碳纤维加固混凝土梁的试验研究
摘要
碳纤维加固是一项有效的混凝土结构修复加固技术。本文的第一部分基于断裂力学与梁的基本理论，对碳纤维加固混凝土梁的粘结胶层以及粘结界面的剪应力分布进行了理论分析，得出了其理论解析解；讨论了碳纤维板的粘结长度、粘结厚度和粘结胶层的抗剪模量对界面剪应力分布的影响。本文的理论分析结果可以表明：增加碳纤维板的粘结长度可以缓解碳纤维板端部界面上的剪应力集中，改善混凝土梁结构的加固效果；增大碳纤维板的粘结厚度可以增大界面上的剪应力，改善混凝土梁上载荷向碳纤维板的传递效果，有利于充分发挥碳纤维布的潜能；如果粘结胶层的抗剪模量过大会加剧剪应力的集中，从而对碳纤维加固的效果不利。
本文的主体部分对碳纤维加固带初裂纹的混凝土梁进行了试验研究。试验考察了碳纤维布粘结长度以及粘贴方式对加固后混凝土梁极限承载力的影响。从试验的结果来看，碳纤维的粘结长度增加对混凝土梁的加固效果的影响十分明显：当碳纤维粘结长度为100mm时，混凝土加固梁的极限承载力一般为未加固混凝土梁的1.81-2.27倍；而当碳纤维粘结长度为200mm和300mm时，混凝土加固梁的极限承载力则分别为未加固梁的3.35-3.97倍和3.61-5.76倍。相比之下，改善碳纤维板的粘结方式，即采用粘结双层碳纤维布和在单层碳纤维布的基础上粘结U形包头的影响要小一些：采用双层碳纤维布加固比单层碳纤维布加固时的极限承载力提高了8.5%-11.3%；采用包头形式加固比单层碳纤维布加固的极限承载力提高了4.7%-18%。另外试验还对裂纹深度对加固效果的影响进行了分析，结果表明：不论采用什么样的粘结方式加固，裂纹深度越大，则加固的效果就越明显。
另一方面，本文还根据试验中观察到的现象和混凝土梁的最终破坏形式，对碳纤维加固混凝土梁的破坏模式和裂纹的发展过程进行了研究。在试验中，碳纤维加固混凝土梁的破坏模式有三种：剪切破坏I、剪切破坏II和分层破坏。剪切破坏I是由于在碳纤维板端部混凝土的剪应力峰值超过其剪切强度产生剪切裂纹，剪切裂纹沿着与混凝土梁轴线成约45度角的方向扩展最终导致混凝土梁破坏。本试验中它一般发生在碳纤维板粘结长度为200mm的情况下。剪切破坏II则是在剪切裂纹发展的过程中与扩展后的初裂纹相贯穿，从而导致混凝土梁破坏。此种破坏在碳纤维板粘结长度为100mm时发生的可能性很大。在分层破坏时初裂纹随载荷一直发展，碳纤维布逐渐脱落，最后初裂纹失稳发展导致试件破坏。
Epoxy-bonding a carbon-fiber composite plate to the tension face of concrete beam is an effective technique for repair and retrofit of concrete beams. In the first part of this paper, based on the fracture mechanics and the theory of beam, a theoretic model is proposed to analyze the shear stress in the adhesive between carbon-fiber composite and concrete. And then the closure-form solution for the shear stress distribution is drawn. At different value of the main parameters that govern the shear stress distribution such as CFP adhesive length, CFP thickness and the anti-shear modulus of adhesive, the distribution of shear stress is studied. This leads to an easy understanding of the influence of some geometrical and material parameters. The following principles are proved: Increasing CFP adhesive length will release the concentrating of shear stress near the cutoff point, this will lead to the increment of loading-bear capacity of concrete beams; Increasing the thickness of CFP will improve the transition of load from concrete beam to CFP, this is useful to exert the potential of CFP; In creasing the anti-shear modulus of adhesive will result enhance the concentrating of shear stress, this is harmful to the effect of CFP reinforced concrete beams.
