Technical Reports, Civil and Environmental Engineering

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Bridge Deck Service Life Prediction and Costs
Williamson, Gregory; Weyers, Richard E.; Brown, Michael C.; Sprinkel, Michael M. (Virginia Center for Transportation Innovation and Research, 2007-12-01)
The service life of Virginia's concrete bridge decks is generally controlled by chloride-induced corrosion of the reinforcing steel as a result of the application of winter maintenance deicing salts. A chloride corrosion model accounting for the variable input parameters using Monte Carlo resampling was developed. The model was validated using condition surveys from 10 Virginia bridge decks built with bare steel. The influence of changes in the construction specifications of w/c = 0.47 and 0.45 and w/cm = 0.45 and a cover depth increase from 2 to 2.75 inches was determined. Decks built under the specification of w/cm = 0.45 (using slag or fly ash) and a 2.75 inch cover depth have a maintenance free service life of greater than 100 years, regardless of the type of reinforcing steel. Galvanized, MMFX-2, and stainless steel, in order of increasing reliability of a service life of greater than 100 years, will provide a redundant corrosion protection system. Life cycle cost analyses were conducted for polymer concrete and portland cement based overlays as maintenance activities. The most economical alternative is dependent on individual structure conditions. The study developed a model and computer software that can be used to determine the time to first repair and rehabilitation of individual bridge decks taking into account the time for corrosion initiation, time from initiation to cracking, and time for corrosion damage to propagate to a state requiring repair.
Construction of a Virginia Short-Span Bridge with the Strongwell 36-Inch Double-Web I-Beam
Cousins, Thomas E.; Lesko, John J. (Virginia Center for Transportation Innovation and Research, 2005-10-01)
The Route 601 Bridge in Sugar Grove, VA, spans 39 ft over Dickey Creek. The bridge is the first to use the Strongwell 36-in-deep fiber-reinforced polymer (FRP) double-web beam (DWB) in a vehicular bridge superstructure. Construction of the new bridge was completed in October 2001, and field testing was undertaken shortly thereafter as well as in June of 2002 to assess any potential changes in structural performance. This paper details the field evaluation of the Route 601 Bridge. Using midspan deflection and strain data from the October 2001 and June 2002 field tests, AASHTO bridge design parameters were determined, namely wheel load distribution factor g, dynamic load allowance IM, and maximum deflection. The wheel load distribution factor was determined to be S/4, a dynamic load allowance was determined to be 0.50, and the maximum deflection of the bridge was L/1110. Deflection results were lower than the AASHTO L/800 limit. This discrepancy is attributed to partial composite action of the deck-to-girder connections, bearing restraint at the supports, and contribution of guardrail stiffness. It was found that diaphragm removal had a small effect on the wheel load distribution factor. An examination of the 36-in DWB capacity and failure mode indicates that the strength of the girder is controlled by compression failure in the flange and not shear failure, as originally thought. An attempt to predict the girder fatigue performance shows that small losses in bending stiffness would be expected at fatigue loads 26% of the ultimate capacity, which was confirmed through experiments. Moreover, there is no concern that fatigue alone will cause a failure during the reasonable life of the structure as presently operated.
Corrosion Protection Service Life of Epoxy-Coated Reinforcing Steel in Virginia Bridge Decks
Brown, Michael C.; Weyers, Richard E.; Megan C. Wheeler (Virginia Center for Transportation Innovation and Research, 2003-09-01)
The corrosion protection service life extension provided by epoxy-coated reinforcement (ECR) was determined by comparing ECR and bare steel bars from 10 Virginia bridge decks built between 1981 and 1995. The objective was to determine the corrosion protection service life time extension provided by ECR field specimens with various degrees of coating adhesion: disbonded, partially disbonded, and wholly bonded coatings. The size and length distributions of cracks in Virginia bridge decks were investigated to assess the frequency and severity of cracks. Correlation of cracks with chloride penetration was used to characterize the influence of cracking on deck deterioration. Cracks influence the rate of chloride penetration, but the frequency and width distributions of cracks indicate that cracks are not likely to shorten the overall service life of most bridge decks in Virginia. Altogether, 141 drilled cores, 102 mm (4 inches) in diameter, were employed in this study. For each of the decks built with ECR, 10 to 12 cores were drilled through a top reinforcing bar adjacent to the previous study core locations. In addition, approximately 3 cores were drilled through a top reinforcing bar at a surface crack location. Laboratory testing involved nondestructive monitoring using advanced electrochemical techniques to periodically assess the corrosion state of the steel bars during cyclic exposure to chloride-rich solution over 36 months of treatment. Time of corrosion initiation and time of cracking (where applicable), as well as chloride content of the concrete before and after treatment, were used in the analysis. Analysis of the epoxy coating after treatment showed the presence of micro cracks in the surface of some coatings, and moisture uptake and glass transition temperatures, as related to curing of the coatings, were investigated. Less than 25 percent of all Virginia bridge decks built under specifications in place since 1981 is projected to corrode sufficiently to require rehabilitation within 100 years, regardless of bar type. The corrosion service life extension attributable to ECR in bridge decks was found to be approximately 5 years beyond that of bare steel and, therefore, ECR is not a cost-effective method of corrosion prevention for bridge decks. Deleting the requirement for ECR in decks would save Virginia approximately $845,000 per year.
