الفهرس 
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Abstract
In most bridges, where span length limits the use of concrete beams, the steel fabricated BUS beams are the common material. The two main methods used in Egypt to fabricate BUS beams are: MAG and SAW. The main problem confronting fabrication of BUS beams is Distortion. Distortion is the result of high temperature and residual stresses during welding. The amount of distortion is checked against limits set up by codes and the produced BUS beam may be rejected by project consultant when a distortion measurement exceeds the limits. In this work, after reviewing the types, causes and methods applied to reduce distortion, a comparison between the amount of distortion produced by the two main welding methods used in fabricating BUS beams MAG and SAW has been conducted. The two methods where applied to fabricate the middle part of main girder beam for bridge El_Mahomdia No 5 where its length is 18 m, the lower flange is 50 mm thick; upper flange is 20 mm thick. and the web is 25 mm thick. In MAG welding, its wire electrode was 1.2 mm diameter, current 190 – 210 A, welding speed 300 mm / min and welding joint was complete in 6 passes. In SAW welding, its wire electrode was 4 mm diameter, current 600 A, welding speed 700 mm / min and welding joint was complete in 1 pass. After fabrication there are three forms of distortion were measured, bowing distortion, buckling distortion and angular distortion. Measurement detected that Bowing distortion produced by both methods are small and proved to be within the allowable limits, Buckling distortion has not been detected in both methods of welding. However, Angular distortion is most common form of distortion occurring after welding by both SAW and MAG, the amount of angular distortion produced by MAG is far less than that produced by SAW. After welding by SAW; angular distortion had exceeded the allowable limits of the Egyptian code.