About the research
The main objective of this research was to investigate the efficacy of the use of helical pile foundations for accelerated bridge construction (ABC) projects. The focus of the research was helical pile use to accelerate foundation construction on bridge projects.
The capacity of helical piles is on par with several other deep foundation technologies. Installers tout the simplicity and speed of installation, along with the ability to work within areas of limited size with smaller equipment. The required equipment for installation (skid steer, backhoe, or excavator) lends itself to quick deployment and being an economical solution (i.e., excavator vs. crane), an advantage for any bridge project, but particularly for low–volume roads where budgetary considerations tend to be a specific priority.
This report includes details on the current state–of–the–practice for helical piles, the potential adoption of helical piles for ABC projects, other key project considerations, and recommendations for further study/research.
This report includes a literature review, contractor/installer questions and answers, a cost comparison, and images from a helical
pile installation demonstration. It also provides a decision making framework, which includes two tools: a process flowchart of
questions and answers and a table matrix of questions and considerations categorized by site and constructability, geotechnical, and design. The References section includes a list of webinar resources at the end of it
About the research
Lateral slide–in bridge construction (SIBC) has gained increasing attention as a viable accelerated bridge construction (ABC) approach. With lateral slide construction, the majority of the bridge superstructure is constructed off alignment, typically parallel to the final position, and usually on a system of temporary works.
While many state departments of transportation (DOTs) have completed lateral slide construction of single–span bridges and have common connection details already established, these details do not directly apply to multi–span slides. The addition of more spans creates a more complex system that require connections (and other details) that were previously not needed in a single–span slide. In addition, the fact that the multi–span bridge needs to slide on abutments plus piers (as opposed to just abutments) creates possible uplift and overturning scenarios.
A comprehensive literature search was conducted to find relevant information on the implementation of SIBC on multi–span bridges. However, limited public information was found that directly related to the substructure behavior subject to the lateral slide load. An analytical simulation was conducted to investigate the structural behavior of the bridge piers during the bridge slide–in and to evaluate the drawbacks and advantages of two– and four–point pushing.
A finite element (FE) model was developed and validated against the data collected from a field monitored bridge. The results indicated that two–point pushing increases the loading on the pier diaphragm by 36%. Because of this, the pier response with respect to the tilt about the x and z directions increased; however, this increase was not significant. By analyzing the field and analytical solution results, it was also found that the bridge pier experienced a greater rotation about the bridge transverse direction than about the longitudinal direction.
The results of the FE modeling and the literature search resulted in unanswered questions that would benefit from further study. A detailed research plan including a series of laboratory tests is presented in the Phase I report.
About the research
Accelerated bridge construction (ABC) techniques are rapidly gaining acceptance as an alternative to conventional construction to reduce construction duration and minimize the impact of closures at the network level. There are different types of ABC and each technique has its limitations and speed of completion. The choice of using a specific ABC depends on a host of different factors including its applicability to specific bridge site, criticality of the bridge to the network, and availability of capital funds for its implementation. Some of these factors tend to have contradicting affects, as a faster ABC technique often entails higher investment levels; on the other hand, a faster technique for a bridge with high criticality to the network may result in large savings in user costs.
This report details the development of a mixed-integer programming model that provides a balanced portfolio of construction techniques on bridge sites over a prioritization process for bridges at the network level. For this purpose, while a network-level scheme is used to select the bridges for rapid replacement based on their criticalities to the network, a project-level scheme accordingly is conducted to optimize the choice of accelerated construction techniques. To account for the effects of different accelerated construction techniques, the costs associated with each replacement technique is calculated including direct costs from the actual replacement of bridges and indirect costs experienced by network users due to the bridge closure during the maintenance period.
Using the mixed-integer programming model, based on the investment budget, the new service performances of bridges, and the optimal accelerated construction techniques for different bridges, the bridge replacement strategy and the costs during the entire process are estimated, which could provide the decision-makers and stakeholders a detailed understanding of the prioritization process at both the network and project level.
