My research focuses on the enhancement of structural resilience through implementation of sustainable structural systems and innovative technologies, particularly for steel structures. Nonlinear structural modelling under dynamic excitation and implementation of performance-based design and assessment methods are indispensable for this purpose. My past research activities can be categorized into two main areas: 1) development of state-of-the-art numerical modelling for the simulation of steel buildings and passive control devices based on large-scale experimentation 2) development/refinement of simplified and advanced methodologies for design, assessment, and retrofit of buildings.


  • Seismic design, evaluation and retrofit of steel structures
  • Structural dynamics and advanced nonlinear analysis
  • Structural resilience and sustainability
  • Passive energy dissipation devices and base isolation systems
  • Performance-based earthquake engineering
  • Tall buildings
  • Steel moment-resisting frames, concentrically braced frames and buckling-restrained braced frames
  • Cold-formed steel shear walls
  • Simplified evaluation methodologies, linear and nonlinear, static and dynamic procedures, displacement-based seismic design


Akcelyan, S., Lignos, D. G. (2023), “Seismic Assessment and Retrofit of Pre-Northridge High Rise Steel Moment Resisting Frame Buildings with Bilinear Oil Dampers“Buildings, Vol.13, No.1, DOI: 10.3390/buildings13010139 

Akcelyan, S., Lignos, D. G. (2021). “Rate-dependent modl for simulating the hysteretic behaviour of low-yield stress buckling-restrained braces under dynamic excitations.” Engineering Structures, 230.

Akcelyan, S., Lignos, D. G.,  (2019). “A practical method for seismic retrofit of tall buildings with supplemental damping.” Proceedings of the 12th Canadian Conference on Earthquake Engineering, Quebec City.

Akcelyan, S., Lignos, D. G., Hikino, T. (2018). “Adaptive numerical method algorithms for nonlinear viscous and bilinear oil damper models subjected to dynamic loading.” Soil Dynamics and Earthquake Engineering, 113, 488-502.

Akcelyan, S., Lignos, D. G.,  (2018). “Seismic retrofit of steel tall buildings with bilinear oil dampers.” Proceedings of the 16th European Conference on Earthquake Engineering, Greece.

Akcelyan, S., Lignos, D. G., Hikino, T., and Nakashima, M. (2016). “Evaluation of simplified and state-of-the-art analysis procedures for steel frame buildings equipped with supplemental damping devices based on E-Defense full-scale shake table tests.” Journal of Structural Engineering, 142(6), 04016024.

Akcelyan, S., (2017) “Seismic retrofit of existing steel tall buildings with supplemental damping devices.” Ph.D. Dissertation, McGill University, Canada.

Akcelyan, S., “Seismic analysis and evaluation of steel structures with viscous dampers.” Oral presentation during the OpenSees Days 2013 Workshop at Richmond field station at UC Berkeley. August 2013. <>.


Uniaxial material models for nonlinear viscous dampers and bilinear oil dampers have been implemented into the Open System for Earthquake Engineering Simulation (OpenSees) platform via C++ programming.

  • ViscousDamper: A new uniaxial material model, which simulates the dynamic response of nonlinear viscous dampers, including its axial stiffness and gap length of clevis. An example is provided to demonstrate the use of viscous damper material within a simple single story shear frame.
  • BilinearOilDamper: A new uniaxial material model, which simulates the dynamic response of oil dampers with a relief valve, including its axial stiffness and gap length of clevis.