[Objective] In this paper, we proposed a new method to enhance the flexural performance of reinforced concrete (RC) beams, improve construction efficiency, and reduce the wet work at the reinforcement site. This method involves reinforcing RC beams with prestressed carbon textile reinforced concrete (P-TRC) plates connected to the RC beams using nails. [Methods] The proposal is underpinned by a four-point bending test conducted on P-TRC plates RC beams. The test results led to the development of a calculation formula for the height of the compression zone in beams reinforced with P-TCR plates in different modes, such as cracking, yielding, tensile failure, and compression failure. [Results] These calculations consider the strain hysteresis of the carbon fiber fabric, which is caused by nail bending. Furthermore, the formula to calculate the bending bearing capacity of the reinforced beam's tension zone under different failure modes was obtained from moment balance. This paper also introduces the stress mechanism of the nail as a reinforcing layer. When traditional layer paving methods are used to reinforce the RC beam, the adhesion between the reinforcing layer and the RC beam relies heavily on chemical adhesion, the frictional resistance between the old and new concrete, and the mechanical occlusion force of the joint surface. However, quantifying the shear performance index of the reinforcing layer proves challenging, and it is difficult to guarantee the failure mode of the reinforcing layer. If peeling or detachment occurs in the reinforcement beam, it could easily lead to a failure in the reinforcement effect. Conversely, when a nail is used for reinforcement, the nail bears the shear capacity of the reinforcement layer. The shear bearing capacity of the nail gradually tends to decrease from the pure bending section of the reinforced beam to the bending and shear section of the same. Under the action of the concentrated force couple formed by the load and the support reaction, the nail in the bending shear section undergoes normal tension. This normal tensile force is generated by the frictional force between the nail and the concrete. By controlling the number, size, and shear strength of nails, the shear performance index of the reinforcing layer can be quantified. Consequently, the P-TRC plate only experiences a failure mode of tensile failure. Additionally, this paper proposes a calculation formula for the midspan deflection of the beam reinforced with a P-TRC plate during normal use, considering the elongation of the reinforcement at the bottom of the beam. Moreover, through experimental procedures, a theoretical calculation formula for the maximum midspan deflection of the beam reinforced with P-TRC plates is proposed. [Conclusions] To validate the calculation formula for the bending bearing capacity and deflection of the reinforced beam, the flexural capacity and mid-span deflection curve of the normal cross-section of the beam reinforced with P-TRC plates under six different working conditions was calculated and compared with the test value. The results show that the theoretical and experimental values of the beam reinforced with P-TRC plates are consistent. This suggests that the presented calculation method holds significant value as a reference for guiding actual engineering design.
[1] BRÜCKNER A, ORTLEPP R, CURBACH M. Textile reinforced concrete for strengthening in bending and shear[J]. Materials and Structures, 2006, 39(8):741-748.
[2] DU Y X, ZHANG M M, ZHOU F, et al. Experimental study on basalt textile reinforced concrete under uniaxial tensile loading[J]. Construction and Building Materials, 2017, 138:88-100.
[3] 荀勇,孙伟, REINHARDT H W,等.短纤维和织物增强混凝土薄板试验研究[J].土木工程学报, 2005, 38(11):58-63. XUN Y, SUN W, REINHARDT H W, et al. An experimental study on short fiber and textile reinforced concrete thin-slabs[J]. China Civil Engineering Journal, 2005, 38(11):58-63.(in Chinese)
[4] 刘扬,彭晖,尚守平.预应力CFRP加固钢筋混凝土受弯构件的抗力概率模型研究[J].工程力学, 2012, 29(7):107-116. LIU Y, PENG H, SHANG S P. Probability model of the flexural resistance of reinforced concrete beams strengthened with prestressed CFRP plates[J]. Engineering Mechanics, 2012, 29(7):107-116.(in Chinese)
[5] ESCRIG C, GIL L, BERNAT-MASO E. Experimental comparison of reinforced concrete beams strengthened against bending with different types of cementitious-matrix composite materials[J]. Construction and Building Materials, 2017, 137:317-329.
