Transit Center - Evaluation of Superstructure

SILVER SPRING TRANSIT CENTER

EVALUATION OF SUPERSTRUCTURE (March 15, 2013)

BY

KCE STRUCTURAL ENGINEERS, P.C.

WISS JANNEY ELSTNER ASSOCIATES, INC., AND

WALTER P. MOORE AND ASSOCIATES, INC.

Summary of Their Findings, Recommendations, and Conclusions

(1)                  During and after the pouring of the concrete slabs by Foulger-Pratt Contracting, LLC (2010 through 2011), the County observed certain construction deficiencies that include the concrete slab thickness, cracking and spalling of concrete, and exposed tendons and rebar.

(2)                  County formally notified Foulger-Pratt of defective and non-conforming work on September 22, 2011. County directed Foulger-Pratt to analyze the construction deficiencies and to propose an appropriate remedy.

(3)                  Foulger-Pratt proposed an unacceptable solution to the County to fix the deficient slab conditions.

(4)                  On March 15, 2012 (just over a year ago), Foulger-Pratt, through its consultant Simpson Gumpertz & Heger (“SGH”), recommended the application of waterproofing – a silane sealer, to address only the cracking of the slabs.

(5)                  Unsatisfied with Foulger-Pratt’s response, the County directed Foulger-Pratt to consider further alternatives, namely a bonded 2” overlay proposed by Parsons Brinckerhoff, Inc. (“PB”), the structural engineer of record (“SER”).

(6)                  On June 22, 2012, Foulger-Pratt assured the County that the silane sealer will work, and also provided an additional response, submitted by Simpson Gumpertz & Heger, that effectively dismissed the bonded overlay alternative proposed by PB as unnecessary.

(7)                  Foulger-Pratt represented that the application of silane is sufficient to “achieve a service life approaching or exceeding 100 years”.

(8)                  County remained unsatisfied with Foulger-Pratt’s response to address the deficient slab conditions.  The County concluded that a thorough analysis of as-built conditions of the Silver Spring Transit Center must be performed to ensure the safety of the public and to ensure that the Silver Spring Transit Center is constructed to achieve a 50 year service life.

(9)                  On June 18, 2012, the County retained KCE Structural Engineers, P.C. (“KCE”) to perform a thorough and complete analysis of the as-built structure, including the design, construction, and inspections procedures.

(10)             As of June 2012, the County’s primary concerns included, but were not limited to:

                                                       i.      The thickness of the concrete slabs;

                                                     ii.      Visible evidence of extensive cracking in the slabs, beams, and girders; and

                                                   iii.      Exposed post tensioning ducts.

(11)             County asked KCE Structural Engineers to develop its professional engineering opinion as to:

                                                       i.      The ability of the Transit Center to support the loads it was to have been designed to support;

                                                     ii.      The durability and maintenance of the as-built structure; and

                                                   iii.      The causes of the primary concerns raised by the County and others with respect to design and construction of the Transit Center.

(12)             KCE was also asked to provide a concept for the repairs/remediation so that the Transit Center can be safely placed in operation.

(13)             KCE performed an extensive document review and structural evaluation of the Transit Center’s structure.  To assist with its evaluation and testing of the Transit Center, KCE retained Wiss Janney Elstner Associates, Inc. (“WJE”) and Walter P Moore and Associates, Inc. (“WPM”), who in turn retained other consultants/subcontractors.  Information about the consultants is included in Attachment 2 of the Report.

(14)             KCE and its team of engineers (WJE and WPM) identify deficiencies present in the design, construction, and inspection and testing procedures for the Transit Center.   

                                                       i.      Design - PB designed the SSTC and is the structural engineer of record.

                                                     ii.      Construction – Foulger Pratt is the General Contractor.  It hired Facchina Construction Company, Inc. (“Facchina”) as one of its subcontractors, and it was Facchina that poured the concrete slabs, beams, girders, and columns, and installed the reinforcing steel and post tensioning cables along with its sub-subcontractors.

                                                   iii.      Special Inspection Testing Procedures were conducted by The Robert B. Balter Company, Inc.

(15)             Design deficiencies in the Transit Center that are the responsibility of PB are as follows: 

                                                       i.      Poorly coordinated set of design documents – e.g. interferences between design elements such as mild steel reinforcing, post-tensioning cables, electrical and other embedded items.

                                                     ii.      Over-stressing of design – e.g. post-tensioning stresses exceed actual weight of concrete slabs, thus causing excessive cracking (over-tightening a drum)

                                                   iii.      Over-restraint inherent in design – e.g. concrete slabs are restrained from permitting the natural movement which occurs during curing (hardening) of concrete, thus causing excessive cracking.

