[Aquinasfan]

A Review of the Central Artery/Tunnel Project's Use of Anchor Bolts on the C05B1 Tunnel Finishes Contract

This is mind-boggling. The structural integrity of the tunnel itself may be compromised:

a letter to MassHighway, B/PB states: “[W]e feel that this practice will not have a detrimental affect on the integrity of the tunnel roof due to the probable loss of the insignificant amount of reinforcing steel." Project documents reviewed by this Office did not contain any evidence of an engineering evaluation performed by B/PB to justify its conclusion to MassHighway that the structural integrity would not be seriously compromised. The structural strength of the tunnel roof may have decreased. If the contractor drilled through or cut a number of adjacent rebars, it could affect the local structural integrity of the concrete. The subcontractors completed approximately 7,000 core drills. Potential public safety issues could exist as a result of the drilling. Despite B/PB’s assurances that no safety issues existed, MassHighway should have obtained and independently reviewed B/PB’s written analysis. This Office has taken the position in the past that the SDC should be consulted whenever a significant change is going to be made in a design or in the construction contract specifications. In this case, the tunnel designers or the SDC for the tunnel finish contract should have been asked to review the decision to cut through the rebar. The SDC, as the Project designer of record, should have an opportunity to comment on all major design changes. The SDC also provides an important check against both the contractor and B/PB. The Project unnecessarily exposes the Commonwealth to financial risk by not involving the designer. The resident engineer for this contract compared the design of the ceiling to a “Swiss watch” because of its complexity. According to the resident engineer, the ceiling design was intricate and extremely difficult to construct, underscoring the need to involve the SDC in any design or specification changes.

[mewzilla]

I thought the ceiling slabs weren't there, though, for any kind of structural support? If so, does this mean that installing the concrete slabs, instead of ceramic tiles say, that the installation might have actually weakened the structural integrity of the tunnel?

[Hemingway's Ghost]

Granted, my engineering "expertise" is limited to the naval, weapons, materials, and electrical engineering courses I took as an undergraduate at Annapolis, but for the life of me, I cannot understand how any engineer would not be concerned with the strength of a concrete ceiling after 7,000 holes were drilled into it, and the rebars giving it extra strength were cut. After reading some of the commentary from civil engineers here on FR, it seems patently obvious that this slab drop-ceiling was not part of the original plan, and that it was designed, engineered, and built almost as an afterthought. If it were not, and this type of exhaust venting was always in scope, hangers for the slabs could have been cast into the concrete ceiling of the tunnel itself---perhaps as part of the rebar, or somehow part of that system.

B/PB has blood on its hands.