What do you think - large mat foundation lap splices on end

[InEngCAN]

I am curious about what some of you might think about this mat foundation I designed.

The foundation holds a large steel tower, anchorage was done by others and governed the thickness of the slab for the required embeddment.

The design called for 25M@300 B&T E-W, the lap splices at the end don't overlap but it looks kind of weird. See below. The only reason I could think of that the laps should overlap is to tie it together better so they don't shift.

Open for discussion!

My interests: Fire Safety Engineering, modern wood products, 3D Design and Drafting, Engineering Surveying

 

[BAretired]

Probably would look better with an overlap, but not structurally required.

BA

 

[CURVEB]

We sometimes detail this condition with a U bar at the end and no hooks in the top/bottom mat. The U bar lap-splices with the top and bottom bars. Otherwise, we sometimes call for the hook to be a "full depth" hook instead of a standard hook so that they can overlap. This is our preferred detailing practice but as BA said is probably not required.

 

[InEngCAN]

The benefits being is it just looks pretty? On the shop drawing it looked fine

-Andrew

http://www.INengineering.ca

 

[BridgeSmith]

Generally, I think it's just easier to tie with the bars overlapping, and it allows the top mat to be supported by the main steel around the edges.

Not sure if it would qualify as shrinkage and temperature reinforcement, if that's required (not usually for a foundation).

 

[JoshPlumSE]

I don't see a "problem" with the way it is now. Certainly looks a little silly though.

However, I would have thought the construction guys would have caught it earlier and either lapped them like you said or used U bars like CurveB suggested. It's just so much easier to build.

 

[SlideRuleEra]

The only reason I could think of that the laps should overlap is to tie it together better so they don't shift.

IMHO, that statement, by itself, is reason for laps. During concrete placement, a rebar cage has to take a lot of "punishment". If it moves during placement there is not much that can be done. The cage needs structural integrity to remain where it should be until concrete placement is complete.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[BAretired]

Seems to me that top steel must be chaired to the correct position over the entire area, not just at the edges.

BA

 

[BridgeSmith]

If the bars at the edges have continuity, then chairs are only needed to support the interior areas.

 

[InEngCAN]

Thanks for the input everyone - next time I will definitely spec some u-bars for construct-ability or use larger lap splices.

-Andrew

http://www.INengineering.ca