# New Suspension Bridge Design **URL:** \ **Category:** Factual Questions\ **Created:** [December 28, 2002, 3:05am UTC](https://boards.straightdope.com/t/new-suspension-bridge-design/145289 "2002-12-28T03:05:31Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [December 28, 2002, 3:05am UTC](https://boards.straightdope.com/t/new-suspension-bridge-design/145289/1 "2002-12-28T03:05:31Z")
There’s a new trend in suspension bridge design. The supporting cables are run along the centerline of the bridge - instead of running along the sides. You may say this saves in materials, but why doesn’t the bridge sway (or oscillate) from side to side? And, doesn’t it require just the same amount of materials, if not more, to stop (dampen) the swaying…mostlikely by additional supports or trusses placed below the deck for added rigidity? Or, is it all done simply for asthetics, and screw the budgets and conventional engineering wisdom! Any civil engineers out there in Doperland? - Jinx ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [December 28, 2002, 3:08am UTC](https://boards.straightdope.com/t/new-suspension-bridge-design/145289/2 "2002-12-28T03:08:04Z")
The term for such bridges is “cable-stayed.” I have no answer to your OP, but using that term to clarify the distinction between “suspension bridges with cables at each side” and “suspension bridges with a cable along the centerline” seemed useful enough to make this post worthwhile. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [December 28, 2002, 3:30am UTC](https://boards.straightdope.com/t/new-suspension-bridge-design/145289/3 "2002-12-28T03:30:14Z")
[MODELING OF CABLE-STAYED BRIDGES FOR ANALYSIS OF TRAFFIC INDUCED VIBRATIONS](http://www.struct.kth.se/people/raid/IMACpaper.pdf) [Bridges](http://school.discovery.com/lessonplans/programs/bridges/answers.html) > [@](#): > > What are some of the advantages of cable-stayed bridges over other types of suspension bridges? > > Cable-stayed bridges use a series of diagonal cables attached to one or more towers to support the load of the bridge. Modern cable-stayed bridges usually require less material to build, may support a longer length between towers, and may require fewer towers to complete a span. They usually require less maintenance than other types of bridges. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [December 28, 2002, 6:26am UTC](https://boards.straightdope.com/t/new-suspension-bridge-design/145289/4 "2002-12-28T06:26:00Z")
There’s a [bridge](http://www.bigdig.com/thtml/gw_crc.htm#bridge1) going up in Boston that’s like this. The cables on the side spans attach to the deck at the center, while the center span is supported by cables attached along both edges. When I took a tour a few years ago, they said they would have preferred to support the side spans at the edges as well, except the existing elevated highway is in the way. (It’s on the far right in the picture linked above.) And that old road won’t be torn down until after the new one is finished. I don’t know if that’s the case with other cable-stayed bridges. It seems like the recent trend is to have the towers in an inverted “Y” shape, with the top of the cables above the centerline of the bridge. Angling the cables outward to the edges of the deck might present a clearance problem for tall trucks in the outermost lanes.