高温（火灾）下预应力混凝土板温度场及力学性能的数值分析
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摘要
防治火灾是长期而艰巨的任务。预应力钢筋混凝土结构是现代工程结构中一种新的结构形式,所以关于其温度场的研究也越来越有意义。在试验室中模拟难度较大,人力、财力消耗较多,危险性也比较高。本文针对预应力钢筋混凝土板在标准升温曲线作用下的温度-应力场进行有限元数值模拟研究。主要工作如下:
(1)对国内外关于钢筋及混凝土热力学参数随温度变化的规律进行了归纳总结;以热传导基本方程为依据,详细介绍了高温条件下截面温度场的有限元方程推导过程,为温度场的数值模拟打下了理论基础。
(2)通过前面数据确定了对流换热系数、辐射换热发射率系数、混凝土导热系数及比热的取值。然后进行预应力钢筋混凝土板的温度场分析和应力应变的数值模拟。按标准升温曲线模拟温度,通过应用ANSYS软件实现对预应力混凝土单向简支板的温度变化全过程分析。绘制了板截面上距受火面不同高度的升温曲线。再将有限元模拟值与试验结果比较,分析两者误差原因,及有限元模拟值的合理性。
(3)火灾中,建筑物的构件除了要承受正常使用的荷载外,还承受温度应力。由于边界条件的限制,温度应力造成预应力混凝土构件发生变形,再内部产生较大内力。本文先通过数值计算方法介绍了板温度应力和挠曲微分方程。然后用有限元软件模拟温度场中预应力钢筋混凝土简支板的温度应力、板的变形、板的应变等。同时,分别对自定义预应力混凝土简支板在标准升温曲线下的变形进行了数值分析。经过计算可得,在正常荷载作用下预应力混凝土板的耐火性较好。
It is a long term and arduous task to prevent and control fire. As reinforced prestressed concrete structure is a new kind of modern structural styles in structure engineering , its investigation in temperature field has become more and more significant . It is not only difficult to situate the fire field in the laboratory but also in a considerable risk as well as human and financial resources consuming. This thesis aims to demonstrate finite element numerical simulation study about temperature-stress field of reinforced prestressed concrete slabs under permanent loads when it is in high-temperature conditions .The primary tasks are as follows:
(1)The laws of parameters about reinforcing steel and concrete along with temperature at home and abroad are summarized .The finite equations of section temperature field under fire are derived on the basis of the heat conduction fundamental equations in detail .The theoretical foundations of the temperature field software are laid firmly.
(2)Based on the last data, the values of convection heat transfer coefficient, radiation emissivity coefficient, thermal conductivity and specific heat of concrete are determinate by a trial and error procedure. After deriving suitable parameters,the temperature field of reinforced prestressed concrete slabs has been analyzed : in addition to that,the ultimate be bearing capacity has been calculated. By simulating the scene of a fire temperature according the ISO standard temperature elevation curve. Temperature change analysis of prestressed concrete simple slab subjected to fire is carried out by using of ANSYS software. Different temperature curves that are apart from the fire surface have been presented in this thesis. Then error analysis has been done by comparing the finite element simulation value with the experimental observed value. The rationality of the finite element simulation value has been analyzed.
(3)When the fire,besides its ability to sustain normal use loads,each component of building is also required to sustain extra temperature stress. As a result of border restrictions,the whole reinforced prestressed concrete structures will be deformed by the temperature stress in addition to that, a great internal force will be produced. In this thesis,temperature stress and differential deflection equation of the thin slab interior will be derived from numerical calculation; the finite element software has been used to simulated temperature stress and the deformation and strain of thin slab interior by the non-linear theory. Then besides, the nonlinear analyses were also done on the deflections of the prestressed concrete bonded simply supported slab respectively in ISO standard temperature rise conditions, and the results show that the prestressed concrete bonded simply supported slab has a good fire resistance under the normal design load level.
(1)对国内外关于钢筋及混凝土热力学参数随温度变化的规律进行了归纳总结;以热传导基本方程为依据,详细介绍了高温条件下截面温度场的有限元方程推导过程,为温度场的数值模拟打下了理论基础。
(2)通过前面数据确定了对流换热系数、辐射换热发射率系数、混凝土导热系数及比热的取值。然后进行预应力钢筋混凝土板的温度场分析和应力应变的数值模拟。按标准升温曲线模拟温度,通过应用ANSYS软件实现对预应力混凝土单向简支板的温度变化全过程分析。绘制了板截面上距受火面不同高度的升温曲线。再将有限元模拟值与试验结果比较,分析两者误差原因,及有限元模拟值的合理性。
(3)火灾中,建筑物的构件除了要承受正常使用的荷载外,还承受温度应力。由于边界条件的限制,温度应力造成预应力混凝土构件发生变形,再内部产生较大内力。本文先通过数值计算方法介绍了板温度应力和挠曲微分方程。然后用有限元软件模拟温度场中预应力钢筋混凝土简支板的温度应力、板的变形、板的应变等。同时,分别对自定义预应力混凝土简支板在标准升温曲线下的变形进行了数值分析。经过计算可得,在正常荷载作用下预应力混凝土板的耐火性较好。
It is a long term and arduous task to prevent and control fire. As reinforced prestressed concrete structure is a new kind of modern structural styles in structure engineering , its investigation in temperature field has become more and more significant . It is not only difficult to situate the fire field in the laboratory but also in a considerable risk as well as human and financial resources consuming. This thesis aims to demonstrate finite element numerical simulation study about temperature-stress field of reinforced prestressed concrete slabs under permanent loads when it is in high-temperature conditions .The primary tasks are as follows:
(1)The laws of parameters about reinforcing steel and concrete along with temperature at home and abroad are summarized .The finite equations of section temperature field under fire are derived on the basis of the heat conduction fundamental equations in detail .The theoretical foundations of the temperature field software are laid firmly.
