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In order to accurately estimate the anti-penetration capacity of yaw-inducing bursting layer with irregular barriers on surface
impacted by projectile, the theoretical model of attack angle and angular velocity for projectile impacting on irregular barrier
was achieved according to the macroscopic relation of contact force versus contact time, in which the main factors such as
the relative geometrical characteristics of projectile and irregular barrier, material property and impact velocity of projectile
influencing on yaw-inducing effectiveness were considered. On the basis of considering synthetically the influences of attack
angle, impact velocity, impact angle of projectile and uncontrolled free surface of target, the theoretical formulation of
penetration depth for bursting layer with irregular barriers on surface impacted by projectile was presented by expressing
the stress of an optional point on the nose of projectile according to the relation of stress versus velocity. The theoretical
results indicate that in the case of oblique impact embodying effect of attack angle, the penetration depth is reduced with
the increase of impact angle, attack angle or angular velocity, and penetration trajectory is also deflected obviously. The
effectiveness of angular velocity influencing on penetration depth is increased with impact velocity increasing. The theoretical
results are in good agreement with test data for low impact velocity. 相似文献
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地下洞室开挖和支护过程的应力南应变状态对隧道工程安全性评估至关重要.文章采用LS-DYNA软件的动力松弛法确定围岩和结构的初始应力和应变状态,然后对开挖、喷锚支护和衬砌支护过程进行数值模拟,分析了围岩Von-Mises应力、塑性应变、最大主应变和位移变化情况.分析表明:开挖和支护方案对围岩应力和应变状态影响较大.大跨度地下工程在开挖和支护过程中出现的塑性变形主要局限于锚杆能够达到的区域,说明喷锚支护设计方案合理;另外,在围岩中会出现一定规模的拉伸应变,主要区域集中在围岩直墙和底板的交界处,但喷射混凝土和衬砌上没有塑性应变发生,拉伸应变的数值也很小;锚杆上的轴力远小于锚杆能承受的最大拉伸轴力,开挖和支护过程结束后整个结构系统均是安全的. 相似文献
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以某典型单层多跨无梁楼盖人防结构为研究对象,根据相似条件设计了场地土和结构模型,分别采用Elcentro波和Kobe波进行水平单向或双向耦合地震动输入,进行两种不同埋深情况下砂土地基中结构地震响应的振动台模型试验研究。给出了结构加速度、应变、位移等动力响应的量测结果,分析了无梁楼盖人防结构地震破坏机理。结果表明:双向耦合输入地震荷载比水平单向输入地震荷载引起的结构动力响应大;浅埋结构与深埋结构相比各种动力响应均明显增大;由于结构中柱相对独立,其动力反应较侧墙强烈;结构中柱上下端、侧墙上下角隅处都是容易遭受地震破坏的部位;竖向地震力对结构的动力响应产生明显影响,其破坏力不容忽视。 相似文献
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