PROUD-IGBO:
Nice pics. Can someone with a civil engineering background explain the function of the cables extending from the 'tower' to the main section below? I thought that they are meant to serve as suspension cables (kinda like the Golden Gate Bridge in San Francisco) to hold the bridge up?

From the little i've seen in the pics, it looks like the bridge doesn't need that kind of support as it's being constructed like the third mainland bridge. I'm thinking they're being used just for aesthetic reasons.....to make the bridge look grand.

I'm not a civil engineer. But with my background in engineering design, this type of bridge is called a SUSPENSION BRIDGE. The fulcrum of this type of bridge usually supports the bridge weight via "knotty" steel cables, usually at the center or at 2-3 intervals as the case may require. The array of these cables may form a parabolic shape required for systemic weight distribution. Although this particular design doesn't seem like a complete suspension bridge, because I can see that the horizontal slabs (or span) are also simultaneously supported by columns (piers). So, I could say the weight of the bridge is being supported by both the columns (piers) and suspension cables.

In Nigeria, the two common types of bridge design are beam bridge and steel bridge. We actually have more beam bridges and very few steel bridges (e.g. Niger bridge, Onitsha) in Nigeria. This suspension bridge will be the first of its kind in Nigeria, I guess. Kudos to LASG for pioneering this kind of bridge design in Nigeria!

Safety is my concern, why was Fashola and his team of inspectors not issued hard hat for the duration of inspection or was there a work stoppage throughout the inspection which I doubt possible?

Very interesting.

The bridge shall be named after fashola.

stillme: The bridge shall be named after fashola.

The bridge shall be named after Mandela.

Tony Spike:

I'm not a civil engineer. But with my background in engineering design, this type of bridge is called a SUSPENSION BRIDGE. The fulcrum of this type of bridge usually supports the bridge weight via "knotty" steel cables, usually at the center or at 2-3 intervals as the case may require. The array of these cables may form a parabolic shape required for systemic weight distribution. Although this particular design doesn't seem like a complete suspension bridge, because I can see that the horizontal slabs (or span) are also simultaneously supported by columns (piers). So, I could say the weight of the bridge is being supported by both the columns (piers) and suspension cables.

In Nigeria, the two common types of bridge design are beam bridge and steel bridge. We actually have more beam bridges and very few steel bridges (e.g. Niger bridge, Onitsha) in Nigeria. This suspension bridge will be the first of its kind in Nigeria, I guess. Kudos to LASG for pioneering this kind of bridge design in Nigeria!

From what I see, the cables suspend the weight of the platform (about 100m on either side of the pylon). As far as I can see, this horizontal part is not supported anywhere else. Therefore, the vertical support for this portion is provided by the cables. If look at the pictures in the previous page closely, you'll see the suspension cables were already in place as soon as the platform was installed. If the cables were to break, this platform will collapse.

nateevs:

From what I see, the cables suspend the weight of the platform (about 100m on either side of the pylon). As far as I can see, this horizontal part is not supported anywhere else. Therefore, the vertical support for this portion is provided by the cables. If look at the pictures in the previous page closely, you'll see the suspension cables were already in place as soon as the platform was installed. If the cables were to break, this platform will collapse.

You are just about right, nateevs. I believe my observation is a little bit lacking due to the poor quality of the pictures. The bridge in neither a full beam bridge nor full suspension bridge. The suspension part of the bridge is the nearly 150m/200m span as noticeable in the uploaded pictures. While we cannot rule out the possibility of a bridge collapse, I do hope the designers of this bridge have done rigorous load failure analysis and other structural integrity tests. Thanks for the added information and observation though.

nateevs:

From what I see, the cables suspend the weight of the platform (about 100m on either side of the pylon). As far as I can see, this horizontal part is not supported anywhere else. Therefore, the vertical support for this portion is provided by the cables. If look at the pictures in the previous page closely, you'll see the suspension cables were already in place as soon as the platform was installed. If the cables were to break, this platform will collapse.

It is a poor observation on your side. The cables are more or less a fancy design than supports for the bridge. It is not a suspension bridge in any way. If you take a closer look at some of the clear images you would find out that there are supports rising from the bed of the water for the bridge.

This image below illustrates what I am trying to explain.

