Seminar on Elasticity and Wave Propagation in Granular Materials

Kianoosh Taghizadeh (University of Twente, NL – University of Stuttgart, DE)

(Hosted by Professor Pak)

Abstract: Complex mixtures with more than one particle species can exhibit enhanced mechanical properties, better than each of the ingredients. The interplay of soft with stiff particles is one reason for this. The focus of this work is the investigation of elastic and dissipative behavior of isotropic, dense, mixed (soft-stiff) assemblies. In particular, the attention is devoted to the effect of microscopic parameters (e.g. stiffness, friction, cohesion) on the macroscopic response (e.g. elastic moduli, attenuation). The research methodology combines experiments, numerical simulations, theory. The study of wave propagation in granular materials allows inferring many fundamental properties of particulate systems such as effective elastic and dissipative mechanisms as well as their dispersive interplay. Measurements of both phase velocities and attenuation provide complementary information about intrinsic material properties. Soft-stiff mixtures, with the same particle size, tested in the geomechanical laboratory, using a triaxial cell equipped with wave transducers, display a discontinuous dependence of wave speed with composition. The diffusive characteristic of energy propagation (scattering) and its frequency dependence (attenuation) are passed into a reduced-order model, a master equation devised and utilized for analytically predicting the transfer of energy across a few different wavenumber ranges, in a one-dimensional chain.

Bio: Kianoosh completed his B.Eng degree in mechanical engineering at Malek-Ashtar University of Technology, Iran. He received his M.Sc degree in Computational Materials Science from Technical University Bergakademie Freiberg, Germany, where he worked with the applied mechanics and solid mechanics group chaired by Prof. Meinhard Kuna.; and his master thesis was awarded the DAAD prize. After completing his master studies, he received a Marie Curie fellowship for his Ph.D in the multi-scale mechanics group, Faculty of Engineering Technology (ET), chaired by Prof. Stefan Luding at the University of Twente, Netherlands. His interests in granular materials evolved from his dissertation research on “Elasticity and Wave Propagation in Particulate Systems”. Currently, he has been engaged in developing models to describe their static and dynamic behaviour of granular systems as a post-doc fellow (funded by DFG-Schwerpunktprogramm- SPP 1897), in the Continuum Mechanics group, faculty of Civil and Environmental Engineering, at the University of Stuttgart, Germany, chaired by Prof. Holger Steeb.

Monday, 9/10/1398, 12:00-13:00 p.m., Room 202, Civil Engineering Department

Seminar on the Application of Passive Energy Dissipation Devices in Seismic Strengthening of Structures

Dipti Ranjan Sahoo

Associate Professor, Department of Civil Engineering ,Indian Institute of Technology Delhi,New Delhi- 110016 (INDIA)

E-mail: ,

(Hosted by professor Khaloo)

Dr Dipti Ranjan Sahoo is an Associate Professor in the Department of Civil Engineering at Indian Institute of Technology (IIT), Delhi. He received his Ph.D. in Civil Engineering from IIT Kanpur in 2008 and worked as a Postdoctoral Fellow at the University of Texas at Arlington, USA during 2008-2010. His research interests are seismic design and behavior of steel structures, Passive vibration control and performance-based seismic design. He is a recipient of the prestigious Indian National Academy of engineering (INAE) Yong Engineer Aware, Institution of Engineers (India) Young Engineer Award. Department of Atomic Energy Young Scientist Award, and Department of Science and Technology Young Scientist Award. He has published more than 200 research articles in the reputed International and National Journal and Conferences. He has already supervised 7 Ph.D. dissertations and more than 100 Masters and Bachelors project and is currently guiding 11 Ph.D. students. He is the Associate Editor of Indian Society of Earthquake Technology (ISET) Journal and for the revision of Indian Standard codes for the revision of Indian Standard codes for design of reinforced concrete and prestressed concrete structures.


Passive energy dissipation technique is widely adopted in the design practices to improve the seismic performance of structures. Metallic dampers are considered as one of the cost-effective passive devices available till date. This seminar was focused on the recent advances on the various types of metallic dampers and their applications in seismic retrofitting of structures. Specifically, Buckling –restrained braces (BRBs), Shear and flexure yielding devices (SAFYDs), and Steel Plate Shear walls (SPSWs) were discussed in detail. The applications of these device in controlling the seismic collapse of deficient non-ductile RC frames will be presented. The seminar also touched upon the real-time hybrid simulation and testing technique to evaluate the seismic performance of structures. Finally, the scope and funding availability for higher studies at Indian Institute of Technology (IIT) Delhi were presented in the seminar.