火灾下混凝土空心板温度场及损伤规律研究
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摘要
为分析火灾下混凝土空心板温度场分布变化,研究其结构受火损伤规律,从服役多年的空心板桥上截取长2.6 m的梁段,按ISO 834标准规定的升温曲线对其进行180 min的明火高温试验,通过预埋温度传感器实测获得空心板梁段温度场随受火作用时间的分布变化规律。在此基础上,结合统计得到的混凝土热工参数代表值、火灾试验升温加热过程和空心板实际受火热边界条件,对梁段的温度场进行有限元数值仿真分析,并将温度场理论计算结果与实测结果进行比较,分析温度场计算偏差的主要原因,探讨温度场有限元模型参数合理取值。采用300℃、500℃和800℃等温线法分别计算火灾下空心板的截面缩减系数。基于最小二乘法拟合得到空心板截面缩减系数与受火作用时间关系,对其火灾下截面损伤进行多项式量化。研究结果表明:空心板内部在试验前期升温速度较快,后期趋于平缓;同一时刻下,空心板内部温度沿梁高方向非线性递减,且梯度逐渐降低;空心板温度场有限元数值仿真结果与实测结果接近;所提出的热工参数代表值合理;空心板截面高度对其受火损伤范围影响不大;火灾下混凝土空心板截面缩减系数随受火时间呈二次抛物线递减,并随梁高递增。该研究成果可用于类似桥梁火灾下的温度场仿真分析和损伤状况评估。
An attempt was made to analyze the internal temperature field and determine the damage pattern in hollow-core concrete slabs(HCSs) exposed to fire. A 2.6 m long beam segment was removed from an HCS bridge that had been in service for many years, and a 180 min high temperature fire test of the HCS was carried out according to the International Organization for Standardization ISO 834 Standard Curve. The change pattern of the temperature fields of the beam segment with the fire exposure time was obtained by embedded temperature sensors. Based on this, combined with the representative values of the thermal parameters of concrete, the heating process, and the thermal boundary condition of the HCS, the temperature field of the HCS was analyzed by finite-element numerical simulation. The theoretical calculation results of the temperature field were compared with the measured results. The main reasons for the deviation between the calculation results and the experiment ones of temperature field were analyzed, and optimal values of the parameters of the finite-element model of the temperature field were determined. The section reduction coefficient of the hollow slab under fire was calculated using a 500 ℃ isotherm method and a 300 ℃ and 800 ℃ isotherm method. The relationship between the reduction coefficient of the HCS and the fire exposure time was fitted by the least-squares method, and the variation in damage to the cross section under fire was quantified by polynomials. The results show that the temperature inside the HCS increases relatively rapidly during the early stage of the test and gradually during the later stage. The temperature inside the HCS decreases nonlinearly in the beam height direction, and the temperature gradient gradually decreases. The finite-element numerical simulation results for the temperature field inside the HCS are similar to the measurement results. The representative values for the thermal parameters proposed in this study are reasonable. The height of a cross section of the HCS has an insignificant effect on the extent of damage at the cross section. The reduction coefficients of a cross section of the HCS exposed to fire decrease exponentially with the fire exposure time and increase with the beam height. The results of this study can be used in numerical simulations of the temperature fields in similar bridges exposed to fire as well as in the assessment of their damage.
