Stability of delayed systems for substructuring testing applications

This paper studies the applicability of a quite novel methodology of experimental test- ing so-called Real-Time Dynamic Substructuring Test (RTDST) in the assessment of protection systems for natural hazards mitigation. RTDST allows testing critical components of the structure at full-scale under realistic extreme loading conditions. Only those components where the nonlinearity is concentrated on are physically tested, whilst the remainder of the structure is simulated numerically. In this technique, un- Avoidable delays associated with the transfer system dynamics affect the signal of ex- perimental measurements which is fed-back to the numerical model. It may cause instability during the test. This work is focused on testing a passive control system based on nonlinear fluid viscous dampers. Throughout explicit stability analyses, we present a complete set of closed-form expressions to describe the dynamics of the main complex delay-induced phenomena exhibited for this system when a delay is consid- ered in the damper response. The theoretical results were confirmed numerically with good agreement.