An approximated method for calculations of the natural period for towers and columns (after PN-77/B-02011 standard) is evolved in the paper using the integration instead of the summation of products of concentrated masses and squares of deflections. Formulas for calculations of first natural frequency (period) for columns shaped like frustum of cone or pyramid are derived. The special case of tube columns shaped like a cone (or pyramid) when generating lines of external and internal cone are crossing the cone (or pyramid) axis in the same point is also solved. Examples of calculations and a comparison of results will be published in the second part.

Stability analysis of the rod subjected to non-conservative load is presented. Static and dynamic criterion of bifurcation and flutter of the structure is discussed. The influence of the angle αof non-conservative load for the critical parameters is detected via sensitivity analysis.

In the paper the Hasofer-Lind index is applied for determining the probability of stability loss truss structure under random load. In 1974 Hasofer-Lind proposed a modified reliability index that did not exhibit the invariance problem. The “correction” is to evaluate the limit state function at a point known as the “design point” instead of the mean values. The design point is generally not known a priori, an iteration technique must be used to solve for the reliability index. The paper shows how changes reliability index under influence different probability density function.

The subject of interest is a girder bridge suspended to the arch. As it was recognised during design, the internal forces in some of suspension rods are changing rapidly with a change of selected geometrical parameters of the structure. The sensitivity analysis of axial forces in all suspension rods depending on location of the arch with respect to the girder part of the bridge is performed.

A biohygrothermal, calculation model of fungus growth, elaborated at Fraunhofer Institute for Building Physics in Germany and computer program WUFI+, built by contribution of the author, are presented in this paper. The software enables calculation of transient heat and moisture courses on building component’s surfaces and estimation, on this base, the threat with fungus growth. Exemplary calculations for typical dwelling house were carried out. A required and diminished, to economize energy consumption, ventilation was assumed. A predicted level of fungus growth threat was compared between these two cases.