Aces High Bulletin Board
General Forums => The O' Club => Topic started by: grizz441 on February 12, 2011, 02:02:01 PM
-
Thought this might be fun for some of you who like this kind of thing and for those who despise engineers to play engineer!
I am going to design a bridge (grad school project) out of either steel or prestressed concrete, and this is the proposed location for where the bridge is going to go. Cost effectiveness plays a big part. For example, when the piers get larger cost of them increases non linearly, however not as much cut will have to be made into existing terrain. Or on another token, the more piers you have, the smaller your girders will be however there will be additional cost for the added pier(s). Don't worry about this stuff when making a conceptual design. Lets just say it will be a 2 lane bridge.
Another thing to keep in mind: When you start exceeding ~35meters your girders start to get a lot more expensive quick. So dont just try a 150m girder across the bridge and say done. That won't work :)
Challenge To You guys: Come up with a conceptual design for your bridge. Where would you place your piers, girders, and consequentially your cut and fill? Lets call the bottom of bridge minimum at 187 m. I have a few ideas of my own. I will take the best ideas out of pool and run cost analysis on all and see which one will be the least expensive and most efficient.
(http://dasmuppets.com/public/Grizz/cross section.png)
(http://dasmuppets.com/public/Grizz/contour.png)
To get the ball rolling, here's the simplest design I sketched up rather quickly in paint. Two span simply supported prestressed conc girders with one pier. Girders will be huge. Two piers may be more efficient. Anyways here's to get the ball rolling.
(http://dasmuppets.com/public/Grizz/cross section design 1.png)
(http://dasmuppets.com/public/Grizz/contour1.png)
-
http://wootbymai.blogspot.com/2010/11/woot-multifunctional-futuristic-bridge.html
:)
-
Also a bit of fun. I have done all but one.
http://fantasticcontraption.com/index.php
-
Couple of questions
What is the prevailing code?
What state and county is this going in to?
What are the piers going in to or are you giving everybody a pass on figuring out how deep to embed the piers?
Are we talking freshwater or salt water?
Oh and can I play or am I dq'd?
Interesting project though since I don't do bridge design but I don't mind exercising my brain from time to time.
PS.. you know there's probably one or two guys besides yourself on this board that have the credentials to actually come up with a working design that would pass the code and stay at or below budget don't you? I ain't one of them.
-
What is the prevailing code?
AASHTO & ASCE
What state and county is this going in to?
Not specified.
What are the piers going in to or are you giving everybody a pass on figuring out how deep to embed the piers?
That's engineering. I'm giving a pass on worrying about that stuff.
Oh and can I play or am I dq'd?
You most certainly can play. Please post your design concept :)
PS.. you know there's probably one or two guys besides yourself on this board that have the credentials to actually come up with a working design that would pass the code and stay at or below budget don't you? I ain't one of them.
I don't have the credentials either, as I am not a bridge engineer. But I have a pretty good feeling on the feasibility of a concept as it relates to cost, and I will figure that all out once I decide on a design. Either way it's just a challenge to simply draw where your bridge will go and where the supports will be. Lets see em :)
-
I call it bridge. Tried not to get too caught up in technical terms.
(http://i91.photobucket.com/albums/k287/bagrat/bridge.png)
-
I call it bridge. Tried not to get too caught up in technical terms.
(http://i91.photobucket.com/albums/k287/bagrat/bridge.png)
Unfortunately I don't think that will work for two reasons:
1) Since you are essentially "damming" part of the river, you are increasing the rate of flow under the bridge which is dangerous for multiple reasons but in particular, scouring out your foundation.
2) Your extreme water level will actually rise and you will have to build the bridge higher.
It may be possible to fill in part of the edge with some of the cut on the right side, but it won't be possible at the degree in which you show. I will keep it in mind. Thx for the submittal. :aok
-
To bad there isn't an easier spot to build a bridge. Elevation changes from side to side are so different that there would be no "cheap" way of building a bridge. You need to find a different location!
