Experimental assessment of dynamic and static based stiffness indices for RC structures

• Main Authors: Fayyadh, Moatasem M., Razak, Hashim Abdul
• Format: Article
• Published: Elsevier Science Inc 2022
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.um.edu.my/40734/

This paper presents the results obtained from experimental modal analysis and static load testing to examine the suitability of the dynamic parameters to estimate stiffness deterioration severity in RC structures. The study investigates the accuracy of different dynamic-based stiffness indices compared to static-based flexural and shear stiffness indices and how different damage levels and scenarios impact them. The flexural damage scenario was found to have the weakest effect on stiffness deterioration, indicated by the frequency-based stiffness index, while shear damage at quarter-span has the greatest influence. The frequency-based stiffness index indicates a stiffness increase when the damage level reaches 0.15, which is believed to be related to the composite effect in RC structures, as discussed by Abdul Razak and Fayyadh (2013). The combined modal parameters stiffness index revealed that the flexural damage scenario has the weakest influence on stiffness deterioration, while shear damage closer to the support has the highest effect on stiffness deterioration. The main difference between the combined parameters index and the other two dynamic indices is that the combined parameters index detects global stiffness changes through frequency, while the local stiffness changes are detected through the mode shape vectors. The general trend of the dynamic-based indices shows that the MAC-based stiffness index gives the lowest sensitivity for stiffness change for all damage levels, while the combined parameters-based stiffness index gives the highest sensitivity among the dynamic parameters indices to detect the stiffness deterioration for all damage levels. The static-based flexural stiffness index shows lower sensitivity to stiffness deterioration than the static-based shear stiffness index. The static-based stiffness indices show better sensitivity than the dynamicbased indices; however, the static load test is time-consuming, equipment and labour intensive, and causes significant disruptions to the existing use of the structures. Thus, the dynamic parameters-based stiffness indices are more suitable for existing structures.