Discrete fracture in high performance fibre reinforced concrete materials

In this paper a simple, but effective methodology to simulate opening mode fracture in high performance fibre reinforced concrete is presented. The main contribution of the paper is a technique to extrapolate the load displacement curves of three point bending experiments on fibre reinforced concrete. The extrapolation allows the full work of fracture to be determined, from which the fracture energy may be obtained. The fracture energy is used in the definition of a cohesive softening function with crack tip singularity. The softening relation is implemented in an embedded discontinuity method, which is employed for the numerical simulation of three point bending experiments. The experimental work includes a size effect study on three point bending specimens. The numerical simulation provides a satisfactory prediction of the flexural behaviour and the size effect observed in the experiments.     

农村公路桥梁损伤状况调查研究

通过湖北黄石地区农村公路桥梁的实地调查,采用权重综合评定法,对农村公路桥梁按损伤程度进行了分类研究,结果表明中等损伤的三类桥居多,损伤基本集中在7个部位,病害类型以混凝土裂缝、混凝土腐蚀、钢筋锈蚀、桥面铺装损伤为主。为后期桥梁加固提供了调查依据。     

大孤山铁矿边坡岩体结构数字识别及力学参数研究

针对目前岩体结构面信息获取主要以人工现场接触测量为主,劳动强度大、效率低下的现状,借助于先进的ShapeMetrix 3D三维数字摄影测量系统,对大孤山铁矿边坡岩体结构面进行摄影测量,对获取到的结构面进行分组、分析,得到结构面各种几何信息的详细数据,并对其进行数理统计计算、分析,拟合出结构面各种几何信息的概率分布模型。采用蒙特卡洛方法编制的程序和根据数字摄影测量系统得到的统计数据,模拟岩体内部结构面三维分布情况。在此基础之上,采用修正广义Hoek-Brown准则,估计节理化岩体强度,得到岩体强度指标。根据已获得的结构面三维分布情况和岩体强度指标综合评价了大孤山铁矿边坡岩体稳定性。     

An extended displacement discontinuity method for analysis of stress wave propagation in viscoelastic rock mass

An extended displacement discontinuity method (EDDM) is proposed to analyze the stress wave propagation in jointed viscoelastic rock mass (VRM).The discontinuities in a rock mass are divided into two groups.The primary group with an average geometrical size larger than or in the same order of magnitude of wavelength of a concerned stress wave is defined as "macro-joints",while the secondary group with a high density and relatively small geometrical size compared to the wavelength is known as "micro-defects"...     

Beyond the group mind: A quantitative review of the interindividual-intergroup discontinuity effect.

This quantitative review of 130 comparisons of interindividual and intergroup interactions in the context of mixed-motive situations reveals that intergroup interactions are generally more competitive than interindividual interactions. The authors identify 4 moderators of this interindividual-intergroup discontinuity effect, each based on the theoretical perspective that the discontinuity effect flows from greater fear and greed in intergroup relative to interindividual interactions. Results reveal that each moderator shares a unique association with the magnitude of the discontinuity effect. The discontinuity effect is larger when (a) participants interact with an opponent whose behavior is unconstrained by the experimenter or constrained by the experimenter to be cooperative rather than constrained by the experimenter to be reciprocal, (b) group members make a group decision rather than individual decisions, (c) unconstrained communication between participants is present rather than absent, and (d) conflict of interest is severe rather than mild. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the elimination of quadrature subcells for discontinuous functions in the eXtended Finite‐Element Method

The introduction of discontinuous/non‐differentiable functions in the eXtended Finite‐Element Method allows to model discontinuities independent of the mesh structure. However, to compute the stiffness matrix of the elements intersected by the discontinuity, a subdivision of the elements into quadrature subcells aligned with the discontinuity line is commonly adopted. In the paper, it is shown how standard Gauss quadrature can be used in the elements containing the discontinuity without splitting the elements into subcells or introducing any additional approximation. The technique is illustrated and developed in one, two and three dimensions for crack and material discontinuity problems. Copyright © 2005 John Wiley & Sons, Ltd.     

Resistivity Survey of the Subsurface Conditions in the Estuary of the Rio de la Plata

An electrical resistivity survey was performed at the estuary of the Rio de la Plata, as part of more comprehensive geotechnical investigations of the subsurface conditions. The studies were required for the emplacement of a 3.5-m-diameter conduit proposed for the discharge of the treated wastewater of the city of Buenos Aires. The soil profile at the site consists mainly of clays and silts underlain by a layer of dense sand. The dense sand layer is a confined aquifer, and the project required that the depth to the sand layer be perfectly determined. Previous geophysical surveys at the site and the general geotechnical conditions showed the inadequacy of seismic methods, which are usually adopted in similar environments. The resistivity method was determined to be a reliable alternative, even though there has been little experience in surveying shallow depth water for geotechnical investigations. The four-electrode Schlumberger electrode array was adopted for the resistivity survey. Some of the test devices were developed especially for the purpose of this project. Calibration of the method was achieved with data obtained from boreholes. The results show that the resistivity technique performed satisfactorily to the 40?m depth required in this project. As a result of the survey, the next geotechnical investigation was focused on a more reduced area and the required number of boreholes was reduced substantially.     

Influence functions of the displacement discontinuity method for anisotropic bodies

In this study, the boundary element equations are obtained from the influence functions of a displacement discontinuity in an anisotropic elastic medium. For this purpose, Kelvin fundamental solutions for anisotropic media on infinite and semi-infinite planes are used to form dipoles from singular loads. Various combinations of these dipoles are used to obtain the influence functions of the displacement discontinuity. Boundary element equations are then derived analytically by the integration of these influence functions on a constant element which results in a linear system for unknown displacement discontinuities. The boundary integrals are calculated in closed form over constant elements. The obtained formulation is applied to a number of classical engineering problems.Tel.: +90-212-285-65-85, 90-212-285-37-07     

微带不连续性的神经网络模型

本文采用多层感知器建立了微带不连续性的神经网络模型。