Simple Aseismic Reinforcement of Steel Structures Using Knee Braces with High-Hardness Vises

A novel technique for upgrading the seismic resistance of steel buildings by adding knee braces to existing structures using vises was proposed by researchers in 2022. A feature of this retrofitting method is the easy setup owing to its use of vises made from high-hardness metal. Tests were conducted to investigate two main failure modes: slipping failure at the connection and yielding and buckling failure of the knee brace. The retrofitting design is discussed based on a comparison between the slipping strengths obtained through tests and calculations. Furthermore, an analytical study, using the finite element method (FEM), was conducted to evaluate the test results of retrofitted frames that failed in terms of the yielding and buckling of the knee braces. The findings of the analyses are consistent with the test results. This study included a stress relaxation test to assess the long-term performance of the vises.