Thickness Design Procedure Research Articles

Investigation of In Situ Thermal Properties and Early-Age Pavement Behavior in the Design and Performance Evaluation of Roller Compacted Concrete Pavement in Louisiana, U.S

The proven durability and high load-carrying capacity of roller compacted concrete pavement (RCCP), combined with its simple and cost-effective construction method and high placement speed, has created a great deal of interest from many states and local transportation agencies in the U.S. Roller compacted concrete (RCC) mixture uses less cement content and less water compared with conventional concrete mixtures, which reduces the total shrinkage strain and RCC set temperature during the hardening stage, resulting in a reduction of early-age deformation and stress developments in the RCCP. Currently, research on the early-age behavior and other thermal properties of RCCP has not been well documented. Therefore, investigations of early-age behavior and thermal properties such as coefficient of thermal expansion, ultimate shrinkage, and built-in curling are needed to understand the true behaviors of RCCP under real climatic conditions. On the other hand, the currently available RCC thickness design procedures, for example, Street-Pave and Pavement Designer, are in general short of flexibility in consideration of the combined effect of wheel and environmental loading on RCCP performance. The primary objective of this work is to investigate the early-age behavior of RCCP and to evaluate the effect of thermal properties on the design and performance of RCCP constructed in Louisiana.

Development of a Fatigue Damage Model for Roller Compacted Concrete Pavement Based on In Situ Saw-Cut Beams and Accelerated Pavement Performance

As a durable, economical, and low-maintenance concrete material, roller compacted concrete (RCC) is steadily becoming the preferred choice for many pavement applications. However, the fatigue models in current pavement thickness design procedures have generally been found to over-predict the RCC pavement fatigue damage under in situ heavy truck loading. In this study, a comprehensive beam fatigue test experiment was performed using field saw-cut RCC slab samples from two full-scale accelerated pavement testing (APT) sections to investigate the fatigue behavior of in situ RCC pavements. This is the first research study to investigate the fatigue behavior of field RCC beam samples prepared and constructed with a high-density asphalt-type paver and a vibratory roller. The results indicate that a well-compacted RCC pavement can achieve higher flexural strength and exhibit better fatigue life than conventional concrete pavement. Based on the beam fatigue test results and in situ fatigue performance of APT test sections, an RCC fatigue-life model was developed, providing a more accurate solution for estimating the allowable number of load repetitions of RCC pavements subjected to vehicular fatigue loading. This model could be used in RCC thickness design procedures to determine the optimum RCC design thickness and long-term fatigue performance of RCC pavements for roadway application.

Evaluating the Effect of Concrete Slab Curling on Joint Load Transfer Responses

Past and current rigid pavement thickness design procedures used by the FAA use single-slab free-edge loading stress analysis as the basis of design. The FAA's rigid pavement design methods have assumed a 25% reduction in free-edge bending stress to account for the ability of properly designed joints to transfer load from slab to slab and reduce bending stress from heavy wheel loads. This percentage of reduction is actually changing continuously as a function of slab temperature, joint type, pavement age, and traffic. A systematic procedure is used to evaluate the joint load transfer percentage of stress reduction factor in greater detail with falling weight deflectometer (FWD) measurements, slab curvature measurements, and finite element method (FEM) structural analysis. Field measurements of joint stiffness and slab curling are presented and compared with FEM simulations calibrated to reproduce field measurements. With the use of calibrated FEM models, the full range of expected load transfer percentages is demonstrated for single-wheel loads, two-wheel gears, and four-wheel gears for a wide range of possible joint stiffness values. Top-down and bottom-up slab cracking stresses are compared. Slab curling measured from test sites is compared with slab curling calculated from FEM models. The calibration of an FEM model to reproduce detailed site measurements of joint stiffness, load transfer efficiency, and slab curvature combined is demonstrated.

TKUPAV: Stress Analysis and Thickness Design Program for Rigid Pavements

An alternative procedure for the determination of critical stresses and the thickness design of rigid pavements is presented. The effects of a finite slab size, different gear configurations, widened outer lane, tied concrete shoulder, second layer, and thermal curling are investigated. The well-known ILLI-SLAB finite-element program was used for the analysis. The program’s applicability for stress estimation is further validated by reproducing very favorable results to the test sections of Taiwan’s second northern highway, the AASHO road test, and the Arlington road test. Prediction models for stress adjustments are developed using a projection pursuit regression technique. A simplified stress analysis procedure is proposed and implemented in a user-friendly program (TKUPAV) to facilitate instant stress estimations at three critical locations of the slab; namely, the edge, corner, and interior. A modified Portland Cement Association stress analysis and thickness design procedure is also proposed and incorporated into the TKUPAV program. This program may be utilized for various structural analyses and designs of jointed concrete pavements in both the metric system and the U.S. customary system.

Performance of CAL/APT Drained and Undrained Pavements Under HVS Loading

The Heavy Vehicle Simulator (HVS) test results of the first experiment of the California Department of Transportation (Caltrans) Accelerated Pavement Testing Program, known as CAL/APT, are presented. The Goal 1 experiment was designed to validate the existing Caltrans pavement thickness design method for drained (containing an asphalt treated permeable base layer) and undrained (containing aggregate base only) flexible pavements. The pavement performance results include fatigue crack development, surface profile, and vertical deflections. The observed performance of the two types of structures is compared. The effects of construction compaction of the asphalt concrete, bonding between asphalt concrete lifts, the relative performance of the drained and undrained structures under the controlled HVS environment, and comparison of the observed performance and performance expected by the thickness design procedure are presented and discussed.

