High Performance Materials in Bridges

This paper describes the task of developing a fiber reinforced polymer (FRP) composite bridge deck system that can be compositely connected to steel girders. The scope of this project included development of design criteria, design and construction of a demonstration bridge in Ohio, laboratory testing and validation of the system and performing life-cycle cost analyses.

The paper analyses the influences of the amount of binder, the percentage of silica fume, the water to binder ratio, and the types of superplasticizer, cement and aggregate respectively on both autogenous and total shrinkage of high performance concrete (HPC). The measurements of shrinkage were carried out under isothermal conditions and constant humidity of environment. Water-binder ratios, the most influential parameter, varied between 0.23 and 0.52.

For fire exposed concrete structures, no design rules exist for the detailed calculation of the bond stress of reinforcement. The effect of thermal stresses on the bond stress and the confining action of the surrounding concrete is currently neglected. This paper presents an elastic-plastic bond-slip model for the simulation of the anchorage behaviour of prestressed strands in concrete structures at both ambient and fire conditions. The model allows for a detailed simulation of the slip and prestress development during fire. The bond model is applied to interface elements between prestressed strands and the concrete structure in a 2D FE model. In this model the temperature effects on material properties of concrete and steel have been considered, according to Eurocode 2. The yield contour depends on the confinement action of the encasing concrete. An arbitrary relation has been set between the slip and the steel stress at one side and an artificial radial expansion of the strand at the other side. The response of the confining concrete against radial expansion of the strand is calculated in a second 2D FE model of the concrete cross section. This cross sectional model accounts for the effect of splitting cracks and also for temperature effects. The model is checked against tests on precast prestressed hollow core slabs at ambient and fire conditions.

Fiber reinforced plastics (FRP) as a structural material instead of steel or concrete can provide many opportunities for structural engineers to propose new structural systems. Although material properties and their application to aerospace structures can be found in literature, little is available on the application of FRP to bridge and building structures. Studied herein is the bond strength of carbon fiber reinforced plastics to structural steels in order to develop the composite structure of steel and fiber reinforced plastic. It is concluded that the strong anisotropy of fiber reinforced plastics may cause local shear stress concentration, resulting in the premature debonding.

The present study employs experimentally verified nonlinear finite element modeling techniques for the study of high performance steel (HPS) I-shaped bridge girders. An evaluation as to the appropriateness of using the current American bridge specification provisions for cross-sectional compactness and adequate bracing is carried out within the context of applications involving A709 Gr. HPS483W high performance steel. Based on this research, it appears that the current AASHTO flange compactness and bracing provisions are inadequate when applied to A709 Gr. HPS483W bridge girders; intense interactions between local and global buckling, as observed during the failure of the bridge girders studied herein, may be the cause. New flange and web compactness criteria, as well as new bracing criteria, are proposed in the present paper for use in the design of A709 Gr. HPS483W bridge girders.

Fibre reinforced polymer (FRP) composites have been providing practical solutions to structural problems in the aerospace, automotive and manufacturing industries for many years, although the benefits of FRP composites have only recently been expanded to include the bridge construction industry. Research into FRP composites for bridge construction is still in the evolutionary stage and it is evident that more information is required to provide confidence for the design of FRP bridges and for the development of design standards. Research is required in the areas of long-term environmental effects on FRP; identifying the various failure modes of FRP composites; developing design methodologies and developing efficient connections to utilise the advantageous properties of FRP composite sections. This paper will investigate the issues related to shear connection in steel - concrete composite construction and will identify parallel issues in developing the best connection application to be used for FRP to exploit the full benefits of the advantages of FRP composites for the bridge construction industry.

The current investigation deals with the response of a newly developed two-span continuous double-T (DT) bridge system, internally and externally prestressed using carbon fiber reinforced polymer (CFRP) Leadline tendons. The effect of pre-tensioning and post-tensioning on the overall strain distribution was examined. The bridge was subjected to an ultimate load test after it had been subjected to 15 million cycles of two repeated loads of constant amplitudes equivalent to the service load at Midspan 1 and twice the service load at Midspan 2. It was concluded that the presence of continuous externally draped CFRP tendons (in the positive and negative moment region), CFRP grids (on both sides of the webs and in the continuous deck slab), and the adjusted (increased) level of external prestressing forces results in a ductile CFRP continuous bridge system.

