Uzokwe's Searchlight

Tuesday, September 5, 2017

Alfred Obiora Uzokwe, P.E



n the 28th of December 2016, while on vacation in Nigeria, I had the opportunity to visit Awka, the capital of Anambra state, along with my wife and my brother. We were there to visit our mutual friend.

Before our visit, I had been reading, on the internet, and seeing the pictures of a newly constructed bridge in Awka. Some referred to it as a cable-stay bridge while others argued that it was not. Because the pictures I was seeing were taken from an angle that did not clearly show how the various components of the bridge were supported, I could not tell, in very clear and definite terms, if the bridge was a true cable-stay. So, when we paid a visit to Awka, I took a closer look and came to a more definite conclusion. Nonetheless, I applaud the state government that built the bridge because it seemed to have become a landmark in the state capital that many use as a symbol of the development in Anambra state and Awka in particular.

We originally approached the bridge from the underside so I could clearly see how the “cables” were attached as well as how what were supposed to be the towers or pylons were positioned. I took a series of pictures (attached in this commentary). We eventually made our way to the top of the bridge deck and I got an even clearer perspective of the bridge deck, the “cables” and the “pylons”. As someone who has worked on a series of bridge construction projects, I could tell that the towers or pylons were not integral load-bearing elements of the bridge. They were merely “attached” to the bridge deck as aesthetic elements. As for the cables, they are also aesthetic elements attached to the bridge deck via the parapet jersey wall, and play no load- transfer role as they would on a true cable-stay bridge. It became clear to me that it was not a cable-stay bridge.

The difference between a cable-stay and a traditional bridge is that in a traditional bridge system, the deck simply rests on a system of piers or columns just like the decking or floor of a building is supported by the pillars. The load from the bridge deck is simply transferred to the piers and in turn transmitted to the ground via the foundation. But in a cable-stay bridge system, the cables are attached to the bridge deck and then all connected to the towers. The load from the bridge deck is transmitted, via the cables, to the towers or pylons. The towers in turn transmit the load to the foundation and eventually to the ground. Therefore, the towers are not supposed to be suspended on the bridge deck but instead constructed from the foundation to the top.

By the time we began our return journey to Nnewi from Awka, darkness had fallen. As we approached the bridge, it clearly dawned on me why many are so proud of the bridge. I was impressed by the way it was adorned and festooned with Christmas lights and ornaments. The bridge was lit and reminded me of some of the many historic bridges that are decorated during the Christmas period in western countries. Even if the “cables’ and “pylons” serve no structural purpose, I could see that they were used as place holders for attachment of Christmas lights and decorations that made the bridge look beautiful. Frankly, I loved what I saw as far as the decorations.

I can say, without fear or contradiction, that the state government provided a bridge that has become a landmark especially during the night and festive seasons. But I wonder what it cost to make it that way? From what I know, the cost of a cable-stay bridge is almost 20 to 30 percent higher than a traditional reinforced concrete utilitarian bridge of the same span. When I asked the cost of the Awka “cable-stay” bridge, I was told that the government did not reveal the cost!

So what is this writer’s beef? No beef but just to say: don’t call it a cable-stay bridge. You can call it a “faux cable-stay” bridge. Also, if the bridge was billed and constructed as a true cable- stay, then we the people of Anambra state need a refund but if it was constructed at the cost of a simple traditional pier and deck bridge, then the Anambra state government was brilliant in using one stone to kill two birds of achieving the desired function of relieving traffic congestion and also making it a night time land mark in the state.


Approach to the bridge a beautiful sight at night

Cable and pylons merely attached to the bridge