Chapter 4: The Construction Process of Segmental Bridges
Erection girder need not rest on the ground, but can also be supported by already existing substructure or superstructure, e.g. the piers of a span that is to be constructed. Project specific design of substructure and superstructure and considerations as e.g. for traffic clearances set the boundaries for erection with erection girders.
Placement of Segments
Figure 4-9: Span-By-Span Erection
CONSIDERATION OF CONSTRUCTION LOADS AND STRESSES
The following sections deal with the relationship between construction loads and the stresses that these induce in structures and the structures themselves while they are under construction and still awaiting completion. The central issue for all considerations is structural safety, meaning failure against structural failure. The generic concept of resistance R that is greater than the most unfavorable combination of load S that induces stresses has been introduced in Section 3.5.2.
Codes require that all construction influences will be properly taken into account during design. Even a professional code applicable for bridges (ACI 1995, p51) in its Section 5.3 only points out that “Consideration should be given to temporary loads caused by the sequence of construction stages, forming, falsework, or construction equipment and the stresses created by lifting and placing precast members.” It assigns the responsibility for the construction scheme, which imposes stresses on the structural members, to the contractor. It is further pointed out that