Finally! I was looking for a map I drew about a month ago. The map explains it all. But the picture above is just perfect.

Think of it as a bridge with two sections.

1) The picture above shows where the bridge curves round Lekki Phase 1. That section of the bridge rests on piers.


2) The section after the curve is the section that spans five cowry creek (that is the section you see in most of my pictures). Much of this section is suspended from cables. The tower is almost halfway between Lekki Phase 1 and Ikoyi.

The toll plaza is right at the beginning of the curve.

[quote author=all4naija]It is a poor observation on your side. The cables are more or less a fancy design than supports for the bridge. It is not a suspension bridge in any way. If you take a closer look at some of the clear images you would find out that there are supports rising from the bed of the water for the bridge.

This image below illustrates what I am trying to explain.
[quote]

No, it is not. Take a closer look at the pictures. You'll see that the bridge is divided into two parts. There is a part that is suspended by cables and the rest held up by the pillars. I'll re-post the pictures taken by Naptu2 so you can take a second look at it.

[img]https://www.nairaland.com/attachments/687943_IMG00817-20120423-1518_jpgc14dd03fada866bc124e5295cfbe211a[/img]
[img]https://www.nairaland.com/attachments/716297_IMG00877-20120530-1335_jpgd323c5a39b6ff5bed5a4bd94b4d55653[/img]

[img]https://www.nairaland.com/attachments/716303_IMG00880-20120530-1338_jpg70f1bd3951a62eca0a5406ede528eaca[/img]

You are right, Jason123. If you take a look at the suspension section of the bridge, the span is parabolically curved to allow for the stress distribution being handled by the suspension cables. The remaining part of the bridge, apart from this suspension section, is designed using the conventional beam bridge design as seen in the pictures.

Tony Spike: You are right, Jason123. If you take a look at the suspension section of the bridge, the span is parabolically curved to allow for the stress distribution being handled by the suspension cables. The remaining part of the bridge, apart from this suspension section, is designed using the conventional beam bridge design as seen in the pictures.

I still disagree. The suspension is not actually what you would see in a suspension bridge. Even without the ones on IKoyi Bridge most of the bridge can still stand. The pictures posted by Jason123 is a testament to that. The point where the cables are in contact with the bridge just tens of meters away have supports. Take a closer look at the first and last picture by Jason123.

It still looks to me as more of fancy than supports.

These images below better illustrate what I am talking about.

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all4naija: I still disagree. The suspension is not actually what you would see in a suspension bridge. Even without the ones on IKoyi Bridge most of the bridge can still stand. The pictures posted by Jason123 is a testament to that. The point where the cables are in contact with the bridge just tens of meters away have supports. Take a closer look at the first and last picture by Jason123.

It still looks to me as more of fancy than supports.

These images below better illustrate what I am talking about.

You are misunderstanding. Even if its just "tens of meters"; those "tens of meters" cannot support themselves, can they?
I am not a structural engineer but I sure know that to have a full suspension bridge of that length, you'll need at least 3 pillars with each about 3 times a high as the one currently being built.

jason123:


You are misunderstanding. Even if its just "tens of meters"; those "tens of meters" cannot support themselves, can they?
I am not a structural engineer but I sure know that to have a full suspension bridge of that length, you'll need at least 3 pillars with each about 3 times a high as the one currently being built.

Lol... Merely looking at the images one can deduce some facts they can possibly be supported by the pylon foundation resting at the bed of the water like every other support for the whole bridge. It is still a fancy than support - that's my point in all the whole talk.

all4naija: I still disagree. The suspension is not actually what you would see in a suspension bridge. Even without the ones on IKoyi Bridge most of the bridge can still stand. The pictures posted by Jason123 is a testament to that. The point where the cables are in contact with the bridge just tens of meters away have supports. Take a closer look at the first and last picture by Jason123.

It still looks to me as more of fancy than supports.

These images below better illustrate what I am talking about.

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No mate. Those pics do not illustrate what you are talking about. To begin with, those pic do not show the platform in place with the pylon. Those pics also do not show the cables in place.

Secondly, it is very possible that that support you see between the Pylon and the rest of the deck is just a temporary platform to get the deck over the pylon in place and install the cables. How else do they install it. Before you call it fancy, you need to show us a picture of the deck over the pylon and cables installed.


