F i r s t
P e r s o n
downstream of Hoover Dam, this structure is eloquently anchored into the sheer
rock faces of the historic Black Canyon.
The main segment of the bridge, which is
a twin-rib concrete arch and steel composite structure, spans approximately 1,060 ft
from wall to wall. Over the course of two
weeks in the middle of January 2013, three
professional engineers and three engineers
in training—all professional rope access
technicians—from Stantec rappelled,
climbed, ascended, traversed, and crawled
over, under, inside, and around every inch
of this structure to thoroughly document
the bridge’s structural condition.
The National Bridge Inspection Standards were established in 1968 by Congress following the tragic collapse on December 15, 1967, of the Silver Bridge,
which connected Point Pleasant, West
Virginia, with Gallipolis, Ohio. Since
then every bridge structure, whether of
the size of the Golden Gate Bridge or as
small as a 20 ft clear span culvert in a rural
locale, must be inspected at intervals not
to exceed 24 months unless the Federal
Highway Administration rules otherwise.
The Hoover Dam Bypass is considered
one of the newest national monuments (al-
High
Over
Hoover
Dam
Rising 880 ft above the Colorado River, the majestic Hoover
Dam Bypass poses formidable challenges to bridge inspectors.
And that is why the rope access technicians who performed a
thorough inspection of the bridge in January are invaluable.
By Ryan Nataluk, P.E.
[ 4 8 ] C i v i l E n g i n e e r i n g o ct o b e r 2 0 1 3
As Nicholas Cioffredi, P.E., a
senior bridge inspection engineer
for Stantec, notes, “You’re so
focused on the task at hand,
inspecting this engineering marvel,
doing your job, and making sure
that you’re safe that it can take
a while to stop long enough to
absorb the exposure of it all. It’s
not often you get to hang devoid of
contact with any structure while
looking down on the Hoover Dam.”
s ta n t e c , a l l
Bridge, often referred to as the Hoover Dam Bypass,
is a very large, complex, and strategically important structure that carries U.S. Route 93 between Nevada and Arizona over the Colorado River. (See “Engineering’s Newest
Marvel,” by Dave Zanetell, P.E., M.ASCE, David Goodyear,
P.E., S.E., P.Eng., M.ASCE, Jeff St. John, P.E., M.ASCE, Brian Lomax, and Danny Sullivan, Civil Engineering, October
2011, pages 56–65, 86–87.) I can vividly remember the
awe and inspiration I felt the first time I viewed this structure. I was at the Hoover Dam observation area, and it was
shortly after Stantec had been selected by the Nevada Department
of Transportation (NDOT) to perform statewide inspections that
would include this marvel. While looking at the bridge with a
dropped jaw that day, I thought about my bridge inspection career
and realized that this is why we specialize in condition assessments
and rope access. In less than four months from that date, my team
and I were rappelling down to the arch for the first time to begin
our inspection using industrial rope access methods.
Rising 880 ft above the water surface of the Colorado River approximately 30 mi southeast of Las Vegas and 1,500 ft
photocredit goes here
he Mike O’Callaghan–Pat Tillman Memorial
photocredit goes here
T
V
To view a video of the project, visit our digital
edition at www.asce.org/cemagazine,
or view the app at www.asce.org/ceapp.
though it has not officially been designated as such), and this 1,905 ft long structure is being inspected at intervals of two
years or less by NDOT-approved inspectors. The personnel and engineering teams
who inspect and evaluate our nation’s infrastructure are very specialized civil and
structural engineers and technicians who
sometimes receive little recognition for the
important tasks they perform. Their basic
training and certification are mandated by
law through the Code of Federal Regulations
(title 23, part 650) and are overseen by the
Federal Highway Administration, but not
all bridge inspectors are “created equal.”
In the early 1980s only a handful of engineers would have had the audacity to
tell a client that they were going to utilize
ropes and harnesses to perform an “inspection” and believe the client would actually
hire them. Just 30 years later this practice
has taken firm hold in the United States
and is achieving wider acceptance and
o ct o b e r 2 0 1 3
C i v i l E n g i n e e r i n g [49]
The personnel and engineering teams who
inspect and evaluate our nation’s infrastructure
are very specialized civil and structural engineers
and technicians who sometimes receive little
recognition for the important tasks they perform.
