Nonlinear constitutive models of rock structural plane and their applications

Structural planes play an important role in controlling the stability of rock engineering,and the influence of structural planes should be considered in the design and construction process of rock engineering.In this paper,mechanical properties,constitutive theory,and numerical application of structural plane are studied by a combination method of laboratory tests,theoretical derivation,and program development.The test results reveal the change laws of various mechanical parameters under different roughness and normal stress.At the pre-peak stage,a non-stationary model of shear stiffness is established,and threedimensional empirical prediction models for initial shear stiffness and residual stage roughness are proposed.The nonlinear constitutive models are established based on elasto-plastic mechanics,and the algorithms of the models are developed based on the return mapping algorithm.According to a large number of statistical analysis results,empirical prediction models are proposed for model parameters expressed by structural plane characteristic parameters.Finally,the discrete element method(DEM)is chosen to embed the constitutive models for practical application.The running programs of the constitutive models have been compiled into the discrete element model library.The comparison results between the proposed model and the Mohr-Coulomb slip model show that the proposed model can better describe nonlinear changes at different stages,and the predicted shear strength,peak strain and shear stiffness are closer to the test results.The research results of the paper are conducive to the accurate evaluation of structural plane in rock engineering.

Toward understanding the role of genomic repeat elements in neurodegenerative diseases

Neurodegenerative diseases cause great medical and economic burdens for both patients and society;however, the complex molecular mechanisms thereof are not yet well understood. With the development of high-coverage sequencing technology, researchers have started to notice that genomic repeat regions, previously neglected in search of disease culprits, are active contributors to multiple neurodegenerative diseases. In this review, we describe the association between repeat element variants and multiple degenerative diseases through genome-wide association studies and targeted sequencing. We discuss the identification of disease-relevant repeat element variants, further powered by the advancement of long-read sequencing technologies and their related tools, and summarize recent findings in the molecular mechanisms of repeat element variants in brain degeneration, such as those causing transcriptional silencing or RNA-mediated gain of toxic function. Furthermore, we describe how in silico predictions using innovative computational models, such as deep learning language models, could enhance and accelerate our understanding of the functional impact of repeat element variants. Finally, we discuss future directions to advance current findings for a better understanding of neurodegenerative diseases and the clinical applications of genomic repeat elements.

An 8-Node Plane Hybrid Element for StructuralMechanics Problems Based on the Hellinger-Reissner Variational Principle

The finite element method (FEM) plays a valuable role in computer modeling and is beneficial to the mechanicaldesign of various structural parts. However, the elements produced by conventional FEM are easily inaccurate andunstable when applied. Therefore, developing new elements within the framework of the generalized variationalprinciple is of great significance. In this paper, an 8-node plane hybrid finite element with 15 parameters (PHQ8-15β) is developed for structural mechanics problems based on the Hellinger-Reissner variational principle.According to the design principle of Pian, 15 unknown parameters are adopted in the selection of stress modes toavoid the zero energy modes.Meanwhile, the stress functions within each element satisfy both the equilibrium andthe compatibility relations of plane stress problems. Subsequently, numerical examples are presented to illustrate theeffectiveness and robustness of the proposed finite element. Numerical results show that various common lockingbehaviors of plane elements can be overcome. The PH-Q8-15β element has excellent performance in all benchmarkproblems, especially for structures with varying cross sections. Furthermore, in bending problems, the reasonablemesh shape of the new element for curved edge structures is analyzed in detail, which can be a useful means toimprove numerical accuracy.

Studying the performance of fully encapsulated rock bolts with modified structural elements

Numerical simulation is a useful tool in investigating the loading performance of rock bolts.The cable structural elements(cableSELs)in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues.In this study,the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model.Furthermore,the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs.Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts.Based on the modified cableSELs,the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied.The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently.With the bolt diameter increasing,the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour.Moreover,after the rock bolt was loaded,the position where the maximum shear stress occurred was variable.Specifically,with the continuous loading,it shifted from the rock bolt loaded end to the other end.

