Modern regulations concerning railway bridges are based on the approach of structural dynamics, which is described in PN-EN standards. This paper presents the results of theoretical dynamic analysis of the HSLM-A train set loading on the structure of a pre-stressed concrete arch bridge - the first railway bridge of its type which was built in Poland (completed in 1959). The recommendations of PN-EN have been followed and modal analysis was carried out to define the sensitivity of the structure to chosen eigenforms. Additionally the paper presents a course of calculations and the conclusions obtained from the analysis of displacements, accelerations, and bending moments induced in the structure through a simulated passage of a high-speed train in the context of the requirements of PN-EN Standards. The conclusions from the current calculations can be used for dynamic analysis of bridges of similar structural solutions.
The primary objective of the present study was to determine the seasonal dynamics of ciliates in activated sludge. Studies were carried out in order to verify the hypothesis that fertility of a habitat may significantly influence the seasonal dynamics of the abundance of ciliates, as well as the number and intensity of correlations between physic-chemical parameters and ciliates. It seems that the values of numbers of ciliates were seasonally changeable. The highest numbers of ciliates were found in spring and summer, however the lowest numbers of ciliate communities were noted in winter. The studies showed that protozoa community is determined by ammonia mainly in summer. In spring and winter additional factors may be important. Probably suspended solid, total organic carbon and concentration of appropriate food (bacteria and flagellates) are the major regulator of abundance of ciliates.