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Two-Dimensional Analysis of Cable Stayed Bridge under Wave Loading

  • Madhuri Seeram
  • Y. Manohar
Original Contribution

Abstract

In the present study finite element analysis is performed for a modified fan type cable-stayed bridge using ANSYS Mechanical. A cable stayed bridge with two towers and main deck is considered for the present study. Dynamic analysis is performed to evaluate natural frequencies. The obtained natural frequencies and mode shapes of cable stayed bridge are compared to the existing results. Further studies have been conducted for offshore area application by increasing the pylon/tower height depending upon the water depth. Natural frequencies and mode shapes are evaluated for the cable stayed bridge for offshore area application. The results indicate that the natural periods are higher than the existing results due to the effect of increase in mass of the structure and decrease in stiffness of the pylon/tower. The cable stayed bridge is analyzed under various environmental loads such as dead, live, vehicle, seismic and wave loading. Morison equation is considered to evaluate the wave force. The sum of inertia and drag force is taken as the wave force distribution along the fluid interacting height of the pylon. Airy’s wave theory is used to assess water particle kinematics, for the wave periods ranging from 5 to 20 s and unit wave height. The maximum wave force among the different regular waves is considered in the wave load case. The support reactions, moments and deflections for offshore area application are highlighted. It is observed that the maximum support reactions and support moments are obtained due to wave and earthquake loading respectively. Hence, it is concluded that the wave and earthquake forces shall be given significance in the design of cable stayed bridge.

Keywords

Finite element method Modal analysis Wave force Earthquake force Airy’s wave theory Morison equation 

List of symbols

Ah

Design horizontal seismic coefficient

Cd

Drag co-efficient

Cm

Inertia co-efficient

d

Water depth

D

Diameter of fluid interacting pylon

F

Wave force per unit length

H

Wave height

I

Importance factor

k

Wave number

[K]

Stiffness matrix of the structure

L

Wave length

[M]

Mass matrix

[Ma]

Added matrix mass

ρ

Mass density of sea water

R

Response reduction factor

Sa/g

Average response acceleration coefficient

T

Wave period

t

Time step

u

Horizontal water particle velocity

\(\dot{u}\)

Horizontal water particle acceleration

VB

Seismic base shear

W

Seismic weight of the structure (Dead Load + 50% of Live Load)

ω

Wave frequency

x

Distance of the pylon from origin

\(\left\{ {\ddot{X}} \right\},\left\{ X \right\}\)

Acceleration and displacement of the structure

z

Depth of the pylon from origin

Z

Seismic zone factor

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Copyright information

© The Institution of Engineers (India) 2018

Authors and Affiliations

  1. 1.Department of Civil EngineeringJNTUKKakinadaIndia
  2. 2.CJIT CollegeJanagaonIndia

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