Saranya S supervised by Dr. Sunitha Palissery received her Doctorate of Philosophy (Ph.D) in Civil Engineering. Here’s a summary of her research work on Seismic Design of Non-Structural Elements in Critical RC Buildings

Non-Structural Elements (NSEs) such as building contents, appendages, services and utilities of buildings are not usually considered as part of lateral force resisting system and are not commonly included in the numerical model of Structural Elements (SEs) and structural system. But, experience from the past earthquakes demonstrates that the presence of the NSEs alter the load paths of the SEs, thereby jeopardizing earthquake safety and functionality of buildings. These failures are unacceptable in important buildings like hospitals; such structures need to be designed to remain occupiable after earthquakes. Alongside, those buildings that are equipped with expensive acceleration-sensitive NSEs, such as medical instruments, need to remain operational after an earthquake. Further, most analytical and numerical studies utilize Floor Response Spectrum approach (with NSEs not considered) or Decoupled Model Approach (with NSEs modelled separately), to estimate acceleration demands on NSEs. This approach clearly neglects the dynamic interaction between SE-NSE, consequently estimating unrealistic seismic demands on NSEs. Further, the acceleration demands on NSEs are influenced by the characteristics of ground motions, higher mode participation, structural irregularities etc. Thus, there is a need to fine-tune the design parameters of NSEs using Coupled Model Approach (with SEs-NSEs modelled together) and consider other influencing parameters. 

In this thesis, firstly, the seismic response of critical low-rise (5-storey) and midrise (10-storey) RC wall-frame buildings is assessed using nonlinear static and nonlinear response history analyses under near-fault and far-fault ground motions. Secondly, the seismic response of acceleration-sensitive, floor-mounted elastic NSEs with fundamental periods (TNSE) ranging from 0.1s to 1.0s (in increments of 0.1s) and weights from 10 kN to 50 kN (in increments of 10 kN), mounted on all floors of these buildings are investigated employing coupled modelling. Results suggest that higher-mode effects are prominent in mid-rise buildings than in low-rise buildings. The extent of building nonlinearity is maximum under near-fault ground motions and in high seismic zones compared to farfault ground motions and low seismic zones. Floor Amplification Factor (FAF) and Component Amplification Factor (CAF) are the critical design parameters influencing the seismic behaviour of NSEs in estimating the design horizontal lateral force. Low-rise and mid-rise buildings have maximum FAFs of 2.5 and 2.0, respectively. In low-rise buildings, maximum CAF is 5.0 on top floors for TSE < 0.5s and TNSE ≥ 0.5s, due to amplification between TNSE and elongated fundamental period of the building, resulting from structural nonlinearity. In mid-rise buildings, maximum CAF is 4.0 at bottom and top floors for TSE < 1.4s and 0.3s ≤ TNSE ≤ 0.7s, due to influence of higher modes. Maximum CAF is 2.0 at bottom floors in both low-rise and mid-rise buildings. Based on these findings, analytical expressions for FAF and CAF spectra are proposed for two sets of seismic zones. The proposed expressions aim to complement current code recommendations, specifically tailored to the characteristics of low-rise and mid-rise critical RC wall–frame buildings. The efficacy of the proposed expressions is demonstrated by comparing them with current code provisions and results from previous studies; the proposed FAF and CAF are found to provide realistic estimation of the seismic demands on NSEs. 

July 2026