“…The weight function method has been widely applied to determine the SIFs of cracked structures since it is able to take complex loading conditions into consideration. 17,18 It has been shown that, if the SIF K ( a ) (1) and the crack face displacement u (1) ( x , a ) of any linearly elastic cracked solid are known as functions of the crack length a for a symmetrical load system (1), then for the same cracked solid subjected to any other symmetrical load system (2) in mode I loading conditions, the SIF K ( a ) (2) can be obtained by the simple integration of the weight function h ( x , a ) and the stress distribution function σ (2) ( x ) 15,16,21,22 where the weight function, independent of σ (2) ( x ), is defined as In equations (1) and (2), a is the half or full crack length for edge cracks and center cracks, respectively; H is a material constant, H = E for plane stress condition and H = E /(1 − v 2 ) for plane strain condition with E the Young’s modulus and v the Poisson’s ratio; K ( a ) (1) and u (1) ( x , a ) are, respectively, the known reference SIF and the crack face displacement in mode I loading conditions for the known load system (1); and σ (2) ( x ) is the stress distribution function across the plane of the crack in the crack free solid subjected to the load system (2).…”