Remarkable ancient timber bridges up to the 1850´s. Part I: general review

Abstract

In 1850, the Bessemer converters were able to produce mass-production inexpensive steel. This technical advance was the key point that leaded to a suddenly extended use of steel in the bridge engineering field. Consequently, timber was pushed into the backstage as a structural material during many decades. In the other hand, timber has been fortunately recovered, especially from 1970´s, as engineering material.
This paper presents the part I of a first stage work concerning to the study of remarkable ancient timber bridges from 1650 to 1850. Part I consists of a general review. The comparison with the current state of art proves that the technical heritage is worth analyzing as a lesson for the present. Selected case studies would be used to explain the historical timber bridge breakthroughs in part II [1].
The geographical areas analysed were restrained to Europe and USA due to the limitations to the access to first-hand sources. Nowadays works following these principles are many (see e.g. [2]), but James’s work [3] still continues being a basic guide for authors.

Full text

Remarkable ancient timber bridges up to the 1850´s. Part I: general
review
Guillermo ÍÑIGUEZ-GONZÁLEZ(1)
Assistant Professor
Technical University of Madrid (UPM)
Madrid, Spain
guillermo.iniguez@upm.es
José L. FERNÁNDEZ-CABO
Associate Professor
Technical University of Madrid (UPM)
Madrid, Spain
Miguel C. FERNÁNDEZ-CABO
Associate Professor
Technical University of Madrid (UPM)
Madrid, Spain
Francisco ARRIAGA-MARTITEGUI
Professor
Technical University of Madrid (UPM)
Madrid, Spain
M. Almudena MAJANO-MAJANO
Ph.D. Student
Technical University of Madrid (UPM)
Madrid, Spain
(1) 2007. Ph D. in Forestry Engineer.
Technical University of Madrid (UPM)
2002. M. Sc. in Forestry Engineer.
Technical University of Madrid (UPM)
Research and Work lines:
Non-destructive evaluation of timber.
Design, calculation, pathology and
rehabilitation of timber structures.
Summary
In 1850, the Bessemer converters were able to produce mass-production inexpensive steel. This
technical advance was the key point that leaded to a suddenly extended use of steel in the bridge
engineering field. Consequently, timber was pushed into the backstage as a structural material
during many decades. In the other hand, timber has been fortunately recovered, especially from
1970´s, as engineering material.
This paper presents the part I of a first stage work concerning to the study of remarkable ancient
timber bridges from 1650 to 1850. Part I consists of a general review. The comparison with the
current state of art proves that the technical heritage is worth analyzing as a lesson for the present.
Selected case studies would be used to explain the historical timber bridge breakthroughs in part II
[1].
The geographical areas analysed were restrained to Europe and USA due to the limitations to the
access to first-hand sources. Nowadays works following these principles are many (see e.g. [2]), but
James’s work [3] still continues being a basic guide for authors.
Keywords: ancient timber bridges, history, design.
1. Introduction
Timber and stone were the two main construction materials used until the beginning of the 19th
century, when the use of iron began to take the leadership for medium and, especially, for long span
structures.
Scientific Revolution produced the figure of the -engineer-, firstly in France, in the 18th century;

