TRAINMAN2001: If the question is for my bridges the (beams/girders) whatever you call them are three pcs pressed together and then the bridges are bolted with 4-40 screws. Some holes are tapped and some are nuts and bolts. The 105 inch bridge has about 700 bolts in it and is an actual working bridge, that is to say without the arch and suspended rods the road bed would bow badly and probably just fall but as it is I had 3 - 25 pound bags of shot in the middle and it never sagged at all so I guess it will hold my trains .
This is what I bought for screws. I buy them 1000 at a time from bolt depot
you can see the slot in these pics how the beams fit together. the width of the slot has to be cut close so the center will press in just tight enough but still stay together
On the long bridge I had to join short pcs because l I had was scrape so I mad some doubler plates to cover the joint's
You can see them here on the 45 inch bridge