The main body of this paper focuses on experimental research of CFP reinforced concrete beams. The experiment highlights the effect of CFP length and the adhesive mode of CFP on the loading-bear capacity of CFP reinforced beams. From the results, it is obvious that when the CFP adhesive length increases, the loading-bear capacity increase too. When the CFP length is 10mm, the loading-bear capacity is 1.81-2.27 times as much as the value of non-reinforced beam; And when the CFP length increase to 200mm and 350mm, the loading-bear capacity increase to 3.35-3.97 times and 3.61-5.76 times as much as the value of non-reinforced beam. By contrast, the effect of improving the adhesive mode of CFP, that is to say, epoxy-bonding double carbon-fiber composite plates or epoxy-bonding U shape CFP anchorage is less notable. The loading-bear capacity of double CFP reinforced concrete beams is 8.5-11.3 percent higher than that of the single CFP reinforced concrete beams; the loading-bear capacity of epoxy-boding U shape CFP anchorage reinforced beams is 4.7-18 percent higher than that of the single CFP reinforced beams. Additionally, the experiment also studies the effect of crack depth on reinforced concrete beams. The result indicates: whatever adhesive mode is taken, it is true that the deeper the crack is, the more notable the effect is.
What's more, this paper studied the failure mode of CFP reinforced concrete beams and the process of the crack's extending based on the phenomenon that were observed in the experiment and the ultimate failure form of samples. There are three kind of failure mode of the CFP reinforced concrete beams: shear failure mode I, shear failure mode II and debonding failure mode. The cause of shear failure mode I is that the shear stress peak exceed the shear strength of concrete, so the shear crack formed and extended along the direction of angle of 45o to the longitude of the concrete beam. The extending of this shear crack leads to failure of samples. This mode appears in the case that the CFP length is 200mm. if during the shear crack's extending it run through the original crack which is locate on the middle of the beam, so from then on the original crack will extend quickly and this will lead to the failure of the samples. This is the failure mode II. It always appears when the CFP length is 100mm. The debonding failure mode is that during the loading process, the original crack extends and leads to the debonding of the CFP and the failure of the samples. This mode appears in the case that the CFP is 350mm.
本文的主体部分对碳纤维加固带初裂纹的混凝土梁进行了试验研究。试验考察了碳纤维布粘结长度以及粘贴方式对加固后混凝土梁极限承载力的影响。从试验的结果来看，碳纤维的粘结长度增加对混凝土梁的加固效果的影响十分明显：当碳纤维粘结长度为100mm时，混凝土加固梁的极限承载力一般为未加固混凝土梁的1.81-2.27倍；而当碳纤维粘结长度为200mm和300mm时，混凝土加固梁的极限承载力则分别为未加固梁的3.35-3.97倍和3.61-5.76倍。相比之下，改善碳纤维板的粘结方式，即采用粘结双层碳纤维布和在单层碳纤维布的基础上粘结U形包头的影响要小一些：采用双层碳纤维布加固比单层碳纤维布加固时的极限承载力提高了8.5%-11.3%；采用包头形式加固比单层碳纤维布加固的极限承载力提高了4.7%-18%。另外试验还对裂纹深度对加固效果的影响进行了分析，结果表明：不论采用什么样的粘结方式加固，裂纹深度越大，则加固的效果就越明显。
另一方面，本文还根据试验中观察到的现象和混凝土梁的最终破坏形式，对碳纤维加固混凝土梁的破坏模式和裂纹的发展过程进行了研究。在试验中，碳纤维加固混凝土梁的破坏模式有三种：剪切破坏I、剪切破坏II和分层破坏。剪切破坏I是由于在碳纤维板端部混凝土的剪应力峰值超过其剪切强度产生剪切裂纹，剪切裂纹沿着与混凝土梁轴线成约45度角的方向扩展最终导致混凝土梁破坏。本试验中它一般发生在碳纤维板粘结长度为200mm的情况下。剪切破坏II则是在剪切裂纹发展的过程中与扩展后的初裂纹相贯穿，从而导致混凝土梁破坏。此种破坏在碳纤维板粘结长度为100mm时发生的可能性很大。在分层破坏时初裂纹随载荷一直发展，碳纤维布逐渐脱落，最后初裂纹失稳发展导致试件破坏。
Epoxy-bonding a carbon-fiber composite plate to the tension face of concrete beam is an effective technique for repair and retrofit of concrete beams. In the first part of this paper, based on the fracture mechanics and the theory of beam, a theoretic model is proposed to analyze the shear stress in the adhesive between carbon-fiber composite and concrete. And then the closure-form solution for the shear stress distribution is drawn. At different value of the main parameters that govern the shear stress distribution such as CFP adhesive length, CFP thickness and the anti-shear modulus of adhesive, the distribution of shear stress is studied. This leads to an easy understanding of the influence of some geometrical and material parameters. The following principles are proved: Increasing CFP adhesive length will release the concentrating of shear stress near the cutoff point, this will lead to the increment of loading-bear capacity of concrete beams; Increasing the thickness of CFP will improve the transition of load from concrete beam to CFP, this is useful to exert the potential of CFP; In creasing the anti-shear modulus of adhesive will result enhance the concentrating of shear stress, this is harmful to the effect of CFP reinforced concrete beams.
