cable suspended bridge

[DPS]

You don't want to work there, trust me.

[Ed_Hobbick]

I tried to erase that post after I sent it but is was too late. I suppose I could/should have modified it.

 

I have a lot of respect for engineers, sometimes wish I was one.

 

To engineers, What kind of a systems would you recommend in this case?

 

What do you see as most likely to result in failure?

 

Is it the bridge that might buck someone off or is something likely to break?

Edited September 22, 2011 by Ed_Hobbick

[sobo]

You don't want to work there, trust me.

Working there would beat the alternative, no?

[ivan]

This duty can be traced all the way back to Babylon, in the Code of Hammurabi.

nice, one of my favorites from the code: build a dam and it breaks => become a slave

 

would have been an interesting consequence after the challenger blew up?

[num1mc]

I call bullshit on this one. Unless DPS has a source, I think this is a grossly exaggerated urban myth.

 

From the USGS: http://pubs.usgs.gov/of/1998/ofr-98-239/ofr-98-239.html

 

"The Bainbridge Island landslide at Rolling Bay Walk is about three houses north of one that was pushed off its foundation on April 23, 1996 (#20, plate1.html; fig. 2). The landslide scar, deposits, and overturned house were still intact at the time of our observations, except for the disturbance caused by recovery operations. The scar of the slide was about 15 m wide, 15-20 m high, and averages 1 m deep. News reports indicated that the owner had built a retaining wall of unknown quality and design (Maier, 1997; Crist, 1997). Newspapers and a local resident indicated that the landslide happened shortly before 8:00 a.m., Sunday, January 19, 1997 (Maier 1997). A neighbor stated that the landslide lasted only a few seconds (Bjorhus and Tu, 1997). The row of houses appear to be constructed in a cut at the base of a steep bluff that rises from a narrow beach area. We observed scars of many old landslides on the bluff to the north of the houses. About five recent slides from 1996 and 1997 storms were visible along undeveloped bluffs not far north of the houses. More slides occurred at Rolling Bay Walk on March 18 and 19, 1997; these slides damaged two houses and pushed another house onto the beach (Wallace, 1997).

 

The Oregonian: http://geography.uoregon.edu/mcdowell/geog322/newspaper_stories/seattle_area_mudslide_kills_family.htm

 

The Seattle Times: http://community.seattletimes.nwsource.com/archive/?date=19970120&slug=2519698

 

"The force of the slide flattened recently built retaining walls on the slope, officials said, pushing the house off its foundation and across a concrete walkway along the shore called Rolling Bay Walk. The two bottom floors of the house were buried in mud 8-feet deep in spots. Only the unfinished top floor of the house, which toppled on its side into the water, was visible."

 

 

 

 

My humble apologies. It is just sometimes people make claims which are based on things they heard, which are exagerated. You are correct about the fatal mass wastage event.

 

Again, I apologize

 

BTW, please explain the apple thing

 

[ivan]

I call bullshit on this one. Unless DPS has a source, I think this is a grossly exaggerated urban myth.

 

From the USGS: http://pubs.usgs.gov/of/1998/ofr-98-239/ofr-98-239.html

 

"The Bainbridge Island landslide at Rolling Bay Walk is about three houses north of one that was pushed off its foundation on April 23, 1996 (#20, plate1.html; fig. 2). The landslide scar, deposits, and overturned house were still intact at the time of our observations, except for the disturbance caused by recovery operations. The scar of the slide was about 15 m wide, 15-20 m high, and averages 1 m deep. News reports indicated that the owner had built a retaining wall of unknown quality and design (Maier, 1997; Crist, 1997). Newspapers and a local resident indicated that the landslide happened shortly before 8:00 a.m., Sunday, January 19, 1997 (Maier 1997). A neighbor stated that the landslide lasted only a few seconds (Bjorhus and Tu, 1997). The row of houses appear to be constructed in a cut at the base of a steep bluff that rises from a narrow beach area. We observed scars of many old landslides on the bluff to the north of the houses. About five recent slides from 1996 and 1997 storms were visible along undeveloped bluffs not far north of the houses. More slides occurred at Rolling Bay Walk on March 18 and 19, 1997; these slides damaged two houses and pushed another house onto the beach (Wallace, 1997).