Ryan
Nataluk’s
Account:
T
[ 5 0 ] C i v i l E n g i n e e r i n g o ct o b e r 2 0 1 3 0885-7024/13-0007/8-0056/$30.00 per article
photocredit goes here
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practice each year. At this time it is estimated that approxi- order to maintain a statewide inventory of this stature, inspecmately 100 professional engineers—and probably twice that tions must be thorough, must be on time, must meet Federnumber of inspection technicians—utilize rope access to al Highway Administration metrics, and must provide the
perform bridge inspections in accordance with the National vital information—including essential maintenance recomBridge Inspection Standards. This pool of specialized profes- mendations—required to prolong service life. The NDOT’s
sionals provides hands-on inspection of the most difficult-to- exceptional attention to public safety complements in an imreach locations on any bridge to better provide owners with a portant way the safety-driven nature of the work executed by
teams like ours.
clear, comprehensive evaluation of the structure.
In June 2012 we were selected to assist the NDOT strucWithin the state of Nevada, the NDOT is responsible for
managing the inspection of 1,972 public bridges owned by tures staff with the inventory, inspection, and load rating of
state and local agencies. Of that total, 1,116 are owned sole- Nevada’s bridges. The selection process followed the NDOT’s
ly by the state, and the NDOT is responsible for maintaining standard request for proposals process and featured competithem. State-owned (“on-system”) structures are typically lo- tive submissions by many nationally recognized engineercated on the national highway system or are on
ing firms. During the selection process, the
state or interstate travel routes, whereas locally Steve Stanley, a bridge and NDOT was specifically interested in the qualiowned (“off-system”) structures typically car- construction inspector for fications of the inspection team, the current
ry locally owned city and county roadways. In Stantec, was a member of and past inspection projects performed by that
comparison with other states and the District of the core Stantec team, all team, and the team’s overall rope access inspecColumbia, Nevada is routinely ranked as hav- of whom are professional tion capabilities. These considerations were
rope access technicians.
important to the NDOT during the selection
ing one of the best inventories in America. In
hroughout my adult life I have
taken great pleasure in adventuring on some of North America’s
largest mountains, dropping into
some of the deepest caves, and scaling a handful of the tallest and most
technical rock walls around. I certainly don’t consider myself to be specifically gifted at any of these activities,
but these goal-oriented, adrenalinepumping excursions are generally
how I have enjoyed my spare time
over the years. When I first discovered, in 1998, that I could utilize my
engineering training in conjunction
with my mountaineering, caving, and
rock-climbing skills, I could hardly believe it. I must have said a thousand times
or more since then, “You mean I get to
rappel, ascend, and climb this (bridge,
building, tower—whatever) and you’re
actually going to pay me for what I find
and document?” I can truly say that I love
my job....most of the time. I say “most
of the time” so as not to give an unreasonable expectation to any engineer interested in bridge inspection. It has its glorious
days, and it has its not-so-glorious days.
Inspecting the Hoover Dam Bypass on
rope is a privilege, and I feel honored to
have done so.
The professional work that my team
and I performed for the Nevada Department of Transportation (NDOT) this
past January holds many similarities to
my interests outside of work: extensive
training, detailed planning, mitigating
dangers, taking small things seriously,
teamwork, and thinking safety! I am a
registered professional engineer in several states, including Nevada and Arizona,
and serve as the project manager and lead
bridge inspector for this statewide inspection project for the NDOT. With respect to any project, I feel a responsibility
to fully ensure the team’s well-being and
overall project success for the team and
the client. First and foremost is the safety of my team members. For this work,
I fully knew that my team was ready
and had all of the professional inspection experience and rope skills necessary
to complete this work to the NDOT’s
complete satisfaction. I also knew that
the physical environment in southern
Nevada can be extremely harsh to even
the most honed human body. Temperatures in the summer can rise to 120ºF
and be so dry that the wind will suck
every drop of moisture from your skin
and lungs. Fortunately, the inspection
this year took place in January, and conditions were more favorable than in, say,
July, but many dangers still existed. The
two things that worried me the most
were dehydration and fatigue deriving
from long, physically demanding days in
high temperatures and hot, strong wind.
Lucky for us, Mother Nature was fairly
temperate during our visit, and the team
was able to complete the objectives like
the pros they are.
