Hamed Arshadi
In this experimental study, the effects of macro-synthetic steel fibers and bidirectional carbon fiber-reinforced polymers (CFRPs) on the impact resistance of concrete specimens were studied. 54 concrete cylindrical specimens with different compressive strengths (20, 30, and 40 MPa) and with different fiber content ratios (0 %, 1 %, 1.5 %, and 2 %) were tested under impact loading. Half of these specimens were tested with the CFRP wrapping. The specimens were subjected to weight (46.7 and 66.8 kg) dropping at a height of 1.62 m. The process of weight dropping was continued until 30 % weight loss in the specimens was observed and the number of weight droppings related to this loss was recorded. Results indicated that the impact resistance of the concrete specimens (corresponding to the number of weight droppings) increased by using steel fibers or CFRP wrapping, separately. However, the results demonstrated that the specimens wrapped with the CFRP sheets had much further impact resistance than the FRCs without wrapping. Finally, the results showed that the greater the compressive strengths of the concrete, the better the impact resistance.
The majority of both land-based and off-shore, critical, and residential structures can be subjected to extreme actions such as impacts induced by extreme wind action, vehicle and vessel collisions, or explosions. It must be reminded that extreme wind actions occur more and more often because of the climate change crisis which causes extreme impact/dynamic effect on the structures (many times even larger than the structures are designed for). Then, it is vital to construct structures with acceptable impact resistance. Existing structures need retrofitting because of such cases as overloading, strength deterioration, and structural damages. Applying fiber-reinforced polymer (FRP) is one of the novel retrofitting approaches in RC structures.
Using FRC along with wrapping concrete members by FRPs can significantly affect their impact resistance. However, there are not sufficient experimental studies about this issue. Thus, in this paper, the effects of macro-synthetic steel fibers (with the production name of MEX-200) and CFRPs on the impact behavior of concrete specimens were studied. Fifty-four concrete specimens with different compressive strengths (20, 30, and 40 MPa at 28days) and with different fiber ratios (0 %, 1 %, 1.5 %, and 2 %) were constructed and tested under impact loading. Only half of these specimens were tested with CFRP wrapping. The specimens were subjected to weight dropping (46.7 kg and 66.8 kg). After crashing the weight on the specimens, the weight of the specimens was measured and compared to their weights before crashing. This process of weight dropping was continued until the destruction of the specimens (30 % weight loss) was observed. The number of weight releasing necessitated to 30 % weight loss (representative to the impact resistance) was counted. Results indicated that the impact resistance of the concrete specimens increased by an increase in steel fiber content ratios or CFRP wrapping. However, the results indicated that the specimens wrapped with the CFRPs had much better impact behavior than the FRC specimens without the CFRP wrapping. Finally, the experimental observations demonstrated that the greater the compressive strengths of the specimens, the greater the impact resistance.
Semnan University of Medical Sciences and Health Services
Kheyroddin, A., Arshadi, H., Khedri, J. “The Resistance of Fiber-reinforced Concrete with Steel Fibers and CFRP to Drop-weight Impact”, Periodica Polytechnica C
