PSI - Issue 44

Hasan Borke Birgin et al. / Procedia Structural Integrity 44 (2023) 1624–1631 Hasan Borke Birgin et al. / Structural Integrity Procedia 00 (2022) 000–000

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distances to the data acquisition system. Moreover, the placement of the sensors is not usually an easy task, due to difficulties in the application, in the maintenance and checking. The monitoring software systems are generally complex, and the collected data size is big, so that a regular intervention is demanded during the operation. All the above concerns could be addressed by the use of novel multifunctional structural materials with self-sensing and self inspecting capabilities. Those materials are regular load-bearing structural materials which could be provided by multifunctional sensing capabilities through the addition of electrically conductive and piezoresistive particles. This paper focuses on the dynamic sensing of large-scale reinforced beams made of smart self-sensing concrete with carbon microfibers. The beams, produced with different setups, have been investigated in dynamic tests, in order to evaluate their identification capabilities. In particular, this paper presents and discusses the findings of dynamic sensing tests conducted on the two real-scale (150 x 250 x 3200 mm 3 ) reinforced concrete beams. One of the beams was made of bulk CMF-concrete composite material, while the other one included embedded small sensors made of the same smart fiber-reinforced concrete. After a brief section about the researches available in literature about smart concrete for monitoring purposes, with particular attention to real-scale applications, the paper describes the materials, the samples and the experimental setups. Then, the results on full-scale beams are presented and commented. Structural health monitoring (SHM) becomes more critical as time passes and the existing civil structures undergo material deterioration. SHM has been always a popular research topic since the sensor technologies have been evolving, the algorithms of data processing have been advancing, and the number of critical structures which need a control during their service life, has increased. The need for reliable, cost-effective, and durable SHM solutions is crucial. As a matter of fact, most of the monitoring practices are developed particularly for specific buildings or infrastructures, rather than being extensively used for monitoring the structures located in active seismic zones (Birgin et al. 2020 a and b). The popular methodology of SHM is usually carried out through dynamic sensing and extraction of dynamic parameters of structures through accelerometers or other traditional sensors. The acquired data can be compared with digital models created by employing finite element modeling tools, yielding a powerful early warning system against life-threatening events (Ding et al. 2020, Yoo et al. 2018). However, traditional high-sensitive sensors’ systems for dynamic monitoring present in the market have high costs since the ambient vibrations expected for the majority of structures have low amplitudes. Moreover, the sensor orientations, sensor-structure interaction, and power sources are limiting factors for the extensive deployment of SHM systems in civil engineering. Smart materials, with multifunctional properties, could represent a solution for the drawbacks of traditional systems, because they have the potential to be themselves self-sensors for SHM (Han et al. 2011, Rainieri et al. 2013). Concrete, in this sense, is a promising candidate as a construction matrix for smart materials, due to its composite nature. It is currently the main construction material for civil engineering, and its matrix material, i.e. cement, is one of the widely investigated binders for the production of multifunctional self-sensing materials (Han et al. 2015, Ubertini and D’Alessandro 2018). Carbon-based conductive particles are generally used for doping cement-based self sensing composites. Among them, carbon microfibers (CMF) appear appropriate inclusions for structures and infrastructures since their dispersion methodology is suitable for great amounts of material (D’Alessandro et al. 2022). Cementitious smart materials, casted in small-, medium- and large-scale elements, are able to generate voltage responses that are scaled to acting load magnitudes (D’Alessandro et al. 2016, Meoni et. Al. 2018). The voltage responses, generated and acquired through dedicated sensing circuitry and data acquisition systems, are capable of measuring and logging the electrical resistance time history of the smart material sensor body (Downey et al. 2018). The smart sensors are connected to electrical circuits through internal or external electrodes, which could be tailored according to the specific application. 3. Materials and samples This section describes the concrete materials adopted for the preparation of small samples, for embedding applications, and of the full-scale elements, together with the specific electrical setup for both types of samples. 2. State-of-art