CONTINUOUS BEAMS 79 



To find R 2 , take a section through R s and consider all the loads on the left of the 

 section. Then the moment equation is 



, 



and inserting the value of R l just obtained, it is found that 



^s|tt 



By this method each reaction may be obtained in terms of those already found, 

 without calculating the shears. 



154. In problem 152 determine the shears and reactions at the supports and 

 check the results with the values tabulated on page 78. The tabular values are 

 the numerical coefficients of wl. 



155. An 18-in. steel I-beam, 601b./ft., is continuous over four supports, the 

 lengths of the three spans, beginning at the left, being 25ft., 40ft., and 35ft., 

 respectively. What -uniform load per foot run would produce a maximum fiber 

 stress in the beam of 16,000 lb./in. 2 ? 



