Staged Concrete Bridge Deck & Overlay Pours Adjacent to Live Traffic

Bridge decks, particularly those in regions where the concrete is subjected to severe environmental conditions such as freeze‐thaw cycles and deicing chemicals, are prone to substantial degradation over time, evidenced by extensive concrete cracking and spalling, corrosion of reinforcement and damage to bridge joints, among others. It is therefore expected that bridge decks will be subjected to repairs, rehabilitation and even replacement during the lifetime of the bridge, which may severely impact traffic operations across the bridge. The need to minimize the impact of bridge deck repairs on traffic operations has led to the use of staged construction, where part of the existing bridge deck is left operational such that traffic can be maintained while the remaining part of the bridge deck is repaired or replaced. Often, full‐depth staged deck construction involves the use of precast deck panels (Oliva et al., 2007) such that cast‐in‐place concrete or grout is only required in the “gaps” or closure pours between the panels. By maintaining part of the bridge open to traffic, temporary structures or road detours may be eliminated, leading to substantial savings and minimizing impact on traffic. A similar challenge is faced in construction of new bridges and widening of existing ones. For new bridges, there is need to open the bridge (or at least part of it) to traffic as early as possible. When widening existing bridges, on the other hand, construction methods that allow traffic operations to continue are highly desirable, as in the case of repairs/replacement of existing decks. During staged construction, one side of the bridge is subjected to traffic (live loads) and dead loads, while the other side is only subjected to dead load. For new decks or full‐depth replacement of existing ones, the presence of live load on one side of the bridge while concrete is cast on the other side not only generates vibrations on the curing concrete, but also relative vertical movement between the longitudinal joint and the adjacent bridge girder on the side being constructed, or between the two edges of closure pours. The effect of these traffic‐induced vibrations and relative deflections on early-age and long‐term performance of longitudinal joints (or closure pours) in staged decks has thus been the subject of research in the past few decades. For bridge deck overlays, on the other hand, the primary concern has been on potential degradation of bond between the existing concrete and the overlay caused by adjacent traffic. As bridges in Wisconsin are subjected to harsh environments and deicing chemicals, minimizing cracking and spalling in the longitudinal joint regions, as well as damage caused by overlay debonding, is of utmost importance to prevent any detrimental effect of staged construction on durability of the bridge deck. The primary objectives of the proposed research are to: (1) evaluate the current state of bridge decks and overlays in the State of Wisconsin that were either constructed or repaired following a staged construction process; (2) evaluate the performance of various longitudinal joint designs applicable to bridge decks constructed in stages; (3) evaluate bond strength between existing decks and concrete overlays placed while being subjected to traffic‐induced vibrations; and (4) develop recommendations for the design and construction of staged concrete bridge decks and overlays. The proposed research activities are expected to lead to the following products: (1) A report summarizing the condition of selected existing bridge decks and overlays constructed in stages. (2) A detailed report on the behavior of different longitudinal joints and overlay designs subjected to simulated traffic‐induced vibrations based on the results from the numerical analyses, field studies and experimental program. (3) A set of recommendations for implementation in the design and construction of staged bridge decks and overlays in order to minimize the effect of traffic‐induced vibrations and increase the service life of the bridge deck. The design and construction recommendations will be prepared in the form of a “field manual”, in consultation with the Project Oversight Committee, such that it can be implemented immediately upon completion of the project. The main target audience for this manual will be WisDOT engineers, as well as bridge engineers and contractors in the State of Wisconsin and other states subjected to climate similar to that of Wisconsin.