Live-Load Performance Evaluation of Historic Covered Timber Bridges in the United States

AbstractThe National Historic Covered Bridge Preservation Program (NHCBP), sponsored by the Federal Highway Administration (FHWA), was established to preserve the covered timber bridge structures that were constructed in the early 1800s. Today, many of the approximately 880 covered timber bridges still in existence in the United States are closed to vehicular traffic; furthermore, a large percentage of the remaining bridges open to traffic are restricted by load postings. Unfortunately, there are no current load-rating standards for covered timber bridges, so engineers do not have many resources at their disposal to reliably understand the behavior of these complex structures. As a result, the estimated load postings and/or ratings are often too conservative. To better understand the live-load performance of covered timber bridges and to develop improved criteria for their load ratings, a series of live-load tests were performed on 11 single-span, historic covered timber bridges. This paper explains the f...