STRENGTH OF ALUMINUM-ALLOY PLATE GIRDERS SUBJECTED TO PATCH LOADING

Aluminium alloys are used in a variety of structural engineering appli cations, such as transportable and lightweight bridges, due to their h igh strength to weight ratio and durability. However, the heat of weld ing may reduce their strength significantly, and necessitate the inclu sion of strength-reduction factors in design calculations. Experimenta l studies of the ultimate resistance of aluminium alloy plate girders to patch loading have indicated that failure generally occurs due to w eb crippling, which is characterized by the formation of plastic hinge s in the loaded flange and yield lines in the web, Theoretical predict ions of ultimate resistance in accordance with BS 8118, the British co de of practice for aluminium structures, based on the buckling of an a ssumed unrestrained web strut, appear unduly conservative when compare d with available experimental results. Theoretical predictions of ulti mate resistance in accordance with EC9, the European code of practice for aluminium structures, based on semi-empirical modifications of mec hanism solutions similar to those presented herein, show good correlat ion with available experimental results. Recent experimental studies o f the ultimate resistance of welded aluminium alloy plate girders to p atch loading are described and discussed. A theoretical procedure for predicting ultimate resistance, based on a mechanism solution for web crippling of steel plate girders, is presented which shows consistent and significantly improved correlation with the test results.