Column reinforcement ratio at splices 2

[UcfSE]

Let's say you have a RC column with 4% steel. At splice locations, you will have twice as many bars in the cross section. Will these bars count toward your [ρ]_g, giving you 8% steel at splice locations? Is this addressed in any code or text that you know of?

I don't want to try (incorrectly imo) take the bars into account for strength; I want to check steel limits. If you have 4.5% steel for instance, then at a splice, you would have 9%, exceeding your 8% limit.

 

[JAE]

You count the main bars and you don't count the double bars at the splice.

 

[swivel63]

i believe that they will count for the ratio, but not for the strength.

 

[WillisV]

The maximum ratio of 8% is the maximum at any cut through the cross section - so at lap splices where they are doubled up you can have a max 8% (so max 4% for strength elsewhere in the column). If you use mechanical splices however you could run 8% throughout the entire column length.

 

[WillisV]

As a code basis for my statement see R10.9.1 of ACI-02: "...the percentage of reinforcement in columns should usually not exceed 4 percent if the column bars are required to be spliced."

 

[dik]

WillisV has it. The maximum reinforcing at any cross-section is 8% and if you have lapped splices, the maximum is 4% assuming the reinf above is the same as that below. This is one of the few areas of code (ACI and CSA) that hasn't changed for 40 years. If the axial load is high enough or the load is in straight compression, the column size can be minimized using mechanical splices.

Dik

 

[JAE]

I stand corrected.

Thanks for the info.

 

[UcfSE]

What a great help you all are.

I mentioned this to a more senior engineer at work who didn't take my word for it about counting the lap splices with the reinforcement ratio but I couldn't back it up at the time, so I needed a reality check.

 

[ash060]

If any a bind with high reinforcing ratios you can require that the splices be staggered at intervals so as not to exceed 8%