concrete pour 1

[shaurya241100]

Hi Guys,

Any one dealt with concrete pouring sequence for simply supported and integral construction for both single span and multispan bridge decks?

 

[civilperson]

A patterned pour is usually specified to minimize shrinkage effects. Example; center third of span, then outside thirds for simple span.

 

[kelowna]

I assume you are asking about composite sections (concrete deck over steel beams)

On simply supported spans, a single pour is fine. If area too large, a central pour (say 50% of the span length) and then two end pours

On multispan bridges, leapfrog is the norm to reduce cracking and shrinkage problems. Pour abutment to inflection point on span 1, then pour central portion of span 2 (between inflection points), then central portion of span 3, then pour infill section over pier 1. Continue. This arrangement should minimize cracking on the already poured and somewhat green concrete.

Obviously pour sequences should be considered during the design and a sequence should be specified to the contractor. Changing the pour sequence changes locked stresses on steel and concrete, affects bridge stability during construction and it might change the required precamber on the steel beams.

 

[bridgebuster]

One thing to add - with an integral abutment bridge you need to pour the backwalls separately from the deck; otherwise you run the risk of cracking the deck.

 

[kelowna]

Good point bridgebuster!

 

[bridgebuster]

thanks kelowna

 

[shaurya241100]

Thanks guys.

I was just thinking what effect does the pouring sequence has on the substructure design. For example if it is an integral piled abutment structure (single span)with or without composite superstructure, woulkd it not be suitable to pour concrete deck first in the central span portion and then on the ends.

However, what would be the case when it is a multiple span deck (composite or only solid slab), which is made continuous for live load?

In other words, if you want to economise a structure, single span or multiple, what should be the concrete pouring sequence in each case?

Thanks

 

[bridgebuster]

You shouldn't pour the deck & abutment simultaneously; doesn't matter if your bridge is simple or continuous.

If your bridge is a simple span pour the deck in one shot.

If it's a continuous bridge pour the deck as you would for any continuous bridge.

 

[BRGENG]

We pour 100 ft single span bridges in single pours all the time and we pour multi span bridges up to 300 ft in a single pour without control joints or expansion joints and we have never had problems with shrinkage cracks. Be sure to pour you end and intermediate bent diaphragms 30 – 60 minutes before pouring the deck over them.

 

[shaurya241100]

Thanks Guys.