THE EFFECT OF LATERAL CONFIGURATION ON STATIC AND DYNAMIC BEHAVIOUR OF LONG SPAN CABLE SUPPORTED BRIDGES

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 6, Issue 11, Nov 2015, pp. 156-163, Article ID: IJCIET_06_11_016
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=11
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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___________________________________________________________________________
THE EFFECT OF LATERAL
CONFIGURATION ON STATIC AND
DYNAMIC BEHAVIOUR OF LONG SPAN
CABLE SUPPORTED BRIDGES
Prof. G. M. Savaliya
Assistant Professor, Civil Engineering Department,
Government Engineering College, Surat, Gujarat, India
Prof. (Dr.) A. K. Desai
Professor, Applied Mechanics Department, SVNIT, Surat, Gujarat, India
Prof.(Dr.) S. A. Vasanwala
Professor, Applied Mechanics Department, SVNIT, Surat, Gujarat, India
ABSTRACT
Long span bridge is the demand of every nation and it could be achieved
with use of enhanced materials. With the development of the high strength
materials and techniques for analysis of bridge, long span cable supported
bridge are introduced. Generally, cable supported bridges comprise both
suspension and cable-stayed bridge. Cable supported bridges are flexible in
behavior. These flexible systems are susceptible to the dynamic effects of wind
and earthquake loads. With increasing span of the bridge the flexibility of the
bridge is increasing. Here, attempt is made to improve the rigidity of long
span bridge and presented in this research paper. For enhancing the rigidity
of the bridge in lateral and vertical directions, different configuration of the
cables of long span cable supported bridges is considered in this study. To
understand the response of the long span cable supported bridges, modal Time
History analysis is carried out in SAP2000 software. The behavior of the cable
supported bridges is studied with different configuration of cables in lateral
direction. The behavioral response of the bridge is presented in form of a Time
Period in lateral and vertical direction for structural members of the bridge.
Key words: Cable-Stayed Bridge, Suspension Bridge, Cable-Stayed
Suspension Hybrid Bridge, Cable-Stays Configuration, SAP2000, Modal Time
History Analysis

The Effect of Lateral Configuration on Static and Dynamic Behaviour of Long Span Cable
Supported Bridges
Cite this Article: Prof. G. M. Savaliya, Prof. (Dr.) A. K. Desai and Prof.(Dr.) S.
A. Vasanwala. The Effect of Lateral Configuration on Static and Dynamic
Behaviour of Long Span Cable Supported Bridges, International Journal of
Civil Engineering and Technology, 6(11), 2015, pp. 156-163.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=11
1. INTRODUCTION
The requirement of bridges is increasing day by day with increasing the populations
and their needs. To grant easy transportation in the urban areas long span bridges
necessities are increasing day by day. In the twentieth century the development and
research in the field of the bridge engineering is take place enormously to fulfill the
need of the very long span bridges. With development of new material and techniques
for analysis very long span cable supported structures came in to practice. In general
for very long span bridges the high strength steel cables are used as a structural load
resisting elements. Some aspects of cable supported bridges are illustrated here.
1.1. Cable-stayed bridge
The cable-stays are directly connected to the bridge deck resulting in a much stiffer
structure. A large number of closely spaced cable-stays support the bridge deck
throughout its length, reducing the required depth and bending stiffness of the
longitudinal girder to a minimum thereby allowing the construction of relatively
longer spans. [2]The structural action is simple in concept; the cables carry the deck
loads to the towers and from there to the foundation. The primary forces in the
structure are tension in the cable-stays and axial compression in the towers and deck;
the effect of bending and shear in deck is less influential. For cable-stayed bridge an
iterative approach in which initially the post-tensioning cable forces in the DL
configuration are determined by solving compatible conditions arising from flexibility
matrix of the structure. In the cable-stayed bridge a cable-stays are making variable
angles with horizontal axis, so the forces in the cable-stays are incompatible at
different locations. So, the optimization procedure is utilized to minimize the cross-
sections of the cable system, on the basis of the maximum effects on stress and
displacement variables evaluated on the live load configurations.
1.2. Suspension bridge
A deck of suspension bridge is hanged by vertical hangers, which are connected to
main suspension caternary cables. The main cable is continuous, over saddles at the
pylons, or towers, from anchorage to anchorage. In a suspension bridge, a procedure
to find the initial configuration under dead load is relatively simple as the main
extremities are fixed at earth constraints.
As an outcome, optimization techniques are frequently employed with the purpose
to identify the structural behavior of the bridge with respect more complex external
loads such as aeroelastic and seismic phenomena. However, most of the
methodologies are typically concerned to evaluate optimum post-tensioning forces in
the dead load (DL) configuration, without achieving the complete optimization of the
geometry, the stiffness of the structural elements and thus the costs of construction.
[1]
The requirement of incredible long span bridges is increased day by day with
increase in inhabitants and their needs. To achieve a very long span bridge, use of
high strength material along with novel structural system is essential. In general to