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
country who leaded the engineering until the second half of the 19th century. The engineering
education in France did not consider timber as a -first category- bridge material; mainly masonry,
and afterwards, iron and steel were considered as really proper materials for bridges during 18th and
19th centuries. The possibility of decay and the vulnerability to fire were clear drawbacks that were
not presented in the more expensive masonry bridges.
Even though, French manuals around 1850´s already collected the major master pieces of the
Grubenman´s (Wettingen and Schafhausen) [4], [5] and [6]; these works did not influence its
practical engineering [7]. French timber bridges were made just as a second choice, after the
masonry bridges, and with a clear parallel to them, i.e. without cover and placing the arch
underneath the floor. As protection technology was very poor, decay came quite soon; which meant
therefore a continuous precaution or even rejection of the timber as material.
The situation in UK was not so critical for timber at the beginning, even though, its evolution ran
quite parallel to France in relation with the layouts of the bridges. Thomas Telford (1757-1834),
firstly, stonemason and architect, was the first great UK engineer (and the first president of the
Institution of Civil Engineers). He dominated the masonry and used the timber in small bridges
(with a good anti-funicular design), but his preference was on iron, with superlative words. The
next British generation of engineers, leaded by Isambard Kingdom Brunel (1806-1859), kept,
fortunately, a more comfortable relation with timber. Even the preferences were for the iron, timber
was employed in important works, as it happened with the railroads viaducts made by the Green´s
[8] and Brunel [9]. An explanation can be found in the protection technology advances quickly
explored and used in UK [10].
In Europe, timber bridge engineering excels in Switzerland, Germany and Austrian Tyrol. Roman
tradition was expanded and improved. The use of covered bridges meant a huge increase in the
durability of these works, and this at sure made easier its use. The privileged situation of timber is
reflected in the number and quality of the printed manuals (see [1]).
Nevertheless, USA contains, without doubt, the most remarkable case studies. European emigrants
introduced its tradition there, especially from UK and central Europe. Breakthroughs were almost
immediately also known in this country (Pope’s manual already collects the Grubenmann´s master
pieces [11]). But they had an additional advantage: timber was cheap and abundant, and the country
was needed of a huge number of bridges. Moreover, during the colonization of the far west, builders
had a special freedom.
This article presents a general overview and analysis about timber bridge heritage and the current
state of art. Section 3 analyzes the database from 1650`s up to 1850`s, and section 4 does it from
1980`s to our days. A comparison between these two periods makes possible to understand why past
is worth of studding as a lesson for the present.
2. Methodology
Once the bibliographical sources were collected, a database, using EXCEL®, was implemented to
be able to sort and filter all the available data. The main and initial source was the work of James
[3], but finally some other works were added as the reference section reflects; especially for the
bridges from 1980´s.
It has been recorded a total of 162 bridges (86 bridges from Europe and 76 from North America;
and including several patents) up to the 1850´s (in reality, 1862), and 42 bridges from 1980´s to our
days. Remarkable, in this context, means a bridge with a span bigger than 30 m (100 ft), even
though this value was reduced for the older examples.
For each entry, the following topics were registered: ID (number that identifies the bridge) Name,
River, Site and Country, Date (of construction), Author/s, Structural Type, Function (pedestrian,
vehicles, railroad), Status (in use, reinforced, disappeared), Spans, and Additional Comments.
The authors support the idea of creating a collective and public database, where any researcher
would collaborate and use the information.

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
3. Analysis of the timber bridge database up to 1850´s
Distribution of built bridges by countries included in database is shown in Fig. 1.
Bridges / Country
110
12
15343
18 14
47
0
10
20
30
40
50
60
70
80
90
Austria
Czech Republic
France
German
y
Ireland
Poland
Romania
Russia
Slovakia
Switzerland
United Kingdo
m
USA
Number of bridges
Fig. 1 Built bridges by country included in data base
Countries in Europe as Switzerland, Germany and United Kingdom excel in places with remarkable
timber bridges built up to 1862.
Those three countries together represent more than the 70 % of the bridges built.
Fig. 2 summarizes the analysis about the traffic carried by each bridge and the date when they were
built.
Bridges (road and railway) / Date
4
10 9
26
50
9
4
10 9
26
16
4
0000
31
0
0
10
20
30
40
50
60
1650-1750 1751-1775 1776-1800 1801-1825 1826-1850 1851-1862
TOTAL b ridges
Road bridges
Railwa y bridges
Fig. 2 Number of built bridges by type of traffic and date
A continuous growth of the number of bridges built can be observed and until the second quarter of
the 19th century, railway timber bridges do not come out. It is evident as well, the fall in the number
of timber bridges after 1850´s.
First full scale working railway steam locomotives appear in the United Kingdom around 1800, but
are extended in the 1830´s, and in the 1840´s at USA. The first transcontinental railroad in the
United States, the "Pacific Railroad", was built between 1863 and 1869. The existing railway