This paper gives two practical methods to reduce residual deformation of structural members while providing them with adequate energy dissipation during earthquakes. One is the combined use of high strength and ordinary strength re-bars in a member. The other is graded composite strands, which consists of high strength wires and ordinary strength wires for pre-stressed concrete members. In these systems ordinary strength steel provides energy dissipation due to its inelastic response and high strength steel acts as an elastic spring to reduce residual deformation or displacement.

Composite wrapping is being used as a means of rehabilitating corrosion-damaged reinforced concrete structures. Concern has been raised about this procedure and the potential for accelerating the problem unless provisions are made for arresting the existing corrosion. Parallel field and laboratory studies have been initiated to address some of the factors that influence the effectiveness of such procedures. In particular the use of corrosion inhibitors as a pre-treatment prior to wrapping is being investigated. Other considerations are the types of fibers and polymer resins that are most appropriate, the severity of damage that can be accommodated, and peculiarities associated with different geometries. Preliminary results indicate that wrapping may help to retard the ingress of additional chlorides, but it may also trap moisture.

This paper presents the constructibility concerns of a steel-free, CFRP grid reinforced bridge deck in Rollinsford, NH. Reinforcement layout and construction issues including grid placement of the CFRP grids, chair stability, concrete consolidation and vibration are presented. In general, the use of CFRP grids provided a quick, efficient method of providing corrosion resistant concrete deck reinforcement.

In this paper the benefits of using reactive powder concrete (RPC) to carry bursting forces in prestressed bridge girders is investigated. Tests were undertaken on three RPC, 150 MPa, deep beams with the results reported. Also in this paper is a FE analysis of a 35 metre prestressed RPC bridge girder. The paper shows some of the significant potential advantages of using RPC in bridge engineering.

It has been well documented that high strength concrete (HSC) columns are subject to early spalling of the concrete cover and that this spalling leads to lower strength. It has also been shown that HSC columns have poor ductility unless high quantities of tie reinforcement are used. In this paper it is shown that the inclusion of steel fibres into the concrete mix significantly enhances the ductility of the section and lowers the demand for closely spaced ties. A design model is given for calculating the ductility of fibre reinforced HSC columns.

This paper presents the results from two research projects and one Doctoral thesis regarding the design of composite beams made of high-strength structural steel and high-strength concrete: (I) The load-bearing behaviour of headed stud shear connectors in high-strength concrete is different from that in normal-strength concrete. Thus a new design approach was developed, where the load bearing capacity of the weld collar is considered. (II) When performing a plastic cross-section design both for the high-strength steel and for the high-strength concrete reductions are required to take into account their typical stress-strain behaviour. (III) The rules in Eurocode 4 (EC 4) dealing with the minimum shear connection ratios depending on the connector's ductility, the beam's span length, the loading, the cross-section and the distribution of the connectors were modified by carrying out numerical simulations.

This contribution describes the design of a light-weight emergency bridge made of glass-fibre-reinforced-polymer and the evaluation of recent experimental investigations performed in the frame of a research project on light-weight bridges made of high performance materials. The aim of the project was to develop a single lane bridge for a span of 20.0 m and MLC 12-loads to achieve cost effectiveness by using pultruded glass-fibre profiles commonly available on the market in connection with bonded steel reinforcement for bolted joints. A testing programme was executed to provide information on the failure criteria and temperature behaviour of these bonded hybrid-connections.

Stress laminated timber bridge deck technology has been established in Australia since 1991, resulting in the construction of over 40 prototype bridges. This paper presents an overview of the R&D undertaken to implement this technology, involving laboratory testing and field application of plate decks spanning up to 9m and high capacity cellular decks spanning 12m, with the potential to span up to 30m.

This paper presents the results of the experimental studies of the prefabricated high-strength concrete (PHC) pile, which suffered brittle failure at the pile head during the 1995 Hyougoken-Nanbu earthquake. The specimens, which were representative of typical pile heads, were tested under reverse cyclic loading and a constant axial load. The conclusions of this study are: (1) when properly reinforced with longitudinal deformed bars and lateral reinforcement, PHC pile can exhibit stable hysteretic behavior and significant ductility, (2) the deformation capacity can be evaluated using the section analysis, in which the concrete confinement provided by the lateral reinforcement is incorporated.

