【作者】 曲树盛；

【导师】 李忠献；

【作者基本信息】 天津大学 ， 结构工程， 2012， 博士

【摘要】 近年来,针对地铁车站的恐怖爆炸事件频繁发生,由于地铁车站具有人群密集,环境封闭的特点,一旦发生意外爆炸事件,不仅会对爆源附近的人员和设备造成严重伤害,而且爆炸所产生的冲击波作用在结构构件上,会引起车站结构的剧烈振动并发生损伤破坏,甚至会导致某些关键构件的失效而引发结构的倒塌;此外,爆炸冲击波通过土体传到地面,会引起地面振动并对地面人员、建筑和设备的安全产生威胁。为了提高地铁车站的抗爆安全性,本论文系统研究了爆炸波在地铁车站内的传播过程与衰减规律,地铁车站结构在内爆炸作用下的动力响应与损伤破坏分析,以及地铁车站内爆炸作用下的地面振动响应等,主要研究工作和创新成果包括以下几个方面:(1)研究了地铁车站内爆炸波的传播过程与衰减规律。针对目前小型规则地下结构内部爆炸流场的试验与数值研究成果不适用于地铁车站等大型复杂结构,通过有限差分程序AUTODYN,建立了一种基于爆炸超压计算精度的大尺寸网格数值模型,采用Euler方法模拟了爆炸波在地铁车站内的传播过程,对作用在车站结构上的爆炸荷载特点进行了分析,得到了爆炸超压和冲量的衰减规律,给出了爆炸发生时避免人员受伤和死亡的安全距离。通过参数分析,研究了结构高度和出口距爆源距离对爆炸波传播的影响。研究表明:地铁车站内爆炸波的传播时间更长、衰减更慢,对结构的破坏作用更大;结构高度不同不仅影响爆炸波的衰减,而且会引起波形的差异;出口的泄爆作用与出口距爆源的距离有关,出口距爆源越近,其泄爆作用越明显。(2)研究了地铁车站结构在内爆炸作用下的动力响应与损伤破坏。基于非线性有限元技术,通过显式动力分析软件LS-DYNA,建立了地铁车站结构在内部爆炸荷载作用下结构动力响应和损伤破坏的数值模拟方法,对地铁车站在背包炸弹等中小型爆炸装置产生的内部爆炸作用下的结构动态响应进行了分析,得到了梁、板、柱等主要受力构件的位移和应变等动力响应,同时分析了炸药量、构件配筋率、材料应变率效应以及土-结构相互作用等因素对结构主要受力构件响应的影响,并对结构抗爆防护概念设计提出建议。研究表明:在内部爆炸作用下,地铁车站的站台板是结构中破坏最为严重的构件,临近柱和中板会产生开裂等轻微破坏;结构的动力响应随炸药量的增大而增大,随构件配筋率的增大而减小;土-结构相互作用对于距离爆源最近的梁、板、柱构件响应影响较小。(3)研究了地铁车站站台柱的抗爆性能并提出相应的优化设计方法。针对目前尚无针对地铁车站站台柱特殊爆炸环境下抗爆性能方面的研究,建立典型地铁车站站台柱抗爆性能分析模型,从截面形状选取、轴压比的选用、箍筋配筋率及其形式等方面,系统研究并提出了提高其抗爆性能的优化设计方法。研究表明:相同截面面积以及相同爆炸冲击环境下,钢筋混凝土圆柱受到的爆炸冲击能量小于方柱,且与钢筋混凝土方柱相比较,提高圆柱的箍筋配筋率会更为显著的增加其抗爆性能,因此,在地铁车站的站台柱设计时,建议采用圆柱;提高纵筋配筋率和增大箍筋直径对于提高钢筋混凝土柱的抗爆性能效果不明显,减小箍筋间距可以显著提高柱子的抗爆性能,并针对钢筋混凝土圆柱提出一种新的箍筋配筋方式,该方式可以显著提高柱子的抗爆性能;对站台柱设置安全防护距离将显著降低作用于其上的爆炸荷载,提高其抵御意外爆炸的性能,通过研究,提出了合理安全防护距离的概念,并针对典型地铁车站站台柱,给出了建议取值。(4)研究了地铁车站内爆炸引起的地面振动特性及其峰值预测方法。针对目前对地下结构内爆炸引起土中应力波的传播和地面振动的特性缺少相应的研究,以天津某典型地铁车站为例,建立了地下结构内爆炸作用下地面振动的数值模拟方法,对车站内发生意外爆炸后,应力波在周围土体内的传播过程,引起的周边地面振动的特性及其衰减规律进行了数值分析;同时针对国内典型地铁车站,研究了车站埋深、炸药量等参数对地铁车站周边地面振动的影响规律,进而提出了考虑车站埋深和比例距离变化的地铁车站周边地面典型位置的地面振动主要参数的计算公式;并对地面振动的安全性进行了评价。研究成果可用于评估地铁车站遭恐怖爆炸情况下地面周边建筑的振动安全性,也可为地铁车站抗爆设计中车站埋深的选取提供理论依据。更多还原