An attempt was made to analyze the internal temperature field and determine the damage pattern in hollow-core concrete slabs(HCSs) exposed to fire. A 2.6 m long beam segment was removed from an HCS bridge that had been in service for many years, and a 180 min high temperature fire test of the HCS was carried out according to the International Organization for Standardization ISO 834 Standard Curve. The change pattern of the temperature fields of the beam segment with the fire exposure time was obtained by embedded temperature sensors. Based on this, combined with the representative values of the thermal parameters of concrete, the heating process, and the thermal boundary condition of the HCS, the temperature field of the HCS was analyzed by finite-element numerical simulation. The theoretical calculation results of the temperature field were compared with the measured results. The main reasons for the deviation between the calculation results and the experiment ones of temperature field were analyzed, and optimal values of the parameters of the finite-element model of the temperature field were determined. The section reduction coefficient of the hollow slab under fire was calculated using a 500 ℃ isotherm method and a 300 ℃ and 800 ℃ isotherm method. The relationship between the reduction coefficient of the HCS and the fire exposure time was fitted by the least-squares method, and the variation in damage to the cross section under fire was quantified by polynomials. The results show that the temperature inside the HCS increases relatively rapidly during the early stage of the test and gradually during the later stage. The temperature inside the HCS decreases nonlinearly in the beam height direction, and the temperature gradient gradually decreases. The finite-element numerical simulation results for the temperature field inside the HCS are similar to the measurement results. The representative values for the thermal parameters proposed in this study are reasonable. The height of a cross section of the HCS has an insignificant effect on the extent of damage at the cross section. The reduction coefficients of a cross section of the HCS exposed to fire decrease exponentially with the fire exposure time and increase with the beam height. The results of this study can be used in numerical simulations of the temperature fields in similar bridges exposed to fire as well as in the assessment of their damage.
引文
[1] 《中国公路学报》编辑部.中国桥梁工程学术研究综述·2014[J].中国公路学报,2014,27(5):1-96. Editorial Department of China Journal of Highway and Transport. Review on China's Bridge Engineering Research: 2014[J]. China Journal of Highway and Transport, 2014, 27 (5): 1-96.
[2] GARLOCK M, PAYA-ZAFORTEZA I, KODUR V, et al. Fire Hazard in Bridges: Review, Assessment and Repair Strategies [J].Engineering Structures, 2012, 35 (1): 89-98.
[3] 张岗,朱美春,贺拴海,等.火灾下预应力混凝土T形截面梁破坏模式研究[J].中国公路学报,2017,30(2):77-85. ZhANG Gang, ZHU Mei-chun, HE Shuan-hai, et al. Failure Model Analysis of Pre-stressed Concrete T Girder Exposed to Fire [J]. China Journal of Highway and Transport, 2017, 30 (2): 77-85.
[4] 陈映贞,许肇峰,王勇平,等.高温(火灾)作用后混凝土残余强度统计分析[J].混凝土与水泥制品,2016,16(9):1-5. CHEN Ying-zhen, XU Zhao-feng, WANG Yong-ping, et al. Statistical Analysis on Residual Strength of Concrete After Fire [J]. Journal of Concrete and Cement Products, 2016, 16 (9): 1-5.
[5] GB 9978.1—2008,建筑结构耐火试验方法[S]. GB 9978.1—2008, Fire Resistance Tests-element of Building Construction [S].
[6] 屈立军,史可贞.钢筋混凝土矩形梁的当量耐火时间[J].火灾科学,2009,18(3):168-174. QU Li-jun, SHI Ke-zhen.T-equivalent Used to Assess the Fire Resistance of RC Rectangular Beam [J]. Journal of Fire Safety Science, 2009, 18 (3): 168-174.
[7] 许清风,韩重庆,李向民,等.不同持荷水平下预应力混凝土空心板耐火极限试验研究[J].建筑结构学报,2013,34(3):20-27. XU Qing-feng, HAN Chong-qing, LI Xiang-min, et al. Experimental Research on Exposed to Fire Endurance of PC Hollow-core Slab Under Different Load Levels [J]. Journal of Building Structures, 2013, 34 (3): 20-27.
[8] SHAKYA A M, KODUR V K R. Response of Precast Prestressed Concrete Hollow Core Slabs Under Fire Conditions [J]. Journal of Engineering Structures, 2015, 87: 126-138.