(2)Based on the last data, the values of convection heat transfer coefficient, radiation emissivity coefficient, thermal conductivity and specific heat of concrete are determinate by a trial and error procedure. After deriving suitable parameters,the temperature field of reinforced prestressed concrete slabs has been analyzed : in addition to that,the ultimate be bearing capacity has been calculated. By simulating the scene of a fire temperature according the ISO standard temperature elevation curve. Temperature change analysis of prestressed concrete simple slab subjected to fire is carried out by using of ANSYS software. Different temperature curves that are apart from the fire surface have been presented in this thesis. Then error analysis has been done by comparing the finite element simulation value with the experimental observed value. The rationality of the finite element simulation value has been analyzed.
(3)When the fire,besides its ability to sustain normal use loads,each component of building is also required to sustain extra temperature stress. As a result of border restrictions,the whole reinforced prestressed concrete structures will be deformed by the temperature stress in addition to that, a great internal force will be produced. In this thesis,temperature stress and differential deflection equation of the thin slab interior will be derived from numerical calculation; the finite element software has been used to simulated temperature stress and the deformation and strain of thin slab interior by the non-linear theory. Then besides, the nonlinear analyses were also done on the deflections of the prestressed concrete bonded simply supported slab respectively in ISO standard temperature rise conditions, and the results show that the prestressed concrete bonded simply supported slab has a good fire resistance under the normal design load level.
引文
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[5]殷颖志,钢结构高强螺栓受拉及受剪连接在高温(火灾)下的性能:[硕士论文],上海;同济大学,2001
[6]胡克旭,朱伯龙,结构受火灾作用的全过程分析方法,四川建筑科学研究,1996,9(5):29~34
[7]霍然,李元洲,金旭辉等,大空间建筑内火灾烟气充填的研究,自然灾害学报,2000,9(1):88~92
[8]钟茂华,厉培德,范维澄等,大空间建筑室内火蔓延全尺寸实验设计,火灾科学,2001,10(1):16~19
[9]袁理明,范维澄,大空间建筑火灾中热烟气层发展规律的理论分析,自然灾害研究,1998,7(1):21~26
[10]苏南,林铜柱.钢筋混凝土柱的抗火性能.土木工程学报,1992,25(1):25~36
[11]范维澄.火灾科学导论.湖北科学技术出版社,武汉,1993,4
[12]时旭东,过镇海.不同保护层厚度的钢筋混凝土梁的耐火试验研究.工业建筑,1996,26(9):12~14
[13]时旭东,过镇海.不同温度工况下钢筋混凝土偏压构件受力性能的对比试验研究[J].建筑结构学报, 2001,(04)
[14]杨建平,时旭东,过镇海.两面高温下钢筋混凝土压弯构件的试验研究,建筑结构,2000,30(2):23~27
[15]李华东,时旭东,过镇海.高温下钢筋混凝土轴心受压柱的破坏特征和变形规律研究,特种结构,1997,14(1):34~37
[16]时旭东,李华东,过镇海.三面受热钢筋混凝土偏心受压柱的试验研究.福州大学学报(自然科学版)增刊,1996,24(53): 35~144
[17]时旭东,李华东,过镇海.三面受火钢筋混凝土轴心受压柱的力学性能研究.建筑结构学报,1997,18(4):13~22
[18]James P. Hurstand Gamal N. Ahmed. Validation and application of a computer model for the thermal response of concrete slabs subjected to fire[J].ACI Structural . September-October1998:480~487
[19] Zdenek R Baiant and Werapol Thonguthai. Pore pressure in heated concrete walls: theoretical prediction [J].Magazine of Concrete Research , 1979 ,31(107):67~76
[20]Harmathy TZ. Thermal Properties of Selected Masonry Unit Concrete [J]·ACI Joumal,Vol.20,No.2 Feb.1973
[21]Harada . T. Strength,Elasticity and Thermal Properties of Concrete Subjected to Elevated Temperature [C].Concrete for Nuclear Reactors,ACISP34,Detroit,1972.377~406
[22]T.T. Lie. Fire resistance of circular steel columns filled with bar-reinforced concrete [J].Journal of Structural Engineering, 1994,120(5):1489~1509
[23]过镇海,时旭东.钢筋混凝土的高温性能及其计算[M].北京:清华大学出版社,2003
[24]朱伯龙,陆洲导等.高温(火灾)下混凝土与钢筋的本构关系[J].四川建筑科学研究,1990(l),37碑3
[25]吴波,马忠诚.钢筋混凝土结构在火灾和低周反复荷载作用下的损伤分析[J].哈尔滨建筑大学学报,Vol.30,No.3,1997b,7~12
[26]徐或.火灾高温后钢筋力学性能的试验研究[D]:[硕士论文].长沙:长沙铁道学院,2000
[27]白凤领,葛保国.英国钢结构建筑火灾试验.消防产品与信息200018(4):13~22
[28] Ashton L A. The fire - resistance of prestressed concrete floors [J]. Civil Engineering and Public Works Review, 1951, 46 (545):843 ~845 ;(546) :940~943.
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