弹丸撞击下钢筋混凝土结构的安全计算与评估

发布时间：2018-05-09 22:02

本文选题：钢筋混凝土靶板 + 弹丸　；参考：《中国科学技术大学》2014年博士论文

【摘要】：钢筋混凝土广泛应用于国防和民用(如核电厂)工程中,研究钢筋混凝土结构在弹丸撞击下的响应和破坏,对工程防护设计和安全评估具有重要的意义。本文的主要目的是预测钢筋混凝土靶板在弹丸撞击发生不同破坏模式时所需要的临界能量,并对钢筋混凝土结构响应进行数值模拟。本文的研究内容主要包含以下几个方面：基于弹丸侵彻力和钢筋混凝土靶板冲击实验数据的基础上,在统一框架内修正了UMIST公式。修正的UMIST公式不仅能适用于平头弹丸,而且适用于非平头弹(如尖头弹、卵形弹和半球形弹等)；不仅能适用于低速撞击,而且也适用于高速撞击；不仅适用于低强度混凝土,而且也适用于高强度混凝土。结果证明修正的公式能在很广的冲击条件内预测在弹丸撞击下钢筋混凝土靶板产生厚度方向开裂破坏、痂斑破坏和贯穿破坏。对刚性平头弹丸撞击下半无限混凝土靶的深侵彻问题进行研究。通过对实验现象的观察,平头弹丸在侵彻过程中会在弹丸前部产生一个“死区”。因此,作为一阶近似可以将平头弹丸侵彻半无限混凝土靶的问题看成是锥形弹侵彻半无限混凝土靶的问题来处理。通过采用刚塑性不可压缩的介质模型,利用滑移线理论方法和虚功率原理,得到了混凝土介质对平头弹丸静阻力部分；再加上由速度效应引起的动阻力,得到混凝土介质对平头弹丸的侵彻阻力。根据所求的混凝土介质阻力,代入到弹丸的运动方程,得出弹丸的侵彻深度公式。该公式预测的弹丸侵彻深度与实验数据吻合得较好。对钢筋混凝土板抗冲剪强度问题进行研究。由于现有的钢筋混凝土板的抗冲剪强度公式中的失效面与真实的失效面并不一致且公式本身并不是无量纲化的,因此现有的公式的适用范围受到一定的限制。本文提出了一个预测钢筋混凝土板在圆柱冲头压入荷载作用下发生冲剪破坏时剪切强度的经验方程,方程中考虑了钢筋量、钢筋间距和跨厚比的影响。通过与实验数据比较,以及与现有的经验公式比较,可以看出本文提出的经验公式具有一定的优越性。基于实验观察和板厚与弹径之比的不同,对钢筋混凝土靶板在平头弹丸低速撞击下的厚度方向开裂破坏进行研究。钢筋混凝土靶板受到平头弹丸低速冲击时一般会发生两种破坏模式,即直接厚度方向开裂破坏,弹丸无明显的侵入；弹丸侵入一定深度后的厚度方向开裂破坏。本文首先建立了弹丸冲击混凝土靶板的侵彻和厚度方向开裂二阶段破坏半分析模型,其次利用本文提出的平头弹丸侵彻混凝土靶板的分析模型得到的侵彻阻力和引入动态增强因子的钢筋混凝土靶板的抗冲剪承载力,得到钢筋混凝土靶板的两种破坏模式的转化条件(破坏模式图)。模型预测与实验数据吻合得较好利用本实验室新建立的混凝土动态本构关系对钢筋混凝土结构在弹丸撞击下的响应和破坏进行数值模拟。该混凝土动态本构模型考虑了压力相关性、应变率效应、Lode角效应、剪切损伤效应和拉伸损伤效应,通过对平头弹丸撞击下的钢筋混凝土靶板响应的数值模拟,得到的钢筋混凝土靶板的破坏形貌与实验观察非常相近,结果令人满意。同时,利用该混凝土动态本构模型对钢筋混凝土板的厚度、钢筋间距和尺寸进行数值模拟研究,得出各因素对钢筋混凝土靶板受到平头弹丸撞击下发生的破坏模式的影响。由于核电厂中的钢筋混凝土结构主要为圆柱壳体和球形壳体,利用数值模拟技术对壳体结构在平头弹丸撞击下产生的破坏情况进行初步研究,结果表明曲率的存在对钢筋混凝土结构的抗冲击能力有利。
[Abstract]:Reinforced concrete is widely used in national defense and civil engineering (such as nuclear power plant), to study the response and damage of reinforced concrete structures under projectile impact. It is of great significance for engineering protection design and safety assessment. The main purpose of this paper is to predict the need for the reinforced concrete target plate in the different failure modes of the projectile impact. The numerical simulation of the response of reinforced concrete structures is carried out.
Based on the experimental data of the impact of the projectile impaction and the impact of the reinforced concrete target plate, the UMIST formula is modified in a unified framework. The modified UMIST formula is not only applicable to flat head projectiles but also for non flat heads (such as pointed projectiles, oval shells and hemispherical projectiles). It is not only applicable to low velocity impact but also for high speed impact. It is not only suitable for low strength concrete, but also suitable for high strength concrete. The results show that the modified formula can predict the thickness of the reinforced concrete target plate under the impact of the projectile in a very wide range of cracking, scab damage and penetration.
The deep penetration problem of a semi infinite concrete target impacted by a rigid flat projectile is studied. Through the observation of the experimental phenomenon, a "dead zone" will be produced in the front of the projectile during the penetration process. Therefore, as a first order approximation, the problem of the penetration of a flat head projectile into a semi infinite coagulant target is considered to be the penetration of a conical projectile. By using the rigid plastic incompressible medium model, by using the theory of slip line theory and the principle of virtual power, the static resistance part of the concrete medium to the flat head projectile is obtained by using the rigid plastic incompressible medium model. The penetration resistance of the concrete medium to the flat head projectile is obtained by the dynamic resistance caused by the velocity effect. The resistance of the condensing medium is replaced by the motion equation of the projectile, and the penetration depth formula of the projectile is obtained. The penetration depth of the projectile predicted by this formula is in good agreement with the experimental data.
