Type C seismic energy dissipation devices are among the modern systems used to improve the seismic performance of structures. These devices dissipate a portion of the seismic energy imparted to a structure, thereby reducing its dynamic response, internal forces, and seismic deformations. Their operating mechanism primarily relies on the plastic behavior of steel and its yielding under cyclic seismic loading. This results in energy dissipation through hysteretic loops generated by repeated loading, unloading, and load reversal cycles. Consequently, these devices enhance the structure’s ability to absorb seismic energy and control deformation. Such systems have gained increasing importance in the seismic retrofitting of existing structures, particularly precast concrete buildings. The rectangular C-Device consists of a steel element with a configuration resembling a portal frame, incorporating circular transitions at its internal corners. This geometric detail aims to reduce stress concentrations and improve the distribution of stresses and strains. It also helps control the energy dissipation zone by directing plastic deformations toward areas specifically designed to dissipate energy. This configuration contributes to more stable hysteretic behavior under reversed cyclic loading. Furthermore, the device can be fabricated from steel plates, providing manufacturing flexibility and facilitating its integration into seismic strengthening systems. A study published in 2022, entitled “Rectangular C-Device with Circular Transitions: Modelling Approaches and Development of an Equivalent Nonlinear Inelastic Spring for Seismic Analysis,” investigated a numerical methodology for representing the nonlinear and hysteretic behavior of C-Devices using Finite Element Analysis (FEA). The study adopted two principal numerical modeling approaches. The first employed a simplified model based on nonlinear frame elements, whereas the second used a more detailed model representing the device as a nonlinear steel plate subjected to in-plane loading, with more detailed representation of the restraints and boundary conditions at the connection regions. One of the study’s most significant contributions was the development of an equivalent nonlinear inelastic uniaxial spring capable of representing the hysteretic behavior of a C-Device without requiring all its geometric details to be modeled in every structural analysis. The spring properties were determined and calibrated using numerical analysis results. The accuracy of the model was verified by comparing its response with detailed numerical models and experimental results under monotonic and reversed cyclic loading. The comparisons demonstrated good agreement between the response of the equivalent spring and that of the detailed models, supporting its use in reducing the computational time and effort required for nonlinear seismic analyses. The significance of this methodology lies in the possibility of incorporating the equivalent nonlinear spring into structural analysis software, such as SAP2000, to represent energy dissipation devices in a simplified and efficient manner, provided that the spring properties are appropriately determined and calibrated using reliable analytical or experimental results. This approach enables engineers to investigate the seismic response of structures and evaluate forces, displacements, and interstory drifts, in addition to examining hysteretic energy dissipation and the behavior of the device during different loading cycles. It can also serve as an effective tool for developing seismic strengthening and rehabilitation solutions for existing structures, including precast concrete buildings. From a seismic design perspective, the use of energy dissipation devices is based on the concept of damage distribution and controlling the location of plastic yielding. The objective is to concentrate energy dissipation in specifically designed components rather than allowing uncontrolled damage to occur in the primary structural elements. Accordingly, the appropriate design of these devices can contribute to a more predictable seismic response mechanism and improve the safety and performance of structures subjected to repeated seismic loading. Prepared by: Dr. Uday Al-Mamoori Specialization: Civil Engineering – Structural and Earthquake Engineering Scientific Reference: Martinez-Rueda, E., & Al-Mamoori, O. (2022). Rectangular C-Device with Circular Transitions: Modelling Approaches and Development of an Equivalent Nonlinear Inelastic Spring for Seismic Analysis. Civil Engineering Beyond Limits, 3(3), 1–10. Article 1579. DOI: https://doi.org/10.36937/cebel.2022.1579