Subsurface Structural Elements Delineation Using Electrical Resistivity Method—A Pointer to Groundwater Exploration:Case Study of Northcentral Part of Futa Campus,Southwestern Nigeria

Electrical resistivity survey was carried out as part of an integrated study of a portion of Federal University of Technology Akure,Campus,South-- western Nigeria—a Basement terrain,to unravel the rock types;delineate structural elements such as fractures and determine the ground water zones which could be pin-pointed for water borehole drilling. Thirty-three(33) Vertical Electrical Sounding(VES) along seven traverse lines using the

STIFFNESS EQUATION OF FINITE SEGMENT FOR FLEXIBLE BEAM-FORMED STRUCTURAL ELEMENTS

The finite segment modelling for the flexible beam-formed structural elements is presented, in which the discretization views of the finite segment method and the difference from the finite element method are introduced. In terms of the nodal model, the joint properties are described easily by the model of the finite segment method, and according to the element properties, the assumption of the small strain is only met in the finite segment method, i. e., the geometric nonlinear deformation of the flexible bodies is allowable. Consequently,the finite segment method is very suited to the flexible multibody structure. The finite segment model is used and the are differentiation is adopted for the differential beam segments. The stiffness equation is derived by the use of the principle of virtual work. The new modelling method shows its normalization, clear physical and geometric meanings and simple computational process.

Deformation warning index for reinforced concrete dam based on structural health monitoring data and numerical simulation

The material mechanical parameters of the dam body and foundation will change when a dam is reinforced during the aging process.This causes significant changes in the structural state of the project and makes it difficult to ensure its structural safety.In this study,a new deformation warning index for reinforced concrete dams was developed according to the prototype monitoring data,statistical models,three-dimensional finite element model(FEM)numerical simulation,and the critical conditions of the dam structure.A statistical model was established to separate the water pressure component.Then,a three-dimensional FEM of the reinforced concrete dam was constructed to simulate the water pressure component.Furthermore,the deformation components that affected the mechanical parameters of the dam under the same amount of reservoir water level change were separated and quantified accurately.In addition,the method for inversion of comprehensive mechanical parameters after dam reinforcement was used.The influence mechanisms of the deformation behavior of concrete dams under the reservoir water level and temperature changes were investigated.A new deformation warning index was developed by combining the forward-simulated critical water pressure component and temperature component in the period of extreme temperature decrease with the aging component separated by the statistical model.The new deformation warning index considers the structural state of the dam before and after reinforcement and links the structural strength criterion and the deformation evolution mechanisms.It provides a theoretical foundation and decision support for long-term service and operation management of reinforced dams.

Mass-Stiffness Templates for Cubic Structural Elements Dedicated to Professor Karl Stark Pister for his 95th birthday

1 This paper considers Lagrangian finite elements for structural dynamics constructed with cubic displacement shape functions.The method of templates is used to investigate the construction of accurate mass-stiffness pairs.This method introduces free parameters that can be adjusted to customize elements according to accuracy and rank-sufficiency criteria.One-and two-dimensional Lagrangian cubic elements with only translational degrees of freedom(DOF)carry two additional nodes on each side,herein called side nodes or SN.Although usually placed at the third-points,the SN location may be adjusted within geometric limits.The adjustment effect is studied in detail using symbolic computations for a bar element.The best SN location is taken to be that producing accurate approximation to the lowest natural frequencies of the continuum model.Optimality is investigated through Fourier analysis of the propagation of plane waves over a regular infinite lattice of bar elements.Focus is placed on the acoustic branch of the frequency-vs.-wavenumber dispersion diagram.It is found that dispersion results using the fully integrated consistent mass matrix(CMM)are independent of the SN location whereas its lowfrequency accuracy order is O(κ8),whereκis the dimensionless wave number.For the diagonally lumped mass matrix(DLMM)constructed through the HRZ scheme,two optimal SN locations are identified,both away from third-points and of accuracy order O(κ8).That with the smallest error coefficient corresponds to the Lobatto 4-point integration rule.A special linear combination of CMM and DLMM with nodes at the Lobatto points yields an accuracy of O(κ10)without any increase in the computational effort over CMM.The effect of reduced integration(RI)on both mass and stiffness matrices is also studied.It is shown that singular mass matrices can be constructed with 2-and 3-point RI rules that display the same optimal accuracy of the exactly integrated case,at the cost of introducing spurious modes.The optimal SN location in two-dimensional,bicubic,isoparametric plane stress quadrilateral elements is briefly investigated by numerical experiments.The frequency accuracy of flexural modes is found to be fairly insensitive to that position,whereas for bar-like modes it agrees with the one-dimensional results.

