Articles > Cement Shoes 2
Cement Shoes
Part Two - Niagara Follies
There were already dozens of wire suspension bridges in France at the time of the
1850 disaster at Angers. Many wide, deep rivers of North America presented a
greater challenge for bridge builders than those previously encountered in Western
Europe. In 1843, Charles Ellet Jr. had suggested studying “…the Niagara River,
below the Falls, where the gorge could be readily spanned by a beautiful edifice…”
By Don Sayenga
Published in Rope News & Sling Technology August 2015
It is fascinating to review the many similarities between the situation at Niagara Gorge in the 1840s and the completion of a bridge at the Si Du Gorge in China within the last five years. Both projects were classed in the world’s record category. Both projects required some sophisticated engineering to get the wire suspension cables anchored. Both projects began in a similar way: to get the first line across at Niagara Gorge they used a kite; at Si Du Gorge they used a rocket.
In 1997, Harvard Business School professor Clayton Christensen coined the term “disruptive technology”. In his explanation of what he meant by the term, he offered two depictions of
how continual innovations affect our daily lives. He named them either “sustaining” or “disruptive”. The advent of iron wire rope in the 1830s exemplified both kinds of innovation. In the case of mining technology, the substitution of metal wire ropes for cordage and chains sustained and enlarged the use of ropes for excavation. In the case of suspension bridges, the same innovation
was disruptive.
Bridge engineers in the 1800s were faced with making a decision about the disruptive technology of wire cables for several reasons. The application of wire cables in structures progressively reduced the use of the metal chains previously used for exactly the same purpose. Drawn wire was stronger than forged chain due to cold mechanical deformation. The greater strength of iron wire allowed the total weight of the structure to be lighter. Wire cables supporting the structure needed less weight to serve as an anchor which, in turn, reduced the size of the anchorages.
In the 1840s, the primary disadvantage of wire cables was the greatly increased total surface area exposed to atmospheric corrosion. Protecting wire cables against corrosion was mainly done by painting. Chinese engineers working at Si Du Gorge in the 21st Century had the benefit of using cables made from drawn steel wire which is even stronger than iron wire. They also profited from many advances in metallurgical corrosion prevention techniques.
FALLING THROUGH THE CRACK
In France, the commission of inquiry investigating the 1850 Angers tragedy issued their report (known as the Dupuit Report) without suggesting any good remedy. The French government declared a halt to the construction of wire bridges, pending an assessment of the other wire bridges scattered all over their nation. At first, the French moratorium was more or less ignored elsewhere. One of the three causes of the failure (troops marching in step) was already recognized as a no-no in the UK. As for the deck being flexible enough to be twisty in a windstorm, engineers were already contriving various styles of trusswork to make bridge decks stiffer. In the USA three of the
most popular trusswork designs were known as Howe, Pratt, and Warren.

The cement shoes defect doesn’t seem to have attracted much scientific attention.
Maybe because it was easy to reason
the troops marching, and the deck
twisting, were the main problem. After
a decade of use, those cement seals of
the anchorages had broken free of the
wires, forming a rigid envelope. Tiny
cracks extended to the exterior. If they
were spotted they could be resealed,
but there was no way to look down into
the anchorage where gravity was causing
moisture to collect at the ends of
the cables – the worst possible place.
Following the great success of the
1842 Schuylkill wire suspension
bridge, Americans were scoping out
other previously uncrossable locations
for wire bridges. The Ohio River drainage
system was being converted into a
transportation corridor where the concept
of a pier-free bridge offered many
opportunities. The Saint Lawrence
River and the Niagara River forming a
boundary with Canada were two other
prime sites under discussion by transportation
experts.
LIKE A CHICKEN CROSSING TO THE
OTHER SIDE
The idea of getting a bridge over the
Niagara River was two-fold: [1] mainly
to facilitate travel into Canada more or
less in the direction of Toronto, and [2]
facilitate tourists who wanted to see
the Canadian side (the most impressive
side) of Niagara Falls, the site of
which was out in the wilderness near
Fort Niagara, a defensive military
base. For purpose #1 the best location
was between the villages of Queenston
ON and Lewiston NY. For purpose #2
the best location was at the gorge just
upstream from The Whirlpool. This
was also the narrowest point. The debate
between the two sites was never adequately settled – therefore as a result
of the debate, suspension bridges
were built at both locations.
