PSI - Issue 5

Baris Arslan et al. / Procedia Structural Integrity 5 (2017) 171–178 Baris Arslan et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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2. Material Properties

2.1. Concrete model

The effects of the varying aggregate sizes on the mechanical properties of the concrete are investigated by many researchers[16 – 22,25 – 30]. Elices and Rocco [19] reported a detailed literature review regarding the effects of the varying aggregate sizes on the mechanical properties of simple concrete. It was reported that the modulus of elasticity decreases as the aggregate size increases. Likewise, the same trend was observed by Saouma et. al. [18] and Tasdemir. et. al. [16]. In this study, in order to investigate the effects clearly; the mechanical properties of the concretes, which are used in FEM analyses, are chosen from the study by Saouma et. al.[18] in which the sizes of the aggregates are varying most significantly within the range of 19, 36 and 76 mm respectively. Detailed mechanical properties of the concrete groups that were obtained experimentally are given in Table 1.

Table 1. The mechanical properties that were obtained experimentally from the study by Saouma et. al [18]. Max. size of aggregate (mm) Density ( kg/m 3 ) E (Mpa) f c (Mpa) f t (Mpa) 19 2390 18000 25.60 2.81 38 2420 16900 24.80 2.67 76 2480 16500 18.90 2.41

The concrete cubes are meshed with hexagonal C3D8 stress elements which have 8-node linear bricks as shown in Fig. 1. The size of the elements is refined locally in order to translate the driving forces which are generated by the PZT patch, efficiently. The mesh sizes of the concrete cube near the PZT patch are 0.25 mm and other parts are relatively coarse, which have a mesh size of 5 mm as shown in Fig. 2. Interactions between the concrete model and the PZT patch are defined as surface-based tie constraint in which all degrees of freedom (DOF) are tied kinematically.

Fig. 1. Full concrete model

Fig. 2. Locally refined concrete and PZT mesh structure

2.2. Piezoelectric Ceramic (PZT-5H)

A piezoelectric material responds to an electric potential gradient by straining, while stress causes an electric potential gradient in the material. This coupling between the electric potential gradient and the strain is the piezoelectric property of the material.