Are Grade Beams Really Simply Supported?

[bigrod223399]

When a grade beam is designed as simply supported between pile caps, in reality, how are the loads from the columns not being transferred into the beam (assuming unbalanced vertical loads)? My intuition tells me that when the beam is connected to the pile caps by extending the rebar into it, that the compression at each end will create a moment. Is there a reason I never see this accounted for? The only way I can see it working is if a joint is put in between the beam and pile cap, but I never see this on details.

 

[human909]

A picture is worth a thousand words and on Eng-tips you need a factor of safety of 2x on that.

(But to partially stab in the dark at your question. Designing the beam as simply supported is likely conservative for the beam. The piles and pile caps maybe not but you need to examine the relative rotational stiffness's of the items.)

 

[JLNJ]

If it’s just a single grade beam between two single piles, then the thought is that the head of the pile rotates a little to relieve the fixity at the beam ends.

 

[Tomfh]

Agree.

It is generally assumed the structure will redistribute to the simply supported condition as required.

 

[BAretired]

Some are and some aren't.

BA