How is shrinkage considered in RC arch design?

Shrinkage is typically evaluated as an equivalent uniform drop in temperature (often taken as 15°C) affecting the arch rib.

Does this standard cover masonry or steel arches?

No, IS 4090 is specifically restricted to the design of reinforced concrete arches.

What secondary stresses must be checked for hingeless arches?

Designers must check stresses arising from temperature variations, concrete shrinkage, elastic rib shortening, and differential support yielding.

IS 4090

: 1967

Criteria for design of reinforced concrete arches

CurrentSpecializedCode of PracticeStructural Engineering · Special Structures

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This code establishes the design criteria for reinforced concrete arches, covering hingeless, two-hinged, and three-hinged configurations. It provides structural analysis guidelines, detailing how to account for primary loads as well as secondary effects like temperature gradients, concrete shrinkage, rib shortening, and support yielding.

Criteria for design of reinforced concrete arches

Quick Reference Values

Equivalent temperature drop for concrete shrinkage15 °C

Coefficient of thermal expansion for concrete11 x 10^-6 / °C

Minimum reinforcement requirementAs per IS 456

Key Formulas

H = (∫ M' y ds / EI) / (∫ y² ds / EI) — Horizontal thrust for two-hinged arch

Shrinkage effect = Equivalent to uniform temperature drop

Practical Notes

In hingeless arches, rib shortening and shrinkage act similarly to a temperature drop and induce significant secondary bending moments that must be explicitly calculated.

For optimal and economical design, the centerline of the arch profile should ideally coincide with the funicular polygon for the primary dead loads to minimize flexural stresses.

While this code covers arches generally, highway arch bridges are predominantly governed by IRC codes (e.g., IRC:112); IS 4090 is typically applied to architectural roofs, industrial structures, and non-highway applications.