Abstract:
When reinforced concrete (RC) box culverts are located under heavy over-burden soil
pressure, the overlying soil loading may produce 'beam bending like' effect in the
longitudinal direction. This bending effect can induce considerable pressure on the
culverts causing excessive deformations and cracks. So far there is no clear
suggestion or provision available in the current codes and specifications to consider
such influence of soil-structure interaction on the stresses developed in the direction
of stream, except the provisions for the minimum reinforcement or distribution
reinforcement. Analysis and design based on the 2-D plane strain condition is
incapable of recognizing such stresses. In the present study, the 3-D finite element
technique has been effectively used to analyze for stresses in the direction of stream
under soil pressures considering soil-culvert interaction.
The FE model developed in this study can be successfully used to investigate the
effect of soil structure interaction on the stresses developed in the direction of stream.
A detailed sensitivity analysis is carried out to consider the influence of different
parameters on the soil-culvert behavior. The sensitivity analysis shows that soil fill
height, length of culvert in the direction of stream, side slope, culvert size etc. have
significant influence on the stresses developed in the direction of stream. Parameters
like coefficient of friction of soil with concrete has little effect on the maximum
bending moment originated at the mid span of the culvert. But it has considerable
effect on the frictional drag along the culvert i.e. on the axial force in the direction
stream. There is no significant change in stresses developed in the culvert when the
extent of soil on both sides of the culvert is more than twice of the width of the
culvert. Based on the findings of the sensitivity analysis, a semi-empirical equation
has been developed to calculate the mid-span moment that may be readily used for
design purpose without going through complicated numerical FE analysis. The
validity of the proposed equation has been established by comparing predicted
moments with those obtained from the FE analysis and it has been found that the
proposed equation predicts moments with reasonable accuracy.