Studied herein is the energy absorption capacity of the laminated fiber reinforced rubber newly developed as a shock absorber, compared with that of the ordinary rubbers. The collision test is carried out between two steel solid bars in order to assess the energy absorption and the impact force during the collision. Then, the numerical simulations of the test results are made by using the mass-spring systems. It is concluded that both rubbers are effective in the energy absorption during the collision; however, the laminated fiber reinforced rubber can reduce the impact force more than the ordinary rubber. It is also concluded that the energy absorption can be estimated by using the mass-spring systems, not but for the impact force during the collision.

The primary objective of this paper is to evaluate the influence of current AASHTO live-load deflection on the design of I-shaped Grade 345W (50W) and HPS 485W (70W) steel girders. Summary information pertaining to an extensive literature review as well as results of a parametric study is presented. Lastly, recommendations are presented regarding alternative serviceability limitations that more adequately control the vibration.

This paper presents results of tests on eight scaled prestressed concrete box-girder bridges with corrugated steel webs. All eight specimens were divided into two groups according to the thickness of the top and bottom slabs. In the first group, the primary experimental parameter is the effective prestress, ranging from 0.3 to 0.8 of the yield stress of prestressing strands. In the second group, the location of prestressing strands at both ends of the specimens and the thickness of end diaphragms are the two major parameters. Based on the experimental results of all eight specimens, their cyclic behavior is critically examined, including ductility factor, and failure mode,etc. It was found that the failure mode depended on the thickness of the top and bottom slabs; larger effective prestressing resulted in earlier occurrence of concrete crushing in the bottom slab close to the end diaphragm; and both the thickness of end diaphragms and the location of prestressing strands at both ends of the specimens are insignificant when the specimens failed at the mid-span due to concrete crushing.

In order to extend the fatigue life of steel bridges, compressive residual stress was induced in the as-welded condition by an additional weld on the weld toe of box welds using developed low transformation temperature welding material. The stress ratio effect due to this compressive residual stress doubled the fatigue limit.

The success of Fiber Reinforced Polymers (FRPs) in structural rehabilitation has also led to the development of new structural concepts utilizing all FRP systems or FRP/Concrete composite systems. An overview of the research and development on applications for advanced composites to bridge engineering structures in general support of civil infrastructure renewal is presented.

Wacker Drive is a major viaduct in downtown Chicago, Illinois. The existing structure is being replaced due to severe corrosion of the embedded reinforcing steel and spalling of the concrete cover. A new structure is being built using high-performance concrete (HPC). The deck is post-tensioned HPC concrete, with a latex-modified concrete (LMC) overlay placed over the deck to provide the wearing surface and further protection of the embedded steel in the HPC deck. A prototype of the structure was built and load tested to failure. This paper discusses the development of the HPC, and the importance of screening raw materials, testing of HPC mixes, and the implementation of a quality assurance program.

A study of an innovative new concept for joints between prefabricated concrete elements has been conducted. The aim has been to design a joint that is stronger than the surrounding elements, but still a very small joint that is easy and fast to perform. A special steel fiber reinforced high performance concrete is used in the joint. Several laboratory tests have been performed showing that the joint meets the demands and can be treated monolithic in design.

More than 30 percent of the 587,815 bridges in the United States are classified as deficient. The Federal Highway Administration is committed to improving mobility on the nation's highways by a significant reduction in the number of deficient bridges and a reduction in the time necessary to complete bridge projects. The United States is aggressively developing and utilizing high performance bridge materials including high performance versions of steel and concrete. The US is also experimenting with fiber-reinforced polymer composites that are advantageous where high strength, light weight and resistance to attack from road salts and chemicals are critical or where rapid installation times are paramount. The Innovative Bridge Research & Construction (IBRC) Program champions the use of innovative materials and technologies to repair, rehabilitate or replace bridges. More than 150 projects utilizing innovative materials have been funded.

