SC&RA
JOBSOF THE YEAR
I
none of the longest bridgemoves
evermade, crews fromOmega
Morgan strategicallymoved the
87-year-old SellwoodBridge inPortland,
OR from its permanent concrete supports
to temporary steel piers tomakeway for
anewbridge tobe constructed across the
WillametteRiver.
The 12-hourmove, whichwaswatched
byhundreds of onlookers, was the result
ofmonths of planning andprecise
execution. The SellwoodBridge, at 1,972
feet long, 75 feet high and, 28 feetwide,
is among the state’s busiest bridgeswith
30,000 vehicle crossings eachday.
Once itwas secured intoplace, the old
bridge in its new locationwouldbecome
a temporary routewhile thenew$307.5
millionbridge is built in the original
location. Itwill open in2016.
The jobwas complicatedby the fact that
itwas not a straight-acrossmove. Instead,
the east endof the bridgeneeded tobe
movedonly 33 feetwhile thewest end
had tobemoved66 feet. The entire span
was also shifted two feet east.Omega
Morgan’s team startedplanning for the
project inMarch2012,moved its crew
onsite on January 2, 2013. The actual
bridgemove occurred January 19, 2013.
BothOmegaMorgan andGeneral
Contractor Slayden/Sundt JointVenture
have successfullyused this detour bridge
methodonother projects, according
to the company.OmegaMorgan’s
collaborationwith the general contractor
was critical toproject planning and
public safety. Timingwas a challenge as
only aweekwas allowed to jackup,move
and jackdown the bridge. Tominimize
downtime, the bridgewas jackedup
with traffic on it.OmegaMorgan’s
safetymanagerwas included in every
phase of planning to identify areas of
safety concern and collaboratewith the
contractor’s safetyplan.
Devising a strategy tomove the bridge
inonepiecehelpedwin the contract
after showing that itwould save time,
money andduplicationof efforts.Other
proposals suggested expensive structural
features and extensive staging.
rotation. The bridgewasmovedusing
pushing cylinders at eachbent.Hydraulic
flowwasmetered so that the cylinders
at eachbentmoved theproper amount.
Prior to themove, the skid trackwas
markedoff in tenth-of-a-foot increments
from the startingpoint of the skidbeams.
Theprogress of the skidbeams at each
bentwasmonitored against anoffset
table to ensure that the bridgewas staying
straight andon a radius of the turn.
Temporary approach spanswere
installed at thewest and east ends of the
relocatedbridge to linkHighway 43 in
southwest Portland to S.E. Tacoma Street.
The job started earlyon a Saturday
morning, the spanmoving at a snail’s
pace of about six feet per hour. About 35
crewmembers remainedon the bridge,
operating thenetworkof 50hydraulic
jacks that lifted andpushed the bridge
on ramps to its new location, and
monitoring the truss.During themove
crewsmonitored thepressure gauges and
adjusted the flow rates at each location.
Using survey laser targets, 10GPS
sensors, 30 stress-strain gauges, the team
successfully completed the translation.
■
‘Shoofly’ plan
Theplan involved sliding the aging
bridge on skid gear to thenorthof the
existingbridge and thenmounting it
onnewpiers that hadbeenbuilt in the
river. The bridgewould thenbecome the
“shoofly,” or detour, while construction
beganon thenewbridge.
Engineers used10 sliding jacks, 40
lifting jacks and a central control system
to assure themoveprogressed as planned.
The truss spanwas designed as a
continuous structure rather than a series
of connected spans, which is unusual, but
allowed it tobemoved inone piece.
Inpreparation for themove, crews
removed short spans at the east andwest
ends of the truss span thatwouldnot be
part of thenewdetour bridge.Hydraulic
jacks lifted the truss span several inches
off the old concretepiers, and then
horizontal jacks pushed it on rails along
steel translationbeams linking the old
pierswith thedetour bridge piers.
The layout of the skidbeams and skid
trackwas critical because the track that
was up to1,100 feet apart had tobe set
ondifferent radiiwith the samepoint of
RIGGING$150,000 TO$750,000
Bridge scoot
>51
49
MAY 2014
ACT
OmegaMorgan
OmegaMorgan crewsmoved the old Sellwood Bridge to a temporary location until the new
bridge can be constructed.
