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

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