Use of Nondestructive Testing in Rehabilitation of Wood Cooling Towersby Andrew H. Stewart, Engineering Data Management Inc, Fort Collins, CO, USA,
Timothy L. Brunette, Engineering Data Management Inc, Fort Collins, CO, USA,
James R. Goodman, Engineering Data Management Inc, Fort Collins, CO, USA,
Abstract: State-of-the-art nondestructive evaluation (NDE) techniques, destructive testing, structural analysis, degradation rate models and statistical analysis are combined to optimize a major cooling tower rehabilitation effort. Data from an innovative in-situ NDE technique are correlated with the results of 74 axial compression tests on 4 ft (1. 2 m) long 4 multiplied by 4 redwood columns removed from 11 years of service in the severe cooling tower environment. Strength and stiffness data on new and on the 11 year old redwood material are used to develop degradation rate curves. These curves are used to predict expected future degradation. Structural analysis results for cooling tower loads are coupled with destructive and nondestructive test data, degradation rate predictions, factors for load duration and temperature effects to evaluate present and future reliability levels. Methods used in establishing minimum NDE predicted strength levels to provide the desired future strength and reliability levels for the rehabilitated cooling towers are discussed. Results of NDE data for approximately 7700 in-situ 4 ft (1. 2 m) long 4 multiplied by 4 redwood columns are reported. Using these data and the correlation established for the 74 test specimens, individual column strengths are predicted.
Subject Headings: Structural analysis | Cooling towers | Chemical degradation | Columns | Structural reliability | Nondestructive tests | Rehabilitation
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