[9] 刘其伟,夏凌,王成明,等.预应力混凝土空心板梁火灾中行为特点的试验研究[J].公路交通科技,2017,34(1):67-75. LIU Qi-wei, XIA Ling, WANG Cheng-ming, et al. Experimental Study of Behavior Characteristics of PC Hollow Slab Beam Exposed to Fire [J]. Journal of Highway and Transportation Research and Development, 2017, 34 (1): 67-75.
[10] 刘其伟,王成明,罗文林,等.预应力空心板梁火灾仿真分析与评估[J].公路,2014(1):35-43. LIU Qi-wei, WANG Cheng-ming, LUO Wen-lin, et al. Simulation Analysis and Evaluation of Pre-stressed Hollow Slab Girders Subjected to Fire Disaster [J]. Highway, 2014 (1): 35-43.
[11] GUO Zhen-hai, SHI Xu-dong. Experiment and Calculation of Reinforced Concrete at Elevated Temperature [M]. Beijing: Tsinghua University Press, 2011.
[12] 俞博,叶见署,温天宇,等.火灾下混凝土空心板的温度场[J].东南大学学报:自然科学版,2009,39(3):536-540. YU Bo, YE Jian-shu, WEN Tian-yu, et al. Temperature Field in Concept Hollow-slab Exposed to Fire [J]. Journal of Southeast University: Natural Science Edition, 2009, 39 (3): 536-540.
[13] DD ENV 1992-1-2: 1996, Design of Concrete Structures—Part-1-2: General Rules Structural Fire Design [S].
[14] 陆洲导.钢筋混凝土梁对火灾反应的研究[D].上海: 同济大学,1989. LU Zhou-dao, Experimental Study on Fire Response of Simple Supported Reinforced Concrete Beams [D]. Shanghai: Tongji University, 1989.
[15] LIE T T, IRWIN R J. Fire Resistance of Rectangular Steel Columns Filled with Bar-reinforced Concrete [J].Journal of Structural Engineering, 1995, 121 (5): 797-805.
[16] 路春森,屈立军,薛武平,等,建筑结构耐火设计[M].北京:中国建材工业出版社,1995. LU Chun-sen, QU Li-jun, XUE Wu-ping, et al. Building Structural fire Design [M]. Beijing: China Building Material Press, 1995.
[17] 李引擎,马道贞,徐坚,等,建筑结构防火设计计算与构造处理[M].北京: 中国建筑工业出版社,1991. LI Yin-qing, MA Dao-zhen, XU Jian, et al. Research on Fire-endurance Characteristics of Building Materials [M]. Beijing: China Architecture & Building Press, 1991.
[18] BS EN 1992-1-2: 2004, Eurocode 2: Design of Concrete Structures — Part-1-2: General Rules—Structural Fire Design [S].
[19] 陈礼刚,胡文福,辛庆德,等.火灾下钢筋混凝土板温度场分布[J].火灾科学,2004,13(4): 241-245. CHEN Li-gang, HU Wen-fu, XIN Qing-de, et al. The Temperature Distribution of the Reinforced Concrete Slabs Under Fire [J]. Journal of Fire Safe Science, 2004, 13 (4): 241-245.
[20] DBJ/T 15-81—2011,建筑混凝土结构耐火设计技术规程[S]. DBJ/T 15-81—2011, Code for Fire Resistance Design of Concrete Structure in Building [S].
[21] 吴波.火灾后钢筋混凝土结构的力学性能[M].北京:科学出版社,2003. WU Bo. The Mechanical Properties of Reinforced Concrete Structures After Fire [M]. Beijing: Science Press, 2003.
[22] 时旭东.过镇海.钢筋混凝土结构的温度场[J].工程力学,1996,13(1):35-43. SHI Xu-dong, GUO Zhen-hai. Analysis of the Temperature Field of Reinforced Concrete Structure [J]. Journal of Engineering Mechanics, 1996, 13 (1): 35-43.
[23] BS EN 1991-1-2: 2002, Eurocode 1: Actions on Structures — Part 1-2: General Actions — Actions on Structures Exposed to Fire [S].
