There were two examples of his designs for quickly constructed military bridges.
The first one clearly works, here it is
The second one seems to me not to work.
For reasons I cannot understand I did not photograph it, but here is a side view diagram:
The thick horizontal line is the bit where the soldiers walk;
the black vercal lines are pillars, and the red lines are ropes.
In the model the ropes were slack, but that suggests to me that the maker
of the model was better and woodcraft than engineering.
Here is a plan view:
I suggest that we look at the load carrying capacity of one or both of these.