![backcalculation stiff bottom layer backcalculation stiff bottom layer](https://www.scientific.net/AMM.587-589.1062/preview.gif)
The upgrade also allows modulus limits to be applied. A facility is incorporated to find the appropriate adjustment factors so that Odemark-Bousinesq solutions will fit more closely with numerical integration methods if required.
![backcalculation stiff bottom layer backcalculation stiff bottom layer](https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/15036/images/image034.png)
The program has recently been upgraded to include the capacity for deflection basin fit, and it can also provide results based on numerical integration methods. It carries out back and forward analysis within the one program, originally using the Odemark-Boussineq transformed section approach. It allows only isotropic moduli to be considered.ĮLMOD (Evaluation of Layer Moduli and Overlay Design) is supplied by Dynatest . This was recently selected as the back-analysis program of choice by the Strategic Highway Research Progam (SHRP), and it can therefore be expected that MODULUS will gain increasing support in the United States. This greatly increases the speed over iterative numerical integration methods. MODULUS, provided by the Texas Transportation Institute, uses a deflection bowl fit to a library of bowl shapes with corresponding layer stiffnesses. It is very versatile and can include complex loading patterns. CIRCLY uses numerical integration and is one of the few programs which will accommodate materials with anisotropic moduli. Seed moduli are required for EFROMD2, and maximum/minimum credible moduli can be specified. For materials where the modulus is strongly dependent on stress level, sublayering is recommended to improve the accuracy of modelling. When an appropriate model of the existing pavement has been established, then CIRCLY is used again in the forward analysis to evaluate rehabilitation options. The program also corrects for secondary effects if the beam support points are affected by the deflection bowl. Field data from either the FWD or Instrumented Benkelman Beam may be used, and the program will apply one or two loading circles accordingly. It uses CIRCLY iteratively to provide elastic layer moduli corresponding to a given deflection bowl.
#Backcalculation stiff bottom layer software#
There are however many users of the latter form of software because of its rapid processing time.ĮFROMD2 (Elastic properties from Deflections) was developed by the Australian Road Research Board. Most of the forward analysis programs (including CIRCLY, BISAR and MODULUS) are based on multi-layer elastic theory with numerical integration or finite element analysis (FLEA), while a few (eg ELMOD ) are based on the Odemark-Bousinesq transformed section approach. Some packages eg EFROMD2 & CIRCLY are supplied as separate programs while others such as ELMOD combine both back and forward analysis into a single program. When the multi-layered elastic model is established, a forward analysis is carried out to determine strains for a modelled rehabilitation treatment such as overlay. The basic procedure comprises iterations, adjusting layer moduli until the computed deflections match the measured deflections.
![backcalculation stiff bottom layer backcalculation stiff bottom layer](https://cdnsciencepub.com/cms/10.1139/L07-083/asset/images/large/l07-083f7.jpeg)
A back-analysis procedure is therefore generally adopted to find moduli from an observed deflection bowl.
![backcalculation stiff bottom layer backcalculation stiff bottom layer](https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/16009/images/fig80.jpg)
There is now a large selection of software for determining the stresses, strains and deflections within a layered elastic system.