May 1, 2015

Mr. Gus Fischer

Dreyfus & Blackford Architects

Via email to: gfischer@db-arch.com

Existing Structure Materials Testing

AC TRANSIT D3 REACTIVATION PROJECT

2016 MacDonald Avenue

Richmond, California

WKA No. 10530.02

As authorized, Wallace-Kuhl and Associates (WKA) has provided materials sampling and

testing services to support evaluation of the existing AC Transit maintenance building in

Richmond, California.

The purpose of our work has been to provide information regarding the masonry wall and roof

slab materials to support evaluation of the building by Buehler & Buehler (B&B), the project

structural engineer. Our scope of work was based on email and verbal discussions with B&B

and the core sampling and testing locations shown on the attached Proposed Repair Plan

sketches prepared by B&B. Our findings are described below.

Masonry Walls

We observed the masonry walls at several accessible locations and verified the rebar

placement with non-destructive equipment (Hilti PS1000 ground penetrating radar (GPR)

machine) and some limited demolition. At the locations where we obtained our core samples,

the rebar in the 8 and 12 inch wide walls was placed in general accordance with the original

construction plans – both vertical and horizontal bars at approximately 16 inches on center.

As requested by B&B, we removed two face shells and a small amount of grout to expose the

extra rebar in the wall pier at Column Lines B @ 2 approximately four feet above ground level.

We found the No. 9 vertical bars and No. 3 ties were present at approximately the spacing

shown in Section G S-206/S-216 of the 1987 building plans.

We observed a significant amount of efflorescence buildup at the inside of the south wall near

core location WC10. It appeared that there was some loss of face shell material where the

efflorescence buildup was greatest.

Existing Structure Materials Testing Page 2

AC TRANSIT D3 REACTIVATION PROJECT

Richmond, California

WKA No. 10530.02

May 1, 2015

We obtained and tested ten core-drilled samples from the masonry walls to observe the

condition of the masonry and verify the strength of the wall materials. The cores were drilled

through the full thickness of the walls except at location WC 5 where the rebar congestion

made it impossible to drill through without cutting rebar. The interior face shell debonded from

the grout during coring at location WC9 (12” thick wall). The core also contained some of the

CMU block web, so a second core was drilled nearby. The interior face shell also debonded at

the second core at this location. Both face shells debonded during coring at location WC6 (16”

thick wall). In general, the grout at our core locations appeared to have been well

consolidated, with only a few small voids observed and little separation cracking at the grout /

CMU block interfaces.

We tested complete cores and portions of the cores for compressive and shear strength (ASTM

C39, C42 and C140; CBC Section 2105A.5). The compressive strength of the composite

cores, grout portion of the cores and CMU face shells we tested all exceeded 3000 pounds per

square inch (psi). The cores we tested for shear strength along the grout / CMU block interface

all exceeded 150 psi in shear strength. For comparison purposes, California Building Code

Section 2105A.5 requires a minimum shear strength of 2.5 x √ f’m or 137 psi for f’m = 3000 psi.

Please refer to the attached Masonry Materials Test Results for core locations and detailed test

results.

Concrete Roof Slab

We observed the roof slab at several locations and located the reinforcing steel with the GPR

machine in the areas where we obtained our core samples. As shown on the plans, there was

relatively little rebar or post tension tendon steel in the center of the bays between columns, but

larger amounts of banded tendons and transverse rebar were present along the column lines.

We observed some displacement (popping out) of the grout used to fill the tendon anchors

along the south side of the structure near the top of the ramp. When we lightly tapped the

grout at one anchor it fell off, revealing rusting of small amount of tendon protruding from the

anchor.

We obtained and tested core samples from the post-tensioned concrete roof slab. The

concrete at our core locations appeared to be well consolidated, with only a few small voids less

roughly 1/8 inch in diameter. The compressive strength (ASTM C39 and C42) of the cores

ranged from 3810 to 5700 psi, with an average of approximately 4680 psi. The average unit

Existing Structure Materials Testing Page 3

AC TRANSIT D3 REACTIVATION PROJECT

Richmond, California

WKA No. 10530.02

May 1, 2015

weight of the core samples was 145 pounds per cubic foot (pcf). Please refer to the attached

Concrete Core Compression Test Results for core locations and detailed test results.

