A hierarchical analysis of factors affecting the adoption and marketing of timber bridges

Several aspects influencing the adoption of timber bridges were investigated. Initially, perceptions of timber as a bridge material were rated by highway officials in twenty-eight states. Timber was rated lowest in overall performance by each group (State Department of Transportation engineers, private consultants, and local highway officials) throughout the United States. The highest rated bridge material was prestressed concrete, followed by reinforced concrete, steel and timber. The most important factors in the bridge material decision included: Lifespan of material, past performance of material, maintenance requirements of material, resistance to natural deterioration, initial cost, and lifecycle cost. Timber was compared to other bridge materials on eight preselected attributes. Timber rated the lowest on the attributes of low maintenance, ease of design, long life, and high strength.

Highway officials in four states (Mississippi, Virginia, Washington, and Wisconsin) were personally interviewed. The Analytic Hierarchy Process (AHP) was used to characterize their decision of a bridge material. The most important bridge criteria were similar in each state, however, their effect on the overall decision differed by state. Prestressed and reinforced concrete were the materials of choice in all states. The results of this study indicate that, based on the six criteria measured, timber will seldom be the material of choice for highway bridges.

Timber bridge manufacturers were surveyed to understand current marketing and management techniques in the promotion of timber bridges. Marketing efforts were most prevalent in the Midwest. Timber bridge sales represented, on average, less than 7% of total sales from responding companies. Wood treating and gluelaminating firms represented over 75% of the timber bridge firms. One-half of the responding timber bridge companies felt that timber bridge sales would increase an average of 15% over the next five years.

Barriers and incentives to timber bridge adoption were investigated. The greatest incentives include: year around construction, resistance to deicing chemicals, quick construction, and aesthetic qualities. Major barriers appear to be: short lifespan, maintenance requirements, decay, perceptions of strength, and that "timber doesn't perform well under high weight and traffic volumes". The realistic size of the bridge market was estimated not to exceed 600 to 700 designed bridges a year. This would require the use of 10 to 12 million board feet of lumber.