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.”