When conducting work outside of
the office within Stantec, our mandatory
practice is to have on-site daily preinspection meetings to discuss the day’s work,
review safety protocols, review the inspection plan, and gauge the team’s physical
and mental state. We want to discuss and
review everything that could potentially
take place and ensure each team member
knows his role and responsibilities.
I have climbed hundreds of bridges
and structures in my career, but it would
be a lie to suggest that I did not have some
apprehension the first time I rappelled off
this bridge. I must have checked my anchors, harness, and gear at least 10 times
before leaving the bucket of the NDOT’s
underbridge inspection unit to embark
on the 750 ft rebelay 880 ft off the sur-
face of the Colorado River. This technique is very handy to utilize in the
inspection of truss bridges, arches,
and other structures that require
both vertical and horizontal movement to complete the job.
One full rebelay between spandrel columns took upward of four
hours. Therefore, once an inspector left the deck of the bridge, he
was going to be “on rope” for quite
a while. A lot can happen in four
hours, and this was my greatest concern for the team. The temperature
can rise, the wind can pick up, a
thunderstorm can roll through, or
a person can overexert himself. Each
team member had to be prepared
for just about anything, including
carrying all of the water and food
required. Escape and rescue plans needed to be ready for execution at any moment. I am glad to report that there was
not one single incident on this project,
and the team performed flawlessly over
the two-week inspection.
No project can proceed and end
smoothly without the teamwork and
cooperation of all members and stakeholders. Each project requires the collaborative, dedicated effort of several
agencies and teams. This project benefited from exceptional commitment
from the NDOT divisions dealing with
structures, underbridge inspection vehicles, and traffic control; the Hoover
Dam Police Department; and the Nevada Highway Patrol. Our team also
benefited from the advanced rescue
training and on-site support provided
by Gemini Rope Access Solutions. All
of these partners and their roles are critical to project success, and they work in
conjunction with our core Stantec team:
Nick Cioffredi, Frank Block, Tom Ritz,
Matt Bialowas, and Steve Stanley. What
I’ve come to appreciate in working with
these gentlemen is the trust and connection we share as climbing partners.
They are sincere friends and dedicated
members of the same inspection team
and are uniquely qualified to perform
this specialized work for agencies like
the NDOT throughout the nation.
Ryan Nataluk, P.E., is a senior structural
engineer and the bridge inspection program
manager for Stantec Consulting in Denver.
o ct o b e r 2 0 1 3
C i v i l E n g i n e e r i n g [51]
Frank Block’s
Account:
We were fortunate to have
inspected and evaluated some
of the largest and most iconic
bridges in America. Our team,
composed of professional engineers and engineers in training, has evaluated structures
ranging from New York City’s
George Washington, Queensboro, and Brooklyn bridges to
small timber bridges in rural locales. The team selected to inspect the Mike O’Callaghan–
Pat Tillman Memorial Bridge
is the same team that inspected the structure that replaced
the Silver Bridge. Our collective experience gives us insight
into several key areas of bridge
inspection, including perspective on the nation’s structural
history and future through our
detailed involvement in design,
fatigue, retrofits, and failures.
This, combined with our experience in evaluation, access planning, and assessment of material
defects and properties, qualified
our team for this momentous inspection. Just as important, all
members of our team of engineers and technicians hold certifications in specialized access
and inspection methods ranging
from rope access to underwater
diving to nondestructive testing.
orking at extreme
heights may appear to
most to be an exercise in
lunacy, but in actuality it is safer
than crossing a busy street in a
major U.S. city. Utilizing rope
access techniques to perform
work on the nation’s highway
process because of its need to maintain
“I have climbed hundreds of bridginfrastructure is a much safer practice
es and structures in my career, but it
public safety and preserve Nevada’s stathan placing an engineer, a technician,
would be a lie to suggest that I did not
tus of having one of the best-ranked inor a worker, along with mechanical
have some apprehension the first time
ventories in the country. Additionally,
equipment, in a traditional work zone.
