The structural response of box culverts to variable soil compressibility condition was studied in this paper. This was made possible by modelling the soil as springs, and varying the spring stiffness which was represented by the modulus of subgrade reaction of the soil. The results showed that the values of maximum bending moments for gravity actions on box culverts increased linearly with modulus of subgrade reaction, but remained within close values. The results also showed good agreement with results from literature for highly compressible soils. However, for incompressible soil condition, results from standard tables in literature were more conservative with about 10% difference for gravity actions, and 21% difference for lateral actions. The term ‘highly compressible’ that was used in literature for manual analysis was discovered to be more valid for lateral load cases than for gravity load cases. Subsequently, the variations of other action effects such as shear force, axial force, torsion, and soil spring settlement with modulus of subgrade reaction were also studied. Keywords: Box Culvert, Modulus of Subgrade Reaction, Soil Settlement, Staad Pro.

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Coarse aggregates gradings have varying effects on the properties of concrete. Coarse aggregates of sizes 10mm, 20mm and 25mm were used for this study. Sieve analysis was conducted on these aggregates. Their coefficients of curvature (Cc) ranged between 1.01 and 1.19, while the coefficients of uniformity (Cu) ranged between 1.24 and 1.73, showing that they are all uniformly graded. 10mm and 25mm coarse aggregates were mixed in various proportions to produce five different concrete mixes (concrete C1, C2, C3, C4 and C5). Concrete C6 was produced with 100% 20mm and was used as a check. Slump test was performed for each mixture, C1 gave the highest slump height of 88mm. Compressive strengths of the cast concrete cubes were determined after 7- and 28-days curing periods. C4 gave maximum compressive strength of 26.33N/mm2 at 28 days. Increase in the percentages of 25mm aggregates resulted in higher compressive strength and decreased workability.