[UPDATE 4:15pm: Looks like Lindblom’s getting raked over the coals for this one. It’s been edited yet again. The Seattle P-I managed to get the story right without all this hassle. Maybe it’s because the P-I doesn’t have a vendetta against Sound Transit?]
[UPDATE 2:57pm: The latest online version of this article is slightly less inflammatory, although still misleading up until paragraph 5. Let’s hope this trend continues going into the print edition.]
These days, when I read a Seattle Times article about Sound Transit, I play a little game – I count the paragraphs before the fearmongering is replaced with the real story. Today I got to 6 before realizing that today’s installment is really about stretching the definition of the word “in.”
Lindblom’s story starts by describing the concrete columns that support Sound Transit’s trackway in Tukwila. The reader is led to believe that the columns are structurally unsound – most of us have seen construction, and are familiar with the concept of using rebar to strengthen concrete. A quick skim of the article is simply scary – this rebar doesn’t meet design specifications?
It turns out this isn’t about rebar at all. It’s about a steel casing, essentially a concrete pour form, for 12′ of the foundation depth (the foundation continues much deeper than that). This casing is left after the pour to add extra reinforcement. Discretionary reinforcement. From the Washington DOT Bridge Design Manual, Section 7.8.2:
“The volumetric ratio and spacing requirements of the AASHTO Guide Specification for LRFD Seismic Bridge Design for confinement need not be met. The top of shafts in typical WSDOT single column/single shaft connections remains elastic under seismic loads due to the large shaft diameter (as compared to the column). Therefore this requirement does not need to be met.”
Because these columns are big, this casing isn’t even actually necessary. There’s a highlight from “grayb” (which I assume is Bruce Gray) in the design memorandum (PDF) so kindly linked by the Seattle Times:
“Because the provision for confinement is discretionary and not prescriptive for large diameter piles, it is the designer’s conclusion that 36ksi steel is adequate for both [10′ and 12′] diameter casings.” [mine]
The headline and the article are blatantly overblown. The grade of steel used in the non-required casing for the columns is lower than it should be. The existence of the 50ksi requirement at all is (from the report) “a detailing exercise at the discretion of the design engineer,” not a structural issue.
You know what all this comes down to? Sound Transit’s engineers dot every I and cross every T, and a reporter that tries at every turn to smear the agency just gets caught with his pants down when he fails to read the reports he writes about.