Construction of Structural Elements and Characteristic System of Athletes’Cognitive Ability

Cognitive ability is important component of competitive ability of athletes,an important content of winning elements in sports,and an important topic of modern sports training and scientific research.These problems will restrict the improvement of athletes’cognitive ability and mental level.Based on the theory of psychology,use multiple hierarchical thinking,research cognitive theory of sports and the characteristics of cognitive ability of elite athletes,research the structure element system of cognitive ability,construct a two-level structure model of the cognitive ability of excellent athletes,summarize specific characteristics of the first level elements,and apply psychological cognitive theory to the training of modern Olympic Games mobilization,so as to provide valuable cognitive training,psychological training,and intelligence training for athletes theoretical guidance.

A Simple and Efficient Structural Topology Optimization Implementation Using Open-Source Software for All Steps of the Algorithm:Modeling, Sensitivity Analysis and Optimization

This work analyzes the implementation of a continuous method of structural topology optimization(STO)using open-source software for all stages of the topology optimization problem:modeling,sensitivity analysis and optimization.Its implementation involves three main components:numerical analysis using the Finite Element Method(FEM),sensitivity analysis using an Adjoint method and an optimization solver.In order to allow the automated numerical solution of Partial Differential Equations(PDEs)and perform a sensitivity analysis,FEniCS and Dolfin Adjoint software are used as tools,which are open-source code.For the optimization process,Ipopt(Interior Point OPTimizer)is used,which is a software package for nonlinear optimization scale designed to find(local)solutions of mathematical optimization problems.The topological optimization method used is based on the SIMP-Solid IsotropicMaterial with Penalization interpolation.The considered problem is the minimization of compliance/maximization of stiffness,considering the examples of recurrent structures in the literature in 2D and 3D.A density filtering algorithm based on Helmholtz formulation is used.The complete code involves 51 lines of programming and is presented and commented in detail in this article.

A Modified Model for Soil–Structure Interface Considering Random Damage of Mesoscopic Contact Elements

The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process.In this study,the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity.The evolution equation of damage variable is developed based on the Weibull function,which is able to cover a rather wide range of distribution shapes by only two parameters,making it applicable for varying scenarios.Accordingly,a statistical damage model is established by incorporating Mohr–Coulomb strength criterion,in which the interfacial residual strength is considered whereby the strain softening behavior can be described.A concept of“semi-softening”characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening.Finally,a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted.The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature,indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.

The Structural Responses of Columns under Various Loadings

This paper focuses on the seismic resistance of one-storied factories, which are commonly used in China due to their flexibility, low cost, and short construction period. With the increasing demand for construction materials, these factories play a vital role in meeting the demands of urbanization and infrastructure development. The seismic resistance of these factories is critical to ensure safety, and this paper presents research on this topic. The paper highlights the advantages of one-storied factories, such as low maintenance cost and seismic resistance, and emphasizes the importance of conducting research on their seismic resistance to ensure safety in construction projects.