The main body of this paper focuses on experimental research of CFP reinforced concrete beams. The experiment highlights the effect of CFP length and the adhesive mode of CFP on the loading-bear capacity of CFP reinforced beams. From the results, it is obvious that when the CFP adhesive length increases, the loading-bear capacity increase too. When the CFP length is 10mm, the loading-bear capacity is 1.81-2.27 times as much as the value of non-reinforced beam; And when the CFP length increase to 200mm and 350mm, the loading-bear capacity increase to 3.35-3.97 times and 3.61-5.76 times as much as the value of non-reinforced beam. By contrast, the effect of improving the adhesive mode of CFP, that is to say, epoxy-bonding double carbon-fiber composite plates or epoxy-bonding U shape CFP anchorage is less notable. The loading-bear capacity of double CFP reinforced concrete beams is 8.5-11.3 percent higher than that of the single CFP reinforced concrete beams; the loading-bear capacity of epoxy-boding U shape CFP anchorage reinforced beams is 4.7-18 percent higher than that of the single CFP reinforced beams. Additionally, the experiment also studies the effect of crack depth on reinforced concrete beams. The result indicates: whatever adhesive mode is taken, it is true that the deeper the crack is, the more notable the effect is.
What's more, this paper studied the failure mode of CFP reinforced concrete beams and the process of the crack's extending based on the phenomenon that were observed in the experiment and the ultimate failure form of samples. There are three kind of failure mode of the CFP reinforced concrete beams: shear failure mode I, shear failure mode II and debonding failure mode. The cause of shear failure mode I is that the shear stress peak exceed the shear strength of concrete, so the shear crack formed and extended along the direction of angle of 45o to the longitude of the concrete beam. The extending of this shear crack leads to failure of samples. This mode appears in the case that the CFP length is 200mm. if during the shear crack's extending it run through the original crack which is locate on the middle of the beam, so from then on the original crack will extend quickly and this will lead to the failure of the samples. This is the failure mode II. It always appears when the CFP length is 100mm. The debonding failure mode is that during the loading process, the original crack extends and leads to the debonding of the CFP and the failure of the samples. This mode appears in the case that the CFP is 350mm.
引文
[1] 赵彤 谢剑著. 碳纤维布补强混凝土结构新技术. 天津大学出版社. 2001年1月
[2] 蒙云. 桥梁加固与改造. 重庆大学出版社. 1989年
[3] W. Jansze . Strengthening of Reinforced Concert Members in Bending by External Bonded Steel Plate. Delft University Press. 1997
[4] Hamid Saadatmanesh and Mohammad R. Ehsani. Experimental Study of Concert Girders Retrofitted with Epoxy-Bonded Composite Laminates. Journal of Structural Engineering ASCE. V.117 No.11. November1991.
[5] 贾永升. 粘钢补强技术在125吨浇钢行车断裂混凝土梁上的应用 . 重庆市2002年结构加固会议论文. 2002年
[6] 贺曼罗. 建筑结构胶粘剂的发展与应用 . 重庆市2002年结构加固会议论文. 2002年
[7]王禹阶. 玻璃钢技术问答. 中国玻璃钢工业协会. 1997年
[8]黄培彦等. 碳纤维增强混凝土缺口梁承载力实验研究. 试验力学.16卷第3期. 2001年9月
[9] Y.Murakami. Stress intensity factors handbook Vol.2[M]. Tokyo: pergamon Press. 1987
[10] Raithby, K.D., External strengthening of concrete bridge with bonded steel plates, Suppl. report 612. Transport and Road Research Laboratory, 1975
[11]Macdonald,M.D., and Calder, A.J.J., Bonded steel plating for strengthening concrete structure, International Journal of adhesion and adhesive (Guilford), V.2, No.2, Apr.1982, pp119-127
[12]Jones, R., Swamy, R.N., Bloxham, J., and Boundbalah, Composite behavior of concrete beams with epoxy bondedexternal reinforcement, international journal of cement composites and lightweight concrete (Harlow), V.2, No.2, May 1980,pp91-107
[13] Meier, U., Bridge repair with high performance composite materials, Mater. Technik, Vol.15, pp.125-128, 1987
[14] Michael J.C , William W.F etc, Bond and force transfer of composite material plates bonded to concrete , ACI structure journal ,march/april , 1998
[15]Kasumassa Nakaba, Toshiyuki kanakubo ect. Bond behavior between fiber-reinforced polymer laminates and concrete, ACI structural journal, May-June 2001.