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
network of the Eastern United States, and the road that connected the Atlantic and Pacific coasts of
the United States by rail, for the first time were linked.
It is important to note that at first, the Union Pacific was not directly connected to the Eastern U.S.
rail network. Instead, trains had to be ferried across the Missouri River. In 1872, the Union Pacific
Missouri River Bridge was opened and directly connected the East and West. This bridge was an
iron bridge, timber bridges were an old fashion at that time.
This event represents perfectly the history of railway bridges in USA. First steps of the railway
were taken over timber bridges but heavier locomotives and “new” materials as iron; rapidly took
out timber from bridge construction.
Total span of the bridges grew in parallel with the number of them, as it is shown in Fig. 3.
Date / Max and average Span (road and railway)
50,3
73,2
85,4
111,9
77,7
61,0
42,7 45,5
59,3 57,4 50,0 58,2
83,8
50,3
0,0
20,0
40,0
60,0
80,0
100,0
120,0
1650-1750 1751-1775 1776-1800 1801-1825 1826-1850 1851-1862
Roa d bridges Max S pan m
Road bridges Average Max Span m
Railway brid ges Max Span m
Railway bridges Average Max Span m
Fig. 3 Max. span and average max. span of built bridges by type of traffic and date, in meters
As time went by, designers felt more confident with timber, and more bridges and longer spans
were crossed.
The maximum span (111.9 m) corresponds to a Theodore Burr’s arch over the Susquehanna river at
McCall's Ferry, Pa, in USA, built in 1814. Arch ribs had two members spaced 2.13 m apart by post,
the panels being braced and counter-braced. It is not clear how the deck was arranged but
presumably it was suspended like that of the Trenton bridge, built in 1804 and 61.89 m of laminated
bowstring, with vertical iron hangers.
Unfortunately, as James quoted [3], the 111.90 m arch seems unpleasantly slender and it collapsed
in 1818, an event followed by the collapse of Burr’s business and early death.
From 1826 to 1850, it is important to note, that road bridges and railway bridges were close in
terms of maximum free and average span crossed. 77.7 m of max span for road bridges and 83.8 m
of max span for railway bridges.
Cascade railway bridge worths a special mention, a triangulated wooden arch of 90 m span erected
by Major Thompson S. Brown and Colonel Julius W. Adams finished in 1848, was in Cullman’s
opinion [12], “the most beautiful piece of carpentry work in America, and possibly unique in the
whole world”.
The Erie Railroad traverses a ravine of over 50 m deep and, on top, more than 90 m wide. Structural
type was an arch with Howe ribs.
Never before, so long free spans were crossed and so many amount of bridges were designed and
built using exclusively sawn timber. Knowledge and practice of timber bridge designers and
builders were in a really high level, never outstripped.

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
In Fig. 4, number of spans by type of traffic and date are analyzed.
Date / Number of spans (road and railway)
2
9
6
19
13
4
1
32
2
7
1
10
5
16
0
5
10
15
20
25
30
1650-1750 1751-1775 1776-1800 1801-1825 1826-1850 1851-1862
Road bridges 1 span
Road bridges 2 spans
Road bridges 3 or more spans
Railway b ridges 1 s pan
Railway b ridges 2 s pans
Railway b ridges 3 o r more sp ans
Fig. 4 Number of spans in built bridges by type of traffic and date
Same conclusions can be drawn as in the previous figure, as time goes by, longer free spans were
crossed and long distances covered.
While road bridges were sort out by one span bridges, railroad bridges had, usually, 3 or more
spans.
4. Analysis of the timber bridge database from 1980´s
From a total of 42 timber bridges, 12 are from Switzerland, 7 from Germany and 21 from the
Nordic Countries: Norway, Sweden and Finland.
The database is far away to be complete, as it is limited to Europe, and even there it is not complete.
But now the main target is just to compare the current situation with the one previous to 1850´s, and
the selected examples reflect the current state of art.
Although some pedestrian timber bridges were constructed in the 70`s, the renaissance of the timber
bridges in Nordic Countries started in the 90`s. As Nordic experts ensure, the significant
contribution to the development of the timber bridge technology was given by the Nordic Timber
Bridge Project [13].
Apart of the number of bridges for country, the big difference founded, is the kind of traffic carried
by the analysed bridges.
Up to 1850, the recorded bridges had more that 30 m of span and were road or railway bridges. For
the bridges built after 1980, minimum of 30 m of span is considered as well, but the kind of bridges
had changed. Nowadays bridges are pedestrian or road, but not railway bridges. Railway lines have
removed timber from their bridges.
In order to mention heavy loads carried by timber bridges, it should be cited the bridge across Rena
river in Norway, named as the “world's strongest timber bridge”.
Built in 2005, it is part of the road network within a Norwegian military training facility. The two
lane timber truss bridge is 158 m long. It was designed for a service life of 100 years and to carry
the load of a heavy military vehicle convoy in one lane (vehicles 30 m long and weighing up to 109
tons each) and full traffic load in the other lane. This gives a design load significantly higher than
for ordinary two lane road bridge.