 

The Oregonian: http://geography.uoregon.edu/mcdowell/geog322/newspaper_stories/seattle_area_mudslide_kills_family.htm

 

The Seattle Times: http://community.seattletimes.nwsource.com/archive/?date=19970120&slug=2519698

 

"The force of the slide flattened recently built retaining walls on the slope, officials said, pushing the house off its foundation and across a concrete walkway along the shore called Rolling Bay Walk. The two bottom floors of the house were buried in mud 8-feet deep in spots. Only the unfinished top floor of the house, which toppled on its side into the water, was visible."

 

 

 

 

My humble apologies. It is just sometimes people make claims which are based on things they heard, which are exagerated. You are correct about the fatal mass wastage event.

 

Again, I apologize

 

BTW, please explain the apple thing

come on now! this is the internet! you're not allowed to be rational or humble!!!

 

apples => good will hunting. best line of movie: "let's go to haaavad and fawk up some smaat kids"

[RuMR]

I'm thinking that a guy could cut to the chase by talking to an Arborist and an Architect. The engineers seem to get too anxious when it comes to actually building/doing.

 

I'll cut to the chase, that's sub-retard level idiocy

+1

[RuMR]

My wife is a bridge engineer (she built the new red bridge over the NF Snoqualmie on the way to Little/Mt Si). She said suspension bridges are a whole different ball of wax. Good luck.

 

Damn...we tried to get that bridge!! We did get the index bridge waaaay back when...

Didn't your firm and another (in a JV or partnership) win the D/B of the new Tacoma Narrows Bridge? I'd say that's a true winner and quite a prestigious grab...

Yah!! that job was one to retire on! I worked on the cutting edges for the caissons, the caissons themselves, the orthotropic deck and the cable saddles...Sometimes my job sucks but there are moments that leave me speechless!

[sobo]

I tried to erase that post after I sent it but is was too late. I suppose I could/should have modified it.

 

I have a lot of respect for engineers, sometimes wish I was one.

Apology accepted.

 

To engineers, What kind of a systems would you recommend in this case?

Your basic "catwalk" would be ideal in this case. What is commonly referred to as a "Burma Bridge", as the OP stated on Page 1 of this thread. It is technically referred to as the negative camber catenary suspended bridge. See Indiana Jones and the Temple of Doom for the classic Hollywood example. Or the Capilano Suspension Bridge, from waterboy49's link on Page 1 of this thread, for a more modern contribution to the genre.

 

What do you see as most likely to result in failure?

If proper selection is made, it wouldn't be the cables. More likely it would be the anchorages. They have the most unknowns and therefore would require the most study.

 

Is it the bridge that might buck someone off or is something likely to break?

If high winds are a concern, just close the bridge/treehouse until more favorable conditions prevail. If all is engineered rigorously (connections, anchorages, etc.) and materials selected properly (cables, slats, suspenders, etc.), then there is no reason to anticipate a failure, assuming proper O&M. Take the Capilano bridge as an example - the bridge has never failed as a result of its engineering. It has been in operation for over 120 years. As I like to remind my clients, "There's no substitute for good engineering."

[sobo]

My wife is a bridge engineer (she built the new red bridge over the NF Snoqualmie on the way to Little/Mt Si). She said suspension bridges are a whole different ball of wax. Good luck.

 

Damn...we tried to get that bridge!! We did get the index bridge waaaay back when...

Didn't your firm and another (in a JV or partnership) win the D/B of the new Tacoma Narrows Bridge? I'd say that's a true winner and quite a prestigious grab...

Yah!! that job was one to retire on! I worked on the cutting edges for the caissons, the caissons themselves, the orthotropic deck and the cable saddles...Sometimes my job sucks but there are moments that leave me speechless!

Yah! So quit yer complainin'! Yeesh!

