Abstract:
Lateral load tests of reinforced concrete perimeter frame with diaphragm have shown that the addition of a floor slab ( diaphragm) can have a major influence on structural performance. Three moment resisting frames were tested. Two of these frames were tested without a floor slab being attached to the beams, while the remaining frame was tested with the addition of a typical floor slab containing prestressed units. The tests showed that the addition of the floor slab increased the strength of the beams appreciably and as a result the lateral strength of the frame was increased by close to 80%. Clearly a strength increase of this order of magnitude is of major concern in seismic design in cases where it is essential to avoid the premature formation of a column sway mechanism. The test results presented together with an analytical study show the origins of this strength increase. Understanding these mechanisms is a first step in establishing a design method for assessing over-strength values in perimeter frames, which contain floors with prestressed units.