Attachment 02B - Building 240 Slab Rating.pdf

14 York Street, Suite 201 | Portland ME 04101 | T 207.879.1838 | F 207.879.1822 | www.ThorntonTomasetti.com

December 8, 2021

Mr. Seth Bickford Lead Engineer

VA MAINE HEALTHCARE SYSTEM

1 VA Center Augusta, ME 04330

Dear Seth, The purpose of this letter is to inform you of the results of our evaluation and load rating of the elevated concrete slab at Building 240, located at the VA Togus Medical Center campus in

Augusta, Maine.

Description of Building

Building 240 is comprised of a single-story pre-fabricated metal building (PFMB) with clear spanning steel frames. The main floor of the building is an elevated cast-in-place concrete slab, which is designed as a two-way flat plate spanning between cast-in-place concrete columns. The building is supported by a concrete grade beam and pile cap foundation. The building serves as a warehouse storage facility for the hospital, with the storage consisting primarily of permanent racked storage, as well as some movable bins. A portion of the elevated slab is used as a loading dock for the warehouse building. This portion of the slab is designed as a one-way slab spanning between the foundation wall and the reinforced concrete beam along 5-line. Below the main floor is a basement space with a mud slab, and this space is also used for storage.

Available Documents

We understand that structural drawings are not available for this building, however, the VA provided slab reinforcing steel shop drawings. The drawings are entitled Additional Storage

Building, Togus, Maine, Veterans Administration and are dated between August and September

1970. The reinforcing grade, size, orientation and spacing provided on these drawings was used in our evaluation. It should be noted that the drawings do not reference a slab design load and the drawings are not as-built drawings, therefore, actual conditions may vary from what is depicted on the plans. Furthermore, the reinforcing steel drawings do not identify the concrete compressive strength or concrete cover to the reinforcing steel. Both of these variables influence the capacity of the slab.

The existing reinforcing steel shops drawings are included in Attachment B.

Field Investigation

A site visit was performed on November 8, 2021 to conduct a visual assessment of the warehouse slab and to observe non-destructive testing (NDT) performed by S.W. Cole.

The purpose of the NDT was to document reinforcing bar spacing, orientation and depth in specific areas of the 2-way slab. In general, the NDT confirmed the size and spacing of the reinforcing steel that was detailed on available shop drawings referenced above. A description of S.W. Cole’s work and their findings is documented their letter addressed to Thornton

Tomasetti with subject line “Report of Findings” dated November 12, 2021. This document is included Attachment A.

Some minor slab and beam deterioration was observed during our visit to the site. The majority of the deterioration was observed at the loading dock slab, where cracking and spalling was noted. Our opinion is that moisture has been infiltrating the slab at this location from the exposed areas above, likely through shrinking cracks in the top surface of the slab. It should be understood that, in order to achieve the load ratings identified in the following sections of this report, the damaged areas of the loading dock slab will need to be repaired to their original condition.

Structural Evaluation and Assumptions

The slab was rated in accordance with the Direct Design Method outlined in section 13.6 of ACI-

318-08. A finite element analysis was used to further verify the results and calculate the approximate deflections in the slab. The slab geometry and reinforcing layout used in the load rating were based on site observations, details provided in the 1970 shop drawings, and the results of the NDT performed on November 8, 2021.

The following materials properties were used in the slab rating:

a. f’c = 3 ksi (assumed based on typical values for age of structure)

b. Fy = 60 ksi (provided on 1970 shop drawings)

The building foundation, mud slab, columns and grade beams were excluded from this load rating.

Findings and Recommendations

Based on the information discussed above, the main warehouse slab was rated for an available unfactored uniform live load of 240 psf. Additionally, the loading dock slab was rated for an available unfactored uniform live load of 150 psf. Both of these ratings are in addition to the assumed unfactored self weight of the slab.

We recommend that the VA perform structural repairs as soon as possible to the concrete slab at the loading dock portion of the building to prevent further water and chloride infiltration. The damaged concrete will continue to experience corrosion if these areas are not addressed, which will lead to larger areas of damage and further reductions in structural capacity. As mentioned previously, for the areas of the loading dock that are damaged, the rating we have provided is only valid once sufficient concrete repairs have been made. We would be pleased to assist you in the preparation of repair documents, as well as oversight for the construction of the repairs, if desired.

