7/31/2019 Bridge Crossings No. 12

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BRIDGE

CROSSINGSPractical Information For The Bridge Industry

No. 12, November 1997

WELDLESS

DECKING EXPANDS

BRIDGE OPTIONS

By Ron ald W. Mangon e

No one questions that a huge number of bridges

i n t h e U n i t e d S t a t e s a r e i n n e e d of r e p a ir o r

replacement . Often , however, ma jor r epairs a re not

needed to the supporting steel in the superstruc-

tur e, but rat her t o the bridge deck.

In August 1996, representatives of American

Grid met with West Virginia DOT personnel and

p r e s e n t e d i n f or m a t i on o n a n e w l y d e v el op e d

Weldless Bridge Deck Grating. The product fea-

tures an interlocking assembly, thereby eliminat-

ing the need for welds but maintaining the load

capaci ty and weight advantages of s teel br idgedeck. Because of the lack of welding, the deck can

expand or cont ra ct freely in varying weat her condi-

tions. Also, the deck sections rem ain distortion-free

through fabrication, galvanizing and installation.

Finally, in most applications the weldless system

should be less expensive then traditional welded

grids.

P resen t a t the mee t ing was S teve Fau lkner ,

District 9 Bridge Design Engineer. Coincidentally,

Faulkner was beginning work on a bridge over the

Greenbr ie r River on Coun ty Rou te 43 in Fo r t

Springs, WV. The structure consists of a 160’-10”Pr at t t hr ough t ru ss span with t wo 39’-2” SSWB

(simple steel wide beam) approach spans on the

north approach. The roadway width is 20’-0” curb-

to-curb and consists of a 6¼”-thick reinforced con-

crete deck. Though built on its presen t sit e in 1957,

the truss span was one of three originally erected

32 years ea rlier on U.S. 60 across t he Gau ley River

at Gauley Bridge, WV. The design live load was 2-

H 15 trucks or 76 lb./sq. ft. of roadway plus 15%

live load impact. In 1951, a new bridge was built

a n d U . S . 60 w a s r e l oc a t e d . T h e t r u s s e s w e r e

dismantled and later re-erected at three different

sites th roughout West Virginia.

The existing truss has now been in service for

almost thr ee-quart ers of a centur y and was r ecent-

ly rated as being in fair condition. The truss has

had some repair work done, the most significant

being the addition of structural tees to all stringersand floorbeams in 1978. The bridge deck, however,

was rated poor to critical with some complete fail-

ures of the concrete . Af ter consider ing several

options, including replacing the br idge and r edeck-

ing us ing an exodermic b r idge deck , Fa u lkner

opted for th e weldless deck. The West Virginia pr o-

 ject is the fir st in the wor ld to u t ilize the new sys-

tem.

Re-decking included t he t wo appr oach spa ns a nd

th e tru ss ma in span —a total of 5,145 sq. ft. For th e

approach spans, a 4” on-center main beam open

grid deck with poured concrete haunches was uti-

lized, while a 6” on-center main beam open grid

deck with HP concrete poured haunches was used

for the truss span. The grid was anchored to the

steel beam using Nelson stud welds; the guide rail

posts were at ta ched with out th e use of welding.

The work was completed on four consecutive

weekends beg inn ing Sep tember 12 , 1997 . The

b r i d g e w a s o p e n t o t r a f fi c Mon d a y a t 7 a . m .

thr ough Fr iday at 5 p.m. between installation peri-

ods.

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