In this paper, the problem of the shear strength of reinforced concrete slab is studied. Because the failure surface in the formula of the existing RC plate is not consistent with the actual failure surface and the formula itself is not dimensionless, the applicable scope of the existing formula is limited. In this paper, a prediction of reinforcement coagulation is proposed. The empirical equation of the shear strength of the soil plate under the action of the pressure of the cylindrical punch under the impact of the punching shear is taken into account. The effect of the amount of steel, the spacing of the steel bar and the ratio of the thickness to the thickness is considered. By comparing with the experimental data and comparing with the existing empirical formulas, it can be seen that the empirical formula presented in this paper has some advantages.
Based on the experimental observation and the difference between the thickness of the plate and the diameter of the projectile, the cracking and failure of the reinforced concrete target plate under the low velocity impact of a flat projectile is studied. In the case of the low velocity impact of the flat head projectile, two types of failure modes will occur, that is, the direct thickness direction cracking and the failure of the projectile; the projectile is not intruded. In this paper, the two stage failure semi analysis model of the penetration and thickness direction cracking of the projectile impact concrete target plate is first established. Secondly, the penetration resistance of the projectile penetrating the concrete target plate and the reinforcement coagulation with dynamic enhancement factor are obtained by using the analysis model of the flat head projectile penetrating the concrete target. The resistance to the punching shear capacity of the target plate is obtained by the two failure modes of the reinforced concrete target plate (failure mode diagram). The model prediction is in good agreement with the experimental data.
A numerical simulation of the response and damage of reinforced concrete structures under projectile impact is carried out by using the new dynamic constitutive relation of concrete in our laboratory. The dynamic constitutive model of the concrete is taken into consideration of pressure correlation, strain rate effect, Lode angle effect, shear damage effect and tensile damage effect, through the impact of steel on the flat head projectile. The numerical simulation of the response of the reinforced concrete target plate is very close to the experimental observation, and the results are satisfactory. At the same time, the concrete dynamic constitutive model is used to simulate the thickness of the reinforced concrete slab, the distance and size of the steel bar, and the factors are obtained for the target plate of the reinforced concrete. The effect of the failure mode of a flat head projectile under impact. The reinforced concrete structure in the nuclear power plant is mainly a cylindrical shell and a spherical shell. The damage of the shell structure under the impact of a flat projectile is preliminarily studied by numerical simulation. The results show the impact of the existence of the ratio of curvature to the reinforced concrete structure. Ability is good.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU375;TM623

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