Sustainability of Semi Integral Steel Concrete Composite Bridge

[SuperStressed]

I will soon begin to design a semi-integral steel concrete composite bridge, consisting of two main steel beams with transverse beams to take the form of a ladder beam. The deck slab will consist of cast in situ reinforced concrete.

I originally proposed a fully integral structure, however the client is reluctant to accept this, however is keen on driving for a sustainable structure. Does anybody know of any significant sustainability (maintenance and environmental) issues with this type of structure?

 

[Dinosaur]

If I understand your description, you are preparing to design a two girder fracture critical bridge girder system. This will add cost to your project over a standard multi-girder system using four or more girders in parallel and eliminating the floor beams. An integral bridge is currently thought to be less maintenance intensive than a bridge using joints. There are many papers you can find with an Internet search on that subject. In my experience, one of the most important steps in building a good bridge is the placement and curing of the concrete in the deck. Don't be shy about the deck thickness. If you are waffling over two thicknesses, choose the next thicker section. Good Luck.

 

[Qshake]

I agree with Dinosaur about the lack of redundancy in the two girder system. Also with the two girder system there will be the tendancy to use the floor beams and or deep diaphragms. If those are not properly anchored to the flanges there will most certainly be out-of-plane bending in the web of the girders and that means....cracks!

On the matter of semi integral. I think this configuration is good and don't see a problem with it since most arrangements I've seen have the joint behind the mudwall and before the actual bearing beam. The mudwall is usually deep enought to ensure that all runoff will not intrude into the bearing gallery (I'm assuming your from the UK).

At any rate, using the the semi integral will eliminate concerns over the cracking of the slab due to residual moment transfered from the slab to the diaphragm, though this is not very common any more. It will also eliminate cracking of the diaphragm due to rotation of the abutment as the wingwalls resist the rotation. In short you get the benefits of the open seat abutment without the expansion joint.

Regards,
Qshake

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