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Steel Designers Manual - TheBestFriend.org

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This material is copyright - all rights reserved. Reproduced under licence from The <strong>Steel</strong> Construction Institute on 12/2/2007<br />

To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.<strong>org</strong>/<br />

<strong>Steel</strong> <strong>Designers</strong>' <strong>Manual</strong> - 6th Edition (2003)<br />

1L<br />

I I I I I<br />

(a)<br />

BL,<br />

IA4-<br />

(b)<br />

328 Beam analysis<br />

(c)<br />

-±<br />

4RB<br />

pIIIUUWWI<br />

(a) + (c) (a) + (b)<br />

Fig. 10.2 Bending moment diagram for propped cantilever with sinking support<br />

10.3.1 Beams with supports at the same level<br />

The two conditions for solution, derived by Mohr, are:<br />

(1) the area of the fixing or negative BM diagram is equal to that of the free or<br />

positive BM diagram<br />

(2) the centres of gravity of the two diagrams lie in the same vertical line, i.e. are<br />

equidistant from a given end of the beam.<br />

Figure 10.3 shows a typical BM diagram for a built-in beam.<br />

ACDB is the diagram of the free moment Ms and the trapezium AEFB is the<br />

diagram of the fixing moment Mi, the portions shaded representing the final<br />

diagram.<br />

Let As = the area of the free BM diagram<br />

and Ai = the area of the fixing moment diagram.

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