architects design group 4131 north central expressway ......joist spanning approximately 48 feet and...

09.18.17

Ms. Melissa Brand-Vokey

Architects Design Group

4131 North Central Expressway, Suite 200

Dallas, Texas 75204

Re: Wylie Public Safety Building

Wylie, Texas

JQ Project No. 3170285

Dear Ms. Brand-Vokey:

JQ Engineering (JQ) performed a limited structural review of the Wylie Public Safety Building located at

2000 North Highway 78, Wylie, Texas on July 11, 2017. The purpose of the review was to observe and

document the general condition of the structure, note any observed deficiencies, perform a structural

analysis of typical framing elements and provide repair recommendations for noted deficiencies. The

structure was damaged by a severe hail storm the previous year and has been vacant since.

The following documents were available for review:

• Original construction documents for “Wylie Complex” produced by Speed Fab-Crete Corporation

International, dated September 23, 1986 (47 sheets);

• Report by McCarthy Architecture dated September 30, 2016 (48 pages);

Our findings are as follows:

Building Description

The Wylie Public Safety Building is a single-story building with an open courtyard in the center (Photograph

1). The structure is approximately 200 feet by 200 feet in plan. Per the original construction documents,

the perimeter and courtyard walls of the building are supported by belled piers with 12-inch wide

reinforced concrete grade beams on 8-inch deep void boxes. The interior columns are supported by

isolated belled piers. The 4-inch thick reinforced concrete slab-on-grade ground floor is on a 4-inch sand

bed with a 6-mil polyethylene moisture barrier. The slab-on-grade is reinforced with #3 bars at 18 inches

on center each way and is cast integrally with the grade beams. The exterior walls are 5-inch thick

loadbearing precast concrete wall panels with perimeter steel channels. Interior HSS 4x4x1/4 columns

support steel joist girders, which span in the north-south direction. Open web steel roof joists spaced

approximately 6’-0” on center span between the exterior walls and interior joist girders in the east-west

direction and support a 1 ½” type F, 22 gauge metal roof deck. Per the original construction documents,

the original roof system consisted of ¾” insulation board covered with a modified bitumen “BRAI” roof

membrane. This original roof has recently been covered with a modified bitumen membrane as a

Wylie Public Safety Building

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temporary solution to the hail damage. The east side of the northeast corner of the building has a canopy

that is assumed to have similar construction to the main structure.

Observations

In general, the structure was observed to be in fair condition. No control joints were observed in the

concrete slab-on-grade and thus the slab has cracked at various locations throughout the building,

especially parallel to the courtyard walls (approximately 2 feet inboard from the courtyard wall), diagonal

cracks from the reentrant corner of the courtyard towards the perimeter of the building and in the

southwest corner near the restrooms (Photographs 2, 3 and 4). The length of most of these cracks

spanned multiple rooms, extending beyond the partition walls. Absent the typical isolation joints around

the columns, cracks were also observed around the bases of the columns in a few locations (Photograph

5). Staining was observed on the floor of Rooms 126 and 127, located on the East side of the building

(Photograph 6). This staining appears to be the result of leaks in the existing roof running down the joists

and dripping down onto the floor below.

Cracks exhibiting efflorescence were observed on the blue-painted top portions of the exterior precast

concrete tilt-wall panels. At a few locations, this cracking was also visible on the interior face of the

concrete walls (Photographs 7 and 8). Deteriorated joint sealant was observed at the vertical joints of

these panels at several locations (Photograph 9). Failed joint sealant also observed at the interface

between the perimeter grade beam and the concrete sidewalk (Photograph 10). Delaminations were

observed at a few locations on the precast panels, with the most severely delaminated location being a

24”x 3” section adjacent to a joint on the North elevation of the building (Photograph 11). Additional

delaminated sections and corroded channels at the panel perimeter were observed at the North and East

elevation entrances, in addition to a delaminated section adjacent to a spall at the East doorway of the

central courtyard (Photograph 12). Corrosion was observed on an exposed drip cap at the corner of a

soffit section at the North elevation entrance (Photograph 13). Further corrosion was observed on the

door frames and drip caps at a few locations (Photograph 14). Staining was observed throughout the

exterior walls with one location at the East elevation exhibiting what appeared to be mold growth likely

caused by moisture (Photograph 15).