Evaluation of the Cargill Safelane Surface Overlay
Sprinkel, Michael M.; Roosevelt, Daniel S.; Flintsch, Gerardo W.; de León Izeppi, Edgar; Mokarem, David W. (Virginia Center for Transportation Innovation and Research, 2009-02-01)
A recent development in polymer concrete overlays is the Cargill SafeLane surface overlay (SafeLane overlay). The 3/8-in-thick overlay is constructed with epoxy and broadcast aggregates, as are typical multiple-layer epoxy overlays that are used to provide a skid-resistant wearing surface for bridge decks that protects the decks again intrusion by chloride ions. Reportedly, the SafeLane overlay is unique in that Cargill indicates that the limestone aggregate used in the overlay can absorb and store liquid deicing chemicals that are applied to the surface of the roadway. The purpose of this research was to compare the SafeLane overlay and the Virginia Department of Transportation (VDOT) modified EP-5 epoxy concrete overlay (hereinafter called the VDOT modified EP-5 overlay) based on an evaluation of their construction, initial condition, and effectiveness in preventing frost, ice, and snow formation on the surface of the roadway. The comparison was limited to overlays placed on four bridges on I-81 in 2004 and 2005 (two SafeLane and two VDOT modified EP-5 overlays) and on four sections of continuously reinforced concrete pavement on the Virginia Smart Road in 2006. The evaluation with respect to the initial condition of the overlays on I-81 was based on a comparison of the as-constructed properties, including aggregate properties, bond strength, permeability, skid resistance, and chloride content. The evaluation with respect to the initial condition of the overlays on the Smart Road was limited to skid resistance. The evaluation of the overlays with respect to their effectiveness in preventing frost, ice, and snow formation was based on visual observations and skid measurements of overlay surfaces under typical interstate winter conditions at the I-81 sites and under artificial snow and ice conditions at the Smart Road. In addition, the effectiveness of the overlays at the Smart Road in preventing frost, ice, and snow formation was compared with that of a bare-tined concrete surface. The evaluation indicated that the SafeLane overlay can provide a skid-resistant wearing and protective surface for bridge decks. The study was not able to determine the performance of the overlay with respect to providing a surface with less accumulation of ice and snow. Further, there has not been sufficient time to evaluate chloride penetration into the decks overlaid with SafeLane overlays in Virginia.
Investigation of Long-Term Prestress Losses in Pretensioned High Performance Concrete Girders
Cousins, Thomas E. (Virginia Center for Transportation Innovation and Research, 2005-06-01)
Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. Creep and shrinkage produce the most significant time-dependent effect on prestress losses, and research has shown that high performance and high strength concretes (HPC and HSC) exhibit less creep and shrinkage than conventional concrete. For this reason, the majority of traditional creep and shrinkage models and methods for estimating prestress losses, over-predict the prestress losses of HPC and HSC girders. Nine HPC girders, with design compressive strengths ranging from 8,000 psi to 10,000 psi, and three 8,000 psi lightweight HPC (HPLWC) girders were instrumented to determine the changes in strain and prestress losses. Several creep and shrinkage models were used to model the instrumented girders. For the HPLWC, each model over-predicted the long-term strains, and the Shams and Kahn model was the best predictor of the measured strains. For the normal weight HPC, the models under-estimated the measured strains at early ages and over-estimated the measured strains at later ages, and the B3 model was the best-predictor of the measured strains. The PCI-BDM model was the most consistent model across all of the instrumented girders. Several methods for estimating prestress losses were also investigated. The methods correlated to high strength concrete, the PCI-BDM and NCHRP 496 methods, predicted the total losses more accurately than the methods provided in the AASHTO Specifications. The newer methods over-predicted the total losses of the HPLWC girders by no more than 8 ksi, and although they under-predicted the total losses of the normal weight HPC girders, they did so by less than 5 ksi.
