ABC Closure Joints: Detailing, Design and Service Life

Accelerated Bridge Construction (ABC) is a paradigm change in delivering bridges, which significantly minimizes onsite construction, enhances the safety of the public and construction workers, and uses innovative materials and technologies that can increase the service life of bridges. The most widely used ABC technique utilizes prefabricated modular bridge deck elements; however, there are concerns regarding the structural performance and durability of cast-in-place joints between these elements. Because of the limited experimental data on closure joints, there is a lack of information helpful for detailing, design and service life of these joints. To address these concerns, research was conducted to develop a comprehensive design specification for closure joints in ABC projects. As part of this initiative, a new detail is proposed to connect the adjacent prefabricated modular deck elements in the closure joint region. The new detail consists of a 90° hooked bar in the closure joint using normal strength concrete. The primary goal of this research is to develop design provisions that could be adopted by governing design and construction specifications. This goal is achieved through non-destructive testing, experimental, and numerical programs focused on these joints. The performance of existing closure joints was also evaluated using nondestructive testing methods. Impulse response testing was identified as an effective method to evaluate joint defects and testing was carried out on in-service bridges and laboratory specimen. The performance of the closure joints was evaluated in terms of mobility. To evaluate the structural performance of the new detail, specimens with different bar sizes and lap splice lengths were tested under flexural loading. The ductility ratio was used to assess the performance of different hooked bar details. It is concluded that a ductility ratio between 3 to 4 can be used as a metric for joint performance. Based on the outcomes of the experimental study, design recommendations are provided for different rebar sizes. A detailed finite element (FE) analysis was carried out to complement the results of experimental study and a parametric study was performed to understand behavior of the joint. The results show that these longitudinal connections detailed with hooked bars can be a viable alternative for the design and construction of closure joints. Closure joint construction can be costly in ABC projects, which can offset the advantages of modular construction. The simplicity of the proposed new detail provides a cost-effective alternative to expensive details which use headed bars or Ultra-High Performance Concrete. The detail is not proprietary; it uses normal strength concrete and is economical