ASCE41 Concrete Moment Frame Check

[structeng2]

Hi Everyone,

I am a little confused by the language in ASCE41 (surprise surprise) regarding the checking of an existing concrete moment frame and what actions are considered to be deformation or force-controlled.

Per Section 10.3.2.1:
"Deformation-controlled actions are defined by the designation of linear and nonlinear acceptance criteria in Tables 10-7 through 10-10 and 10-13 through 10-22. Where linear and nonlinear acceptance criteria are not specified in the tables, actions shall be taken as force-controlled..."

However, when looking at table 10-10a for the columns and 10-13 for beams, the tables do not specify actions (like shear or flexure or axial). So, am I to interpret this that ALL actions of the column and beam (except joints capacities) are deformation controlled?

In other chapters (like ch. 9 for steel), they have different m-factors for different actions (e.g. braces in tension, braces in compression, etc.)

Thanks for your input!

Peter

 

[r13]

Where linear and nonlinear acceptance criteria are not specified in the tables, actions shall be taken as force-controlled..."

However, when looking at table 10-10a for the columns and 10-13 for beams, the tables do not specify actions

I'm not familiar with ASCE 41, and confused that, is "specified actions = criteria"? However, I think your conclusion was reversed from the instruction.

 

[structeng2]

Thanks retired13.

I should clarify a bit -

"actions" in asce41 lingo means the capacity check of various failure modes (shear, axial, flexure, etc.).

In a typical table, they will have sub-sections for each action; so for a braced frame, they will have separate m-factors for tension and compression. However, the tables in the concrete moment frame section does not have sub-sections, the table is just titled: "m-factors for columns of concrete moment frames".

So, I am not clear if that means that all actions of that columns (axial, flexure, shear) should use the m-factor from that table.

Hope that makes sense.

 

[r13]

As far as I can understand is that, under the column and beam tables, there was no "acceptance criteria" provided, thus the actions (for columns and beams) shall be considered "force controlled". If a "m" factor is provided, and is applicable to "force controlled" elements, then you shall use it for all actions concerning columns and beams. Does this make sense?

 

[wannabeSE]

What version of ASCE 41 are you referencing. For ASCE41-13, table 10-10 (couldn't find 10-10a in 2013 edition) is the non-linear hinge properties for beam column joints. Non-linear procedures don't use m-factors. Table 10-13 has the m-factors used for linear analysis of beams. There are 4 conditions, beams controlled by flexure, shear, inadequate development/splicing along span, and inadequate embedment into the beam-column joint.

The m-factors are only used for deformation controlled actions, you won't find a table of m-factors for force controlled actions. I don't know what you are missing. If I had to guess, I'd say look back at the demand, capacity and acceptance criteria in chapter 7.5.2 for linear procedures and understand the different criteria for force controlled versus deformation controlled.

 

[structeng2]

I am using ASCE41-17.

Table 10-13 is more clear on what m-factor to use based on the failure mode. I agree with that.

The equivalent table in ASCE41-13 for columns is 10-9. Interestingly enough - the table in ASCE41-13 is pretty clear with Condition i, ii, iii, and is clearly defined in 10.4.2.2.2.

However, in 41-17, they got rid of these conditions. But, as I am looking at the table in more detail it looks like they have embedded the conditions i, ii, iii from 41-13 into the inequalities of the 41-17 table. (e.g. Vye / VcolOE is determining whether the column is shear controlled or not, which was condition ii, and iii from 41-13).

Thank you all for the discussion, I think I just needed to talk it through out loud.