J‐integral determination in riveted beams of a structural old steel by estimation methods*

Abstract

A B S T R A C T This work deals with the application of the J-integral estimation method to cracked riveted beams of old puddle iron. The ductility of some of these materials makes it necessary to use elasto-plastic fracture criteria to assess damage tolerance. This requires a high computational effort because it involves the determination of the J-integral in beams with plates and angles that interact by means of redundant forces dependent on crack size. The J-integral estimation method proposed by the Electric Power Research Institute could reduce this effort provided it were shown to be valid for this type of beam. This work contributes to this end by comparing the J-integral values resultant from the estimation method and a complete finite element modelling of a riveted beam consisting of two angles and a cracked plate made of actual puddle iron from a road bridge more than a century old but still in service. A number of samples removed from the bridge showed that this material failed in a ductile manner when it was fracture tested with fatigue precracked compact specimens, even at temperatures as low as −20 • C. The two types of J-integral values found are in good agreement over the ranges of load and crack size explored.Keywords fracture toughness; J-integral; old structural steel; ductile puddle iron. N O M E N C L A T U R Ea = crack size a = crack growth b = web width E = Young's modulus J ep = elastic-plastic J-integral J ep = estimated elastic-plastic J-integral J IC = fracture toughness as measured at ductile crack growth initiation J el , J pl = elastic, plastic component of J-integral M = applied bending moment M e = reference value of the applied bending moment M M f L = applied bending moment M at fracture initiation n = strain-hardening exponent R p0,2 , R m = yield, ultimate strength u = displacement in a cracked configuration u = estimated displacement in a cracked configuration u el , u pl = elastic, plastic component of displacement in a cracked configuration W , B = specimen width, thickness ν = Poisson's ratio

09.12: Assessment of old mild steel structures related to brittle fracture

“…Such research results have also been published on the international level (e.g. [14] and [15]). While the origin of the steels was mostly given, the test procedure, the used test standards, the dimensions of the test specimens and also partly the test temperature was only insufficiently documented.…”

Toughness of old mild steels

“…The results were published e. g. in [14][15][16] and were used in various concepts to determine the brittle fracture resistance of riveted structures. Some of the research results have also been published on an international level (e. g. [17,18]). While the origin of the steels was mostly given, the test procedure and standards, the dimensions of the specimens and also partly the test temperatures were only insufficiently recorded.…”