Yang X.,Louisiana Transportation Research Center |
Yang X.,University of Kansas |
Han J.,University of Kansas |
Pokharel S.K.,Access Inc. |
And 6 more authors.
Geotextiles and Geomembranes | Year: 2012
Accelerated pavement testing (APT) is an effective method in evaluating pavement performances by applying controlled wheel loading under environmental conditions. This note presents the findings from an accelerated pavement test on unpaved road sections involving geocell reinforcement of sand bases. A total of four unpaved road sections were constructed. Sections 1 and 4 were unreinforced sections first with sand bases and then replaced with aggregate bases after failure. Sections 2 and 3 were sand sections reinforced with novel polymeric alloy (NPA) geocell under an aggregate cover layer. Rut depths developed in each section were measured after a certain number of wheel passes. Horizontal strains at different locations in the NPA geocell were monitored by strain gages. Test results demonstrated that the NPA geocell had a significant effect in improving the stability of unpaved roads and reducing the permanent deformation. Under the particular test condition, the NPA geocell-reinforced sand layer behaved equivalently to the A-1-a aggregate of the same thickness. The deformations of the geocell-reinforced road sections were analyzed. The test also revealed the importance of keeping the geocell structure intact to ensure the adequate performance of NPA geocell-reinforced bases. Strain gage measurements showed that the NPA geocell beneath the wheel path experienced tensile stresses whereas the geocell outside the wheel path experienced compressive stresses. © 2011 Elsevier Ltd.
Mohammad L.N.,Louisiana State University |
Cooper S.B.,Louisiana Transportation Research Center |
Elseifi M.A.,Louisiana State University
Journal of Materials in Civil Engineering | Year: 2011
The objective of this study was to evaluate the use of crumb rubber (CR) from waste tires and engineered additives as a rejuvenator to high reclaimed asphalt pavement (RAP) content asphalt mixtures. Six asphalt mixtures were prepared by mixing aggregate blends with four asphalt binders, an unmodified asphalt binder classified as performance grade (PG) 64-22, two polymer-modified binders classified as PG 70-22M and PG 76-22M, and a PG 76-22 crumb-rubber-modified binder. The RAP content was varied from 0-40% and crumb-rubber additives were blended with the unmodified binder by using wet and dry processes. Hot-mix asphalt (HMA) mixture testing included an evaluation of rutting susceptibility, moisture resistance, and resistance to cracking using the flow number test, the loaded-wheel tracking test, the dynamic modulus test, the modified Lottman test, the dissipated creep strain energy test, and the semi-circular bending test. Results of the experimental program indicated that the addition of the CR additives rejuvenated the blended asphalt binder for the HMA mixture with high RAP content. The use of high RAP content with crumb rubber as a rejuvenator in the preparation of HMA is expected to provide adequate moisture resistance and superior rutting resistance as compared to conventional mixtures. However, because of the hardening properties of the mix prepared with high RAP content, the fracture and cracking resistance of the produced mixture was reduced compared with polymer-modified mixes. © 2011 American Society of Civil Engineers.
Nazzal M.D.,Ohio University |
Abu-Farsakh M.Y.,Louisiana Transportation Research Center |
Mohammad L.N.,Louisiana State University
International Journal of Geomechanics | Year: 2010
A finite-element model was developed using ABAQUS software package to investigate the effect of placing geosynthetic reinforcement within the base course layer on the response of a flexible pavement structure. A critical state two-surface constitutive model was first modified to represent the behavior of base course materials under the unsaturated field conditions. The modified model was then implemented into ABAQUS through a user defined subroutine, UMAT. The implemented model was validated using the results of laboratory triaxial tests. Finite-element analyses were then conducted on different unreinforced and geosynthetic reinforced flexible pavement sections. The results of this study demonstrated the ability of the modified critical state two-surface constitutive model to predict, with good accuracy, the response of the considered base course material at its optimum field conditions when subjected to cyclic as well as static loads. The results of the finite-element analyses showed that the geosynthetic reinforcement reduced the lateral strains within the base course and subgrade layers. Furthermore, the inclusion of the geosynthetic layer resulted in a significant reduction in the vertical and shear strains at the top of the subgrade layer. The improvement of the geosynthetic layer was found to be more pronounced in the development of the plastic strains rather than the resilient strains. The reinforcement benefits were enhanced as its elastic modulus increased. © 2010 ASCE.
