Zapris Adamantis G, Kytinou Violetta K, Chalioris Constantin E
Laboratory of Reinforced Concrete and Seismic Design of Structures, Civil Engineering Department, School of Engineering, Democritus University of Thrace, 67100 Xanthi, Greece.
Polymers (Basel). 2024 Sep 18;16(18):2634. doi: 10.3390/polym16182634.
The fiber-reinforced polymer (FRP) strengthening of reinforced concrete (RC) elements with torsional deficiencies has not yet been extensively studied. Existing studies have primarily focused on rectangular RC beams. The few studies on L or T-shaped beams have used open-form retrofitting methods. However, premature debonding of the retrofitting from concrete surfaces often leads to detachment before achieving enhanced torsional capacity. This study introduces an innovative application of closed-form FRP retrofitting for RC T-beams against torsion. Two novel closed-form torsional upgrading methods were proposed and investigated through a comprehensive experimental program involving eight large-scale T-beams. One method employs FRP ropes embedded in transverse grooves near the surface, while the other combines U-shaped EB-FRP strips with FRP ropes. Additionally, two configurations were examined replicating scenarios where the upper part of the slab is accessible or inaccessible. The results demonstrate that the closed-form methods improve torsional strength by 9% to 25% and twist at failure by 92% to 536% compared to unstrengthened beams, with beams retrofitting through the slab exhibiting superior performance. Step-by-step technical guidelines of the proposed methods are presented to minimize construction defects and ensure effective implementation in real RC structures.
纤维增强聚合物（FRP）对存在抗扭缺陷的钢筋混凝土（RC）构件进行加固的研究尚未广泛开展。现有研究主要集中在矩形RC梁。对L形或T形梁的少数研究采用了开放式加固方法。然而，加固材料与混凝土表面过早脱粘往往导致在达到增强的抗扭能力之前就发生脱离。本研究介绍了一种用于RC T形梁抗扭的封闭式FRP加固创新应用。通过一个涉及八根大型T形梁的综合试验计划，提出并研究了两种新型封闭式抗扭升级方法。一种方法是在靠近表面的横向凹槽中嵌入FRP绳索，另一种方法是将U形EB - FRP条带与FRP绳索相结合。此外，还研究了两种配置，以模拟平板上部可及或不可及的情况。结果表明，与未加固梁相比，封闭式方法可将抗扭强度提高9%至25%，破坏时的扭转角度提高92%至536%，通过平板进行加固的梁表现出更优异的性能。文中给出了所提方法的逐步技术指南，以尽量减少施工缺陷并确保在实际RC结构中有效实施。
