Doctor of Philosophy
School of Civil, Mining and Environmental Engineering
Goldston, Matthew William, Behaviour of concrete beams reinforced with GFRP bars under static & impact loading, Doctor of Philosophy thesis, School of Civil, Mining and Environmental Engineering, University of Wollongong, 2016. http://ro.uow.edu.au/theses/4846
Composite materials, including Fibre Reinforced Polymer (FRP) bars, have been gaining momentum as alternatives to traditional steel reinforcements in civil and structural engineering sectors. FRP materials are non-corrosive, making them a suitable alternative to steel reinforcement in aggressive environments, lightweight and possess high longitudinal tensile strength, which are advantageous for their use in civil infrastructure. Furthermore, since they are non-conductive, they are a suitable in medical applications that are highly sensitive to electromagnetic fields including magnetic resonance imaging (MRI) facilities.
The effects of high velocity conditions such as blast or impact loading on reinforced concrete structures reinforced with steel reinforcement have been thoroughly investigated. The structural behaviour of these RC structures including beams, columns and slabs under these types of conditions are well known through extensive research, including experimental studies and numerical modelling. However, there has been little to no attention through both analytically and experimentally, the structural response of RC beams internally reinforced with FRP bars. This is an area of concern as structures reinforced with FRP bars may be susceptible to high velocity impact during their service life. Especially in coastal areas where FRP reinforcement bars is suited to that type of environment.
The objective of this research project is to investigate the response of beams reinforced with glass fibre reinforced polymer (GFRP) bars under impact loading. Furthermore, the behaviour under static loading was also investigated. An experimental program at the University of Wollongong was conducted to achieve the required objectives. The concrete beams were manufactured and tested until failure within the laboratory. In total, twenty four small scaled GFRP RC beams were constructed and tested under both static and impact loading. The specimens had a rectangular cross section of 100 x 150 mm, with a length of 2400 mm, and were set up under simply supported conditions. The main variables were the longitudinal reinforcement ratio and concrete strength. GFRP RC beams with higher reinforcement ratio showed higher post-cracking bending stiffness and experienced flexural-critical failure under static loading. However, GFRP RC beams under impact loading, regardless of their shear capacity, experienced a ‘‘shear plug” and a dynamic punching shear failure around the impact zone. The average dynamic amplification factor was calculated as approximately 1.16, indicating higher dynamic moment capacities compared to static moment capacities.
A two-degree-of-freedom mass-spring-damper system was used to model the dynamic punching shear behaviour of the concrete beams reinforced with GFRP bars under impact loading using MATLAB. Experimental results were used to verify the accuracy of the system. Furthermore, the model was validated for the use of GFRP bars for reinforcing concrete beams. A comparative analysis of experimental dynamic mid-span deflections and dynamic deflections obtained from the punching shear model are included with a high degree of accuracy obtained.