Pier/column development length
Pier/column development length
(OP)
A sr. engineer has been checking a set of plans that I had done a while back and questioned the development length of the reinforcing in the column to the pier cap. I used the basic development length, but did not include any modification factors. Would you use the basic development length or apply the factors to it? No damage has been done, just a QC check, i'm just frustrated that I would have missed that....





RE: Pier/column development length
RE: Pier/column development length
Even if you don't use the modification factors, you should make it clear to a checker that you know you're not using them and the rationale behind it. A senior engineer will not know what you were thinking "a while back."
RE: Pier/column development length
RE: Pier/column development length
As for the two sets of plans that show it both ways. You should make the assessment of whether the details are correct. Like yourself, I spend endless hours reviewing design drawings 'by others' to find an industry standard ways of doing things. Personally I hate seeing two sets of plans design the same element differently, particular when the plans are coming from the same office.
RE: Pier/column development length
My present memory (though hazy) was that the development length was increased even beyond the "factors", since EQ was always controlling (in my limited experience) and it was necessary that the plastic moment functioned.
RE: Pier/column development length
RE: Pier/column development length
If BridgeEI's bridge is in a seismic zone (SDC C or D) and you are applying AASHTO's Guide Specifications for LRFD Seismic Bridge Design (2009), then your requirement for development length should be based upon section 8.8.4 of that guide specification. Interestingly, you find that the embedment length is smaller than what is recommended by the AASHTO LRFD Bridge Design Specifications. However, it is recommended that the column longitudinal reinforcing be exteneded "as close as practically possible" to the face of the cap beam.
RE: Pier/column development length
I have shied away from specifying epoxy coated bars because my understanding was that they needed special handling and inspection. My understanding was that if the coating is damaged the bar can corrode at an accelerated rate where it was damaged. I specified galvanized bars in the few and minor instances where additional protection was required.
However, I suspect galvanized bars are likely cost prohibitive (for other than minor use), and the sacrificial coating may be depleted by continuous ionic exposure.
I remember being very conservative with plastic moment design. Also, I take the AASHTO code with a grain of salt and was sorry to see the old spec's go.