Thirdly, unless you are sitting on a boat right on the side of the Pylon, you are making an error in judgement of distance as a result of optical illusion. The distance between the support on the base of the Pylon and the next support (if it is a true support) is unknown to you. Also the downward force exerted by the weight of the deck and the estimated maximum load applied on the deck (weight of Cars, buses, pedestrians) is also unknown to you. Unless you know the next support is placed at the right spot; which then acts as a counter force for the maximum downward load exertion, you cannot assert that the cables are just fancy. To say that it is, is a clear indication that you do not have any idea about engineering. And I suggest that if you do not know, then refrain from making such comments.


Have you asked why the deck on the Pylon is parabolical is shape?
Have you asked why there seems to be a hollow in the in the deck approaching the Pylon - a feature not continued over the entire length of the bridge?
Have you also asked why the construction seems to be converging at the Pylon end - which seems like the middle? If the Cables were fancy, the whole construction could just be done left to right of right to left, past the Pylon and then they come back for the cables.

Since there is, according to you, no load bearing on the pylon, why waste money building the upper part of the pylon with concrete when aluminium will suffice?

In fact, I have found the perfect for you. On eof the pics posted by Naptu. Look at this picture and you can just about imagine the process of construction. If this does not prove beyond any doubt that the cables are not fancy then I do not know what can.

nateevs:

No mate. Those pics do not illustrate what you are talking about. To begin with, those pic do not show the platform in place with the pylon. Those pics also do not show the cables in place.

Secondly, it is very possible that that support you see between the Pylon and the rest of the deck is just a temporary platform to get the deck over the pylon in place and install the cables. How else do they install it. Before you call it fancy, you need to show us a picture of the deck over the pylon and cables installed.


Thirdly, unless you are sitting on a boat right on the side of the Pylon, you are making an error in judgement of distance as a result of optical illusion. The distance between the support on the base of the Pylon and the next support (if it is a true support) is unknown to you. Also the downward force exerted by the weight of the deck and the estimated maximum load applied on the deck (weight of Cars, buses, pedestrians) is also unknown to you. Unless you know the next support is placed at the right spot; which then acts as a counter force for the maximum downward load exertion, you cannot assert that the cables are just fancy. To say that it is, is a clear indication that you do not have any idea about engineering. And I suggest that if you do not know, then refrain from making such comments.


Have you asked why the deck on the Pylon is parabolical is shape?
Have you asked why there seems to be a hollow in the in the deck approaching the Pylon - a feature not continued over the entire length of the bridge?
Have you also asked why the construction seems to be converging at the Pylon end - which seems like the middle? If the Cables were fancy, the whole construction could just be done left to right of right to left, past the Pylon and then they come back for the cables.

Since there is, according to you, no load bearing on the pylon, why waste money building the upper part of the pylon with concrete when aluminium will suffice?

You comment is based on guesses. There is no temporal supports there coming from the bed of the water. If a temporal supports are going to be used they would likely come from cranes mounted on barges!

It is a cable bridge not a suspension bridge. Even the parts which seem to be supported by cables are also supported by pillars and the pylons. The support by pylons is where the bridge rest on the middle of the pylon foundation. Please, stop speculating. This cable bridge is just fancy like many cable bridge you can find in many countries around the world.

nateevs: In fact, I have found the perfect for you. On eof the pics posted by Naptu. Look at this picture and you can just about imagine the process of construction. If this does not prove beyond any doubt that the cables are not fancy then I do not know what can.

How is it not fancy in that picture? Aren't you seeing the constructed part of the bridge is resting on the fulcrum of the pylon, at the middle than the cable holding it. Spare us the simplicity!

www.nairaland.com/attachments/720896_Lekki_Ikoyi_Bridge_jpgf8473ffcf509d530a127927aab5d3927

The actual rendering of Ikoyi bridge below would be good explanations of what I am saying here.

