Abstract
Plate bridges with encased beams are suitable for building bridges of short and medium range. The paper presented focuses on the research into progressive bridges with encased filler beams of modified steel sections designed to minimize steel consumption without affecting essentially the overall structure resistance. This type of construction is suitable for bridges over short and middle spans as it offers a number of advantages, such as little headroom, quite clear static action of forces and a short construction period with no falsework required. Among some disadvantages is the economic inefficiency of steel I-sections, which are employed in the majority of bridges of this type. Therefore, there is an urgent need for the development of more economical design approaches and more purposeful arrangement and employment of steel beams. The paper presented brings some results from experimental tests on elements with encased steel filler-beams acting compositely under both short-term static and dynamic loads, and long-term load.