Researchers at the Structural Engineering Laboratory of the Department of Building and Civil Engineering at Toyohashi University of Technology have developed a new concept that can use non-bonded carbon fiber reinforced plastic (CFRP) laminates to strengthen steel in critical building structures to increase steel buckling performance. This method does not require surface treatment before applying CFRP, because CFRP does not adhere to the surface of the steel, but only improves the structural strength by increasing the bending rigidity of the steel.
Since CFRP successfully reinforced concrete in the field of civil engineering, it has developed into a method of strengthening steel members instead of traditional steel plates. CFRP is widely used because of its light weight, high strength-to-weight ratio, fatigue resistance, and corrosion resistance. However, to date, the research and development of CFRP reinforcement steel has mainly focused on the bonding technology, that is, the use of adhesives to adhere CFRP to the steel surface. However, the disadvantage of bonding reinforcement is that complex and time-consuming surface treatment work is required before installing CFRP. In addition, since the steel is completely exposed to the environment during the entire service life, the key to this reinforcement technology-the bond strength performance between steel and CFRP will also be significantly reduced. Replacing this method with new bonded CFRP technology is also not a particularly suitable solution because it is unlikely to be cost-effective.
Therefore, the research team developed a method that does not bond CFRP to the steel surface, but uses CFRP to strengthen the steel. Studies have shown that this method can delay the buckling of the steel and improve the compression capacity of the steel rod. Whether the compression capacity is improved is affected by the number of carbon fiber layers.
Material core breakthrough
Fengky Satria Yoresta, the first author of the study, said: "We have developed this method of strengthening CFRP steel without bonding to replace the method of bonding CFRP to the steel surface. The main advantage of this method is that it is simpler It takes less time and is particularly suitable for existing building structural elements. It eliminates the trouble of processing steel surfaces (such as sandblasting or manual grinding, etc.), which can greatly save costs. "
The research team leader and associate professor Yukihiro Matsumoto added: "Almost all previous studies used binders to strengthen steel members with CFRP. This method is quite complicated because steel surfaces need to be properly treated before CFRP is applied. In order to allow the steel surface to bond with CFRP, the surface treatment will also affect the bonding strength. In addition, we cannot fully estimate that the bonding performance between CFRP and steel will be affected when the steel is exposed to the environment during its life How is it affected. Therefore, we tried to develop a non-bonded reinforcement method to improve the traditional reinforcement method. "
He also said: "Unbonded reinforcement method is very useful, easy to adopt and manage. However, our method can not transfer stress smoothly, so we need to create an appropriate mechanical model. Finally, we conducted mechanical simulations and experiments to prove The role of this reinforcement method. "
The research team believes that the unbonded CFRP reinforcement method it developed is not only applicable to civil engineering, but also applied to other fields such as aerospace, automotive and marine industries. This new method has a bright future and is expected to be used to quickly produce innovative high-quality products.