To create bridges over a boundary
line two companies were needed; one
in each country, functioning jointly. It
wasn’t a comfy arrangement. The first
bridge across was at the gorge site, built
in 1848 by US engineer Charles Ellet,
Jr., and the second was at Queenston /
Lewiston built in 1851 by US engineer
Edward Serrell. Both bridges used
French-style multiple parallel-wire
cables fabricated at the site. Neither
bridge was strong enough to be used by
a railroad train, but we should not forget
at the time there were no railroads
anywhere near either site.

Both bridges used underfloor wire stays to hold the bridge deck steady in
a windstorm. One of the problems faced by bridge-builders at Niagara occurs in
a severe winter when Lake Erie freezes over. After a thaw, enormous masses of
ice propelled by gravity churn through the gorge. In the winter of 1853-54, ice in
the gorge threatened the underfloor stays of Serrell’s bridge at Queenston / Lewiston.
To preserve them, they were disconnected, allowing the ice to pass, but before
they could be reconnected a windstorm wrecked the bridge floor. Ellet’s bridge
was at a higher location. Its underfloor
stays were safe. Meanwhile, both bridges
had demonstrated success crossing the
river, causing many developers to contemplate
putting a railroad across.
In 1852 John Roebling got involved.
He proposed to use Ellet’s bridge as a
work platform to build a double-deck
bridge with a railroad on the top deck.
He had received a patent in 1847 for
a method to stretch a doubled length
of wire across an open space allowing
him to build up a cable approximately
in place. The cable was one long piece
of wire doubled again and again by the
process. In 1855, he built his bridge at
Niagara in this manner, removing Ellet’s
bridge in the process, but re-using
the wire from Ellet’s cables. The rest of
the wire was purchased in the UK.
John A Roebling’s final report to the
owners of the bridge is dated May 1, 1855. On Page 19 he gave the following summary of how he constructed his anchorages:
“The chains end at the level of the coping, where they connect with
the cables, which are also enclosed in
grout and masonry for a length of 12
feet, the latter terminating in ornamental
blocks above the coping. The
strength of the wire is not affected by
sudden changes of temperature; no further
protection of the cables therefore
is required.”
AN ACCIDENT WAITING TO HAPPEN?
Because no one had any experience
with repairing cement shoes such as
those installed at Angers and Niagara,
the 1850 conclusions the Dupuit
Report caused very little excitement
in the USA. Few technical journals
were being published in the States,
the Americans had just concluded our
war with Mexico, and everyone was
distracted by the California gold rush.
British engineers, however, were more
alert. Canada partly belonged to both
England and France. The Canadian
railroad using Roebling’s unique double-
deck structure studied the subject.
For a variety of reasons, questions began
to be raised about Roebling’s wire
cables at Niagara Gorge almost immediately
after the bridge went into service
in 1855.
According to Washington Roebling,
who was attending college at Rensselaer
Polytechnic Institute in Troy, NY
during the time of the Niagara Gorge
project, his father realized it was extremely
important to dispel any doubts
about his bridge.
“Mr. Roebling felt it his duty to go there in the summer of 1860
and make an inspection. This
resulted in the writing of a
pamphlet entitled the “Condition
of the Niagara Bridge”
published Aug. 1, 1860 …In
this paper he … lays great
stress on the preservative effect
of cement on iron bars
when imbedded therein.”
The Suspension Bridge used different combinations of three rails to serve three different railroads.
Photo shows the crossing of a locomotive over the Niagara Suspension Bridge, along with the
triple gauge railway on the bridge. The sealed anchorages can be seen in the foreground.
Photo courtesy Niagara Falls Public Library
John A. Roebling wasn’t
wrong very often, but when he
was wrong he seems to have
believed he could be wrong at
the top of his voice to shout
down any opposition. His 1860
report concludes with these
words:
“The cables of the Niagara
Bridge… will last as long as
the nature of good wrought iron
will permit, when subjected
to a moderate tension,
not exceeding one-fifth of its
ultimate strength. This durability
I am unwilling to estimate
at less than several
hundred years… I will close this report
by repeating once more… that they are
free from vibration; that they are well
preserved and taken care of; and consequently
that they may be safely trusted
for a long series of years.”
