Sun Qitang, Research on Spatial Mechanical Behavior of

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25 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Sun Qitang, Research on Spatial Mechanical Behavior of
Separated Double Box Girder Bridge with Wide Deck Stiffened
by Single Arch-rib, Fujian: Master degree thesis of Fuzhou
University, 2009

Abstract
In recent years, with the rapid development of transportation and
urbanized construction, separated double box girder bridges with wide deck
have been designed and constructed in China. Wanbian Bridge in Fuzhou,
with 34m wide deck, is the first separated double box girder bridge with wide
deck stiffened by single arch-rib in China. The main bridge is composed of two
girders which have variable cross-section from support to mid-span. The two
girders, only connected by transverse beam and V-shaped piers, are stiffened
by concrete-filled steel tubular arch rib in the middle of the cross-bridge. The
bridge is complicated, and the spatial effect is dominated. Taking this bridge as
a case study, the mechanical behavior of double box girder bridge with wide
deck stiffened by single arch-rib is studied in this thesis. This research focus
on the following contents:
Firstly, a finite element model of Wanbian Bridge is established. By
comparing the finite element model results with on site dead load test results,
the finite element model of the whole bridge is validated.
Secondly, by using the finite element model, the effect of arch rib on the
internal force of whole bridge is studied. The results show that by installation of
the arch rib, the transverse beam stress is increased by 14%, the deflection of
the main girder is reduced by 13% to 18%, and the longitudinal stress of the
girder is reduced by 13% to 25%. Thus, the installation of the arch rib can
make the longitudinal stress of the Wanbian Bridge girder decreased.
Then, based on the above conclusion, the effect of arch rib stiffness and
transverse beam stiffness on the mechanical behavior of such kind of bridge is
discussed. It is indicated that arch rib stiffness increased reasonably in a
certain range is beneficial to the longitudinal stress of the main girder. However,
when the stiffness ratio between arch rib and main girder is larger than 1/700,
the advantageous effect of the arch rib stiffness on the longitudinal stress of
the main girder is not obvious enough. The analysis also indicates that thicker
transverse beam is helpful to reduce the cross bridge stress and the
transverse beam stress. But when the thickness of transverse beam is
increases to 300% of the original, the beneficial effect on the transverse beam
itself will be weakened and make the dead load of the whole bridge increased.
Finally, for the mechanical behavior of transverse beam of separated
double box girder bridge stiffened by arch-rib, the elastic supported beam
method, considering the stiffness of both arch and girder, which is more close
to the actual mechanical behavior of the transverse beam than the mothed
only considering stiffness of girderis, is proposed by comparing with the results
from FE analysis.