In 1996, the American Iron and Steel Institute, the Office of Naval Research and the Federal Highway Administration (FHWA) introduced new High Performance Steel (HPS) grades with superior strength, weldability and toughness. Since then, HPS-70W has been used successfully on bridges across the country and is increasingly gaining popularity with bridge design professionals. As HPS-70W steel becomes a more viable alternative, designers are faced with two basic questions: When is HPS-70W steel economical? What are the advantages of its use?

All steels possess a combination of properties that determines how well a steel performs. Strength, weldability, toughness, ductility, corrosion resistance, and formability are all important to determine how well a steel performs. High-performance steel (HPS) can be defined as having an optimized balance of these properties to give maximum performance in bridge structures while remaining cost-effective.

Under certain conditions, high performance steel (HPS) bridge girder designs are controlled by design limits that are not influenced by steel strength, and, thus, the use of HPS may be uneconomical. Innovative bridge girders have been proposed to overcome these design limits. The paper focuses on I-shaped girders with corrugated webs and I-shaped girders with tubular flanges. Design criteria are proposed and limited design studies showing some advantages of these innovations are presented.

The shear transfer at construction joints for members was investigated experimentally using twenty-six direct shear type specimens in order to study the effects of high strength concrete, high strength shear friction reinforcement and interface roughness. The displacement-controlled cyclic loading was applied and shear stress transferred along the interface was separated into the contributions of concrete and dowel actions. In the dowel action, the flexural action dominates the shear-frictional reinforcement and the average tensile strain at the interface did not reach the yield strain at the peak stress. The assumption that reinforcement had yielded at the peak stress was not met in the test. In the concrete action, stress transfer depends on the concrete strength and the surface roughness and the combined effect of concrete strength and surface roughness needs to be considered in a design equation. If earthquake forces act cyclically to the interface, it is not safe to count on the experimental results based on the monotonic loading test since the shear resistance in the direction opposite to the virgin direction could become smaller. This effect is pronounced for specimens with rough interface and considered to be caused by the wearing of the interlocking mechanism.

A basic step in the reliability evaluation of slender high-strength concrete (HSC) columns is the prediction of the slender column capacity under sustained loads. In this paper, the procedures for the numerical modeling of the long-term strength of slender HSC columns under sustained loads are presented. The proposed formulation directly accounts for the concrete stress-strain diagram, creep strains and the reduced concrete compressive strength under sustained loads. Finally, results of a reliability analysis of slender reinforced concrete (RC) columns under sustained loads are discussed.

The observation of the actual performance of cantilever bridges made in HPC revealed that the deflections were smaller than expected. Experiments have been carried out (in laboratory and field) to investigate the creep and shrinkage. Predictions based on the Model Code 90 (and 78) showed that the creep of HPC was overestimated.

Considerable corrosion of reinforced concrete members accelerated the research on non-metallic materials like Fiber Reinforced Polymers (FRP) for structural applications as non-corrosive reinforcement. A comparative experimental study was carried out on prestressed concrete beams pretensioned either with CFRP or steel wires. Load-deflection responses are analyzed and pivot point of loading-unloading moduli under repeated loading is defined. Practical details are given on prestressing technique and heat curing.

The U.S. military must often deploy to other countries where bridges may have insufficient strength for their heavy tactical vehicles. Strong and lightweight Fiber Reinforced Polymer (FRP) materials have been shown to be useful for strengthening reinforced concrete bridges. However, to be useful by the military, an upgrade method must be fast and easy to use, two characteristics that are not usually associated with FRP materials. An effort is currently underway at the U.S. Army Engineer Research and Development Center (ERDC) to develop alternative rapid application methodologies for FRP materials to strengthen reinforced concrete bridges. The most promising technique to emerge has been the use of mechanical fasteners (i.e. nails) to attach FRP plates to the bottom of the beams, in place of the conventional adhesive bonding techniques. This paper provides an overview of an extensive series of flexural tests conducted on beams retrofitted with FRP plates using the mechanical fastening technique. The tests showed that strength gains close to that expected from conventionally-bonded FRP can be obtained and the failure mode is actually much more ductile than with conventional FRP upgrades. Results of several analytical parametric studies are also presented and provide insight into the effect of variations in material and geometric properties of the upgraded beams.

