Damage Tensor Analysis on Regional Seismic Status

INTRODUCTIONThe introductiontothe damage variable was made originally by Kachanov (1958) and Rabotnov(1963) .As a factor of deterioration in material or rock,damage develops with the changing of loadand environment . The damage variable describes the characteristics of material in the stage frommicrofissure generationto macrofracture formation.Grady and Kipp (1980) loaded oil shale at a constant strainrate andits damage degreeincreasedrapidly. Whenthe load reachedits utmost ,collapse occ…     

地震滑坡灾害下输电杆塔灾损评估研究

为快速评估地震与滑坡灾害对输电杆塔的损毁作用,辅助风险防控措施制定与应急指挥人员决策,研究输电杆塔在地震与滑坡灾害中的损失概率模型。使用蒙特卡洛方法模拟地震震级与震源点坐标,结合峰值地面加速度与脆弱性曲线构建输电杆塔震损概率模型。基于Newmark理论与材料力学原理,构建地震诱发滑坡概率模型及杆塔滑坡冲击损毁概率模型。对我国西南部某区域输电杆塔进行地震与滑坡灾损分析,得到研究区域内各输电杆塔震损概率及滑坡冲击损毁概率。研究结果表明,输电杆塔损毁概率随震级的增大而增大,震级相同时输电杆塔损毁概率主要取决于震中距。滑坡体高度及杆塔与坡脚距离是影响杆塔损毁概率的主要因素,较高处的滑坡体下落时将重力势能转化为动能,进而冲击作用于杆塔,而较小的杆塔与坡脚距离将导致摩擦损耗较小。对于损毁概率较高的杆塔,应采取避让、迁移等措施,降低滑坡灾害的影响。     

裂隙型硬粘土的力学模型及其在边坡工程中的应用

硬粘土是介于软岩和硬土之间的一种介质, 其中含有规律分布的裂隙, 具有明显的方向性和各向异性特征; 本文从实际应用的角度出发, 提出一种适用于裂隙性硬粘土的损伤力学模型, 并应用于南水北调中线渠道边坡工程的数值模拟分析。     

Micromechanical Model for Simulating the Fracture Process of Rock

Summary A micromechanical model is proposed to study the deformation and failure process of rock based on knowledge of heterogeneity of rock at the mesoscopic level. In this numerical model, the heterogeneity of rock at the mesoscopic level is considered by assuming the material properties in rock conform to the Weibull distribution. Elastic damage mechanics is used to describe the constitutive law of meso-level elements, the finite element method is employed as the basic stress analysis tool and the maximum tensile strain criterion as well as the Mohr-Coulomb criterion is utilized as the damage threshold. A simple method, similar to a smeared crack model, is used for tracing the crack propagation process and interaction of multiple cracks. Based on this model, a numerical simulation program named Rock Failure Process Analysis Code (RFPA) is developed. The influence of parameters that include the Weibull distribution parameters, constitutive parameters of meso-level elements and number of elements in the numerical model, are discussed in detail. It is shown that the homogeneity index is the most important factor to simulate material failure with this model. This model is able to capture the complete mechanical responses of rock, which includes the crack patterns associated with different loading stages and loading conditions, localization of deformation, stress redistribution and failure process. The numerical simulation of rock specimens under a variety of static loading conditions is presented, and the results compare well with experimental results.     

Degradation of rope properties under increasing monotonic load

This paper describes the development of a computational model to predict the response of synthetic-fiber ropes under both monotonic and cyclic loads. The model addresses the issue of damage to a rope cross-section and its effect on rope response. Isotropic damage is assumed and is therefore characterized by a scalar quantity known as the damage index. The damage index is used to quantify the amount of deterioration that takes place in a damaged rope throughout its loading history. For the current study, data obtained from static tension tests are used to determine the evolution relationship for the damage index. This relationship is based on the stiffness ratio between experimental data and simulation of rope response without any source of damage and is assumed to be described by an exponential equation. Numerical simulations of damaged rope behavior compare well with experimental results.     

云南禄丰—元谋5.1级地震烈度分布及震害因素分析

对2010年2月25日云南省禄丰—元谋5.1级地震现场53个居民点的震害调查资料进行分析,介绍了烈度的分布形状、烈度区面积、范围,分析了局部地形、含煤地层等场地条件对震害异常的影响及各类房屋、生命线工程、水利设施等的震害特征和破坏原因,在此基础上提出了灾区恢复重建的建议。     

横向地震波冲击下建筑结构稳定性变化分析

高层EPS法分析横向地震波冲击下建筑结构稳定性变化时,未进行横向地震波随机过程数学模拟,获取的横向地震波与实测不符,提出一种新的横向地震波冲击下建筑结构稳定性变化分析方法,采用三角级数型非平稳随机过程模型函数,模拟横向地震波非平稳性特征,得到横向地震波模拟曲线,根据该曲线建立建筑结构稳定性动力运动方程,运用Hilber-Hughes-Taylor递推格式求解该方程的安全系数,安全系数越高建筑结构稳定性越强。为研究建筑结构在横向地震波反复荷载作用下的稳定性状态,运用弹塑性损伤模型模拟建筑结构核心筒墙体混凝土,得到用于分析建筑结构稳定性的最大、最小特征值。实验结果表明,所提方法能够分析建筑结构稳定性变化,横向地震波冲击前5 s对建筑结构稳定性影响最大。     

2017年8月8日九寨沟7.0级地震长波辐射异常特征

通过距平方法,研究2017年8月8日九寨沟7.0级地震前震中所在区域（95.00°—110.00°E,25.00°—45.00°N）长波辐射时空演化特征,研究结果表明:①2017年7月,去除背景之后的长波辐射场在震区附近出现显著增强现象,增强区域基本走向与地质构造走向一致,其主体区域沿着巴颜喀拉块体南缘边界带,重要分支横跨巴颜喀拉块体,直接延伸至九寨沟7.0级地震震中;②紧邻九寨沟7.0级地震震中的4个格点在去除背景变化后的长波辐射时序曲线变化特征基本一致,即在2017年7月出现显著大于其他月份的现象。     

钢筋混凝土柱的破坏形态及变形能力研究

对钢筋混凝土（RC）柱在地震作用下的变形性能进行量化,本文从太平洋地震研究中心柱数据库中收集到123根RC柱抗震性能试验数据,提出基于参数剪跨比和弯剪比的RC柱破坏形态判别标准;在弯曲破坏、弯剪破坏、剪切破坏三种破坏形态下,研究了轴压比、剪跨比、配箍特征值等参数对位移角的显著性影响,通过回归分析归纳出三种破坏形态下屈服位移角和极限位移角的回归方程,回归系数显著性概率均小于0.05。结果表明：本文提出的RC柱破坏形态判别标准准确度高,适应性强;位移角线性回归方程具有合理性。