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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