Bridge Engineers needed....

[jeronij]

Ok, I will try to explain how to take the measure for such a bridge, using some pictures I made for you:

A top view on a bridge design:



You must study carefully this picture, because it shows the areas that can be used for modelling, and those which dont.

Turning this into 3D, and just to show you the idea, these were the useable areas for the models for the start/end and center pieces. 



In fact the boxes that you can see in this picture, are very similar to the final LOD for this bridge, but I would make them twice taller for such a intercontinental bridge.

This is another variation, using some more lenght to the -Z



In both cases, we would use overhanging props for both pieces, but a single model for each one ( the start end and the towers/center pieces) for the sake of simplicity.

I hope you get the idea

[Sir Charles of Dunlap]

Okay... I see now what you guys are saying, bigger is better. I like that, I too would like to have a mega bridge in my city. One problem, you guys have been suggesting I play with the custom bridges in the game, but I can't get them to work, I can get the ones that were included with the January NAM to work but nothing else. I have tried a few different things but they haven't worked, it's probably the fact that I have the old ones in there. Well I will try to get them to work so I can check them out. In the mean time, any batters out there who know their way through BAT very well, is there a way for me to expand the pieces to exact dimensions, or only in certain directions (stretch). I know there is the scale tool but I don't like using it because it throws everything off.

-Charlie

[jeronij]

Of course the above bridge design is just an idea.
The start/end piece can have different lengths. 2x1, 2x2, 2x3, 2x4...
The center/column piece too: 2x1, 2x2, 2x3

However, the smaller the pieces are, the best, to avoid graphic glitches 

[Sir Charles of Dunlap]

Oh, well, I did find a way to make the piece I have bigger in the ways it needs to be.

How is that for size? I am going to add light towers on the top, anything special for adding the lights that I need to know about? Okay, so I think once I make the start/end piece I will be done with the major work on this bridge. Then I will need to add all the little details. Dang, this isn't as easy as I thought. lol Oh Jeronij, have you had time to play with my other model?

-Charlie

[mightygoose]

ok so we can only use 8m either side of the deck tiles... and the rest would have to be overhanging props... ok im with you.

[Shadow Assassin]

Well, theoretically, it should be possible to have bridges wider than 16/32m, it just involves a helluva lot of cheating with the model. Here's what I think could be possible - the model itself could be three tiles wide, but only one tile is the deck - the extra two tiles would be the er, ornamentation...

[mightygoose]

see realisticially for the gibralta you are looking at 3 tile wide roadway to accomodate gap in middle, it would be your standard highway, i think the RHW6 would be cool. then your looknig at like 2 tiles each side for those supports... so 7 tile wide bridge with three tile roadway.... im assuming that is totally impossible.

[jeronij]

I dont think we can build the Gibraltar bridge at something remotely similar to real scale. We are limited by the game. The actual wider bridges are 32 meters wide. This is the logical limit. We can exceed it a little bit, as showed in the pictures, but that's all  More that this will create way too many graphic glitches with the automata 

[mightygoose]

ok

[jeronij]

More on this,

the width of the bridges is set in the bridge exemplar. Theorically we could build any width ( always SC4 tiles) bridge. However, nobody has accomplished a more than 2 tiles width bridge so far. The first thing that comes to my mind is that the wider transit network is 2 tiles, so something like puzzle pieces or transit enabled lots would be needed to be able to build such a bridge.

This could be a good challenge for some modder with time and willness.... who knows?, that it does not exist does not mean that it can not exist   

[willvette]

a scaled down version would look better, if you recall, i requested a long highway bridge and a med. monorail/HSRP bridge

[Sir Charles of Dunlap]

How is that for detail? I added cables, two light towers on top (for planes to see) I added a foundation, did some texturing, and added a maitinence entrance. Well, I just noticed something I forgot to size down, but unless there is anything I have to change I am done with the support. Well, it does need road lighting, and okay, so I have three things on it. lol 1. lighting on the deck 2. rescale one support thing, see middle of support, down one from the top. 3. wait was there a three? lol The bridge deck for the rest of the bridge will be the same as there. Hmm... Now for the end/start piece. I started a couple different ideas, but trashed them, they sucked. I am not quite sure what to do, because I don't want the foundation to be under water, but if it isn't the deck will be 40 meters or so above the water, I am thinking elevated highway bridge, and the endpiece will have to slope down, which is possible right? I would assume so sense there is a raised road bridge in the game.