[sobo]

BTW, please explain the apple thing

As ivan has noted, it's from the 1997 film, Good Will Hunting.

 

There is a memorable scene where Matt Damon's character (Will Hunting) is challenged by Clark the College Puke (Scott William Winters, the guy on the left in the photo below) to acquire the phone number of a certain female student named Skylar (Minnie Driver), whom both The College Puke and Will Hunting are in competition for her attention. The Puke asserts that Will is of singularly low breeding, and that Skylar would never deign to release her digits to such a member of the proletariat as Will. By contrast, The Puke fancies himself as being from a much purer gene pool, and clearly he will emerge from the wager with Skylar's contact info.

 

Will locates Skylar, chats her up, and leaves their conversation with a scrap of paper upon which she has written her phone number. While walking down the street shortly thereafter, Will chances to spy The Puke enjoying a light repast in a local cafe. Will takes the paper upon which Skylar's digits are inscribed from his pocket, plasters it up against the window opposite The Puke's table, and shouts through the glass, "Do ya like apples!!??" Initially surprised, The Puke recovers quickly and replies churlishly, "Yeah.", in response to which Will utters the snappy rejoinder, "Well, I got her number. How'd'ya like them apples?"

 

Hence, the origin of DPS's comment.

 

[olyclimber]

well that wasn't exactly accurate:

 

http://en.wikipedia.org/wiki/How_do_you_like_them_apples

 

how do you like THEM apples?

[sobo]

OK, so it has a little more history than 1997. I'll give ya that...

But everybody remembers the line from GWH.

[JayB]

Would one of those flying-fox thingies that people use to cross bridges be feasible and/or any less technically demanding?

 

If it were me I'd probably just build the thing and add a separate static line and pulley system that would protect users in the even of a catastrophic failure.

 

BTW - what's a back of the envelope price for a bridge (design, construction, and materials) like Matt envisions that would satisfy all of the necessary engineering requirements? $20-30K? Seems like it could easily run triple the price of the said tree-house.

[sobo]

...BTW - what's a back of the envelope price for a bridge (design, construction, and materials) like Matt envisions that would satisfy all of the necessary engineering requirements? $20-30K? Seems like it could easily run triple the price of the said tree-house.

 

Difficult to quantify without having several variables known. We will firstly assume that an engineer competent in the field will be engaged to generate the design. Then...

1a. Will it be designed by the registered engineer acting professionally (that is, for a fee and the PE stamps/seals the design)?

1b. Or will it be designed by the registered engineer acting charitably (that is, pro bono and possibly no PE stamp/seal affixed)?

2a. Will plans and specifications be required (that is, for submittal to a regulatory and/or approving agency)?

2b. Or will it be built off "the back of an envelope" (that is, from some crude sketches/conceptual drawings)?

3. Will permitting costs be included?

4a. Will the labor be union and/or prevailing wage (that is, will this be built as a Public Works project)?

4b. Or will the labor be donated (that is, charitably by friends, benefactors, etc. a la Habitat For Humanity)?

5a. Will the materials be purchased by private citizens (that is, at Hope Depot, Lowes, etc.)?

5b. Or will the materials be purchased at a construction supply warehouse and at Contractor Price schedules?

5c. Or will the materials be donated by a local construction contractor (that is, say in exchange for publicity)?

6. Will the land upon which this project is to be constructed be purchased, or will it be donated?

 

Clearly, there are several unanswered questions, and surely more, that could add dramatically to the currently envisioned total project cost. For similar reasons, on every contract for engineering services that I write for my firm, I am required to have the following statement prominently displayed in the contract:

 

Opinions of Cost, Financial Considerations, and Schedules

In providing opinions of cost, financial analyses, and schedules for the project, ENGINEER has no control over cost or price of labor and materials; unknown or latent conditions of existing equipment or structures that may affect operation or maintenance costs; competitive bidding procedures and market conditions; time or quality of performance by operating personnel or third parties; and other economic and operational factors that may materially affect the ultimate project cost or schedule. Therefore, ENGINEER makes no warranty that CLIENT’s actual project costs, financial aspects, economic feasibility, or schedules will not vary from ENGINEER’s opinions, analyses, projections, or schedules.

