When it went wrong on the old Corbin truss bridge.
Since the first log fell across water people have been fascinated with bridges and their power to bring together what has been separate. I, naturally, am one of those people. Love bridges, love hanging out on them. Especially railway bridges when the train is coming!
The recent work being done to redo the Alexander Creek Bridge just past the weigh scales at the border has had traffic pretty jammed up these last few months. It brought back memories of the systematic replacement of the old truss deck bridges throughout the Elk Valley years ago. If you recall there were two at each end of Fernie, one at Sparwood and Hosmer, one over Michel Creek on the south side of the Michel Creek valley and one just before the Corbin turnoff. All were narrow and dangerous and God help you if you lost control while on it.
The west side Fernie Bridge, however small in the world of spans, was nevertheless still a significant structure for its community. Its construction style was known as a Pratt Truss Deck Bridge and it has stood until 1999 on the same spot for over 50 years, spanning the Elk River for Highway 3.
It struck me that it might be interesting to try to explain in layman’s terms just how this type of bridge can span the distance it does and carry the weight it does unsupported. Unfortunately once I had waded (more like staggered) through the textbook descriptions of live load stresses, maximum bending moments, applied forces, compressive strength tables and shear resistance diagrams I found that there was no easy way to do so. Not that I grasped it all but suffice it to say that live loads (us) and dead loads (our cars) on the bridge are transferred successfully through the bridge’s system of beams and into its abutments at either end.
On a moonlit night back in July of 1999 60 ton jacks, winches, pulleys and a good amount of grease were used to move all 800 tons of that West Fernie Bridge slightly downstream to make room for a new span.
The last time the west side span was moved was in 1948 but in that year it went up instead of sideways. That was the year of its original construction and also the year of the famous flood of ‘48. That flood occurred just as the new East and West Fernie bridges were under construction. The rivet crews apparently became alarmed that late Monday in May when the fast rising Elk River came close to lapping at the new bridge’s floor level. Permission was then sought from the Provincial Public Works Department in the bridgeless land of Victoria to raise the new span four feet. This it was felt would eliminate any future high waters jamming debris against the bridge. I can’t recall the ‘95 flood’s high mark near the bridge but I’m bettin’ that if you lowered the bridge four feet it would have been awful dam close.
The Dominion Bridge crews back then were no slouches and both east and west Fernie bridges were erected in exactly 3 weeks, unlike the latest effort at the Alexander which is probably going to go on forever.
It seems my great grandfather (of same name) worked on a bridge in Scotland which was at the time (1890) the largest steel cantilever bridge in the world. This marvelous railway span allowed the Flying Scotsman steam train to go from Edinburgh to Dundee and is still in use today. It is known as the Firth of Forth bridge, a mile and a half of blood, sweat and steel. It was finished the year after Gustave Eiffel had completed his Parisian tower and stands as a pure structure, enduring as a work of art and a symbol of man’s mastery over the power of the wind.
Why wind? Well, because in 1878 a precursor to the Forth bridge built over the Tay river was built only to collapse a year later due to its inability to resist gale force winds on Scotland’s east coast. It took 70 people in a train with it and forced a rethinking of wind pressure resistance and structural design. The Forth cantilever has ancient Asian origins combined with more modern construction materials (i.e. steel). A series of rigid beams 12 feet in diameter projects from a base kind of like branches from a tree to support a central span. The middle cantilever was built on a mid-river estuary island called Inchgarvie. The three cantilevers were connected by two suspended girder spans, each 350 feet long.
The story goes from great grandpa that the cantilever sections were connected to each other ever so slowly, bay by bay. The last act was to connect each one to the other with giant gusset plates full of holes for rivets and high tension bolts. The Forth bridge easily expands over six feet due to temperature changes and on the connection day they patiently waited for the final gusset plates to align as the sun climbed in the sky.
Once lined up riveters and bolters furiously attacked the plates but nature (i.e. a cloud passing over the sun) intervened which resulted in a cooling contraction that sent rivets and riveters flying in every direction.
Eventually Forth bridge was completed and the story goes that there are two cottages at either end of the bridge whose families have a lifetime job. That job is to continuously scrape sand and paint the amazing Firth of Forth bridge.
I have one more bridge story for you, one that is a little more sobering than the first. It came to mind as I listened to the pile drivers dull thunk while waiting on traffic at the Alexander. It is the story of my older brother Alex who at one time worked with an Alberta bridge construction crew in the late 1950’s. Pile driving in his day was with mostly wooden posts and to keep these river piles from splitting it was his job to stand next to them and wrap a coil of manila rope onto their tops to keep the pile driver’s impact from splitting the timber. A green operator and an innocent slip led to a devastating accident that crushed his hand and led to the loss of most of two fingers on his left hand. It ended his career as a bridge builder and also as an ardent “bag piper”. The loss of most of his two middle fingers on his left hand made it impossible for him to effectively cover the chanter holes on his pipes.
The upside of this story was that a brilliant surgeon in Cardston rebuilt my brother’s hand and encouraged him during some very extensive physiotherapy to practice his piano skills thereby toughening his abbreviated digits and refining his already fine playing ability.
It was a turning point in his life as his chording hand was left unimpeded by those rarely used fingers. Anyone who ever heard this young coal miner many years ago, with his white shirt sleeves rolled up, pound out a super fast Bushtown polka at the local legions would know how this accident became a blessing.