Pouring of a Huge beam
Pouring of a Huge beam
(OP)
We are preparing a method statement for pouring of a huge beam 3.0 (width)x 5.90 (Depth) X 21.0m (Span). The beam shall be poured in stages, each with depth around 1.50m. We are preparing to pour the first bottom 2.0m with the required formwork to support its weight. Then, this beam shall work as a support for the rest of the depth (formwork shall be removed). This is required because this beam is 3 floors higher than foundation, and making formwork to support all this huge mass shall cost a lot in time and money.
I am asking, shall this arrangement affect the final behavior and stress distribution of the complete beam?
I am asking, shall this arrangement affect the final behavior and stress distribution of the complete beam?






RE: Pouring of a Huge beam
That is an unbelievably big beam if those cross-section dimensions are in meters!
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
I would be concerned about removing the shoring even after the first 2 meters has achieved the desired strength. You have a large dead load consideration that would not be resisted by sufficient compressive concrete. This will "pre-stress" your top rebar in compression when the bottom 2m bends under self load. Check for buckling or displacement of the compression rebar if you remove the shoring.
When the lower 2m has achieved strength, the existing formwork and shoring should support the additional 1m of placement when coupled with the strength of the partially completed beam section.
Pay close attention to the concrete mix design. It is important to make sure you have a proper mix design for strength gain, aggregate size for prevention of voids and for proper encapsulation of the rebar.
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
Ron, I have added top reinforcement at each cast, working as a compression steel and provide continuity with columns. Actually top bars of the original beam shall be installed after pouring the first and second cast with the upper inverted U-links. I do not understand what is the additional one meter. Formwork is required to be removed to allow finishing work at the lower floors, and to minimize the load supported by it.
MoonlitKnight, I assume that the first 2m supporting all weight above it, and so consider all other as weight only. Is this something wrong with this approach?
RE: Pouring of a Huge beam
BA
RE: Pouring of a Huge beam
How long do you plan to wait between the placements?
RE: Pouring of a Huge beam
Dik
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
dik, We did a mock-up thermal test with the 1.5m depth, and it is OK for the type of concrete used.
Ingenuity, Post-tension may be a good idea. Thanks I shall explore it. Thanks to all.
RE: Pouring of a Huge beam
I would also think a post tensioned beam is a possible better solution...
RE: Pouring of a Huge beam
A 2m deep beam spanning 21m with the huge amount of load you are adding just two weeks after it is poured is going to deflect substantially during and after pouring the upper beam section. This will disturb the initial set of the new concrete, resulting in micro cracking.
Third point re-shoring was a suggestion. You could space them closer if you wish. With a 3m wide beam, you would not use a single shore under the center of the beam. You would use two shores about 2m apart.
With shores at 7m centers along the beam, each shore would carry 3000/2 = 1500kN for the weight of the 3.0m x 5.9m concrete beam. A steel HSS, braced at each floor level could easily carry that but I would not quarrel with you if you selected a spacing of 3.5m instead. You would need a foundation under each shore to carry the temporary load, but that is not unreasonable for the project you are undertaking.
BA
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
RE: Pouring of a Huge beam
As opposed to some of the advice to reshore, I would approach the construction of this transfer beam in the same manner as you. As Ingenuity suggested, I would use post-tensioning, with at least enough stressing to balance the dead load of the first lift. Staged stressing is typically used in big transfer beams.
RE: Pouring of a Huge beam
BA