Our representatives replaced the concrete we removed with high strength grout of greater

strength. We replaced the masonry materials in the areas where we cored through the

masonry walls with high strength grout. We replaced the face shells at the front (north) and

east sides of the building with CMU block of similar color and finish.

The information above is based on our exploration, sampling and testing of the building at

several discrete locations. All measurements should be considered approximate and may vary

at different locations within the structure. Please be aware that the conditions and configuration

of the construction materials may also vary throughout the structure.

Please contact me if you have any questions or need additional clarification.

Wallace - Kuhl & Associates

David A. Redford, P.E.

Senior Engineer

Attachments: Proposed Repair Plan Sketches with Core Locations

Photos of Tendon Anchor and Efflorescence

Masonry Materials Test Results

Concrete Core Compression Test Results

STAIR NO.3

STAIR NO.1

ELEVATOR

301

AA A B C D E F G H I

1

2

3

4

5

6

6.3

ma

tch

line

ma

tch

line

1 1/2" separation joint

South WingNorth Wing

4'

- 0

"4

' -

0"

add steel angle sheartransfer conn. alongshear walls pertyp all walls

provide additional steeljamb ea side of opngper typ

4' - 0" 4' - 0"

4'

- 0

"4

' -

0"

typ

typ

typ typ

1

SSK-08

1

SSK-05

JOB

JOB NO.

CLIENT BY SHEET NO.

DATE

BUEHLER & BUEHLERSTRUCTURAL ENGINEERS, INC.

600 Q St., Suite 200

SACRAMENTO, CALIFORNIA 95811

AC TRANSIT

2014-045500 Jan 23, 2015

- JDH SSK-03

1" = 20'-0"Proposed Repair Plan

Provide Cores at 1stfloor wall

- Indicates proposed location of concrete roof slab core testing

- Indicates proposed location of CMU wall core testing

H I J K L M N O P Q

1

22

3

4

5

6

6.3

R

5.2

6.1

ma

tch

line

ma

tch

line

1 1/2" separation joint

South Wing

22' - 3

"

4' - 0" 4' - 0"

typ typ

4' - 0" 4' - 0"

typ typ

4' - 0"

typ

typ

4'

- 0

"4

' -

0"

add steel angle sheartransfer conn. alongshear walls pertyp all walls

anlong line 5.2,provide slip condalong wall lentgth

provide new micropileFDN ea end of line Rwall per

1

SSK-05

provide additional steeljamb ea side of opngper typ

1

SSK-08

1

SSK-05

1

SSK-07

install shotcretealong Line R wallper

A

SSK-06

A

SSK-06

indicates added fiber wrap in east/west dir, typ

indicates added fiber wrap in north/south dir, typ

JOB

JOB NO.

CLIENT BY SHEET NO.

DATE

BUEHLER & BUEHLERSTRUCTURAL ENGINEERS, INC.

600 Q St., Suite 200

SACRAMENTO, CALIFORNIA 95811

AC TRANSIT

2014-045500 Jan 23, 2015

- JDH SSK-04

1" = 20'-0"Proposed Repair Plan

AC TRANSIT D3 REACTIVATION PROJECT

Richmond, California

WKA No. 10530.02

May 1, 2015

EFFLORESCENCE PHOTOS

Inside of wall at Core Location WC10

Detail of efflorescence with slight loss of material at CMU block face

AC TRANSIT D3 REACTIVATION PROJECT

Richmond, California

WKA No. 10530.02

May 1, 2015

TENDON ANCHOR PHOTOS

PT tendon anchors at south side near top of ramp

PT tendon anchors showing rust and displacement of grout cover

AC TRANSIT D3 REACTIVATION PROJECT WKA No. 10530.02

May 1, 2015

MASONRY MATERIALS TEST RESULTS

(ASTM C39, C42 and C140)

Page 1 of 2

Core

No.

