Discussion. Some Aspects of the Design and Construction of the 17th July Bridge at Northgate, Baghdad.

Abstract

At what stage of the work were the archaeological discoveries made? Presumably there were discussions between the Iraqi Ministry of Construction and the organization responsible for archaeological preservation. It would be of interest to know whether the Engineer was consulted on this matter and, for example, if he was allowed to give consideration to the possible redesigning of the bridge, perhaps by increasing the spans, to avoid destruction of the ancient brickwork. M r P. L. Martin, Rendel, Palmer & TrittonThe foundation design for the bridge was dominated by consideration of the extraordinary scour conditions. Design studies therefore centred on pile capacity under both vertical and lateral load at times of flood. This discussion contribution enlarges on the pile testing which was camed out. 45.The first two pile tests did not confirm either that the permanent piles would have adequate bearing capacity or that settlements under working load would be within acceptable limits. A further test was made. The test had two objectives. The first was to prove the effectiveness of the unorthodox procedure for cleaning the base of the pile shaft. The second was to determine the relationship between end bearing capacity and the standard penetration test data obtained from the site investigations. An extrapolation could then be made to determine base capacity under scour conditions. Ideally this test would have been made on a pile founded at -9.0 m, but, even if skin friction could have been eliminated entirely, it would have been necessary to increase the test load to compensate for the increased overburden pressure (from +5.0 m to river-bed level) over that occurring at maximum scour. Furthermore, a test pile could not by then