## 1 Introduction  
Reinforced concrete (RC) is the most common material used in infrastructure such as bridges [1; 2]. RC columns are often the primary elements of energy dissipation in bridges subjected to seismic loads. Failure of bridge columns can cause the collapse of bridge girders, which has been the catastrophic scenario for the majority of bridges damaged in past earthquakes. After a seismic event, it is imperative to quickly assess the health condition of an RC structure to provide early warning of the structural damage. It is essential to design a structural health monitoring system that can monitor and report the health status for large-scale infrastructures in real-time.  
With attractive features of low-cost, small size, large bandwidth, and actuating-sensing functions, piezoceramics have been increasingly employed in many engineering fields [3; 4; 5; 6; 7]. In this project, piezoceramic-based devices, called smart aggregates (SA), were utilized as transducers for structural health monitoring of RC columns under a pseudo-dynamic loading procedure. In addition to the structural health monitoring function, the smart aggregate can be used to perform early-age concrete strength monitoring [8; 9], impact detection [10], seismic detection [11], and soil freeze-thaw monitoring [12], demonstrating that SAs are multi-functional devices. In previous studies, SAs have been successfully implemented for structural health monitoring of various concrete structures under different loading cases including: a concrete bridge bent-cap under static loading [13], a concrete frame under static loading [14; 15], a shear wall under reversed cyclic loading [16], columns under seismic loading [17], stress wave base communication in concrete structures [18; 19] and columns under reversed cyclic loading [20; 21]. The purpose of this project was to further verify the effectiveness of the smart aggregate in health monitoring of a RC concrete column tested with pseudo-dynamic loads.  
To verify the effectiveness of the proposed smart aggregate under pseudo-dynamic loads, the smart aggregates were used as transducers to perform health monitoring on RC columns under a mathematically simulated earthquake record. One full-scale circular RC column was designed at George Washington University based on an American Association of State Highway and Transportation Officials (AASHTO) design example for a curved bridge. The column was tested at the Newmark Structural Engineering Laboratory at the University of Illinois, Urbana-Champaign. The employed smart aggregates were embedded at pre-determined locations in the full-scale RC column to perform structural health monitoring. During the test, the column was assumed to be the pier in the same curved bridge and subjected to a simulated earthquake record, one step at a time. After each step, the stiffness of the column was calculated and the next step of the earthquake record was adjusted to account for any decrease in stiffness. Structural health monitoring was performed periodically during the approximately 40-h test. Due to the pseudo-dynamic loading, the investigated RC column was subject to crack. When the column was pushed on one side, cracks opened; when the column was pulled back, the cracks closed. In the active-sensing approach, one smart aggregate was used as an actuator to generate a repeated swept sine signal while the others were used as sensors to detect the signal response. The existence of cracks, acting as stress relief, attenuated the wave propagation, so the signal received by SA sensors correspondingly decreased. A structural damage index was formed based on the wavelet packet-based tools. The general increasing values of the developed structural damage indices for each implemented SA successfully detect the damage severity during the test. In addition, the cyclic behavior of the local damage indices successfully monitored the crack opening and closing phenomenon subject to the pseudo-dynamic loading.