I rappelled off this bridge. I must have
the NDOT must inspect and maintain
Our clients also find that it’s more cost
checked my anchors, harness, and gear
not only such “typical” bridge and culeffective. According to recent data comvert structures as concrete and steel at least 10 times before leaving the buck- piled by the Federal Highway Adminiset,” says Ryan Nataluk, P.E., Stantec’s
overpasses, underpasses, box culverts,
tration’s Work Zone Mobility and Safety
bridge inspection program manager.
and pipes but also such structures in
Program, “There were 87,606 crashes in
its inventory as the Hoover Dam Bywork zones in 2010. This is 1.6 percent
pass and the Galena Creek Bridge,which require more ad- of the total number of roadway crashes (5,419,345) in 2010.
vanced engineering and access techniques to facilitate in- Most crashes in work zones do not lead to fatalities. In 2010
depth evaluations.
work zone crashes, 0.6 percent were fatal crashes, 30 percent
[ 5 2 ] C i v i l E n g i n e e r i n g o ct o b e r 2 0 1 3 0885-7024/13-0010-0048/$30.00 per article
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W
T
he opportunity to inspect the
Mike O’Callaghan–Pat Tillman Memorial Bridge was a once-in-a-lifetime experience (although I’m hopeful
for a return trip in 2015). I can remember
first hearing that we were awarded the
contract for statewide bridge inspections.
I was very interested in travelling around
a state in which I had spent little time.
I then came to realize the scope
of the project and that our inspections would include the recently completed Hoover Dam
Bypass structure. My interest
quickly turned into a mild obsession. I began to pore over Internet photographs and articles
on the bridge while thoroughly
conveying my interest in this inspection to the decision makers
assembling the inspection team.
It is only the most iconic and
nationally recognized structure
since the Golden Gate!
The weeks leading up to the
inspection were filled with planning the inspection sequence,
rounding up ropes, organizing
equipment, and coordinating
with the Nevada Department
of Transportation (NDOT) and
police staff while completing
work on other inspection projects. Add in a few last-minute
time constraints to the daily
schedule, the possibility of high
winds, and the overwhelming obligation to provide our best, and you might
be able to grasp the anxiety as the first
day of inspection neared. But the long
hours and apprehension were more than
justified the first time the underbridge
inspection vehicle (UBIV) bucket lowered from beneath my feet and left me
suspended 880 ft above the canyon floor.
The inspection itself unfolded almost flawlessly. After meeting and developing a level of understanding with
the NDOT traffic control staff, the UBIV
operators, and the Hoover Dam Police Department, our job as inspectors
turned into directing the resources of
these teams in an efficient manner in
order to set up anchors and get as many
inspectors as possible “on rope” evaluating the structure. Our experience enabled us to create a detailed outline of
which ropes would be needed to access
each column and arch segment, and our
estimates of the time that would be required to complete each inspection enabled the team to share equipment and
put as many as five inspectors on rope
simultaneously. As the team member in
charge of planning the rope allocations
and inspection sequencing, this was
my primary concern. I was also a little
concerned about how my body would
physically hold up for two weeks during which I would regularly be making
rope ascents of nearly 300 ft. I believe I
ascended approximately 1,150 ft of vertical rope during the inspection, nearly
the length of four football fields!
Of course, there will always be a
few barriers to climb over with inspections like this (pun intended). During
the fourth day of the inspection, wind
speeds in the canyon gusted in excess of 25 mph, essentially grounding
the UBIVs, our primary means of access to the superstructure. Fortunately, the southeast corner of the bridge is
shielded by a large rock outcropping
that reduced the wind to an acceptable
15 mph. This enabled three inspectors
to access the pier columns, abutment,
and superstructure at the east end. The
second team of three inspectors, however, was left without means of UBIV
retrieval from the arch interiors. In order to regain terra firma, a rebelay system was devised and anchored over the
bridge railing and down to the top of
the south arch rib below. The team had
gained access inside the hollow arch ribs
earlier in the morning, set anchors and
ropes, and descended through the interiors of both ribs for the purpose
of performing a complete interior inspection meeting all confined-space entry requirements.
