During fabrication and erection, the section may be completely open at the top, or it may be braced by a top lateral­bracing system connected to the top flanges (Figure 8.2). A composite box girder bridge may take the form of single box, multibox also called twin box, or multicellular box (Figure 8.3). To close the top opening and complete the box, a rein­ forced concrete deck slab is added, which acts compositely with the steel section by means of shear connectors to ensure full interaction between them. During construction, the steel girders are subjected to the wet con­ crete load and other construction loads without the composite action that results from the hardened concrete deck.