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Analysis of suspended bridges for isolated communities

Hermansson, Viktor LU and Holma, Jonas LU (2015) VBK920 20151
Division of Structural Engingeering
Abstract
Light suspended bridges are often used to connect villages or trail systems in geographical areas
with lacking infrastructure and demanding topology. Different international non-profit
organizations in collaboration with local promoters are building these bridges with the purpose
of connecting isolated communities with health care and education.
The design and construction of these bridges has by and large relied on engineering judgment
and design conservatism coupled with past experiences of similar construction projects. An
interest to engage in the designing of similar bridges has been shown from staff at the Division
of Structural Engineering at the Faculty of Engineering of Lund University. This master thesis
aims... (More)
Light suspended bridges are often used to connect villages or trail systems in geographical areas
with lacking infrastructure and demanding topology. Different international non-profit
organizations in collaboration with local promoters are building these bridges with the purpose
of connecting isolated communities with health care and education.
The design and construction of these bridges has by and large relied on engineering judgment
and design conservatism coupled with past experiences of similar construction projects. An
interest to engage in the designing of similar bridges has been shown from staff at the Division
of Structural Engineering at the Faculty of Engineering of Lund University. This master thesis
aims therefore to provide more sophisticated models of suspended bridges as material for future
work.
Suspended bridges are suitable to use for long spans, both due to low construction cost and to
efficient material usage. They can also most often be built without advanced tools or machinery.
The bridges studied in this thesis are intended for pedestrians and animals which result in a very
slim design.
Recommendations mainly from the development organization Helvetas will be compared to the
Eurocode to investigate if these creates overly conservative designs. These comparisons will be
made with both hand calculations, the finite element software Brigade/Plus and data from
existing bridges.
Vibrations and sways due to wind can be a major problem for light suspended bridges. Due to
their small dead load in combination with a low lateral stiffness, the sways and vibrations can
be very large in comparison with more common pedestrian bridges. This could lead to
temporary inoperability or in worst case structural failure. With the models made in
Brigade/Plus, wind effects can be analyzed and suitable measures or restrictions can be
proposed. (Less)
Popular Abstract
Light suspended pedestrian bridges are often
built in rural areas to connect isolated
communities. With steel cables as main load
bearing elements, the structure becomes very
load efficient. Due to easy construction methods
and few parts, these bridges also becomes cost
effective. Because of the lightness of these
bridges, they become sensitive to wind effects.
These effects are investigated in this thesis.

Light suspended bridges are often used to connect
villages or trail systems in geographical areas with
lacking infrastructure and demanding topology.
Different international non-profit organizations in
collaboration with local promoters are building
these bridges with the purpose of connecting
isolated... (More)
Light suspended pedestrian bridges are often
built in rural areas to connect isolated
communities. With steel cables as main load
bearing elements, the structure becomes very
load efficient. Due to easy construction methods
and few parts, these bridges also becomes cost
effective. Because of the lightness of these
bridges, they become sensitive to wind effects.
These effects are investigated in this thesis.

Light suspended bridges are often used to connect
villages or trail systems in geographical areas with
lacking infrastructure and demanding topology.
Different international non-profit organizations in
collaboration with local promoters are building
these bridges with the purpose of connecting
isolated communities with health care and
education.

The design and construction of these bridges has by
and large relied on engineering judgement and
design conservatism coupled with past experiences
of similar construction projects. This master thesis
aims to provide more sophisticated models of
suspended bridges as material for future work.

Vibrations and sways due to wind can be a major
problem for light suspended bridges. Due to their
small dead load and low lateral stiffness, the sways
and vibrations can be very large in comparison with
more common pedestrian bridges. This could lead
to temporary inoperability or in worst case
structural failure. An existing bridge with a span of
100 meter has been analyzed to be able to calibrate
reliable FE-models. With these models wind
effects can be analyzed and suitable measures or
restrictions can be proposed.


The contributions of the thesis are a general insight
in the construction of these type of bridges, a
working FE-model of suspended bridges and how
the behavior changes with different setups such as
span or sag. Some specific conclusions made in the
thesis are:
Modifying the sag is the best way to affect
the natural frequencies.
The criteria for using wind stabilization
should rather be based on displacement
than accelerations.
Bridges designed with design guides
provided by aid organizations requires
larger cable dimensions than bridges
designed according to Eurocode.
Due to the nonlinearity of sagging cables a
full implicit dynamic analysis is preferred
when determining the dynamic response of
a suspended bridge. (Less)
Please use this url to cite or link to this publication:
author
Hermansson, Viktor LU and Holma, Jonas LU
supervisor
organization
alternative title
Analys av lätta hängbroar för isolerade samhällen
course
VBK920 20151
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Suspended bridge, wind loads, dynamic response, vibrations, cables, FE-analysis, modal superposition.
report number
TVBK-5243
ISSN
0349-4969
language
English
additional info
Examiner: Roberto Crocetti
id
8521252
date added to LUP
2016-04-06 13:23:27
date last changed
2016-04-06 13:23:27
@misc{8521252,
  abstract     = {Light suspended bridges are often used to connect villages or trail systems in geographical areas 
with lacking infrastructure and demanding topology. Different international non-profit 
organizations in collaboration with local promoters are building these bridges with the purpose 
of connecting isolated communities with health care and education. 
The design and construction of these bridges has by and large relied on engineering judgment 
and design conservatism coupled with past experiences of similar construction projects. An 
interest to engage in the designing of similar bridges has been shown from staff at the Division 
of Structural Engineering at the Faculty of Engineering of Lund University. This master thesis 
aims therefore to provide more sophisticated models of suspended bridges as material for future 
work. 
Suspended bridges are suitable to use for long spans, both due to low construction cost and to 
efficient material usage. They can also most often be built without advanced tools or machinery. 
The bridges studied in this thesis are intended for pedestrians and animals which result in a very 
slim design. 
Recommendations mainly from the development organization Helvetas will be compared to the 
Eurocode to investigate if these creates overly conservative designs. These comparisons will be 
made with both hand calculations, the finite element software Brigade/Plus and data from 
existing bridges. 
Vibrations and sways due to wind can be a major problem for light suspended bridges. Due to 
their small dead load in combination with a low lateral stiffness, the sways and vibrations can 
be very large in comparison with more common pedestrian bridges. This could lead to 
temporary inoperability or in worst case structural failure. With the models made in 
Brigade/Plus, wind effects can be analyzed and suitable measures or restrictions can be 
proposed.},
  author       = {Hermansson, Viktor and Holma, Jonas},
  issn         = {0349-4969},
  keyword      = {Suspended bridge,wind loads,dynamic response,vibrations,cables,FE-analysis,modal superposition.},
  language     = {eng},
  note         = {Student Paper},
  title        = {Analysis of suspended bridges for isolated communities},
  year         = {2015},
}