DuHasst
-
(http://i603.photobucket.com/albums/tt118/phatzo/bridge-1.png)
-
well this is just something i thought of really quick after watching its construction back in 1997, its a hurried pic
(http://i148.photobucket.com/albums/s35/68zoom/cross20section.png)
It's a Cable-stayed bridge in a semi-fan arrangement, Prestressed Concrete Deck and towers after the Thea Foss waterway bridge, now not having the soil analysis, or general hardscape of the land makes it harder but another option would be an Arched similar to this one ( its just down the road)
(http://i148.photobucket.com/albums/s35/68zoom/arched.jpg)
-
(http://i603.photobucket.com/albums/tt118/phatzo/bridge-1.png)
I'm not opposed to the concept of a suspension bridge of course, but there would be no tunnel since the tunnel would have to be big enough to accomodate big trucks and by that point >12ft clearance you are already past the height of that hill. The way the picture is scaled is misleading. The y axis and x axis scales are completely different, so while your scale looks correct for the size of the tunnel based off the x axis, It's way off on the y axis since your tunnel is only about 3 feet high :)
I think the suspension bridge might be overkill for the 300 ft span and will be way too expensive but it is an option. Of course, I don't think I'd be able to design it which is another reason I might not want to do that. :)
-
Are you just trying to get us to write your paper for you. :D
-
Are you just trying to get us to write your paper for you. :D
:rofl
-
OK i redid mine little bit more to scale i think and the Cables are ran different to spread the load out through out the tower as apposed to my first drawing
(http://i148.photobucket.com/albums/s35/68zoom/crosssection-1.png)
-
Are you just trying to get us to write your paper for you. :D
:D
Nah just curious on different bridge configurations. This is the creativity phase of design. You don't have to be an engineer to envision how you want a bridge to look. This is just the first part of the project though, the actual work will be in cost analysis, and all rigorous design of the bridge itself. But before that can start I need to decide on the general stuff.
-
OK i redid mine little bit more to scale i think and the Cables are ran different to spread the load out through out the tower as apposed to my first drawing
(http://i148.photobucket.com/albums/s35/68zoom/crosssection.png)
That is a beautiful suspension bridge idea. :aok
-
Grizz alot of the Design of the Bridge depends on the area its going to be built in, is the Bridge going to be located in the country a trendy area of town or historical area and so on, i know when designing a home i take that in consideration, unless the person flipping the bill has a set design in mind
-
Just wait till all you guys see my "Bridge".
Everyones going to be envious of my talents as a designer.
-
The center span of the Mackinac bridge is ~1100 meters. Scale that down, with a tower and anchor at each end.
Since you can't go into a tunnel, just remove the fill.
Sorry I can't draw this up for you, I suck at that stuff.
-
Grizz alot of the Design of the Bridge depends on the area its going to be built in, is the Bridge going to be located in the country a trendy area of town or historical area and so on, i know when designing a home i take that in consideration, unless the person flipping the bill has a set design in mind
It's pretty open ended. Design will be governed purely by economy and the bridge satisfies aashto design. I don't think aesthetics will come into play much, although I don't think it should be ugly...
Idea 2:
(http://dasmuppets.com/public/Grizz/bridge section.jpg)
-
Zoom beat me to it. I was thinking suspension as well. Hmmmmmm... thinking
(http://img.photobucket.com/albums/v99/dichotomy/crosssection.jpg)
Okay Grizz this is totally off the top of my head and based on current economies as I understand them (I'd really prefer to run calcs on this stuff but don't have the tools here at the house)
I'd want to elevate the bridge a bit above the extreme range of the water just for safety's sake. I'm also assuming we're using the most current version of AASHTO with all the LTS's included (ASCE applies in lighting standards but it's my understanding that AASHTO meets or exceeds ASCE requirements).
Not being able to tell except visually I'd prefer to keep my piers equally spaced although the left side pier will, most likely, be larger od and embed depth. Primary material would be reinforced concrete as that is less expensive than steel (and oh boy is steel about to take a jump). I'm assuming decent soil conditions at the point of ingress / egress and haven't considered a foundation below the ramps for this reason.
Pass / Fail?
By the way if you have any interest at all in getting into the light pole business I have several licensed PE contacts and I'd be more than happy to introduce you to them.
-
2 things possible here grizz
1. we can give you a design for the bridge
2. why dont you use ur 109 n fly ppl across the gap, can make sum good money i bet.
-
The center span of the Mackinac bridge is ~1100 meters. Scale that down, with a tower and anchor at each end.
Since you can't go into a tunnel, just remove the fill.
Sorry I can't draw this up for you, I suck at that stuff.
I'll have to run some numbers but I would think that a suspension bridge would be more expensive than a traditional type of bridge at this span. I could be wrong.
