RESIDUAL STRENGTH OF ALUMINIUM PLATE GIRDERS WITH SCATTERED HOLES IN THE WEB PANELS.

Modern lightweight transportable bridges are constructed from welded aluminium alloy plate girders. The design of these girders is based on limit state principles where the material is used efficiently so that any damage sustained by the girders may have serious consequences. In view of this, a research study has been undertaken by the authors to investigate the effects of various types of damage upon the collapse behaviour of aluminium plate girders under predominant shear loading. This paper describes that part of the study which concentrated on girders containing a number of small holes scattered randomly over the complete area of the web panels. The proposed method for determining the residual shear capacity of such damaged girders is based on the Cardiff tension field theory for steel girders, modified to allow for the differences in material and geometrical properties between undamaged steel girders and damaged aluminium girders. The main feature of this new method is the use of an equivalent thickness analogy for the quantification of the loss in post-buckling strength caused by the presence of the holes; this allows a damaged panel to be considered as an equivalent intact panel of reduced web thickness and thus enables a damaged girder to be analysed in a similar manner to an intact girder. Validation of the proposed method is based on a series of five tests on damaged girders fabricated from 7019 aluminium alloy. (A)