Prof. G. M. Savaliya, Prof. (Dr.) A. K. Desai and Prof.(Dr.) S. A. Vasanwala
achieve longer span bridges, cable-stayed and suspension systems are used, in which
the cable-stayed bridge has better structural stiffness and suspension bridge has ability
to offer longer span. Combination of above two structural systems could achieve a
very long span cable-stayed suspension hybrid bridge.
1.3. Cable-stayed suspension hybrid bridge
The cable-stayed suspension hybrid bridge is presented as an alternative to long span
cable-stayed and suspension bridges. Hybrid cable-stayed suspension bridge is
combination of cable-stayed bridge and suspension bridge as shown in Fig. 1.
Figure 1 hybrid cable-stayed suspension bridge
The idea for this innovative system was first introduced by Dischinger in 1949,
Schlaich 1988; Gimsing 1988; Lin and Chow 1991.[1] There after a very little work is
done on this system of combined bridge.
1.3.1. Advantages of Cable-stayed suspension hybrid bridge
Advantages of combining both the systems were discussed below. By combining both
the system of cable supported bridges following advantages could be achieve [3]
1. As compared to the suspension bridge with the same span length the partly
suspension portion is replaced by cable-stayed portion and suspension portion can be
shortened, so the tensional forces in the main caternary cables are greatly decreased.
2. Reduction of suspension portion in main span decrease in the construction costs of
the main cables, massive anchors, difficulty to construct them in water, and therefore
makes it possible to build in the soft soil foundation also.
3. As compared to cable-stayed bridges with the same span length, the cable-stayed
portion is also greatly shortened. These results, the reduced height of tower, length of
stays and the axial forces in the deck.
4. In addition to these, cantilevers during erection are also shorted and wind stability of
the bridge under construction may therefore improve.
Therefore Hybrid cable-stayed suspension bridge becomes an attractive alternative
in the design of long span bridge systems.
So, the long span cable supported bridges like cable-stayed bridge, suspension
bridge and cable-stayed suspension hybrid bridge with different lateral configuration
is considered in the current study.
1.3.2. Analysis of cable supported bridges
Long span cable supported bridge highly are defined through large number of cable
elements which lead to highly statically indeterminate structures. So, post tensioning
forces in cables and cross sectional area of the cables can be considered as design
variables, which must be determined to identify the bridge configuration under dead
and live loading for economical structural steel quantity and optimum performance of

Supported Bridges
structural elements. The analysis of cable-stayed suspension hybrid bridge is a new
area of research. The hybrid bridge is consists of the main cables, cable-stays and
hangers in a bridge, which present better performances than conventional ones based
on pure suspension and cable-stayed configurations.
2. BRIDGE CONFIGURATIONS
The bridge configurations considered in the current study for cable-stayed bridge,
suspension bridge and cable-stayed suspension hybrid bridge is explained here. The
bridge configuration is based on bridge of the east channel of Lingding Strait in China
[5] having central span = 1400 m, two side spans = 319 m and height of
pylon=258.986 m. The behavior of bridge is studied for different cable configuration
and thus pylon height is considered as a constant.
Figure 2 Geometric configuration of cable-stayed suspension hybrid bridge
(CSSHB)
In current study as shown in Fig.2, the bridge having central span = 1400 m, two
side spans = 312 m and pylon height = 258.986 m is studied with suspension to span
ratio 0.5 means suspension portion length is 700m in centre of main span. Table 1
shows the material properties of different elements of bridge.
Table 1 Cross-sectional properties of cable-stayed suspension hybrid bridge members [4]
Members
E
(Mpa)
A
(m2)
Jd
(m4)
Iy
(m4)
Iz
(m4)
M
(Kg/m)
Jm
(Kg.m2
/m
)
Girder 2.1x105
1.761 3.939 193.2 8.33 26340 2.957x106
Tower C 3.3 x104
30 350 220 320 78000 5.7x105
Tower TB 3.3 x104
10 150 70 70 26000 4.7x105
Main Cable CS 2.0 x105
0.3167 - - - 2660.3 -
Main Cable SS 2.0 x105
0.3547 - - - 2979 -
Hanger Cable 2.0 x105
0.0064 - - - 50.2 -
Stayed cables 2.0 x105
vary - - - vary -
Where, E - Modulus of Elasticity; A - Cross section area; M - Mass per unit
length; Jd - torsional constat; Iy-Lateral Bending moment of inertia; Iz-Vertical
Bending moment of inertia; Jm – mass moment of inertia per unit length
Figure 3 presents cable-stays at different positions from the pylon to center of the
span with the assigned cross sectional area in m2
. At the pylon the cable stays no is 0
and as the deck span is moving towards center of the main span the cable-stays no is
increasing towards the 39, in graph shown below in the horizontal axis no of cable-
stays are presented and in vertical axis respective area of the cable-stays in m2
. Here,
distance between two hanger cables λ is 17.941 m