-
Another factor of price thou is the ability to use your Cut from the Hillside as fill, it might not meet the Fed standards for compaction tests as far as your approaches go, then you'll have to factor in the cost of Importing Spec Fill to meet the requirements for that job, the cut either can be used else where on jobsite or trucked off, Dirt work was my living until my Injury
-
Another factor of price thou is the ability to use your Cut from the Hillside as fill, it might not meet the Fed standards for compaction tests as far as your approaches go, then you'll have to factor in the cost of Importing Spec Fill to meet the requirements for that job, the cut either can be used else where on jobsite or trucked off, Dirt work was my living until my Injury
For site work, to keep things simple and even for everyone, we are using $51/m^3 for site work. So I assume that means for cut and fill. It really simplifies having to worry about that stuff.
-
Zoom beat me to it. I was thinking suspension as well. Hmmmmmm... thinking
(http://img.photobucket.com/albums/v99/dichotomy/crosssection.jpg)
Okay Grizz this is totally off the top of my head and based on current economies as I understand them (I'd really prefer to run calcs on this stuff but don't have the tools here at the house)
I'd want to elevate the bridge a bit above the extreme range of the water just for safety's sake. I'm also assuming we're using the most current version of AASHTO with all the LTS's included (ASCE applies in lighting standards but it's my understanding that AASHTO meets or exceeds ASCE requirements).
Not being able to tell except visually I'd prefer to keep my piers equally spaced although the left side pier will, most likely, be larger od and embed depth. Primary material would be reinforced concrete as that is less expensive than steel (and oh boy is steel about to take a jump). I'm assuming decent soil conditions at the point of ingress / egress and haven't considered a foundation below the ramps for this reason.
Pass / Fail?
By the way if you have any interest at all in getting into the light pole business I have several licensed PE contacts and I'd be more than happy to introduce you to them.
Well it would have to be either prestressed precast concrete or post tensioned cast in place concrete. Reinforced concrete isn't really used much anymore for beams, typically only walls, piers, and foundations now. The arched girders won't be possible with concrete in that configuration, although that could be done with steel.
As for the equal span lengths, a couple things...
1. Dropping a pier down into the deepest part of river will require a larger cross section pier, since it will be more slender, and also more concrete.
2. I'm not sure how each span would connect at the piers. 3 span continuous maybe, I'll have to check if that is feasible.
-
Can't beat the old Through-truss. With two pillars, it should do fine with minimal girder strength at certain points.
-
:furious
Grizz now you have me thinking about this. You know how much I hate to think and I don't have my code books handy.
Actually thanks bro.. nice intellectual challenge.
-
:furious
Grizz now you have me thinking about this. You know how much I hate to think and I don't have my code books handy.
Actually thanks bro.. nice intellectual challenge.
I figured it would be fun for a lot of posters on here, there are some smart folks. We now await patiently for the sunbat p.e. to chime in. :rock
-
Can't beat the old Through-truss. With two pillars, it should do fine with minimal girder strength at certain points.
Yep, although imo steel truss bridges are rather ugly. :D
-
I figured it would be fun for a lot of posters on here, there are some smart folks. We now await patiently for the sunbat p.e. to chime in. :rock
Truth Grizz
I do want to hear what Sunbat has to say.
-
///////////////////////\
/ \
/ \
:::::::::::::::::::::::::::::::::::::::::::::::
""""""""""""""""""""""""""""""""""""""""""""""""""""""""
This should work
-
Do u have to worry about how this is going to be built or is it just theory?
-
Do u have to worry about how this is going to be built or is it just theory?
I have to worry about how the thing is going to be built.
-
Just fill the river up with a bunch of Grizz carcasses. They are hollow enough to allow the water to flow through but have heads big enough to support any weight necessary.
-
Just fill the river up with a bunch of Grizz carcasses. They are hollow enough to allow the water to flow through but have heads big enough to support any weight necessary.
Picture pls, I'm a visual learner.
-
Just fill the river up with a bunch of Grizz carcasses. They are hollow enough to allow the water to flow through but have heads big enough to support any weight necessary.