Parameters Governing the Corrosion Protection Efficiency of Fusion-Bonded Epoxy Coatings on Reinforcing Steel
Andrei Ramniceanu; Weyers, Richard E.; Brown, Michael C.; Sprinkel, Michael M. (Virginia Center for Transportation Innovation and Research, 2008-01-01)
The purpose of this study was to investigate various epoxy coating and exposure parameters to determine their effects on the corrosion of reinforcing steel. The parameters investigated were: chloride content at the bar depth, coated bar corroded area, corrosion product color under the coating, epoxy coating adhesion, coating color, coating damage (holidays and holes), coating thickness, TGA, DSC and EDS analysis and SEM coating cracking investigation. This study demonstrated that the ECR coating samples extracted from concrete exhibited extensive cracking compared to the new ECR samples in which the coating cracking was limited to only one sample. The coating cracking correlated with the amount of chloride at bar level, residual adhesion of the epoxy to the steel surface, and the percent moisture in the coating. The coating cracking is also related to the change in color of the epoxy and indicates that the epoxy coating degradation in concrete influences the surface condition of the coating. The DSC results showed that both the extracted epoxy coating samples as well as new samples are not fully cured during the manufacturing process. Additionally, the extracted epoxy coated samples investigated presented significant permanent adhesion loss with little or no epoxy coating residue present on the bar surface, while the EDS analysis showed that once adhesion is lost, corrosion will proceed unimpeded under the coating even in the absence of chlorides. The parameters that presented a direct correlation with the observed corrosion activity were the number of holidays and the number of damaged areas per unit length of bar. The results also show a distinct loss of quality control in the handling and possibly storage of new coated bars. The new ECR samples had significantly higher damage density than the samples extracted from concrete, while there was no change in the number of holidays and cure condition.
Thermal Response of Integral Abutment Bridges with Mechanically Stabilized Earth Walls
Arenas, Alfredo E.; Filz, George M.; Cousins, Thomas E. (Virginia Center for Transportation Innovation and Research, 2013-03-01)
The advantages of integral abutment bridges (IABs) include reduced maintenance costs and increased useful life spans. However, improved procedures are necessary to account for the impacts of cyclic thermal displacements on IAB components, including the foundation piling and the components of mechanically stabilized earth (MSE) walls that are often used around IABs. As requested by the Virginia Center for Transportation Innovation and Research and the Virginia Department of Transportation (VDOT), this research focused on IABs with foundation piling in the backfill of MSE walls that have a "U-back" configuration, which indicates that the MSE wall has three faces, one parallel to the abutment and two parallel to the bridge alignment. During this research, more than 65 three-dimensional numerical analyses were performed to investigate and quantify how different structural and geotechnical bridge components behave during thermal expansion and contraction of the bridge. In addition, a separate series of three-dimensional numerical models were developed to evaluate the usefulness of corrugated steel pipes in-filled with loose sand around the abutment piles. The results of this research quantify the influence of design parameter variations on the effects of thermal displacement on system components, and thus provide information necessary for IAB design. One of the findings is that corrugated steel pipes around abutment piles are not necessary. An estimate of the cost savings from eliminating these pipes is presented. One of the most important outputs of this research is an easy-to-use Excel spreadsheet, named IAB v3, that quantifies the impact of thermal displacement in the longitudinal direction, but also in the transverse direction when the abutment wall is at a skew angle to the bridge alignment. The spreadsheet accommodates seven different pile sizes, which can be oriented for weak or strong axis bending, with variable offset of the abutment from the MSE wall and for variable skew angles. Both steel and concrete girders are considered. The spreadsheet calculates the increments of displacements, forces, moments, and pressures on systems components due to thermal displacement of IABs. In addition, this report provides recommendations for implementing the research results in VDOT practice by proposing modifications to Chapter 17 of VDOT's Manual of the Structure and Bridge Division, Volume V, Part 2, Design Aids and Particular Details, and to Chapter 10 of Volume V, Part 11, Geotechnical Manual for Structures. The background for each recommended modification is discussed, and specific details for changes to wording and calculations in the manuals are presented.

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