[6] 杜运兴,邵喜诚,周芬.预应力CTRC板加固持载混凝土梁的抗弯性能研究[J].铁道科学与工程学报, 2020, 17(1):189-197. DU Y X, SHAO X C, ZHOU F. Flexural behavior of RC beams repaired with prestressed CTRC plates under sustaining loads[J]. Journal of Railway Science and Engineering, 2020, 17(1):189-197.(in Chinese)
[7] 薛伟辰,曾磊,谭园.预应力CFRP板加固混凝土梁设计理论研究[J].建筑结构学报, 2008, 29(4):127-133. XUE W C, ZENG L, TAN Y. Studies on design theories of concrete beams strengthened with Prestressed CFRP plates[J]. Journal of Building Structures, 2008, 29(4):127-133.(in Chinese)
[8] 周云,王廷彦,张军伟. CFRP加固钢筋混凝土短梁抗弯刚度计算方法[J].土木工程学报, 2020, 53(11):9-20, 35. ZHOU Y, WANG T Y, ZHANG J W. Calculation method on flexural stiffness of reinforced concrete short beam strengthened by CFRP[J]. China Civil Engineering Journal, 2020, 53(11):9-20, 35.(in Chinese)
[9] 陈爱玖,韩小燕,杨粉,等.预应力碳纤维布加固钢筋再生混凝土梁受弯承载力研究[J].土木工程学报, 2018, 51(11):104-112. CHEN A J, HAN X Y, YANG F, et al. Study on flexural capacity of reinforced recycled concrete beams strengthened with prestressed CFRP sheets[J]. China Civil Engineering Journal, 2018, 51(11):104-112.(in Chinese)
[10] 江胜华,侯建国,何英明.考虑预应力损失的CFRP布加固钢筋混凝土梁正常使用极限状态可靠度研究[J].土木工程学报, 2015, 48(11):36-43. JIANG S H, HOU J G, HE Y M. Reliability research of serviceability limit states for RC beams strengthened with prestressed CFRP sheets considering prestress loss[J]. China Civil Engineering Journal, 2015, 48(11):36-43.(in Chinese)
[11] ESMAEELI E, BARROS J A O. Flexural strengthening of RC beams using Hybrid Composite Plate (HCP):Experimental and analytical study[J]. Composites Part B:Engineering, 2015, 79:604-620.
[12] 荀勇,支正东,张勤.织物增强混凝土薄板加固钢筋混凝土梁受弯性能试验研究[J].建筑结构学报, 2010, 31(3):70-76. XUN Y, ZHI Z D, ZHANG Q. Experimental research on flexural behavior of reinforced concrete beams strengthened with textile reinforced concrete sheets[J]. Journal of Building Structures, 2010, 31(3):70-76.(in Chinese)
[13] 周芬,陈小晔,杜运兴,等.预拉纤维复合板增强梁抗弯性能研究[J].华中科技大学学报(自然科学版), 2019, 47(1):60-66. ZHOU F, CHEN X Y, DU Y X, et al. Study on flexural behavior of beams strengthened with prestressed fabric reinforced cementitious plates[J]. Journal of Huazhong University of Science and Technology (Natural Science Edition), 2019, 47(1):60-66.(in Chinese)
[14] 余琼,张燕语.预应力碳纤维布加固钢筋混凝土梁挠度研究[J].结构工程师, 2011, 27(1):139-143. YU Q, ZHANG Y Y. Study on deflection of RC beams Strengthened with prestressed CFRP[J]. Structural Engineers, 2011, 27(1):139-143.(in Chinese)
[15] 徐世烺,尹世平,蔡新华.纤维编织网增强混凝土加固钢筋混凝土梁受弯性能研究[J].土木工程学报, 2011, 44(4):23-34. XU S L, YIN S P, CAI X H. Investigation on the flexural behavior of reinforced concrete beam strengthened with textile-reinforced concrete[J]. China Civil Engineering Journal, 2011, 44(4):23-34.(in Chinese)
[16] 周芬,徐文,杜运兴. TRC板增强钢筋混凝土梁的抗弯性能[J].中南大学学报(自然科学版), 2018, 49(1):183-191. ZHOU F, XU W, DU Y X. Flexural behavior of RC beams strengthened with TRC plates[J]. Journal of Central South University (Science and Technology), 2018, 49(1):183-191.(in Chinese)
[17] 毛宇欣,黄俊豪,钱永久.考虑二次受力的CFRP布加固RC梁短期挠度研究[J].工程抗震与加固改造, 2023, 45(4):130-137, 155. MAO Y X, HUANG J H, QIAN Y J. Study on short-term deflection of RC beams strengthened by CFRP sheet considering secondary load[J]. Earthquake Resistant Engineering and Retrofitting, 2023, 45(4):130-137, 155.(in Chinese)
[18] 吴子林,杜运兴,周芬.预制TRC板与混凝土界面性能研究[J].新型建筑材料, 2021, 48(8):74-79. WU Z L, DU Y X, ZHOU F. Interface performance between precast TRC slab and concrete member[J]. New Building Materials, 2021, 48(8):74-79.(in Chinese)
[19] 中华人民共和国住房和城乡建设部.混凝土结构设计规范:GB 50010-2010[S].北京:中国建筑工业出版社, 2011. Ministry of Housing and Urban-Rural Development of the People's Republic of China. Code for design of concrete structures:GB 50010-2010[S]. Beijing:China Architecture&Building Press, 2011.(in Chinese)
[20] 张勤.织物增强混凝土(TRC)加固RC梁正截面抗弯性能试验研究[D].镇江:江苏大学, 2009. ZHANG Q. Experimental study on flexural behavior of reinforced concrete beams strengthened with textile reinforced concrete[D]. Zhenjiang:Jiangsu University, 2009.(in Chinese)
[21] YANG D S, PARK S K, NEALE K W. Flexural behaviour of reinforced concrete beams strengthened with prestressed carbon composites[J]. Composite Structures, 2009, 88(4):497-508.