Non-loadbearing light gauge metal studs, located beneath the window sills and on the interior face of the

precast concrete walls, were observed to be bent at a few locations (Photograph 16). These slight

deformations appear to have occurred when the drywall and insulation was removed from the walls. The

metal studs also appeared to be partially corroded at a few locations. The metal stud framing is not part

of the structural framing of the building.

Cracking was observed at several locations of the interior non-load bearing partition walls. Several of

these cracks originated from the top corners of the door frames (Photograph 17). A large, vertical crack

was observed at the wall of the women’s restroom (Photograph 18).

Both the open web steel joists and joist girders were observed to have minor corrosion at many locations

(Photographs 19, 20 and 21). Similarly, the cap plates of the HSS columns were observed to have minor

corrosion (Photograph 22). Deformations were observed on the underside of the ribbed metal deck.

Additionally, the underside of the metal deck was observed to be severely corroded in a few locations

(Photographs 23 and 24).


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Ponding water was observed over the modified bitumen roof membrane along the east and west parapet

walls (Photograph 25). Although no ponding water was observed on the drive-through canopy roof,

staining was prevalent on the underside of the canopy (Photograph 26). The scuppers located at the

perimeter of the roof appeared to be clogged with debris at most locations (Photograph 27). Similar to

the sealant failure observed on the tilt-wall panels, gaps were observed in the joint sealant at the parapet

walls that form the protruding saw-tooth section of the roof (Photograph 28).

Analysis

Two typical interior open web steel joists, one typical interior joist girder and one typical interior column

were analyzed to determine allowable live loads. The structural elements were analyzed based upon the

2015 International Building Code for self-weight, superimposed dead load and live load. The following

dead load assumptions were made during analysis: 1 ½” Type F 22 gauge metal roof deck, ¾” rigid

insulation board, single-ply 80 mil Fibertite modified bitumen roof and 10 pounds per square foot (PSF)

for supported ceiling and mechanical systems.

The two typical interior open web steel joists were analyzed based on information contained in the

original construction documents and data gathered at the site. These included the following: Vulcraft

20K4 joist spanning approximately 33 feet and spaced approximately 6 feet on center, and a Vulcraft 28K9

joist spanning approximately 48 feet and spaced approximately 6 feet on center. The typical interior joist

girder analyzed was a Vulcraft 32G 6N 7.2K joist girder spanning 36’-3 ½”. The typical interior column

analyzed was an HSS 4x4x¼, 13’ – 4 ½” tall.

Based on analysis of these structural elements, the existing structure has a maximum allowable live load

of 22 PSF. The 20K4 open web metal joist controlled the allowable live load. Per current code, the typical

required design live load for roofs is 20 PSF, so this result aligns with current design requirements. In

addition, review of the original construction documents noted that the total design load for the structure

was 40 PSF which is typically an acceptable total design load for structures of this type. Atypical loading

such as roof top mechanical units may require isolated reinforcing of the roof structure.

Discussion

Slab-on-Grade Cracking and Movement

Clay soils, common in north Texas, are “active” soils, in that they swell when wet and shrink when dry.

Swelling and shrinking of the subgrade material can result in heaving (upward movement) or subsidence

(downward movement) of the building foundation and sidewalks. Trees around the perimeter also can

cause desiccation of the soils, which results in subsidence of the slab. It is important to maintain a

constant moisture content in the soils around and under these buildings to help minimize the potential

for movement imparted by the shrink/swell cycling.

Slab-on-grade construction typically specifies control joints in the slab; however, no control joints were

installed in the existing slab. In addition, there are no blockouts in the slab around the piers or supported

columns. As the subgrade moves, the slab cracks at random locations rather than on the grid pattern

induced by control joints. These factors have resulted in random cracking in the slab throughout the

structure.


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Most of the cracks observed in the drywall were minor; however, the wide crack in the women’s restroom

appears to be the result of the slab-on-grade heaving as the subgrade swells, possibly caused by a leak in

the plumbing drain lines. Video inspection of the drain lines may be able to identify the location of any

breaches in the lines.

Roof Deck and Membrane

Due to the continuing leaks in the roof, even after the temporary modified bitumen membrane was

installed, it is likely that water has become trapped between the top side of the metal roof deck and the

existing roof membrane system. When the top side of the metal roof deck is uncovered, it should be

inspected for any additional deterioration. It is likely that additional corrosion will be discovered, which

will require additional repairs.