I just pee'd
-
Typical engineering or over engineered project... all about cost cutting and no safety or common sense concerns. :devil
:lol
-
Typical engineering or over engineered project... all about cost cutting and no safety or common sense concerns. :devil
:lol
Elaborate please. (If you can)
-
Dads, the design code establishes the level of safety of a structure, this has no bearing on safety, this is just attempting to come up with the most efficient design. You could design a bridge with the same level of safety as one that cost a million dollars less all based on how you did it. So deciding on pier locations, number of piers, material, type of bridge, are all important steps in determining the most economical way to design a bridge without compromising safety. They are not related because regardless of how you arrange your elements, they all must be designed to AASHTO design specification.
-
Idea 3:
(http://dasmuppets.com/public/Grizz/BRIDGE DESIGN2.jpg)
-
Idea 3:
(http://dasmuppets.com/public/Grizz/BRIDGE DESIGN2.jpg)
An arch could be very efficient but not like that.
-
An arch could be very efficient but not like that.
Explanation pls. :D
-
U have huge piers at both ends that are seeing very large shears at the top from the arch developing the compression it needs to be a good arch. This is inefficient because u have to design the piers to resist the shear from the arch and the shear also ptoduces a huge moment in the pier that will require a large footing or a deeper pier. Your banks can be natural buttresses that the ends of the arch could push into with much smaller foundations because they will be in pure compression.
Plus, you can make the arch smaller and use the banks with small abutments as supports at the end.
-
U have huge piers at both ends that are seeing very large shears at the top from the arch developing the compression it needs to be a good arch. This is inefficient because u have to design the piers to resist the shear from the arch and the shear also ptoduces a huge moment in the pier that will require a large footing or a deeper pier. Your banks can be natural buttresses that the ends of the arch could push into with much smaller foundations because they will be in pure compression.
Plus, you can make the arch smaller and use the banks with small abutments as supports at the end.
(http://dasmuppets.com/public/Grizz/BRIDGE DESIGN2a.jpg)
-
Yeah. Like that. However, if you are going to use battered piles (piles may not be needed) you may as well batter them in the direction of the load.
EDIT: You changed the picture. The first way was much better. Now your arch is taller than necessary.
-
Elaborate please. (If you can)
Relax, just jerking your chain.... hence the devil
Here in Hampton roads area they have several tunnels that go deep under water so that it does not interfere with shipping, very amazing since it has the harsh added element of salt water, not sure if your model depicts salt water or fresh, but my option would have been to construct a tunnel as to not interfere with shipping. :aok
-
Here is my bridge, I jsut took off and did this in 5-minutes. Sorry if it's similar to someone elses already.
(http://i675.photobucket.com/albums/vv115/Babalon84/AH%20Junk/BridgeCGB.png)
It's concrete (precast if possible, a lot cheaper than steel). Two things, particularly mindful of project cost, that I think you didn't address Grizz:
1) It's Cut & Fill. Most places these days it costs near a fortune to dispose of (or an arse-load of luck finding a happy taker of) fill/dirt. It is considered a cost-saving/VE/LEED/$$$$ goal of clients to not have to have to pay for any additional disposal, trucking/transportaion, associated fees, etc. when you can logicaly use 100% of any displaced dirt from any cutting. It's trading the cheaper cost of X-inches to build the bridge higher in exchange for the cost of not having to transport and dispose of Y amount of fill.
2) Pay mind where possible to build piers where water levels won't be during construction (cheaper), and also not to build them in the deepest parts of a river. I find my piers strike a good balance, wont be too big or expencive to construct, and also will allow for smaller/cheaper foundations for the bridge (I think in your basic design, they would need to be rather large foundations for the large spans).
-
Here is my bridge, I jsut took off and did this in 5-minutes. Sorry if it's similar to someone elses already.
(http://i675.photobucket.com/albums/vv115/Babalon84/AH%20Junk/BridgeCGB.png)
It's concrete (precast if possible, a lot cheaper than steel). Two things, particularly mindful of project cost, that I think you didn't address Grizz:
1) It's Cut & Fill. Most places these days it costs near a fortune to dispose of (or an arse-load of luck finding a happy taker of) fill/dirt. It is considered a cost-saving/VE/LEED/$$$$ goal of clients to not have to have to pay for any additional disposal, trucking/transportaion, associated fees, etc. when you can logicaly use 100% of any displaced dirt from any cutting. It's trading the cheaper cost of X-inches to build the bridge higher in exchange for the cost of not having to transport and dispose of Y amount of fill.