This paper describes results related to the strengthening of a cast-in-place concrete T-girder bridge. The 5 spans are continuous and monothically connected to the bents with movement joints at the abutment and in the center span. The strengthening was conducted through the use of externally bonded fiber reinforced composites. Results of monitoring of the health of the rehabilitated structure are presented, as are results of laboratory tests on shear strengthening schemes to be applied in an eventual rehabilitation of the girders on the same bridge.

The paper presents some new technologies for bridge rehabilitation using high performance materials. These technologies were applied with great success to repair many road bridges in Romania. The rehabilitation of the road bridges comprises of the replacing of the waterproofing, pavement and expansion joints, as well as repair of the reinforced or prestressed concrete structures. The paper also presents some examples of road bridges in Romania that were repaired with high performance concrete.

The alleviation of alkali-silica reaction (ASR) in existing concrete structures is a complex problem. This paper introduces some experimental research on this issue. Results and analysis show that ASR can be alleviated in small concrete specimens by wrapping with fiber reinforcing polymers. The higher the Young's modulus of fiber, the better the alleviating effect is. Sufficient thickness of FRP and three-dimensional wrapping should be provided. Theoretical analysis shows that waterproofing is the primary reason that FRP-wrapping suppresses ASR. Physical restraint is a secondary mechanism.

Four one-third-scale prestressed RC (PRC) interior beam-column joints were tested by the authors. The main parameters of this test were the prestressing force and the bond condition between the grout and prestressing tendons passing through a joint. Prestressing force was applied at the ends of the beams using the post-tensioning method. These beam-column joints were analyzed using a nonlinear finite element method (FEM). The analysis was carried out by considering the bond between the grout and prestressing tendons as in the tests. All specimens failed in joint shear failure both in the tests and in the FEM analysis. The FEM results show a good agreement with the test results on the maximum story shear forces and the failure mode. From the experimental and FEM results, the effects of the prestressing force and the bond condition between the grout and prestressing tendons on the joint shear capacity were examined. The following conclusions can be made from the detailed investigations: (1) The joint shear cracking strength obtained from the tests was almost constant regardless of the level of the prestressing force. However, the angles of shear cracking in the joint changed with the prestressing forces; (2) The shear capacity of the joint was not much affected by the prestressing forces; and (3) Because the bond between the grout and rounded tendons deteriorated at an early loading stage, the effect of the bond conditions on the joint shear capacity was not significant.

A structural experiment and analyses have been conducted to investigate the shear and flexural performance of reinforced beams with high performance fiber reinforced cement composite (HPFRCC). Beams with HPFRCC showed higher shear strength, ultimate flexural moment and ductility after flexural yielding than reinforced concrete beams. The estimation methods, which took into account the tensile characteristics of HPFRCC, reasonably reproduced the experimental results.

This paper evaluates the shear strength for normal and high strength concrete beams reinforced with longitudinal GFRP reinforcing bars and no web reinforcement. The effect of reinforcement ratio ρ_f is examined, and experimental data is compared with values predicted by FRP shear strength expressions found in the literature, including the new design expression recommended by ACI Committee 440.

This paper deals with the circumstances of application of high-strength concrete in the Hungarian bridge construction industry in the mirror of adopting the Eurocode series. As a historical background, first a comparison has been carried out analysing the safety level of concrete bridge structures designed according to the Hungarian codes through the 20^th century and the Eurocode. Then the main aspects and tasks of the current Hungarian concrete technology have been summarised. Finally, a proposal concerning the partial safety factor of high-strength concrete has been presented.

This paper presents the results of a study in which time-dependent strains and deflections were monitored for normal and high strength concrete beams reinforced with GFRP. Sustained load behavior was observed to be similar to that of steel reinforced beams. The effect of additional flexural cracking over time was found to be significant.

The competitiveness of orthotropic bridge decks depends on their high strength to weight ratio. However, poor durability of paving materials and fatigue failure of welds have contributed to high costs of repair including road user delay costs due to traffic disruption. It is proposed to use a layered surfacing system, combining lightweight asphalt, conventional asphalt and a layer of glass fiber mesh embedded just beneath the chip-sealed surface. Fatigue tests indicate that glass fiber reinforcement increases the durability by a factor of at least ten.