Institute for Transportation

About the research

Fully encasing a grouping of pier piles into one monolithic pier is more cost-effective than individually encasing each pile. Currently, the decision to fully encase rather than individually encase piles is made when there are ice or debris issues associated with the waterway in which the pier stands. The objective of this project was to calculate the capacities for monolithic encased piles with different pile lengths and encasement lengths through finite element (FE) simulations. The results of this research can be used by design and load rating engineers to calculate the capacities of concrete-encased H-piles and can be one of many resources utilized in overall bridge design and assessment. To achieve the goal, a comprehensive literature review was conducted on the design and capacity estimation of bare piles, individually encased piles, and fully encased piles. FE modeling was then performed to calculate the capacities of encased piles with different pile and encasement lengths. The results indicate that the capacities of H-piles in monolithic concrete encasement are greater than those of individually encased piles. Piles arranged with the weak axis restrained by adjacent piles and encasement achieve greater capacities than piles arranged with the strong axis restrained.

About the research

The objectives of this research were to investigate the structural behavior of the U-bolt connections on an in-service steel overhead sign truss (SOST) structure, evaluate the loading through the U-bolt connections when the SOST was subjected to various wind directions, and compare the loading experienced by the in-service U-bolt connections with the capacities predicted by a 2019 Iowa Department of Transportation (DOT) study.

To achieve these objectives, an in-service SOST structure in Iowa was selected and monitored on site for 10 months. The data collected during field monitoring were processed and analyzed. Following that, a finite element model was created utilizing the commercially available software Ansys to simulate the structural response of the SOST when subjected to wind loads. The data collected during field monitoring were used to determine the loads acting on the model and to validate the model. Further, the loads transferred through the U-bolt connections when the SOST structure was subjected to the design wind loads were calculated and compared with the U-bolt capacities predicted by a 2019 Iowa DOT study.

The yield and ultimate U-bolt capacities predicted by a 2019 Iowa DOT study were compared to the Service I and Extreme I design wind loads calculated using the AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. The comparison indicates that of all of the Type A U-bolt connections, only the U-bolt types with high yield strengths have yield capacities greater than the imposed stress. The 2019 Iowa DOT study indicated that the yield capacity of a U-bolt connection is low due to the complex geometry, and stress concentrations occur when loading is low. Conversely, the ultimate capacities are greater than the Extreme I wind loads because a U-bolt connection exhibits good ductility before reaching failure.

About the research

This study investigated alternative mixture design strategies for ultra-high performance concrete (UHPC) incorporating different types of supplementary cementitious materials (SCMs) and different types, sizes, and dosages of superabsorbent polymers (SAPs). In the first stage of this investigation, the effects of natural zeolite on the hydration development of UHPC were studied. UHPC mixtures were prepared in which silica fume, the most common SCM currently used in UHPC, was gradually replaced with natural zeolite in 25% increments. The hydration development of the mixtures was evaluated through several macroscale and microscale experiments. It was found that zeolite particles are capable of internally curing the surrounding unhydrated cement particles through water desorption over time. Furthermore, when used together, silica fume and zeolite exhibited a synergistic effect that further enhanced the degree of hydration (DOH) of the cement particles. In the second stage, the hydration development of mixtures containing different SCMs, including silica fume, silica fume and zeolite, zeolite, and limestone, were compared with those of a control mixture. A similar experimental program to that pursued in the first stage was completed. In the third stage, an alternative approach to increasing the hydration of cement particles in UHPC using SAPs was evaluated through the preparation of multiple mixtures with various SAP types, sizes, and dosages. Employing a holistic testing matrix, it was observed that the introduction of SAPs to the UHPC mixtures increased the DOH of the cement particles and improved the dimensional stability of the developed mixtures. The results of this study provided a fundamental understanding of the behavior of each SCM and SAP type in UHPC individually and in combination with each other. The outcomes can be employed to select the most appropriate SCMs and SAPs based on a given project’s needs and target applications.

About the research

This project investigated helical pile foundation implementation for bridges, resulting in a design and construction guide. The simplicity and speed of helical pile installation, along with the ability to work within areas of limited size with smaller, more maneuverable equipment, can accelerate the construction of bridge structure foundations.

The guide provides bridge engineers and designers with direction and specifications for this substructure foundation option, which can be advantageous on any bridge project, but particularly for low-volume roads where budgetary considerations tend to be a specific priority.

The guide includes many useful design specification reference tables and also useful construction and installation documentation tools as examples and as table forms that can be used for helical pile bridge foundations.

About the research

Accelerated bridge construction (ABC) is widely used by departments of transportation (DOTs) because of the reductions in 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.

A common ABC technique is the use of prefabricated bridge elements and systems (PBES). Bridge components are built outside of the construction area, transported to the 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. Damage due to weather is also 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 bridges. However, there is a gap in the literature regarding how to address the long-term performance and durability concerns associated with the joints that connect high-quality bridge elements. One approach that has gained significant attention is to eliminate these 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 undertaken.

To address this issue, this 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 is design guidelines and practical recommendations for properly implementing a link slab in jointless bridges constructed using ABC and conventional techniques.

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