[24] 陈振龙,韩重庆,许清风,等.底面受火预应力混凝土空心板耐火性能的有限元分析[J].防灾减灾工程学报,2016,36(3):478-485. CHEN Zhen-long, HAN Chong-qing, XU Qing-feng, et al. Finite Element Analysis of PC Hollow-core Slab Exposed to Fire [J]. Journal of Disaster Prevention and Mitigation Engineering, 2016, 36 (3): 478-485.
[25] 刘桂荣,宋玉普.火灾下钢筋混凝土剪力墙温度场分析[J].混凝土,2010(1):4-6. LIU Gui-rong, SONG Yu-pu. Temperature Field of Reinforced Concrete Shear Walls Exposed to Fire [J]. Concrete, 2010 (1): 4-6.
[2] GARLOCK M, PAYA-ZAFORTEZA I, KODUR V, et al. Fire Hazard in Bridges: Review, Assessment and Repair Strategies [J].Engineering Structures, 2012, 35 (1): 89-98.
[3] 张岗,朱美春,贺拴海,等.火灾下预应力混凝土T形截面梁破坏模式研究[J].中国公路学报,2017,30(2):77-85. ZhANG Gang, ZHU Mei-chun, HE Shuan-hai, et al. Failure Model Analysis of Pre-stressed Concrete T Girder Exposed to Fire [J]. China Journal of Highway and Transport, 2017, 30 (2): 77-85.
[4] 陈映贞,许肇峰,王勇平,等.高温(火灾)作用后混凝土残余强度统计分析[J].混凝土与水泥制品,2016,16(9):1-5. CHEN Ying-zhen, XU Zhao-feng, WANG Yong-ping, et al. Statistical Analysis on Residual Strength of Concrete After Fire [J]. Journal of Concrete and Cement Products, 2016, 16 (9): 1-5.
[5] GB 9978.1—2008,建筑结构耐火试验方法[S]. GB 9978.1—2008, Fire Resistance Tests-element of Building Construction [S].
[6] 屈立军,史可贞.钢筋混凝土矩形梁的当量耐火时间[J].火灾科学,2009,18(3):168-174. QU Li-jun, SHI Ke-zhen.T-equivalent Used to Assess the Fire Resistance of RC Rectangular Beam [J]. Journal of Fire Safety Science, 2009, 18 (3): 168-174.
[7] 许清风,韩重庆,李向民,等.不同持荷水平下预应力混凝土空心板耐火极限试验研究[J].建筑结构学报,2013,34(3):20-27. XU Qing-feng, HAN Chong-qing, LI Xiang-min, et al. Experimental Research on Exposed to Fire Endurance of PC Hollow-core Slab Under Different Load Levels [J]. Journal of Building Structures, 2013, 34 (3): 20-27.
[8] SHAKYA A M, KODUR V K R. Response of Precast Prestressed Concrete Hollow Core Slabs Under Fire Conditions [J]. Journal of Engineering Structures, 2015, 87: 126-138.
[9] 刘其伟,夏凌,王成明,等.预应力混凝土空心板梁火灾中行为特点的试验研究[J].公路交通科技,2017,34(1):67-75. LIU Qi-wei, XIA Ling, WANG Cheng-ming, et al. Experimental Study of Behavior Characteristics of PC Hollow Slab Beam Exposed to Fire [J]. Journal of Highway and Transportation Research and Development, 2017, 34 (1): 67-75.
[10] 刘其伟,王成明,罗文林,等.预应力空心板梁火灾仿真分析与评估[J].公路,2014(1):35-43. LIU Qi-wei, WANG Cheng-ming, LUO Wen-lin, et al. Simulation Analysis and Evaluation of Pre-stressed Hollow Slab Girders Subjected to Fire Disaster [J]. Highway, 2014 (1): 35-43.
[11] GUO Zhen-hai, SHI Xu-dong. Experiment and Calculation of Reinforced Concrete at Elevated Temperature [M]. Beijing: Tsinghua University Press, 2011.
