MODAL ANALYSIS OF VERTICALLY CURVED CONCRETE FLYOVER BRIDGES
MODAL ANALYSIS OF VERTICALLY CURVED CONCRETE FLYOVER BRIDGES
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Date
2016-08
Authors
JA’E, Idris Ahmed
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Abstract
The effectiveness and sensitivity of vertically curved concrete flyover bridge (VCCFB) profile
is presented. Modal analysis was conducted on three VCCFB models; one for a profile
achieved using horizontal beams, profile achieved using slightly curved beams and a profile
achieved using combination of straight and curved beams. Twelve vibration mode shapes
were recorded with corresponding natural frequencies for each model. In each mode, a
model with a profile using straight beams were found to have higher natural frequencies
with major differencesin modes 2, 6 and 8 corresponding to 2.26, 3.01 and 2.87% differences
from the model with curved beams respectively. Also, major differences were recorded in
modes 2, 3 and 5 corresponding to 6.31, 5.51 and 4.24% differences in natural frequencies
from model with combine beams when using CSiBridge (2015) software. Three vehicles were
simulated each passing the bridge for a period of 10 seconds per lane at the same speed of
10, 20, 30, 40, 50km/h and at varying vehicular speeds of 45, 50, 60km/h and 60, 65,70km/h
respectively. The response spectrum from time history analysis conducted for the three (3)
vehicles moving on each of the model were plotted. The vertical component of acceleration
was compared with the Irwin (1979) base curve for human perceptibility threshold. The
profile achieved using a combination of straight and curved beams were found to induce less
vibration compared to profiles achieved using straight and slightly curved beams. These
result thus indicate that profiles of VCCFB achieved using combination of straight and
slightly curved beams at the cusp induced less vibration compared to profiles achieved with
straight or slightly curved beams. As such the use of combine geometry precast beams should
be encouraged in achieving vertical profiles for this class of bridges.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF
MASTERS OF SCIENCE DEGREE IN CIVIL ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING, FACULTY OF ENGINEERING,
AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA.
Keywords
MODAL ANALYSIS,, VERTICALLY CURVED CONCRETE FLY OVER BRIDGES