PSI - Issue 64

4

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

M. Pedram et al. / Procedia Structural Integrity 64 (2024) 621–628

624

Fig. 1- Boundary conditions for the FE models

Element type and mesh The finite element models were formed by considering the 3D geometrical dimensions of slabs. The geometrical model was discretised by 8-node thermal field volume elements of hexahedral shape and linear interpolation (HF8 in the element library of LUSAS). These models intended to simulate the 250× 250× 100mm concrete slabs with variable subsurface voids of 100×100mm surface area at 5, 10, 15, 20 and 25mm depths. Therefore, the 100mm depth of the slabs (z-direction) was discretised into 20 elements of 5mm thickness. This facilitated adjusting the concrete cover above the void into 1, to 5 rows of elements for the concrete cover of 5 to 25mm depth, respectively. The length (x-direction) and width (y-direction) of models were divided into 10 elements of 25mm length and width. Therefore, the models comprise 10×10×20 elements (2000 in total). Fig. 2 shows the typical FE model of the D5 slab. In addition, this figure shows the node numbers corresponding to 9 designated spots for surface temperature analysis. Node 2785 corresponds to point #5 in the centre of the void cover. The average temperature of 8 points on the surface of intact concrete was used for thermal contrast calculation. That is the thermal contrast was the difference of temperature at node 2785 and the average of 8 points on the intact concrete.