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
In the other hand, Fig. 5 shows the maximum span and average maximum span of built bridges by
type of traffic.
Date / Max and average Span (foot and road)
80,0
90,0
56,0 50,0
45,0
70,3
34,6 33,6
0,0
20,0
40,0
60,0
80,0
100,0
120,0
1980-1995 1996-2010
Foot bridges Max Span m
Foot bridges Average Max Span m
Road bridges Max Span m
Road bridges Average Max Span m
Fig. 5 Max. span and average max. span of built bridges by type of traffic and date
Vax Holm bridge, built in 1996 in Sweden, is a cable-stayed pedestrian bridge with a span of 90.0 m
and one of the world’s greatest span.
Flisa bridge [14], at Glomma, built in 2003 in Norway, is the world’s longest timber bridge
designed for full traffic loads with respect to clear span (70.34 m), and one of the longest with
respect to total length (196 m). It is also worth of mention the bridge over the Rena river, designed
for heavy tanks [15].
More than 70 m of clear span for a road bridge is an important mark, but it is necessary to
remember that this span was already overcame in 1756 for the Grubenmann´s in Switzerland, and
in 1794 for Timothy Palmer in USA.
5. Conclusions
Until the end of the 18th century, development of the long-span wooden through-truss bridge took
place primarily in Switzerland and Germany, where the knowledge for such structures was deep.
At the beginning of the 18th century, the leadership moved to USA, the facility to get good quality
and abundant raw material, and the necessity of quick conquest of virgin land, along with the
knowledge imported from Europe and domestic patents developed, led to new building typologies
and a large number of buildings.
At 1850´s, the number of remarkable timber bridges is Europe and USA was similar, but the USA
dominance in the construction of railway bridges was evident.
A continuous growth of the number of bridges built and the length of the span crossed from 1750´s
to 1850´s is confirmed.
The appearance and rapid development of railway, creates a new challenge that leads to hone the
talent of the designers and make the most of it to the builders. This period in terms of knowledge
and good work, is not repeated in the following years.
The quick development of steel and other materials meant the decline and abandonment of timber
as construction material for bridges. The resurgence of the use of wood in construction of bridges is
evident from the 80`s until today, but despite the new products developed and improved techniques,
the maximum spans and the structural typologies of those years, have not been overcame.
As novelty, it is the fact that Nordic Countries have entered in the statistics and constitute the
reference present and promising future of this discipline.

ÍÑIGUEZ-GONZÁLEZ, FERNÁNDEZ-CABO, FERNÁNDEZ CABO, ARRIAGA-MARTITEGUI, MAJANO-
MAJANO: Remarkable ancient timber bridges up to the 1850´s. Part I: general review
International Conference on Timber Bridges 2010, Lillehammer, Norway
The comparison between the past and present designs is obviously not fair, as new scientific tools,
technologies and material means an important improvement in relation to the past. The advances are
especially remarkable in relation with the connection systems, now stiffer. This includes -glues-,
key for most of the new timber engineering materials. It exists also a huge advance in wood
protection technologies. But, when maximum spans are compared, this only highlights the
importance of the timber bridge heritage.
6. Acknowledgements
This paper is mainly based on J. G. James’s work, which has guided authors all the time. The data
base recorded has been especially created with the help of the following sources: Institution of Civil
Engineers (UK), Berkeley University (USA), Google on-line open library, digital historical archive
of the ETS de Aquitectura:
http://www.aq.upm.es/biblioteca/fondoantiguo/historiaconstruccion.html and the ETS de Ingenieros
de Caminos, Canales y Puertos of the UPM (Spain); On-line records of Historic Bridges of the USA
and Switzerland: http://bridgehunter.com/ and http://www.swiss-timber-bridges.ch/
Thanks to Nagore Etxeberria, for her technical comments and final review of the text.
7. References
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International Conference on Timber Bridges 2010, Lillehammer, Norway
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