2) Pay mind where possible to build piers where water levels won't be during construction (cheaper), and also not to build them in the deepest parts of a river. I find my piers strike a good balance, wont be too big or expencive to construct, and also will allow for smaller/cheaper foundations for the bridge (I think in your basic design, they would need to be rather large foundations for the large spans).
Thanks Bab, I like that idea of a 4th pier also. That might be more cost efficient than 3 piers all things considered.
Zoom, phatzo, your ideas are much appreciated also and while they are scaled appropriately, I don't think they are cost efficient for this span length so I probably won't be looking more closely at them. Besides, I have barely any bridge experience as is and even less "innovative bridge design" experience so I'll probably have to stick to girder bridge.
-
Thanks Bab, I like that idea of a 4th pier also. That might be more cost efficient than 3 piers all things considered.
Zoom, phatzo, your ideas are much appreciated also and while they are scaled appropriately, I don't think they are cost efficient for this span length so I probably won't be looking more closely at them. Besides, I have barely any bridge experience as is and even less "innovative bridge design" experience so I'll probably have to stick to girder bridge.
If only every bridge designer/engineer in the world had an unlimited budget on every project..... sometimes ya get lucky though: http://en.wikipedia.org/wiki/Sundial_Bridge (gorgeous (and ingenious) bridge IMO though if ya ever get the chance to see or study it).
The Sundial Bridge is a cantilever spar cable-stayed bridge for bicycles and pedestrians that spans the Sacramento River in Redding, California, United States and forms a large sundial. It was designed by Santiago Calatrava and completed in 2004 at a cost of US$23,500,000. The bridge has become iconic for Redding
That's taxpayer money baby! (albeit one of the nicer uses of it)
(http://www.wayfaring.info/wp-content/uploads/2007/11/turtlebay01.jpg)
Day
(http://images.litwc.com/bridges/SunDial%20Bridge.jpg)
Night
(http://www.americantrails.org/i/resourceimages/Sundial3.jpg)
-
:O
AWESOME!!!!
-
Here ya go Grizz. Both of these are rather cheap and easy designs. Not much for city ascetics, but very functional. I'm more toward the second on as the lacking of post prevents river flow or river traffic for commerce.
First: Under truss design.
(http://i191.photobucket.com/albums/z235/nathanyoung1980/cross20section.jpg)
Second: Arch Design.
(http://i191.photobucket.com/albums/z235/nathanyoung1980/cross20section1.jpg)
-
(http://i58.photobucket.com/albums/g256/BloodyBandage/crosssection.png)
-
I'm thinking why even build a bridge. This would be allot more fun :noid
(http://i586.photobucket.com/albums/ss304/longhornsfan2010/cross20section1.png)
-
I was thinking the same thing, only taking more of a Wyle E. Coyote influenced design using catapults.
(http://img341.imageshack.us/img341/7368/crosssectiondesign1.png)
-
rpm and killer, I lol'd :lol
kilo I'm definitely going to look into that sloped crossing. It looks steeper than it is based on the scale differences.
5pointoh, that steel one is pretty similar to my layout but I think as far as girder bridges are concerned, prestressed concrete is cheaper and more efficient so I'm going to go with that. The arch bridge I'm going to stay away from due to more difficulty in analyzing it and also it will probably be less economical at that span.
Thx for the contributions though guys, I will keep you updated when I solve which girder bridge and with which pier arrangement will be cheapest of the ideas posted. :cheers:
-
:aok
Good thread Grizz...
A good Engineer and a good designer are always interested in looking at alternative ways to do things AND looking into areas that are not their primary discipline. This thread had me talking to a couple of my PE's this week and watermelon chatting about this and that.
-
It looks steeper than it is based on the scale differences.
If you adjust for scale (height/length) you can quickly figure out that any type of arched design is probably not suitable.
So, if you go by the cost, the cheapest would be three section pratt truss (or variation of thereof) steel bridge.
If you account for the maintenance, than two section (one center pylon) pre-stressed concrete balanced cantilever design would suit you perfectly (aesthetics).
-
Thought this might be fun for some of you who like this kind of thing and for those who despise engineers to play engineer!
I am going to design a bridge (grad school project) out of either steel or prestressed concrete, and this is the proposed location for where the bridge is going to go. Cost effectiveness plays a big part. For example, when the piers get larger cost of them increases non linearly, however not as much cut will have to be made into existing terrain. Or on another token, the more piers you have, the smaller your girders will be however there will be additional cost for the added pier(s). Don't worry about this stuff when making a conceptual design. Lets just say it will be a 2 lane bridge.
