As
expected, the graph shows a nearly linear decrease in the load bearing
capacity for 
each of
the models with increasing span. The Warren IT model consistently
supported the 
greatest
load for a given span. The Warren RT model carried the least.
This is explained 
largely
by the fact that the Warren IT model had the highest H/S ratio and the
Warren RT 
the
lowest for the spans tested. This is shown in the following images
of the shortest spans 
tested
for each of these two structures. 
. 



Fig. 175  H/S ratios for 
Warren IT and RT 
truss models 


Warren IT  H/S = .66 
Warren RT  H/S = .25 


. 
The
relationship of the maximum load to the H/S ratio of these models is made
evident by 
the next
graph which compares them directly. 
. 

Fig.
176  Graph of maximum load vs. H/S ratio for Howe, Pratt, and Warren truss
models 
. 
The
increase in in load bearing capacity with an increase in the H/S ratio is
evident from 
the
graph. Note also that as their H/S ratios decrease the relative
differences in their load 
capacities diminish. The H/S ratios of the models decrease because
their spans increase 
. 
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Page 
109  Building stability  Comparing truss bridge models 

