Equivalent wall for frameworks; Buckling analysis of planar structures - Global Structural Analysis of Buildings - page 214

where K, N l and r are defined by formulae (9.11), (9.2) and (9.12), respectively. Critical
load parameters α p and α S are given in Tables 9.3 and 9.3 as a function of stiffness

β S , defined by formulae (9.18) and (9.23).
It should be borne in mind when the full-height bending critical loads N l and N g are
calculated that with frameworks with ground floor beams the uniformly distributed
axial load on the equivalent column does not represent an approximation and therefore
there is no need to reduce the part critical loads, i.e. r s =1.0 should be used in formulae
(9.2) and (9.6).
For frameworks under concentrated top load, both the continuum model and the
sandwich model result in the same formula for the critical load:

ratios β and

(9.36)

In formula (9.36) F g is the full-height bending critical load defined by
formula (9.7).

9.5 FRAMEWORKS WITH GROUND FLOOR COLUMNS OF
DIFFERENT HEIGHT

It is a practical case that the height of the columns on ground floor level is different
from those above the first floor level. In most cases, they are higher than the ones on
the other storey levels (Fig. 9.10/a/b/c) and therefore they create a more unfavourable
situation, as far as stability is concerned.

Fig. 9.10 Frameworks with ground floor columns of different height.