A study on the effect of overfill design on the structural behaviour of precast concrete closed spandrel arch bridge
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Date
2018-06
Authors
Jing, Gan Ka
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Abstract
Arch bridges are gaining popularity since the introduction of precast concrete technology.
Closed spandrel arch bridge is one type of precast arch bridge that consists of earth
materials that is filled between the spandrel walls and the top of the precast arches.
Among the backfilling materials, lean concrete is good in providing strength and rigidity
for the arch, yet it comes with a higher cost. In order to achieve a more economical design,
it is crucial to understand the structural behaviour of the precast concrete arch under
different overfill design. Three types of models have been analysed including model with
varying thickness of lean concrete overfill along the arch, model with varying thickness
of lean concrete buttress support built adjacent to the end of the arch and model with
interchange of soil and lean concrete layers backfill and different cut slope distance. The
analysis was carried out using finite element analysis software, PLAXIS. The axial force,
shear force, bending moment and deflection of the arch for different models were
observed. It is found that models with lean concrete fill along the arch are effective in
reducing the overall forces and bending moment while models with lean concrete
buttress support are effective in reducing the maximum shear forces and hogging
moment only. On the other hand, the models with interchange of lean concrete and soil
layer backfill are inducing higher forces and bending moment to the arch. The cost
reduction of steel reinforcement required and cost for replacement of soil fill with lean
concrete was also calculated to estimate the effectiveness of the model. The model with
lean concrete of 400mm thick at support and 100mm thick at crown lying along the arch
panel and model with lean concrete buttress support of 1.0m width and 1.0m height show
the highest reduction of cost required.