【作者】 刘超；

【导师】 胡志坚；

【作者基本信息】 武汉理工大学 ， 道路与铁道工程， 2012， 硕士

【摘要】 随着公路桥梁建设的不断发展,战争和偶然因素引发的桥梁爆炸事故越来越频繁。桥梁结构在爆炸冲击荷载作用下的动力响应与损伤破坏研究变得日趋重要。尽管国内外学者对钢筋混凝土结构抗爆做了很多研究,但现阶段关于预应力混凝土结构抗爆研究几乎是空白。而随着预应力技术的发展,预应力混凝土结构在土木工程中的应用日益广泛,故而开展预应力混凝土桥梁爆炸荷载作用效应研究是十分必要的。本文针对炸药爆炸冲击波的传播规律和混凝土梁在爆炸荷载作用下的动力响应进行数值模拟研究,主要进行了以下几个方面的工作：1、详细分析爆炸冲击波的产生原理及其传播与反射规律,并推导了爆炸产物与其周围介质作用过程中的质量、动量和能量守恒三大定律公式,最终导出了爆炸总方程组。2、分析爆炸荷载重要特性参数。采用非线性显式动力有限元分析软件AUTODYN模拟计算了爆炸冲击波超压峰值和正压作用时间,发现网格尺寸效应对数值模拟结果影响较大；同时将模拟结果同经验公式值进行对比,归纳出合理描述冲击波超压峰值与比例距离关系的表达式。3、基于简化单自由度体系分析方法,将爆炸荷载简化为线性下降的三角形荷载,计算分析单片混凝土梁的固有频率、自振周期、静力位移及最大动力位移等,并通过薄板弯曲理论对桥面板结构进行理论推导与结构特性分析。4、研究爆炸荷载作用下钢筋混凝土梁的动力响应和破坏模式。通过改变比例距离、设置防护构件、配筋率、配箍率以及断面形式等参数,数值模拟梁体上方爆炸和下方爆炸,分析普通钢筋混凝土梁的抗爆性能。指出不同参数的变化会影响钢筋混凝土梁的破坏模式。5、根据钢筋混凝土梁爆炸模拟相关结论,建立预应力混凝土梁爆炸模型。通过改变比例距离、设置防护构件等参数,模拟梁体上方爆炸和下方爆炸,并将其响应和破坏模式同相应钢筋混凝土梁比较,得出在上方爆炸时预应力钢筋的作用效应并不理想,预应力混凝土梁的抗爆性能不佳；下方爆炸时预应力钢筋抗冲击作用效应比普通钢筋明显,其抗爆性能比钢筋混凝土梁强。本文的研究结果可为预测桥梁结构受爆炸荷载作用后的变形与破坏模式提供参考,同时为桥梁结构的抗爆设计及综合防护提供理论依据,具有重要的工程意义。更多还原

【Abstract】 With the development of highway and bridge construction,explosion accidents of bridge caused by the warfare and accidents become more and more frequent.The dynamic response and damage study of bridge structure under blast loads become more and more important day by day.Domestic and foreign scholars have do much anti-detonation research about reinforced concrete structure,but the anti-detonation research about prestressed concrete structure at the present is almost black.Moreover with the development of prestressing technique,prestressed concrete structures have been widely used in the field of civil engineering. Therefore,it is quiet necessary to corry out the study of blast loads action effect for prestressed concrete bridges. Aiming at the propagation rules of explosive shock wave and the dynamic response of concrete beams under blast loads,the following work has been done by numerical simulation in this paper:1.The production principle of explosive shock wave and its propagation and reflection law are analysed detailedly.Besides,the mass,momentum and energy conservation three important laws in the effect process between explosion production and medium are inferred,and the explosion total equations have been derived ultimately.2.The important characteristic parameters of blast loads have been analysed. Nonlinear explicit dynamic finite element analysis software AUTODYN has been used to simulate the peak overpressure and positive time of explosive shock wave in the air.The mesh size will affect numerical simulation results;At the same time,the simulation results have been compared with experiential formula value,and a reasonable expression which is useful to descrip the relationship between overpressure peak of shock wave and scale distance has been summed.3.The inherent frequency,natural vibration,static displacement and maximum dynamic displacement of monolithic concrete beam have been calculated by simplifying blast loads to linear declined triangular loads,which is based on simplified single degree of freedom system analytical method.Meanwhile.theoretical derivation and structural characteristic analysis of bridge deck structure have been done through the small bending theory of thin plate.4.The dynamic response and failure modes of reinforced concrete beams under blast loads have been researched.The upper and lower explosion of beams have simulated to analyse anti-detonation perfomance of reinforced concrete beams by changing parameters of scale distance,setting protective components,reinforcement ratio,stirrup ratio and section types.And pointed out that the changes of different parameters will affect the failure modes of reinforced concrete beams.5.According to explosion simulation related conclusions of reinforced concrete beam,the prestressed concrete beam models have been established. The upper and lower explosion of beams have simulated by changing parameters of scale distance and setting protective components,and compared its reponse and failure models with relevant reinforced concrete beams.It is concluded that action effect of prestressed concrete beams is unsatisfactory about upper explosion,and anti-detonation perfomance of prestressed concrete beams is poor.Meanwhile,the impact action effect of prestressed concrete beams is more obvious than reinforced concrete beams,and its anti-detonation perfomance is stronger than reinforced concrete beams.These research results can provide reference for predicting the deformation and damage mode of bridge structures under blast loads,meanwhile,it can provide theoretical basis for antiknock design and comprehensive protection of bridge structure更多还原