**4. Comparison of calculated bearing capacity with experimental data**

According to the proposed method, the algorithm for estimate the stress–strain state and calculate the load-bearing capacity of compressed concrete filled steel tube elements was developed and this algorithm was implemented in the computer program. The results of the calculations are compared with the experiment data of CFST samples made of normal concrete. These data were obtained by many researchers for 569 experiments with short centrally compressed columns, 512 flexible centrally compressed columns and 292 eccentrically compressed elements.

Experimental data was taken from research works [16, 23, 24].

In order to obtain more objective information, the experimental data of samples were analyzed with a large range of geometric and structural parameter variation:


The results of the comparison show a completely satisfactory coincidence of experimental destructive loads with theoretical values (**Table 2**).

The data in **Table 2** show a good agreement between theory and practice.

According to the results of the data of work [23], the calculations according to Eurocode 4 (EN 1994-1-1: 2004) have a slightly worse accuracy. However, the main advantage of the proposed calculation method is its versatility. In particular, when using this method, one can take into account the presence of a high-strength rod and (or) spiral reinforcement, the effect of preliminary lateral compression of the concrete core [16]. The research work [13] verified the acceptability of the EN 1994-1-1: 2004 method for calculating the strength of compressed CFST made of various types of concrete: normal, ultrahigh-strength, self-compacting, light-weight concretes and engineered cementitious composite. It is concluded that the


**Table 2.**

*Summary of Comparison of Calculated Bearing Capacity with Experimental Data.*

calculation accuracy is satisfactory only for normal concrete. The proposed method makes it possible, with an appropriate selection of the material coefficients *a* and *b* in Eqs. (14), (16) and (20), to provide the required accuracy of calculations.

Based on the results of the carried out analysis, the following values of the coefficients of materials for various types of concrete can be recommended:


Given recommendations are preliminary and need to be clarified, since they have been obtained on the basis of processing a very limited amount of experiments.
