Alcan Structural Engineering

Division of moments between column and middle strips

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The design moments obtained from analysis of the frames or from Table 5.4 should be divided between the column and middle strips in the proportions given in Table 5.5.

Table 5.5 Distribution of design moments of flat slabs

Design moment

Column strip %

Middle strip %

Negative

Positive

Note

For the case where the width of column strip is taken as equal to that of the drop and the middle strip is thereby increased in width, the design moments to be resisted by the middle strip should be increased in proportion to its increased width. The design moments to be resisted by the column strip may be decreased by an amount such that the total positive and the total negative design moments resisted by the column strip and middle strip together are unchanged.

In general, moments will be able to be transferred only between a slab and an edge or corner column by a column strip considerably narrower than that appropriate for an internal panel. The breadth of this strip, be, for various typical cases is shown in Figure 5.3. be should not be taken as greater than the column strip width appropriate for an interior panel.

Note y is the distance from the face of the slab to the innermost face of the column.

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