin O, gasdermin D, or membrane attack complex.

关键词： cellular mechanics atomic force microscopy neutrophil extracellular trap macrophage phagocytosis pore formation

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Non-convex sparse optimization-based impact force identification with limited vibration measurements

《机械工程前沿（英文）》 2023年第18卷第3期 doi: 10.1007/s11465-023-0762-2

摘要： Impact force identification is important for structure health monitoring especially in applications involving composite structures. Different from the traditional direct measurement method, the impact force identification technique is more cost effective and feasible because it only requires a few sensors to capture the system response and infer the information about the applied forces. This technique enables the acquisition of impact locations and time histories of forces, aiding in the rapid assessment of potentially damaged areas and the extent of the damage. As a typical inverse problem, impact force reconstruction and localization is a challenging task, which has led to the development of numerous methods aimed at obtaining stable solutions. The classical

ℓ 2

regularization method often struggles to generate sparse solutions. When solving the under-determined problem,

ℓ 2

regularization often identifies false forces in non-loaded regions, interfering with the accurate identification of the true impact locations. The popular

ℓ 1

sparse regularization, while promoting sparsity, underestimates the amplitude of impact forces, resulting in biased estimations. To alleviate such limitations, a novel non-convex sparse regularization method that uses the non-convex

ℓ 1 − 2

penalty, which is the difference of the

ℓ 1

and

ℓ 2

norms, as a regularizer, is proposed in this paper. The principle of alternating direction method of multipliers (ADMM) is introduced to tackle the non-convex model by facilitating the decomposition of the complex original problem into easily solvable subproblems. The proposed method named

ℓ 1 − 2 -ADMM

is applied to solve the impact force identification problem with unknown force locations, which can realize simultaneous impact localization and time history reconstruction with an under-determined, sparse sensor configuration. Simulations and experiments are performed on a composite plate to verify the identification accuracy and robustness with respect to the noise of the

ℓ 1 − 2 -ADMM

method. Results indicate that compared with other existing regularization methods, the

ℓ 1 − 2 -ADMM

method can simultaneously reconstruct and localize impact forces more accurately, facilitating sparser solutions, and yielding more accurate results.

关键词： impact force identification inverse problem sparse regularization under-determined condition alternating direction method of multipliers

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Shape and topology optimization for tailoring the ratio between two flexural eigenfrequencies of atomic force

Qi XIA,Tao ZHOU,Michael Yu WANG,Tielin SHI

《机械工程前沿（英文）》 2014年第9卷第1期页码 50-57 doi: 10.1007/s11465-014-0286-x

摘要：

In an operation mode of atomic force microscopy that uses a higher eigenmode to determine the physical properties of material surface, the ratio between the eigenfrequency of a higher flexural eigenmode and that of the first flexural eigenmode was identified as an important parameter that affects the sensitivity and accessibility. Structure features such as cut-out are often used to tune the ratio of eigenfrequencies and to enhance the performance. However, there lacks a systematic and automatic method for tailoring the ratio. In order to deal with this issue, a shape and topology optimization problem is formulated, where the ratio between two eigenfrequencies is defined as a constraint and the area of the cantilever is maximized. The optimization problem is solved via the level set based method.

关键词： atomic force microscopy cantilever probe eigenfrequency optimization

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on PVDF ultrafiltration membrane fouling behavior under different pH conditions: interface adhesion force

