# Performance Assessment of a Renovated Precast Concrete Bridge Using Static and Dynamic Tests
## 1 Introduction  
Bridges are among the most complex and important structures of civil infrastructure. They must operate in demanding environments, and withstand extreme loads and deterioration which occur during their operational lifespan [1]. Therefore, maintenance and monitoring of their state is crucial, mainly for safety and economic reasons [2]. Visual inspection represents a standard process in many countries [3]. As mentioned in [4], the identification of damages from visual inspections are usually influenced by the subjectivity of the expert. There are other issues with visual inspections--some locations are not accessible; at other times it is difficult to determine the severity of damage. Due to these reasons and possible road closures, bridge owners and managers are interested in automation of the process by using sensors. Many researchers across the United States [1], Europe [2; 5; 6; 7; 8], and Asia [9; 10; 11; 12] have taken advantage of the rapid evolution of sensing technologies in the last few decades and implemented methods of structural health monitoring (SHM) to track the structural integrity of bridges. An important part of SHM is testing. Two main approaches to testing are known: destructive and non-destructive. Destructive methods use demolition of material to determine material characteristics. On the other hand, the advantage of non-destructive testing is that the observed structure will remain undamaged after a test. Therefore, non-destructive testing is a well-developed research and practical field, and vibration-based methods are one part of that field. According to [13], vibration-based SHM techniques can be divided into global non-destructive techniques, local non-destructive techniques, and long-term application of SHM techniques. Local techniques deal with one structural element, such as cables [12]. On the other hand, global techniques use data from a whole structure. Furthermore, the testing methods can be divided according to how the response is excited: statically or dynamically. The design of static tests is less difficult, as only a stationary load is used. The possibility of easier evaluation is also advantageous, and the results can be simpler compared to the results from numerical models. On the other hand, they have less practical value, and they do not show the real behavior of structures during dynamic loads. Dynamic test methods that examine the behavior of structures under dynamic loads are mainly applied to bridges. These structures are loaded by moving vehicles, pedestrians, or ambient dynamic loads. The fast evolution of sensing technology has enabled the incorporation of SHM methods into the life cycle of bridges [14]. It must be noted that a visual inspection cannot be completely substituted by SHM methods. Several types of measuring devices and compatible sensors are now available. The most common types of sensors are strain gauges, accelerometers, speedometer gauges, temperature sensors, and optical sensors, among others. The above-mentioned authors mainly used one type of sensor in their studies. Strains were measured in [1], accelerometers were used in [5] and [8], and radar was applied in [9]. The combination of multiple sensor types was presented in [11]. A similar approach was selected in this work; a measuring device with the ability to measure accelerations, temperatures and strains was used in combination with the use of radar interferometry and a video camera. This paper presents the development of a SHM strategy as an application of a fusion of well-known methods during various stages of testing (e.g., numerical modal analysis to obtain initial dynamic parameters, operational modal analysis [15], verification and validation of a FEM model [16], and vehicle-bridge interactions [17]) in order to obtain the global static and dynamic response of a reinforced concrete bridge, along with local measurements of strains in external cables.