The Mantua Group

Simple Black and White Asset Management, Reliability Expertise, and Maintenance Execution Perfection.

Data Analysis

Wood Decay Engineering for Transmission Pole Assessment

Applying AS 1170.5 Draft Wood Decay Modeling to Predict Functional and Catastrophic Failure Thresholds

This white paper presents an engineering methodology for predicting wood pole deterioration using decay progression models aligned with AS 1170.5 Draft, the Australian standard. The approach integrates field-measured decay rates from test stake programs with pole geometry to establish both functional failure (FF) and catastrophic failure (CF) thresholds for transmission structures.

A critical finding is that failure timing is highly dependent on original pole diameter, not simply pole age. Analysis demonstrates that functional failure for minimum-diameter poles may occur 50 years before maximum-diameter poles of the same age and treatment cohort, fundamentally changing how asset managers should prioritize inspections and replacements.

The methodology incorporates treatment effects for both Pressure Impregnated (PI) and Natural Round (NR) timber, accounting for preservative type, retention levels, and the progression of wood decay through sapwood, outer heartwood, and inner heartwood (corewood) zones.

Regulatory Period Replacement Forecasting for Transmission Assets

Using Conditional Unreliability to Justify Capital Expenditure Forecasts

This white paper presents a mathematically rigorous methodology for forecasting transmission asset replacement volumes across regulatory periods. The approach applies conditional unreliability analysis to convert Weibull distribution parameters into defensible, period-specific replacement projections suitable for regulatory capital expenditure submissions.

Traditional forecasting methods based on historical replacement rates or simple age-based rules fail to account for the non-linear nature of asset deterioration and the evolving age profile of in-service populations. Conditional unreliability
directly addresses these limitations by answering the essential question: ‘Given that this asset has survived to its current age, what is the probability it will require replacement within the next regulatory period?’

The methodology produces both aggregate replacement volumes for capital planning and individual structure probability assessments for tactical prioritization, providing a united analytical framework that serves multiple asset management functions.