About the research
Accelerated bridge construction (ABC) is now being widely used by departments of transportation because of the reductions of traffic disruption, social cost, environmental impact, and lost time. ABC is also known to improve work zone safety, on-site constructability, and project completion time. One of the common techniques in ABC is using prefabricated bridge elements and systems (PBES). The bridge components are built outside of the construction area, transported on site, and then rapidly installed. Time lost due to concrete placement, curing in the construction zone, and formwork erection/removal is reduced. Another benefit to using prefabricated structural elements is improved quality control. Damaging effects due to weather are minimized because elements are built in a controlled environment. Considering the advantages of PBES, a number of research projects have been conducted on the prefabrication and installation of the main structural elements of the bridges.
However, there is a gap in the literature on how the long-term performance and durability concerns associated with the joints that connect already high-quality bridge elements may be addressed. One approach that has gained significant attention is to eliminate the joints through revised design strategies. While such strategies have been successfully developed for integral abutments used for ABC applications, no systematic study on removing the expansion joints between bridge girders has been found. To address this issue, the current research project investigated the use of a flexible link slab through a comprehensive set of experimental tests and numerical simulations. The outcome of this project was to provide the design guidelines and practical recommendations necessary to properly implement a link slab in the jointless bridges constructed with ABC and conventional techniques.
About the research
Accelerated bridge construction (ABC) is a solution for upgrading substandard bridges that reduces construction and closure times and minimizes exposure of the traveling public and road workers to construction activities. To take full advantage of the benefits of ABC, agencies should decide which projects are appropriate for ABC, how to bid these projects given the unique attributes of ABC methods, and which procurement and project delivery methods to use.
The research team compiled information on decision matrices for identifying ABC projects, alternative delivery methods, and the procurement methods used for ABC projects, outlining bidding processes for projects that utilized ABC. Four ABC projects in three states (Georgia, Indiana, and Minnesota) were then investigated in detail. The research team reached out to personnel involved in the projects to discuss bid items, contracting methods, and lessons learned. The results of this effort are included in two separate reports and also in four standalone case study summaries.
The case studies suggest that ABC can be successfully implemented using any of the delivery methods explored in this study: design-build, design-bid-build, or construction manager/general contractor. Regardless of the project delivery method, communication and collaboration between the contractor and agency result in a better project outcome. Effective communication with the public is also important during ABC projects and can be done by either the agency or the contractor. When bids allow for flexibility, innovation is often incorporated into the project, which results in financial savings for the agency and/or time savings for the traveling public. After a project is completed, the agency can benefit from reviewing the lessons learned and successful aspects of the project and applying these to future projects.
About the research
Bridge deck expansion joints allow for the movement of bridge decks exposed to thermal expansion and dynamic loading. These joints are often one of the first components of a bridge deck to fail, and there is a need for accelerated replacement options, especially in areas with high traffic volumes. Extensive research is being conducted on accelerated bridge construction (ABC) initiatives to reduce lane closure time. However, less attention has been devoted to accelerated repair and replacement of bridge deck expansion joints.
This project developed methods for the accelerated replacement of bridge deck expansion joints, beginning with a literature review. The combination of a stainless steel railing and ultra-high-performance concrete (UHPC) header with hydrodemolition was evaluated for its effectiveness as an accelerated option.
A life-cycle cost analysis with a sensitivity study compared the proposed replacement to current practices and two alternative methods. This analysis revealed that,for bridges with a life of greater than 50 years, the proposed replacement was the most cost-effective option.
The proposed replacement joint also underwent bonding, static, and fatigue testing. Hydrodemolition was also used in the replacement process of the testing. These tests indicated that the joint system utilizing hydrodemolition produces an excellent bond with the existing concrete. The static and fatigue testing revealed the joint system meets department of transportation (DOT)standards and would likely have a long service life.
About the research
Accelerated bridge construction (ABC) is the solution of choice to upgrade substandard bridges or construct new bridges while maintaining traffic flow and optimizing safety through work zones. However, the perception of higher construction costs for ABC versus conventional construction continues in spite of numerous ABC projects having lower construction costs compared to conventional construction. This inaccurate perception and the fear of cost overruns are causing some bridge owners to be reluctant to implement ABC technologies, especially those technologies related to bridge system moves, which can provide the greatest benefits for safety and traffic flow.