Another thing to keep in mind: When you start exceeding ~35meters your girders start to get a lot more expensive quick. So dont just try a 150m girder across the bridge and say done. That won't work :)
Challenge To You guys: Come up with a conceptual design for your bridge. Where would you place your piers, girders, and consequentially your cut and fill? Lets call the bottom of bridge minimum at 187 m. I have a few ideas of my own. I will take the best ideas out of pool and run cost analysis on all and see which one will be the least expensive and most efficient.
(http://dasmuppets.com/public/Grizz/cross section.png)
(http://dasmuppets.com/public/Grizz/contour.png)
To get the ball rolling, here's the simplest design I sketched up rather quickly in paint. Two span simply supported prestressed conc girders with one pier. Girders will be huge. Two piers may be more efficient. Anyways here's to get the ball rolling.
(http://dasmuppets.com/public/Grizz/cross section design 1.png)
(http://dasmuppets.com/public/Grizz/contour1.png)
Cool! I'm actually doing this in my Principles of Engineering class myself, but it isn't as defined as yours. We use a program called Westpoint Bridge Builder and we enter into a contest to see who can design the cheapest bridge that works.
-
If you adjust for scale (height/length) you can quickly figure out that any type of arched design is probably not suitable.
So, if you go by the cost, the cheapest would be three section pratt truss (or variation of thereof) steel bridge.
If you account for the maintenance, than two section (one center pylon) pre-stressed concrete balanced cantilever design would suit you perfectly (aesthetics).
How did you come up with that so fast? Do you have a spread sheet handy or something?
-
How did you come up with that so fast? Do you have a spread sheet handy or something?
Your whole chart is 23 ft in height, you have to over-bridge about 400 ft only, and cost is concern. Not many options left, are they?
-
How do you know a steel truss is cheaper than prestressed girders?
-
How do you know a steel truss is cheaper than prestressed girders?
It's structurally more efficient and design is cheaper at these lengths. As for the economical efficiency for the lifespan of the bridge, I don't know. That depends on many factors.
-
(http://i173.photobucket.com/albums/w63/jager515/cross20sectionwithcat.png)
I know it was supposed to be at 187m, but the giant cat keeps drinking all the water.
-
It's structurally more efficient and design is cheaper at these lengths. As for the economical efficiency for the lifespan of the bridge, I don't know. That depends on many factors.
That's contrary to all I've read and been told. Anything from 100-150ft spans I've heard that prestressed dominates.
-
That's contrary to all I've read and been told. Anything from 100-150ft spans I've heard that prestressed dominates.
Steel bridges were always and still are, structurally more efficient at all but shortest spans. That's why they build so many. Of course, they used to have many disadvantages and limitations as well (fabrication, lifespan, maintenance, environmental impact, aesthetics, etc), although with technology advances that is changing too.
Remember I'm not talking about life-cycle economics here, which (today) isn't so clear cut as it has been in the past.
-
Wish I had gotten here sooner. Most of the good ideas have already been pitched, including the giant cat idea.
I dated a girl who went to VA Tech and was part of the steel bridge team. There were some very interesting ideas that I got to see.
Here is a beautiful one near me.
2300ft span :O
(http://i239.photobucket.com/albums/ff107/tymekeepyr/tr_nicholson.jpg)
-
(http://i58.photobucket.com/albums/g256/BloodyBandage/crosssection.png)
rpm and killer, I lol'd :lol
kilo I'm definitely going to look into that sloped crossing. It looks steeper than it is based on the scale differences.
Grizz is correct. The slope would not be steep in the slightest.
If i did my math correctly then the road would only drop 0.1368 inches per foot or keeping it in metric units 0.01125 meters per meter traveled.
-
Side note: I was talking to one of the PE's I work with and he said that 90% of the short bridges in TX that he's dealt with are fabbed from precast concrete whereas the larger spans tend to be fabricated more of steel beam and girders. Didn't have time to get into a long winded discussion with him for a lot of detail.
-
If you adjust for scale (height/length) you can quickly figure out that any type of arched design is probably not suitable.
So, if you go by the cost, the cheapest would be three section pratt truss (or variation of thereof) steel bridge.
