PSI - Issue 64

Galić Josip et al. / Procedia Structural Integrity 64 (2024) 908 –917 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 9. (a) steel truss on facade, (b) strengthened existing slab with steel straps

Reinforced concrete walls have been added to the side of building and next to the staircase as additional bracing in the transverse direction. The walls on the side are not the full length in purpose to achieve a more ductile behavior of the entire structure. Additionally, efforts have been made to ensure that all added walls are approximately the same length and evenly distributed. This was important because the existing ribbed slab is very poorly reinforced in the area of the compression slab. Therefore, to prevent cracking of the compression slab, it has been additionally reinforced with steel strips. Modal analysis has shown improved behavior of the structure, where the first two modes are purely translational oscillation, while the third mode is rotational oscillation. The calculation assumes the behavior of the frame for the existing load-bearing structure of reinforced concrete beams and columns, so the joints are additionally reinforced by wrapping them with CFRP according with CNR-DT (2014) fabric because greater shear reinforcement is needed at these locations than what was originally installed. These areas are very sensitive to seismic action, so it was important to strengthen them.

Fig. 10. (a) New RC walls, (b) Added steel truss on facade, (c) First mode is X direction translation f = 1,34 Hz, second mode X direction translation f = 1,50 Hz

3.2. Construction of strenghtening The construction work on building are still ongoing. So far, all reinforced concrete work for strengthening have been completed, as well as most of the steel truss, as can be seen in the photographs on fig. 11.

Fig. 11. (a) strengthened node column-beam with CFRP, (b) view on steel truss on façade, (c) detail on steel truss on façade with visible holes for connection of steel truss with existing RC frame ,