Modified Portland Cement Association Stress Analysis and Thickness Design Procedures

A new stress analysis and thickness design procedure for jointed concrete pavements was developed. On the basis of Westergaard’s edge stress solution and several prediction models for stress adjustments for a variety of loading and environmental (i.e., thermal curling) conditions, a modified Portland Cement Association (PCA) equivalent stress analysis and thickness design procedure was proposed and implemented in a highly user-friendly, Windows-based program, TKUPAV, for practical trial applications. The proposed approach has been further verified by reproducing results very close to the PCA’s equivalent stresses and fatigue damages using a spreadsheet program and the TKUPAV program. The possible detrimental effect of loading plus daytime curling has been illustrated in a case study, which also indicated that the effect of thermal curling should be considered in the thickness design of concrete pavements.

Updating Pavement Design Procedures for New York State

New York's effort in adapting concepts from AASHTO's pavement design guide as a basis for a revised state design procedure for thickness of new and reconstructed pavements is summarized. The rationale for this revised procedure was to design more durable pavements and reduce life-cycle costs. New York's past pavement design practice and the background for the revisions are briefly described. A sensitivity analysis was conducted to identify how AASHTO design variables affect pavement thickness. Past performance of selected New York pavements was also studied. The rationale is discussed for determination of appropriate design variables, based on the sensitivity analysis, performance studies, and reviews of past and current practice. Also described is the justification of other design features, such as 50-year design life, granular subgrade, permeable base, edge drains, shorter slabs, maximum and minimum pavement thicknesses, and new dowel and tie-bar designs. Development and implementation of New York's new AASHTO-based thickness design procedure are major steps toward accomplishing the goals of building longer-lasting pavements and reducing life-cycle costs.

Updating Pavement Design Procedures for New York State

New York's effort in adapting concepts from AASHTO's pavement design guide as a basis for a revised state design procedure for thickness of new and reconstructed pavements is summarized. The rationale for this revised procedure was to design more durable pavements and reduce life-cycle costs. New York's past pavement design practice and the background for the revisions are briefly described. A sensitivity analysis was conducted to identify how AASHTO design variables affect pavement thickness. Past performance of selected New York pavements was also studied. The rationale is discussed for determination of appropriate design variables, based on the sensitivity analysis, performance studies, and reviews of past and current practice. Also described is the justification of other design features, such as 50-year design life, granular subgrade, permeable base, edge drains, shorter slabs, maximum and minimum pavement thicknesses, and new dowel and tie-bar designs. Development and implementation of New York's new AASHTO-based thickness design procedure are major steps toward accomplishing the goals of building longer-lasting pavements and reducing life-cycle costs.

Asphalt Concrete Creep as Related to Rutting

Rutting is one of the major modes of distress in flexible pavements. It is caused by plastic deformation that can occur in any of pavement layers. Historically, rutting of asphalt concrete has been considered a mix design and/or construction problem. Furthermore, current methods of mix design are independent from pavement thickness design procedures. The focus of this paper is on permanent deformation of asphalt concrete layer. The primary objective is to develop a methodology for characterization of rutting potential of asphalt mixtures that can be easily implementable at state highway agencies. Permanent deformation characterization procedures are to be based upon parameters that can be integrated into mechanistic pavement design procedures. A mechanistic methodology is developed for permanent deformation characterization of asphalt paving materials. Rheological properties of hot mix asphalt (HMA) are thoroughly studied by means of a simple creep test that is originally developed by Shell researchers. Procedures are developed in order to account for nonlinear, viscoelastic, and viscoplastic deformation components of HMA. Results indicate that structural arrangement of pavement layers has a significant influence on rutting performance of the HMA layer. Findings of this study can be easily implemented in an integrated mix-thickness design procedure.

Strake camber and thickness design procedure for low alpha supersonic flow

A procedure for the design of a strake mounted on a large forebody at a typical supersonic cruise condition is described. The design goal is attached flow on the upper surface of the strake at the low lift condition. Strake camber and thickness are systematically varied until an attached-flow, surface-pressure distribution is achieved. The surface pressures are computed by a full-potential solver, NHCOREL, and an empirical guideline is used to prevent leading-edge flow separation

Thickness Design Procedure For Cement-Treated Sand Bases

An equation formerly limited to thickness requirements for soil-cement bases is shown to be applicable to cement-treated sand bases provided proper equation constants are used. These constants are related to base thickness and subgrade modulus and can be determined using the nomograph presented. The constants apply to poorly graded sand bases treated with 7% portland cement producing a minimum seven day compressive strength of 450 psi. Design criteria are presented to limit indescriminate use of the equation.

Review and Evaluation of Soil-Cement Pavements

Factors affecting properties of soil-cement; quality and thickness design procedures for soil-cement base courses are examined; field tests and airfield performance data are analyzed and compared with performance of conventional flexible pavements.

A Review and Evaluation of Soil-Cement Pavements

The factors affecting the properties of soil-cement are reviewed. Quality and thickness design procedures for soil-cement base courses are critically examined. Field test section and airfield performance data are analyzed and compared with the performance of conventional flexible pavements.