SIMPLIFIED CALCULATION METHOD FOR HIGH TEMPERATURE FLEXURAL BEARING CAPACITY OF RC BEAMS STRENGTHENED WITH CFRP UNDER FIRE

Abstract

Abstract: The calculation of bearing capacity of CFRP reinforced members under fire condition is the key to the fire resistance design. The temperature field of one-surface and three-surface exposed to fire of insulated CFRP reinforced RC beams under standard fire was analyzed by the finite element numerical simulation. Considering the influence of main factors (thickness and thermal conductivity of fireproof coating), a simplified formula for calculating the surface and internal temperatures of strengthened members is proposed. The accuracy of the simplified formula was well verified by comparing with the experimental data. By combining the analysis method of ultimate state of concrete beams section and the high temperature degradation model of material and interface properties, a simplified calculation method was established to calculate the high temperature bearing capacity of CFRP reinforced RC beams at different times under ISO 834 standard fire conditions. Compared the load capacity with the load effect, the reasonable thickness of fire protection materials could be determined. The research results can be helpful to establish the fire protection design method of CFRP reinforced RC beams, or to judge whether the existing CFRP reinforced beams can meet the requirement of fire resistance. The theoretical means and methods for fire resistance design and safety appraisal of CFRP reinforced structures were proposed.

Key words: concrete structure, FRP strengthening, loading capacity, fire, calculation method, composites

CLC Number:

TB332

HAO Jian-wen, DONG Kun, JIANG Ji-tong, HU Ke-xu. SIMPLIFIED CALCULATION METHOD FOR HIGH TEMPERATURE FLEXURAL BEARING CAPACITY OF RC BEAMS STRENGTHENED WITH CFRP UNDER FIRE[J]. Composites Science and Engineering, 2020, 0(6): 10-17.

References

[1] Feng P, Ye L, Bao R. A large-span woven web suspension roof system made of high-strength FRP[J]. Iabse Symposium Report, 2000, 88(3): 43-48.
[2] Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures: ACI440[S]. American Concrete Institute, 2004.
[3] 叶列平, 冯鹏. FRP在工程结构中的应用与发展[J]. 土木工程学报, 2006, 39(3): 24-36.
[4] 陆锦标, 顾祥林. 既有建筑结构检测鉴定规范的现状和发展趋势[J]. 住宅科技, 2008(6): 37-43.
[5] Halliwell S. In-service performance of glass reinforced plastic composites in buildings[J]. Proceedings of the Institution of Civil Engineers-Structures and Buildings, 2004, 157(1): 99-104.
[6] 纤维增强复合材料建设工程应用技术规范: GB 50608—2016[S]. 北京: 中国计划出版社, 2016.
[7] Abbasi A, Hogg P J. A model for predicting the properties of the constituents of a glass fibre rebar reinforced concrete beam at elevated temperatures simulating a fire test[J]. Composites Part B: Engineering, 2005, 36(5): 384-393.
[8] 董坤, 胡克旭, 王炜浩, 等. CFRP加固混凝土梁不同防火材料保护设计方法[J]. 防灾减灾工程学报, 2015, 35(1): 6-10.
[9] Gao W Y, Dai J G, TengJ G. Simple method for predicting temperatures in reinforced concrete beams exposed to a standard fire[J]. Advances in Structural Engineering, 2014,17: 573-589.
[10] 刘汾涛, 魏德敏. 碳纤维布加固混凝土梁的温度场实用计算方法[J]. 工程抗震与加固改造, 2009, 31(6): 93-98.
[11] 吴波, 万志军, 王帆. 碳纤维布抗弯加固钢筋混凝土梁的耐火极限分析[J]. 工程抗震与加固改造, 2008(2): 101-108.
[12] 刘汾涛, 吴波, 魏德敏. 碳纤维布加固混凝土梁的高温抗弯承载力——影响因素及衰减关系[J]. 自然灾害学报, 2009, 18(6): 21-28.
[13] Kodur V K R, Yu B. Rational approach for evaluating fire resistance of FRP-strengthened concrete beams[J]. J Comp Cons, 2016, 20(6): 4016041.
[14] Kodur V K R, Yu B. A simplified approach for predicting temperature in reinforced concrete members exposed to standard fire[J]. Fire Safety Journal, 2013, 56(1): 39-51.
[15] Chowdhury E, Bisby L, Green M, et al. Heat transfer and structural response modelling of FRP confined rectangular concrete columns in fire[J]. Construction & Building Materials, 2012, 32(7): 77-89.
[16] Kodur V K, Ahemd A, Dwaikat M. Modeling the fire performance of FRP-strengthened reinforced concrete beams: state-of-the-art[J]. Composites &Polycon, 2009, 1-20.
[17] Gao W Y, Dai J G, Teng J G. Fire resistance design of un-protected FRP-strengthened RC beams[J]. Materials and Structures, 2016,49(12): 5357-5371.
[18] 高皖扬, 胡克旭, 陆洲导. CFRP加固钢筋混凝土梁耐火性能试验研究[J]. 土木工程学报, 2010, 43(3): 15-23.
[19] 胡克旭, 侯梦君, 高皖扬, 等. 不同保护措施下CFRP加固混凝土梁耐火性能试验[J]. 哈尔滨工业大学学报, 2018, 50(6): 138-144.
[20] 建筑设计防火规范: GB50016—2014[S]. 北京: 中国计划出版社, 2014.
[21] Design of Concrete Structures, Part 1-2: General rules-Structural Fire Design: EN 1992-1-2, Eurocode 2[S]. European Committee for Standardization, 2004.
[22] Dong K, Hu K. Development of bond strength model for CFRP-to-concrete joints at high temperatures[J]. Composites Part B: Engineering, 2016, 95: 264-271.
[23] 胡克旭, 董坤, 杨耀武. 温度作用对碳纤维—混凝土界面黏结性能的影响[J]. 同济大学学报(自然科学版), 2016, 44(6): 845-852.
[24] Dai J G, Ueda T, Sato Y. Development of the nonlinear bond stress-slip model of fiber reinforced plastics sheet-concrete interfaces with a simple method[J]. Journal of Composites for Construction, 2005, 9(1): 52-62.