美国“去风险”对中国产业链供应链安全的影响及应对

在大国竞争加剧、突发公共卫生事件冲击和乌克兰危机持续等多重不确定性因素叠加的背景下,全球产业链供应链正进入重要的重塑阶段。与此同时,美国先后提出对华“脱钩”“去风险”,以减少其对中国产业链供应链的依赖,这严重影响了全球产业链供应链的稳定畅通。首先,本文界定产业链供应链安全范畴主要包括主体要素安全和结构要素安全。其次,辨析美国“脱钩”“去风险”政策意图的异同,并就现阶段美国“去风险”对中国产业链供应链安全的主要影响和中国所面临的现实挑战进行论述。分析发现,美国“去风险”对中国产业链供应链安全的主要影响包括:一是美国通过控制核心技术、中间品出口和关键资源危及中国产业链供应链主体要素安全。二是通过制造业回流、“近岸外包”“友岸外包”重塑全球产业空间布局,威胁中国产业链供应链结构要素安全。三是通过友好国家网络拉拢盟友,增加中国产业链供应链被排除风险。最后,本文据此提出中国如何在美国“去风险”背景下维护产业链供应链安全稳定的政策建议。

耐张型悬索支撑输电结构风振非线性有限元分析

耐张型悬索支撑输电结构是一类适用于山地地形的新型输电结构,其主要受风荷载控制。为此,该研究发展了该输电结构风振非线性有限元分析模型并开展了结构风振响应分析。考虑结构的几何非线性,通过单元应变能与位移的关系推导了支撑悬索和输电线的三维杆单元切线刚度矩阵;给出了支撑悬索和输电线的单元质量矩阵、阻尼矩阵以及由风荷载等效而得的单元节点荷载向量;基于非线性有限元理论,建立了耐张型悬索支撑输电结构风振非线性动力方程,并采用了结合Newton-Raphson迭代法的Newmark-β法求解非线性动力方程;通过所建立的动力学分析模型对两跨耐张型悬索支撑输电结构进行了风致非线性振动分析。算例分析结果表明:①提出的模型具有较好的计算精度和较高的计算效率;②悬索支撑导线部分的低阶固有频率比悬索支撑地线部分的低阶固有频率更低;③该输电结构的输电线位移响应受风荷载影响较大;④输电线侧向位移和支撑悬索张力受风速和风向角影响均较显著。

环境规制、数据要素配置水平与产业结构调整

文章基于数字经济、绿色经济发展深刻影响产业结构转型升级进程这一背景,首先在理论分析的基础上构建了数据要素配置水平综合评价指标体系;然后采用Dagum基尼系数对数据要素配置水平的空间差异及主要来源进行分解测算;最后,基于2012—2019年省级面板数据探讨了环境规制的结构调整红利及数据要素有效配置的渠道效应。研究结果显示,我国数据要素配置水平总体空间差异明显,且区域间差异为主要来源,区域内差异次之。环境规制对产业结构升级存在先促进后抑制的“倒U”型影响,数据要素配置也有显著促进作用。动态边际效应结果显示,在研究期内环境规制所带来的产业结构“调整红利”正在逐渐弱化,数据要素优化配置可充当环境规制促进产业结构升级的有效路径,且从子维度来看,数据传播共享的渠道效应最为显著。数据要素配置的网络外部性特征对环境规制和产业结构优化的调节作用在不同地区所呈现的阶段性特征不同。

知识复杂性的测度方法综述与比较

[研究目的]复杂知识是突破关键核心技术的基础支撑,也是企业或区域建立竞争优势的关键要素。该文旨在全面把握知识复杂性测度方法的研究现状与前沿进展,为知识复杂性的深入研究提供测度理论基础。[研究方法]通过梳理国内外知识复杂性研究的相关文献,详细介绍三种主要的知识复杂性测度方法的核心思想、理论基础和计算过程,并进一步对比分析不同方法的适用层次和优缺点,最后提出未来研究方向。[研究结论]反射法主要基于知识的空间分布异质性间接衡量知识复杂性,虽然原理简单且操作相对容易,但无法揭示知识复杂性的本质特征;元素依赖性指数利用知识组合频次衡量知识元素之间的相互依赖程度,进而反映知识复杂性,忽视了其他影响知识组合的因素;结构多样性指数通过知识组合网络拓扑结构的多样性反映知识复杂性,综合考虑多个网络结构指标,并经过大量数值模拟检验,但存在估计结果不稳定、仅适用于二值网络等问题。

