Ultra-high-performance concrete (UHPC) is an excellent material for bridge construction due to its superior workability, durability, and mechanical properties. This paper presents the development of an innovative UHPC superstructure system for medium- and long-span bridges. The new system consists of decked I-beams (DIBs) designed to optimize superstructure weight, speed of construction, structural efficiency, and durability. A nonproprietary UHPC mixture was developed, and a special form was manufactured to produce DIBs with ribbed slabs. Several material/structural tests were conducted on small-scale specimens and two full-scale specimens to evaluate flexural strength and punching shear strength of the ribbed deck slab as well as load distribution in the DIB flanges. The challenges associated with the production of two full-scale specimens using the new nonproprietary UHPC mixture and DIB forms are discussed. Test results indicated the adequacy of the developed system when compared to the demand of an example bridge and the predicted capacity according to AASHTO UHPC Guide Specifications and PCI Design Guide.

The paper presents the development of a new UHPC Decked I-Beam (DIB) superstructure system for bridges in Nebraska and discusses its design, production, and testing. The UHPC DIB was developed to achieve maximum deck durability, speed of construction, and structural efficiency. Special formwork was designed and manufactured to fabricate the developed system for both pretensioned and post-tensioned bridges, with options for using either minimized weight ribbed slab or simplified precasting solid slab top flange option. Two 20 ft long, 4.5 ft deep, and 9 ft wide full-scale specimens were manufactured by the two precast bridge producers in Nebraska using a UHPC mix design developed in an earlier project for NDOT using locally sourced materials: a) pretensioned specimen with ribbed slab; and b) post-tensioned specimen with solid slab. The solid slab top flange specimen was produced for the purpose of comparing behavior of the two geometries. Several material/structural tests were conducted on the two specimens to evaluate UHPC mechanical properties, shear strength without transverse reinforcement, wheel load transverse distribution in the DIB flanges, and anchorage zone reinforcement of the post-tensioned option. Test results indicated the adequacy of the developed system capacities when compared to the demand of 100 ft long simply supported bridge and predictions of the latest UHPC design guidelines. Lessons learned from the production of the two specimens are also discussed.

As a follow up to the paper on the design of the UHPC decked I beam (DIB) presented at the second international interactive UHPC symposium, the current paper will look at the DIB fabrication and testing. Due to lack of UHPC structural design codes, there is a need to perform experimental structural evaluation of these precast structural elements, including small scale specimens and full scale 15-m beam. The experimental findings and comparisons with design codes will be presented

The state of Nebraska has begun an ambitious initiative to develop a standardized bridge superstructure system utilizing ultra-high-performance concrete in the precast concrete beams and in the cast-in-place closure pours between beams and over the supports. The initiative was motivated by recently made available structural design guidelines by the Federal Highway Administration (FHWA) and by the Precast Prestressed Concrete Institute (PCI), which followed over 25 years of intensive materials research and non-structural applications. Research has demonstrated that UHPC can be produced in available precasting facilities and can result in outstanding tensile properties due to use of steel fibers, and excellent durability due to the application of particle packing theory. Nebraska is in an environment of extreme temperatures during the year. Deicing chemicals and freeze-thaw cycles cause deck cracking which requires significant maintenance work. In addition, urban areas require rapid construction to minimize traffic disruption. The newly developed UHPC NUDIB (Nebraska University Decked I Beam) was designed to meet both the requirements of accelerated bridge construction (ABC) and deck durability. Further, due to the relatively high unit cost of the UHPC mix, effort was made to minimize the volume of concrete used without sacrificing stiffness. The result is an I beam shape that has a top flange whose width is nearly equal to the beam spacing. The gap between beams is only 8 inches and is filled with CIP UHPC. The web width is standardized at 4 in. The bottom flange is designed to be suitable for both segmental post-tensioning and full-length pretensioning. The top flange has a 2.5 in. skin and a total depth of 8 in., with the 5.5 in. difference occupied by thin ribs spaced at 24 in. The family of sizes has three depths: 54, 72, and 90 in. and variable flange width from 72 to 136 in. The expected spans range up to 200 feet. This paper explains the evolution of the cross-section shape. It details an innovative forming system for this relatively complex cross section shape. It provides a span chart and explains the various challenges faced and how they were resolved.