Ji G.,Louisiana State University |
Li G.,Louisiana State University |
Li G.,Southern University and A&M College |
Alaywan W.,Louisiana Transportation Research Center
Construction and Building Materials | Year: 2013
Fiber reinforced polymer (FRP) composites, as a mature technology, have been widely used to repair/retrofit/reinforce damaged/degraded concrete structures such as steel reinforced concrete (RC) beams or columns by externally bonding FRP sheet(s) onto the surface of substrate concrete structures. However, the performance of FRP systems exposed to fire is a serious concern due to the combustibility of FRPs. The objective of this study is to understand and develop a new fire resistant technology with nanoclay reinforced intumescent coating. RC beams were prepared, damaged, and repaired by FRP with the new coating. The repaired RC beams were subjected to fire hazard again, and re-evaluated for its residual structural capacity. The effectiveness of the developed new coating for fire resistance was evaluated based on the test results. It is believed that this coating system would enhance fire resistance of the FRP, and safety and reliability of FRP repaired concrete structures. © 2013 Elsevier Ltd. All rights reserved.
Hassan M.M.,Louisiana State University |
Dylla H.,Louisiana State University |
Mohammad L.N.,Engineering Materials Characterization Research Facility |
Rupnow T.,Louisiana Transportation Research Center
Construction and Building Materials | Year: 2010
The use of titanium dioxide (TiO2) ultrafine particles as coating for concrete pavement have received considerable attention in recent years as these particles can trap and decompose organic and inorganic air pollutants by a photocatalytic process. In spite of these promising benefits, the durability and resistance to wear of TiO2 surface coating has not been evaluated. The objective of this study was to determine the abrasion and wear resistance properties of TiO2 coatings and its effect on the coating's environmental performance. To achieve this objective, an experimental program was conducted to measure and compare the environmental performance of titanium dioxide coating before and after laboratory-simulated abrasion and wearing. The environmental efficiency of the coating to remove nitrogen oxides (NOx) from the atmosphere was measured using a newly developed laboratory setup. Microscopic analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine the distribution of TiO2 particles on the surface before and after wearing. The measured rut depth using the Loaded-Wheel Tester (LWT) was minimal indicating that the use of the coating did not appear to affect the wear resistance of the surface. Wearing of the specimens with 5% TiO2 resulted in a small decrease in the coating NO removal efficiency. In contrast, the wearing of the samples with 3% TiO2 slightly improved the NO removal efficiency. Results presented in this paper support that the use of TiO2 coating as a photocatalytic compound would provide acceptable durability and wear resistance.
Yu X.B.,Case Western Reserve University |
Yu X.B.,Louisiana Transportation Research Center |
Yu X.,Case Western Reserve University
Canadian Geotechnical Journal | Year: 2011
Bridge scour is a major threat to the safety of bridges. There is a high risk of scour-induced damage due to the catastrophic nature of bridge foundation failure. The development of an innovative bridge scour monitoring system is a pressing task for the research community. Such a system needs to be fieldworthy, which is a characteristic assessed in terms of accuracy, ruggedness, and automation. Among these criteria, an automatic signal analysis algorithm is generally a prerequisite for deploying a long-term field monitoring program. This paper describes the development and validation of an algorithm for a scour monitoring system based on the principles of guided radar: time-domain reflectometry (TDR). This algorithm is based on the extension of the classic dielectric mixing model to layered systems. The performance of this algorithm is evaluated using experiments designed to simulate different field scour conditions. These include different types of sediments and the variation of river conditions (i.e., salinity of river water, air entrainment, and amount of suspended sediments). The experiment results indicate that the developed analyses algorithm is robust and accurate for scour-depth estimation under these investigated conditions.
Saber A.,Louisiana Tech University |
Alaywan W.,Louisiana Transportation Research Center
Journal of Bridge Engineering | Year: 2011
Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48°was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab. Thus, the bridge deck would provide the continuity over the support, improve the riding quality, enhance the structural redundancy, and reduce the expansion joint installation and maintenance costs. © 2011 ASCE.
