Michael Antonis, Hamilton H R
Department of Civil Engineering, School of Engineering, Frederick University, Nicosia 1036, Cyprus.
Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL 32611, USA.
Materials (Basel). 2021 Sep 8;14(18):5163. doi: 10.3390/ma14185163.
Concrete members are typically designed so that flexural failure initiates with steel yielding and ends with concrete crushing in compression in order to take advantage of the yielding property of steel that allows for large deformations prior to any fracture of the material. On the other hand, if a large percentage of steel or linear elastic non-yielding reinforcement (i.e., FRP composite) is used, the member flexural failure typically initiates and ends with concrete crushing in compression. These members are known as compression-controlled members and typically exhibit brittle behavior. This study proposes a new approach in improving the flexural behavior of over-reinforced members through concrete confinement using carbon fiber reinforced polymer (CFRP) grid tubes in the compression zone. The concept was experimentally tested using rectangular beams. Beam 1 (control beam) had no grid reinforcement and beam 2 (tube beam) had two 152 mm grid tubes embedded in its compression zone. Experimental results indicate improvement in the ductility of the tube beam compared to the control beam of approximately 20-30% depending on the criteria used. Considering the low amount and mechanical properties of the CFRP grid, the improvement is significant, which shows that the proposed approach is valid and improves the ductility of compression-controlled members.
混凝土构件的设计通常是这样的，即弯曲破坏始于钢筋屈服，并以混凝土受压破碎结束，以便利用钢材的屈服特性，这种特性允许材料在任何断裂之前产生大变形。另一方面，如果使用了很大比例的钢材或线弹性非屈服钢筋（即纤维增强复合材料），构件的弯曲破坏通常始于并结束于混凝土受压破碎。这些构件被称为受压控制构件，通常表现出脆性破坏行为。本研究提出了一种新方法，通过在受压区使用碳纤维增强聚合物（CFRP）网格管对超筋构件进行混凝土约束，来改善其弯曲性能。该概念通过矩形梁进行了试验验证。梁1（对照梁）没有网格配筋，梁2（网格管梁）在其受压区嵌入了两根152毫米的网格管。试验结果表明，与对照梁相比，网格管梁的延性提高了约20% - 30%，具体取决于所采用的标准。考虑到CFRP网格的用量少和力学性能，这种提高是显著的，这表明所提出的方法是有效的，并且改善了受压控制构件的延性。