基于属性的概念化:制度本体研究的必要性与路径

制度本体的研究现状与制度之于人类生活的重要性并不相称,制度研究有必要返回本体,明确存在。解读制度理论的制度理解并指出它所引发的本体认知困惑,确立了制度本体研究的必要性。本体在于内涵,内涵首要是本质,有抱负的研究者都试图给出事物的本质性定义,但此定义往往可欲难求。一个可行的操作化步骤是,确定本体的属性。制度学界普遍接受的“制度即结构”可以明确为“制度即要素结构”,并可解构为要素之制、载体之制与结构之制。确定本体属性、要素化属性并将其概念化,应是可行的本体研究策略或路径。由此获得的概念语言暨制度本体词汇有助于校准本体描述,同时可作为中介术语沟通制度研究,推动制度知识的共享与交流。

基于BIM的公路工程标准化EBS分解方法

工程结构分解(EBS)是公路工程全寿命周期信息化管理的基础。为了提高公路工程建设期信息化水平,基于BIM技术应用,提出了公路工程标准化EBS分解方法。标准化分解方法根据工程中不同路段,梳理专业划分以及空间位置划分原则,并依据行业标准,确定标准化EBS结构的叶子节点,提供公路工程EBS结构树模板示例。研究结果旨在提高高速公路数字化交付中的数据处理标准建设,为实施公路工程数字化提供基础支持。

基于Python的平面杆系结构有限元分析

基于Python程序,将杆单元位移不连续、理想刚杆两种力学对象关联统一,开展平面杆系结构有限元模型分析,并实现一种基于“变量标记”的自由度集中处理的计算模式.基于虚功原理引入并推证刚体荷载传递定理,表明耦合单元、刚杆及忽略某一自由度的有限元内置算法处理过程中,实质是将单元刚度矩阵进行“刚化”处理.算例分析表明,“变量标记”的计算模式与单元刚度矩阵的“刚化”处理,具有力学模型的普适性和统一性、编程的可行性以及结果的可靠性等特点,能解决平面任意杆系结构的建模问题.研究结果表明,“主从结点”、“刚杆”等建模方法,对于进一步开展有限元二次开发、大变形以及非线性等功能性扩展等有重要的参加价值,证明将Python程序应用于结构有限元分析的可行性.

纤维金属板蜂窝夹芯结构鸟体高速冲击损伤分析

纤维金属板蜂窝夹芯结构作为一种轻质航空结构,研究其抗鸟体高速冲击性能具有重要的现实意义。本文提出一种基于连续介质损伤力学的有限元模型,研究鸟体高速冲击下纤维金属板蜂窝夹芯结构的力学行为及损伤机理。采用光滑粒子流体动力学(Smooth particle hydrodynamics, SPH)法对鸟体类流体力学行为进行建模;采用Johnson-Cook模型模拟金属层冲击力学响应;采用三维Hashin准则,考虑应变率效应,模拟复合材料层板面内损伤演化;采用界面单元模拟层间分层现象。编写用户材料VUMAT子程序,实现基于ABAQUS/Explicit软件平台的数值求解。探讨鸟体速度、蜂窝高度和面板厚度对纤维金属板蜂窝夹芯结构鸟体冲击性能的影响,分析预应力条件下纤维金属板蜂窝夹芯结构鸟体高速冲击损伤特性,为夹芯结构鸟体冲击问题数值分析提供一定的参考。