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[img]http://3.bp..com/-TKUPKnZSDys/TVRETylVW7I/AAAAAAAABXk/l3hYqDGoIwE/s1600/LEKKI_IKOYI_BRIDGE02.jpg[/img]

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[img]http://4.bp..com/-fS-x6QrcT0A/TVREUHKJwRI/AAAAAAAABXs/0LcRSKy0I0o/s1600/2i1mcqx.jpg[/img]

Hehehehe. You are one of those guys who's deemed intelligent and almost always has an answer to everything.
To the ignorant few, you seem like a genius, to those who know from a mile away, you are spreading your tentacles beyond familiar territories.
And it's very obvious now how little you know about the subject, yet forcefully trying to make us believe you know a lot.


I will illustrate with a digram. The construction in the picture I posted previously is mirrored by the paint pic I have attached. The 90M deck is constructed slowly from the middle of the pylon and held in place horizontally by the cables whose support is the Pylon. This is a result of detailed analysis of load bearing and counter-loading keeping the deck in place perfectly horizontally. The construction will continue outwards (from the pylon) until the 90M deck rests on the other ends already in place. How can the middle deck rest on its own before it reaches the other end without the cables.

all4naija: You comment is based on guesses. There is no temporal supports there coming from the bed of the water. If a temporal supports are going to be used they would likely come from cranes mounted on barges!

It is a cable bridge not a suspension bridge. Even the parts which seem to be supported by cables are also supported by pillars and the pylons. The support by pylons is where the bridge rest on the middle of the pylon foundation. Please, stop speculating. This cable bridge is just fancy like many cable bridge you can find in many countries around the world.

That's what I was trying to capture, but the picture quality's terrible. If I still had my digital camera you'd have seen the cranes on the barges (there were 2 barges).

Indeed a picture from the expressway would make it clear that the stretch of bridge that spans five cowry creek would come crashing down if all the cables break. Unfortunately, my camera phone can't take that picture.

all4naija: How is it not fancy in that picture? Aren't you seeing the constructed part of the bridge is resting on the fulcrum of the pylon, at the middle than the cable holding it. Spare us the simplicity!

This response is shocking. It is very evident in the picture and from the illustration I gave that the cables are holding the deck in place. You are suggesting a miraculous load suspension in the middle of the Pylon in manner that looks like this.

nateevs: Hehehehe. You are one of those guys who's deemed intelligent and almost always has an answer to everything.
To the ignorant few, you seem like a genius, to those who know from a mile away, you are spreading your tentacles beyond familiar territories.
And it's very obvious now how little you know about the subject, yet forcefully trying to make us believe you know a lot.


I will illustrate with a digram. The construction in the picture I posted previously is mirrored by the paint pic I have attached. The 90M deck is constructed slowly from the middle of the pylon and held in place horizontally by the cables whose support is the Pylon. This is a result of detailed analysis of load bearing and counter-loading keeping the deck in place perfectly horizontally. The construction will continue outwards (from the pylon) until the 90M deck rests on the other ends already in place. How can the middle deck rest on its own before it reaches the other end without the cables.

Lol... You are the one exercising your imperfect ineptitude here. Indeed, there is what is called 'equilibrium' that is what we are seeing as is responsible for the balanced of the deck with the cables having little or no supporting effect. Where you are missing the point is that the cables being more of fancy than supports must come along with the pylons to get the rightful sense of construction work.Above all you still keep on ignoring the actual rendering of the project yet come up with you theoretical analysis without applying it to the real world and posting against the actual facts available on the rendering and ongoing construction.

Again, the rendering. Point to me how much support the cables can provide compare to the fulcrum of the pylon?
[img]http://3.bp..com/-TKUPKnZSDys/TVRETylVW7I/AAAAAAAABXk/l3hYqDGoIwE/s1600/LEKKI_IKOYI_BRIDGE02.jpg[/img]


Another view to put things in perspective yet not a full explanation of what the equilibrium represent in that pylon case.It is a hollow deck.

You are the one adding more information than necessary to explain what is going on with the bridge. Again, it is a thing of equilibrium and nothing magical about that as you are trying to insinuate it to be.

nateevs:


This response is shocking. It is very evident in the picture and from the illustration I gave that the cables are holding the deck in place. You are suggesting a miraculous load suspension in the middle of the Pylon in manner that looks like this.

