170 



MAXIMUM LIVE LOAD MOMENT. 



Art. 106. 



Fig. 127. 



For % > IT- I, a load in the 

 second span will, as before, 

 produce a minus moment; a 

 load in the first span may 

 produce either a plus or min- 

 us moment f depending upon 

 its location. If the location 

 of P, Fig. Ill, is found 

 which will produce zero mo- 

 ment at the section under 

 consideration, all loads to 

 the left of this load will evi- 

 dently produce a minus mo- 

 ment at the section, and all loads to the right, a plus moment; 

 the loadings, therefore, for the two maximum moments will be 

 as shown in Figs. 127 and 128. A single load at D, a distance k l 

 from the left support will give zero moment at a distance x from 

 this support. The value of k is given with Fig. Ill, for equal 

 spans. 



/ 



> 128. 



o 



X >) 

 I 



-nl 



Fig. 129. 



107. Maximum Live Load Moment in a Continuous Beam 

 of Three Spans. Only 

 points in the end spans, 

 which are of equal 

 length, will be consid- 

 ered. As shown by Fig. 

 112, any load in the 

 third span will produce 

 a positive moment at 

 any section of the first 

 span, arid any load in 

 the first span will pro- 

 duce a positive moment 

 in the first span at any 

 section to the left of the 

 point of contra-flexure. pi g> 139. 