[16] Amir M.malek, Hamid Saadatmanesh ect. Prediction of failure load of R/C beams strengthened with FRP platedue to stress concentration at the plate end, ACI structural journal, March-April 1998.
[17] Hamid Saadatmanesh ect. RC beams strengthened with FRP plate, part 1: experimental study , Journal of structural engineering, V.117, No.11,Nov. 1991
[18]An. Wei, Hamid Saadatmanesh ect., RC beams strengthened with FRP plate, part 2: Analysis
and Parametric Study, Journal of structural engineering, V.117, No.11,Nov. 1991
[19]Veronica, Sierra-Ruiz , Jean-Francois Destrebecq , etc. Simplified Models for Transfer Length in Concrete Structures Reinforced with Composite material
[20]黄培彦等. 纤维薄板增强混凝土缺口试件破坏模式研究 非均匀材料的变形与破坏学术研讨会 重庆 2001年
[21]Dussek,Ian J., and King, G.E.M., Development of Structural by means of Epoxy-Resin-Bonded Eternal Reinforcement, Transportation Research Record No.785, Transportation Research board,Washington,D.C.,1980,pp.21-24.
[22]Joshon,R.P.,and Swamy, R.N., Plate Seperation and Anchorage of Reinforced Concrete Beams strengthened by Epoxy-bonded steel plate, Structural Engineer(London),V.66,No 5,Mar.1988,pp.85-94
[23]Saadatmanesh,H.,and Ehsani,M.R.,fiber composite plates can strengthen beams, Concrete International:Design & construction, Vol 2,No.3,Mar.1990,pp.65-71
[24]吴刚等. 外贴CFRP加固混凝土结构的抗弯设计方法. 建筑结构. 2000. 30（7）：7-10
[25]吴家龙. 弹性力学. 同济大学出版社. 1987年8月
[26]王荣国等. 复合材料概论. 哈尔滨工业大学出版社. 1999年8月
[27]李立寒，张南鹭. 道路建筑材料. 同济大学出版社. 1999年7月
[28]吴文清，郑晓燕. 外贴纤维增强塑料板. 混凝土与水泥制品.1998年第2期. 4月.
[29]吴刚，安琳等. 碳纤维布用于钢筋混凝土梁抗弯加固的试验研究.建筑结构. 2000. 30(7).
[30]张培源等. 新编材料力学. 重庆大学工程力学系. 1998年10月
[31]牛松山等. 用混杂纤维改善混凝土强度及韧性的试验研究. 非均匀材料的变形与破坏学术研讨会. 重庆. 2001年
[32]Marco Arduini,Angelo Di Tommaso , Antonio Nanni. Brittle failure in FRP plate and sheet bonded beams.ACI Structural Journal,July-August 1997.
[33]Calder, G.O., and Calder A.J.J., Exposure Test on Externally Reinforced Concrete beam-First Two years, Supplementary Report No.529, Transport and Road Research Laboratory, Crowthorne, 1979,27 pp
[34]Johnson, R.P., and Tait, C.J., Strength in Combined Bending and Tension of Concrete Beams with Externally Bonded Reinforcing Plates, Building and Environment, V.16, No.4,1981, pp287-299
[35]Omar Chaallal, and Mohsen Shshawy, Performance of Fiber-reinforced Polymer-Wrapped Reinforced Concrete Column under Combined Axial-Flexual Loading, ACI Structural Journal, July-August 2000, No.97-S68, pp659-668
[2] 蒙云. 桥梁加固与改造. 重庆大学出版社. 1989年
[3] W. Jansze . Strengthening of Reinforced Concert Members in Bending by External Bonded Steel Plate. Delft University Press. 1997
[4] Hamid Saadatmanesh and Mohammad R. Ehsani. Experimental Study of Concert Girders Retrofitted with Epoxy-Bonded Composite Laminates. Journal of Structural Engineering ASCE. V.117 No.11. November1991.
