IJUP08 - Universidade do Porto

Study and design of precast reinforced concrete box-culverts
under high embankments
Daniel Pinto 1
1 Department of Civil Engineering, Faculty of Engineering, University of Porto, Portugal.
Precast reinforced concrete box-culverts (BC) are often used as systems for crossing
highway embankments (materializing hydraulic and pedestrian passages), [1]. Although
this is a simple role, the loadings applied to these structures are rather complex. Due to
soil-structure interaction effects, the state of stress on the culvert depends on the stiffness
of both the structure and the backfill, which is not usually contemplated in the simplified
design methods that assumed that the load applied to the top slab correspond to the
geostatic load. The applied soil pressure is also governed by the BC geometry, the soil
properties and the method and quality of construction [1-4].
A numerical study on reinforced concrete box-culverts behaviour was developed on a
precast commercial BC design for a 10m high embankment. The numerical analyses were
performed using a finite element code, in the DIANA-9.2 program, capable of considering
the nonlinear behaviour of both the soil and the reinforced concrete structure and enabling
the consideration of all the construction stages. New parametric analyses, beyond those
which were accomplished in previous studies, [2, 3] were developed for the identification
of the main parameters influencing the interaction mechanism and to evaluate the BC
structural performance up to failure. These parametric analyses were enclosed on four
principal analyses groups, like changing the soil characteristics, the concrete
characteristics, the reinforced quantity and changing the BC geometry. The influence of
the BC nonlinear behaviour on the interaction mechanism, both in service and ultimate
state conditions, was analyzed and discussed.
The main results show that the soil characteristics have an important influence in the BC
behaviour and the other parameters affect the performance up to failure. The principal
cause of failure is the concrete crushing on the interior corners on the BC walls.
As concluding remarks, it is considered that the soil pressures and the BC nonlinear
behavior are directly related and should be reflected in the design stage in order to achieve
a more rational and economical design.
[1] Bennett, R., Wood, S., Drumm, E., and Rainwater, N. (2005), Vertical Loads on Concrete Box
Culverts under High Embankments, Journal of Bridge Engineering, 10(6), 643-649.
[2] Figueiras, J., Pimentel, M., Costa, P. (2006), Análise do Comportamento e Verificação de
Dimensionamento de Box-Culverts – Relatório Síntese, LABEST-FEUP.
[3] Sang, Pedro A.S. (2000), Comportamento e Modelação Numérica de Estruturas Enterradas de
Betão, Dissertação de Mestrado em Estruturas de Engenharia Civil, FEUP.
[4] Kim, K., and Yoo, C. (2005), Design Loading on Deeply Buried Box Culverts, Journal of
Geotechnical and Geoenvironmental Engineering, 13(1), 20-27.
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