Issue 46

S.Y. Jiang et alii, Frattura ed Integrità Strutturale, 46 (2018) 275-284; DOI: 10.3221/IGF-ESIS.46.25 283 According to Tab. 4, the total crack height in the sustained loading phase is affected by the total height of pre-cracks. With no pre-cracks, B-1 and B-2 have greater height of cracks during sustained loading phase. With high total pre-crack height, B-3 and B-4 have limited growth in crack height in the same phase, leading to reduced sectional stiffness and surge in long- term deflection. C ONCLUSIONS (1) The pre-cracking degree before reinforcement has little effect on the instantaneous stiffness of the reinforced beam, that is, the instantaneous beam deflection will not change much after the reinforcement. The total deflection of reinforced beam is controlled by the instantaneous deflection (including the residual deflection. The additional deflection accounts for a small proportion of the total deflection. (2) The pre-cracking degree of before strengthening will affect the additional deflection of strengthened beams, the larger the pre-cracking degree is, the smaller the long-term additional deflection of the strengthened beam is. (3) Concrete creep is the ultimate cause of deflection. The pre-cracking of concrete beam reduces the concrete viscoelasticity and releases the concrete stress, which in turn lower the concrete creep and additional deflection. (4) The degree of pre-cracking is negatively correlated with the crack development under sustained load, the decline of sectional stiffness and the magnitude of additional deflection. (5) The creep of concrete will cause the change of the long-term deflection and the cause of the long-term stiffness reduction of the strengthened beam, so the creep of the concrete is the most fundamental reason for the increase of the long-term additional deflection of the reinforced beam. ACKNOWLEDGMENTS he authors are grateful to the finical support from the Key Projects of College Outstanding Achievements Transformation (KJZH14220). R EFERENCES [1] Pan, W. (2017). Application of carbon fiber reinforcement in structural strengthening engineering, Development Guide to Building Materials, 15(8), pp. 44-46. [2] Ali, B.M., Bouiadjera, B.B., Chikh, E.B.O., Elmeguenni, M. (2017). The effect of the plastic instability on the behavior of an amorphous polymer, Mathematical Modelling of Engineering Problems, 4(1), pp. 53-58. DOI: 10.18280/mmep.040111. [3] Hong, S. (2014). Effect of Intermediate Crack Deboning on the Flexural Strength of CFRP-Strengthened RC Beams, Mechanics of Composite Materials, 50(4), pp. 523-536. DOI: 10.1007/s11029-014-9439-6. [4] Shuraim, A.B., El-Sayed, A.K., Al-Negheimish A.I. (2016). Efficiency of CFRP Strengthening in Controlling the Deflection of RC Beams in a Redundant Structural System, Journal of Composites for Construction, 20(2), 04015054. DOI: 10.1061/(ASCE)CC.1943-5614.0000604. [5] Peng, H., Zhang, J., Shang, S. (2016). Experimental study of flexural fatigue performance of reinforced concrete beams strengthened with prestressed CFRP plates, Engineering Structures, 127, pp. 62-72. DOI: 10.1016/j.engstruct.2016.08.026 [6] Plevris, N., Triantafillou, T.C. (1994). Time-Dependent Behavior of RC Members Strengthened with FRP Laminates, Journal of Structural Engineering, 120(3), pp. 1016-1042. DOI:10.1061/(ASCE)0733-9455(1994)120:3(1016). [7] Hong, S., Park, S.K. (2016). Long-term behavior of fiber-reinforced-polymer-plated concrete beams under sustained loading: Analytical and experimental study, Composite Structures, 152, pp. 140-157. DOI: 10.1016/j.compstruct.2016.05.031. [8] El-Sayed, A.K., Al-Zaid, R.A., Al-Negheimish, A.I. (2014). Long-term behavior of wide shallow RC beams strengthened with externally bonded CFRP plates, Construction & Building Materials, 51(4), pp. 473-483. DOI:10.1016/j.conbuildmat.2013.10.055. T