EXPERIMENTAL EVALUATION OF SEISMIC RESPONSE OF NON STRUCTURAL COMPONENTS IN RC FRAMES

Abstract

Non-structural elements (NSEs) such as cable trays, pipelines, HVAC systems, and suspended utilities are highly vulnerable during earthquakes and play an important role in maintaining building functionality after seismic events. Recognizing the importance of seismic safety of utility systems, IS 1893 introduced new provisions for “Architectural Elements and Utilities (AEUs)” in Indian seismic design practice. However, limited experimental validation is available for these newly introduced provisions. The present study investigates the seismic behaviour of cable tray systems installed in a structural frame model subjected to shake table excitation. Cable trays with rigid and flexible support configurations were installed at different floor levels, and acceleration response was measured at the base, floor slabs, and cable tray locations under excitation frequencies ranging from 0.5 Hz to 12 Hz. Experimental results showed significant floor acceleration amplification at upper floors, with maximum Peak Floor Acceleration (PFA) of 1.5g observed at the third floor. Resonance behaviour was observed between 6.5 Hz and 8.5 Hz, resulting in sudden increase in cable tray acceleration response. The amplification factor increases significantly with elevation, showing a 50.38% rise from the 1st to the 2nd floor and a further 25.00% rise from the 2nd to the 3rd floor, resulting in an overall increase of 87.97% from the 1st to the 3rd floor. The flexible support system shows the highest amplification increase at the 1st floor (81.82%), while the increase at the 2nd and 3rd floors is approximately 53–59% compared to the rigid support system. Comparative analysis between experimentally obtained seismic forces and codal force predictions based on Draft IS 1893 and ASCE 7 indicated that actual seismic demand exceeded equivalent static codal predictions near resonance conditions. Where experimental force exceeded the IS 1893 value approximately 71%. The study highlights the importance of considering floor amplification, resonance effects, and support flexibility in seismic design of utility systems. The findings of the study contribute toward improved understanding of seismic behaviour of non-structural utility systems and provide practical design recommendations for seismic anchorage and support systems in RC buildings.