落石低速冲击混凝土板破坏效应研究

发布时间：2018-07-27 21:31

【摘要】：在西部地区,公路桥梁和房屋建筑大多依山而建,再加之西部地区处在地震带区域,地震带来的地质灾害不同程度的威胁着已建和在建工程。特别是5.12地震之后,流域沿线两侧山体出现松动,由于多种原因导致的崩塌落石情况越发频繁,山区公路、隧道棚洞、桥梁遭到撞击损坏的事故日益增多,山区落石危害的问题就越来越突出。国内外关于落石撞击桥墩的研究较多,关于桥面板的则研究较少,板类构件在低速冲击作用下有明显的整体响应,和前者有很大不同,值得深入研究。为此,本文通过室内试验、数值仿真和理论推导来研究和验证上述问题。具体内容和结论如下:(1)混凝土板低速冲击试验通过室内小尺寸混凝土板模型试验,研究在低速冲击荷载作用下,混凝土板的破坏过程、开裂形式及冲击力影响参数。试验可知:混凝土板的碰撞过程比落石撞击桥墩碰撞时间长,原因是碰撞过程包含了板的整体变形和变形恢复过程;冲击力的大小与板厚、冲击速度和混凝土强度都有一定关系,其中速度和板厚影响更大,混凝土强度对靶板破坏形态有一定影响。(2)针对低速冲击的数值模拟参数优化利用LS-Dyna建立有限元模型,模拟低速大质量体撞击混凝土板过程,结合模型试验数据优化数值模拟设置参数,使模拟结果更趋近真实情况。(3)低速冲击作用下混凝土板破坏机理研究基于室内模型试验和数值模拟的破坏效应和破坏特征,结合塑性板理论可知:混凝土板在大质量低速度冲击作用下大多出现弯曲破坏,但随着速度增大,混凝土板中心局部冲切破坏特征会愈加明显。(4)落石撞击混凝土板的冲击力计算方法推导基于在室内模型试验和数值模拟结果,在前人研究的基础上推导考虑结构整体变形的落石冲击力计算方法。该方法得到的计算结果与试验结果和有限元解均相差不大,偏差在30%以内,本文计算方法合理。
[Abstract]:In the western region, most of the highway bridges and buildings are built according to the mountains, and the western region is located in the seismic zone, the geological hazards caused by the earthquake threaten the construction of the existing construction projects to varying degrees. In particular, after the May 12 earthquake, the mountains along the river basin were loosened, and the collapse and fall of rocks due to various reasons became more and more frequent. The accidents of mountain roads, tunnels and bridges being damaged by impact were increasing day by day. The problem of falling rocks in mountain areas is becoming more and more serious. At home and abroad, there are more researches on falling stone impact pier and less on bridge deck slab. The whole response of slab members under low speed impact is obvious, which is very different from the former, so it is worthy of further study. Therefore, the above problems are studied and verified by laboratory test, numerical simulation and theoretical derivation. The main contents and conclusions are as follows: (1) the failure process, cracking form and impact force parameters of concrete slabs under low speed impact load are studied through the model tests of small size concrete slabs in laboratory. Experimental results show that the impact process of concrete slab is longer than that of stone fall impact bridge pier, because the impact process includes the whole deformation and deformation recovery process of the slab, the impact force and the thickness of the slab. There is a certain relationship between impact velocity and concrete strength, in which velocity and slab thickness have more influence, and concrete strength has certain influence on the failure pattern of target slabs. (2) the finite element model is established by using LS-Dyna to optimize the numerical simulation parameters of low velocity impact. In order to simulate the impact process of low speed and large mass body against concrete slab, the parameters of numerical simulation are optimized with model test data. The simulation results are more realistic. (3) the failure mechanism of concrete slabs under low speed impact is studied based on the failure effect and failure characteristics of indoor model test and numerical simulation. Combined with the theory of plastic slabs, it can be seen that most of the concrete slabs under the action of large mass and low velocity impact appear bending failure, but with the increase of velocity, The characteristics of local punching failure in the center of concrete slabs will become more obvious. (4) the calculation method of impact force of rockfall impact concrete slabs is derived based on the results of indoor model tests and numerical simulation. On the basis of previous studies, the calculation method of rock drop impact force considering the whole deformation of structure is deduced. The calculated results obtained by this method are not different from the experimental results and the finite element solutions, and the deviation is less than 30%. The calculation method in this paper is reasonable.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U446

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