In this study, one of the fairly known practical plate problems was investigated experimentally, a square plate laterally loaded with single concentrated load at mid-span under all edges fixed. Clamping was made continuously along the edges with a small quantity of rotation. This type of clamping could be called as partially fixed. High-strength and ordinary concrete slabs containing steel wire fibers (volumetrically 0.5% and 1.0%) were constructed and tested. Load-deflection relationships were investigated. One of the objectives of this study was to investigate the effects of support rotations. Rotations of supports at corresponding load values were also measured. Ordinary concrete slabs support rotation values were recorded relatively close compared to high strength specimens. Mechanical properties of high-strength concrete and steel fibers were examined. Fracture patterns of plates were presented. Collapse occurred because of adherence loss in all slab specimens.