STRENGTH REQUIREMENTS FOR ROUND CONDUIT 



743 



niiued by strain measurements and Equation (1) are compared in Fig. 4. 

 The agreement is very close. 



Fig. 5 shows the theoretical moment distribution in a thin-walled 

 tube subjected to a uniformly distributed vertical pressure; Fig. 6 is 

 the theoretical moment distribution in the same tube subjected to a 

 uniformly distributed vertical pressui'e at the top of the tube and a 

 point load at the bottom of the tube. 



Fig. 7 shows the typical experimental moment distribution in a thin- 

 walled tube in an 18-inch wide and 40-inch deep trench with a backfill 

 (36-inch cover) of moist Georgia clay subjected to an applied surface 

 load of 10,000 lb. Fig. 8 shows the moment distribution under the same 

 conditions but with a backfill of moist fine sand. 



F=IOLBS/lN = l20 LBS/FT 



E = IO X 10* PSI 



LOAD DISTRIBUTION 



lOr 



5-4 



z 



<D-6 



-8 



SR-4 STRAIN GAGES 



F= 10 LBS/IN = 120 LBS/FT 



MOMENT DISTRIBUTION 



M = -y(:^-SlNe)=ANALYTICAL MOMENT DISTRIBUTION = 



Mi = -g-h^E£i =EXPERIMENTAL MOMENT DlSTRlBUTlON=0 



Fig. 4 — Analytical and e.xperimental momoiit distrihiition in a thin-walled 

 tube under two-point load. 



