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Chen L.,Professional Service Industries Inc. | Graybeal B.A.,Turner Fairbank Highway Research Center
Journal of Bridge Engineering | Year: 2012

The concrete-damaged plasticity (CDP) model with proposed material properties replicated the observed deflection and strain responses of three experimentally tested I-girders and was determined to be consistent for different spans under both flexural and shear tests. In this study, the CDP model was further tested in modeling the behaviors of a prestressed second-generation ultrahigh-performance concrete (UHPC) pi-girder. The computational aspects include discussion of the various parameters that influenced the accuracy of the model and investigation of the scenarios regarding the limits that are useful for further optimization of the girder. The CDP model was reconfirmed to be consistent and reliable in replicating the observed structural response of both the UHPC pi-girder and a modified structural configuration referred to as the "UHPC pi-girder-with-joint. " The finite-element analysis modeling techniques developed herein are expected to be valuable in the future development of additional UHPC structural components. © 2012 American Society of Civil Engineers.

Chen L.,Professional Service Industries Inc. | Graybeal B.A.,Structural Concrete Research Program Manager
Journal of Bridge Engineering | Year: 2012

Abstract Ultrahigh performance concrete (UHPC) is an advanced cementitious composite material that has been developed in recent decades. When compared with more conventional cement-based concrete materials, UHPC tends to exhibit superior properties such as increased durability, strength, and long-term stability. This computational investigation focused on modeling the structural behaviors of UHPC components including prestressed UHPC AASHTO Type II girders. The concrete damaged plasticity model was tailored to model UHPC within a commercially available finite-element analysis package. This manuscript focuses on modeling three UHPC I-girders tested under flexural or shear loading configurations. The concrete damaged plasticity model was demonstrated to replicate both linear and nonlinear structural responses of I-girders reasonably well. A set of UHPC constitutive properties were developed that facilitate the model replication of the local and global responses observed in the series of physical tests. © 2012 American Society of Civil Engineers.

Dixon P.,Professional Service Industries Inc. | Guthrie W.,Brigham Young University | Eggett D.,Brigham Young University
Transportation Research Record | Year: 2012

Full-depth reclamation (FDR) in conjunction with cement stabilization is an established practice for the rehabilitation of flexible pavements. Conventionally, the FDR process involves applying dry cement powder with a pneumatic spreader, but this process can create undesirable fugitive cement dust. To solve this problem, cement slurry has been proposed because it can allow cement stabilization to be used in urban areas. This research sought to (a) identify construction-related factors that influence the strength of road base treated with cement slurry in conjunction with FDR and quantify the effects of those factors and (b) compare the strength of road base treated with cement slurry with that of road base treated with dry cement. Full-factorial laboratory experimentation on a road base sampled from an FDR project was conducted. The 7-day unconfined compressive strength was measured as the dependent variable. The independent variables included cement content; slurry water batching temperature; presence of a set-retarding, water-reducing admixture; cement slurry aging temperature; cement slurry aging time; cement-aggregate mixing time; and form of cement. The results suggested that the slurry water batching temperature, the haul time, the environmental temperature, and the presence of a set-retarding, water-reducing admixture would not significantly affect the strength of a cement-treated base (CTB) within the ranges of the factors investigated in this research. However, cement content and cement-aggregate mixing time were found to be positively correlated with CTB strength, regardless of the cement form. Additionally, the use of cement slurry was found to result in slightly lower strength values than the use of dry cement.

Zhang G.,Professional Service Industries Inc. | Harichandran R.S.,Michigan State University | Harichandran R.S.,University of New Haven | Ramuhalli P.,Pacific Northwest National Laboratory
NDT and E International | Year: 2012

Delamination of concrete bridge decks is a commonly observed distress in corrosive environments. In traditional acoustic inspection methods, delamination is assessed by the hollowness of the sound created by impacting the bridge deck with a hammer or bar or by dragging a chain. The signals from such sounding methods are often contaminated by ambient traffic noise and delamination detection is highly subjective. In the proposed method, a modified version of independent component analysis (ICA) is used to filter the traffic noise. To eliminate subjectivity, mel-frequency cepstral coefficients (MFCC) are used as features for delamination detection and the delamination is detected by a radial basis function (RBF) neural network. Results from both laboratory and field data suggest that the proposed method is noise robust and has satisfactory performance. The method can also detect the debonding of repair patches and concrete delamination below the repair patches. The algorithms were incorporated into an automatic impact-based delamination detection (AIDD) system for field application. © 2011 Elsevier Ltd. All rights reserved.

Zmetra K.,Professional Service Industries Inc. | Zaghi A.E.,University of Connecticut | Wille K.,University of Connecticut
Structures Congress 2015 - Proceedings of the 2015 Structures Congress | Year: 2015

The end corrosion in steel girders at the bearings due to joint leakage is a significant problem in many of the old bridges around the nation. This critical damage impairs the shear and bearing capacities of girders. This paper discusses a novel method for retrofitting the corroded ends of steel bridge girders using ultra-high performance concrete (UHPC) encasings. This repair method involves casting thin UHPC panels on each side of girder web. Shear studs welded to undamaged portion of the web and flange engage the UHPC panels and provide an alternate load path. This repair method is expected to be superior to the current practice of attaching steel cover plates. It can be easier to design and install, reduce obstruction to traffic during the repair, prevent future corrosion to the girder end, and reduce the total cost of repair. To investigate the effectiveness of the repair in recovering the capacity of the corrosion damaged girders, three large-scale experiments were performed on the undamaged, damaged and repaired rolled girders. It was found that a 1 3/4-in. thick UHPC panel cast two-third of the height of the girder effectively restores the bearing capacity. A high fidelity finite element model was created from the results of the large-scale experiments. This model was then used to design eight repair techniques for full size plate and rolled girders with heavy corrosion damage. This innovative repair method may offer the bridge design community a superior alternative retrofit method for large scale application on our aging bridges.

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