Horizontally curved bridges have been mostly built with steel plate I-girders or tub girders. In the past 15 years, curved concrete girders have been successfully used in several states, including Nebraska, Colorado, and Flor­ida. This paper addresses the design of curved concrete girder bridges using ultra-high-performance concrete (UHPC) by combining state-of-the-art spliced girder technology and UHPC technology. It also proposes a number of unique features that result in further simplifi­cation of precast concrete production and construction. Critical design criteria are discussed. The system devel­opment of curved UHPC girder bridges and necessary construction steps are elaborated through a numerical example of a three-span bridge, which shows greatly reduced concrete quantities when compared with re­cently constructed curved concrete girders. With UHPC designed as proposed here, horizontally curved bridges are expected to be cost competitive with conventional concrete and more economical than structural steel.

■ PCI has devoted resources to study ways to meet UHPC implementation challenges, which include cost and the development of UHPC structural systems to capitalize on its unique capabilities. Ultra-high-performance concrete (UHPC) was first introduced as reactive powder concrete in the early 1990s by employees of the French contractor Bouygues. Since then, France, Japan, Malaysia, South Korea, and several other countries have made significant progress in using this material for bridge construction and other applications. The first roadway bridge with UHPC beams was built in France in 2001 and comprised five double tees with a beam section referred to as a pi shape.

This paper presents the development and experimental investigation of a new full depth precast concrete deck system that was developed within the NCHRP Project 12-96 as a simplified system for accelerated bridge construction. The system has the following features: shear connectors are located at the transverse joints only that are spaced up to 6 ft (1.8 m) in the longitudinal direction; transverse joints and shear connections are filled with UHPC that enables full composite behavior between the deck and the supporting girders; deck panels can be made solid or ribbed if deck weight reduction is desirable; and unique clustered shear connector assembly is used to resist large interface shear forces. The paper focuses on the role of using UHPC in achieving the goals of the new system and allowing the extension of the maximum spacing of shear connectors from 4 ft(1.2 m), currently specified by AASHTO LRFD Bridge Design Specifications, to 6 ft(1.8 m). This extension increases the interface shear demand and stress concentration at the joints by 50%, which necessitates the use of a grouting material with superior mechanical and durability properties, like UHPC.

Precast/prestressed concrete is commonly used in short and medium span bridge construction because its assured quality, inherent durability, and optimized use of materials satisfy the needs of bridge owners. Recent research projects conducted at the University of Nebraska – Lincoln (UNL) focused on using high performance materials in precast/prestressed concrete bridge girders and deck panels that significantly improve their durability, economics, and speed of construction. This paper discusses the use of High Strength Self-Consolidated Concrete (HSSCC), 18 mm diameter prestressing strands, and Grade 550 high strength welded-wire reinforcement (WWR) to achieve simplicity of production and erection and maximize span-to-depth ratio while being economical. Precast/prestressed concrete girders with span-to-depth ratio of over 30 were developed and tested. The main advantages of these girder are the ease of production, speed of construction, and enhanced durability. A summary of specimen design, production, and tested is presented.

The use of shallow floor systems in office buildings is desirable because it reduces the overall building height and saves on the cost of architectural, mechanical, and electrical building systems. Precast, prestressed concrete floors consisting of hollow-core slabs on inverted-tee beams are known !Or their superior quality and speed of construction. However, when the depth of the hOllow-core slab, inverted-tee beam ledge, and column corbel are added, the total floor depth becomes significantly larger than that of cast-in-place, post-tensioned slabs. This paper presents a system by which the hollow-core slabs are framed next to the beam rather than on top of a ledge, and the beams are framed into the column without the aid of a permanent concrete corbel. For the development of the system, a 30 by 30 ft (9.1 by 9.1 m) bay size is considered typical for office floors. Hollow-core slabs that are 8 in. (203 mm) deep are supported on 10 in. (254 mm) deep beams using a new beam-hollow-core connection that is designed using shear-friction theory. Methods of temporary support until the composite topping is cured are presented. Full-scale testing continued satisfactory performance. A beam-column connection is also developed using column recesses at the beam location and reinforcing bars through a void in the column to allow the beam to be continuous and its reaction to be resisted by the column without the conventional corbel. A temporary , steel angle support is used until the connection grout is hardened. Full-scale testing of the beam-column connection showed excellent behavior. 'l'he main advantages of this shallow floor system are its high span-to-depth ratio (up to 30) and its efficient and economical production and erection techniques. Some of the features of the developed system were implemented in a four-story office building in Lincoln, Neb. Experience with this application is also discussed.