If you account for the maintenance, than two section (one center pylon) pre-stressed concrete balanced cantilever design would suit you perfectly (aesthetics).
You're right about maintenance costs, but have you looked up the prices of structural grade steel in the last decade? After shipping, permits, securing enough qualified union steelworkers, etc. etc. it's easily over 3-times the cost of on-site or off-site prestressed concrete fabrication. Prestressed concrete is the popular standard now in everything from bridges to hospitals.
For a while the price was rising so steeply that contractors would buy all the steel they would need years in advance (as soon as they could get their first bid documents) and let it sit. This caused problems in itself because beams ordered from the foundry 2-3 years ago may not be needed or have been modified during the permiting or VE process. Even on conrete jobs they can't leave the exposed or stock rebar unsecure these days else scrappers will come by and pinch it all in a second.
How do you know a steel truss is cheaper than prestressed girders?
He doesn't because I'll tell you right now and up-front he's so wrong in today's market it's not funny.
It's structurally more efficient and design is cheaper at these lengths. As for the economical efficiency for the lifespan of the bridge, I don't know. That depends on many factors.
Please, just stop or present to us your sources. Yes, it's apears to be structuraly less mass (a few steel beams instead of slabs, beams and blocks of concrete) , but far from effecient or economic.
-
steel prices are currently trending up again.
-
You're right about maintenance costs, but have you looked up the prices of structural grade steel in the last decade? After shipping, permits, securing enough qualified union steelworkers, etc. etc. it's easily over 3-times the cost of on-site or off-site prestressed concrete fabrication. Prestressed concrete is the popular standard now in everything from bridges to hospitals.
For a while the price was rising so steeply that contractors would buy all the steel they would need years in advance (as soon as they could get their first bid documents) and let it sit. This caused problems in itself because beams ordered from the foundry 2-3 years ago may not be needed or have been modified during the permiting or VE process. Even on conrete jobs they can't leave the exposed or stock rebar unsecure these days else scrappers will come by and pinch it all in a second.
He doesn't because I'll tell you right now and up-front he's so wrong in today's market it's not funny.
Please, just stop or present to us your sources. Yes, it's apears to be structuraly less mass (a few steel beams instead of slabs, beams and blocks of concrete) , but far from effecient or economic.
Again, I said steel bridges trump concrete bridges when it comes to structural efficiency. If you'd bother to read, you could see that I said I don't know which would be ahead for the life cycle economics.
But again for you:
1. There is no such thing as one type fits all, especially when it comes to bridges
2. Every type of bridge design has its optimal span length which vary by the type. Out of that optimum it will most likely be less efficient then type within the range.
3. The above will influence type selection
4. Price of the material and fabrication is only one aspect of life-cycle economics of a bridge
5. At given span length of 400-500 ft, and other data given by Grizz, best choices are a)over-deck steel truss b) segmental pre-stressed concrete (mentioned in one of my previous posts)
6. No engineer worth his salt will tell you which is more economical without 'case by case' life-cycle cost analysis (everything else is just a guess).
PS
my sources:
Publications of American Society of Civil Engineers (ASCE)
Issues of The Journal of Structural Engineering by ASCE
Issues of The Practice Periodical on Structural Design and Construction by ASCE
Issues of The Journal of Management in Engineering by ASCE
Publications of American Iron and Steel Institute (AISI)
Publications of American Concrete Institute (ACI)
Publications of American Institute of Steel Construction (AISC)
-
Again, I said steel bridges trump concrete bridges when it comes to structural efficiency. If you'd bother to read, you could see that I said I don't know which would be ahead for the life cycle economics.
But again for you:
1. There is no such thing as one type fits all, especially when it comes to bridges
2. Every type of bridge design has its optimal span length which vary by the type. Out of that optimum it will most likely be less efficient then type within the range.
3. The above will influence type selection
4. Price of the material and fabrication is only one aspect of life-cycle economics of a bridge
5. At given span length of 400-500 ft, and other data given by Grizz, best choices are a)over-deck steel truss b) segmental pre-stressed concrete (mentioned in one of my previous posts)
6. No engineer worth his salt will tell you which is more economical without 'case by case' life-cycle cost analysis (everything else is just a guess).
