What type of deck is constructed with timber planks laid flat transversely across the superstructure?

The type of deck being described is indeed a plan deck. This construction technique involves laying timber planks flat and transversely across the bridge's superstructure, providing a level surface designed to support the loads applied to the deck. This method is particularly effective for maintaining the structural integrity and ease of maintenance in bridge construction.

The design allows for quick installation and adaptability, as timber is a readily available material that can be easily worked with on-site. Additionally, plan decks can offer acceptable performance in various environments, making them a popular choice in certain types of bridging applications.

In contrast, the other options reflect different construction techniques or materials that serve various purposes. A nail laminated deck involves layering timber planks that are fastened with nails, offering a different structural behavior and load distribution method. A stress laminated deck typically uses timber members that are glued and mechanically fastened together, aimed at enhancing strength and stiffness. Cast-in-place refers to concrete that is poured and cured on-site to form the deck, a method that provides durability but differs significantly from timber plank construction. Each of these alternatives has unique features suited to specific engineering requirements, emphasizing the importance of selecting the appropriate deck type based on design needs.