You are the one speaking tongue-in-cheek. You forget to understand what I am saying. I repeat, the cables are more of fancy than supports. In other words without the cables the bridge can still stand. There is no magic there than equilibrium playing a major part. It would be right not to have a support at the middle of the pylon leaving the cables with all the support to prove your point, yet the reverse is the case.

The image below shows how a typical cable supports would look like(the Golden Gate Bridge).

Oh now I see All4naija's point. It is clear what he is saying when comparing the first picture with the picture he brought out.

Yes all4naija it is not a full suspension bridge but it is a suspension bridge because without the line the mid-section would collapse. I hope that helps.

No one can make a definitive statement about the bridge, however it is very unlikely that the cable supports will be merely for 'fancy'. Based on the video provided on youtube, you have two bridge sections - the full span approach bridge, and the 'full' cable stay (or stayed) bridge supported by the pylon.

@
The Golden Gate bridge is a suspension bridge, which is different from a cable stayed bridge. The spans used in a suspension bridge are much greater than those for a cable stay bridge, reflected by the shorter span for the Ikoyi bridge. They may appear the same to a layman, but are very different.

The bridges you should be comparing to are the likes of the Alex Fraser Bridge in Canada or the Geoga Bridge in Korea

While the bridge sections close to the pylon will be supported by the pylon (i.e. cantilevered), sections further away are supported by the cables. There is no bridge design without some redundancy, and the cables are likely not supporting the entire bridge length (part pylon, part cables).

If, by calling it 'fancy', you mean that this particular bridge design was selected for its aesthetic qualities, then you may be correct. However, the cables are an essential (not aesthetic/fancy) element of a cable stayed bridge.

Hello people, we are here to learn and I really appreciate it. The arguments and counter-arguments are worth taking a look at. I have taken my scarce time to picture the behaviour of loading pattern on this bridge. I have included some assumed free body diagrams of the active and reactive forces that may be encountered on this supposed "suspension" section. I have tried as much as possible, using the simplest knowledge of moments of forces, as well as turning effects to present an argument.

In this case we shall make two theoretical assumptions on the pylon as thus:

(1) The pylon firmly secures the span section at the middle of the span creating an upward force to support its vertical stability

OR

(2) The pylon acts as a passive fulcrum, supporting only the span section by the virtue of the "see-saw" principle in the absence of loads at both ends.

So, what do we have?

CASE 1: A load application at the right side causes a corresponding oscillatory swinging at the other end. This can be reduced but not eliminated if and only if the pylon firmly secures the span as seen in the assumption in (1). So, how do we totally eliminate this swinging, let's look at case 2...

CASE 2: This swinging can be totally eliminated by applying another support at the left end in form of suspension cables. This is seen in this case. This diagram only shows one cable support for simplicity. This cable, provides an upward force to counter the oscillatory motion ,at least, in one direction.

CASE 3: Let us assume that another load is now added to the left end, in the presence of the left side suspension cable. So, what happens? This may result in unbalanced forces (upward swing) at the right side. How do we solve this, we look at case 4...

CASE 4: Another suspension cable is added to the right side to balance the upward swing at the span section. Thus, the loads are now balanced.


Basically, we can see that the suspension cables will provide stability to the turning effects as a result of the drifts of inbound and outbound vehicles. Thus, the suspension cables may not be as fanciful as envisaged but is definitely serving a purpose. The degree of purpose will depend on how firmly secured the span is to the pylon, of which I am unsure of. We however need to confirm if the pylon is of "see-saw" specification or acts as an active pier (firmly securing the span).

I hope my explanation is lucid enough. Meanwhile, more contributions are needed from experts. May I use this opportunity to implore Seun Osewa to include a science, engineering and design section for Nairaland? I don't see why we should be discussing design matters in the political section.

This is beginning to pan out. @Debosky, your argument only support mine with the images you presented.I never called Ikoyi bridge for once a suspension bridge.I 've never in any of my argument, because, it is not a suspension bridge. Why I make use of the suspension bridge image is for illustration of what cables support would likely or supposed to be if fancy is not partly what it's meant for. The first bridge cables are more of fancy than support excepting for the second one that has a large span of deck without resting on any supporting platform coming from the water.

A closer look at Ikoyi bridge, which is different from the second bridge in your example, only points to something that is not near in comparison to the one we are arguing about.

