At head of title: National Cooperative Highway Research Program.

Analyses on catastrophic collapse of some adjacent precast concrete box bean bridges reveal the fact that the function loss of shear keys can result in the formation of the "Single Plate Load Effect"; as a result, loads cannot transfer between adjacent beams and damage to both the structure and vehicles can be triggered on the loaded beam by heave trucks. This leads to the concern that the system safety of adjacent precast concrete beam bridges becomes insufficient when the shear keys deteriorate to a certain degree. To understand the system performance of this type of bridges, this dissertation studied the system performance of a model bridge over the full load range through an experimental investigation and finite element simulation. The results confirmed that the assumption that the robustness of certain adjacent precast concrete beam bridges may be considered safe according to the traditional safely check standards, but may not be sufficient in terms of the system safety criteria. Thus, a system factor is recommended to be applied in the safety check equation of this type of bridges. Even though some codes have already incorporated the criteria for evaluating the system behavior of highway bridges in the design and evaluating procedure, little guidance has been provided on how to determine corresponding redundancy or system factors. On the basis of the experiment findings and theoretical analysis, a simplified framework was proposed to address the particular structural feature and topology of adjacent precast concrete bean bridges, which can reduce the computation complexity compared to existing approaches for redundancy and robustness assessment. Sensitive parameters for system reliability were investigated and system reliability indices were computed using a finite element response surface method. The rationality and calibration of system factors were analyzed. In the end, the procedure for system safety and reliability assessment of adjacent precast concrete box beam bridges was applied on a bridge in service with different transverse connections and damage scenarios. The case study verified the proposed approach and outlined the procedure that can be adopted for routine bridge evaluation practice.

Precast prestressed concrete adjacent box beam bridges are widely utilized for short- and medium-span bridges throughout North America. However, a recurring issue with this bridge type is the deterioration of the shear key connection, resulting in substandard performance of the overall bridge system. This research investigated partial- and full-depth connection designs utilizing conventional non-shrink grout and ultra-high performance concrete (UHPC) by conducting full-scale structural testing. Quantitative measures to evaluate the connection performance that may assist in examining similar types of bridges are suggested in this study. A model to calculate the shear force in the connection is proposed, and both the shear and tensile stresses at the connection are analyzed. The findings can be used to assist in the design of connections for this bridge type. The performance of conventionally grouted and UHPC connections are presented and compared. It was found that the adjacent box beam bridges with UHPC connections can be a resilient bridge superstructure system, providing an innovative solution that can advance the state of the practice in bridge construction. This report corresponds to the accompanying TechBrief, Adjacent Box Beam Connections: Performance and Optimization.

Satisfactory performance of non-composite box-beam bridges depends on the effectiveness of the key way, waterproofing membrane and tie rods, and the related construction practices. Development of cracks at the longitudinal joints of such bridges is often a recurring problem that causes water leakage at the joints and corrosion of the embedded prestressing strands. The primary objective of this study was to identify the sources, causes and effects of inadequate waterproofing at the joints and to develop prevention measures. The performance of waterproofing membranes and the structural performance of key way joints with the existing and new grout materials were evaluated and correlated with field measurements recorded under traffic loading. Construction practices for new bridges, and the investigation of a bridge that was in service for 32 years at the time of its demolition were also documented. Mechanical tests on membranes revealed that they are able to accommodate at least one inch of tensile and shear deformations without losing their waterproofing properties. That kind of elongation allows membranes to bridge over any cracks that may develop at the longitudinal joints. Therefore, membrane deficiencies may not the primary cause of water leakage. Key way joints with a combination of the currently specified ODOT geometry and ODOT-approved grouts were found to be incapable of carrying any shear loads in conjunction with out-of-plane moments. From the limited site inspections done in this project, the practices followed at construction sites seem to be seriously flawed and may be largely contributing to water leakage problems in box-beam bridges. Recommendations on new key way geometries and the grouts that were developed and tested in this project are suggested for implementation.