The work was labor intensive, but the work setting was
incredibly rewarding. Each
time I stepped into the UBIV
bucket and rode out over the
bridge rail of this iconic structure, I couldn’t help but be
overcome by a state of pure
wonderment at the beauty and
grandeur of the Black Canyon
and the Hoover Dam spread
out before me. This, coupled
with the adrenaline from the
incredible height at which I
was suspended and with the
unsettling, somewhat fitful
motions of the hydraulic platform, made for a nervously euphoric experience. The best
by far was each time the UBIV
platform pulled away and left
me hanging on my rope, away
from the roar of the diesel engines and traffic of the bridge deck and
alone with my spandrel column and
the incredible view around it. I’ve never been so careful to check my rigging
and safety backup as I was each time
I inched gingerly toward the bottom
edge of the arch and then below into
the sea of air extending 880 ft to the
river below. There’s something instinctive that tells you, “You shouldn’t be
here—get back on solid ground.” But
at the same time, the rush is too good
to pass up. Of course, these sensations
are placed quickly in check with the reminder that “I have a job to do.”
Frank Block, P.E., A.M.ASCE, is a project
engineer for Stantec Consulting in Denver.
o ct o b e r 2 0 1 3
C i v i l E n g i n e e r i n g [53]
T
he anchors were set. We
tugged and pulled our anchor
slings every which way from the
safety of the underbridge inspection vehicle bucket and then checked to make
sure there was no chance of movement.
There wasn’t. Still, I’d be lying if I said
there wasn’t a moment of relief that
first time the bucket dropped out from
underneath me and I was floating, the
Colorado River 880 ft below.
The first time I was “on rope” on this
structure I was out for four hours. And
once you’re on rope, you’re on rope.
Nobody’s going to come get you. Nobody’s going to come and hang out.
On Hoover, we were actually on
four ropes most of the time. You have
to have ropes attached to both ends of
the span so you can maneuver along the
bridge length. You pull on one and release the other so you can position yourself where you want. It takes a little bit
of acrobatics, I guess.
It might have been the morning of
the third day on rope before I stopped
and turned around to face the chasm
below and realized where I was. Everything was very slow and surreal for
a moment. I couldn’t help thinking,
“What an amazing privilege!” That’s
were injury crashes, and 69 percent were property damageonly crashes.” If you compare these statistics with the 0.0
percent of fatalities connected and associated with the use of
technical rope access work, you can clearly deduce that rope
access work is very safe. That safety is also enjoyed by the
traveling public. Not only is our work keeping the structures safe for travel, but rope access also enables us to work
unnoticed. More often than not, motorists do not see us and
therefore are not distracted by us.
In addition to safety, rope access provides an economical
way for owners to evaluate such assets as bridges, buildings,
dams, tanks, and towers. In most situations there is no need
[ 5 4 ] C i v i l E n g i n e e r i n g o ct o b e r 2 0 1 3 when I realized that our job has its
perks.
You’re so focused on the task at
hand, inspecting this engineering marvel, doing your job, and making sure
that you’re safe that it can take a while
to stop long enough to absorb the exposure of it all. It’s not often you get to
hang devoid of contact with any structure while looking down on the Hoover
Dam.
We always say, “There’s no glory in
bridge inspection,” but Hoover was a
glory job.
Nicholas Cioffredi, P.E., is a structural engineer and senior inspector for Stantec Consulting in Denver.
for the costly endeavor of shutting down traffic lanes for a fullblown traffic control setup. Additionally, there is little need
for expensive mechanical equipment and specialized staff to
lift or suspend the engineers or workers. A growing proportion of the rope access technicians in the United States and
Canada—whether they perform inspections, maintenance,
window washing, or other vertical work—are members of
and certified by the Society of Professional Rope Access Technicians. The organization’s mission, according to its website, is to “advance the safe use of rope access through education, developing standards, and administering certifications.”
Stantec has nearly 20 professional engineers and engineers in
Tom A. Ritz, P.E., a senior
structural engineer for
Stantec, is “on rope”
during the inspection of
the Hoover Dam Bypass.
photocredit goes here
Nicholas
Cioffredi’s
Account:
o ct o b e r 2 0 1 3
C i v i l E n g i n e e r i n g [55]
training who have been trained and certified by this group.
What type of engineer chooses this line of work? Consider the composition of our team: all of our rope access personnel are full-time bridge engineers. We have assembled a
team of engineers who have parlayed professional and recreational passions into a profound resource for public safety.
When accessing remote, hard-to-reach locations, we are able
to assess the significance of defects while “on rope.” That’s
why our team is composed exclusively of bridge engineers
with extensive inspection, design, and analysis experience.