-Charlie

[Ennedi]

Generally I like your present work very much. But I would like to make one suggestion:

You should think about these diagonal cable-stayed struts. They are not used on smaller bridges. What is their function? I am not a bridge engineer, but I make some work on large steel and conctrete structures. I think these struts are needed to precisely adjusting the stretch of main suspension cables and to give them the proper stress pattern. I can imagine these struts don't need to pull the main cable - they can suspend it to chang the cable curve. The second reason of use such solution: the pylon with suspended cable is much more stable. The third reason: engineers can adjust the length of struts to extinguish vibrations caused by wind, traffic, earthquake etc. especially the resonance.

What is the conclusion from the sc4 point of view? Look at the picture below

may i make a request, theirs this one bridge that was proposed to cross the Strait of Gibraltar (between Europe and Africa) and it looks so cool . "The suspension cables for these longest bridges are suspended from the ends of cable-stayed struts extending diagonally from huge pylons."


I would like to request a large version for ground and raised highway and a small version for monorail/HSRP, Plz

And make somethhing similar. Struts should be a bit more massive ( but they are wider at the pylon and narrowed at the end - so they look light) and they should suspend main cables.
I suggest you to draw main cables first and then adjust the length and angle of cable-stayed struts to the curve of main cables.
Sorry for bad english, it was hard for me to explain it.

[jeronij]

Thanks for that explanation Ennedi. I totally agree 

SirCharles, you can also check this thread: 
http://www.simtropolis.com/forum/messageview.cfm?catid=124&threadid=70813&highlight_key=y&keyword1=double%20decker and have a look to the pictures from the Tsing Ma bridge.... specially the towers... this is the level of detail I like the most 

[stewart_garden]

I must admit that I am a bridge engineer (I know, I know, it is a terrible affliction...) and I am stumped as to the function of the diagonal 'struts'.  However, if this is what Charlie wants to make then it is up to him...

Stewart

[mightygoose]

sir charles... if yours is meant to be a scaled down version then your model is fundamentally wrong.... look at the render... look at the far tower...



as you can see there is only one diagonal strut... not two.... as to the reasoning of their existence is it not to take some of the vertical load from gravtiy and using it as a pivoted symmetrical horizontal brace to suspend the cables further.

speaking of cables sir charles.. it als helps if your cable arrangements are symmetrical on either side of the tower.... just a thing i noticed.

btw thats rougly a full sized model... seven tiles wide, roadway for RHW6, the diagonal strut total span one side to other is 480m.... height of towers around 320m and the water is a medium city tile

anyway i just thought id illustrate the major structural layout of this bridge, i know the proportions arent quite there, the real one being taller with longer struts.. the cabling i could demonstrate as well i spose....

oh and btw did a bit of digging it seems someone has already modelled the original version for flight sim...





here is an article outlining the reasoning for the slanting struts...

[linkie]

a plan drawn up by a guy making a lego version... also old design...





for you major bridge fanatics... here is an index of 162 bridge structure type/region specific sites....
[linkie]

[stewart_garden]

Interesting article about the Gibraltar bridge Mightygoose - thanks for the link.  It seems the intention would be to reduce the span of the suspension cables, hence reducing the required size.  Not sure how viable this would be in real life tough...

Stewart

[Sir Charles of Dunlap]

Wow... I think I am finally catching on, and just when I was about to ask what the struts were... Hmm... So I have made to conclusions from this, 1. I am going to be spending a little time with the model making it more Gibraltarish, and 2. I am going to need to study engineering before finishing this project. lol Well not really, but come on you engineers you I am only in highschool give me a break. lol But having more pictures to go by does make things much easier. Thanks guys, I will try, ok will make things better. It might be a little while before I am back, but probably not as long as I think...

-Charlie

[jeronij]

Thanks for these great pictures and detailed information mightygoose    These pictures are really nice, and shows the right dimensions for such a beast 

stewart, fortunately the physics and dynamics in SC4 are not simulated at all    ,

[Ennedi]

stewart, fortunately the physics and dynamics in SC4 are not simulated at all    ,

Yes, it is very favourable circumstance 
But it is very good that sc4 creators try to think in logical way and make realistic objects. I think sc4 could be a great place to show some extraordinary engineering projects - existing and planned. Some of projected ultra-modern structures need completely new building materials and must wait a few years. But it is an excellent thing to see somebody's vision how it could look in real world.
This bridge is definitely worth to show. There are some interesting small and middle-sized bridges (such as Gateshead), but large suspension bridges look similar. This one is completely different. I said it earlier, but I repeat: it doesn't need to be larger than Akashi. Maybe it can have higher pylons, but having the same size it will look more massive because of these "struts".

@Mightygoose, you made great addition to this thread!