(a) Ikoyi bridge image compare with yours first image.

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[img]http://3.bp..com/-TKUPKnZSDys/TVRETylVW7I/AAAAAAAABXk/l3hYqDGoIwE/s1600/LEKKI_IKOYI_BRIDGE02.jpg[/img]

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** Why the number 2 bridge might be different from Ikoyi is that the deck is not resting on the pylons but Ikoyi bridge own is. A closer look at the picture, it is there where the deck would likely rest on the pylons(at the middle of the pylons)**

Those two images above point to cables with less support than fancy. There are cable bridges in the world without the cables having anything to do with much of the support but for fancy because of the short span of deck. That is what Ikoyi bridge is like. The span which is to be supported by the cables is to short and the pylon fulcrum is already doing that. The evidences are on the images above.

(b)Ikoyi Bridge compare with your second image.

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[img]http://3.bp..com/-TKUPKnZSDys/TVRETylVW7I/AAAAAAAABXk/l3hYqDGoIwE/s1600/LEKKI_IKOYI_BRIDGE02.jpg[/img]

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The span of the deck of your image is long and there is no platform to rest upon other than the cables bearing the full weight of it, which is different from Ikoyi bridge short deck distance from the pylon and it is resting on the fulcrum of it.In Ikoyi bridge case there is no use even to say the cables could act as balance on horizontal movement due to wind forces as would likely be with suspension bridges. I would be interested to be proven wrong of my argument with good proofs and evidences. Not like the ones you presented in your comment.

On the final note, the distances in almost all sections of the bridge correspond to the ones of the pylons only of a fraction difference.

It is indeed, at the end of the day , all matter of sentiments looking at what many people present here to support the functions of the cables in this Ikoyi cable bridge.It is cable-stay bridge quite alright but the cables are more of a fancy than support, for the fact that the deck of the bridge can still stand without them.

Garbage. Absolute Garbage. I wil post this again and again until you get it. Trying to deduce that the cables are fancy from the final picture is utter rubbish. This is the picture that shows from the outset that the cables are holding the deck in place. Take this picture as it is and erase render from your memory. The construction begins from the Pylon and cables hold the deck in place.

You are the one causing massive confusion for yourself. No one here, you likewise has called this a suspension bridge. No one has actually even suggested that the cable is carrying "all of the load on the deck". However, you are suggesting that the cables are carrying not "one single gram of weight on the deck". This is what baffles me.

How can one tell what is not carrying load by just looking at it? You are not privy to the calculations and load analysis sessions and you keep mentioning with authority that the cables are for fancy. I will get on the fone and contact a ton of people who can get me someone to speak to at JB and confirm and put the results here on NL. If you are right that the cables are fancy, I will own up but if you are wrong. . . . .

nateevs: Garbage. Absolute Garbage. I wil post this again and again until you get it. Trying to deduce that the cables are fancy from the final picture is utter rubbish. This is the picture that shows from the outset that the cables are holding the deck in place. Take this picture as it is and erase render from your memory. The construction begins from the Pylon and cables hold the deck in place.

You are the one with the issue. This is among the simple reasons Nigerians can easily be deceived by expatriates. I said it before, what you are possibly seeing in the picture,you are loudly blabbing about, is done for the project to come along perfectly. Why not remove the fulcrum of the pylon and let the cables be the only suspenders? You seem to be petty in your observations. Dude, stop being sweaty over what you can not clearly understand.

I repeat, the cables are more of fancy than support in this Ikoyi Cable-stay bridge project.

nateevs: You are the one causing massive confusion for yourself. No one here, you likewise has called this a suspension bridge. No one has actually even suggested that the cable is carrying "all of the load on the deck". However, you are suggesting that the cables are carrying not "one single gram of weight on the deck". This is what baffles me.

How can one tell what is not carrying load by just looking at it? You are not privy to the calculations and load analysis sessions and you keep mentioning with authority that the cables are for fancy. I will get on the fone and contact a ton of people who can get me someone to speak to at JB and confirm and put the results here on NL. If you are right that the cables are fancy, I will own up but if you are wrong. . . . .

Your lack of comprehend is overwhelming. You are a daft suffering from autism.

Point to where I called it suspension bridge, mor.on. Point to it!