Prof. G. M. Savaliya
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Figure 3 Cable Area assigned to St
2.1. Arrangements of stayed cable in cable
To study the effect of stay cable planes arrangement on dynamic strength, vertical
configuration of cable-stays can be revised the same as in lateral directions
outward angles with vertical axis and inclined inward angels with vertical axis.
stay cables of bridges can be arranged to be vertical or inclined with vertical axis in
lateral direction, which can be adjusted by lateral configuration of pylo
connection with cable-stays.
configuration of the cables are incorporated with special inclination of stayed cable
with the vertical axis passes through the connection of deck and the cable
Here the considered configurations are generated by offering the inclined
inclination angle. The cable configurations are generated by assigning offsets at the
top of the cables-stays in pylon as 14m and respective inclination angles assigned
4.264º with the vertical axis passes through connection between the deck and cable
stays. The inclination is assigned in both directions inward direction from the vertical
axis as well as outward direction also. In the below Figure
angle profiles in inward and out ward direction
the cable-stays with vertical axis is shown.
Inward inclination θ=4.264
Figure 4 the cable-stays having
ET/index.asp 160 editor@iaeme.com
Cable Area assigned to Stay Cables from pylon to center of span
Arrangements of stayed cable in cable-stayed bridge
stays can be revised the same as in lateral directions
outward angles with vertical axis and inclined inward angels with vertical axis.
lateral direction, which can be adjusted by lateral configuration of pylo
stays. In this research paper the significant stayed cable
with the vertical axis passes through the connection of deck and the cable
stays in pylon as 14m and respective inclination angles assigned
.264º with the vertical axis passes through connection between the deck and cable
axis as well as outward direction also. In the below Figure 4 the cable
and out ward direction generated by providing offset at top of
stays with vertical axis is shown.
θ=4.264º θ=0º outward inclination
stays having vertical, inward and outward angles with vertical axis
Prof.(Dr.) S. A. Vasanwala
editor@iaeme.com
ay Cables from pylon to center of span
stays can be revised the same as in lateral directions inclined
outward angles with vertical axis and inclined inward angels with vertical axis. The
lateral direction, which can be adjusted by lateral configuration of pylons top and its
In this research paper the significant stayed cable
with the vertical axis passes through the connection of deck and the cable stays.
stays in pylon as 14m and respective inclination angles assigned is
.264º with the vertical axis passes through connection between the deck and cable-
the cable-stays with
generated by providing offset at top of
outward inclination θ=4.264º
angles with vertical axis

Supported Bridges
Cable stays are provided with above vertical, inward and outward angle make
with vertical axis passes through joints of deck and cable-stays.
3. LOAD ASSIGNMENTS
Structural elements of bridge are assigned with load cases as shown in below Table 2.
Table 2 loads assigned to the different members
Type of the load Value of Assigned Load Element Assigned
Dead Load 97.980 kN/m Deck
SIDL 50.0 kN/m Deck
Live Load 34.650 kN/m Deck
4. STATIC AND DYNAMIC BEHAVIOR
Nonlinear static and dynamic analyses are carried out to determine the response of the
cable-stayed bridge, suspension bridge and cable-stayed suspension hybrid bridge.
Here, geometrical nonlinearity of the cable supported bridge is more influencing
factor in analysis. The P-Delta effect can be a very important contributor to the
stiffness for considering geometrical nonlinearity of cable structures. The lateral
stiffness of cables is due almost entirely to tension, since they are very flexible when
unstressed. It is important to use realistic values for the P-delta load combination,
since the lateral stiffness of the cables is approximately proportional to the P-delta
axial forces.
Dynamic behavior of bridge can conclude by dynamic analysis. Hence, Modal
analysis is carried out to recognize the dynamic behavior of bridge. In modal analysis
each modal load case results in a set of modes. Each mode consists of a mode shape
(normalized deflected shape) and a set of modal properties like Time periods and
Frequencies of the structure. Results are presented for different length of suspension
to main span ratio for cable-stayed suspension hybrid bridge.
4.1. Analysis results and discussions
Static and dynamic analyses are carried out to determine the response of the structure
for different types of loadings. Here, different cable layouts of the cable supported
bridges are considered for the study. The effect of these considered layouts can be
judge by the structures response to the applied load cases. Each mode consists of a
mode shape (normalized deflected shape) and a set of modal properties like Time
periods and Frequencies of the structure.
4.2. Result Parameters Considered For Parametric Study
Result parameters considered to understand the dynamic response of the bridge is
presented here. The geometrical parameter considered in this paper is effects of Cable
stays configuration in lateral directions, which can be obtain by changing top
orientation of the cables and form of pylon.
Parameters considered for comparison of results in parametric study are as
follows:
1. Time period of the bridge for different mode shapes in Lateral mode shapes,
2. Time period of the bridge for different mode shapes in Vertical Mode shapes,
3. Time period of the bridge for different mode shapes in longitudinal modes shapes
with different cable-stayed configurations etc.

