【作者】 王岳华；

【导师】 丁一宁；

【作者基本信息】 大连理工大学 ， 结构工程， 2008， 博士

【摘要】 隧道火灾具有升温剧烈、温度高的特点,严重威胁人民生命和财产的安全。对于隧道衬砌结构的耐火性能设计,一方面需要考虑高温造成的材料性能劣化,另一方面还要考虑剧烈升温导致的温度应力,衬砌的严重变形和开裂同样危害隧道的安全性。有鉴于此,本文针对纤维高性能混凝土筒体在高温冲击下的性能,结合国家自然科学基金项目:纤维混凝土/喷射混凝土在循环高温作用下的力学性能(50278013),主要包括以下内容:1、进行了纤维高性能混凝土工作性的试验研究。研制了具有较高工作性的高性能混凝土;分析了不同类型及掺量的钢纤维、聚丙烯纤维和混杂纤维对高性能混凝土振前、振后坍落流动度的影响,聚丙烯纤维和混杂纤维对高性能混凝土的工作性有显著的降低作用,但可通过少量振动加以缓解;以保证筒体浇筑的顺利完成。2、对高温前后纤维高性能混凝土的抗压强度和弹性模量进行了试验研究。PP纤维对400℃高温后抗压强度的影响较明显;高温对混凝土弹性模量的影响大于抗压强度。3、在总结普通混凝土热工性能的基础上,对高温下纤维高性能混凝土的热膨胀性能进行了试验研究。研究表明,混杂纤维可明显减小高性能混凝土的热膨胀变形,为实际工程使用混杂纤维降低混凝土结构在高温冲击下的温度应力提供了依据。给出了纤维高性能混凝土高温下自由热应变的计算式和平均热膨胀系数,可作为相应结构高温行为分析的计算参数。4、针对隧道火灾的高温冲击特点,自行设计了明火高温试验系统并改装了高温位移传感器,研制出适合进行筒体耐高温冲击性能研究的明火高温试验系统。研究了高温冲击下筒体温度场、变形的特点和变化规律:结合温度应力的有限元计算,研究了温度、变形和应力之间的关系;给出了开裂前筒外壁径向位移的简化计算式。5、分析了不同纤维对筒体高温变形及高温后筒外壁裂缝形态的影响,混杂纤维可限制筒体的高温变形,减小高温后的裂缝宽度,使高温后筒体的裂缝分布“多、细、密”,因而可提高筒体的耐高温冲击性能。6、确定高温(火灾)时混凝土构件内部的温度场是研究构件及结构高温力学行为的基础。基于试验结果,应用ANSYS软件对筒壁的瞬态温度场进行了有限元分析,同时探讨了选取不同热工参数及对流换热系数对计算结果的影响。7、以温度场分析为基础,对高温冲击下筒壁开裂前的变形和温度应力进行了有限元分析,总结了筒壁温度应力分布及其随温度的变化规律,分析了筒壁开裂时的应力状态。更多还原

【Abstract】 Tunnel fire has the character of temperature rising up rapidly and highly, which may severely damage safety of people’s lives and properties. For designing fire-resistant performance of tunnel lining, deteriorations of materials due to high temperature are needed to consider on one hand, while thermal stress due to temperature rising-up acutely should also be considered on the other hand. Safety of tunnel is also decreased by severe deformation and cracking of lining structure. For this reason, aiming at the behaviours of Fiber Reinforced High Performance Concrete (FRHPC) pipes under high temperature impact, based on the project of National Nature Science Foundation, Investigation on Bearing Capacity of Fiber Reinforced Concrete/Shotcrete under the Repeated High Temperature (No. 50278013), the following researches are presented in this thesis:1. Test on workability of FRHPC are carried out. High Performance Concrete (HPC) with high workability is developed. The influences of steel fiber, PP fiber and hybrid fiber with different type and content on the Slump-Flow of HPC before and after vibrating are analyzed. PP fiber and hybrid fiber have remarkable effects on decreasing the workability of HPC, but with slightly vibrating the effects can be mitigated. Casting pipe successfully is ensured.2. Test on compressive strength and elastic modulus of FRHPC before and after high temperature are carried out. PP fiber has clear effect on the compressive strength after high temperature of 400℃. The influence of high temperature on elastic modulus is greater than on compressive strength.3. Based on summarizing thermal properties of Normal Concrete (NC), test on thermal expansion property of FRHPC under high temperature are carried out. Hybrid fiber can clearly reduce the thermal expansion of HPC, which provides support for engineering practice of using hybrid fiber to decrease thermal stress of concrete structure under high temperature impact. The formulae of free thermal strain and the average thermal expansion coefficients of FRHPCs under high temperature are presented, which can be calculation parameters when analyzing high temperature behaviour of relevant structure.4. Based on the character of temperature rising-up rapidly and highly in tunnel fire, a fire-simulated high temperature test system, which is suit for researching pipe’s performance of resisting high temperature impact, is developed. Pipe’ features and changing laws of temperature and deformation under high temperature impact are investigated. Based on FE solution of thermal stress, the relationship between temperature, deformation and stress is analyzed. Simplified formula for calculating radial displacement of pipe’s outer-side layer before cracking is presented.5. The influence of different fibers on pipe’s deformation under high temperature and cracking manner after high temperature is analyzed. Hybrid fiber restricted pipe’s deformation under high temperature, reduced crack width after high temperature, also made pipe’s crack distribution "more, thin and dense" after high temperature, so can improve pipe’ s performance of resisting high temperature impact as a result.6. Analyzing temperature field inside concrete member under high temperature/fire is the precondition for investigating high-temperature mechanical bahaviour of members and structures. Based on test data, using ANSYS, FE analysis on transient temperature field of pipe is carried out, and the effects of choosing different thermal properties and convection coefficients on the solution are discussed at the same time.7. Based on temperature field analysis, FE analysis on pipe’s deformation and thermal stress before cracking under high temperature impact is carried out. Distribution and law of thermal stress changing with temperature is summarized, and stress state of pipe shell when cracking is analyzed.更多还原