Approximate

Location Dia.

Capped

Length Area

Correction

Factor

Maximum

Load

Compressive

Strength

(in) (in) (in2) (pounds) (psi)

Composite Masonry

Cores

WC1 8” wall, Line R @ 5.4 3.71 7.7 10.8 1.00 42,700 3950

WC2 8” wall, Line R @ 5.9 3.71 7.7 10.8 1.00 38,500 3560

WC8 8” wall, Line 6 @ H.7 3.71 6.0 10.8 0.97 42,400 3810

WC3 12” wall, Line Q @

3.5 3.71 11.7 10.8 1.00 44,500 4120

WC4 12” wall, Line 2 @ M 3.71 11.7 10.8 1.00 48,400 4480

Average 3980

Grout Cores

WC5 16” wall, Line 2 @ D 3.71 4.25 10.8 0.91 55,200 4650

WC6 16” wall, Line 2 @ B 5.64 11.2 25.0 1.00 95,200 3810

Average 4230

CMU Block

Coupons

Length

Thick-

ness Area

(in) (in) (in)

WC6A 16” wall, Line 2 @ B 5.02 1.25 6.3 NA 38,770 6150

WC6B 16” wall, Line 2 @ B 4.83 1.18 5.7 NA 30,420 5340

Average 5750

AC TRANSIT D3 REACTIVATION PROJECT WKA No. 10530.02

May 1, 2015

MASONRY MATERIALS TEST RESULTS

(CBC Section 2114A.9.3)

Page 2 of 2

Core No.

Approximate

Location Dia. Area

Maximum

Load

Shear

Strength Failure Description

(in) (in2) (pounds) (psi)

Grout / CMU Block

Shear Strength

WC7-A 8” wall, Line 6 @

C.6 3.71 10.8 3830 350

Partly at grout/face

shell interface and

partly in CMU

WC7-B 8” wall, Line 6 @

C.6 3.71 10.8 4620 430

Partly at grout/face

shell interface and

partly in CMU

WC9-A 12” wall, Line 6 @

M.5 3.71 10.8 1750 160

Along interface

between grout and

face shell

WC9-B 12” wall, Line 6 @

M.5 3.71 10.8 1750 160

Along interface

between grout and

face shell

WC10-A 8” wall, Line 6 @

Q.3 3.71 10.8 3800 350

Partly at grout/face

shell interface and

partly in CMU

WC10-B 8” wall, Line 6 @

Q.3 3.71 10.8 3810 350

Partly at grout/face

shell interface and

partly in CMU

Average 300

NOTES: Masonry materials testing was performed on cores and portions of cores that

were drilled horizontally through the walls.

One face shell debonded from Core WC8 during coring. The Composite

Masonry Core strength test was performed with one face shell and grout.

The face shells debonded from Cores WC5 and WC6 during coring, so the grout

and CMU block were tested separately.

The cores were obtained 3 to 4 feet above ground level except Cores WC7 and

WC8, which were obtained about 3 feet above the mezzanine floor.

AC TRANSIT D3 REACTIVATION PROJECT WKA No. 10530.02

May 1, 2015

CONCRETE CORE COMPRESSION TEST RESULTS

(ASTM C39 and C42)

Page 1 of 1

Core

No.

Approximate

Location Dia.

Capped

Length Area

Correction

Factor

Maximum

Load

Unit

Weight

Compressive

Strength

(in) (in) (in2) (pounds) (pcf) (psi)

Roof Slab

SC1 Line C.5 @

3.5 2.75 4.90 5.94 0.98 34,600 147 5700

SC2 Line J.5 @

3.5 2.75 4.65 5.94 0.98 27,400 145 4520

SC3 Line O.5 @

4.5 2.75 4.81 5.94 0.98 23,100 144 3810

Average 145 4680

NOTES: The slab concrete contained nominal 1-inch max size, normal weight aggregate.

The cores were drilled vertically down into the slab. Where necessary, the top

and/or bottom of the cores were trimmed with a wet saw prior to testing for

compressive strength.