Book Description

Bridges that are designated historic present a special challenge to bridge engineers whenever rehabilitation work or improvements are made to the bridges. Federal and state laws protect historically significant bridges, and railings on these bridges can be subject to protection because of the role they play in aesthetics. Unfortunately, original railings on historic bridges do not typically meet current crash-test requirements and typically do not meet current standards for railing height and size of permitted openings. The primary objective of this study is to develop strategies that can be used to address existing railings on historic bridges and to develop solutions that meet current design requirements. In addition to the modification, selection, and design of the bridge railing, the bridge deck is also impacted by changes made to the railing. Due to increased force levels recently required by AASHTO, deck overhangs require significantly more reinforcement than for past practice. These increases are being realized on all bridge decks and may pose particular challenges for the attachment of railing to historic bridges. Therefore, a secondary objective of this project is to investigate the design of the deck overhang and determine whether reduced amounts of reinforcement are possible. For Volume 1 (Replacement Strategies), three phases of research were conducted. First, an overview of current practice for addressing historic bridge railings was performed. Second, an investigation was conducted to document historic bridge railings in Indiana. Finally, rehabilitation solutions were developed to address the specific bridge railings found in Indiana. Based on this research, three retrofit strategies were developed which include an inboard railing, curb railing, and a simulated historic railing. These rehabilitation solutions can be used to address historic bridge railings not only in Indiana, but across the country. For Volume 2 (Bridge Deck Overhang Design), experimental testing of half-scale and full-scale overhang specimens was conducted, and the results were analyzed. Failures of in-service bridge railings were also evaluated. Based on this research, recommendations are provided for the more efficient and economic design of bridge deck overhangs. These recommendations are applicable not only for historic bridges, but for all concrete bridge decks.