Monitoring the Seismic Behavior of a Scaled RC Frame with Intermediate Ductility in a Shaking Table Test
Mohammad Vasef, Mohammad Sadegh Marefat, Sina Shid-Moosavi, Peng "Patrick" Sun
TL;DR
This work develops variational methods to establish the existence of $T$-periodic solutions for Hamiltonian systems under convexity and subquadratic growth at infinity. Central to the approach is the dual action functional, with explicit spectral conditions involving $\gamma$, $\lambda$, and $\delta$ derived from asymptotic matrices $A_{\infty}$ and $B_{\infty}$, as well as equilibria data from $H''(\xi_k)$. It provides nontriviality criteria showing that, under inequalities like $\gamma< -\lambda < \delta$, the minimizers yield nonzero periodic orbits, including non-constant solutions when appropriate spectral bounds are satisfied. By situating these results among Rabinowitz, Clarke & Ekeland, and Michalek & Tarantello, the paper highlights the historical development and practical utility of convex-subquadratic Hamiltonian theory for identifying periodic orbits and subharmonics in nonlinear dynamics.
Abstract
One of the commonly used seismic force-resisting systems in structures is Reinforced Concrete (RC) Intermediate Moment Frames (IMF). Although using the IMF is not allowed in high seismic hazard zones according to ASCE 7-10, it is permitted in both Iran's 2800 Seismic Standard and New Zealand's Seismic Code. This study investigates the seismic behavior of a reinforced concrete IMF subjected to earthquake excitations using shaking table tests on a 2D RC structural model which is designed under the regulations of ACI318-19. The scale factor of 1/2.78 is selected for the frame fabrication due to the size limit of the shaking table. The constructed model has three stories with a height as 115 cm for each story, the clear length of beams as 151 cm, and cross-sectional dimensions of columns and beams as 11 $\times$ 11 cm and 12 $\times$ 11 cm, respectively. The whole structure is supported by a foundation that is 173 cm long, 52 cm wide, and 22 cm deep. Columns and beams are reinforced with 8 mm diameter longitudinal ribbed bars and stirrups with 6 mm diameter. The tests are conducted in stages with increasing peak ground acceleration (PGA) till the failure of the frame. Sarpol-E-Zahab earthquake seismic record is adopted for the experiment. The structural responses (e.g., displacements, longitudinal bars' strain, crack propagation, accelerations) are monitored during the test using both conventional sensors and vison-based sensors. As a comparative study, both conventional sensors and computer vision techniques are used to monitor the health state and to analyze the structural dynamics of the scaled RC frame structure.