[12] 俞博,叶见署,温天宇,等.火灾下混凝土空心板的温度场[J].东南大学学报:自然科学版,2009,39(3):536-540. YU Bo, YE Jian-shu, WEN Tian-yu, et al. Temperature Field in Concept Hollow-slab Exposed to Fire [J]. Journal of Southeast University: Natural Science Edition, 2009, 39 (3): 536-540.
[13] DD ENV 1992-1-2: 1996, Design of Concrete Structures—Part-1-2: General Rules Structural Fire Design [S].
[14] 陆洲导.钢筋混凝土梁对火灾反应的研究[D].上海: 同济大学,1989. LU Zhou-dao, Experimental Study on Fire Response of Simple Supported Reinforced Concrete Beams [D]. Shanghai: Tongji University, 1989.
[15] LIE T T, IRWIN R J. Fire Resistance of Rectangular Steel Columns Filled with Bar-reinforced Concrete [J].Journal of Structural Engineering, 1995, 121 (5): 797-805.
[16] 路春森,屈立军,薛武平,等,建筑结构耐火设计[M].北京:中国建材工业出版社,1995. LU Chun-sen, QU Li-jun, XUE Wu-ping, et al. Building Structural fire Design [M]. Beijing: China Building Material Press, 1995.
[17] 李引擎,马道贞,徐坚,等,建筑结构防火设计计算与构造处理[M].北京: 中国建筑工业出版社,1991. LI Yin-qing, MA Dao-zhen, XU Jian, et al. Research on Fire-endurance Characteristics of Building Materials [M]. Beijing: China Architecture & Building Press, 1991.
[18] BS EN 1992-1-2: 2004, Eurocode 2: Design of Concrete Structures — Part-1-2: General Rules—Structural Fire Design [S].
[19] 陈礼刚,胡文福,辛庆德,等.火灾下钢筋混凝土板温度场分布[J].火灾科学,2004,13(4): 241-245. CHEN Li-gang, HU Wen-fu, XIN Qing-de, et al. The Temperature Distribution of the Reinforced Concrete Slabs Under Fire [J]. Journal of Fire Safe Science, 2004, 13 (4): 241-245.
[20] DBJ/T 15-81—2011,建筑混凝土结构耐火设计技术规程[S]. DBJ/T 15-81—2011, Code for Fire Resistance Design of Concrete Structure in Building [S].
[21] 吴波.火灾后钢筋混凝土结构的力学性能[M].北京:科学出版社,2003. WU Bo. The Mechanical Properties of Reinforced Concrete Structures After Fire [M]. Beijing: Science Press, 2003.
[22] 时旭东.过镇海.钢筋混凝土结构的温度场[J].工程力学,1996,13(1):35-43. SHI Xu-dong, GUO Zhen-hai. Analysis of the Temperature Field of Reinforced Concrete Structure [J]. Journal of Engineering Mechanics, 1996, 13 (1): 35-43.
[23] BS EN 1991-1-2: 2002, Eurocode 1: Actions on Structures — Part 1-2: General Actions — Actions on Structures Exposed to Fire [S].
[24] 陈振龙,韩重庆,许清风,等.底面受火预应力混凝土空心板耐火性能的有限元分析[J].防灾减灾工程学报,2016,36(3):478-485. CHEN Zhen-long, HAN Chong-qing, XU Qing-feng, et al. Finite Element Analysis of PC Hollow-core Slab Exposed to Fire [J]. Journal of Disaster Prevention and Mitigation Engineering, 2016, 36 (3): 478-485.
[25] 刘桂荣,宋玉普.火灾下钢筋混凝土剪力墙温度场分析[J].混凝土,2010(1):4-6. LIU Gui-rong, SONG Yu-pu. Temperature Field of Reinforced Concrete Shear Walls Exposed to Fire [J]. Concrete, 2010 (1): 4-6.