弹丸侵彻无钢筋混凝土的数值模拟

采用二维梁-颗粒模型BPM2D（beam-particle model in two dimensions）模拟了刚性弹丸侵彻无钢筋混凝土的过程。离散元法（DEM）和有限元法（FEM）等数值计算方法各有其优势,同时也都存在不足之处：离散元法适于处理由连续介质向非连续介质转化的破坏问题,但对于连续体计算结果精度不高;有限元法适于预测材料破坏的区域,但难以直接用于计算脆性材料破坏过程,因此将两种方法结合可以形成一种较好的混合模型。梁-颗粒模型BPM2D是基于离散元法,结合有限元法开发的二维数值计算模型,采用3种类型梁单元形成混凝土数值试样,每种类型梁单元的力学性质均按韦伯（Weibull）分布随机赋值,以模拟混凝土细观结构的非均匀性,同时梁单元的强度随应变率不同而变化。利用此模型分析了弹丸侵彻下混凝土的破坏过程,并给出侵彻过程弹丸减速度-时间历程曲线。比较计算结果与试验数据表明梁-颗粒模型可有效应用于计算和模拟脆性材料动态破坏问题。     

Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration

The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.     

基于响应面法的软岩隧道湿喷纤维混凝土支护结构可靠度分析

由于湿喷纤维混凝土支护结构物理、力学参数和喷层厚度的离散性及混凝土强度破坏准则难以用支护材料参数显式表达,对该类隧道支护结构进行可靠度分析十分困难,提出采用响应面方法计算湿喷纤维混凝土支护结构的可靠度方法,并给出了计算流程,其中围岩-支护结构的确定性分析采用非线性有限元方法,可靠度分析采用2次响应面法.以赣州-龙岩铁路金华山软岩隧道湿喷纤维混凝土支护结构为研究对象,对该支护结构的可靠度进行分析与计算.分析结果表明,金华山隧道湿喷纤维混凝土支护结构可靠度指标高,处于安全状态.