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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 />

332 Beam analysis<br />

160 kNm<br />

1<br />

93.3 kN<br />

LA 4.Om 20m<br />

I-<br />

I 6.Om<br />

360 kN<br />

load<br />

]1320 kNm<br />

12667<br />

Fig. 10.6 Bending moment and shear force diagrams for fixed-end beam<br />

bending<br />

moment<br />

It will be seen that for symmetrical loads, where MA = MB, the reactions will be<br />

the same as for simply-supported beams.<br />

An example of bending moment and shear force diagrams for a built-in beam<br />

carrying a point load is given in Fig. 10.6.<br />

10.4 Continuous beams<br />

The solution of this type of beam consists, in the first instance, of the evaluation of<br />

the fixing or negative moments at the supports.<br />

The most general method is the use of Clapeyron’s Theorem of Three Moments.<br />

The theorem applies only to any two adjacent spans in a continuous beam and in<br />

its simplest form deals with a beam which has all the supports at the same level, and<br />

has a constant section throughout its length.<br />

The proof of the theorem results in the following expression:<br />

Ê A1 ¥ x1<br />

A2 ¥ x2ˆ<br />

MA ¥ L1+ 2MB( L1 + L2)+ MC ¥ L2<br />

= 6 +<br />

Ë L L ¯<br />

1<br />

2<br />

shear

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