【Abstract】 Recently, terrorist explosion in subway station happens more frequently than ever all over the world. Subway stations are of great crowd density and enclosure surrounding. Once accidental or terrorist explosion occurs inside them, not only causes casualties and damages to facilities nearby the explosive, but also induce strong vibration and damage of the structural components or even lead to the collapse of these structures due to the blast wave. Shock wave might also spread to the ground surface through the soil, causing vibration of the ground which is also a threat to the safety of persons, buildings and facilities on the ground. In order to improve the safety performance of subway station under internal explosion, in this dissertation, three main problems in research of blast wave propagation and damage mechanism of the structure under blast loading are systematically studied. They are (1) propagation progress and attenuation law of blast wave inside subway station; (2) dynamic response and damage of a subway station structure due to internal explosion; (3) ground vibration induced by internal explosion in subway station. The primary work and achievement are as follows:(1) Propagation law and overpressure load of blast wave inside subway station are studied. The current experiments and simulation research achievement in small regular underground structures may not be suitable for the large complicated underground structures like subway stations. Therefore, a new numerical model building method with bigger grid size based on overpressure calculating precision is established using the finite difference program AUTODYN. The propagation process of blast wave inside a subway station is numerical simulated using Euler method, the propagation and attenuation law of blast wave are investigated, safe distances to avoid human casualties are determined, and effects of height of structure and distances of exit from explosive on propagation of blast wave are analyzed. The results show that the blast wave in the subway station is of a longer propagating duration, a slower attenuation, and larger damaging effects on the structure. Different heights of structures not only affect the attenuation of blast wave, but also cause the difference of waveforms. The venting effect of the exit is related to the distance of the exit from the explosive, and the closer the exit from the explosive is, the more remarkable the venting effect is.(2) Dynamic response and damage of a subway station structure due to internal explosion are studied. Based on the nonlinear dynamic analysis software LS-DYNA, a method for simulating the dynamic response and damage of a subway station structure under internal explosion is established. The responses of the structure due to internal explosions from typical small explosive devices, such as suitcase bombs, are simulated. The dynamic displacement and strain of the typical columns, beams and floors are derived for estimating the safety of the structure. Parametric studies are also carried out to investigate the influences of TNT equivalent charge weight, reinforcement ratio of concrete members and soil-structure dynamic interaction on the dynamic responses of the structural members. The results show that the platform floor is the most seriously damaged member under the internal explosion, while minor damage such as small cracks might occur in the member nearby the explosion; Dynamic response of the structure will get stronger with the increase of the TNT equivalent charge weight, and weaker with the increase of reinforcement ratio; The soil-structure dynamic interaction cannot be considered since it has little effect on the dynamic response of the members near the explosion.(3) Blast resistance performance and optimization design of platform column for subway station are studied. Currently, there is no relative research on the blast resistance of platform column under its special explosion scenario available in the literature. In this dissertation, systematic researches are carried out, regarding to the selection of cross section, axial compression ratio, reinforcement form and ratio of stirrups, to propose optimization design methods for improving the blast resistance performance of typical subway station platform columns. The results show that, under the same explosion scenario and column section area, the circular RC column suffers less blast energy than the square one. And by increasing the stirrups ratio, blast resistance capability of circular column can be more significantly improved than the square one. Therefore, a circular cross section is suggested in blast-resistant design of subway station platform column. Reducing the stirrup spacing could significantly improve the blast resistant capability of the platform column, while increasing the diameter of the stirrups or the ratio of longitudinal reinforcement has little effect. Further, a new stirrup arrangement method for circular RC column is proposed to enhance its blast resistant capability. A safety protection distance can obviously reduce the blast pressure on the platform columns and further increase its blast resistance performance. Thus, a conception of reasonable safety protection distance for typical subway station platform columns is proposed with suggested values.(4) Ground vibration induced by internal explosion in subway station is studied. There is no relative research on stress propagation and ground vibration caused by internal explosion in underground structures available in the literature. A case study of typical subway station in Tianjin is carried out to analysis the responses of surrounding soil induced by internal explosion, including the propagation of shock wave in the soil, characteristics of ground vibration and its attenuation law. For typical subway station in China, parametric studies are carried out to investigate the influences of explosive weight and structure buried depth on ground vibration surrounding the subway station. Further, a series of formulas concerning scaled distance and structure buried depth are given to calculate the main parameters of ground vibration at typical positions surrounding the subway station. The results of the research can be used both to estimate the vibration safety of buildings surrounding the subway station under terrorist bombing attack, and to provide theoretical basis for the determination of structure buried depth in blast-resistant design of subway stations.更多还原