PSI - Issue 64

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

911

4

The intermediate structure consists of a reinforced concrete ribbed floor, typical of the construction period. The dimensions of the ribbed floor include beams with a width of b = 6 cm and rib height of 30 cm, with an additional 5 cm for the compression slab. The beams of the ribbed floor are spaced at distance of a = 45 cm Vertical communication is provided by three staircases connecting all floors. Structure of the main staircase area (upper part on the fig. 4(a)) consists of a framed structure with masonry infill. The foundation structure consists of concrete foundation beams and footings. Non-load-bearing construction includes partition walls made of solid brick built with lime mortar. The external infill walls vary in thickness to match the dimensions of the reinforced concrete structure that encloses them, while internal partition walls are mostly 15 cm thick. The roof is flat and accessible. 2.2. In-situ tests The in-situ test on the building were conducted to determine the existing reinforcement of the reinforced concrete frames and the compressive strength of the concrete. Additionally, they were carried out to determine the dimensions of individual load-bearing elements of the structure. The testing of compressive strength was performed by taking cylindrical samples from three columns. The testing was conducted according to the HRN EN 12504-1:2019 method. The cylinders were extracted from the structure by drilling with a core diameter of 100 mm.

Fig. 5. Position of in situ samples taken from reinforced concrete columns

After conducting the compressive strength tests on the samples, the results ranged from f c = 30.7 MPa to a maximum value of f c = 39.6 MPa, as shown in Table 1.

Table 1. Compressive strength of concrete in columns. Sample

Force ( kN )

f c ( MPa )

V1 V2 V3

240 305 255

30.7 39.6 32.6

According to the conducted compressive strength testing of concrete samples extracted from the existing columns of the structure, the concrete strength class C25/30 will be adopted for analysis. In addition to the compressive strength testing of the existing concrete, investigative works were carried out to determine the reinforcement in the columns and the dimensions of the elements. The investigation was conducted by opening positions using invasive methods to remove the protective layer, enabling the determination of the type of reinforcing bars and their exact diameter, considering the predominantly framed structure. Furthermore, apart from determining the reinforcement in the columns, the reinforcement in the beams was also determined at the node or connection point of the beam to the column.