While all the action on a train trestle may have occurred atop the rail deck and attached girders (the trestles superstructure), the real work occurred down on the valley’s floor, where the bridge’s compliment of steel piers (the sub structure) worked to hold the train and its cargo high above the river’s waters. The secret of it all was a series of girders and trusses that worked to transfer the engine’s weight (along with its compliment of rolling stock) down to a series of concrete footings that actually held up the bridge.
Each of the bridge’s steel piers rested atop a grouping of four concrete footings, one footing for each of the pier’s four main “legs”. To resist lateral movement of the bridge from wind, the footings are not set directly under the rail bridge but our sprawled outward a dozen or so feet.
Here’s a closer look at the base of one of the trestle’s piers. This area of the valley floor was pretty wet, and would normally be covered in a rather thick layer of underbrush. Thankfully we visited the site in early spring, and the foliage had not yet taken root. I would guess that this area got flooded quiet often, especially during spring run off.
Here’s a closer look at one of those concrete piers, which consists of a large concrete block and several thin iron plates which were probably added to help level the structure. Sitting atop those plates is a large flange in which the iron beam “leg” is attached by means of a pair of iron bolts.
Here’s another footing, this one even more robust then the first.
Amazingly its only a pair of these bolts that seem to be holding the iron “legs” down to the concrete footings. I suppose the weight of the structure is adequate in holding the leg in place, and those bolts are only to resist sheering forces.
Above those foots is the first joining point at which the “legs” are joined to the rigid frame of the truss work.
Instead of the large iron “I” beams used on the piers “legs”, that truss work consists of much lighter steelwork utilizing thiner side beams and several cross ties.
Midway down those framing criss crossed beams is another vertical member that joins up with the more truss work above. Its another thin beam, utilizing similar cross ties.
One last detail not to be missed, but only faintly noted along the trestle’s many iron beams and trusses. A single name stamped into the metal, a name of the company responsible for this bridge and its two siblings down the line. The name is Phoenix and it refers to the Phoenix Bridge Company out of Phoenixville Pennsylvania. The Phoenix Bridge Co. operated from around 1869 to 1964, during which time it built more than four thousand bridges all across the country. The company’s primary trade was in “pre-fab” train trestles, where bridges of a particular style could be bought from the company’s catalogue and installed quickly on site using pre fabricated beams and girders. But the company was most famous for its role in the construction of New York’s Manhattan Bridge, built in 1909. Only further proof that the Copper Country was once an integral part of the nations industrial fabric, a role it hasn’t played in quite some time.
But at least these trestles remain to remind us…