The structural engineering firm, e.construct (Omaha, Nebraska, United States), has designed an Ultra-High Performance Concrete (UHPC) decked I-beam to be installed at a new privately-owned vehicular bridge in Shanty Bay, Ontario, Canada for demonstration and evaluation. Through a technology transfer joint venture agreement between FACCA Incorporated (Ruscom, Ontario, Canada) and Dura Technology (Ipoh, Malaysia), the Dura UHPC is batched using local North American raw materials. This paper will focus on development of the UHPC decked I-beam and adjustments that have come about during the on-going implementation process for this Design-Build project. The paper will also list items needing further investigation. One of the biggest challenges faced thus far has been the creation of formwork that will allow for the top flange waffle deck to be cast simultaneously with the rest of the beam without creation of any cold joints. Economy in utilizing the relatively expensive UHPC and desire to reduce the number of ribs in the top flange resulted in an optimized spacing of 500 mm (20 in.). To keep the rib width to a minimum, high strength corrosion resistant steel, ChrōmX, was introduced. Prototype pieces and small specimens are currently being cast for element testing.

The development of non-proprietary ultra-high performance concrete (UHPC) mixtures based on locally available materials is of key importance in the deployment of the UHPC technology in the United States. With the development of lower cost, non-proprietary mixtures, larger-scale applications of UHPC are possible. This paper discusses a joint endeavor to develop precast bridge elements for Florida made from a non-proprietary, locally-based UHPC mixture. The paper discusses development of the non-proprietary mixture; evaluation of the mechanical properties and workability of the locally-based UHPC; considerations related to implementing the mixture at a plant-production scale;limited structural testing of a UHPC pile; and lessons learned from the trial placements to date.

The St. Clair Road bridge over the Maple River in Clinton County, Mich., uses an innovative unbonded post-tensioning system in precast concrete adjacent box beams that eliminates the need for grouting post-tensioning ducts and for a cast-in-place concrete deck slab, resulting in accelerated bridge construction. The transverse unhonded post-tensioning tendons in both the top and bottom flanges of the beams eliminate the need for intermediate diaphragms. More important, this system enhances the overall structural performance by eliminating reflective cracks above the longitudinal joints because the joints are in permanent compression. As a result, it will likely reduce long-term costs by potentially reducing the frequency of repairs and maintenance.

Precast, prestressed concrete continuous bridges have been constructed in many countries around the world. Although these bridges have been in service for many years, there has been limited verification of the ability of the connection to provide the predicted continuity. Subsequently. many U.S. states design the girders as simple spans for both dead and live loads without considering any moments developed by the diaphragm connection. The effect of thermal expansion and contraction is hardly considered in the analysis, though it is found to have significant effects on continuity. Apart from this, there is no consensus on the best method to calculate restraint moments that develop in the continuity diaphragm or how to detail positive moment connections. The objective of this paper is to provide a simplified spreadsheet analysis for the restraint moments and the required crack control reinforcement. Detailed numerical analysis was performed using a two-span NU-girder bridge. It is recommended that the strands already in the beam be used to meet the crack control requirements with no additional mild reinforcement.

Concrete poles used in transmission structures usually are made using the spun-cast method. Recent surveys found that some spuncast concrete poles have had durability problems as a result of longitudinal cracking and concrete segregation, which have resulted in corrosion of the reinforcing/prestressing steel. An innovative static-cast concrete pole system was developed to eliminate the shortfalls of spun-cast concrete poles. These poles have a nonprismatic hexagonal hollow section, made of fiber-reinforced self-consolidated concrete (SCC), and are reinforced longitudinally using glass fiber-reinforced polymer (GFRP) bars. The static-cast operation and use of nonmetallic reinforcement make these poles corrosion free and significantly reduce their lifecycle cost. The objective of this paper is to present the design, production, testing, and implementation of the proposed static-cast concrete poles. Testing results indicate that the flexural capacity, shear capacity, and deflection of the proposed static-cast concrete poles can be predicted accurately using existing approaches. The experience of implementing this approach for two poles gives an indication of the constructability of the proposed system and its ease of handling using the same equipment and procedures adopted for conventional poles. (c) 2017 American Society of Civil Engineers.

