In steel bridges and constructions, the currently used assembling is made with common bolts and with connections with prestressed high strength bolts, to which prestressing forces are inserted in the rods after being mounted. This paper presents the mechanical behaviour of the connections made with flange-type end plates made with common bolts subjected to tension, respectively with high strength prestressed bolts, considering that the end plates have a very high stiffness or behave as flexible (semi-stiff) to rotation plates, when rotated in the vertical plane of the connection. The present paper presents briefly the arch steel bridge crossing the Some? river in the city of Cluj-Napoca, for which a feasibility study was made and where the cross girders were connected to the girder ties with end plates and cover plates welded to the tension upper flange. The calculation is performed for four constructive solutions and calculation hypotheses. It was found out that the constructive solution which is a hybrid connection of end plates joined together with non-preloaded bolts and a welded additional cover plate over the joint area in the elongated space of the flange can lead to a more uniform distribution of the stresses in the connection parts, the cover plate takes over a much larger stress in this case and the stresses in the bolts decrease significantly. The final part of the paper presents several conclusions and recommendations which are regarded by the authors are extremely useful in the design activity.
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