Diagnosis of and remedy for imperfection sensitivity of arch bridges

Unless the hangers of arch bridges are sufficiently stiff, such bridges are imperfection sensitive [1]. Increasing the stiffness of the hangers, such structures eventually become imperfection insensitive. The mathematical definition of imperfection insensitivity follows from a series expansion of the dimensionless load parameter Δλ(κ, η), relative to the stability limit λ = λ S , given as [2] 1 Δλ(κ, η) = λ 1 (κ)η + λ 2 (κ)η 2 + λ 3 (κ)η 3 + O (η 4 ), where λ 1 , λ 2 , … are coefficients depending on the stiffness of the hangers representing the design parameter κ and η is a path parameter describing the postbuckling path. A necessary condition for imperfection insensitivity is [3] 2 λ 1 (κ) = 0   ∀κ. If, for a specific value κ of κ, also 3 λ 2 (κ= κ ) > 0, then the structure is imperfection insensitive for κ= κ . It will be shown numerically that the increase of the stiffness of the hangers is the remedy addressed in the title of the paper. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)