We need to know what we are evaluating. And we like being
able to see details and defects up close. Most engineers never
have that opportunity. Travel is an inherent part of inspection, and finding senior engineers who are passionate enough
about bridges, preserving public safety, and assisting agencies to leave home for days on end isn’t always easy. We train
extensively with our gear and participate in rescue scenarios
so that it all becomes second nature to us. We like the long,
hard days on rope when on the job. Not all
members of our rope access team were initially climbers, but all have a love of adventure, the outdoors, and bridge engineering.
Climbing isn’t always clean and fun either;
in fact, more often than not, we encounter
debris, bird waste, and cockroaches.
Planning an inspection of a structure on
the scale of the Mike O’Callaghan–Pat Tillman Memorial Bridge begins with a solid
understanding of the structure’s design:
what to look for, where to look for it, and
which access to use. The Hoover Dam Bypass is constructed primarily of reinforced, cast-in-place, and
precast concrete elements with the addition of steel tub girders that support the deck across its 16 spans. Each of these
materials, as well as the manner in which they are assembled,
is susceptible to deterioration, which may lead to weakening and therefore to maintenance work. It is important to
understand these potential deficiencies when planning and
performing an inspection. At the 880 ft level, for example,
what are the deficiencies that we might encounter?
Typical visual defects of reinforced concrete include cracking, delamination, and spalling in the concrete, coupled with
potential corrosion of exposed reinforcing. Cracking in concrete can be an indication of shrinkage of the concrete surface during curing, of corroding internal reinforcing that is
expanding, or of overload causing flexural or shear stresses in
the concrete element. These deficiencies can be detrimental
to the structure on which they are observed. Consider that
even a small crack can allow moisture and chlorides to penetrate through the concrete surface and begin to corrode the
underlying reinforcing. Areas of particular concern occur at
portions of the structure at which high shear and moment
loads or zones of high compressive stresses exist.
Steel elements provide their own set of typical visual
defects, for example, paint loss, corrosion, distortion, and
cracking. The loss of paint and corrosion typically correlate.
Even minor defects in the paint system may allow corrosion of the underlying steel, undermining the paint system
around it and exacerbating failure. Corrosion is a concern as
it leads to section loss of the affected steel, resulting in loss
of load capacity.
Distortion can be indicative of stresses beyond the elastic limit state, resulting in permanent out-of-plane bending,
twisting, or elongation of an element. These conditions must
be evaluated carefully to interpret indications of stress reversal possibly caused by the likes of high transverse wind loading, seismic events, or immobility of the structure.
Fatigue cracking is a science unto itself and in general
terms results from repeated loading over a high number of
cycles. Certain design and construction details can increase
the fatigue susceptibility or intensify the loading cycles accelerating localized fatigue. These details are classified as fatigue-prone details and are typically associated with welded
connections in tensile regions of an element. Welds add a
significant level of additional constraint or localized tension
to the steel, reducing available yielding capacity. Category
We like the long, hard days on
rope when on the job. Not all
members of our rope access team
were initially climbers, but all
have a love of adventure, the
outdoors, and bridge engineering.
[ 5 6 ] C i v i l E n g i n e e r i n g o ct o b e r 2 0 1 3 D and higher details are of specific concern, as are design
and construction decisions that place two or more welds in
close proximity.
Cuts in steel members also can be problematic, especially when encompassing abrupt changes in cut or direction
through the material—for example, 90-degree cut copes.
These details are often performed in the field and are well understood by modern designers and builders alike. Smooth,
rounded details transfer stress uniformly, allowing for less
concentration of stress.
Discovering potential material defects of a structure and
determining the locations at which they are most likely to
occur are essential when planning access for a “hands-on”
inspection.
Access to these areas on the Mike O’Callaghan–Pat Tillman Memorial Bridge, given its size and location between
the steep walls of the Black Canyon, is more difficult than on
other structures. An underbridge inspection vehicle (UBIV)
typically can be used to access the undersides of the deck,
girders, abutments, and top portions of the piers but is not
able to reach much beyond 40 ft vertically from the bridge
deck. This limitation leaves a large portion of the structure
inaccessible through traditional inspection access methods.
This is where we apply the ascending, descending, and traversing mobility of rope access. Rope access is one of the only
suitable methods for inspecting the substructure of the Mike
O’Callaghan–Pat Tillman Memorial Bridge.
