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Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


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Title: Timber Bridges: Design, Construction, Inspection, and Maintenance Chapter 09: Design of Longitudinal Stress-Laminated Deck Superstructures

Source: United States Department of Agriculture, Forest Service, Washington, DC.

Author(s)Ritter, Michael A.;Oliva, Michael G.

Publication Year: 1990  View PDF »

Related Publications: view

Category: US Forest Service Publication

Abstract: Longitudinal stress-laminated deck superstructures consist of a series of lumber laminations that are placed edgewise between supports and are compressed transversely with high-strength prestressing elements (Figure 9-1). The bridges are similar in configuration to glulam or nail-laminated longitudinal decks previously discussed; however, with stress-laminated decks the load transfer between laminations is developed totally by compression and friction between the laminations, rather than by glue or mechanical fasteners. This friction is created by transverse compression applied to the deck using the same type of high-strength steel-stressing elements that are commonly used for prestressed concrete. These elements, which have historically been high-strength steel rods, are placed at regular intervals through prebored holes in the wide faces of the laminations and are stressed in tension using a hydraulic jack. In a typical stress-laminated lumber deck, each rod may have from 80,000 to 100,000 pounds of tension that is transferred into the deck to develop compression between the laminations. The total force from all prestressing elements on a 32-foot-long bridge, for example, may be as high as 1 million pounds. That 1 million pounds compresses the laminations so tightly that the deck behaves like one large, solid plate of wood.

Keywords: Lamination;Bridge;Compression;Stress;Laminated; the timber bridge manual;

File size: 853 kb(s)

Date posted: 06/02/2009
Current FPL Scientist associated with this product
Ritter, Michael A.
Assistant Director

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