Strengthening the Silver Spring Transit Center’s interior beams and girders — a fix recommended more than a year ago by Montgomery County’s engineering consultant — would add another six months to the repair effort and virtually eliminate the possibility of the autumn opening hoped for by officials, the County Council was told Tuesday.
General Services director David Dise, the county official overseeing the problem-plagued project, also said that if repairs are deferred until after the center opens — a possibility being entertained by Metro, which will operate the facility — the work could take a year or more and involve closure of a “significant” portion of the bus and train hub.
The $120 million center was originally scheduled to open in December 2011.
KCE, the firm hired by the county to investigate serious cracking in structural concrete, reported in March 2013 that about 250 concrete beams and girders might be vulnerable to stress from torsion and shear forces caused by hundreds of buses entering the facility each day.
Torsion is the force exerted on concrete by twisting; shearing refers to vertical pressures that could cause concrete to crack or fail.
Dise told the council that KCE’s position has been affirmed by a working group of building experts recruited by County Executive Isiah Leggett and headed by former Lockheed Martin Chairman Norman Augustine. The panel is expected to issue a report sometime in the next several weeks.
But Metro has been reluctant to consent to the work — which would involve the embedding of additional steel supports inside the beams and girders — because of concerns that it would create new damage that could further compromise the building.
Dise said Tuesday that Metro “has questioned whether this work needs to be performed or, if it is necessary, may be deferred until evidence of stress occurs, if at all.”
Metro is basing its hesitancy at least in part on assertions from Parson Brinckerhoff, which designed the center. Parsons vice president Jerry Jannetti said in a recent e-mail that transit center was designed to resist shear and torsion caused by “the equivalent of several fully loaded 18-wheel tractor trailer trucks driving at Interstate highway speeds--loads far in excess of normal operation for this garage.”
Jannetti added that the new layer of latex modified concrete — set to be added this spring to compensate for overly thin concrete poured by contractors — has the added benefit of further increasing the torsional capacity of the beams and girders. Other reinforcement work would be an unnecessary expense.”
The county and KCE, which attributed cracking concrete to flaws in Parsons’ original design, disagree.
Metro sent a representative, government relations officer Charles Scott, to Tuesday’s briefing. But Scott had little to say, only that the agency had received “conflicting reports” on the advisability of the beam and girder reinforcement. Pressed for comment afterward, he walked away from reporters.
For the moment, at least, Metro appears to be leaning toward deferring the work and hoping that signs of shear or torsion stress don’t emerge. If Metro were to want the reinforcment done up front, before opening the center, it would be best to do it before the new concrete is poured, Dise said. But plans for the pour are moving ahead.
The county and the transit agency are negotiating an agreement that would provide for regular independent engineering inspections of the building to look for signs of stress. If they appear, Metro wants to be protected from additional costs with a surety bond that would be put up by Parsons.