The following is
taken from the Executive Summary of the Silver Spring MD Transit Center evaluation
report prepared for WMATA. (This report can be found and downloaded at: http://www6.montgomerycountymd.gov/mcgtmpl.asp?url=/content/DGS/DBDC/RegionalProjectPages/SilverSpringProjects/sstc.asp
)
“The evaluation by WDP indicated that significant design
and construction deficiencies have resulted in a structure that will be unable
to achieve the 50 year design service life specified in the WMATA design
requirements without significant repairs and a long-term maintenance program to
address durability problems.
The evaluation by WDP indicated that the overall design
of the SSTC was deficient due to the restrained nature of the structure and the
inability of the structure to accommodate normal thermal movements. The
restrained nature of the as-designed structure was a significant factor in the
observed cracking at the structure.
Significant construction deficiencies were also observed
in the evaluation. The construction deficiencies include omission of
post-tensioning tendons in the pour strips on Level 330, thin concrete slabs,
extensive cracking on the elevated slab surfaces as a result of restrained
shrinkage and finishing problems, exposed and low concrete cover to
post-tensioning tendon ducts at numerous locations, and low entrained air
content in the top surface of the elevated slabs.
Attempts to repair the cracking in the elevated slabs
have been made by the contractor. To date, the repairs have not been effective
in controlling the movement of water through the slabs. Further, the extent of
cracking has increased over time, through the formation of new cracks and the
extension of existing cracks. The cracking in the elevated decks is undesirable
as the cracks allow the ingress of water and other deleterious materials into
the concrete slabs.
The life cycle costs for repair and
maintenance of the SSTC structure will be significantly increased as a result
of the design and construction defects.”
This slab reminds me of peanut brittle. After the first car rolls onto it, it'll be peanut brittle that you can put into a box.
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