基于中主应力的岩石统计损伤软化模型参数研究

岩石本构关系问题一直是岩石力学研究的重点问题,基于损伤力学理论,假设岩石的损伤变量分别服从幂函数分布与正态分布,建立考虑中主应力影响的模型,总结参数规律。通过两种分布函数所建立的岩石统计损伤软化本构模型与试验结果对比,以及分析损伤变量D的数值变化探讨模型适用性,研究表明:建立的模型曲线均能够较为理想地与实验曲线吻合,与岩石材料的力学性质基本吻合。而正态分布函数模型较幂函数分布模型的损伤变量D演化趋势更为合理。     

Prediction of the fatigue life of slender web plates using fracture mechanics concepts

The results of a series of fatigue tests, on slender plate girders subjected to repeated shear loading, are summarised and used to establish a lower bound fatigue strength curve for the welded web boundary, based on geometric or principal surface stress ranges. The propagation of a semi-elliptical surface crack, through the thickness of a plate, is studied using fracture mechanics concepts. An extensive parametric study indicates that the initial crack size and aspect ratio, the geometric stress concentration at the weld toe, and the plate thickness, all have a significant influence on fatigue strength. It is concluded that the fracture mechanics approach requires specification of a number of parameters which are difficult to determine in practice. However, having specified a realistic crack size and aspect ratio and an approximate stress concentration at the weld toe, the solution can be calibrated against available experimental fatigue strength curves.     

Predicting the removal of soluble organic contaminants by lime softening

The removal of organic contaminants by lime softening and molecular characteristics influencing removal were experimentally and theoretically examined. Coprecipitation appeared to be the major removal mechanism for organic substances in low concentrations, and only those substances able to adsorb onto CaCO₃ were able to be removed by lime softening. All of the removable anionic compounds were able to coordinate with Ca²⁺ to form relatively insoluble complexes. Fatty acids, which form relatively soluble complexes with Ca²⁺, and hydrophobic chemicals unable to coordinate with Ca²⁺ were not removed.Molecular characteristics influencing removal included molecular charge, functionality, degree of polymerization, molecular geometry and affinity for water. In general, softening is effective in removing polymeric electrolytes possessing acidic oxygen-containing residues, such as carboxyl, phenol, enol, phosphoryl, phosphonyl, sulfuryl and sulfonyl groups. Simple monomeric molecules are not expected to be effectively removed unless they polymerize or possess phosphorus-containing functional groups such as phosphoryl and phosphonyl.     

Shear lag analysis by the adaptive finite element method: 1. Analysis of simple plated structures

Due to the presence of sharp stress gradients, traditional finite element analysis using uniform meshes for the solution of shear lag problems for thin-walled structures is inefficient and will result in inaccurate values of effective breadth ratio. By using the adaptive finite element analysis, it is possible to obtain results with predetermined accuracy with a minimum amount of computational cost. An adaptive finite element analysis procedure is used to deal with the problem of shear lag effects of plated structures with arbitrary dimensions and geometry. This study consists of two parts. In Part 1 of the study, shear lag effects in simple plated structures, such as straight rectangular, single-cell box girders are studied. In Part 2 of the study, the adaptive refinement procedure will be extended to the shear lag analysis of complex plated structures such as core walls with openings, multi-cell box girders and box girders with curve flanges.     

The characterisation of geosynthetic interface friction by means of the inclined plane test

The paper focuses on the evaluation of the shear strength in conditions of low normal stress of various geosynthetic-geosynthetic interfaces, which are typical of landfill cover systems, by means of the inclined plane test, with the aim of studying the friction mobilisation in relation to various kinematic behaviours. The results of three different methods to evaluate the angle of friction were analysed, together with the sensitivity of the interfaces in relation to the wear effect and the influence of the state of hydration. The results showed very different responses of the interfaces to the shear stress, which involved three main types of sliding mechanisms, referred to as sudden, gradual and uneven sliding. Another outcome observed was that the shear strength of geosynthetic-geosynthetic interfaces cannot always be properly characterised following the procedure proposed by the European standard for soil-geosynthetic interfaces (EN ISO 12957–2), since the actual mobilised kinematic behaviour should be taken into consideration. In this regard, the paper provides some hints on the choice of the more representative parameter of friction for each type of sliding. A particular focus was given to the case of gradual sliding interfaces, for which the static friction is difficult to detect due to the very slow movements; for practical purposes, the design friction of these interfaces should be evaluated by using an adequate safety factor with respect to the friction evaluated at 1 mm of displacement.     

Shear lag analysis by the adaptive finite element method: 2. Analysis of complex plated structures

The adaptive finite element analysis procedure proposed in Part 1 of this study is employed to solve shear lag problems for complex plated structures with more general and complex geometries, including core walls with openings, multi-cell box girders and box girders with curved flanges. By using the adaptive finite element method, parametric studies were carried out to investigate the influence of some key geometrical parameters on the shear lag effect for these types of structure. In addition, it is found that the adaptive finite element method is a convenient tool for the shear lag analysis of structures with complicated geometry and multiple loading conditions, and could be used in day-to-day analyses.     

信息技术支持下的课程思政教学模式与实践研究——以工程力学课程为例

信息技术的迅速发展给高等教育教学带来巨大的冲击。培养德才兼备的高质量工程类人才，探究信息技术支持下的课程思政教学模式，实现专业课与思政课协同育人具有十分重要的意义。经过4年课程思政教学实践，厘清课程思政的概念和实践意义，总结工程力学课程思政教学实践中存在的问题，如学生参与度相对较低、课程思政运用的教学手段相对传统、课程思政开展的教学环节相对单一等。针对上述问题，明确工程力学课程教学内容各模块的能力目标、知识目标与育人目标，并提出多媒体的利用和微课的制作以提高课程思政学生参与感，桥梁模型的加载比拼与有限元软件的模拟分析以创新课程思政展现形式，学习通的加入和新媒体平台的融合以丰富课程思政实施手段等对策。最后，以梁的合理设计这节课为例，通过教学设计详细说明基于信息技术支持下的工程力学课程思政教学模式。     

Evaluation of the ground-coupled quasi-stationary heat transfer in buildings by means of an accurate and computationally efficient numerical approach and comparison with the ISO 13370 procedure

The purpose of this article is to present and validate a computationally efficient numerical approach for the calculation of the ground-coupled heat transfer in buildings with periodic boundary conditions. When the boundary conditions of the heat transfer problem are described by periodic functions, it is possible to consider the transient state problem as a quasi-stationary problem with considerable savings in terms of computational time. The method is presented in detail from a mathematical point of view, together with a validation for two simple cases of slab-on-grade thermal losses, four comparisons with the ISO 13370:2007 procedure, a case with a complex shape and an evaluation of the computational efficiency.     

Determination of rock mass deformation modulus by means of traveling load tests—Part I: Theory of the traveling load test in an open pit

A new scheme named the Traveling Load Test is proposed to measure the macroscopic deformation modulus of the floor rock mass in an open pit, covering a volume of rock mass much larger than conventional loading tests. Facility of the test includes extra-large excavators as load-sources on the flat surface and high-resolution borehole tilt-meters installed in rock to detect the microscopic tilt induced by the load. Emphasis is given to the theory of deformation modulus determination, which is applicable to the field where the floor is fully covered by an accumulation of loose blocks of stone produced by blasting damage and/or stress relief. The relation between the induced tilt and the traveling load is formulated, and subsequently it is shown how the deformation modulus is determined by analyzing the induced tilt-loading distance curve, within acceptable engineering accuracy.