Precast concrete parking structures have proved their cost-effectiveness, speed of construction, and architectural elegance. The dominant precast concrete joist product in the United States for parking structures is the double tee. Research over the past 40 years has focused on improving the cost-effectiveness of double tees by increasing their width from 8 to 10 to 12 ft (2.4 to 3.0 to 3.6 m). Recently a 15 ft (4.5 m) wide double tee was introduced in some U.S. regions. Another active area of research has been to make the reinforcement of the spandrel beams simpler.This paper offers a precast concrete pretopped box slab with a wide top flange. The slab has a total depth of 24 in. (610 mm), compared with the corresponding 30 in. (76 mm) double tee, and a top flange width of 8 to 16 ft (2.4 to 4.9 m). The 12 ft wide, 24 in. deep pretopped box slab is expected to replace the 12 ft wide, 30 in. deep double tee, and the 16 ft wide, 24 in. deep pretopped box slab is expected to replace the 16 ft wide, 30 in. deep double tee. This research shows that the new shape requires fewer strands than the double tee, and it theoretically and experimentally performs well. When considered in the total-precast concrete system described herein, it is expected to be competitive on both an initial and life-cycle cost basis.This paper also offers an innovative transverse posttensioning system to render the joints maintenance free and to eliminate the need for sealants, which have inspection demands and require occasional replacement. Details are given on how to get the joints precompressed while keeping the construction steps simple.

A new system for framing curved bridges using precast prestressed concrete girders is introduced. The main feature of the new system is the use of relatively short [6-12 m (20-40ft)] straight girder segments that are joined and posttensioned to form a full-length curved girder. The visual impact of the deviation of these chords from a true curve is indistinguishable by a casual observer. However, it greatly simplifies production of precast curved girders, which are currently produced in full-span piece lengths. Another feature of the new system is utilization of two of the most commonly used precast concrete girder shapes: I-girder and U-girder. The straight-line bridge girder forms and prestressing bed can be used for the proposed curved girder system, saving considerable initial capital and allowing more precasters to compete for this type of bridge. The result is a better value of the cost-effective precast concrete stringer system compared to curved steel, cast-in-place concrete, and segmental precast systems. This paper presents the components of the new system and proposed construction stages. It also presents an overview of the analytical and experimental investigations conducted to evaluate the constructability and structural performance of the proposed system. Preliminary design aids are presented to assist in determining suitable girder size for different span lengths and radii of curvature.

The National Bridge Inspection Standards require highway departments to inspect, evaluate, and determine load ratings for structures defined as bridges located on all public roads. Load rating of bridges is performed to determine the live load that structures can safely carry at a given structural condition. Bridges are rated for three types of loads, design loads, legal loads, and permit loads, which is a laborious and time-consuming task as it requires the analysis of the structure under different load cases. Several tools are currently available to assist bridge engineers to perform bridge rating in a consistent and timely manner. However, these tools support the rating of conventional bridge systems, such as slab, I-girder, box girder and truss bridges. Recently, several innovative bridge systems have been developed, such as tied-arch bridge systems used in the construction of Ravenna and Columbus bridges in the state of Nebraska, USA. The objective of this paper is to present the procedures and models developed for the load rating of tied-arch bridges. This includes developing analytical models and performing rating factor calculations in accordance to AASHTO Load and Resistance Factored Rating specifications. Three-dimensional finite element models were developed and rating calculations were performed for the primary structural components assuming various percentages of section loss and using the most common legal and permit loads in addition to AASHTO live loads. Analysis and rating were also conducted for an extreme event where one of the hangers is fully damaged.

Precast, prestressed I-girder bridges are generally designed as simple spans for the girder self-weight and deck weight and continuous spans for super-imposed dead and live loads. Because the super-imposed loads are only about one-third of the total load, structural efficiency can be further improved if continuity is achieved for the deck weight. This paper presents a threaded rod continuity system to make precast concrete girders continuous for the deck weight without resorting to posttensioning. The threaded rod continuity system can increase bridge span capacity from 10% to 15% and essentially eliminate possible cracking at the bottom fiber of the pier diaphragm. The threaded rod continuity system allows precast concrete to compete favorably with steel in long-span highway bridges. This paper covers the historical development of the threaded rod continuity system. This paper also includes design criteria, experimental tests, design procedures, system implementation, and a numerical example.