变质量质系的哈密顿原理

在变质量系的第二类拉格朗日方程的基础上 ,进一步导出了原质点的结合与分离同时进行时 ,变质量质系哈密顿原理的表达式 ,其目的是导出哈密顿原理更具有普遍性的表达式 ,该表达式同样可以计算常质量系的问题     

Splitting strength of beams loaded perpendicular to grain by dowel joints

A linear elastic fracture mechanics model for calculation of the splitting strength of dowel-type fastener joints loaded perpendicular to grain (Van der Put/Leijten model) has previously been presented, and now forms the basis for design in Eurocode 5. The original Van der Put/Leijten model was derived using a number of simplifying assumptions, e.g., that the normal forces in the cracked parts of the beam can be ignored, leading to a solution that does not involve the effect of an initial crack. In the present article an extended version of the Van der Put/Leijten model is derived without any simplifying assumptions, and it is shown that the original Van der Put/Leijten model appears as a special case, namely by assuming that only contributions from shear deformations are significant. The model presented here involves the effect of an initial crack and may be characterized as a generalized linear elastic fracture mechanics model. Results of tests showing the influence of initial cracks of various lengths are presented and compared with the predictions.     

A Review of Concrete Damage Constitutive Models

The existing constitutive models of concrete are mainly based on the framework of the classic elastic -plastic models which are rigorous on mathematics, but not coordinated with the failure mechanism of concrete. Researchers of different countries proposed various kinds of damage constitutive models based on the irreversible thermodynamics theory to describe the damage behavior of concrete. This paper presents a review of different models for concrete,analyzes the characteristics of each representative model and studies the scope of their application. On the basis of the review of existing concrete damage models, some new methods can be provided for further research on damage constitutive models.     

PRELIMINARY RESEARCH OF PHOTOELASTIC ISODYNES EXPERIMENTAL TECHNIQUES

The photoelastic isodyne experimental apparatus investigated by authors is presented. The design of the integrating prism ard the relative experimental techniques are discussed,Using this apparatus the two fundamental experiments on the stress analysis of the circular disc loaded along vetical diameter and the determination of the stress intensity factor for the side crack of the extension-loaded plate are completed.     

Engineering Memoir and Features Analysis of Dynamics Phenomena in Yanshitai Mine

The depth of coal mining in Yanshitai mine is over 600 m,dynamics phenomena have been occurred of ter during mining ahd excavating.On the basis of research in Yanshitai mine,this paper recorded the geology and mechanics model of typical dynamics phenomena based on the mining and geology conditions,which have been applied for the mechanism of dynamics phenomena and studied with catastrophe.Meanwhile,the features and influence factor have been studied,and they can be references for mine hazards.     

The use of impulse oscillometry for separate analysis of inspiratory and expiratory impedance parameters in horses: effects of sedation with xylazine

AIM: To improve the outcome of parameters measured by the impulse oscillometry system (IOS) in horses by separate assessment of inspiratory and expiratory impedance spectra in the frequency range between 1 and 10 Hz. As basis for further studies, the influence of sedation with xylazine on respiratory impedance was also investigated. METHODS: (i) The respiratory impedance of 11 horses was measured using IOS before and 6 min after sedation (xylazine; 0.6 mg/kg b.w.). (ii) The time course of impedance parameters in a period of 24 min after administration of xylazine was evaluated in 12 horses at regular intervals of 3 min. Resistance (R(rs)), reactance (X(rs)), and coherence (Co) were calculated as mean spectra (R(rs),X(rs),Co) of the entire measurement as well as separated into inspiration (Ri(rs),Xi(rs),Coi) and expiration (Re(rs),Xe(rs),Coe) at frequencies of 1, 5, and 10 Hz. RESULTS: (i) R(rs), X(rs) as well as Re(rs) and Xe(rs) revealed no significant influence of sedation. However, separate analysis of inspiration and expiration revealed a significant influence of sedation on all inspiratory impedance parameters. (ii) During the 24 min period after sedation, almost all inspiratory parameters were found significantly dependent on the time course of sedation whereas expiratory parameters Re10, Xe1, and Xe5 were not influenced. These results indicate that confounding factors due to sedation act mainly during inspiration. Muscle relaxation in upper airways due to xylazine is suspected to be the main cause of these phenomena.     

Analysis of Concrete Damage Model in Pile Body Stress Test

Automatic pile body stress test system is used in an in-situ static loading test. It’s found that strain process line has a step-like feature. When unloading, as the rebound amount of soil is less than the amount of pile body, negative frictional resistance exists in the soil. It’s considered that concrete damage model can explain the modulus “reduced” phenomenon of calibration section’s concrete. Based on damage mechanics theory, a function of modulus of concrete and its own strain are obtained. According to actual strain of pile body, different modulus are adopted to calculate pile body stress. The in-situ test results show that this method is more reasonable.     

Meso-experimental analysis on fracture characteristics ofJinping bedded marble

The project problem because of wall rock’s deformation fracture in deep-buried and high geostress conditions is very prominent at Jinping hydropower Ⅱ station underground engineering. According to the characteristics of the bedded marble collected from Jinpiing Ⅱ hydropower station auxiliary traffic tunnel in deep-buried area, three-point bending experiment on different bedded direction specimens with SEM high temperature testing system is carried out to test the stress of bedded marble in different directions and the failure mechanism and deformation features of homogeneous marble. In the test, there are 3 groups of specimens, include parallel bedded specimen, vertical bedded specimen and homogeneous marble specimen. The results show that: bedded marble’s bedded feature is because of the banded structure feature between dolomite mineral particles and calcite mineral particles; the fracture mechanism and strength parameter of bedded marble depend on different force directions and mineral composition. Because of the cement capacity between dolomite minerals and particles size, homogeneous marble specimen has the lowest strength. The marble specimens’ deformation shows 3 stages, and because of different fracture mechanisms, the plastic deformation of parallel bedded specimens is more obvious than that of vertical bedded specimen. While the deformation of homogeneous marble can be divided into 2 stages, i.e. before and after peak stage, and the after peak stage shows the complete deformation development process.     

西南山区公路建设场地模糊分类系统研究

通过对西南山区地理、地质情况对公路建设施工难易和路基稳定性情况的研究,筛选出岩体单轴抗压强度、浅层岩溶和山地类型等6个起主要作用的因素,构成影响因素评价集.借鉴岩体分类经验,将公路建设场地分为5类,形成分类决策评语集.基于隶属函数等效性,研究出各因素在各类型中总体隶属函数的构造方法和确定隶属函数具体形式的算法.应用模糊评判原理,确定了从评价因素集到决策评语集的映射关系,构成了西南山区公路建设场地模糊分类系统.利用该系统研究了某山区公路的第3施工合同段的类型,分析结论被作为设计和施工依据之一.