PS
my sources:
Publications of American Society of Civil Engineers (ASCE)
Issues of The Journal of Structural Engineering by ASCE
Issues of The Practice Periodical on Structural Design and Construction by ASCE
Issues of The Journal of Management in Engineering by ASCE
Publications of American Iron and Steel Institute (AISI)
Publications of American Concrete Institute (ACI)
Publications of American Institute of Steel Construction (AISC)
If you adjust for scale (height/length) you can quickly figure out that any type of arched design is probably not suitable.
So, if you go by the cost, the cheapest would be three section pratt truss (or variation of thereof) steel bridge.
If you account for the maintenance, than two section (one center pylon) pre-stressed concrete balanced cantilever design would suit you perfectly (aesthetics).
Since we're now talking about structural effeciencies and not costs of design, fabrication or construction, then yes, I do agree that in general steel is a superior material. Then again, so would titanium be to steel (if it were plentiful enough and thus, cheap).
-
Here's one for you guys.
Two years ago I designed an 80 ft pole with 18 fixtures for 72 EPA in a 90 MPH zone under AASHTO 1994 as defined by the customer. The pole calculates out to be at 96 percent capacity under full load. A few months ago I was asked if they could add another 18 fixtures. Knowing the answer was no but also knowing the customer I ran the calcs and it came out 30% overstressed and adding wall thickness (new pole) didn't help because the bolt circle was required to be increased by 4 inches and the foundation was beyond max capacity.
Sorry Mr customer it wont work you'll have to do a new install if you want that much EPA.
This morning I received a request to see if they could install a 100 ft pole on the existing foundation if I designed the new pole to fit over the existing anchor bolts and they installed chem bolts to fit the new bolt circle and used commercial code... :huh :headscratch: :bhead
-
I know the answer to this.. B
-
I know the answer to this.. B
I thought it was C :huh
-
Can i work on mine a little bit this weekend? Iver never tried a bridge, and i could use some contructive criticism.
-
I thought it was C :huh
You're BOTH wrong... the answer was 'chartreuse'
-
(http://i600.photobucket.com/albums/tt86/splittiebus66/ohnogodzirra.png)
oh no godzirra
-
(http://i600.photobucket.com/albums/tt86/splittiebus66/ohnogodzirra.png)
oh no godzirra
Run Nikki RUN!
-
there is actually a bridge here in alabama that pretty much looks just like kilo2 design. concrete pillars, steel girders with a concrete road deck.
-
If only every bridge designer/engineer in the world had an unlimited budget on every project..... sometimes ya get lucky though: http://en.wikipedia.org/wiki/Sundial_Bridge (gorgeous (and ingenious) bridge IMO though if ya ever get the chance to see or study it).
That's taxpayer money baby! (albeit one of the nicer uses of it)
(http://www.wayfaring.info/wp-content/uploads/2007/11/turtlebay01.jpg)
Day
(http://images.litwc.com/bridges/SunDial%20Bridge.jpg)
Night
(http://www.americantrails.org/i/resourceimages/Sundial3.jpg)
The bulk of the $23.5M overurn from the original $3M from Redding was covered by the McConnell Foundation out of pocket. Redding city councel wanted a simple steel truss foot bridge. Santiago Calatrava was given carte blanche because a small concortium of Lawyers and doctors in Redding wanted a Calatrava to bring in tourism dollars. It didn't hurt that majicly california issued Calatrava his CA license the same day he applied. Kinda like a day after he got off the plane from Spain. He had no U.S. bridge building experience before that. But again it's only a really expensive "Foot Bridge".
The sacramento river did it's 100 year peak flood in the 1980's. So everyone tied to this project will be dead and gone when the area under the dial end of the bridge washes away in 2080. Before then all that expensive Spanish tile covering all of the exposed concrete will have fallen into the river.
Yes this is what a "Private Foundation" carte blanche buys you. Something the city councel won't be able to afford the upkeep on and the state will ignore because it's not a vehical traffic bridge. I guess it will fall on the taxpayers then. Sounds like a dry run for our fearless Bamster today.....
-
(http://i177.photobucket.com/albums/w229/tes111/Bdg.jpg)
Think Kilo nailed this one. Essentially a 9 foot grade change over 549'. Now if you could just criss cross the lanes (one over and one under) a couple of times so that you end up back on your side of the road, then run the pilings through the center of the crossings and suspend the road beneath via cable and a brace from below you would have a twisty bridge that people could see both sides of.
-
(http://i177.photobucket.com/albums/w229/tes111/Bdg-1.jpg)
Should look more like this.