In retrospect, there are very few ways
to explain why a brilliant engineer like
John A. Roebling would deliberately
build a spectacular bridge containing a
design flaw condemned by the Dupuit
Report. Roebling’s designs differed
from the French practice in several
ways. His wooden decks were deliberately
built more stiff. His
multiple main wire cables
were compressed into circular
cross-section and
wrapped end-to-end with a
wire serving, everywhere
except at the saddles and
inside the anchorages.
He connected the ends of
his cables to iron eyebar
chains which descended
into the anchorages on a
curving slant instead of
plunging vertically.
If we seek an explanation,
we might guess he
was unaware of the Dupuit
report but that is almost
unthinkable. He was
constantly reading technical
literature and was
publishing his own theories
where everyone could read them. It becomes more obvious if we see this as a territorial stake-out. Roebling was
financially successful as a wire rope manufacturer. He didn’t need the money,
but he was desperate to gain prestige as a bridge-builder. One element
of his turf-protection strategy was to obtain U.S. Patent protection on what
he thought were the best of his ideas.
There it is: he was granted Patent
4710 on August 26, 1846 for “Improvements
in the Wire Cable or Chain Suspension
Bridge”. The text of Patent
4710 begins “My plan of anchorage
differs very materially from the mode
hitherto pursued.” After describing
how and why he had devised a superior
anchorage, he summarized like this:
“It is also my practice to surround all
the iron below ground by hydraulic cement
and wall it in with solid masonry,
in place of leaving an open channel as
is the case in most suspension bridges.
The cement with which I surround
the chains or cables preserves them
against rusting effectually.”
PASSING THE BUCK
Despite the strident assertions of
Roebling’s 1860 report, uncertainties
about the cement shoes of Roebling’s
Niagara main cables continued to
be bothersome to the railroads. The
owners of the international bridge were watching it carefully. They were
mainly concerned about the steady deterioration
of the wooden structural elements
but the unknown status of the
main cable anchorages added to their
anxiety. Unlike other wire bridges, it
wasn’t a major transportation artery.
The owners were faced with losing
oodles of tourist revenue if any repair
work interrupted use of the bridge.

Eight years after Roebling’s unexpected
death in 1869, the Canadian
railroad that was using the bridge demanded
a study of its condition. The
bridge company called in a group of
brilliant American engineers including
T.C. Clark, W .H. Paine, L.L. Buck,
T.E. Sickles, and Milnor Roberts to
assess the cement shoes. They got to
the bottom of the matter very quickly.
Although they made their studies quietly,
without interrupting traffic which
would have alarmed tourists and honeymooners
using the bridge, they had to
report some extremely bad news about
cable corrosion inside the anchorages.
The discovery of cable corrosion caused
a commission to be formed to make a
decision about what to do next. Everyone
realized a quick fix was impossible,
and mum’s the word.
According to L. L. Buck,
who summarized the findings
with a complete historical
wrap-up in 1881,
the situation at Niagara
was identical to what the
French panel found at Angers
two dozen years earlier:
“…the whole pit being
solidly filled with cement
masonry…the strands were
also covered with masonry
and the whole grouted, the
intent being to preserve
them from oxidation… The
evident cause of this corrosion
was the elongation and
contraction of the strands
under passing loads which
had loosened the cement
from the outside strands,
allowing moisture to work
in and finally reach the lowest
point”.
THE RIGHT MAN FOR THE JOB
L.L. Buck (1837 - 1909) served as an
enlisted man in the Union Army during
the Civil War. Although he was
already in his late 20s when the fighting
ended, he enrolled at Rensselaer to
get his CE degree in 1868. None of the
older, better established civil engineers
was eager to risk his reputation on a
scary fix like Niagara. Buck, however,
had gone to Peru after college, where
his innovative work on the Verrugas
Viaduct attracted lots of attention
among his peers. He was eager to tackle
the challenge. The bridge company
gave him a contract in September 1877 to correct the anchorage. They
also had him consider removing
the wooden deck truss to be replaced
with ironwork.

The task was complicated because
the double-deck bridge
had four main cables, not just
two. According to bridge historian
Frank Griggs, writing in
Structure Magazine (2010) Buck
“…arrived at the site September
13, 1877. He finished the anchorage
rehabilitation and later
replaced the wooden deck structure
with iron, in less than eight
months.” As an extra burden, after
beginning the job Buck discovered
“the old walls extended
back further than was shown in
the plates of Mr. Roebling’s report
… which would necessitate
very expensive trenches...”. He
figured out a way to get around
the problem, allowing him to cut
out corroded wires, one by one,
and splice in new ones.
