Highway flyover bridges in New Jersey experienced extensive early-age cracking on the high performance concrete deck recently. There were transverse cracks observed predominantly in the positive moment regions and spider cracks concentrated in the negative moment region over the box beam. A typical two-span curved continuous bridge with high performance concrete (HPC) deck, steel girders and integral box-beam was selected to identify factors that affect early-age HPC deck cracking so as to mitigate the cracking issues on existing concrete continuous bridges. Extensive field tests were performed and various structural responses were collected for model calibration and structural analysis. Cracking issues due to effects of vertical temperature differentials, staging, shrinkage, settlement, tilt of piers, dead load, live load, etc., were quantitatively investigated and summarized through parametric study. Of prime interest has been the identification of the contributions of various effects on deck cr...

Bridge approach slabs are designed to function as a transitional roadway to the bridge deck, spanning the distance between the abutment and the road pavement. However, the number of rough riding approaches with heavy maintenance requirements is sufficient to convince highway agencies that a serious problem exists. The complaints usually describe a ‘bump’ that motorists feel when they approach or leave bridges. This bump results in reduction of steering response, distraction to the driver, amplified truck impact and dynamic response in bridge decks, and expense to maintenance operations. Approach slabs can lose their contact supports due to various reasons, including the settlement of soil and the bulging of embankments. The objective of this paper is to present results from a study to evaluate the analytical behaviour and the field performance of new design alternatives that could reduce or eliminate this problem. The new designs were analysed using comprehensive finite element (FE) models and were also built and instrumented at the Doremus Avenue Bridge in Newark, New Jersey, for testing and long-term monitoring. Various truck load tests were performed prior to opening the bridge to traffic. The results show that the FE models are accurate and that the new design alternatives have higher load carrying capacities than those of the existing design. In addition, results also show that long-term field monitoring using various sensors can lead to quantitative measurements of various factors that can lead to the cracking of the approach slabs.

The “S-over” Load Distribution Factor (LDF) has been used for many years for determining the distributed moments and shear forces of a girder. Only until recently after the adaptation of the AASHTO LRFD Bridge Design Specification, new LDF equations are proposed using power functions. Although these new equations can more accurately predict the distributed moments and shear forces similar to both field and finite element analysis results, they are complex and they do not represent the fundamental background of LDF but rather based on regression analysis. Therefore, a more fundamental equation such as the S-over LDF is needed for the engineer to have a better understanding of the relationship between the girder sizes and spacing. The primary objective of this study is to develop a simplified S-over LDF for shear for steel and prestressed concrete I-girder bridges. Actual field testing of seven I-girder bridges were evaluated and validated to the developed Finite Element Analysis (FEA) model. A parametric study of bridges with various girder spacing and length were performed to develop the proposed equations. Results show that the proposed equations have excellent correlation with the more exact FEA model as well as the computer-based analysis.

Cracking in concrete deck has been the major concern to bridge designers as well as owners. Excessive cracking not only would affect the performance and serviceability of the bridge but also reduce the service life of the concrete deck and increase the maintenance cost. It is proven that many factors could cause the cracking of concrete deck including restrained shrinkage, temperature effects, applied live load, and improper construction sequence. Among these factors, appropriate construction staging plays an important role in minimizing the cracking of concrete deck, especially for multiple span continuous bridges. However, the construction staging has not been subjected to detailed research in the past. Therefore, it is important to evaluate the current concrete deck construction staging practice and propose an optimized construction staging for multiple span continuous bridges, if needed. In this study, the research approach adopted is aimed at investigating the cracking of a typical multiple-span continuous bridge, evaluating the construction staging, and providing an optimized practice for deck construction staging. A typical three-span continuous bridge was selected for investigation and various types of sensors were instrumented on the bridge to monitor the behavior of the structure during and after construction. The finite-element (FE) model was developed and validated with the data collected from field testing. Based on FE analysis and experimental data, the cracking of the bridge deck was investigated and alternative construction staging scenarios were simulated and compared. Moreover, based on analysis results, an optimized deck construction staging practice was recommended for future use.

Modeling the traffic loads on bridges has been the subject of numerous studies. Defining a live load model to be used for bridge design is not an easy task. It demands among many other things a reliable dataset, a well-defined procedure for filtering data and also the determination of statistics for single and multiple presence occurrences. This study examines and characterizes the live load statistics for Brazilian concrete bridges. Single and multiple truck presence are evaluated for different bridge spans and truck daily volume. The sample is comprised of the thirteen months of data from a High Speed Weigh-In-Motion station (HS-WIM) in a resolution of one hundredth of a second currently operating on the Fernão Dias highway, also known as BR-381. The system provides eleven thousand records on a daily basis. After the filtering process three thousand trucks remain. The station takes measures in an same-direction two-lane highway, which allows the evaluation and characterization of both single and multiple presence statistics. Three case of multiple presence are considered: following, side-by-side and staggered cases. The consideration of truck multiple presence on concrete bridges is mandatory to understand and characterize live load models. The results show that with the exception of the side-by-side case, the frequency of multiple truck presence is significantly affected by span length. It also shows that the daily truck volume considerably affects the multiple presence statistics for all load patterns. The results show that the general tendency of the occurrence of all multiple presence events is to increase as the truck volume increases.

Transit agencies own and operate thousands of bridge structures subjected to repetitive train loading. The majority of these bridges were built at the turn of the century and many have exceeded their theoretical fatigue life spans. In New Jersey, the recent increase of the railcar weight limit from 1,170 kN (263,000 lb) to 1,272 kN (286,000 lb) raised concerns for railway bridges that have been in service for more than a century. To prioritize and schedule repairs and rehabilitation events, there is a need to establish refined procedures that would be able to estimate the impact of the increased railcar weight on the remaining life and damage accumulation of bridges. In this paper, three typical railway bridges with various span lengths were selected. Field testing was performed to validate the three-dimensional (3D) finite-element (FE) models of the bridges. A probabilistic approach was developed for fatigue evaluation. For fatigue resistance, a new model was proposed based on previous full-scale fatigue tests. The variance of fatigue resistance increases when the stress range increases based on test results. The new 1,272-kN freight car and its frequency are found to have a significant effect near the supports in terms of remaining fatigue life. Midspan location would not always be the most critical location of the bridge when operating the heavier railcars. An increase of 1,000 freight trains annually will decrease the remaining fatigue life by approximately 2 years. Last, the introduction of heavier railcars will have more significant effects on shorter spans.