The Rayleigh’s method can be used to determine the first natural frequency of beams with variable cross-section. The authors analyse multi-segment simply supported beams, symmetrical with respect to their midpoint, having a constant width and variable height. The beams consist generally of five segments. It has been assumed that the neutral bar axis deflected during vibrations has a shape of a beam deflected by a static uniform load. The calculations were made in Mathematica environment and their results are very close to those obtained with FEM.
Przedstawiono wymagania normy PN-B-19503: 2004 w zakresie badań kratownic stalowych stosowanych jako zbrojenie prefabrykowanych stropowych belek i płyt żelbetowych. Opisano metody badań oraz wymagane próbki i urządzenia do przeprowadzenia badań.
EN
Testing requirements of steel trusses as a concrete reinforcement for floor slabs and floor joists according to standard PN-B-19503: 2004 are presented in this paper. Testing methods are described; needed specimens and testing equipment to carry out the test are specified.
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