Not sure how many coastal Maine/NH/MA users there are here, but thought this might be interesting some. We have quite the little local project going on.

http://www.seacoastonline.com/articl...NEWS-203280365

PORTSMOUTH - The new Memorial Bridge will be the first gussetless truss bridge in the world, the first to incorporate cold bending of steel, the first to tuck its machine rooms underneath the bridge.

And it may well be gray instead of green, because a coating of zinc will make it last longer. Perhaps, too, it might be viewed as in keeping with the ship-building tradition of the Portsmouth Naval Shipyard.

All of these innovations and the attention to detail come from the mind of the bridge's designer, Theodore Zoli, national chief bridge engineer for HNTB Inc.

Zoli knows his bridges. He designed the Leonard P. Zakim Bunker Hill Memorial Bridge in Boston and the Lake Champlain Bridge between New York and Vermont, and he is the first structural engineer to win a MacArthur Foundation Genius Award. He is using the grant money to design a lightweight portable bridge and a lightweight shelter.

When his design/build team responded to a request for proposals from the New Hampshire Department of Transportation for Memorial Bridge, he said he knew this design was going to call for something different.

"I knew we needed to depart from the structural design of the truss bridge," Zoli said. "Sometimes, my students say my course demonizes the truss because they're not safe enough. Part of what I was thinking about was: 'How can we make structural systems that are safer?'"

The problem with trusses are the gussets, the point at which several steel beams are joined by plates on either side, kept in place with steel bolts. As gusset plates rust, as was the case with the current Memorial Bridge, they compromise the strength of all the separate pieces.

When the Interstate 35 truss bridge in Minneapolis, Minn., collapsed in 2007, Zoli said, it was determined that the gusset plate design was part of the problem.

Zoli's Memorial Bridge design eliminates gusset plates entirely. Instead, the metal sections are all uniform in size so they fit together like puzzle pieces, through a process called splicing.


"The idea is that, if I want to make the best connection I can from one member to the next, if they're exactly the same shape, I can splice them together," he said.

Each section is spliced in what he called a "sandwich," with the sections fitting in place and then sandwiched between two plates on either side to hold them.

"Those connections perform beautifully — much better than gusset plates," he said.

To make those sections uniform, Zoli came up with another innovation — cold-bent steel. In most truss bridges, individual steel beams are used; in Memorial Bridge, 65-foot curved sections are being fabricated.

"What we realized is, if we bent the plates to a fairly large radius, a fairly gentle bend, we can use cold bending," he said. The Memorial Bridge will be the first that incorporates cold-bent plates, he added.

But importantly, Zoli said, cold-bending of steel was developed many years ago by the U.S. Navy in its construction of submarines. "That's not lost on me," he said, with the shipyard in plain view of the bridge.

Meanwhile, Zoli said the designer of the original Memorial Bridge, John Alexander Waddell, is never far from his mind — nor is the Seacoast.

"The Memorial Bridge was an incredibly important work in the history of bridge engineering. It made international news when it was built," he said. "It was one of the most important structures of that decade and set a number of precedents."

Zoli said he looked at what Waddell did in designing Memorial Bridge and "innovated in a similar way, but using a different strategy."


As for the gray color, it's actually a zinc coating. He said each piece of the bridge will be dipped in zinc at the fabricator, Structal Bridges in Claremont. Zinc, he said, "provides the highest protection from corrosion."

The design/build contract calls for four layers of paint to be used and not zinc, which is more expensive. Under the contract, the end result would be a green bridge, but one that will not last as long, Zoli said.

"The problem with zinc is, it's gray," he said.

Keith Cota, project manager with the N.H. DOT, said the state and Archer Western Contractors are currently in negotiations about which coating to use.

But Zoli said a gray bridge could actually be viewed as historically important for the Seacoast.

"To me, the remarkable part of that region, and its importance in American history, is its shipbuilding for the Navy," he said. "I don't think gray is an inappropriate color for such a community. If it makes sense anywhere, it makes sense there."

go with the galvinizeing it will last alot longer

Cool.

Every time i go over one of those i wonder if a gusset is gonna give way . . . . . glad they got that sorted out











thanks for posting, wish they had some closer detailed pics i like this kinda stuff.

It that the route 1 bridge that drops you into the rotary in downtown portsmouth.

No, that is the Long Bridge (Sara Mildred Long) which is due up next for some work. This is the bridge that puts you right downtown Portsmouth. Close to the Portsmouth shipyard.

Yes this is the bridge that connects you with the rotary, crosses Badger Island to Kittery.

The disassembly of the old bridge is well underway.

My mistake. I read rotary and always think of the traffic circle and the Rte 1 bypass bridge.

[QUOTE=glassdave;3651674]Every time i go over one of those i wonder if a gusset is gonna give way . . . . . glad they got that sorted out

Dave not to worry ,No gussets here,Only sandwich joints and plates.

Hi!
Are you sure?
In Poland we have them since 2011.
I cannot post an url address, but you may search in the web for:
polska-org.pl/foto/3237/Wiadukt_kolejowy_Malczyce_LK_302_LK_275_3237216.jp g
(keep the "jpg" together)
Regards.