Q

US Department 400 Seventh St. S.W
of Transportation Washington, D.C. 20590
Federal Highway ,

Administration
Refer to: HNG-14

Mr. Daniel H. Copeland

Executive Director

Bridge Grid Flooring Manufacturers
Association

231 South Church Street

Mt. Pleasant, Pennsylvania 15666

Dear Mr. Copeland:

This is to summarize the results of several contacts you and your
consultant, Dr. Ahomad Ahmadi, have had with Mr. Benjamin Tang
and Mr. James H. Hatton, Jr., of the Federal Highway
Administration, Office of Engineering, regarding the
acceptability of proposed details for mounting a shaped concrete
parapet on a grid reinforced concrete bridge deck. The principal
issue under consideration was the adequacy of the anchorage of
the "Z" bar connecting the parapet to the deck. The finite
element analysis supplied with your September 8 letter to

Mr. Hatton dispelled our concerns on that issue. Therefore, the
parapet attachment detail shown in the enclosed drawing, which
was forwarded with your November 3 letter to Mr. Hatton, is
satisfactory, subject to the comments below, and acceptable for
use on the National Highway System projects if proposed by a
State highway agency.

The comments we would offer relative to the details on the
drawing are as follows:

o The quantity of steel, both vertical and longitudinal in
the parapet is less than that used in a comparable
crash-tested parapet. However, given that the base of
the parapet is wider in the detail you supplied than was
the base in the tested parapet and that the tested
parapet was not damaged by the testing, we would not
insist upon an increase in the reinforcement except as
indicated in the next comment.


3

etri

2

° In an earlier drawing you provided there was a note that
read, "within 4200 mm on both sides of an [open] joint
in the parapet...and at the end of the bridge, reduce
maximum spacing of vertical reinforcement to half the
shown spacing." While we consider the length along the
parapet over which the reduced spacing of the vertical
reinforcement applies to be somewhat conservative, in
view of the previous comment, the reduced spacing
requirement should be added to the drawing supplied with
your November 3 letter.

o An important factor revealed by the finite element
analysis was that the toe of the "Z" bar is below the
neutral axis of the bridge deck. A special provision
should be developed to ensure that the lower horizontal
portion of the "Z" bar, the toe, will, with proper
consideration for cover, be placed as low in the grid
reinforced deck as permitted by the grid to ensure that
the toe will always be below the neutral axis of the
deck.

° In the finite element analysis, good shear transfer at
the interface between the bottom of the parapet and the
top of the deck was assumed. The construction
specifications should ensure that the contact surface on
the deck is properly cleaned and prepared prior to
placement of the parapet concrete to ensure proper
performance.

If you have any further questions, please feel free to continue
to contact Mr. Hatton.

Sincerely yours,

1 at

Jewry L. Poston, Chief
Federal-Aid and Design Division

i ini tion
Federal Highway Administra os:
HNG-14:JHatton: 366-1329:gm:12-22 95: COPELAND
copies to:
HPD-1 HNG-1 HNG-10 HNG-14

3128 File, 3128 _
Bae aFL-1 HHS-10 HSR-20 HNG-20 HNG-30

3
c and Roadside Design Acceptance Letter B 233


GRID REINFORCED CONCRETE
BRIDGE DECK

#15 @ 300 wo

CONSTR, _JT.
& NOTCH

T
DRIP LEDGE J

FIRST CROSS BAR BENEATH PARAPET OMITTED / —i 89 MAXIMUM DIMENSION FROM FACE OF PARAPET
FOR 4 1/4" GRID FLOOR, FIRST TWO CROSS / TO FIRST CROSS BAR BEYOND PARAPET
BARS OMITTED FOR 5 3/16" GRID FLOORS.

TYPICAL CONCRETE PARAPET DETAIL

1/4" FULL DEPTH GRID REINFO! NN, DETAILS ARE APPROPRIATE FOR 5 3/16"
DEPTH DECK DESIGNS AS WELL
HALF DEPTH GRIDS SHALL BE FULL DEPTH FOR A MINIMUM DISTANCE OF 915 mm FROM THE OUTSIDE EDGE OF

THE DECK
ATTACHMENT DETAIL APPLICABLE FOR ALL OVERLAY TYPES

ALL DIMENSIONS IN mm UNLESS NOTED OTHERWISE
500 ie) 250 500

1 INCH = 500 mm

TYPICAL ATTACHMENT OF CONCRETE PARAPET TO
GRID REINFORCED CONCRETE BRIDGE DECK