Stability of the bracing system of a compositebox girder bridge during construction

Abstract

The paper describes how steel box girder bridge segmentsweighing 130 metric tons and measuring 54 m werefabricated and transported by road in the old city of Cairo,a city of 16 million inhabitants, from a fabrication yardsituated at about 32 km away from the project location.The stability of the compressed flanges of the open boxbefore pouring the concrete of the slab is a problem thatneeds to be investigated. The torsional rigidity of the boxduring the construction phase is not satisfactory. Anadequate temporary bracing system is thus requiredlinking together the two compressed flanges. The rigidityof the bracing members will compensate the excessiveflexibility of the open box. It is expected that the flexuralcarrying capacity of the box once provided with bracingwill increase significantly.Needless to say that transporting eight full oversized boxgirders, each weighing 130 tons and measuring 54 m fromthe fabrication yard to the site situated about 32 km awaywas a real challenge. At last, the box girders welded in shop enable a considerable reduction of fieldwelded joints and help also delivery of the project as-planned just on-time