Talk:Tied-arch bridge

examples?

• Fremont Bridge (Portland)
• Port Mann Bridge
• John McLoughlin Bridge
• Daniel Carter Beard Bridge
• Hoan Bridge
• Abraham Lincoln Memorial Bridge

bowstrings (are they technically tied arches also?)

• Fort Pitt Bridge
• Fort Duquesne Bridge
• Big Creek Bridge

Cacophony 21:24, 18 April 2006 (UTC)

Hi Cacophony! Bowstring is just another name for tied arch. The main idea is that the road deck is under tension and that it ties the ends of the arch together, eliminating horizontal forces at the foundations. The Fremont bridge is a great looking tied arch, but it is a more complicated example because of the two half arches at either end. I think it would be good to put a picture of a simpler tied arch (such as Fort Pitt) above Fremont, with captions explaining that both bridges are tied arches.

Also it would be good to place links back to this article from the many articles on tied arch bridges, such as those you mention.

Robshill 18:01, 20 April 2006 (UTC)

Done, properly sorted - Leonard G. 19:34, 11 September 2006 (UTC)

New longest span

The new Hastings, MN bridge over the Mississippi river will have:

The span is the longest tied arch bridge with a free-standing rib in the western hemisphere.
This is the structure that includes the 545-foot long, free-standing tied arches. 

See http://www.dot.state.mn.us/hastingsbridge/ Fholson 12:44, 24 September 2012 (UTC) — Preceding unsigned comment added by Fholson (talk • contribs)

Are the examples here correct?

The Torikai ohasi. the Fort Pitt Bridge and Windsor Railway Bridge are clearly tied arch. But the Lowry Avenue Bridge, the Hoan bridge and others look to be traditional arch bridge, with the deck just suspended, not put under tension by the arch. Should these be removed? 82.10.224.23 (talk) 06:42, 9 January 2014 (UTC)

Braunstone Gate Bridge looks to be a truss bridge. Any objections if I were to remove it? — Preceding unsigned comment added by 82.10.224.23 (talk) 07:13, 9 January 2014 (UTC)

Final objections before these are deleted? Instead of removing, I'll put them under the Arch Bridge page. Chumpih (talk) 05:21, 9 March 2014 (UTC)

Don't just delete the pictures based on looks. Do some checking first. For example, the Lowry Ave. Bridge designer says it is a tied arch. See Lowry Avenue Bridge in Minneapolis Opens to Traffic. The piers supporting the Hoan and Lowry Ave. bridges don't look massive enough to withstand the thrust from conventional arches.

Due to the flat bottom chord, I agree that the Braunstone Gate Bridge is not an arch at all.--Triskele Jim 17:09, 11 March 2014 (UTC)

It's very difficult to tell a bridge from a photo anyway, without knowing just how much load each member is carrying. A tied arch is carrying weight on the arch, a truss is sharing it between arch and tie. Unless you've a Perspex bridge in polarised light, I can't tell just by looking.

• File:Pennybacker bridge.jpg – simple arch. Might have some relevance on the page as a counter-example (possibly), but not just lost in a gallery.
• File:Hoan Bridge.jpg – a through deck balanced arch, not a simple tied arch. The spans outboard of the piers balance the thrust on the feet of the arch. The central arch thus doesn't need to be tied. Is it a tied arch though? Hard to tell without seeing the anchors of the outboard spans. Are they earth anchored (probably on valley sides), or are they tied by a long decking? Either type is used. Needs clarification though, because the feet of that central arch aren't tied.
• File:FortPittBridge.jpg – "Note that the arches terminate atop slender raised piers, which provide no squeezing force; tension in the road deck holds up the arch." Yes, that's the point of a tied arch. Why restate it here?
• File:Blackfriars_Street_Bridge_from_south_riverbed,_fall_2007.jpg – I don't even recognise this bridge. Doesn't look like cast iron and it looks more like a bowstring truss than a tied arch.
• File:Leicester-Bowstring-bridge.png is of course a Pratt truss.
• File:Archbridgegodavari.JPG – no idea. Poor photo too. The small bearing pads under the arch ends suggest a tied arch or truss, but it could be anything.
• File:Blue Water Bridge.jpg – see Hoan Bridge. This is the balanced type, but because it appears to be elevated, the likelihood is that the ends of the outboard spans are tied, not anchored, and thus it belongs here (if properly explained).
• File:Champlain Bridge (United States) New Panorama 28July2011.jpg – no idea. They haven't even finished building it yet. The spans that are complete and visible look like box beams, not any sort of arch. Besides the image only being a couple of pixels high.
• File:Lleida GFRP Pedestrian bridge.jpg – given the comparable sizes of the two members, the civil engineer wasn't doing their job if the load isn't shared fairly evenly between the two of them, i.e. it's a truss rather than a tied arch.
• File:Torun budowa mostu Zawackiej 2013-05-20.jpg – Again, it's incomplete. Those arches look ground anchored as simple arches, not tied (and certainly not tied yet, which makes it misleading at present).

Overall, I'd nuke the lot. This is an encyclopedia and so (IMHO) galleries rarely belong in encyclopedias, as they are merely decorative collections of unexplained eye candy. In an article like this, we're trying to explain different design aspects. We should explain each of these, with relevant images as needed, and not confuse readers with this sort of rag bag gallery. Some of these also look far too much like the usual, "I love my local bridge and my teacher said to add a photo to Wikipedia". So definitely nuke the errors (most of them), move the outliers (Hoan and Blue Water) to thumbed images and make sure they're specifically explained, and IMHO, nuke the gallery altogether. Andy Dingley (talk) 18:21, 11 March 2014 (UTC)

Stupidities like Bowstring truss being a redirect to Tied-arch bridge don't help either. Andy Dingley (talk) 18:23, 11 March 2014 (UTC)

I've replaced the pic of the Lake Champlain Bridge with one of the completed structure. A construction pic showing the Champlain bridge while they were lifting the arch into place could be useful, since it would show the arch does not need external thrust restraint. Here's a time-lapse video.

If you think the gallery needs serious weeding or re-writing, go ahead. --Triskele Jim 20:06, 11 March 2014 (UTC)

Construction isn't compelling evidence for how it operates in service. Many arches can be lifted into place (as simple beams) because they aren't yet carrying the load of their decks. Sometimes there is also a temporary tie added for support during construction, then removed and replaced by a stronger and heaver one. I think Chepstow Railway Bridge was the first to use this. Andy Dingley (talk) 21:57, 11 March 2014 (UTC)