While the anchorages were being
fixed, he examined the deck which was
in worse condition than he expected:
“In short, there were very few tight
joints in the structure. It had, consequently,
become extremely flexible …
it was evident that any attempt to repair
the structure would only result in
the rapid destruction of the new work.”
Buck got the go-ahead to create a new
iron truss and deck. He made a
careful evaluation of possibly
using steel instead of wrought
iron. For his own reassurance,
he submitted his ideas to Washington
Roebling who approved
his plans.
Buck was ahead of his time.
He reported: “the use of steel for
structural purposes had not yet
reached a stage at which all of the
required shapes could be promptly
and economically obtained – at
least in this country. Consequently
my specifications were …for
the use of either iron or steel or a
combination…” The substitution
of a metal deck aroused another
specter. Examination revealed
the limestone blocks at the tops
of the towers had begun to spall.
In Washington Roebling’s words:
“Mr. Buck then addressed himself
to the remarkable engineering
feat of replacing the stone towers…and yet keeping the traffic uninterrupted.”
Frank Griggs explains: “Buck decided to build new wrought-iron towers around the existing stone towers…Engineering News called it ‘the most delicate and daring piece of bridge-work ever undertaken’. The Engineering Record wrote ‘his reconstruction of the towers of the bridge in 1886 is probably one of the most remarkable engineering achievements of our age…
performed so modestly … few people knew that such an enterprise was even contemplated”. Because of the publicity black-out, Buck never has received the praise he deserves, which is truly unfortunate.
THERE’S MORE TO THIS STORY, FOLKS
After 1825, the Erie Canal launched faster transportation between population centers on the Hudson River and the Great Lakes, but it was Cornelius Vanderbilt’s New York Central Railroad which greatly eased the journey. In the years following the Civil War, a trip to Niagara Falls became the trope linked to thousands of honeymooning couples from the USA. Tourist traffic
mandated faster and more frequent train service. The population of Erie County was multiplied by four in the years 1850-1900.
The two cities known as Niagara Falls, one in each nation, grew rapidly at both ends of the bridge. As the weight of railroad locomotives steadily increased it became clear there would soon be an expiration date for Roebling’s bridge. One of the band-aids applied toward the end was the substitution of streetcars. Ultimately, about twenty years after Buck was called in to get rid of Roebling’s cement shoes, he replaced the entire thing with a completely new bridge. The story of how he achieved this, again without interrupting
traffic, is among the greatest stories of civil engineering.
Buck’s saga is a tale told rarely because he worked without publicity. Anchorages
for the Brooklyn Bridge had just been completed when Buck started the job. Washington Roebling later commented
on the irony that his father wasn’t around to read Buck’s report:
“Dying when he did he was spared the mortification of finding that the cable wires were very badly rusted where
they connect with the anchorages - large numbers had to be replaced - and if the mischief had gone on much longer, the cables might have fallen long before the predicted two hundred years”.
The anchorages of the Brooklyn Bridge were designed by Washington
Roebling to omit cement shoes, because,
as he put it: “The best plan is
to leave everything open free of access,
only covered against the weather so
that it can be inspected and painted
from time to time.” Prior to designing
and building the Brooklyn Bridge,
Washington Roebling had observed his
father in action at two other bridges.
One over the Allegheny River and one
over the Ohio River. Both were built
with cement shoes.
Further Reading
- Cement Shoes Part 1 Angers 1850
- The story of the Si Du Bridge was presented in 2008 by
Chongxu Wang, Dr. Yuancheng Peng, and Dr. Yinbo Liu
at the International Bridge Conference in Pittsburgh PA.
It was reprinted in the form “Crossing The Limits” by Civil
Engineering magazine (Reston VA January 2009 Vol 79 No
1 pp. 64-80)
- L. L. Buck’s Report on the Renewal of the Niagara Suspension
Bridge (1881) is now downloadable from the internet
at: https://archive.org/details/cihm_26454
Frank Griggs’ 2010 bio of L.L. Buck can been seen at
www.structuremag.org
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