SOME ASPECTS OF THE DESIGN AND CONSTRUCTION OF THE 17TH JULY BRIDGE AT NORTHGATE, BAGHDAD.

Abstract

The paper describes some aspects of a four-lane, five-span, prestressed concrete highway bridge of 270 M overall length, together with 570 M of approach structures, which has recently been constructed over the River Tigris in Baghdad as part of the city's plan to cope with an increasing volume of traffic. The change in the city's master plan during the construction stage led to an interesting investigation into local traffic behaviour. The foundations of the bridge are constructed in a river subjected to appreciable annual bed scour, and additional problems were caused by the discovery during construction of ancient remains of the Nebuchadnezzer period, projecting into the river from the right bank. The piles of the contractor's alternative design proved difficult to test satisfactorily and eventually a special test pile had to be designed. The restrictions of the site required a possible method of erecting the bridge to be developed at the conceptional stage of the design. The method, which considerably influenced the design and which was subsequently adopted by the contractor, involved the launching out over the river of precast beams up to 60 M in length by 3 M deep and weighing 280 tons, and their subsequent, accurate positioning for incorporation into the finished continuous deck structure. (TRRL)