Yu X.,Case Western Reserve University |
Yu X.,Louisiana Transportation Research Center
Advances in Structural Engineering | Year: 2011
Bridge scour is the number one cause of bridge failures. There are high risks associated with scour-induced damages due to their catastrophic nature. Developing real time bridge scour monitoring systems is a pressing task for the research community. Such systems need to be accurate, rugged, and field worthy. Implementing automatic signal interpretation is important to ensure the success of a long term scour monitoring instrument. This paper is part of the efforts to develop a TDR system to monitor the development of scour and sedimentation process. The focus of this paper is on an automation algorithm for TDR signal analyses. It discusses the theoretical foundation of this TDR algorithm for scour depth estimation. The influence of different types of sediments and the conditions of river (including the salinity and the effects of high air entrainment and suspended sediments) on the accuracy are assessed. The study indicates that the scour monitoring algorithm based on extending a physics-based general design equation is accurate under these different conditions. This will help implement a robust algorithm to automate the TDR bridge scour monitoring system.
Wu Z.,Louisiana Transportation Research Center |
Yang X.,Louisiana Transportation Research Center |
Zhang Z.,Louisiana Transportation Research Center
International Journal of Pavement Engineering | Year: 2013
This paper presents a recent study on using the mechanistic-empirical pavement design guide (MEPDG) design software (version 1.1) to evaluate the performance of typical Louisiana flexible pavement structures and compared it to the existing pavement performance data available in the pavement management system. The pavement performance indicators evaluated in this study include fatigue cracking, rutting and International Roughness Index (IRI). In addition to comparing the measured and predicted mean performance, the predicted pavement distresses at certain reliability design levels were also compared with the field variation of distresses extracted from a number of selected projects. The overall comparison results between the measured and predicted pavement distresses showed strong dependency on the pavement structure type considered in this study. Generally speaking, the MEPDG rutting models tended to over-predict the total rutting for Louisiana flexible pavements, whereas both fatigue cracking and IRI models in the MEPDG seemed to be adequate for most projects selected. Finally, a special optimisation approach was introduced to determine a set of preliminary local calibration factors for the MEPDG rutting models for two types of flexible pavements in Louisiana. © 2013 Copyright Taylor and Francis Group, LLC.
Agency: NSF | Branch: Standard Grant | Program: | Phase: IUSE | Award Amount: 337.31K | Year: 2015
The University of New Orleans (UNO), Louisiana State University (LSU) and the Louisiana Transportation Research Center (LTRC) are partnering on the project Field Monitoring and Measurements Education: A Model for Civil and Environmental Engineering. The goal of this project is to develop a model instructional program, using structural engineering and structural health monitoring as a test bed, that can be used to educate civil and environmental engineering (CEE) students in the fundamental principles and technology of field monitoring and measurements (FMM) and to utilize monitoring technologies and FMM data to evaluate performance and behavior, analyze problems and design CEE systems. The nations aging, and in some cases, failing infrastructure necessitates the education of future engineers to address problems related to structural health (and other critical areas). Since this project addresses a national need, two activities will be given significant attention: developing and implementing the instructional materials in a manner that maximizes their potential for adoption at other institutions; and building a community of interested and contributing scholars. The latter effort will encompass targeted proactive outreach activities at the state, regional, and national levels.
Specific objectives of the project are to: (1) improve student performance with respect to the existing learning outcomes of the civil engineering courses into which field monitoring modules will be incorporated, (2) improve student knowledge of and ability to use field monitoring measurements, (3) train faculty in the use of the curricular materials and (4) develop a community of scholars that has an interest in and will contribute to the further development of FMM instructional materials. Quality control and quality assurance of the instructional materials will be achieved through close coordination among the investigators, the advisory panel, and the external evaluator aided by the results of a formative evaluation of the prototype structural engineering FMM instructional unit and a summative evaluation of a revised unit over a two academic year cycle at both LSU and UNO. During the second year of the project, the unit will be introduced and assessed at four partner institutions (Virginia Tech, Case Western Reserve University, Tuskegee University and University of North Florida). The project collaborators at the partner institutions will also be used in an advisory capacity throughout all stages of the project. The results of this project will serve to establish an instructional model upon which other CEE sub-disciplines can build.