While the traditional contracting method for state departments of transportation (DOTs) is primarily unit price contracting, there are alternatives, including cost plus, lump sum, lump sum with a guaranteed maximum price, and progressive lump sum with a guaranteed maximum price. To date, there has been little investigation into the use of these alternative contracting methods for ABC projects. This project explored the use of these options to understand the state of practice regarding contracting methods and provide insights and lessons learned for DOTs.
About the research
Ultra-high performance concrete (UHPC) provides superior properties in strength and durability for the long-term performance of bridges. Despite these desirable properties and the potential to be applicable in the majority of projects, UHPC is still not widely used, mainly because of the cost associated with it.
This report details a study performed on the design of non-proprietary UHPC mixes that provide comparable strength properties to that of commercially available mixtures. A set of base mixtures were explored by varying the ratios for various constituents and investigating their durability, strength, and transport properties, including volume stability and freeze-thaw resistance.
In the later stage of the project, the selected non-proprietary mixes were evaluated for their flexural strength. The flexural strength in UHPC comes mainly from the fibers used in the mix. Bearing in mind the role of fibers, the effects of various types of steel fibers (i.e., variation in shape, size, and dosage) were evaluated. The role of fibers on strength and post-cracking behavior was carefully examined using laboratory testing and image analysis utilizing digital image correlation techniques. The efforts found that an optimal combination of micro- and macrofibers can enhance the flexural strength of UHPC mixtures.
Steel fibers contribute to more than a third of the cost of UHPC mixtures, so the possibility of utilizing less expensive and more environmentally friendly synthetic fibers—polypropylene, polyvinyl alcohol, nylon, alkali resistant glass, or carbon—to partially replace the steel fibers could reduce the cost of UHPC. The steel fibers were partially replaced by the different synthetic fibers to see their effect on the UHPC’s fresh properties and flexural strength. Utilizing digital image correlation, the synthetic fiber contribution to post-cracking behavior was evaluated, especially from the crack width control and crack propagation aspects. The replacement of steel fibers with synthetic fibers showed promise for flexural strength and post-cracking behavior.
This report provides recommendations for the preparation of cost-effective, non-proprietary UHPC mixtures that could be used for various transportation infrastructure applications. Further recommendations are also made for the optimal combination of different types of steel micro- and macrofibers to get the best flexural response. Recommendations are then extended for the use of different types of synthetic fibers and the optimum percentage of dosage replacement for steel fibers.
About the research
Accelerated bridge construction (ABC) has been implemented with greater frequency over the last decade, with successful projects geographically spread across the country. As these initial deployments of ABC methods age, it becomes necessary to inspect the structures for both maintenance decision making and for assurance of adequate service life performance. This data collection in the form of detailed inspection information allows for active management of the infrastructure and assessment of performance via key metrics. As such, it would be useful to broadly assess the performance of past ABC projects across the nation using consistent and effective inspection methods and metrics. This effort is further strengthened by the national presence of the ABC-UTC partner universities who are collaborating on this project.
About the research
Many transportation organizations have embraced Accelerated Bridge Construction (ABC) to reduce both the traffic impacts and societal costs. One of the most common means to achieve ABC is to utilize prefabricated elements that are connected on site to construct a bridge. ABC will not be effective if the barrier requires cast-in-place construction. The purpose of this report is to present details of a precast barrier and two connection alternatives between the deck and precast barriers. In addition, a new connection between two adjacent prefabricated barriers was presented. All three connections were tested using full-scale precast barriers and a video summarizing the test can be found at https://youtu.be/up6sMEeqfaU.
One barrier-to-deck connection used inclined reinforcing bars with threaded ends that were connected to bar splicers embedded in the bridge deck. The other barrier-to-deck connection used U-shaped bars that were inserted into the barrier from the underside of the bridge deck overhang. Factors that were considered when designing the connections were minimal damage to deck, easy replacement of barrier, constructability, durability, and cost.
The barrier-to-barrier connection utilized headed reinforcement in the longitudinal and transverse directions. The connections were designed to meet TL-4 loads as per the Manual for Assessing Safety Hardware (MASH) and Load and Resistance Factor Design (LRFD) Bridge Design Specifications.
This report presents results from various tests and shows that all proposed connections are viable for accelerated construction of concrete barriers, although some refinement to the tested details will be needed.