Development of reinforced concrete column with embedded concrete hinge and lateral restraints for Anti-Catastrophe oriented design

In Japan, since the 2011 Tohoku Earthquake, there has been a growing interest in addressing earthquakes that exceed design assumptions. Consequently, the concept of "anti-catastrophe" has been proposed as a new approach to the seismic design of infrastructures. This approach necessitates considering the conditions after significant structural damage, a concept not explicitly addressed in current seismic design codes. This study proposes two types of reinforced concrete (RC) columns: Embedded Concrete Hinge RC column (ECH-RC) and Embedded Concrete Hinge unbonded bar RC column (ECH-UBRC) to minimize the uncertainty of failure behaviors of RC columns during Beyond Design-Basis Events (BDBE) while ensuring high ductility during Design -Basis Events (DBE). ECH-RC features a Mesnager hinge embedded at its base, while ECH-UBRC incorporates unbonded high-strength bars in addition to a Mesnager hinge. ECH-RC and ECH-UBRC are designed for bridge columns subjected to low axial loads. To ensure the stability of the entire bridge structure during BDBE, providing lateral restraints at large displacements is essential. Results from cyclic loading tests revealed that embedded Mesnager hinges effectively prevented the uncontrollable failure of RC columns during BDBE by limiting axial and shear deformation at the plastic hinge, while the unbonded bars enhanced the stability of RC columns.