Xudong WANG,Miao ZHOU,Xiaorong MENG,Lei WANG,Danxi HUANG

《环境科学与工程前沿（英文）》 2016年第10卷第4期 doi: 10.1007/s11783-016-0855-9

摘要： pH values of the BSA solution significantly impact the process of membrane fouling. Dramatic flux decline is caused by membrane–BSA adhesion force at start of filtration. XDLVO theory shows the polar or Lewis acid–base interaction plays a major role in membrane fouling. To further determine the fouling behavior of bovine serum albumin (BSA) on different hydrophilic PVDF ultrafiltration (UF) membranes over a range of pH values, self-made atomic force microscopy (AFM) colloidal probes were used to detect the adhesion forces of membrane–BSA and BSA–BSA, respectively. Results showed that the membrane–BSA adhesion interaction was stronger than the BSA–BSA adhesion interaction, and the adhesion force between BSA–BSA-fouled PVDF/PVA membranes was similar to that between BSA–BSA-fouled PVDF/PVP membranes, which indicated that the fouling was mainly caused by the adhesion interaction between membrane and BSA. At the same pH condition, the PVDF/PVA membrane–BSA adhesion force was smaller than that of PVDF/PVP membrane–BSA, which illustrated that the more hydrophilic the membrane was, the better antifouling ability it had. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory predicts that the polar or Lewis acid–base (AB) interaction played a dominant role in the interfacial free energy of membrane–BSA and BSA–BSA that can be affected by pH. For the same membrane, the pH values of a BSA solution can have a significant impact on the process of membrane fouling by changing the AB component of free energy.

关键词： PVDF membrane Membrane fouling Adhesion force Protein Interfacial free energy

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A numerical study of prestressed high strength steel tubular members

Michaela GKANTOU, Marios THEOFANOUS, Charalampos BANIOTOPOULOS

《结构与土木工程前沿（英文）》 2020年第14卷第1期页码 10-22 doi: 10.1007/s11709-019-0547-1

摘要： The structural behavior of prestressed high strength steel (HSS) tubular members is investigated through the execution of advanced finite element modeling. Numerical models are developed and validated against published experimental data on HSS tubular members subjected to different levels of initial prestress and loaded either in tension or compression. The effect of the presence or absence of grouting on the strength and ductility of the members is also considered. To numerically replicate the structural response recorded in the tests, some key modeling features including the employed numerical solver, the adopted material models and the element types warrant careful consideration. Upon developing of the finite element models, the numerically generated ultimate loads, the corresponding failure modes and the full load-deformation curves are compared to the experimental ones, indicating a successful validation. As anticipated, prestressing enhances the load-bearing capacity for the tensile members, whereas it is detrimental for the compressive ones. A series of parametric studies is performed to assess the influence of key factors on the structural response of prestressed HSS members and the obtained results are discussed. Design guidance for tensile and compressive prestressed tubular members is also provided.

关键词： finite element prestressing tubular members grout high strength steel

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Nonlinear sealing force of a seawater balance valve used in an 11000-meter manned submersible

《机械工程前沿（英文）》 2023年第18卷第1期 doi: 10.1007/s11465-022-0726-y

摘要： Balance valve is a core component of the 11000-meter manned submersible “struggle,” and its sealing performance is crucial and challenging when the maximum pressure difference is 118 MPa. The increasing sealing force improves the sealing performance and increases the system’s energy consumption at the same time. A hybrid analytical–numerical–experimental (ANE) model is proposed to obtain the minimum sealing force, ensuring no leakage at the valve port and reducing energy consumption as much as possible. The effects of roundness error, environmental pressure, and materials on the minimum sealing force are considered in the ANE model. The basic form of minimum sealing force equations is established, and the remaining unknown coefficients of the equations are obtained by the finite element method (FEM). The accuracy of the equation is evaluated by comparing the independent FEM data to the equation data. Results of the comparison show good agreement, and the difference between the independent FEM data and equation data is within 3% when the environmental pressure is 0–118 MPa. Finally, the minimum sealing force equation is applied in a balance valve to be experimented using a deep-sea simulation device. The balance valve designed through the minimum sealing force equation is leak-free in the experiment. Thus, the minimum sealing force equation is suitable for the ultrahigh pressure balance valve and has guiding significance for evaluating the sealing performance of ultrahigh pressure balance valves.

关键词： seawater balance valve sealing performance hybrid ANE model FEM minimum sealing force equation