[5] 贾永升. 粘钢补强技术在125吨浇钢行车断裂混凝土梁上的应用 . 重庆市2002年结构加固会议论文. 2002年
[6] 贺曼罗. 建筑结构胶粘剂的发展与应用 . 重庆市2002年结构加固会议论文. 2002年
[7]王禹阶. 玻璃钢技术问答. 中国玻璃钢工业协会. 1997年
[8]黄培彦等. 碳纤维增强混凝土缺口梁承载力实验研究. 试验力学.16卷第3期. 2001年9月
[9] Y.Murakami. Stress intensity factors handbook Vol.2[M]. Tokyo: pergamon Press. 1987
[10] Raithby, K.D., External strengthening of concrete bridge with bonded steel plates, Suppl. report 612. Transport and Road Research Laboratory, 1975
[11]Macdonald,M.D., and Calder, A.J.J., Bonded steel plating for strengthening concrete structure, International Journal of adhesion and adhesive (Guilford), V.2, No.2, Apr.1982, pp119-127
[12]Jones, R., Swamy, R.N., Bloxham, J., and Boundbalah, Composite behavior of concrete beams with epoxy bondedexternal reinforcement, international journal of cement composites and lightweight concrete (Harlow), V.2, No.2, May 1980,pp91-107
[13] Meier, U., Bridge repair with high performance composite materials, Mater. Technik, Vol.15, pp.125-128, 1987
[14] Michael J.C , William W.F etc, Bond and force transfer of composite material plates bonded to concrete , ACI structure journal ,march/april , 1998
[15]Kasumassa Nakaba, Toshiyuki kanakubo ect. Bond behavior between fiber-reinforced polymer laminates and concrete, ACI structural journal, May-June 2001.
[16] Amir M.malek, Hamid Saadatmanesh ect. Prediction of failure load of R/C beams strengthened with FRP platedue to stress concentration at the plate end, ACI structural journal, March-April 1998.
[17] Hamid Saadatmanesh ect. RC beams strengthened with FRP plate, part 1: experimental study , Journal of structural engineering, V.117, No.11,Nov. 1991
[18]An. Wei, Hamid Saadatmanesh ect., RC beams strengthened with FRP plate, part 2: Analysis
and Parametric Study, Journal of structural engineering, V.117, No.11,Nov. 1991
[19]Veronica, Sierra-Ruiz , Jean-Francois Destrebecq , etc. Simplified Models for Transfer Length in Concrete Structures Reinforced with Composite material
[20]黄培彦等. 纤维薄板增强混凝土缺口试件破坏模式研究 非均匀材料的变形与破坏学术研讨会 重庆 2001年
[21]Dussek,Ian J., and King, G.E.M., Development of Structural by means of Epoxy-Resin-Bonded Eternal Reinforcement, Transportation Research Record No.785, Transportation Research board,Washington,D.C.,1980,pp.21-24.
[22]Joshon,R.P.,and Swamy, R.N., Plate Seperation and Anchorage of Reinforced Concrete Beams strengthened by Epoxy-bonded steel plate, Structural Engineer(London),V.66,No 5,Mar.1988,pp.85-94
[23]Saadatmanesh,H.,and Ehsani,M.R.,fiber composite plates can strengthen beams, Concrete International:Design & construction, Vol 2,No.3,Mar.1990,pp.65-71
[24]吴刚等. 外贴CFRP加固混凝土结构的抗弯设计方法. 建筑结构. 2000. 30（7）：7-10
[25]吴家龙. 弹性力学. 同济大学出版社. 1987年8月
[26]王荣国等. 复合材料概论. 哈尔滨工业大学出版社. 1999年8月
[27]李立寒，张南鹭. 道路建筑材料. 同济大学出版社. 1999年7月
[28]吴文清，郑晓燕. 外贴纤维增强塑料板. 混凝土与水泥制品.1998年第2期. 4月.
[29]吴刚，安琳等. 碳纤维布用于钢筋混凝土梁抗弯加固的试验研究.建筑结构. 2000. 30(7).
[30]张培源等. 新编材料力学. 重庆大学工程力学系. 1998年10月
[31]牛松山等. 用混杂纤维改善混凝土强度及韧性的试验研究. 非均匀材料的变形与破坏学术研讨会. 重庆. 2001年
[32]Marco Arduini,Angelo Di Tommaso , Antonio Nanni. Brittle failure in FRP plate and sheet bonded beams.ACI Structural Journal,July-August 1997.
[33]Calder, G.O., and Calder A.J.J., Exposure Test on Externally Reinforced Concrete beam-First Two years, Supplementary Report No.529, Transport and Road Research Laboratory, Crowthorne, 1979,27 pp
[34]Johnson, R.P., and Tait, C.J., Strength in Combined Bending and Tension of Concrete Beams with Externally Bonded Reinforcing Plates, Building and Environment, V.16, No.4,1981, pp287-299
[35]Omar Chaallal, and Mohsen Shshawy, Performance of Fiber-reinforced Polymer-Wrapped Reinforced Concrete Column under Combined Axial-Flexual Loading, ACI Structural Journal, July-August 2000, No.97-S68, pp659-668