                                                   iv.      Failure to incorporate certain WMATA Design Criteria into Contract Documents.

                                                     v.      Expansion joints are inadequate in number and in placement.

                                                   vi.      Concrete pouring and curing requirements not incorporated into drawings and contract documents.

                                                 vii.      Failure to accommodate fire rating requirements – e.g. insufficient concrete cover specified over post-tensioning and rebar in concrete slabs and columns.  Two-hour rating called for in the drawings.  Structure would only receive a one-hour rating as designed.

(16)             Construction deficiencies in the Transit Center that are the responsibility of Foulger-Pratt and its subcontractors are as follows:

                                                       i.      Slab thickness – well below contract requirements, even assuming accepted tolerances (a permissible deviation).

                                                     ii.      Concrete Strength – Contract calls for concrete strength of 8,000 psi; Foulger-Pratt through its subcontractors provided concrete with a calculated strength of 6,970 psi.  The 6,970 psi number represents a holistic view of the overall calculated concrete strength of the facility.  KCE and its team used that number to calculate the load capacity of the Transit Center and as a basis for calculating the loads for the remediation plan.

                                                   iii.      The concrete in deck Pours 1A, 1B, 1E, 1H, and 2C has unacceptable concrete strength based on the ACI 318-02 requirements. Table 10A in the Report shows the slabs with insufficient concrete strength.  Certain slabs do meet the minimum requirements, however, as a whole the facility does not comply with applicable standards or the design requirements.  KCE and its team’s representative compressive strength core results are found in Table 10 (pages 56 and 57 of the Report). 

                                                   iv.      According to KCE and its team, concrete strength is compromised by a combination of several factors:  The addition of too much water to the concrete mix and improper cold curing methods employed by Foulger-Pratt and its subcontractors for concrete that was poured in cold weather.

                                                     v.      Pour Strips on level 330 do not contain post tensioning cables or sufficient rebar to support design loads.  Regardless of other deficiencies on the project, this defect results in an unusable facility – *a significant safety hazard from the failure of the level 330 pour strips.  Without the investigation of the Transit Center completed by KCE and its team of consultants, the County would not have become aware of the significant defects in the pour strips on level 330 unless and until there was a failure of those pour strips during the normal operation of the Transit Center.

(17)             Inspections deficiencies that are the responsibility of The Robert B. Balter Company are as follows:

                                                       i.      The Robert B. Balter Company’s inspections were not completed in accordance with contract documents, WMATA standards, or the Statement of Special Inspections as required by the Montgomery County Department of Permitting Services.

                                                         

                                                     ii.      The Robert B. Balter Company failed to provide adequate inspections, specifically with respect to concrete placement, curing and representative samples testing which likely contributed to concrete strength deficiencies.

(18)             KCE and its team of consultants’ conceptual recommendations and opinion is that remedial actions are required:

                                                       i.      To provide the required strength of certain structural elements;

                                                     ii.      To provide long term durability of the decks and columns; and

                                                   iii.      To achieve the required fire rating of certain columns.

(19)             KCE and its team of consultants propose the following conceptual recommendations:

                                                       i.      Remove and replace existing Pour Strip slabs on Level 330 with appropriately designed and detailed Pour Strips before the overlay noted below is installed.

                                                     ii.      Increase the combined shear and torsional capacity of selected post-tensioned beams on Levels 330 and 350.

                                                   iii.      Enlarge certain columns to provide the required fire rating and increase durability.

                                                   iv.      Increase the combined shear and torsional capacity of selected post-tensioned girders to provide the required shear and torsion capacities.

                                                     v.      Provide a properly detailed concrete overlay on the top surface for the slabs of Levels 330 and 350 in order to provide the required long-term durability.

                                                   vi.      There are two approaches that can be adopted to address these slab concerns:

1.      Design an unbonded overlay system including an appropriately designed wearing course for traffic loads and a properly detailed interstitial waterproofing layer; or

2.      Design a bonded topping slab.

(20)             KCE and its team concludes that the problems at the Silver Spring Transit Center have been caused in varying degrees by errors and omissions of the designer, Parsons Brinckerhoff, Inc., the general contractor, Foulger-Pratt Contracting, LLC and its subcontractors, and the inspection and materials testing firm and Special Inspections Program Special Inspector, The Robert B. Balter Company, Inc.

(21)             KCE and its team of consultants’ professional opinion is that with the conceptual remediation recommendations completed as outlined in their report, the Silver Spring Transit Center can be safely put into service.