Geometric Shape Control of Long Span Steel and Concrete Con-tinuous Composite Structure Box Girder at Construction Stage

The steel and concrete continuous composite structure box girder of Contract B4,Shanghai Changjiang River Tunnel and Bridge Project is currently the largest composite girder structure in China and the world advanced construction techniques,such as those of prefabrication of the structure at girder yard and erection of the structure by floating vessel at pier site,have been applied.As it was designed,the composite box girder was preset with longitudinal gradient and was to be arranged on the curve with different curvature radii,the geometric shape control of the girder in the construction was therefore very complicated.This paper presents the measures and effect of geometric shape control of the girder at various critical construction stages of assembling of each steel girder block,assembling of the girder blocks into a full span for lifting and erection,compositing of the steel and concrete structures and closure of the girder at pier top.