Concrete Wall Panel Modifications

As part of the planned renovation, it is possible that alterations of the existing concrete wall panels to

create additional openings or to enlarge the building into the existing courtyard. Such structural

modifications are normally possible, but typically require the installation of supplemental reinforcing of

the existing concrete wall panels. Further, openings are best be contained within a single wall panel so as

to not require the installation of supplemental columns and associated foundations. As the building

renovation is planned, further review of the existing building will be required so as to fully develop the

required structural modifications.

Recommendations

The following repairs should be completed as part of the building renovation:

1. Rout and seal cracks in slab-on-grade.

2. Remove and replace unsound concrete at exterior precast panels.

3. Clean and coat corroded open web steel joists, joist girders, metal deck, miscellaneous steel, and

exterior doors, frames and drip caps.

4. Remove existing roof membrane and protection board to expose top side of metal deck and

inspect for deterioration of the metal deck.

5. Remove and replace areas of metal roof deck where corrosion was observed from below or where

significant deterioration is discovered during inspection of the top side of the metal deck.

6. Remove and replace deteriorated joint sealants.

7. Video inspect drain lines in the women’s restroom if this restroom and associated underfloor

plumbing is to remain.

8. Remove debris from existing roof scuppers.

9. Trim tree limbs that are overhanging the roof to avoid additional debris collecting in the roof

scuppers.

Our recommendations do not address non-structural items such as interior partitions as we have assumed

that essentially all existing interior finishes will be demolished as part of the renovation. Further, these

recommendations to not address structural modifications related to building renovation or expansion as

the scope of such changes is unknown at this time.


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Disclaimer

The opinions and comments provided in this report are based upon field observations as part of our scope

of services. JQ has ascertained to the best of our ability the visually apparent defects in the building

structure and envelope. However, as field observations were conducted on structures in which the

majority of the building envelope elements are concealed, JQ cannot be responsible for failing to ascertain

deficiencies which were not visible due to the existing conditions in the building. No warranty, expressed

or implied, regarding the condition of the building is intended. In addition, no representation as to the

expected useful life of the building or other components identified in this report is made.

If you have any questions or if we can be of further assistance, please contact us.

Sincerely yours,

JQ Engineering, LLP

Texas Registered Engineering Firm: F-1294

Stephen H. Lucy, P.E. Julie Bolding, P.E.

Partner Senior Project Engineer

Enclosures


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Photograph 1 - Overall view of the South elevation

Photograph 2 - Crack in slab parallel to courtyard wall


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Photograph 3- Cracking at concrete slab-on-grade from reentrant corner of courtyard

Photograph 4 - Close-up of cracking at concrete slab-on-grade


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Photograph 5 - Cracks around base of column (overlaid in red for clarity)

Photograph 6 - Staining on concrete slab-on-grade due to leaking roof


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Photograph 7 - Efflorescence on cracking at top portion of precast concrete panels

Photograph 8 - Cracking on precast concrete wall interior


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Photograph 9 - Deteriorated joint sealant

Photograph 10 - Failed joint sealant between perimeter grade beam and sidewalk


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Photograph 11 - Delaminated concrete at precast concrete panel

Photograph 12 - Corrosion on channel at perimeter of precast panel with delaminated concrete and

deteriorated coating


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Photograph 13 - Corrosion on metal drip cap at edge of soffit

Photograph 14 - Corrosion at door frame and metal drip cap


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Photograph 15 - Mold growth on precast concrete panel

Photograph 16 - Bent light gauge metal studs


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Photograph 17 - Cracking at partition wall above door frame

Photograph 18 - Wide opening in wall of women’s restroom


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Photograph 19 - Corrosion on joist girder

Photograph 20 - Corrosion on open web metal joist


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Photograph 21 - Close-up of corrosion on joist girder

Photograph 22 - Corrosion on HSS column and cap plate


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Photograph 23 - Deformation on underside of metal roof deck

Photograph 24 - Corrosion on underside of metal roof deck


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Photograph 25 - Ponding water on roof

Photograph 26 - Staining on underside of canopy ceiling tiles


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Photograph 27 - Debris in scupper

Photograph 28 - Joint sealant failure at precast concrete panel parapet

architects design group 4131 north central expressway ......joist spanning approximately 48 feet and...

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