ELMOD 5

Elmod 5 is one component of a number of integrated software packages available from Dynatest for effective and efficient management of pavements.

ELMOD is an acronym for Evaluation of Layer Moduli and Overlay Design.

The new version has retained the well known fast and user friendly back-calculation routines and has a number of improvements on graphing and reporting, with all data now being stored in a Microsoft Access database format. Enhancements have been made to many of the functions including data editing, batch mode, overlay design and aircraft wander.

Many current methods of pavement evaluation and rehabilitation design rely almost exclusively on empirical relationships. Since empirical rules are difficult to generalise across a wide range of pavement types, loading and local environmental conditions, a primary goal for the Dynatest methodology has been to reduce the reliance on empirical approaches.

Instead, pavements can be analysed like most other civil engineering structures, i.e., through the use of calculated and allowable stresses and strains at critical points within the pavement structure, under load. The relationships between allowable stresses and strains, and pavement distress, remains essentially empirical. The calculation of existing stresses and strains within the pavement structure can be accomplished through an analytical, or mechanistic approach.

ELMOD 5.0 forms is the core module of the Dynatest suite analytical programs.

Advantages of Elmod 5:

• Reads Dynatest Edition 9.x, 10.x, 20.x, 25.x and FwdWin MDB data files.
• Utilises up to 15 geophones.
• Batch processes FWD/HWD data files.
• Provides extensive analytical and presentation graphing facilities.
• Offers a "turn-key" approach to pavement analysis.
• Performs backcalculation, calculates stresses and strains, and determines overlay requirements.
• Elmod 5 is one component of an integrated software package available from
• Dynatest for effective and efficient management of pavements

Three new modules can also be attached to ELMOD5:

• The FEM/LET/MET module
• The LCCA module and
• The PCN module (replacing the old ACN-PCN program):

The FEM/LET/MET Module

• The FEM (Finite Element Module) makes use of an axial symmetric finite element program.
• The LET (Linear Elastic Theory) option makes use of the Waterways Experiment Station's program (WESLEA), andMET is similar to the method used in ELMOD with improved adjustment factors.

The program can be used to manually change the layer moduli (or other parameters) and compare the effect on the deflections, calculated by any of the three options, compared to the measured deflections. An automatic fitting of measured and calculated basins may also be done, either on a point-by-point basis or for all points in the FWD file. With FEM all of the layers may be treated as non-linear elastic, and with MET the subgrade may be non-linear. Both the LET and MET may determine the depth to bedrock.

The program may also be used to calculate the critical stresses and strains at the layer interfaces.

The LCCA module

The main purpose of the LCCA (Life Cycle Cost Analysis) module is to select the optimum rehabilitation and maintenance solution for the section.

The main inputs are the backcalculation results from Elmod 5.0 and a user defined choice of rehabilitation solutions.

The program performs a life cycle cost analysis for each maintenance option, and arranges the solutions according to cost/benefit ratios. LCCA makes use of incremental-recursive analysis methods that are based on the approach of the new AASHTO 2002 design guide. If other performance data is available like roughness, rut depth, friction and visual surveys, these can also be included in the modelling.

The performance models and cost models are user adjustable and may be calibrated to specific conditions.

The PCN module

PCN is a optional module to Elmod that uses the data files from Dynatest FWD/HWD equipment to calculate ACN/PCN values based on the methods used by ICAO.

The programme includes a database of over one hundred and twenty-five aircraft with ICAO ACN values.