seminar presentation about stress ribbon bridge

1. KAISER AHMAD MALIK
O7-CE-2012
Department of Civil Engineering
COET,BGSBU.

2.  Motivation
 Introduction
 Finsterwalders bridge theory
 Form of structure
 Construction procedure
 Comparision with simple suspension bridge
 Modified stress ribbon bridges
 Advantages and applications
 conclusion

3.  ‘’Stress ribbon bridge philosphers,thinkers
,intelectuals all appeal please build bridges
and not walls between different communities
to achieve universal brotherhood’’

4.  Stress ribbon bridges are slender ,concrete
deck segments placed on bearing cables in
shape of catenary
 consists of slightly sagging tensioned cables
bedded in a concrete slab that is very thin
compared with the slab
 It’s a kind of suspension structure where the
cables are tensioned so tightly that traffic can
be placed on the concrete slab embedding
cable
 Typically made of concrete reinforced with
steel tensioning cables

6. Stress Ribbon Bridge
West Golf Cart Bridge
West Golf Cart
Bridge
Sacramento River Trail
Pedestrian Bridge
Rogue River
Pedestrian Bridge
McLoughlin Boulevard
Pedestrian Bridge
Lake Hodges Bridge

7.  Stress Ribbon Bridge uses the theory of a catenary
transmitting loads via tension in the deck to abutments
which are anchored to the ground. This concept was first
introduced by a German engineer Ulrich Finsterwalder.
 The stress ribbon itself is a reinforced concrete slab with a
thickness of about 10 inches (25.4cm). This reinforcement
consists of three to four layers of 1 inch (2.5cm) to 1 ¼ inch
(1.2cm) diameter, high strength steel.

8.  Precast concrete planks with bearing tendons
to support them during construction
 Joints between planks are sealed with
concrete
 To reduce dead load and horizontal forces at
the abutment deck depth is kept minimum
 The prestressing tendons transfer horizontal
forces in to the abutments and then to
ground using ground anchors

10.  Consists of abutments to transfer horizontal
forces from deck cables into ground via ground
anchors
 The ground anchors are tensioned before and
after the erection of deck
 The soil pressure ,overturning and sliding has to
be checked for construction as well as permanent
condition
 Pedestrains,temperature and wind load can cause
large changes in the B.M close to the deck near
abutments and accordingly fatigue and
crackwidths are to be considered

11. Supports:
• Cables are pre-tensioned by anchoring into support structure,
hence this region is highly stressed.
• Performance may be improved by construction of:
i) flexible saddle
ii) parabolic haunch
iii) intermediate arch support
Stress Ribbon Bridge

12.  Rock base is a prerequisite
 In some cases where the soil conditions do
not permit use of anchors ,piles can also be
used
 Combination of drilled shafts and anchors
can also be used where horizontal
deformation is significant
 Battered micropiling is another alternative
which can resist load from ribbon because of
its compression and tension capacity

13.  Contrary to simple suspension bridge ,where
cables carry loads ,in stress ribbon, by
tensioning the cables and the deck between
abutments ,the deck shares axial tension
forces .
 Unlike the simple suspension bridge the
ribbon is stressed in compression ,which
adds stiffness to the structure
 Unlike suspension bridge it does not tend to
sway and bounce

14. ABUTMENTS ARE BUILT
BEARING CABLES HUNG BETWEEN THEM
PRECAST PLANKS SLID ALONG THE CABLES
CONCRETE PORED BETWEEN PLANK JOINTS
ALLOWED TO HARDEN
BRIDGE READY FOR PUBLIC USE

15. Deck:
 Stress Ribbon Bridge :
Lake Hodges Bridge, USA

16. Deck:
• Might be pre-fabricated or cast in-situ
• Stressed only by normal forces hence might be reduced by
waffles
• Integrated with end and intermediate supporting
construction so as to work as a composite structure.
Stress Ribbon Bridge

17. STRESS –
RIBBON
BRIDGE
STIFFENED
BY ARCH
STRESS-RIBBON
BRIDGE
SUSPENDED ON
ARCH

18.  It was designed by prof.Strasky
 Due to dead load ,the horizontal forces both in arch
and in the stress ribbon have same magnitude ,but
they act in opposite direction
 After post-tensioning the stress-ribbon and arch
behave as one structure
 Therefore foundation is loaded by only vertical
reactions

19.  External bearing cables stiffen the
structure both in the vertical and
horizontal directions
 Horizontal movements caused by live
load are eliminated by stoppers which
allow only horizontal movement due
to temperature changes and creep and
shrinkage of concrete

20.  The main advantage is that they can be
erected independently from the existing
terrain ,hence have minimum environment
impact
 Economical, aesthetic and ensure visually
pleasing end result.
 Can be erected without false work or shoring
 No bearings or expansion joints used

21.  These bridges are versatile and adaptable
structures
 They are sustainable structures since not
much material is used in the deck
 Structurally efficient ,aesthetic, yet cost
effective
 Easy to assemble and quick to erect
 Deck slab made of precast concrete so
require no scaffolding