Steel arch-rectangular support has a wide range of applications in Polish coal mines due to its asymmetrical shape. The frame has an arched outline on one side of the side wall, while on the opposite side it is rectangular. As a result, the support is ideal for securing set up room and recovery room. It can also be successfully used to secure three-way intersections of underground workings. To a large extent, however, the importance of these advantages is diminished by relatively low load-bearing parameters, resulting from a partially straight canopy, as well as the asymmetrical distribution of the load acting on the support in underground conditions. In order to ensure the proper and optimal operation of such frames, in addition to the standard requirements for roof supports, additional conditions must be met. The basic requirement is to support the end of the canopy on the corner of the excavation. This article presents examples of arch-rectangular supports, their applications as well as laboratory tests and strength analysis of the frames and its elements. These tests allowed the requirements regarding the construction of the frame, the selection of the support and the conditions of building in the excavation to be specified.
This paper presents an estimation of performances by tests on composite material structures. In order to evaluate the effects on the structural behavior, tests changing the percentage of orientation of the fiber at 0, 45 and 90 degrees and mixing the unidirectional plies with the fabric ones have been done. Fixed the lay-up configuration and so the stacking sequence, two typology of structures have been analyzed; the first one having only unidirectional plies while the second one having a fabric ply (plain weave 0/90) in place of the top and bottom unidirectional plies. The openhole compressive strength and the filled-hole tensile strength and moduli have been characterized by test. A total of 72 specimens have been used in the test campaign. In order to well compare the test results a Performance Weight Index (PWI) has been introduced by authors in order to normalize the strength of each laminate with respect to its weight/unit of surface. Results and different laminate behaviors have been evaluated and discussed.