 

Now that may seem like CYA to a lot of the people on this board, but you'd be hella surprised at the number of clients out there that think that once you estimate a project cost for them, it's cast in stone for the life of the project.

[JayB]

That's definitely useful information to think about.

 

Let's assume that Matt wanted to have the whole thing done by the books, he's paying out of pocket, and you'd have to attach you name to the project and assume whatever financial/professional liability came along with doing so?

 

Ravine on one side, big tree 80 feet away, and he wants a bridge made of suspended cables and slats to span the gap between the two. If impossible to guestimate based on that information, how about a ballpark figure that you'd give someone who called in over the phone, with the understanding that you wouldn't be able to give them a firm price until you saw the said tree and ravine.

[skykilo]

A fizzy cyst would just rig that shit with a buncha scrap layin' around the lab backyard. I just built like three death traps today! We got an engineer but he stays wayyyyyyyy busy and there's ample opportunity for DIYing.

[ivan]

A fizzy cyst would just rig that shit with a buncha scrap layin' around the lab backyard. I just built like three death traps today! We got an engineer but he stays wayyyyyyyy busy and there's ample opportunity for DIYing.

what's up w/ you fizzy cysts breaking einstein's laws today, eh?

[num1mc]

4a. Will the labor be union and/or prevailing wage (that is, will this be built as a Public Works project)?

4b. Or will the labor be donated (that is, charitably by friends, benefactors, etc. a la Habitat For Humanity)?

4c. Will labor be comprised of Merit Shops?

 

5a. Will the materials be purchased by private citizens (that is, at Hope Depot, Lowes, etc.)?

5b. Or will the materials be purchased at a construction supply warehouse and at Contractor Price schedules?

5c. Or will the materials be donated by a local construction contractor (that is, say in exchange for publicity)?

 

5b is the most likely. Suppliers would also be very reticent to donate such items as wire rope with the applicable cert's

 

Also: Will Special Inspections be required? It is nigh to impossible to expect to receive any type of deal on these services

 

Will an architect's services also be required?

[sobo]

Mark,

You add several salient points. Recognize that my list was not meant to be all-inclusive. Hence, the "and surely more" qualification in my post above.

[sobo]

That's definitely useful information to think about.

 

Let's assume that Matt wanted to have the whole thing done by the books, he's paying out of pocket, and you'd have to attach you name to the project and assume whatever financial/professional liability came along with doing so?

 

Ravine on one side, big tree 80 feet away, and he wants a bridge made of suspended cables and slats to span the gap between the two. If impossible to guestimate based on that information, how about a ballpark figure that you'd give someone who called in over the phone, with the understanding that you wouldn't be able to give them a firm price until you saw the said tree and ravine.

Given that scenario, and not quoting a "firm" price (as you stated), and me not being a structural engineer, I would tell Matt between $40k-$60k, and allow for a 30% contingency. Everything works back from there. And of course...

 

Opinions of Cost, Financial Considerations, and Schedules

In providing opinions of cost, financial analyses, and schedules for the project, SOBO has no control over cost or price of labor and materials; unknown or latent conditions of existing equipment or structures that may affect operation or maintenance costs; competitive bidding procedures and market conditions; time or quality of performance by operating personnel or third parties; and other economic and operational factors that may materially affect the ultimate project cost or schedule. Therefore, SOBO makes no warranty that MATT’s actual project costs, financial aspects, economic feasibility, or schedules will not vary from SOBO’s opinions, analyses, projections, or schedules.

[JosephH]

From one of the cooler threads on SuperTopo...

 

and

 

CABLE-SUSPENDED PEDESTRIAN BRIDGE DESIGN FOR RURAL CONSTRUCTION

 

 

[sobo]

CABLE-SUSPENDED PEDESTRIAN BRIDGE DESIGN FOR RURAL CONSTRUCTION

That was a pretty cool read. Thanks, Joe!