Stantec’s extensive rope access inspection experience with and arch rib sections called for more careful calculation. The
various bridge types and access difficulties guided our study ropes would have to reach diagonally between spandrel colof the bridge plans. In combination with insight provided umns across the bay, as well as below the arch rib and evby the NDOT staff, this experience revealed the most viable erywhere between. Needless to say, these inspection routes
rope anchor locations, which in this case were primarily at the called for some very long lengths of rope. We deployed up
connections between the steel tub girders and the pier caps. to 1,500 ft of rope for a single rebelay on the outer spandrel
At these locations, ropes could be anchored at the corners of bays. Considering that we routinely had three climbers on
each pier such that an inspector would have a line of sight rope at once, we needed more than 5,500 ft of rope on-site,
across two faces of the pier column from one rope setup. This not including rescue rigs.
plan would allow inspectors to observe 100 percent of the
Now that a detailed plan was in place to access and incolumn surface from just two
spect the structure, rigging
rope setups at opposing corthe ropes and anchors was all
ners. The plan would also prothat remained. In order to obvide access to the foundations
tain the necessary access to
and portions of the arch ribs at
the superstructure and the top
the base of the columns.
of our rope systems, mechaniIn order for an inspector
cal equipment would have to
to safely move longitudinalbe used.
UBIV equipment can be
ly across each spandrel bay via
very efficient when accessrope, the system must utilize
ing the superstructure of such
dual sets of two ropes and anmultispan structures as the
chors located at opposite ends
Mike O’Callaghan–Pat Tillapproximately 110 ft apart. In
man Memorial Bridge, ofthis configuration, the inspecten requiring just a single
tors can ascend and descend
deployment of the UBIV platboth sets of ropes congruently
form. Utilizing the UBIV cain order to position themselves
pabilities, inspectors can acat any point between. This
cess the superstructure to set
method is referred to as rebelay
up the rope system and anif it involves one looped system
chors as planned while evaluof two ropes and as rope-toating the interior and exterior
rope transfer if it relies on two
of each girder. Once the rope
separate dual-rope systems.
systems are in place, inspecThe arch ribs of the bridge
tors can then deploy from the
are hollow and had to be inUBIV platforms. Imagine, at
spected from the interior for
one moment you are in a seindications of internal defects.
cure bucket only to have it
Once inside, inspectors redrop out from beneath you,
quired a set of 700 ft long ropes
to descend and ascend the steep interiors of the Frank Block, P.E., A.M.ASCE, leaving you dangling free almost 1,000 ft off
arches. Confined-space rope access requires an- left, and Tom A. Ritz, P.E., the ground—and with no parachute!
The inspection went as planned, aside from a
other level of safety and training. The stagnant rappel down to an arch of
the Hoover Dam Bypass. single high-wind day that led to downtime for
air inside the arch ribs requires continuous monthe required mechanical equipment. The initoring via four-gas air monitors. Each inspector
is equipped with a monitor, and the readings are radioed to the spection was completed ahead of schedule halfway through
the seventh day. The structure’s impeccable condition was
access supervisor at prescribed intervals.
When using rope access, one of the most important as- indicative of the care taken during design and construction
pects of the plan is to know how much rope will be needed. and made for a relatively effortless inspection, especially in
You need the requisite length of rope below you as you de- view of the bridge’s size and complexity. At the time of the
scend through the inspection; otherwise, it would be like inspection the bridge had been open to traffic for less than 27
driving across Death Valley on a quarter of a tank of fuel. months. As for the crossing’s future, it seems certain it will
You simply won’t make the full journey. There aren’t going stand proudly in the Black Canyon for decades, if not centuto be any rope stations along the way. Again, careful study ries, to come—an infinity compared with the brief time that
of the bridge plans was necessary to complete the detailed will elapse before its concrete facades are graced by the ropes
ce
approach. The rope length necessary to descend the spandrel and prying eyes of the next inspection, in 2015.
and pier columns is equal to the vertical height of the pier
and foundation plus an additional 10 to 15 ft for anchors Ryan Nataluk, P.E., is a senior structural engineer and the bridge
and maneuverability. Inspection of the spandrel columns inspection program manager for Stantec Consulting in Denver.
o ct o b e r 2 0 1 3
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