PSI - Issue 81

Mykhailo Hud et al. / Procedia Structural Integrity 81 (2026) 486–492

488

1 opening

2 opening

Balcony

Fig 2. Alternative structural configurations

The analysed models included a configuration (Fig 2.) with one opening on each storey, a variant with two openings per storey, and a scheme featuring asymmetrically positioned balconies. The introduction of these modifications made it possible to trace the transformation of stiffness characteristics and the geometric structure of the frame under conditions of variable weakening of elements or uneven redistribution of material within the structural system. 3. Result and discussion This section presents the results of the modal analysis for both the basic and modified models of a frame building with an asymmetrical layout. A comparison of the frequency spectra and vibration modes of these materials can provide insights into the impact of geometric changes on the structure's spatial stiffness and its response to dynamic loads.

Frequency (Hz)

14

12

10

8

6

Frequency (Hz)

4

2

0

1

2

3

4

5

6

7

8

9

10

11

Mode

Fig 3. Frequencies of basic frame model

The graph (Fig 3.) shows the change in the natural frequencies of the basic frame model according to the mode number. The curve displays a discernible upward trend, commencing at 1.318 Hz and ascending to over 12 Hz in the higher modes. The increase is uneven, with small plateaus at modes 1 – 2, 4 – 5, 7 – 8, and 10 – 11, suggesting that certain vibration patterns repeat across these ranges. The most significant increase is observed around the midpoint of the spectrum, from 7.775 Hz to above 12 Hz, suggesting the activation of stiffer or more localised oscillation modes.