2013 Session: 236

• Development of Climate Zones for DARWin-ME
  Abstract: The Enhanced Integrated Climatic Model (EICM) integrated in the DARWin-ME design procedure allows users to select adjacent weather stations to generate a virtual weather station (VWS), whose data are further used to predict environmental impact on pavement performance. The DARWin-ME approach doesn't fully consider the potential spatial variations among these adjacent stations. Therefore, developing climate zones within a state may be necessary to account for the different climatic patterns and improve the accuracy of generated climate data. In this paper, using climate data from the National Climatic Data Center (NCDC), a cluster analysis technique is applied to develop climate zones for the State of Oklahoma. Consequently, climatic data from NCDC, DARWin-ME site-specific weather station, DARWin-ME interpolation approach using adjacent stations, and interpolation using stations within the same climate zone are obtained and compared. It is anticipated that the virtual weather data generated from the approach developed in this paper will provide more accurate data than those using the built-in DARWin-ME database and approach. However, due to the fact that Oklahoma is one of the most geographically flattest states in the US and the spatial variations within the states are insignificant, only minor improvements are obtained using the proposed technique in the DARWin-ME analyses. It is identified in the paper that selecting 5 to 10-year period of climate history data provided in DARWin-ME to generate climate data for a 20 to 40-year pavement design is inadequate. It is recommended that further work needs to be conducted in the states where substantial spatial variations are present.
  Authors: Li, Qiang; Wang, Kelvin C. P.; Zhang, Jun
  Authors: Li, Qiang; Wang, Kelvin C. P.; Zhang, Jun
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-4149
• Modeling and Calibration of Concrete Slab Interfacial Effects
  Abstract: For many years, concrete pavement construction, whether new or overlay, has been done with a variety of layer interfaces ranging from strongly cemented having a high degree of shear strength to completely unstabilized having only internal frictional resistance between the individual particles. In this regard, both past and present design methodologies have been limited in their capability to address the bond between the slab and the underlying layers – essentially considering either unbonded or fully bonded conditions for design purposes. However, this limitation ignores a wide range of partially bonded conditions that can exist between these two limits that may consist of a variety of combinations of different levels of friction and adhesion. For most instances of design, unbonded conditions are principally hypothetical where qualification of the amount of adhesive strength and frictional restraint that develops along the interfacial between the slab and the underlying layer is key to the characterization of slab behavior resulting for varying degrees of partial bond. This paper addresses a framework to model the effects of the concrete pavement slab/subbase interface for design purposes relative to these and other factors as they may pertain to the prediction of short and long term performance.
  Authors: Bari, Muhammad Ehsanul; Zollinger, Dan G.; Jung, Youn su
  Authors: Bari, Muhammad Ehsanul; Zollinger, Dan G.; Jung, Youn su
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-4607
• Experimental Study on Characteristics of Base Friction for Concrete Pavement Structure in China
  Abstract: The restraint between the slab and the base of a concrete pavement structure is an important factor that should be taken into consideration when designing a concrete pavement. Excessive restraint can lead to unexpected distresses due to the daily cycle of ambient thermal influence and the changing moisture conditions that are ultimately detrimental to the performance of the pavement. Reasonable evaluation of base friction contributes to configuring joint sealing, slab thickness and reinforced steel.Semi-rigid base, mostly made of cement stabilized crushed stone, has been widely used as the typical base for cement concrete pavement in China. Usually, a polythene sheet would be placed between the concrete slab and the base to make the interface condition smooth. In certain cases, geotextile and asphalt bond breaker may also be used as a friction reducer.A series of push-off tests were performed under different conditions to study the characteristics of base friction for a typical concrete pavement in China. Polythene sheet, geotextile, emulsified asphalt and asphalt bond breakers of three different thicknesses(2cm, 4cm and 6cm) were placed between concrete slabs and semi-rigid bases. Concrete slabs were also cast directly on base with no bond breaker to study the influence of these factors on the characteristics of base friction. Also investigated in this study were the potential factors that affect the behavior of concrete slab under frictional drag, including rate of movements, slab thickness and number of movement cycles.
  Authors: Li, Sili
  Authors: Li, Sili
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-2291
  Practice-Ready: Yes
• New Load Transfer Assembly for Jointed Concrete Pavements
  Abstract: Jointed concrete pavements continue to suffer from joint failure as the main distress and rehabilitation issue. The shear stress in the vicinity of dowel bars which is resulted from heavy traffic loads is the major factor that contributes to initiation of microcracks and joint faulting. A new load transfer assembly is introduced in this paper to be used in place of the conventional dowel bars. The introduced load transfer assembly was approved by the United States Patent Office as a new invention. The assembly comprises a spine and a plurality of dowel bars projecting from the spine where the spine comprises an elongated, freely rotating hinge. Finite element modeling was employed to evaluate the effect of using the new apparatus on the reduction of shear stress in concrete slabs. The finite element model was solved under various loading conditions and subgrade support. The obtained results showed that the suggested system reduces the shear stress level in the concrete by 15 to 20 percent. This amount of reduction in the shear stress can significantly reduce the shear-induced cracking near the joint. Furthermore, using the new load assembly was shown to be more effective on shear stress level than stabilizing the subgrade. The new invention has the capability of addressing curling and warping induced stresses as well as horizontal movement due to contraction and expansion. Furthermore, the new system prevents the dowel bars misalignment during new construction, as well as expediting the process of retrofitting damaged joints.
  Authors: Zeinali, Alireza; Mahboub, Kaymar C.; Southgate, Herbert F.
  Authors: Zeinali, Alireza; Mahboub, Kaymar C.; Southgate, Herbert F.
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-2638
  Practice-Ready: Yes
• Modeling of Slab-Foundation Friction in Jointed Concrete Pavements Under Nonlinear Thermal Gradient or Traffic Loads
  Abstract: The accurate modeling of the thermo-mechanical response of jointed concrete pavements is of primary importance in the design of pavement sections. From the initial development of pavement analysis software in the early 1970’s, it was recognized that the Finite Element Method was the most appropriate modeling tool due to its potential ability to capture all the pavement response features. A series of software development efforts have culminated in the production of NYSLAB, a jointed pavement analysis tool that has the capability to predict the complete thermo-mechanical response including pavement curling and the interactions that occur between the slabs and the foundation. This paper presents a series of studies developed in NYSLAB looking specifically into the slab-foundation friction generated by nonlinear thermal gradients and traffic loads. Nonlinear temperature gradients can produce slab expansion and contraction that lead to the generation of frictional tractions between slabs and foundation. The prediction of these friction tractions is complicated by the curling of the slabs that cause some portions of the slabs to lose contact with the foundation. The results presented here highlight the importance of considering these frictional tractions in the analysis of jointed concrete pavements since they have a significant impact on PCC slabs bending stresses.
  Authors: Zokaei Ashtiani, Mohammad Ali
  Authors: Zokaei Ashtiani, Mohammad Ali
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-3147
  Practice-Ready: Yes
• New Load Transfer Assembly for Jointed Concrete Pavements
  Authors: Zeinali, Alireza
  Authors: Zeinali, Alireza
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-2638
• Development of Climate Zones for DARWin-ME
  Authors: Li, Qiang
  Authors: Li, Qiang
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-4149
• Modeling of Slab-Foundation Friction in Jointed Concrete Pavements Under Nonlinear Thermal Gradient or Traffic Loads
  Authors: Zokaei Ashtiani, Mohammad Ali
  Authors: Zokaei Ashtiani, Mohammad Ali
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 236
  Paper Number: 13-3147