We trust that the information provided addresses your needs at this time, but please do not hesitate to contact us if you have any questions.

Very truly yours, THORNTON TOMASETTI, INC.

Christopher G. Williams, P.E., S.E. Ethan A. Rhile, P.E.

Senior Associate Vice President

Enclosures:

Attachment A – S.W. Cole Report of Findings Attachment B – Existing Reinforcing Steel Shop Drawings

ATTACHMENT A – S.W. COLE REINFORCEMENT SCANNING

21-0731

November 12, 2021

Thornton Tomasetti Attention: Christopher G. Williams, P.E., S.E.

14 York Street, Suite 201 Portland, ME 04104

Subject: Report of Findings Slab Investigation Togus Veterans Health Administration Warehouse Building 240 Augusta, Maine

Chris:

In accordance with our Proposal dated June 8, 2021 and as requested, we made a site visit on November 8, 2021 to perform forensic non-destructive materials testing services on portions of the Warehouse 240 slab.

PROJECT BACKGROUND

We understand that Thornton Tomasetti has been retained to perform an evaluation on the 1970 era structural slab portion of Warehouse Building 240. Part of this evaluation included approximate thickness and perceived reinforcing patterns.

FIELD WORK

Prior to starting our field work, we met on site with our client Christopher Williams P.E., S.E. and Seth Bickford Lead Engineer for the Togus Facilities Management Services. We discussed the locations of scans along with the focused objectives of documenting bar counts in specific load areas for the 2-way slab.

For the first two scans, we were located on the top side of the slab offset from where the additional pier reinforcement is detailed on historic drawings made available. Images from these two scans indicated reinforcement running transverse to the scan orientation approximately 4 ½ to 5-inches down with approximate spacing of 12-inches on center. It appeared that another top layer of reinforcement running parallel with scan orientation may be present at approximately 1 to 2-inches below the top of slab with reinforcement most likely supported by steel chairs. During initial scanning, slab thickness was not known and the scans were performed at a depth of 12-inches with early results inconclusive on thickness.

While performing scans at locations 3 through 7, we observed additional reinforcement within the top 4-inches of the slab in both directions with some indication that an intermediate layer of reinforcement between 5 and 8-inches below top of slab may also be present. Above these columns at the requested scan locations, reinforcement tightened to 8-inches on center and from what we could infer from the scan images, reinforcement at these locations appeared to be #6 bar. Due to the higher concentration of reinforcement, the images were still too cloudy to determine overall thickness and assess bottom layer reinforcement. A measured thickness at a penetration indicated that the subject slab section was likely cast at thickness of approximately 15-inches exists;

further review of the scans substantiated this assessment.

Due to the large concentration of utilities, stored items, and restricted access areas in the basement we were only able to scan limited areas. Scans 8 through 11 were spread randomly through the bottom portion of the slab at areas selected by our client with understood objective being to focus on reinforcement spanning the open areas between columns. In general, these limited scans confirmed bar count noted on the available drawings with all reinforcement hits marked on the slab for confirmation measurements by our client. While onsite we also performed a scan from the bottom side of the loading dock area. The thickness of this scan may be slightly off as the dielectric for this area could vary with unpredictable moisture contents but generally, we found a single bottom mat of reinforcement at 8” on center with a total thickness of roughly 7-inches.

FIELD OBSERVATIONS & FINDINGS

Visual assessment of the warehouse slab sections showed some cracking on the surface.

These cracks appeared more prevalent above columns and where the control joints were cut with many cracks appearing to align with the top mat of reinforcement. Limited cracking was observed on the bottom side of the slab section. The loading dock slab showed signs of spalling both in the scans and visually.

Ground penetrating radar scans from the discussed investigation locations are attached with some mark ups to aid in interpretation along with a sketch showing scan locations and several photographs of the work area.

CLOSURE

Thank you for allowing us to work with you on this project. If we can be of any further assistance or have any questions regarding the findings, please contact either Peter

Phelan or Karl Gimpel at our Gray, Maine office.

Regards, S. W. Cole Engineering, Inc.

Peter Phelan

Construction Services Technician IV

Karl Gimpel

Construction Services Manager kgimpel Karl Gimpel

ATTACHMENT B – EXISTING REINFORCING STEEL SHOP DRAWINGS