4.3. Results considering cable-stayed configuration as geometrical
Parameters of cable-stayed bridge
Here, for the different cable layout configuration, the response of the structure in the
form of time periods of different mode shapes is presented in below given tables.
Table 2 Time period of the modes of the cable-stayed bridge with different cable layout
configurations
Layout Cable-stayed bridge
Cable-Stayed suspension
hybrid bridge
Suspension Bridge
Mode
Shape
Inward
4.264º
Vertical
0º
Outward
4.264º
Inward
4.264º
Vertical
0º
Outward
4.264º
Inward
4.264º
Vertical
0º
Outward
4.264º
Lateral_1 11.56 12.38 14.14 12.42 13.15 14.59 12.00 12.79 14.41
Lateral_2 7.82 10.35 10.80 7.81 10.41 11.12 7.80 10.31 10.87
Pylon_1 7.93 11.21 13.39 7.97 11.24 13.43 7.97 11.24 13.45
Vertical_
1
4.71 4.74 4.77 7.28 7.05 7.28 7.28 5.20 7.28
Vertical_
2
4.08 4.13 4.19 4.82 4.87 4.89 5.03 4.04 5.09
Longi._1 5.09 5.13 5.19 5.40 5.48 5.47 4.81 4.81 4.82
5. CONCLUSIONS
From the analysis carried out with the different three cable-stays configurations the
follwing observations are found. The dynamic analysis of cable-stayed ridge,
suspension bridge and cable-stayed suspension hybrid bridge (CSSHB) with
suspension to main span ratio 0.5 (Sup/span=0. 5) is carried out to identify the
behaviour of the bridge with the lateral configuration of cables. The following results
are obtained from the analysis:
1. From the results of principal lateral bending mode time period of CSSHB
(Sup/Span=0. 5) with the considered configuration of cables in lateral direction, It is
found that the time period increases 9.87 % if the vertical configuration is replaced by
outward inclination of 4.264°.
2. The time period of bridge in lateral direction reduces effectively by provision of
inward inclination to cables. From the figure it is found that by the provision of
inward inclination of 4.264° the lateral bending time period is reduced 5.66%.
3. The pylon time period of the bridge reduces 29.10 %, if the inward inclination of
4.264° is provided instead of vertical configuration. The reduction in the time period
is also due to the change in shape of the pylon to ‘A’ shape.
4. From the Table, it finds that the pylon time period of CSSHB (Sup/Span=0. 5)
increases by 16.31 % if vertical cables are replaced by outward inclination of 4.264°.
Here, for the provision of outward inclination to cables the shape of the pylon is also
changed to inverted ‘A’ shape and thus the stiffness of the bridge is reduced. The
longitudinal and vertical mode shape time period not changing effectively with
change in the lateral configuration of bridges.

Supported Bridges
REFERENCES
[1] Gimsing, N. J.(1983), “Cable-Supported Bridges—Concept and Design,” John
Wiley & Sons, Inc., New York.
[2] Podolny, W.(1986) “Cable suspended Bridges,”, John Wiley & Sons, Inc., New
York.
[3] Zhang Xin-jun(2006), “Study of design parameters on flutter stability of cable –
stayed–suspension hybrid bridges”, Wind and Structures, Vol. 9, No. 4 pp. 331-
344.
[4] Zhang Xin-Jun(2007), “Investigations on Mechaniscs performance of cable-
stayed suspension hybrid bridges”, Wind and Structures, Vol. 10, No. 6 pp. 533-
542.
[5] XIAO, R. C., “Research on design of cable-stayed suspension hybrid bridges”,
China civil engineering journal, 33(5), (2000), pp. 46-51.
[6] Abdul Kareem Naji Abbood. A Comparative Technical and Economical Study
To Different Options Location For Bridge and Its Approaches, International
Journal of Civil Engineering and Technology, 4(6), 2013, pp. 214-229.
[7] Dr. K.v. Ramana reddy. Aerodynamic Stability of A Cable Stayed Bridge,
International Journal of Civil Engineering and Technology, 5(5), 2014, pp. 233 -
239.

THE EFFECT OF LATERAL CONFIGURATION ON STATIC AND DYNAMIC BEHAVIOUR OF LONG SPAN CABLE SUPPORTED BRIDGES

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