Timber bridges play a critical role at local, state, and national levels. They provide rapid and cost-effective transportation solutions. To that end, this bulletin addresses the benefits of constructing bridges with timber, including low carbon footprint, short construction time, environmentally benign aesthetics, high strength-to-weight ratio, off-site fabrication, extended service life, long spans, and favorable economics. Methods for improving timber bridge durability and protection are critical aspects of this bulletin. Physical, chemical, and design-based protection strategies against biotic organisms and abiotic stressors, methods of protection and maintenance as well as choice of structural form are included in this document. Options for use of hardwood species, treatment techniques, connection details, and deck design are described. Nationally recognized standards, including AWPA, ASTM, and AASHTO are referenced to facilitate knowledge transfer. Examples of timber bridge construction from around the world are illustrated. It is hoped that this bulletin will inspire, promote, and educate many stakeholders, designers, supervisors, and engineers in the field of timber bridges for years to come..

Pest control operators in Oregon were surveyed to examine the occurrence of carpenter ants and other wood destroying organisms in structures. Carpenter ants frequently occurred in the coast and Willamette valley regions of the state and were associated with wetter, mesic habitats. To examine the effects of substrate and moisture on Camponotus vicinus and Camponotus modoc, I exposed inseminated queen ants to various substrates at differing humidities and exposed queens ants to a series of humidities. Camponotus vicinus intiated significantly more colonies in drier conditions than C. modoc. Camponotus vicinus also lived longer at lower humidities than C. modoc. Neither ant species could rear offspring in western redcedar. A survey of the yeasts associated with Camponotus vicinus revealed the yeast Debaryomyces polymorphus was frequently found in the buccal cavity and in colonies of these ants at two different locations. To examine the effects of exposure to this yeast on larval development in C. vicinus, I developed an artificial diet for this ant and tested this diet and variations of it on small satellite colonies of ants and larvae. Some of the artificial diets significantly affected larval development. Exposure of the small colonies and larvae to D. polymorphus showed that the yeast effected growth of some colonies fed deficient diets. Ants fed diets lacking B vitamins and cholesterol had heavier pupae and brood when exposed to live yeast than those not exposed.